Cooling of hot bubbles by surface texture during the boiling crisis

NASA Astrophysics Data System (ADS)

Dhillon, Navdeep; Buongiorno, Jacopo; Varanasi, Kripa

2015-11-01

We report the existence of maxima in critical heat flux (CHF) enhancement for pool boiling on textured hydrophilic surfaces and reveal the interaction mechanism between bubbles and surface texture that governs the boiling crisis phenomenon. Boiling is a process of fundamental importance in many engineering and industrial applications but the maximum heat flux that can be absorbed by the boiling liquid (or CHF) is limited by the boiling crisis. Enhancing the CHF of industrial boilers by surface texturing can lead to substantial energy savings and reduction in greenhouse gas emissions on a global scale. However, the fundamental mechanisms behind this enhancement are not well understood, with some previous studies indicating that CHF should increase monotonically with increasing texture density. However, using pool boiling experiments on a parametrically designed set of plain and nano-textured micropillar surfaces, we show that there is an optimum intermediate texture density that maximizes CHF and further that the length scale of this texture is of fundamental significance. Using imbibition experiments and high-speed optical and infrared imaging, we reveal the fundamental mechanisms governing the CHF enhancement maxima in boiling crisis. We acknowledge funding from the Chevron corporation.

Enhancement of critical heat flux in nucleate boiling of nanofluids: a state-of-art review

PubMed Central

2011-01-01

Nanofluids (suspensions of nanometer-sized particles in base fluids) have recently been shown to have nucleate boiling critical heat flux (CHF) far superior to that of the pure base fluid. Over the past decade, numerous experimental and analytical studies on the nucleate boiling CHF of nanofluids have been conducted. The purpose of this article is to provide an exhaustive review of these studies. The characteristics of CHF enhancement in nanofluids are systemically presented according to the effects of the primary boiling parameters. Research efforts to identify the effects of nanoparticles underlying irregular enhancement phenomena of CHF in nanofluids are then presented. Also, attempts to explain the physical mechanism based on available CHF theories are described. Finally, future research needs are identified. PMID:21711949

On the look-up tables for the critical heat flux in tubes (history and problems)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kirillov, P.L.; Smogalev, I.P.

1995-09-01

The complication of critical heat flux (CHF) problem for boiling in channels is caused by the large number of variable factors and the variety of two-phase flows. The existence of several hundreds of correlations for the prediction of CHF demonstrates the unsatisfactory state of this problem. The phenomenological CHF models can provide only the qualitative predictions of CHF primarily in annular-dispersed flow. The CHF look-up tables covered the results of numerous experiments received more recognition in the last 15 years. These tables are based on the statistical averaging of CHF values for each range of pressure, mass flux and quality.more » The CHF values for regions, where no experimental data is available, are obtained by extrapolation. The correction of these tables to account for the diameter effect is a complicated problem. There are ranges of conditions where the simple correlations cannot produce the reliable results. Therefore, diameter effect on CHF needs additional study. The modification of look-up table data for CHF in tubes to predict CHF in rod bundles must include a method which to take into account the nonuniformity of quality in a rod bundle cross section.« less

Combining liquid inertia with pressure recovery from bubble expansion for enhanced flow boiling

NASA Astrophysics Data System (ADS)

Kalani, A.; Kandlikar, S. G.

2015-11-01

In this paper, we demonstrate using liquid inertia force in a taper gap microchannel geometry to provide a high level of heat dissipation capacity accompanied by a high heat transfer coefficient and low pressure drop during flow boiling. The high mass flux increases liquid inertia force and promotes vapor removal from the manifold, thereby increasing critical heat flux (CHF) and heat transfer coefficient. The tapered gap above the microchannels provides an increasing cross-sectional area in the flow direction. This gap allows bubbles to emerge from microchannels and expand within the gap along the flow direction. The bubble evaporation and expansion in tapered gap causes pressure recovery and reduces the total pressure drop. The pressure recovery increases with the increased evaporation rate at higher heat fluxes. Using a 6% taper and a moderately high inlet liquid flow Reynolds number of 1095, we have reached a CHF of 1.07 kW/cm2 with a heat transfer coefficient of 295 kW/m2 °C and a pressure drop of 30 kPa.

Pool boiling characteristics and critical heat flux mechanisms of microporous surfaces and enhancement through structural modification

NASA Astrophysics Data System (ADS)

Ha, Minseok; Graham, Samuel

2017-08-01

Experimental studies have shown that microporous surfaces induce one of the highest enhancements in critical heat flux (CHF) during pool boiling. However, microporous surfaces may also induce a very large surface superheat (>100 °C) which is not desirable for applications such as microelectronics cooling. While the understanding of the CHF mechanism is the key to enhancing boiling heat transfer, a comprehensive understanding is not yet available. So far, three different theories for the CHF of microporous surfaces have been suggested: viscous-capillary model, hydrodynamic instability model, and dryout of the porous coatings. In general, all three theories account for some aspects of boiling phenomena. In this study, the theories are examined through their correlations with experimental data on microporous surfaces during pool boiling using deionized (DI) water. It was found that the modulation of the vapor-jet through the pore network enables a higher CHF than that of a flat surface based on the hydrodynamic instability theory. In addition, it was found that as the heat flux increases, a vapor layer grows in the porous coatings described by a simple thermal resistance model which is responsible for the large surface superheat. Once the vapor layer grows to fill the microporous structure, transition to film boiling occurs and CHF is reached. By disrupting the formation of this vapor layer through the fabrication of channels to allow vapor escape, an enhancement in the CHF and heat transfer coefficient was observed, allowing CHF greater than 3500 kW/m2 at a superheat less than 50 °C.

Microscale Heat Transfer Enhancement using Spinodal Decomposition of Binary Liquid Mixtures: A Collaborative Modeling/Experimental Approach

DTIC Science & Technology

2013-09-01

heat transfer coefficients due to the high heat of vapor- ization. Many authors ([ Mudawar (2001)], [ Mudawar and Bowers (1999)] and [Kandlikar (2005...Letters, 95, (2005), 1. [Rosales and Meneveau (2006)] C. Rosales and C. Meneveau. Physics of Fluids, 18, (2006), 075104. [ Mudawar and Bowers (1999)] I... Mudawar and M.B. Bowers, Ultra-high crit- ical heat flux (CHF) for subcooled water flow boiling-I: CHF data and parametric effects for small

A Novel Role of Three Dimensional Graphene Foam to Prevent Heater Failure during Boiling

PubMed Central

Ahn, Ho Seon; Kim, Ji Min; Park, Chibeom; Jang, Ji-Wook; Lee, Jae Sung; Kim, Hyungdae; Kaviany, Massoud; Kim, Moo Hwan

2013-01-01

We report a novel boiling heat transfer (NBHT) in reduced graphene oxide (RGO) suspended in water (RGO colloid) near critical heat flux (CHF), which is traditionally the dangerous limitation of nucleate boiling heat transfer because of heater failure. When the heat flux reaches the maximum value (CHF) in RGO colloid pool boiling, the wall temperature increases gradually and slowly with an almost constant heat flux, contrary to the rapid wall temperature increase found during water pool boiling. The gained time by NBHT would provide the safer margin of the heat transfer and the amazing impact on the thermal system as the first report of graphene application. In addition, the CHF and boiling heat transfer performance also increase. This novel boiling phenomenon can effectively prevent heater failure because of the role played by the self-assembled three-dimensional foam-like graphene network (SFG). PMID:23743619

Criticality in the slowed-down boiling crisis at zero gravity.

PubMed

Charignon, T; Lloveras, P; Chatain, D; Truskinovsky, L; Vives, E; Beysens, D; Nikolayev, V S

2015-05-01

Boiling crisis is a transition between nucleate and film boiling. It occurs at a threshold value of the heat flux from the heater called CHF (critical heat flux). Usually, boiling crisis studies are hindered by the high CHF and short transition duration (below 1 ms). Here we report on experiments in hydrogen near its liquid-vapor critical point, in which the CHF is low and the dynamics slow enough to be resolved. As under such conditions the surface tension is very small, the experiments are carried out in the reduced gravity to preserve the conventional bubble geometry. Weightlessness is created artificially in two-phase hydrogen by compensating gravity with magnetic forces. We were able to reveal the fractal structure of the contour of the percolating cluster of the dry areas at the heater that precedes the boiling crisis. We provide a direct statistical analysis of dry spot areas that confirms the boiling crisis at zero gravity as a scale-free phenomenon. It was observed that, in agreement with theoretical predictions, saturated boiling CHF tends to zero (within the precision of our thermal control system) in zero gravity, which suggests that the boiling crisis may be observed at any heat flux provided the experiment lasts long enough.

Transient boiling in two-phase helium natural circulation loops

NASA Astrophysics Data System (ADS)

Furci, H.; Baudouy, B.; Four, A.; Meuris, C.

2014-01-01

Two-phase helium natural circulation loops are used for cooling large superconducting magnets, as CMS for LHC. During normal operation or in the case of incidents, transients are exerted on the cooling system. Here a cooling system of this type is studied experimentally. Sudden power changes are operated on a vertical-heated-section natural convection loop, simulating a fast increase of heat deposition on magnet cooling pipes. Mass flow rate, heated section wall temperature and pressure drop variations are measured as a function of time, to assess the time behavior concerning the boiling regime according to the values of power injected on the heated section. The boiling curves and critical heat flux (CHF) values have been obtained in steady state. Temperature evolution has been observed in order to explore the operating ranges where heat transfer is deteriorated. Premature film boiling has been observed during transients on the heated section in some power ranges, even at appreciably lower values than the CHF. A way of attenuating these undesired temperature excursions has been identified through the application of high enough initial heating power.

Development of Flow Boiling and Condensation Experiment on the International Space Station- Normal and Low Gravity Flow Boiling Experiment Development and Test Results

NASA Technical Reports Server (NTRS)

Nahra, Henry K.; Hall, Nancy R.; Hasan, Mohammad M.; Wagner, James D.; May, Rochelle L.; Mackey, Jeffrey R.; Kolacz, John S.; Butcher, Robert L.; Frankenfield, Bruce J.; Mudawar, Issam;

Effects of orientation and downward-facing convex curvature on pool-boiling critical heat flux

NASA Astrophysics Data System (ADS)

Howard, Alicia Ann Harris

Photographic studies of near-saturated pool boiling on both inclined flat surfaces and a downward-facing convex surface were conducted in order to determine the physical mechanisms that trigger critical heat flux (CHF). Based on the vapor behavior observed just prior to CHF, it is shown for the flat surfaces that the surface orientations can be divided into three regions: upward-facing (0-60°), near-vertical (60-165°), and downward-facing (165-180°) each region is associated with a unique CHIP trigger mechanism. In the upward-facing region, the buoyancy forces remove the vapor vertically off the heater surface. The near- vertical region is characterized by a wavy liquid-vapor interface which sweeps along the heater surface. In the downward-facing region, the vapor repeatedly stratifies on the heater surface, greatly decreasing CHF. The vapor behavior along the convex surface is cyclic in nature and similar to the nucleation/coalescence/stratification/release procedure observed for flat surfaces in the downward-facing region. The vapor stratification occurred at the bottom (downward-facing) heaters on the convex surface. CHF is always triggered on these downward-facing heaters and then propagates up the convex surface, and the orientations of these heaters are comparable with the orientation range of the flat surface downward-facing region. The vast differences between the observed vapor behavior within the three regions and on the convex surface indicate that a single overall pool boiling CHF model cannot possibly account for all the observed effects. Upward-facing surfaces have been examined and modeled extensively by many investigators and a few investigators have addressed downward-facing surfaces, so this investigation focuses on modeling the near-vertical region. The near-vertical CHF model incorporates classical two-dimensional interfacial instability theory, a separated flow model, an energy balance, and a criterion for separation of the wavy interface from the surface at CHF. The model was tested for different fluids and shows good agreement with CHF data. Additionally, the instability theory incorporated into this model accurately predicts the angle of transition between the near-vertical and downward-facing regions.

Critical heat flux maxima during boiling crisis on textured surfaces

PubMed Central

Dhillon, Navdeep Singh; Buongiorno, Jacopo; Varanasi, Kripa K.

2015-01-01

Enhancing the critical heat flux (CHF) of industrial boilers by surface texturing can lead to substantial energy savings and global reduction in greenhouse gas emissions, but fundamentally this phenomenon is not well understood. Prior studies on boiling crisis indicate that CHF monotonically increases with increasing texture density. Here we report on the existence of maxima in CHF enhancement at intermediate texture density using measurements on parametrically designed plain and nano-textured micropillar surfaces. Using high-speed optical and infrared imaging, we study the dynamics of dry spot heating and rewetting phenomena and reveal that the dry spot heating timescale is of the same order as that of the gravity and liquid imbibition-induced dry spot rewetting timescale. Based on these insights, we develop a coupled thermal-hydraulic model that relates CHF enhancement to rewetting of a hot dry spot on the boiling surface, thereby revealing the mechanism governing the hitherto unknown CHF enhancement maxima. PMID:26346098

Enhanced flow boiling in microchannels through integrating multiple micro-nozzles and reentry microcavities

NASA Astrophysics Data System (ADS)

Li, Wenming; Qu, Xiaopeng; Alam, Tamanna; Yang, Fanghao; Chang, Wei; Khan, Jamil; Li, Chen

2017-01-01

In a microchannel system, a higher mass velocity can lead to enhanced flow boiling performances, but at a cost of two-phase pressure drop. It is highly desirable to achieve a high heat transfer rate and critical heat flux (CHF) exceeding 1 kW/cm2 without elevating the pressure drop, particularly, at a reduced mass velocity. In this study, we developed a microchannel configuration that enables more efficient utilization of the coolant through integrating multiple microscale nozzles connected to auxiliary channels as well as microscale reentry cavities on sidewalls of main microchannels. We achieved a CHF of 1016 W/cm2 with a 50% less mass velocity, i.e., 680 kg/m2s, compared to the two-nozzle configuration developed in our previous studies. Two primary enhancement mechanisms are: (a) the enhanced global liquid supply by four evenly distributed micronozzles, particularly near the outlet region and (b) the effective management of local dryout by the capillary flow-induced sustainable thin liquid film resulting from an array of microscale cavities. A significantly improved heat transfer coefficient of 131 kW/m2 K at a mass velocity of 680 kg/m2s is attributed to the enhanced nucleate boiling, the established capillary/thin film evaporation, and the induced advection from the present microchannel configuration. All these significant enhancements have been achieved with a ˜55% lower two-phase pressure drop.

Enhanced heat transfer is dependent on thickness of graphene films: the heat dissipation during boiling

PubMed Central

Ahn, Ho Seon; Kim, Jin Man; Kim, TaeJoo; Park, Su Cheong; Kim, Ji Min; Park, Youngjae; Yu, Dong In; Hwang, Kyoung Won; Jo, HangJin; Park, Hyun Sun; Kim, Hyungdae; Kim, Moo Hwan

2014-01-01

Boiling heat transfer (BHT) is a particularly efficient heat transport method because of the latent heat associated with the process. However, the efficiency of BHT decreases significantly with increasing wall temperature when the critical heat flux (CHF) is reached. Graphene has received much recent research attention for applications in thermal engineering due to its large thermal conductivity. In this study, graphene films of various thicknesses were deposited on a heated surface, and enhancements of BHT and CHF were investigated via pool-boiling experiments. In contrast to the well-known surface effects, including improved wettability and liquid spreading due to micron- and nanometer-scale structures, nanometer-scale folded edges of graphene films provided a clue of BHT improvement and only the thermal conductivity of the graphene layer could explain the dependence of the CHF on the thickness. The large thermal conductivity of the graphene films inhibited the formation of hot spots, thereby increasing the CHF. Finally, the provided empirical model could be suitable for prediction of CHF. PMID:25182076

Boiling on Microconfigured Composite Surfaces Enhanced

NASA Technical Reports Server (NTRS)

Chao, David F.

2000-01-01

Boiling heat transfer is one of the key technologies for the two-phase active thermal-control system used on space platforms, as well as for the dynamic power systems aboard the International Space Station. Because it is an effective heat transfer mode, boiling is integral to many space applications, such as heat exchangers and other cooling devices. Nucleate boiling near the critical heat flux (CHF) can transport very large thermal loads with a much smaller device and much lower pumping power than for single-phase heat exchangers. However, boiling performance sharply deteriorates in a reduced-gravity environment, and operation in the CHF regime is somewhat perilous because of the risk of burnout to the device surface. New materials called microconfigured metal-graphite composites can enhance boiling. The photomicrograph shows the microconfiguration (x3000) of the copper-graphite (Cu-Gr) surface as viewed by scanning electronic microscope. The graphite fiber tips appear as plateaus with rugged surfaces embedded in the copper matrix. It has been experimentally demonstrated that this type of material manifests excellent boiling heat transfer performance characteristics and an increased CHF. Nonisothermal surfaces were less sensitive to variations of wall superheat in the CHF regime. Because of the great difference in conductivity between the copper base and the graphite fiber, the composite surfaces have a nonisothermal surface characteristic and, therefore, will have a much larger "safe" operating region in the CHF regime. In addition, the thermocapillary forces induced by the temperature differences between the fiber tips and the metal matrix play an important role in bubble detachment, and may not be adversely affected in a reduced-gravity environment. All these factors indicate that microconfigured composites may improve the reliability and economy (dominant factors in all space applications) of various thermal components found on spacecraft during future missions.

Influence of the wetting state of a heated surface on heat transfer and pressure loss in an evaporator tube

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koehler, W; Hein, D

1986-09-01

The influence of the wetting state of a heated surface on heat transfer and pressure loss in an evaporator tube was investigated for a parameter range occurring in fossil-fired steam generators. Included in the analysis are quantities which determine the wetting state in steady and transient flow. The experimental work consists of the following: Occurrence of critical heat flux (CHF) and post-CHF heat transfer in a vertical upflow evaporator tube; influence of pressure and enthalpy transients on heat transfer in the unwetted region; influence of pipe orientation on heat transfer; and two phase flow pressure loss in wetted and unwettedmore » region. Based on these experiments a method of predicting CHF for a vertical upflow evaporator tube was developed. The heat transfer in the unwetted region was newly formulated taking into account thermal nonequilibrium between the water and steam phases. Wall temperature excursions during pressure and enthalpy transients are interpreted with the help of the boiling curve and the Leidenfrost phenomenon. A method is developed by means of which it is possible to determine the influence of the pipe orientation on the location of the boiling crisis as well as on the heat transfer in the unwetted region. The influence of the wetting state of the heated surface on the two phase flow pressure loss is interpreted as ''Wall effect'' and is calculated using a simplified computer model. 68 refs., 83 figs.« less

Critical heat flux phenomena depending on pre-pressurization in transient heat input

NASA Astrophysics Data System (ADS)

Park, Jongdoc; Fukuda, Katsuya; Liu, Qiusheng

2017-07-01

The critical heat flux (CHF) levels that occurred due to exponential heat inputs for varying periods to a 1.0-mm diameter horizontal cylinder immersed in various liquids were measured to develop an extended database on the effect of various pressures and subcoolings by photographic study. Two main mechanisms of CHF were found. One mechanism is due to the time lag of the hydrodynamic instability (HI) which starts at steady-state CHF upon fully developed nucleate boiling, and the other mechanism is due to the explosive process of heterogeneous spontaneous nucleation (HSN) which occurs at a certain HSN superheat in originally flooded cavities on the cylinder surface. The incipience of boiling processes was completely different depending on pre-pressurization. Also, the dependence of pre-pressure in transient CHFs changed due to the wettability of boiling liquids. The objective of this work is to clarify the transient CHF phenomena due to HI or HSN by photographic.

CHF Enhancement by Vessel Coating for External Reactor Vessel Cooling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fan-Bill Cheung; Joy L. Rempe

2004-06-01

In-vessel retention (IVR) is a key severe accident management (SAM) strategy that has been adopted by some operating nuclear power plants and advanced light water reactors (ALWRs). One viable means for IVR is the method of external reactor vessel cooling (ERVC) by flooding of the reactor cavity during a severe accident. As part of a joint Korean – United States International Nuclear Energy Research Initiative (K-INERI), an experimental study has been conducted to investigate the viability of using an appropriate vessel coating to enhance the critical heat flux (CHF) limits during ERVC. Toward this end, transient quenching and steady-state boilingmore » experiments were performed in the SBLB (Subscale Boundary Layer Boiling) facility at Penn State using test vessels with micro-porous aluminum coatings. Local boiling curves and CHF limits were obtained in these experiments. When compared to the corresponding data without coatings, substantial enhancement in the local CHF limits for the case with surface coatings was observed. Results of the steady state boiling experiments showed that micro-porous aluminum coatings were very durable. Even after many cycles of steady state boiling, the vessel coatings remained rather intact, with no apparent changes in color or structure. Moreover, the heat transfer performance of the coatings was found to be highly desirable with an appreciable CHF enhancement in all locations on the vessel outer surface but with very little effect of aging.« less

Electrically Driven Liquid Film Boiling Experiment

NASA Technical Reports Server (NTRS)

Didion, Jeffrey R.

2016-01-01

This presentation presents the science background and ground based results that form the basis of the Electrically Driven Liquid Film Boiling Experiment. This is an ISS experiment that is manifested for 2021. Objective: Characterize the effects of gravity on the interaction of electric and flow fields in the presence of phase change specifically pertaining to: a) The effects of microgravity on the electrically generated two-phase flow. b) The effects of microgravity on electrically driven liquid film boiling (includes extreme heat fluxes). Electro-wetting of the boiling section will repel the bubbles away from the heated surface in microgravity environment. Relevance/Impact: Provides phenomenological foundation for the development of electric field based two-phase thermal management systems leveraging EHD, permitting optimization of heat transfer surface area to volume ratios as well as achievement of high heat transfer coefficients thus resulting in system mass and volume savings. EHD replaces buoyancy or flow driven bubble removal from heated surface. Development Approach: Conduct preliminary experiments in low gravity and ground-based facilities to refine technique and obtain preliminary data for model development. ISS environment required to characterize electro-wetting effect on nucleate boiling and CHF in the absence of gravity. Will operate in the FIR - designed for autonomous operation.

Infrared thermometry study of nanofluid pool boiling phenomena

PubMed Central

2011-01-01

Infrared thermometry was used to obtain first-of-a-kind, time- and space-resolved data for pool boiling phenomena in water-based nanofluids with diamond and silica nanoparticles at low concentration (<0.1 vol.%). In addition to macroscopic parameters like the average heat transfer coefficient and critical heat flux [CHF] value, more fundamental parameters such as the bubble departure diameter and frequency, growth and wait times, and nucleation site density [NSD] were directly measured for a thin, resistively heated, indium-tin-oxide surface deposited onto a sapphire substrate. Consistent with other nanofluid studies, the nanoparticles caused deterioration in the nucleate boiling heat transfer (by as much as 50%) and an increase in the CHF (by as much as 100%). The bubble departure frequency and NSD were found to be lower in nanofluids compared with water for the same wall superheat. Furthermore, it was found that a porous layer of nanoparticles built up on the heater surface during nucleate boiling, which improved surface wettability compared with the water-boiled surfaces. Using the prevalent nucleate boiling models, it was possible to correlate this improved surface wettability to the experimentally observed reductions in the bubble departure frequency, NSD, and ultimately to the deterioration in the nucleate boiling heat transfer and the CHF enhancement. PMID:21711754

Nucleate boiling performance on nano/microstructures with different wetting surfaces

PubMed Central

2012-01-01

A study of nucleate boiling phenomena on nano/microstructures is a very basic and useful study with a view to the potential application of modified surfaces as heating surfaces in a number of fields. We present a detailed study of boiling experiments on fabricated nano/microstructured surfaces used as heating surfaces under atmospheric conditions, employing identical nanostructures with two different wettabilities (silicon-oxidized and Teflon-coated). Consequently, enhancements of both boiling heat transfer (BHT) and critical heat flux (CHF) are demonstrated in the nano/microstructures, independent of their wettability. However, the increment of BHT and CHF on each of the different wetting surfaces depended on the wetting characteristics of heating surfaces. The effect of water penetration in the surface structures by capillary phenomena is suggested as a plausible mechanism for the enhanced CHF on the nano/microstructures regardless of the wettability of the surfaces in atmospheric condition. This is supported by comparing bubble shapes generated in actual boiling experiments and dynamic contact angles under atmospheric conditions on Teflon-coated nano/microstructured surfaces. PMID:22559173

The behavior of vapor bubbles during boiling enhanced with acoustics and open microchannels

NASA Astrophysics Data System (ADS)

Boziuk, Thomas; Smith, Marc K.; Glezer, Ari

2012-11-01

Boiling heat transfer on a submerged heated surface is enhanced by combining a grid of surface micromachined open channels and ultrasonic acoustic actuation to control the formation and evolution of vapor bubbles and to inhibit the instability that leads to film boiling at the critical heat flux (CHF). The microchannels provide nucleation sites for vapor bubble formation and enable the entrainment of bulk subcooled fluid to these sites for sustained evaporation. Acoustic actuation excites interfacial oscillations of the detached bubbles and leads to accelerated condensation in the bulk fluid, thereby limiting the formation of vapor columns that precede the CHF instability. The combined effects of microchannels and acoustic actuation are investigated experimentally with emphasis on bubble nucleation, growth, detachment, and condensation. It is shown that this hybrid approach leads to a significant increase in the critical heat flux, a reduction of the vapor mass above the surface, and the breakup of low-frequency vapor slug formation. A large-scale model of the microchannel grid reveals details of the flow near the nucleation site and shows that the presence of the microchannels decreases the surface superheat at a given heat flux. Supported by ONR.

Critical heat flux (CHF) phenomenon on a downward facing curved surface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheung, F.B.; Haddad, K.H.; Liu, Y.C.

1997-06-01

This report describes a theoretical and experimental study of the boundary layer boiling and critical heat flux phenomena on a downward facing curved heating surface, including both hemispherical and toroidal surfaces. A subscale boundary layer boiling (SBLB) test facility was developed to measure the spatial variation of the critical heat flux and observe the underlying mechanisms. Transient quenching and steady-state boiling experiments were performed in the SBLB facility under both saturated and subcooled conditions to obtain a complete database on the critical heat flux. To complement the experimental effort, an advanced hydrodynamic CHF model was developed from the conservation lawsmore » along with sound physical arguments. The model provides a clear physical explanation for the spatial variation of the CHF observed in the SBLB experiments and for the weak dependence of the CHF data on the physical size of the vessel. Based upon the CHF model, a scaling law was established for estimating the local critical heat flux on the outer surface of a heated hemispherical vessel that is fully submerged in water. The scaling law, which compares favorably with all the available local CHF data obtained for various vessel sizes, can be used to predict the local CHF limits on large commercial-size vessels. This technical information represents one of the essential elements that is needed in assessing the efficacy of external cooling of core melt by cavity flooding as a severe accident management strategy. 83 figs., 3 tabs.« less

Bubble induced flow field modulation for pool boiling enhancement over a tubular surface

NASA Astrophysics Data System (ADS)

Raghupathi, P. A.; Joshi, I. M.; Jaikumar, A.; Emery, T. S.; Kandlikar, S. G.

2017-06-01

We demonstrate the efficacy of using a strategically placed enhancement feature to modify the trajectory of bubbles nucleating on a horizontal tubular surface to increase both the critical heat flux (CHF) and the heat transfer coefficient (HTC). The CHF on a plain tube is shown to be triggered by a local dryout at the bottom of the tube due to vapor agglomeration. To mitigate this effect and delay CHF, the nucleating bubble trajectory is modified by incorporating a bubble diverter placed axially at the bottom of the tube. The nucleating bubble at the base of the diverter experiences a tangential evaporation momentum force (EMF) which causes the bubble to grow sideways away from the tube and avoid localized bubble patches that are responsible for CHF initiation. High speed imaging confirmed the lateral displacement of the bubbles away from the diverter closely matched with the theoretical predictions using EMF and buoyancy forces. Since the EMF is stronger at higher heat fluxes, bubble displacement increases with heat flux and results in the formation of separate liquid-vapor pathways wherein the liquid enters almost unobstructed at the bottom and the vapor bubble leaves sideways. Experimental results yielded CHF and HTC enhancements of ˜60% and ˜75%, respectively, with the diverter configuration when compared to a plain tube. This work can be used for guidance in developing enhancement strategies to effectively modulate the liquid-vapor flow around the heater surface at various locations to enhance HTC and CHF.

Independent and collective roles of surface structures at different length scales on pool boiling heat transfer

PubMed Central

Li, Calvin H.; Rioux, Russell P.

2016-01-01

Spherical Cu nanocavity surfaces are synthesized to examine the individual role of contact angles in connecting lateral Rayleigh-Taylor wavelength to vertical Kevin-Helmholtz wavelength on hydrodynamic instability for the onset of pool boiling Critical Heat Flux (CHF). Solid and porous Cu pillar surfaces are sintered to investigate the individual role of pillar structure pitch at millimeter scale, named as module wavelength, on hydrodynamic instability at CHF. Last, spherical Cu nanocavities are coated on the porous Cu pillars to create a multiscale Cu structure, which is studied to examine the collective role and relative significance of contact angles and module wavelength on hydrodynamic instability at CHF, and the results indicate that module wavelength plays the dominant role on hydrodynamic instability at CHF when the height of surface structures is equal or above ¼ Kelvin-Helmholtz wavelength. Pool boiling Heat Transfer Coefficient (HTC) enhancements on spherical Cu nanocavity surfaces, solid and porous Cu pillar surfaces, and the integrated multiscale structure have been investigated, too. The experimental results reveal that the nanostructures and porous pillar structures can be combined together to achieve even higher enhancement of HTC than that of individual structures. PMID:27841322

Experimental investigation of time and repeated cycles in nucleate pool boiling of alumina/water nanofluid on polished and machined surfaces

NASA Astrophysics Data System (ADS)

Rajabzadeh Dareh, F.; Haghshenasfard, M.; Nasr Esfahany, M.; Salimi Jazi, H.

2018-06-01

Pool boiling heat transfer of pure water and nanofluids on a copper block has been studied experimentally. Nanofluids with various concentrations of 0.0025, 0.005 and 0.01 vol.% are employed and two simple surfaces (polished and machined copper surface) are used as the heating surfaces. The results indicated that the critical heat flux (CHF) in boiling of fluids on the polished surface is 7% higher than CHF on the machined surface. In the case of machined surface, the heat transfer coefficient (HTC) of 0.01 vol.% nanofluid is about 37% higher than HTC of base fluid, while in the polished surface the average HTC of 0.01% nanofluid is about 19% lower than HTC of the pure water. The results also showed that the boiling time and boiling cycles on the polished surface changes the heat transfer performance. By increasing the boiling time from 5 to 10 min, the roughness enhances about 150%, but by increasing the boiling time to 15 min, the roughness enhancement is only 8%.

Enhanced Boiling on Micro-Configured Composite Surfaces Under Microgravity Conditions

NASA Technical Reports Server (NTRS)

Zhang, Nengli; Chai, An-Ti

1999-01-01

In order to accommodate the growing thermal management needs of future space platforms, several two-phase active thermal control systems (ATCSs) have evolved and were included in the designs of space stations. Compared to the pumped single-phase liquid loops used in the conventional Space Transportation System and Spacelab, ATCSs offer significant benefits that may be realized by adopting a two-phase fluid-loop system. Alternately, dynamic power systems (DPSs), based on the Rankine cycle, seem inevitably to be required to supply the electrical power requirements of expanding space activities. Boiling heat transfer is one of the key technologies for both ATCSs and DPSs. Nucleate boiling near critical heat flux (CHF) can transport very large thermal loads with much smaller device size and much lower pumping power. However, boiling performance deteriorates in a reduced gravity environment and operation in the CHF regime is precarious because any slight overload will cause the heat transfer to suddenly move to the film boiling regime, which in turn, will result in burnout of the heat transfer surfaces. New materials, such as micro-configured metal-graphite composites, can provide a solution for boiling enhancement. It has been shown experimentally that this type of material manifests outstanding boiling heat transfer performance and their CHF is also extended to higher values. Due to the high thermal conductivity of graphite fiber (up to 1,200 W/m-K in the fiber direction), the composite surfaces are non-isothermal during the boiling process. The composite surfaces are believed to have a much wider safe operating region (a more uniform boiling curve in the CHF regime) because non-isothermal surfaces have been found to be less sensitive to variations of wall superheat in the CHF regime. The thermocapillary forces formed by the temperature difference between the fiber tips and the metal matrix play a more important role than the buoyancy in the bubble detachment, for the bubble detachment manifests itself by a necking process which should not be weakened by reduced gravity. In addition, the composite surfaces introduce no extra pressure drop, no fouling and do not impose significant primary or maintenance costs. All of these suggest that this type of composite is an ideal material for the challenge of accounting for both reliability and economy of the relevant components applied in the ATCSs, the DPSs and other devices in future space missions. The aim of the proposed work is to experimentally investigate high nucleate pool boiling performance on a micro-configured metal-graphite composite surface and to determine the mechanisms of the nucleate boiling heat transfer both experimentally and theoretically. Freon-113 and water will be used as the test liquids to investigate wettability effects on boiling characteristics. The Cu-Gr and Al-Gr composites with various volume fractions of graphite fibers will be tested to obtain the heat transfer characteristic data in the nucleate boiling region and in the CHF regime. In the experiments, the bubble emission and coalescence processes will be recorded by a video camera with a magnifying borescope probe immersed in the working fluid. The temperature profile in the thermal boundary layer on the composite surfaces will be measured by a group of micro thermocouples consisting of four ultra fine micro thermocouples. This instrument was developed and successfully used to measure the temperature profile of evaporating liquid thin layers by the proposers in a study performed at the NASA/Lewis Research Center. A two tier model to explain the nucleate boiling process and the performance enhancement on the composite surfaces has been suggested by the authors. According to the model, the thicknesses of the microlayer and the macrolayer underneath the bubbles and mushrooms, can be estimated by the geometry of the composite surface. The experimental results will be compared to the predictions from the model, and in turn, to revise and improve it.

Critical Heat Flux in Pool Boiling on Metal-Graphite Composite Surfaces

NASA Technical Reports Server (NTRS)

Zhang, Nengli; Yang, Wen-Jei; Chao, David F.; Chao, David F. (Technical Monitor)

2000-01-01

A study is conducted on high heat-flux pool boiling of pentane on micro-configured composite surfaces. The boiling surfaces are copper-graphite (Cu-Gr) and aluminum-graphite (Al-Gr) composites with a fiber volume concentration of 50%. The micro-graphite fibers embedded in the matrix contribute to a substantial enhancement in boiling heat-transfer performance. Correlation equations are obtained for both the isolated and coalesced bubble regimes, utilizing a mathematical model based on a metal-graphite, two-tier configuration with the aid of experimental data. A new model to predict the critical heat flux (CHF) on the composites is proposed to explain the fundamental aspects of the boiling phenomena. Three different factors affecting the CHF are considered in the model. Two of them are expected to become the main agents driving vapor volume detachment under microgravity conditions, using the metal-graphite composite surfaces as the heating surface and using liquids with an unusual Marangoni effect as the working fluid.

Spray cooling characteristics of nanofluids for electronic power devices.

PubMed

Hsieh, Shou-Shing; Leu, Hsin-Yuan; Liu, Hao-Hsiang

2015-01-01

The performance of a single spray for electronic power devices using deionized (DI) water and pure silver (Ag) particles as well as multi-walled carbon nanotube (MCNT) particles, respectively, is studied herein. The tests are performed with a flat horizontal heated surface using a nozzle diameter of 0.5 mm with a definite nozzle-to-target surface distance of 25 mm. The effects of nanoparticle volume fraction and mass flow rate of the liquid on the surface heat flux, including critical heat flux (CHF), are explored. Both steady state and transient data are collected for the two-phase heat transfer coefficient, boiling curve/ cooling history, and the corresponding CHF. The heat transfer removal rate can reach up to 274 W/cm(2) with the corresponding CHF enhancement ratio of 2.4 for the Ag/water nanofluids present at a volume fraction of 0.0075% with a low mass flux of 11.9 × 10(-4) kg/cm(2)s.

Measurement of Key Pool BOiling Parameters in nanofluids for Nuclerar Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bang, In C; Buongiorno, Jdacopo; Hu, Lin-wen

Nanofluids, colloidal dispersions of nanoparticles in a base fluid such as water, can afford very significant Critical Heat Flux (CHF) enhancement. Such engineered fluids potentially could be employed in reactors as advanced coolants in safety systems with significant safety and economic advantages. However, a satisfactory explanation of the CHF enhancement mechanism in nanofluids is lacking. To close this gap, we have identified the important boiling parameters to be measured. These are the properties (e.g., density, viscosity, thermal conductivity, specific heat, vaporization enthalpy, surface tension), hydrodynamic parameters (i.e., bubble size, bubble velocity, departure frequency, hot/dry spot dynamics) and surface conditions (i.e.,more » contact angle, nucleation site density). We have also deployed a pool boiling facility in which many such parameters can be measured. The facility is equipped with a thin indium-tin-oxide heater deposited over a sapphire substrate. An infra-red high-speed camera and an optical probe are used to measure the temperature distribution on the heater and the hydrodynamics above the heater, respectively. The first data generated with this facility already provide some clue on the CHF enhancement mechanism in nanofluids. Specifically, the progression to burnout in a pure fluid (ethanol in this case) is characterized by a smoothly-shaped and steadily-expanding hot spot. By contrast, in the ethanol-based nanofluid the hot spot pulsates and the progression to burnout lasts longer, although the nanofluid CHF is higher than the pure fluid CHF. The presence of a nanoparticle deposition layer on the heater surface seems to enhance wettability and aid hot spot dissipation, thus delaying burnout.« less

Nano-inspired fluidic interactivity for boiling heat transfer: impact and criteria

PubMed Central

Kim, Beom Seok; Choi, Geehong; Shin, Sangwoo; Gemming, Thomas; Cho, Hyung Hee

2016-01-01

The enhancement of boiling heat transfer, the most powerful energy-transferring technology, will lead to milestones in the development of high-efficiency, next-generation energy systems. Perceiving nano-inspired interface functionalities from their rough morphologies, we demonstrate interface-induced liquid refreshing is essential to improve heat transfer by intrinsically avoiding Leidenfrost phenomenon. High liquid accessibility of hemi-wicking and catalytic nucleation, triggered by the morphological and hydrodynamic peculiarities of nano-inspired interfaces, contribute to the critical heat flux (CHF) and the heat transfer coefficient (HTC). Our experiments show CHF is a function of universal hydrodynamic characteristics involving interfacial liquid accessibility and HTC is improved with a higher probability of smaller nuclei with less superheat. Considering the interface-induced and bulk liquid accessibility at boiling, we discuss functionalizing the interactivity between an interface and a counteracting fluid seeking to create a novel interface, a so-called smart interface, for a breakthrough in boiling and its pragmatic application in energy systems. PMID:27708341

Effect of Running Parameters on Flow Boiling Instabilities in Microchannels.

PubMed

Zong, Lu-Xiang; Xu, Jin-Liang; Liu, Guo-Hua

2015-04-01

Flow boiling instability (FBI) in microchannels is undesirable because they can induce the mechanical vibrations and disturb the heat transfer characteristics. In this study, the synchronous optical visualization experimental system was set up. The pure acetone liquid was used as the working fluid, and the parallel triangle silicon microchannel heat sink was designed as the experimental section. With the heat flux ranging from 0-450 kW/m2 the microchannel demand average pressure drop-heater length (Δp(ave)L) curve for constant low mass flux, and the demand pressure drop-mass flux (Δp(ave)G) curve for constant length on main heater surface were obtained and studied. The effect of heat flux (q = 188.28, 256.00, and 299.87 kW/m2), length of main heater surface (L = 4.5, 6.25, and 8.00 mm), and mass flux (G = 188.97, 283.45, and 377.94 kg/m2s) on pressure drops (Ap) and temperatures at the central point of the main heater surface (Twc) were experimentally studied. The results showed that, heat flux, length of the main heater surface, and mass flux were identified as the important parameters to the boiling instability process. The boiling incipience (TBI) and critical heat flux (CHF) were early induced for the lower mass flux or the main heater surface with longer length. With heat flux increasing, the pressure drops were linearly and slightly decreased in the single liquid region but increased sharply in the two phase flow region, in which the flow boiling instabilities with apparent amplitude and long period were more easily triggered at high heat flux. Moreover, the system pressure was increased with the increase of the heat flux.

Micro/Nano-Scale Phase Change Systems for Thermal Management and Solar Energy Conversion Applications

NASA Astrophysics Data System (ADS)

Coso, Dusan

The first part of the dissertation presents a study that implements micro and nano scale engineered surfaces for enhancement of evaporation and boiling phase change heat transfer in both capillary wick structures and pool boiling systems. Capillary wicking surfaces are integral components of heat pipes and vapor chamber thermal spreaders often used for thermal management of microelectronic devices. In addition, pool boiling systems can be encountered in immersion cooling systems which are becoming more commonly investigated for thermal management applications of microelectronic devices and even data centers. The latent heat associated with the change of state from liquid to vapor, and the small temperature differences required to drive this process yield great heat transfer characteristics. Additionally, since no external energy is required to drive the phase change process, these systems are great for portable devices and favorable for reduction of cost and energy consumption over alternate thermal management technologies. Most state of the art capillary wicks used in these devices are typically constructed from sintered copper media. These porous structures yield high surface areas of thin liquid film where evaporation occurs, thus promoting phase change heat transfer. However, thermal interfaces at particle point contacts formed during the sintering process and complex liquid/vapor flow within these wick structures yield high thermal and liquid flow resistances and limit the maximum heat flux they can dissipate. In capillary wicks the maximum heat flux is typically governed by the capillary or boiling limits and engineering surfaces that delay these limitations and yield structures with large surface areas of thin liquid film where phase change heat transfer is promoted is highly desired. In this study, biporous media consisting of microscale pin fins separated by microchannels are examined as candidate structures for the evaporator wick of a vapor chamber heat pipe. Smaller pores are used to generate high capillary suction, while larger microchannels are used to alleviate flow resistance. The heat transfer coefficient is found to depend on the area coverage of a liquid film with thickness on the order of a few microns near the meniscus of the triple phase contact line. We manipulate the area coverage and film thickness by varying the surface area-to-volume ratio through the use of microstructuring. In some samples, a transition from evaporative heat transfer to nucleate boiling is observed. While it is difficult to identify when the transition occurs, one can identify regimes where evaporation dominates over nucleate boiling and vice versa. Heat fluxes of 277.0 (+/- 9.7) W/cm2 can be dissipated by wicks with heaters of area 1 cm2, while heat fluxes up to 733.1 (+/- 103.4) W/cm2 can be dissipated by wicks with smaller heaters intended to simulate local hot-spots. In pool boiling systems that are encountered in immersion cooling applications, the heat transfer coefficient (HTC) is governed by the bubble nucleation site density and the agitation in the liquid/vapor flow these bubbles produce when they detach from the surface. The nucleation site density and release rate is usually determined by the surface morphology. Another important parameter in pool boiling systems is the maximum heat flux (CHF) that can safely be dissipated. In practice, this quantity is about two orders of magnitude smaller than limitations suggested by kinetic theory. For essentially infinite, smooth, well wetted surfaces, hydrodynamic instability theories capturing liquid/vapor interactions away from the heated surface have been successful in predicting CHF. On finite micro and nano structured surfaces where applying the hydrodynamic theory formulation is not easily justified, other effects may contribute to phase change heat transfer characteristics. Here, we also present a pool boiling study on biporous microstructured surfaces used in capillary wick experiments. Structures are manipulated by reduction of pore size to determine if increased capillary pressure can enhance rewetting from heater edges and delay CHF. A comparative study between the two experimental systems indicates that while the capillary limitation is significant in capillary wick experiments, for these well wetted microstructured surfaces used in pool boiling systems the hydrodynamic limitation defined based on heater size causes the occurrence of CHF. Other hierarchical nanowire surfaces containing periodic microscale cavities are investigated as well and are seen to yield a ˜2.4 fold increase in heat transfer coefficient characteristics while not compromising CHF compared to surfaces where cavities are not present. These studies indicate pathways for enhancement of heat transfer coefficient via implementing hierarchical structures, while no clear method in increasing CHF is determined for finite size surfaces of various morphologies. In the second part of this dissertation, solar energy storage is sought in 'phase change' of photochromic molecular systems: the storage of solar energy in the chemical bonds of photosensitive molecules (a photochemical reaction) and subsequent recovery of the energy in a back reaction in the form of heat, reversibly. These molecular systems are interesting alternatives to photovoltaic and solar thermal technologies which cannot satisfy the needs of load leveling, or for portable municipal heating applications. Typically made of organic compounds, these molecules have become known for rapid decomposition, short energy storage time scales and poor energy storing efficiencies. Thus, they have been abandoned as practical solar energy storage systems in the past several decades. On the other hand, organometallic molecular systems have not been extensively probed for these applications. Recent research has indicated that organometallic (fulvalene)diruthenium FvRu2 has demonstrated excellent energy storage characteristic and durability. Here, we report on a full cycle molecular solar thermal (MOST) microfluidic system based on a bis(1,1-dimethyltridecyl) substituted derivative of FvRu2 that allows for long term solar energy storage (110 J/g), and "on demand" energy release upon exposure to a catalyst. The microfluidic systems developed here are excellent for photoconversion characterization and scrutinizing potential catalysts and can be extended to studying many other molecular systems. The objective of the work presented here is to demonstrate that "on demand" solar energy storage and release in MOST systems is viable and motivate future research on other photochromic organometallic systems.

Ultrahigh Flux Thin Film Boiling Heat Transfer Through Nanoporous Membranes.

PubMed

Wang, Qingyang; Chen, Renkun

2018-05-09

Phase change heat transfer is fundamentally important for thermal energy conversion and management, such as in electronics with power density over 1 kW/cm 2 . The critical heat flux (CHF) of phase change heat transfer, either evaporation or boiling, is limited by vapor flux from the liquid-vapor interface, known as the upper limit of heat flux. This limit could in theory be greater than 1 kW/cm 2 on a planar surface, but its experimental realization has remained elusive. Here, we utilized nanoporous membranes to realize a new "thin film boiling" regime that resulted in an unprecedentedly high CHF of over 1.2 kW/cm 2 on a planar surface, which is within a factor of 4 of the theoretical limit, and can be increased to a higher value if mechanical strength of the membranes can be improved (demonstrated with 1.85 kW/cm 2 CHF in this work). The liquid supply is achieved through a simple nanoporous membrane that supports the liquid film where its thickness automatically decreases as heat flux increases. The thin film configuration reduces the conductive thermal resistance, leads to high frequency bubble departure, and provides separate liquid-vapor pathways, therefore significantly enhances the heat transfer. Our work provides a new nanostructuring approach to achieve ultrahigh heat flux in phase change heat transfer and will benefit both theoretical understanding and application in thermal management of high power devices of boiling heat transfer.

Vapor bubble evolution on a heated surface containing open microchannels

NASA Astrophysics Data System (ADS)

Forster, Christopher J.; Glezer, Ari; Smith, Marc K.

2011-11-01

Power electronics require cooling technologies capable of high heat fluxes at or below the operating temperatures of these devices. Boiling heat transfer is an effective choice for such cooling, but it is limited by the critical heat flux (CHF), which is typically near 125 W/cm2 for pool boiling of water on a flat plate at standard pressure and gravity. One method of increasing CHF is to incorporate an array of microchannels into the heated surface. Microchannels have been experimentally shown to improve CHF, and the goal of this study is to determine the primary mechanisms associated with the microchannels that allow for the increased CHF. While the use of various microstructures is not new, the emphasis of previous work has been on heat transfer aspects, as opposed to the fluid dynamics inside and in the vicinity of the microchannels. This work considers the non-isothermal fluid motion during bubble growth and departure by varying channel geometry, spacing, and heat flux input using a level-set method including vaporization and condensation. These results and the study of the underlying mechanisms will aid in the design optimization of microchannel-based cooling devices. Supported by ONR.

A study of nucleate boiling and critical heat flux with EHD enhancement

NASA Astrophysics Data System (ADS)

Hristov, Y.; Zhao, D.; Kenning, D. B. R.; Sefiane, K.; Karayiannis, T. G.

2009-05-01

The paper describes results from an experimental and theoretical study of the effect of an electric field on nucleate boiling and the critical heat flux (CHF) in pool boiling of R123 at atmospheric pressure on a horizontal wall with a smooth surface. Two designs of electrode (parallel rods and wire mesh) were used. The experimental data exhibit some differences from the data obtained by other researchers in similar experiments on a wall with a different surface finish and with a slightly different design of wire mesh electrode. The hydrodynamic model for EHD enhancement of CHF cannot reconcile the differences. A theoretical model has been developed for the growth of a single vapour bubble on a superheated wall in an electric field, leading to a numerical simulation based on the level-set method. The model includes matching of sub-models for the micro- and macro-regions, conduction in the wall, distortion of the electric field by the bubble, the temperature dependence of electrical properties and free-charge generation. In the present form of the model, some of these effects are realised in an approximate form. The capability to investigate dry-spot formation and wall temperature changes that might lead to CHF has been demonstrated.

Methodology for the study of the boiling crisis in a nuclear fuel bundle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crecy, F. de; Juhel, D.

1995-09-01

The boiling crisis is one of the phenoumena limiting the available power from a nuclear power plant. It has been widely studied for decades, and numerous data, models, correlations or tables are now available in the literature. If we now try to obtain a general view of previous work in this field, we may note that there are several ways of tackling the subject. The mechanistic models try to model the two-phase flow topology and the interaction between different sublayers, and must be validated by comparison with basic experiments, such as DEBORA, where we try to obtain some detailed informationsmore » on the two-phase flow pattern in a pure and simple geometry. This allows us to obtain better knowledge of the so-called {open_quotes}intrinsic effect{close_quotes}. These models are not yet acceptable for nuclear use. As the geometry of the rod bundles and grids has a tremendous importance for the Critical Heat Flux (CHF), it is mandatory to have more precise results for a given fuel rod bundle in a restricted range of parameters: this leads to the empirical approach, using empirical CHF predictors (tables, correlations, splines, etc...). One of the key points of such a method is the obtaining local thermohydraulic values, that is to say the evaluation of the so-called {open_quotes}mixing effect{close_quotes}. This is done by a subchannel analysis code or equivalent, which can be qualified on two kinds of experiments: overall flow measurements in a subchannel, such as HYDROMEL in single-phase flow or GRAZIELLA in two-phase flow, or detailed measurements inside a subchannel, such as AGATE. Nevertheless, the final qualification of a specific nuclear fuel, i.e. the synthesis of these mechanistic and empirical approaches, intrinsic and mixing effects, etc..., must be achieved on a global test such as OMEGA. This is the strategy used in France by CEA and its partners FRAMATOME and EdF.« less

Heat Transfer Performances of Pool Boiling on Metal-Graphite Composite Surfaces

NASA Technical Reports Server (NTRS)

Zhang, Nengli; Chao, David F.; Yang, Wen-Jei

2000-01-01

Nucleate boiling, especially near the critical heat flux (CHF), can provide excellent economy along with high efficiency of heat transfer. However, the performance of nucleate boiling may deteriorate in a reduced gravity environment and the nucleate boiling usually has a potentially dangerous characteristic in CHF regime. That is, any slight overload can result in burnout of the boiling surface because the heat transfer will suddenly move into the film-boiling regime. Therefore, enhancement of nucleate boiling heat transfer becomes more important in reduced gravity environments. Enhancing nucleate boiling and critical heat flux can be reached using micro-configured metal-graphite composites as the boiling surface. Thermocapillary force induced by temperature difference between the graphite-fiber tips and the metal matrix, which is independent of gravity, will play an important role in bubble detachment. Thus boiling heat transfer performance does not deteriorate in a reduced-gravity environment. Based on the existing experimental data, and a two-tier theoretical model, correlation formulas are derived for nucleate boiling on the copper-graphite and aluminum-graphite composite surfaces, in both the isolated and coalesced bubble regimes. Experimental studies were performed on nucleate pool boiling of pentane on cooper-graphite (Cu-Gr) and aluminum-graphite (Al-Gr) composite surfaces with various fiber volume concentrations for heat fluxes up to 35 W per square centimeter. It is revealed that a significant enhancement in boiling heat transfer performance on the composite surfaces is achieved, due to the presence of micro-graphite fibers embedded in the matrix. The onset of nucleate boiling (the isolated bubble regime) occurs at wall superheat of about 10 C for the Cu-Gr surface and 15 C for the Al-Gr surface, much lower than their respective pure metal surfaces. Transition from an isolated bubble regime to a coalesced bubble regime in boiling occurs at a superheat of about 14 C on Cu-Gr surface and 19 C on Al-Gr surface.

FILM-30: A Heat Transfer Properties Code for Water Coolant

DOE Office of Scientific and Technical Information (OSTI.GOV)

MARSHALL, THERON D.

2001-02-01

A FORTRAN computer code has been written to calculate the heat transfer properties at the wetted perimeter of a coolant channel when provided the bulk water conditions. This computer code is titled FILM-30 and the code calculates its heat transfer properties by using the following correlations: (1) Sieder-Tate: forced convection, (2) Bergles-Rohsenow: onset to nucleate boiling, (3) Bergles-Rohsenow: partially developed nucleate boiling, (4) Araki: fully developed nucleate boiling, (5) Tong-75: critical heat flux (CHF), and (6) Marshall-98: transition boiling. FILM-30 produces output files that provide the heat flux and heat transfer coefficient at the wetted perimeter as a function ofmore » temperature. To validate FILM-30, the calculated heat transfer properties were used in finite element analyses to predict internal temperatures for a water-cooled copper mockup under one-sided heating from a rastered electron beam. These predicted temperatures were compared with the measured temperatures from the author's 1994 and 1998 heat transfer experiments. There was excellent agreement between the predicted and experimentally measured temperatures, which confirmed the accuracy of FILM-30 within the experimental range of the tests. FILM-30 can accurately predict the CHF and transition boiling regimes, which is an important advantage over current heat transfer codes. Consequently, FILM-30 is ideal for predicting heat transfer properties for applications that feature high heat fluxes produced by one-sided heating.« less

Investigation of saturated critical heat flux in a single, uniformly heated microchannel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wojtan, Leszek; Revellin, Remi; Thome, John R.

2006-08-15

A series of tests have been performed to determine the saturated critical heat flux (CHF) in 0.5 and 0.8mm internal diameter microchannel tubes as a function of refrigerant mass velocity, heated length, saturation temperature and inlet liquid subcooling. The tested refrigerants were R-134a and R-245fa and the heated length of microchannel was varied between 20 and 70mm. The results show a strong dependence of CHF on mass velocity, heated length and microchannel diameter but no influence of liquid subcooling (2-15{sup o}C) was observed. The experimental results have been compared to the well-known CHF single-channel correlation of Y. Katto and H.more » Ohno [An improved version of the generalized correlation of critical heat flux for the forced convective boiling in uniformly heated vertical tubes, Int. J. Heat and Mass Transfer 27 (9) (1984) 1641-1648] and the multichannel correlation of W. Qu and I. Mudawar [Measurement and correlation of critical heat flux in two-phase microchannel heat sinks, Int. J. Heat and Mass Transfer 47 (2004) 2045-2059]. The comparison shows that the correlation of Katto-Ohno predicts microchannel data with a mean absolute error of 32.8% with only 41.2% of the data falling within a +/-15% error band. The correlation of Qu and Mudawar shows the same trends as the CHF data but significantly overpredicts them. Based on the present experimental data, a new microscale version of the Katto-Ohno correlation for the prediction of CHF during saturated boiling in microchannels has been proposed. (author)« less

Marangoni Effects in the Boiling of Binary Fluid Mixtures

NASA Technical Reports Server (NTRS)

Ahmed, Sayeed; Carey, Van P.; Motil, Brian

1996-01-01

Results of very recent experimental studies indicate that during nucleate boiling in some binary mixture, Marangoni effects augment the gravity driven flow of liquid towards the heated surface. With gravity present, it is impossible to separate the two effects. The reduced gravity environment gives an unique opportunity to explore th role of Marangoni effects on the boiling mechanisms free of gravitational body forces that obscure the role of such effects. However, recent experimental results suggest that under reduced gravity conditions, Marangoni effects is the dominant mechanism of vapor-liquid exchange at the surface for some binary mixture. To further explore such effects, experiments have been conducted with water/2-propanol mixtures at three different concentrations under normal gravity with different orientations of the heater surface and under reduce gravity aboard the DC-9 aircraft at NASA Lewis Research Center. The system pressure was sub atmospheric (approx. 8 kP at 1g(n)) and the bulk liquid temperature varied from low subcooling to near saturation. The molar concentrations of 2-propanol tested were 0.015, 0.025, and 0.1. Boiling curves were obtained both for high gravity (approx. 2g(n)) and reduce gravity (approx. 0.01g(n)). For each concentration of 2-propanol, the critical heat flux has been determined in the flight experiments only for reduced gravity conditions. Comparison of boiling curves and CHF obtained under l-g(n) an reduced gravity indicates that boiling mechanism in this mixtures is nearly independent of gravity. The results also indicate that the Marangoni mechanism is strong enough in these mixtures to sustain the boiling under reduced gravity conditions.

Boiling and quenching heat transfer advancement by nanoscale surface modification.

PubMed

Hu, Hong; Xu, Cheng; Zhao, Yang; Ziegler, Kirk J; Chung, J N

2017-07-21

All power production, refrigeration, and advanced electronic systems depend on efficient heat transfer mechanisms for achieving high power density and best system efficiency. Breakthrough advancement in boiling and quenching phase-change heat transfer processes by nanoscale surface texturing can lead to higher energy transfer efficiencies, substantial energy savings, and global reduction in greenhouse gas emissions. This paper reports breakthrough advancements on both fronts of boiling and quenching. The critical heat flux (CHF) in boiling and the Leidenfrost point temperature (LPT) in quenching are the bottlenecks to the heat transfer advancements. As compared to a conventional aluminum surface, the current research reports a substantial enhancement of the CHF by 112% and an increase of the LPT by 40 K using an aluminum surface with anodized aluminum oxide (AAO) nanoporous texture finish. These heat transfer enhancements imply that the power density would increase by more than 100% and the quenching efficiency would be raised by 33%. A theory that links the nucleation potential of the surface to heat transfer rates has been developed and it successfully explains the current finding by revealing that the heat transfer modification and enhancement are mainly attributed to the superhydrophilic surface property and excessive nanoscale nucleation sites created by the nanoporous surface.

Length Scale and Gravity Effects on Microgravity Boiling Heat Transfer

NASA Technical Reports Server (NTRS)

Kim, Jungho; McQuillen, John; Balombin, Joe

2002-01-01

Boiling is a complex phenomenon where hydrodynamics, heat transfer, mass transfer, and interfacial phenomena are tightly interwoven. An understanding of boiling and critical heat flux in microgravity environments is of importance to space based hardware and processes such as heat exchange, cryogenic fuel storage and transportation, electronic cooling, and material processing due to the large amounts of heat that can be removed with relatively little increase in temperature. Although research in this area has been performed in the past four decades, the mechanisms by which heat is removed from surfaces in microgravity are still unclear. In earth gravity, buoyancy is an important parameter that affects boiling heat transfer through the rate at which bubbles are removed from the surface. A simple model describing the bubble departure size based on a quasistatic force balance between buoyancy and surface tension is given by the Fritz [I] relation: Bo(exp 1/2) = 0.0208 theta where Bo is the ratio between buoyancy and surface tension forces. For small, rapidly growing bubbles, inertia associated with the induced liquid motion can also cause bubble departure. In microgravity, the magnitude of effects related to natural convection and buoyancy are small and physical mechanisms normally masked by natural convection in earth gravity such as Marangoni convection can substantially influence the boiling and vapor bubble dynamics. CHF (critical heat transfer) is also substantially affected by microgravity. In 1 g environments, Bo has been used as a correlating parameter for CHF. Zuber's CHF model for an infinite horizontal surface assumes that vapor columns formed by the merger of bubbles become unstable due to a Helmholtz instability blocking the supply of liquid to the surface. The jets are spaced lambda(sub D) apart, where lambda(sub D) = 2pi square root of 3[(sigma)/(g(rho(sub l) - rho(sub v)](exp 1/2) = 2pi square root of 3 L Bo(exp -1/2) = square root of 3 lambda(sub c) and is the wavelength that amplifies most rapidly. The critical wavelength, lambda(sub c), is the wavelength below which a vapor layer underneath a liquid layer is stable. For heaters with Bo smaller than about 3 (heaters smaller than lambda(sub D)), the above model is not applicable, and surface tension effects dominate. Bubble coalescence is thought to be the mechanism for CHF under these conditions. Small Bo can result by decreasing the size of a heater in earth gravity, or by operating a large heater in a lower gravity environment. In the microgravity of space, even large heaters can have low Bo, and models based on Helmholtz instability should not be applicable. The macrolayer model of Haramura and Katto is dimensionally equivalent to Zuber's model and has the same dependence on gravity, so it should not be applicable as well. The goal of this work is to determine how boiling heat transfer mechanisms in a low-g environment are altered from those at higher gravity levels. Boiling data using a microheater array was obtained under gravity environments ranging from 1.8 g to 0.02 g with heater sizes ranging from 2.7 mm to 1 mm. The boiling behavior for 2.7 mm at 0.02 g looked quite similar to boiling on the 1 mm heater at 1 g-the formation of a large primary bubble surrounded by smaller satellite bubbles was observed under both conditions. The similarity suggests that for heaters smaller than some fraction of I(sub c), coalescence and surface tension dominate boiling heat transfer. It also suggests that microgravity boiling can be studied by studying boiling on very small heaters.

A scaling law for the local CHF on the external bottom side of a fully submerged reactor vessel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheung, F.B.; Haddad, K.H.; Liu, Y.C.

1997-02-01

A scaling law for estimating the local critical heat flux on the outer surface of a heated hemispherical vessel that is fully submerged in water has been developed from the results of an advanced hydrodynamic CHF model for pool boiling on a downward facing curved heating surface. The scaling law accounts for the effects of the size of the vessel, the level of liquid subcooling, the intrinsic properties of the fluid, and the spatial variation of the local critical heat flux along the heating surface. It is found that for vessels with diameters considerably larger than the characteristic size ofmore » the vapor masses, the size effect on the local critical heat flux is limited almost entirely to the effect of subcooling associated with the local liquid head. When the subcooling effect is accounted for separately, the local CHF limit is nearly independent of the vessel size. Based upon the scaling law developed in this work, it is possible to merge, within the experimental uncertainties, all the available local CHF data obtained for various vessel sizes under both saturated and subcooled boiling conditions into a single curve. Applications of the scaling law to commercial-size vessels have been made for various system pressures and water levels above the heated vessel. Over the range of conditions explored in this study, the local CHF limit is found to increase by a factor of two or more from the bottom center to the upper edge of the vessel. Meanwhile, the critical heat flux at a given angular position of the heated vessel is also found to increase appreciably with the system pressure and the water level.« less

Critical heat flux for water boiling in channels. Modern state, typical regularities, unsolved problems, and ways for solving them (a review)

NASA Astrophysics Data System (ADS)

Bobkov, V. P.

2015-02-01

Some general matters concerned with description of burnout in channels are outlined. Data obtained from experimental investigations on critical heat fluxes (CHF) in different channels, CHF data banks, the main determining parameters, CHF basic dependences, and a system of correction functions are discussed. Two methods for estimating the CHF description errors are analyzed. The influence of operating parameters, transverse sizes of channels, and conditions at their inlet are analyzed. The effects of heat-transfer surface shape and heat supply arrangement are considered for concentric annular channels. The notions of a thermal boundary layer and an elementary thermal cell during burnout in channels with an intricate cross section are defined. New notions for describing CHF in rod assemblies are introduced: bundle effect, thermal misalignment, assembly-section-averaged and local parameters (for an elementary cell), cell-wise CHF analysis in bundles, and standard and nonstandard cells. Possible influence of wall thermophysical properties on CHF in dense assemblies and other effects are considered. Thermal interaction of nonequivalent cells and the effect of heat supply arrangement over the cell perimeter are analyzed. Special attention is paid to description of the effect the heat release nonuniformity along the channels has on CHF. Objectives to be pursued by studies of CHF in channels of different cross-section shapes are formulated.

Cooling Performance of a Partially-Confined FC-72 Spray: The Effect of Dissolved Air (Postprint)

DTIC Science & Technology

2007-01-01

plate FC = FC-72 fluid htr = heater conductive layer int = interface between heater substrate and insulating support post m = measured s = heater... microporous enhanced surface and a plain reference surface, and developed correlations for nucleate boiling and CHF. The results of the experiment...8Rainey, K. N., You, S. M., and Lee, S., “Effect of Pressure, Subcooling, and Dissolved Gas on Pool Boiling Heat Transfer from Microporous Surfaces

Steady-State Thermal-Hydraulics Analyses for the Conversion of BR2 to Low Enriched Uranium Fuel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Licht, J.; Bergeron, A.; Dionne, B.

The code PLTEMP/ANL version 4.2 was used to perform the steady-state thermal-hydraulic analyses of the BR2 research reactor for conversion from Highly-Enriched to Low Enriched Uranium fuel (HEU and LEU, respectively). Calculations were performed to evaluate different fuel assemblies with respect to the onset of nucleate boiling (ONB), flow instability (FI), critical heat flux (CHF) and fuel temperature at beginning of cycle conditions. The fuel assemblies were characteristic of fresh fuel (0% burnup), highest heat flux (16% burnup), highest power (32% burnup) and highest burnup (46% burnup). Results show that the high heat flux fuel element is limiting for ONB,more » FI, and CHF, for both HEU and LEU fuel, but that the high power fuel element produces similar margin in a few cases. The maximum fuel temperature similarly occurs in both the high heat flux and high power fuel assemblies for both HEU and LEU fuel. A sensitivity study was also performed to evaluate the variation in fuel temperature due to uncertainties in the thermal conductivity degradation associated with burnup.« less

Nanofluid two-phase flow and thermal physics: a new research frontier of nanotechnology and its challenges.

PubMed

Cheng, Lixin; Bandarra Filho, Enio P; Thome, John R

2008-07-01

Nanofluids are a new class of fluids engineered by dispersing nanometer-size solid particles in base fluids. As a new research frontier, nanofluid two-phase flow and thermal physics have the potential to improve heat transfer and energy efficiency in thermal management systems for many applications, such as microelectronics, power electronics, transportation, nuclear engineering, heat pipes, refrigeration, air-conditioning and heat pump systems. So far, the study of nanofluid two-phase flow and thermal physics is still in its infancy. This field of research provides many opportunities to study new frontiers but also poses great challenges. To summarize the current status of research in this newly developing interdisciplinary field and to identify the future research needs as well, this paper focuses on presenting a comprehensive review of nucleate pool boiling, flow boiling, critical heat flux, condensation and two-phase flow of nanofluids. Even for the limited studies done so far, there are some controversies. Conclusions and contradictions on the available nanofluid studies on physical properties, two-phase flow, heat transfer and critical heat flux (CHF) are presented. Based on a comprehensive analysis, it has been realized that the physical properties of nanofluids such as surface tension, liquid thermal conductivity, viscosity and density have significant effects on the nanofluid two-phase flow and heat transfer characteristics but the lack of the accurate knowledge of these physical properties has greatly limited the study in this interdisciplinary field. Therefore, effort should be made to contribute to the physical property database of nanofluids as a first priority. Secondly, in particular, research on nanofluid two-phase flow and heat transfer in microchannels should be emphasized in the future.

Assessment of respiratory flow cycle morphology in patients with chronic heart failure.

PubMed

Garde, Ainara; Sörnmo, Leif; Laguna, Pablo; Jané, Raimon; Benito, Salvador; Bayés-Genís, Antoni; Giraldo, Beatriz F

2017-02-01

Breathing pattern as periodic breathing (PB) in chronic heart failure (CHF) is associated with poor prognosis and high mortality risk. This work investigates the significance of a number of time domain parameters for characterizing respiratory flow cycle morphology in patients with CHF. Thus, our primary goal is to detect PB pattern and identify patients at higher risk. In addition, differences in respiratory flow cycle morphology between CHF patients (with and without PB) and healthy subjects are studied. Differences between these parameters are assessed by investigating the following three classification issues: CHF patients with PB versus with non-periodic breathing (nPB), CHF patients (both PB and nPB) versus healthy subjects, and nPB patients versus healthy subjects. Twenty-six CHF patients (8/18 with PB/nPB) and 35 healthy subjects are studied. The results show that the maximal expiratory flow interval is shorter and with lower dispersion in CHF patients than in healthy subjects. The flow slopes are much steeper in CHF patients, especially for PB. Both inspiration and expiration durations are reduced in CHF patients, mostly for PB. Using the classification and regression tree technique, the most discriminant parameters are selected. For signals shorter than 1 min, the time domain parameters produce better results than the spectral parameters, with accuracies for each classification of 82/78, 89/85, and 91/89 %, respectively. It is concluded that morphologic analysis in the time domain is useful, especially when short signals are analyzed.

An investigation of transition boiling mechanisms of subcooled water under forced convective conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kwang-Won, Lee; Sang-Yong, Lee

1995-09-01

A mechanistic model for forced convective transition boiling has been developed to investigate transition boiling mechanisms and to predict transition boiling heat flux realistically. This model is based on a postulated multi-stage boiling process occurring during the passage time of the elongated vapor blanket specified at a critical heat flux (CHF) condition. Between the departure from nucleate boiling (DNB) and the departure from film boiling (DFB) points, the boiling heat transfer is established through three boiling stages, namely, the macrolayer evaporation and dryout governed by nucleate boiling in a thin liquid film and the unstable film boiling characterized by themore » frequent touches of the interface and the heated wall. The total heat transfer rates after the DNB is weighted by the time fractions of each stage, which are defined as the ratio of each stage duration to the vapor blanket passage time. The model predictions are compared with some available experimental transition boiling data. The parametric effects of pressure, mass flux, inlet subcooling on the transition boiling heat transfer are also investigated. From these comparisons, it can be seen that this model can identify the crucial mechanisms of forced convective transition boiling, and that the transition boiling heat fluxes including the maximum heat flux and the minimum film boiling heat flux are well predicted at low qualities/high pressures near 10 bar. In future, this model will be improved in the unstable film boiling stage and generalized for high quality and low pressure situations.« less

Effect of diameter of metal nanowires on pool boiling heat transfer with FC-72

NASA Astrophysics Data System (ADS)

Kumar G., Udaya; S., Suresh; M. R., Thansekhar; Babu P., Dinesh

2017-11-01

Effect of varying diameter of metal nanowires on pool boiling heat transfer performance is presented in this study. Copper nanowires (CuNWs) of four different diameters (∼35 nm, ∼70 nm, ∼130 nm and ∼200 nm) were grown directly on copper specimen using template-based electrodeposition technique. Both critical heat flux (CHF) and boiling heat transfer coefficient (h) were found to be improved in surfaces with nanowires as compared to the bare copper surface. Moreover, both the parameters were found to increase with increasing diameter of the nanowires. The percentage increases observed in CHF for the samples with nanowires were 38.37%, 40.16%, 48.48% and 45.57% whereas the percentage increase in the heat transfer coefficient were 86.36%, 95.45%, 184.1% and 131.82% respectively as compared to the bare copper surface. Important reasons believed for this enhancement were improvement in micron scale cavity density and cavity size which arises as a result of the coagulation and grouping of nanowires during the drying process. In addition to this, superhydrophilic nature, capillary effect, and enhanced bubble dynamics parameters (bubble frequency, bubble departure diameter, and nucleation site density) were found to be the concurring mechanisms responsible for this enhancement in heat transfer performance. Qualitative bubble dynamics analysis was done for the surfaces involved and the visual observations are provided to support the results presented and discussed.

Steady-State Thermal-Hydraulics Analyses for the Conversion of the BR2 Reactor to LEU

DOE Office of Scientific and Technical Information (OSTI.GOV)

Licht, J. R.; Bergeron, A.; Dionne, B.

BR2 is a research reactor used for radioisotope production and materials testing. It’s a tank-in-pool type reactor cooled by light water and moderated by beryllium and light water. The reactor core consists of a beryllium moderator forming a matrix of 79 hexagonal prisms in a hyperboloid configuration; each having a central bore that can contain a variety of different components such as a fuel assembly, a control or regulating rod, an experimental device, or a beryllium or aluminum plug. Based on a series of tests, the BR2 operation is currently limited to a maximum allowable heat flux of 470 W/cmmore » 2 to ensure fuel plate integrity during steady-state operation and after a loss-of-flow/loss-of-pressure accident. A feasibility study for the conversion of the BR2 reactor from highly-enriched uranium (HEU) to low-enriched uranium (LEU) fuel was previously performed to verify it can operate safely at the same maximum nominal steady-state heat flux. An assessment was also performed to quantify the heat fluxes at which the onset of flow instability and critical heat flux occur for each fuel type. This document updates and expands these results for the current representative core configuration (assuming a fresh beryllium matrix) by evaluating the onset of nucleate boiling (ONB), onset of fully developed nucleate boiling (FDNB), onset of flow instability (OFI) and critical heat flux (CHF).« less

Enhancement of Boiling Heat Transfer in Di-Electric Fluids

DTIC Science & Technology

1991-09-01

working fluid of R-I13. Maddox and Mudawar [Ref. 8] studied the effect of subcooling and surface aug- mentation on values of Critical Heat Flux (CHF). They...Enhanced Surfaces to Dielectric Fluids," A SME Journal of Heat Transfer, v.104, pp.292-299, May 1982. 8. Maddox D.E., and Mudawar ,I., "Single and Two

DOE Office of Scientific and Technical Information (OSTI.GOV)

LeJemtel, T.H.; Scortichini, D.; Katz, S.

In patients with chronic congestive heart failure (CHF), skeletal muscle blood flow can be measured directly by the continuous thermodilution technique and by the xenon-133 clearance method. The continuous thermodilution technique requires retrograde catheterization of the femoral vein and, thus, cannot be repeated conveniently in patients during evaluation of pharmacologic interventions. The xenon-133 clearance, which requires only an intramuscular injection, allows repeated determination of skeletal muscle blood flow. In patients with severe CHF, a fixed capacity of the skeletal muscle vasculature to dilate appears to limit maximal exercise performance. Moreover, the changes in peak skeletal muscle blood flow noted duringmore » long-term administration of captopril, an angiotensin-converting enzyme inhibitor, appears to correlate with the changes in aerobic capacity. In patients with CHF, resting supine deep femoral vein oxygen content can be used as an indirect measurement of resting skeletal muscle blood flow. The absence of a steady state complicates the determination of peak skeletal muscle blood flow reached during graded bicycle or treadmill exercise in patients with chronic CHF. Indirect assessments of skeletal muscle blood flow and metabolism during exercise performed at submaximal work loads are currently developed in patients with chronic CHF.« less

A comparison of critical heat flux in tubes and bilaterally heated annuli

DOE Office of Scientific and Technical Information (OSTI.GOV)

Doerffer, S.; Groeneveld, D.C.; Cheng, S.C.

1995-09-01

This paper examines the critical heat flux (CHF) behaviour for annular flow in bilaterally heated annuli and compares it to that in tubes and unilaterally heated annuli. It was found that the differences in CHF between bilaterally and unilaterally heated annuli or tubes strongly depend on pressure and quality. the CHF in bilaterally heated annuli can be predicted by tube CHF prediction methods for the simultaneous CHF occurrence at both surfaces, and the following flow conditions: pressure 7-10 MPa, mass flux 0.5-4.0 Mg/m{sup 2}s and critical quality 0.23-0.9. The effect on CHF of the outer-to-inner surface heat flux ratio, wasmore » also examined. The prediction of CHF for bilaterally heated annuli was based on the droplet-diffusion model proposed by Kirillov and Smogalev. While their model refers only to CHF occurrence at the inner surface, we extended it to cases where CHF occurs at the outer surface, and simultaneously at both surfaces, thus covering all cases of CHF occurrence in bilaterally heated annuli. From the annuli CHF data of Becker and Letzter, we derived empirical functions required by the model. the proposed equations provide good accuracy for the CHF data used in this study. Moreover, the equations can predict conditions at which CHF occurs simultaneously at both surfaces. Also, this method can be used for cases with only one heated surface.« less

CHF considerations for highly moderated 100% MOX fuels PWRs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saphier, D.; Raymond, P.

1995-09-01

A feasibility study on using 100% MOX fuel in a PWR with increased moderating ratio, RMA, was initiated. In the proposed design all the parameters were chosen identical to the French 1450MW PWR, except the fuel pin diameter which was reduced to achieve higher moderating ratios, V{sub M}/V{sub F}, where V{sub M} and V{sub F} are the moderator and fuel volume respectively. Moderating ratios from 2 to 4 were considered. In the present study the thermal-hydraulic feasibility of using fuel assemblies with smaller diameter fuel pins was investigated. The major design constrain in this study was the critical heat fluxmore » (CHF). In order to maintain the fuel pin integrity under nominal operating and transient conditions, the minimum DNBR, (Departure from Nucleate Boiling Ratio given by CHF/q{close_quotes}{sub local}, where q{close_quotes}{sub local} is the local heat flux), has to be above a given value. The limitations of the existing CHF correlations for the present study are outlined. Two designs based on the conventional 17x17 fuel assembly and on the advanced 19x19 assembly meeting the MDNBR criteria and satisfying the control margin requirements, are proposed.« less

Experimental investigation of nucleate pool boiling characteristics of high concentrated alumina/water nanofluids

NASA Astrophysics Data System (ADS)

Kshirsagar, Jagdeep M.; Shrivastava, Ramakant

2018-06-01

In Present study, the critical heat flux (CHF) and boiling heat transfer coefficient of alumina nanoparticles with the base fluid as deionised water is measured. The selected concentrations of nanofluids for the experimentation are from 0.3, 0.6, 0.9, 1.2 and 1.5 wt%. The main objective to select higher concentration is that to study the surface morphology of heater surface at higher concentrations and its effect on critical heat flux and heat transfer coefficient. It is observed that the critical heat flux enhancement rate decreases as concentration increases and surface roughness of heater surface decreases after 1.2 wt% concentration of nanofluids.

Exercise training attenuates chemoreflex-mediated reductions of renal blood flow in heart failure

PubMed Central

Pügge, Carolin; Mediratta, Jai; Schiller, Alicia M.; Del Rio, Rodrigo; Zucker, Irving H.; Schultz, Harold D.

2015-01-01

In chronic heart failure (CHF), carotid body chemoreceptor (CBC) activity is increased and contributes to increased tonic and hypoxia-evoked elevation in renal sympathetic nerve activity (RSNA). Elevated RSNA and reduced renal perfusion may contribute to development of the cardio-renal syndrome in CHF. Exercise training (EXT) has been shown to abrogate CBC-mediated increases in RSNA in experimental heart failure; however, the effect of EXT on CBC control of renal blood flow (RBF) is undetermined. We hypothesized that CBCs contribute to tonic reductions in RBF in CHF, that stimulation of the CBC with hypoxia would result in exaggerated reductions in RBF, and that these responses would be attenuated with EXT. RBF was measured in CHF-sedentary (SED), CHF-EXT, CHF-carotid body denervation (CBD), and CHF-renal denervation (RDNX) groups. We measured RBF at rest and in response to hypoxia (FiO2 10%). All animals exhibited similar reductions in ejection fraction and fractional shortening as well as increases in ventricular systolic and diastolic volumes. Resting RBF was lower in CHF-SED (29 ± 2 ml/min) than in CHF-EXT animals (46 ± 2 ml/min, P < 0.05) or in CHF-CBD animals (42 ± 6 ml/min, P < 0.05). In CHF-SED, RBF decreased during hypoxia, and this was prevented in CHF-EXT animals. Both CBD and RDNX abolished the RBF response to hypoxia in CHF. Mean arterial pressure increased in response to hypoxia in CHF-SED, but was prevented by EXT, CBD, and RDNX. EXT is effective in attenuating chemoreflex-mediated tonic and hypoxia-evoked reductions in RBF in CHF. PMID:26001414

Exercise training attenuates chemoreflex-mediated reductions of renal blood flow in heart failure.

PubMed

Marcus, Noah J; Pügge, Carolin; Mediratta, Jai; Schiller, Alicia M; Del Rio, Rodrigo; Zucker, Irving H; Schultz, Harold D

2015-07-15

In chronic heart failure (CHF), carotid body chemoreceptor (CBC) activity is increased and contributes to increased tonic and hypoxia-evoked elevation in renal sympathetic nerve activity (RSNA). Elevated RSNA and reduced renal perfusion may contribute to development of the cardio-renal syndrome in CHF. Exercise training (EXT) has been shown to abrogate CBC-mediated increases in RSNA in experimental heart failure; however, the effect of EXT on CBC control of renal blood flow (RBF) is undetermined. We hypothesized that CBCs contribute to tonic reductions in RBF in CHF, that stimulation of the CBC with hypoxia would result in exaggerated reductions in RBF, and that these responses would be attenuated with EXT. RBF was measured in CHF-sedentary (SED), CHF-EXT, CHF-carotid body denervation (CBD), and CHF-renal denervation (RDNX) groups. We measured RBF at rest and in response to hypoxia (FiO2 10%). All animals exhibited similar reductions in ejection fraction and fractional shortening as well as increases in ventricular systolic and diastolic volumes. Resting RBF was lower in CHF-SED (29 ± 2 ml/min) than in CHF-EXT animals (46 ± 2 ml/min, P < 0.05) or in CHF-CBD animals (42 ± 6 ml/min, P < 0.05). In CHF-SED, RBF decreased during hypoxia, and this was prevented in CHF-EXT animals. Both CBD and RDNX abolished the RBF response to hypoxia in CHF. Mean arterial pressure increased in response to hypoxia in CHF-SED, but was prevented by EXT, CBD, and RDNX. EXT is effective in attenuating chemoreflex-mediated tonic and hypoxia-evoked reductions in RBF in CHF. Copyright © 2015 the American Physiological Society.

Chronic heart failure does not attenuate the total activity of sympathetic outflow to skin during whole-body heating.

PubMed

Cui, Jian; Boehmer, John P; Blaha, Cheryl; Lucking, Robert; Kunselman, Allen R; Sinoway, Lawrence I

2013-03-01

Previous studies show that the rise in skin blood flow and cutaneous vascular conductance during heat stress is substantially attenuated in chronic heart failure (CHF) patients. The mechanisms responsible for this finding are not clear. In particular, little is known regarding the responses of skin sympathetic nerve activity (SSNA) that control the skin blood flow during heat stress in CHF patients. We examined the effects of a modest heat stress to test the hypothesis that SSNA responses could be attenuated in CHF. We assessed SSNA (microneurography) from the peroneal nerve and skin blood flow (forearm laser Doppler) in 9 patients with stable class II-III CHF and in matched healthy subjects during passive whole-body heating with a water-perfused suit. Whole-body heating induced similar increases in internal temperature (≈0.6 °C) in both groups. Whole-body heat stress evoked similar SSNA activation in CHF patients (Δ891±110 U/min) and the control subjects (Δ787±84 U/min; P=0.66), whereas the elevation in forearm cutaneous vascular conductance in patients with CHF was significantly lower than that in healthy control subjects (Δ131±29% vs. Δ623±131%; P=0.001). The present data show that SSNA activation during a modest whole-body heat stress is not attenuated in CHF. Thus, the attenuated skin vasodilator response in CHF patients is not attributable to a reduction in total activity of sympathetic outflow to skin.

Frequency response of the renal vasculature in congestive heart failure.

PubMed

DiBona, Gerald F; Sawin, Linda L

2003-04-29

The renal vasoconstrictor response to renal nerve stimulation is greater in congestive heart failure (CHF) rats than in control rats. This study tested the hypothesis that the enhanced renal vasoconstrictor response to renal nerve stimulation in CHF is a result of an impairment in the low-pass filter function of the renal vasculature. In response to conventional graded-frequency renal nerve stimulation, the reductions in renal blood flow at each stimulation frequency were greater in CHF rats than control rats. A pseudorandom binary sequence pattern of renal nerve stimulation was used to examine the frequency response of the renal vasculature. Although this did not affect the renal blood flow power spectrum in control rats, there was a 10-fold increase in renal blood flow power over the frequency range of 0.01 to 1.0 Hz in CHF rats. On analysis of transfer function gain, attenuation of the renal nerve stimulation input signal was similar in control and CHF rats over the frequency range of 0.001 to 0.1 Hz. However, over the frequency range of 0.1 to 1.0 Hz, although there was progressive attenuation of the input signal (-30 to -70 dB) in control rats, CHF rats exhibited a flat gain response (-20 dB) without progressive attenuation. The enhanced renal vasoconstrictor response to renal nerve stimulation in CHF rats is caused by an alteration in the low-pass filter function of the renal vasculature, resulting in a greater transfer of input signals into renal blood flow in the 0.1 to 1.0 Hz range.

Predictions of Critical Heat Flux in Annular Pipes with TRACEv4.160 code

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jasiulevicius, Audrius; Macian-Juan, Rafael

2006-07-01

This paper presents the assessment of TRACE (version v4.160) against the Critical Heat Flux (CHF) experiments in annular tubes performed at the Royal Institute of Technology (KTH) in Stockholm, Sweden. The experimental database includes data for coolant mass fluxes between 250 and 2500 kg/m{sup 2}s and inlet subcooling of 10 and 40 K at a pressure of 70 bar. The work presented in this paper supplements the calculations of single round tube experiments carried out earlier and provides a broader scope of validated geometries. In addition to the Biasi and CISE-GE CHF correlations available in the code, a number ofmore » experimental points at low flow conditions are available for the annular geometry experiments, which also permitted the assessment of the Biasi/Zuber CHF correlation used in TRACE v4.160 for low flow conditions. Experiments with different axial power distribution were simulated and the effects of the axial power profile and the coolant inlet subcooling on the TRACE predictions were investigated. The results of this work show that the Biasi/Zuber correlation provides good estimation of the CHF at 70 bar, and, for the same conditions, the simulation of the annular experiments resulted in the calculation of lower CHF values compared to single-tube experiments. The analysis of the performance of the standard TRACE CHF correlations shows that the CISE-GE correlation yields critical qualities (quality at CHF) closer to the experimental values at 70 bar than the Biasi correlation for annular flow conditions. Regarding the power profile, the results of the TRACE calculations seem to be very sensitive to its shape, since, depending on the profile, different accuracies in the predictions were noted while other system conditions remained constant. The inlet coolant subcooling was also an important factor in the accuracy of TRACE CHF predictions. Thus, an increase in the inlet subcooling led to a clear improvement in the estimation of the critical quality with both Biasi and CISE-GE correlations. To complement the work, three additional CHF correlations were implemented in TRACE v4.160, namely the Bowring, Tong W-3 and Levitan-Lantsman CHF models, in order to assess the applicability of these correlations to simulate the CHF in annular tubes. The improvement of CHF predictions for low coolant mass flows (up to 1500 kg/m{sup 2}s) is noted when applying Bowring CHF correlation. However, the increase in the inlet subcooling increases the error in predicted critical quality with the Bowring correlation. The Levitan-Lantsman and Tong-W-3 correlations provide results similar to the Biasi model. Therefore, the most correct CHF predictions among the investigated correlations were obtained using CISE-GE model in the standard TRAC v4.160 code. (authors)« less

An experimental investigation of liquid methane convection and boiling in rocket engine cooling channels

NASA Astrophysics Data System (ADS)

Trujillo, Abraham Gerardo

In the past decades, interest in developing hydrocarbon-fueled rocket engines for deep spaceflight missions has continued to grow. In particular, liquid methane (LCH4) has been of interest due to the weight efficiency, storage, and handling advantages it offers over several currently used propellants. Deep space exploration requires reusable, long life rocket engines. Due to the high temperatures reached during combustion, the life of an engine is significantly impacted by the cooling system's efficiency. Regenerative (regen) cooling is presented as a viable alternative to common cooling methods such as film and dump cooling since it provides improved engine efficiency. Due to limited availability of experimental sub-critical liquid methane cooling data for regen engine design, there has been an interest in studying the heat transfer characteristics of the propellant. For this reason, recent experimental studies at the Center for Space Exploration Technology Research (cSETR) at the University of Texas at El Paso (UTEP) have focused on investigating the heat transfer characteristics of sub-critical CH4 flowing through sub-scale cooling channels. To conduct the experiments, the csETR developed a High Heat Flux Test Facility (HHFTF) where all the channels are heated using a conduction-based thermal concentrator. In this study, two smooth channels with cross sectional geometries of 1.8 mm x 4.1 mm and 3.2 mm x 3.2 mm were tested. In addition, three roughened channels all with a 3.2 mm x 3.2 mm square cross section were also tested. For the rectangular smooth channel, Reynolds numbers ranged between 68,000 and 131,000, while the Nusselt numbers were between 40 and 325. For the rough channels, Reynolds numbers ranged from 82,000 to 131,000, and Nusselt numbers were between 65 and 810. Sub-cooled film-boiling phenomena were confirmed for all the channels presented in this work. Film-boiling onset at Critical Heat Flux (CHF) was correlated to a Boiling Number (Bo) of approximately 0.1 for all channels. Convective Nusselt number follows predicted trends for Reynolds number with a wall temperature correction for both the boiling and non-boiling regimes.

Study of the heat-transfer crisis on heat-release surfaces of annular channels with swirl and transit flows

NASA Astrophysics Data System (ADS)

Boltenko, E. A.

2016-10-01

The results of the experimental study of the heat-transfer crisis on heat-release surfaces of annular channels with swirl and transit flow are presented. The experiments were carried out using electric heated annular channels with one and (or) two heat-release surfaces. For the organization of transit flow on a convex heat-release surface, four longitudinal ribs were installed uniformly at its perimeter. Swirl flow was realized using a capillary wound tightly (without gaps) on the ribs. The ratio between swirl and transit flows in the annular gap was varied by applying longitudinal ribs of different height. The experiments were carried out using a closed-type circulatory system. The experimental data were obtained in a wide range of regime parameters. Both water heated to the temperature less than the saturation temperature and water-steam mixture were fed at the inlet of the channels. For the measurement of the temperature of the heat-release surfaces, chromel-copel thermocouples were used. It was shown that the presence of swirl flow on a convex heatrelease surface led to a significant decrease in critical heat flows (CHF) compared to a smooth surface. To increase CHF, it was proposed to use the interaction of swirl flows of the heat carrier. The second swirl flow was transit flow, i.e., swirl flow with the step equal to infinity. It was shown that CHF values for a channel with swirl and transit flow in all the studied range of regime parameters was higher than CHF values for both a smooth annular channel and a channel with swirl. The empirical ratios describing the dependence of CHF on convex and concave heat-release surfaces of annular channels with swirl and transit flow on the geometrical characteristics of channels and the regime parameters were obtained. The experiments were carried out at the pressure p = 3.0-16.0 MPa and the mass velocity ρw = 250-3000 kg/(m2s).

Development of an Efficient Meso- scale Multi-phase Flow Solver in Nuclear Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Taehun

2015-10-20

The proposed research aims at formulating a predictive high-order Lattice Boltzmann Equation for multi-phase flows relevant to nuclear energy related application - namely, saturated and sub-cooled boiling in reactors, and liquid- liquid mixing and extraction for fuel cycle separation. An efficient flow solver will be developed based on the Finite Element based Lattice Boltzmann Method (FE- LBM), accounting for phase-change heat transfer and capable of treating multiple phases over length scales from the submicron to the meter. A thermal LBM will be developed in order to handle adjustable Prandtl number, arbitrary specific heat ratio, a wide range of temperature variations,more » better numerical stability during liquid-vapor phase change, and full thermo-hydrodynamic consistency. Two-phase FE-LBM will be extended to liquid–liquid–gas multi-phase flows for application to high-fidelity simulations building up from the meso-scale up to the equipment sub-component scale. While several relevant applications exist, the initial applications for demonstration of the efficient methods to be developed as part of this project include numerical investigations of Critical Heat Flux (CHF) phenomena in nuclear reactor fuel bundles, and liquid-liquid mixing and interfacial area generation for liquid-liquid separations. In addition, targeted experiments will be conducted for validation of this advanced multi-phase model.« less

Boiling Visualization and Critical Heat Flux Phenomena In Narrow Rectangular Gap

DOE Office of Scientific and Technical Information (OSTI.GOV)

J. J. Kim; Y. H. Kim; S. J. Kim

2004-12-01

An experimental study was performed to investifate the pool boling critical hear flux (CHF) on one-dimensional inclined rectangular channels with narrow gaps by changing the orientation of a copper test heater assembly. In a pool of saturated water at atmospheric pressure, the test parameters include the gap sizes of 1,2,5, and 10 mm, andthe surface orientation angles from the downward facing position (180 degrees) to the vertical position (90 degress) respectively.

An experimental investigation on liquid methane heat transfer enhancement through the use of longitudinal fins in cooling channels

NASA Astrophysics Data System (ADS)

Galvan, Manuel de Jesus

In the past years, hydrocarbon fuels have been the focus of attention as the interest in developing reusable, high-performing liquid rocket engines has grown. Liquid methane (LCH4) has been of particular interest because of the cost, handling, and storage advantages that it presents when compared to currently used propellants. Deep space exploration requires thrusters that can operate reliably during long-duration missions. One of the challenges in the development of a reliable engine has been providing adequate combustion chamber cooling to prevent engine failure. Regenerative (regen) cooling has presented itself as an appealing option because it provides improved cooling and engine efficiency over other types of cooling, such as film or dump cooling. Due to limited availability of experimental sub-critical liquid methane cooling data for pressure-fed regen engine design, there has been an interest in studying the heat transfer characteristics of the propellant. For this reason, recent experimental studies at the Center for Space Exploration Technology Research (cSETR) at the University of Texas at El Paso (UTEP) have focused on investigating the heat transfer characteristics of sub-critical CH4 flowing through smooth sub-scale cooling channels. In addition to investigating smooth channels, the cSETR has conducted experiments to investigate the effects of internal longitudinal fins on the heat transfer of methane. To conduct the experiments, the cSETR developed a conduction-based thermal concentrator known as the High Heat Flux Test Facility (HHFTF) in which the channels are heated. In this study, a smooth channel and three channels with longitudinal fins all with cross sectional geometries of 3.2 mm x 3.2 mm were tested. The Nusselt numbers ranged from 70 and 510, and Reynolds numbers were between 50,000 and 128,000. Sub-cooled film-boiling phenomena were discovered in the data pertaining to the smooth and two finned channels. Sub-cooled film-boiling was not observed in the channel that had the fins with the highest height. Film-boiling onset at Critical Heat Flux (CHF) was correlated to a Boiling Number (Bo) of approximately 0.1 for the channels studies. Convective Nusselt number follows predicted trends for Reynolds number with a wall temperature correction factor for both the boiling and non-boiling regimes.

Synchrotron x-ray imaging visualization study of capillary-induced flow and critical heat flux on surfaces with engineered micropillars

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, Dong In; Kwak, Ho Jae; Noh, Hyunwoo

Over the past several decades, phenomena related to critical heat flux (CHF) on structured surfaces have received a large amount of attention from the research community. The purpose of such research has been to enhance the safety and efficiency of a variety of thermal systems. A number of theories have been put forward to explain the key CHF enhancement mechanisms on structured surfaces. However, these theories have not been confirmed experimentally due to limitations in the available visualization techniques and the complexity of the phenomena. To overcome the limitations of the previous visualization techniques and elucidate the CHF enhancement mechanismmore » on the structured surfaces, we introduce synchrotron X-ray imaging with high spatial (~2 μm) and time (~20,000 Hz) resolutions. Lastly, this technique has enabled us to confirm that capillary-induced flow is the key CHF enhancement mechanism on structured surfaces.« less

Synchrotron x-ray imaging visualization study of capillary-induced flow and critical heat flux on surfaces with engineered micropillars

DOE PAGES

Yu, Dong In; Kwak, Ho Jae; Noh, Hyunwoo; ...

2018-02-23

Over the past several decades, phenomena related to critical heat flux (CHF) on structured surfaces have received a large amount of attention from the research community. The purpose of such research has been to enhance the safety and efficiency of a variety of thermal systems. A number of theories have been put forward to explain the key CHF enhancement mechanisms on structured surfaces. However, these theories have not been confirmed experimentally due to limitations in the available visualization techniques and the complexity of the phenomena. To overcome the limitations of the previous visualization techniques and elucidate the CHF enhancement mechanismmore » on the structured surfaces, we introduce synchrotron X-ray imaging with high spatial (~2 μm) and time (~20,000 Hz) resolutions. Lastly, this technique has enabled us to confirm that capillary-induced flow is the key CHF enhancement mechanism on structured surfaces.« less

Boiling incipience and convective boiling of neon and nitrogen

NASA Technical Reports Server (NTRS)

Papell, S. S.; Hendricks, R. C.

1977-01-01

Forced convection and subcooled boiling heat transfer data for liquid nitrogen and liquid neon were obtained in support of a design study for a 30 tesla cryomagnet cooled by forced convection of liquid neon. This design precludes nucleate boiling in the flow channels as they are too small to handle vapor flow. Consequently, it was necessary to determine boiling incipience under the operating conditions of the magnet system. The cryogen data obtained over a range of system pressures, fluid flow rates, and applied heat fluxes were used to develop correlations for predicting boiling incipience and convective boiling heat transfer coefficients in uniformly heated flow channels. The accuracy of the correlating equations was then evaluated. A technique was also developed to calculate the position of boiling incipience in a uniformly heated flow channel. Comparisons made with the experimental data showed a prediction accuracy of plus or minus 15 percent

Exercise training normalizes renal blood flow responses to acute hypoxia in experimental heart failure: role of the α1-adrenergic receptor.

PubMed

Pügge, Carolin; Mediratta, Jai; Marcus, Noah J; Schultz, Harold D; Schiller, Alicia M; Zucker, Irving H

2016-02-01

Recent data suggest that exercise training (ExT) is beneficial in chronic heart failure (CHF) because it improves autonomic and peripheral vascular function. In this study, we hypothesized that ExT in the CHF state ameliorates the renal vasoconstrictor responses to hypoxia and that this beneficial effect is mediated by changes in α1-adrenergic receptor activation. CHF was induced in rabbits. Renal blood flow (RBF) and renal vascular conductance (RVC) responses to 6 min of 5% isocapnic hypoxia were assessed in the conscious state in sedentary (SED) and ExT rabbits with CHF with and without α1-adrenergic blockade. α1-adrenergic receptor expression in the kidney cortex was also evaluated. A significant decline in baseline RBF and RVC and an exaggerated renal vasoconstriction during acute hypoxia occurred in CHF-SED rabbits compared with the prepaced state (P < 0.05). ExT diminished the decline in baseline RBF and RVC and restored changes during hypoxia to those of the prepaced state. α1-adrenergic blockade partially prevented the decline in RBF and RVC in CHF-SED rabbits and eliminated the differences in hypoxia responses between SED and ExT animals. Unilateral renal denervation (DnX) blocked the hypoxia-induced renal vasoconstriction in CHF-SED rabbits. α1-adrenergic protein in the renal cortex of animals with CHF was increased in SED animals and normalized after ExT. These data provide evidence that the acute decline in RBF during hypoxia is caused entirely by the renal nerves but is only partially mediated by α1-adrenergic receptors. Nonetheless, α1-adrenergic receptors play an important role in the beneficial effects of ExT in the kidney. Copyright © 2016 the American Physiological Society.

Transport Phenomena in Fluid Dynamics: Matrix Heat Exchangers and Their Applications in Energy Systems

DTIC Science & Technology

2009-07-01

presented a summary of recent research on boiling in microchannels . He addressed the topics of macro scale versus micro scale heat transfer , two phase...flow regime, flow boiling 14 heat transfer results for microchannels , heat transfer mechanisms in microchannels , and flow boiling models for... Heat Transfer Boiling In Minichannel And Microchannel Flow Passages Of Compact Evaporators, Keynote Lecture Presented at the Engineering Foundation

Ryanodine Receptor Calcium Leak in Circulating B-Lymphocytes as a Biomarker in Heart Failure.

PubMed

Kushnir, Alexander; Santulli, Gaetano; Reiken, Steven R; Coromilas, Ellie; Godfrey, Sarah J; Brunjes, Danielle L; Colombo, Paolo C; Yuzefpolskaya, Melana; Sokol, Seth I; Kitsis, Richard N; Marks, Andrew R

2018-03-28

Background -Advances in congestive heart failure (CHF) management depend on biomarkers for monitoring disease progression and therapeutic response. During systole, intracellular Ca2 + is released from the sarcoplasmic reticulum (SR) into the cytoplasm through type 2 ryanodine receptor/Ca2 + release channels (RyR2). In CHF, chronically elevated circulating catecholamine levels cause pathologic remodeling of RyR2 resulting in diastolic SR Ca2 + leak, and decreased myocardial contractility. Similarly, skeletal muscle contraction requires SR Ca2 + release through type-1 ryanodine receptors (RyR1), and chronically elevated catecholamine levels in CHF cause RyR1 mediated SR Ca2 + leak, contributing to myopathy and weakness. Circulating B-lymphocytes express RyR1 and catecholamine responsive signaling cascades, making them a potential surrogate for defects in intracellular Ca2 + handling due to leaky RyR channels in CHF. Methods -Whole blood was collected from patients with CHF, CHF status-post left-ventricular assist devices (LVAD), and controls. Blood was also collected from mice with ischemic CHF, ischemic CHF + S107 (a drug that specifically reduces RyR channel Ca2 + leak), and WT controls. Channel macromolecular complex was assessed by immunostaining RyR1 immunoprecipitated from lymphocyte enriched preparations. RyR1 Ca2 + leak was assessed using flow cytometry to measure Ca2 + fluorescence in B-lymphocytes, in the absence and presence of RyR1 agonists that empty RyR1 Ca2 + stores within the endoplasmic reticulum (ER). Results -Circulating B-lymphocytes from humans and mice with CHF exhibited remodeled RyR1 and decreased ER Ca2 + stores, consistent with chronic intracellular Ca2 + leak. This Ca2 + leak correlated with circulating catecholamine levels. The intracellular Ca2 + leak was significantly reduced in mice treated with the Rycal S107. CHF patients treated with LVAD exhibited a heterogeneous response. Conclusions -In CHF, B-lymphocytes exhibit remodeled leaky RyR1 channels and decreased ER Ca2 + stores consistent with chronic intracellular Ca2 + leak. RyR1 mediated Ca2 + leak in B-lymphocytes assessed using flow cytometry provides a surrogate measure of intracellular Ca2 + handling and systemic sympathetic burden, presenting a novel biomarker for monitoring response to pharmacologic and mechanical CHF therapy.

Plasma atrial natriuretic peptide and N-terminal pro B-type natriuretic peptide concentrations in dogs with right-sided congestive heart failure

PubMed Central

KANNO, Nobuyuki; HORI, Yasutomo; HIDAKA, Yuichi; CHIKAZAWA, Seishiro; KANAI, Kazutaka; HOSHI, Fumio; ITOH, Naoyuki

2015-01-01

The clinical utility of plasma natriuretic peptide concentrations in dogs with right-sided congestive heart failure (CHF) remains unclear. We investigated whether plasma levels of atrial natriuretic peptide (ANP) and N-terminal pro B-type natriuretic peptide (NT-proBNP) are useful for assessing the congestive signs of right-sided heart failure in dogs. This retrospective study enrolled 16 healthy dogs and 51 untreated dogs with presence (n=28) or absence (n=23) of right-sided CHF. Medical records of physical examinations, thoracic radiography and echocardiography were reviewed. The plasma concentration of canine ANP was measured with a chemiluminescent enzyme immunoassay. Plasma NT-proBNP concentrations were determined using an enzyme immunoassay. Plasma ANP and NT-proBNP concentrations in dogs with right-sided CHF were significantly higher than in healthy controls and those without right-sided CHF. The plasma NT-proBNP concentration >3,003 pmol/l used to identify right-sided CHF had a sensitivity of 88.5% and specificity of 90.3%. An area under the ROC curve (AUC) was 0.93. The AUC for NT-proBNP was significantly higher than the AUCs for the cardiothoracic ratio, vertebral heart score, ratio of right ventricular end-diastolic internal diameter to body surface area, tricuspid late diastolic flow and ratio of the velocities of tricuspid early to late diastolic flow. These results suggest that plasma ANP and NT-proBNP concentrations increase markedly in dogs with right-sided CHF. Particularly, NT-proBNP is simple and helpful biomarkers to assess the right-sided CHF. PMID:26607133

Evaluation of correlations of flow boiling heat transfer of R22 in horizontal channels.

PubMed

Zhou, Zhanru; Fang, Xiande; Li, Dingkun

2013-01-01

The calculation of two-phase flow boiling heat transfer of R22 in channels is required in a variety of applications, such as chemical process cooling systems, refrigeration, and air conditioning. A number of correlations for flow boiling heat transfer in channels have been proposed. This work evaluates the existing correlations for flow boiling heat transfer coefficient with 1669 experimental data points of flow boiling heat transfer of R22 collected from 18 published papers. The top two correlations for R22 are those of Liu and Winterton (1991) and Fang (2013), with the mean absolute deviation of 32.7% and 32.8%, respectively. More studies should be carried out to develop better ones. Effects of channel dimension and vapor quality on heat transfer are analyzed, and the results provide valuable information for further research in the correlation of two-phase flow boiling heat transfer of R22 in channels.

Evaluation of Correlations of Flow Boiling Heat Transfer of R22 in Horizontal Channels

PubMed Central

Fang, Xiande; Li, Dingkun

2013-01-01

The calculation of two-phase flow boiling heat transfer of R22 in channels is required in a variety of applications, such as chemical process cooling systems, refrigeration, and air conditioning. A number of correlations for flow boiling heat transfer in channels have been proposed. This work evaluates the existing correlations for flow boiling heat transfer coefficient with 1669 experimental data points of flow boiling heat transfer of R22 collected from 18 published papers. The top two correlations for R22 are those of Liu and Winterton (1991) and Fang (2013), with the mean absolute deviation of 32.7% and 32.8%, respectively. More studies should be carried out to develop better ones. Effects of channel dimension and vapor quality on heat transfer are analyzed, and the results provide valuable information for further research in the correlation of two-phase flow boiling heat transfer of R22 in channels. PMID:23956695

Capillary hydrodynamics and transport processes during phase change in microscale systems

NASA Astrophysics Data System (ADS)

Kuznetsov, V. V.

2017-09-01

The characteristics of two-phase gas-liquid flow and heat transfer during flow boiling and condensing in micro-scale heat exchangers are discussed in this paper. The results of numerical simulation of the evaporating liquid film flowing downward in rectangular minichannel of the two-phase compact heat exchanger are presented and the peculiarities of microscale heat transport in annular flow with phase changes are discussed. Presented model accounts the capillarity induced transverse flow of liquid and predicts the microscale heat transport processes when the nucleate boiling becomes suppressed. The simultaneous influence of the forced convection, nucleate boiling and liquid film evaporation during flow boiling in plate-fin heat exchangers is considered. The equation for prediction of the flow boiling heat transfer at low flux conditions is presented and verified using experimental data.

Dietary nitrate supplementation: impact on skeletal muscle vascular control in exercising rats with chronic heart failure

PubMed Central

Ferguson, Scott K.; Holdsworth, Clark T.; Colburn, Trenton D.; Wright, Jennifer L.; Craig, Jesse C.; Fees, Alex; Jones, Andrew M.; Allen, Jason D.; Musch, Timothy I.

2016-01-01

Chronic heart failure (CHF) results in central and peripheral derangements that ultimately reduce skeletal muscle O2 delivery and impair exercise tolerance. Dietary nitrate (NO3−) supplementation improves skeletal muscle vascular function and tolerance to exercise. We tested the hypothesis that NO3− supplementation would elevate exercising skeletal muscle blood flow (BF) and vascular conductance (VC) in CHF rats. Myocardial infarction (MI) was induced (coronary artery ligation) in young adult male rats. After 21 days of recovery, rats randomly received 5 days of NO3−-rich beetroot juice (CHF + BR, n = 10) or a placebo (CHF, n = 10). Mean arterial pressure (carotid artery catheter) and skeletal muscle BF (radiolabeled microspheres) were measured during treadmill exercise (20 m/min, 5% grade). CHF-induced dysfunction, as determined by myocardial infarction size (29 ± 3% and 33 ± 4% in CHF and CHF + BR, respectively) and left ventricular end-diastolic pressure (18 ± 2 and 18 ± 2 mmHg in CHF and CHF + BR, respectively), and exercising mean arterial pressure (131 ± 3 and 128 ± 4 mmHg in CHF and CHF + BR, respectively) were not different (P > 0.05) between groups. Total exercising hindlimb skeletal muscle BF (95 ± 5 and 116 ± 9 ml·min−1·100 g−1 in CHF and CHF + BR, respectively) and VC (0.75 ± 0.05 and 0.90 ± 0.05 ml·min−1·100 g−1·mmHg−1 in CHF and CHF + BR, respectively) were 22% and 20% greater in BR-supplemented rats, respectively (P < 0.05). During exercise, BF in 9 and VC in 10 hindlimb muscles and muscle portions were significantly greater in the CHF + BR group. These results provide strong evidence that dietary NO3− supplementation improves skeletal muscle vascular function during exercise in rats with CHF and, thus, support the use of BR as a novel therapeutic modality for the treatment of CHF. PMID:27445296

Dietary nitrate supplementation: impact on skeletal muscle vascular control in exercising rats with chronic heart failure.

PubMed

Ferguson, Scott K; Holdsworth, Clark T; Colburn, Trenton D; Wright, Jennifer L; Craig, Jesse C; Fees, Alex; Jones, Andrew M; Allen, Jason D; Musch, Timothy I; Poole, David C

2016-09-01

Chronic heart failure (CHF) results in central and peripheral derangements that ultimately reduce skeletal muscle O2 delivery and impair exercise tolerance. Dietary nitrate (NO3 (-)) supplementation improves skeletal muscle vascular function and tolerance to exercise. We tested the hypothesis that NO3 (-) supplementation would elevate exercising skeletal muscle blood flow (BF) and vascular conductance (VC) in CHF rats. Myocardial infarction (MI) was induced (coronary artery ligation) in young adult male rats. After 21 days of recovery, rats randomly received 5 days of NO3 (-)-rich beetroot juice (CHF + BR, n = 10) or a placebo (CHF, n = 10). Mean arterial pressure (carotid artery catheter) and skeletal muscle BF (radiolabeled microspheres) were measured during treadmill exercise (20 m/min, 5% grade). CHF-induced dysfunction, as determined by myocardial infarction size (29 ± 3% and 33 ± 4% in CHF and CHF + BR, respectively) and left ventricular end-diastolic pressure (18 ± 2 and 18 ± 2 mmHg in CHF and CHF + BR, respectively), and exercising mean arterial pressure (131 ± 3 and 128 ± 4 mmHg in CHF and CHF + BR, respectively) were not different (P > 0.05) between groups. Total exercising hindlimb skeletal muscle BF (95 ± 5 and 116 ± 9 ml·min(-1)·100 g(-1) in CHF and CHF + BR, respectively) and VC (0.75 ± 0.05 and 0.90 ± 0.05 ml·min(-1)·100 g(-1)·mmHg(-1) in CHF and CHF + BR, respectively) were 22% and 20% greater in BR-supplemented rats, respectively (P < 0.05). During exercise, BF in 9 and VC in 10 hindlimb muscles and muscle portions were significantly greater in the CHF + BR group. These results provide strong evidence that dietary NO3 (-) supplementation improves skeletal muscle vascular function during exercise in rats with CHF and, thus, support the use of BR as a novel therapeutic modality for the treatment of CHF. Copyright © 2016 the American Physiological Society.

Steady State Film Boiling Heat Transfer Simulated With Trace V4.160

DOE Office of Scientific and Technical Information (OSTI.GOV)

Audrius Jasiulevicius; Rafael Macian-Juan

2006-07-01

This paper presents the results of the assessment and analysis of TRACE v4.160 heat transfer predictions in the post-CHF (critical heat flux) region and discusses the possibilities to improve the TRACE v4.160 code predictions in the film boiling heat transfer when applying different film boiling correlations. For this purpose, the TRACE v4.160-calculated film boiling heat flux and the resulting maximum inner wall temperatures during film boiling in single tubes were compared with experimental data obtained at the Royal Institute of Technology (KTH) in Stockholm, Sweden. The experimental database included measurements for pressures ranging from 30 to 200 bar and coolantmore » mass fluxes from 500 to 3000 kg/m{sup 2}s. It was found that TRACE v4.160 does not produce correct predictions of the film boiling heat flux, and consequently of the maximum inner wall temperature in the test section, under the wide range of conditions documented in the KTH experiments. In particular, it was found that the standard TRACE v4.160 under-predicts the film boiling heat transfer coefficient at low pressure-low mass flux and high pressure-high mass flux conditions. For most of the rest of the investigated range of parameters, TRACE v4.160 over-predicts the film boiling heat transfer coefficient, which can lead to non-conservative predictions in applications to nuclear power plant analyses. Since no satisfactory agreement with the experimental database was obtained with the standard TRACE v4.160 film boiling heat transfer correlations, we have added seven film boiling correlations to TRACE v4.160 in order to investigate the possibility to improve the code predictions for the conditions similar to the KTH tests. The film boiling correlations were selected among the most commonly used film boiling correlations found in the open literature, namely Groeneveld 5.7, Bishop (2 correlations), Tong, Konkov, Miropolskii and Groeneveld-Delorme correlations. The only correlation among the investigated, which resulted in a significant improvement of TRACE predictions, was the Groeneveld 5.7. It was found, that replacing the current film boiling correlation (Dougall-Rohsenow) for the wall-togas heat transfer with Groeneveld 5.7 improves the code predictions for the film boiling heat transfer at high qualities in single tubes in the entire range of pressure and coolant mass flux considered. (authors)« less

Transition process leading to microbubble emission boiling on horizontal circular heated surface in subcooled pool

NASA Astrophysics Data System (ADS)

Ueno, Ichiro; Ando, Jun; Horiuchi, Kazuna; Saiki, Takahito; Kaneko, Toshihiro

2016-11-01

Microbubble emission boiling (MEB) produces a higher heat flux than critical heat flux (CHF) and therefore has been investigated in terms of its heat transfer characteristics as well as the conditions under which MEB occurs. Its physical mechanism, however, is not yet clearly understood. We carried out a series of experiments to examine boiling on horizontal circular heated surfaces of 5 mm and of 10 mm in diameter, in a subcooled pool, paying close attention to the transition process to MEB. High-speed observation results show that, in the MEB regime, the growth, condensation, and collapse of the vapor bubbles occur within a very short time. In addition, a number of fine bubbles are emitted from the collapse of the vapor bubbles. By tracking these tiny bubbles, we clearly visualize that the collapse of the vapor bubbles drives the liquid near the bubbles towards the heated surface, such that the convection field around the vapor bubbles under MEB significantly differs from that under nucleate boiling. Moreover, the axial temperature gradient in a heated block (quasi-heat flux) indicates a clear difference between nucleate boiling and MEB. A combination of quasi-heat flux and the measurement of the behavior of the vapor bubbles allows us to discuss the transition to MEB. This work was financially supported by the 45th Research Grant in Natural Sciences from The Mitsubishi Foundation (2014 - 2015), and by Research Grant for Boiler and Pressurized Vessels from The Japan Boiler Association (2016).

Forced convection flow boiling and two-phase flow phenomena in a microchannel

NASA Astrophysics Data System (ADS)

Na, Yun Whan

2008-07-01

The present study was performed to numerically analyze the evaporation phenomena through the liquid-vapor interface and to investigate bubble dynamics and heat transfer behavior during forced convective flow boiling in a microchannel. Flow instabilities of two-phase flow boiling in a microchannel were studied as well. The main objective of this research is to investigate the fundamental mechanisms of two-phase flow boiling in a microchannel and provide predictive tools to design thermal management systems, for example, microchannel heat sinks. The numerical results obtained from this study were qualitatively and quantitatively compared with experimental results in the open literature. Physical and mathematical models, accounting for evaporating phenomena through the liquid-vapor interface in a microchannel at constant heat flux and constant wall temperature, have been developed, respectively. The heat transfer mechanism is affected by the dominant heat conduction through the thin liquid film and vaporization at the liquid-vapor interface. The thickness of the liquid film and the pressure of the liquid and vapor phases were simultaneously solved by the governing differential equations. The developed semi-analytical evaporation model that takes into account of the interfacial phenomena and surface tension effects was used to obtain solutions numerically using the fourth-order Runge-Kutta method. The effects of heat flux 19 and wall temperature on the liquid film were evaluated. The obtained pressure drops in a microchannel were qualitatively consistent with the experimental results of Qu and Mudawar (2004). Forced convective flow boiling in a single microchannel with different channel heights was studied through a numerical simulation to investigate bubble dynamics, flow patterns, and heat transfer. The momentum and energy equations were solved using the finite volume method while the liquid-vapor interface of a bubble is captured using the VOF (Volume of Fluid) technique. The effects of different constant heat fluxes and different channel heights on the boiling mechanisms were investigated. The effects of liquid velocity on the bubble departure diameter were analyzed. The obtained results showed that the wall superheats at the position of nucleate boiling are relatively independent of the mass flow rates at the same channel height. The obtained results, however, showed that the heat flux at the onset of nucleate boiling strongly depends on the channel height. With a decrease of the channel height and an increase of the liquid velocity at the channel inlet, the departure diameter of a bubble was smaller. The periodic flow patterns, such as the bubbly flow, elongated slug flow, and churn flow were observed in the microchannel. Flow instabilities of two-phase flow boiling in a trapezoidal microchannel using a three-dimensional model were investigated. Fluctuation behaviors of flow boiling parameters such as wall temperature and inlet pressure caused by periodic flow patterns were studied at different heat fluxes and mass fluxes. The numerical results showed large amplitude and short period oscillations for wall temperature and inlet pressure fluctuations. Stable and unstable flow boiling regime with short period oscillations were investigated. Those flow boiling regimes were not listed in stable and unstable boiling regime map proposed by Wang et al. (2007).

On the pulse boiling frequency in thermosyphons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, J.F.; Wang, J.C.Y.

1992-02-01

The unsteady periodic boiling phenomenon, pulse boiling, appearing in the evaporator of thermosyphons has been mentioned and investigated by many researchers. The heat transfer coefficient in evaporators was predicted according to different considerations of flow patterns. For instance, Shiraishi et al. proposed a method based on a combination flow pattern: the nucleate boiling in a liquid pool and the evaporation from a falling condensate film. Liu et al. only considered a pure pulse boiling flow pattern, and Xin et al. focused on the flow pattern of the continuous boiling process without pulse phenomenon. Besides, the forming conditions of pulse boilingmore » were also described differently. Xin et al. also reported that pulse boiling cannot occur in a carbon-steel/water heat pipe; Ma et al., however, observed this phenomenon in a carbon-steel/water thermosyphon. Nearly all researchers mentioned that this phenomenon indeed exists in glass/water thermosyphons. Although the influential factors have been discussed qualitatively, the quantitative analysis has yet to be conducted. This study focuses on the pulse boiling frequency as a criterion for the determination of flow patterns, and attempts are made to predict the frequency both experimentally and theoretically.« less

Dryout-type critical heat flux in vertical upward annular flow: effects of entrainment rate, initial entrained fraction and diameter

NASA Astrophysics Data System (ADS)

Wu, Zan; Wadekar, Vishwas; Wang, Chenglong; Sunden, Bengt

2018-01-01

This study aims to reveal the effects of liquid entrainment, initial entrained fraction and tube diameter on liquid film dryout in vertical upward annular flow for flow boiling. Entrainment and deposition rates of droplets were included in mass conservation equations to estimate the local liquid film mass flux in annular flow, and the critical vapor quality at dryout conditions. Different entrainment rate correlations were evaluated using flow boiling data of water and organic liquids including n-pentane, iso-octane and R134a. Effect of the initial entrained fraction (IEF) at the churn-to-annular flow transition was also investigated. A transitional Boiling number was proposed to separate the IEF-sensitive region at high Boiling numbers and the IEF-insensitive region at low Boiling numbers. Besides, the diameter effect on dryout vapor quality was studied. The dryout vapor quality increases with decreasing tube diameter. It needs to be pointed out that the dryout characteristics of submillimeter channels might be different because of different mechanisms of dryout, i.e., drying of liquid film underneath long vapor slugs and flow boiling instabilities.

Boiling incipience and convective boiling of neon and nitrogen

NASA Technical Reports Server (NTRS)

Papell, S. S.; Hendricks, R. C.

1977-01-01

Forced convection and subcooled boiling heat transfer data for liquid nitrogen and liquid neon were obtained in support of a design study for a 30 tesla cryomagnet cooled by forced convection of liquid neon. The cryogen data obtained over a range of system pressures, fluid flow rates, and applied heat fluxes were used to develop correlations for predicting boiling incipience and convective boiling heat transfer coefficients in uniformly heated flow channels. The accuracy of the correlating equations was then evaluated. A technique was also developed to calculate the position of boiling incipience in a uniformly heated flow channel. Comparisons made with the experimental data showed a prediction accuracy of + or - 15 percent.

Investigation on the heat transfer characteristics during flow boiling of liquefied natural gas in a vertical micro-fin tube

NASA Astrophysics Data System (ADS)

Xu, Bin; Shi, Yumei; Chen, Dongsheng

2014-03-01

This paper presents an experimental investigation on the heat transfer characteristics of liquefied natural gas flow boiling in a vertical micro-fin tube. The effect of heat flux, mass flux and inlet pressure on the flow boiling heat transfer coefficients was analyzed. The Kim, Koyama, and two kinds of Wellsandt correlations with different Ftp coefficients were used to predict the flow boiling heat transfer coefficients. The predicted results showed that the Koyama correlation was the most accurate over the range of experimental conditions.

The role of heater thermal response in reactor thermal limits during oscillartory two-phase flows

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ruggles, A.E.; Brown, N.W.; Vasil`ev, A.D.

1995-09-01

Analytical and numerical investigations of critical heat flux (CHF) and reactor thermal limits are conducted for oscillatory two-phase flows often associated with natural circulation conditions. It is shown that the CHF and associated thermal limits depend on the amplitude of the flow oscillations, the period of the flow oscillations, and the thermal properties and dimensions of the heater. The value of the thermal limit can be much lower in unsteady flow situations than would be expected using time average flow conditions. It is also shown that the properties of the heater strongly influence the thermal limit value in unsteady flowmore » situations, which is very important to the design of experiments to evaluate thermal limits for reactor fuel systems.« less

Characterization of Single Phase and Two Phase Heat and Momentum Transport in a Spiraling Radial Inow Microchannel Heat Sink

NASA Astrophysics Data System (ADS)

Ruiz, Maritza

Thermal management of systems under high heat fluxes on the order of hundreds of W/cm2 is important for the safety, performance and lifetime of devices, with innovative cooling technologies leading to improved performance of electronics or concentrating solar photovoltaics. A novel, spiraling radial inflow microchannel heat sink for high flux cooling applications, using a single phase or vaporizing coolant, has demonstrated enhanced heat transfer capabilities. The design of the heat sink provides an inward swirl flow between parallel, coaxial disks that form a microchannel of 1 cm radius and 300 micron channel height with a single inlet and a single outlet. The channel is heated on one side through a conducting copper surface, and is essentially adiabatic on the opposite side to simulate a heat sink scenario for electronics or concentrated photovoltaics cooling. Experimental results on the heat transfer and pressure drop characteristics in the heat sink, using single phase water as a working fluid, revealed heat transfer enhancements due to flow acceleration and induced secondary flows when compared to unidirectional laminar fully developed flow between parallel plates. Additionally, thermal gradients on the surface are small relative to the bulk fluid temperature gain, a beneficial feature for high heat flux cooling applications. Heat flux levels of 113 W/cm2 at a surface temperature of 77 deg C were reached with a ratio of pumping power to heat rate of 0.03%. Analytical models on single phase flow are used to explore the parametric trends of the flow rate and passage geometry on the streamlines and pressure drop through the device. Flow boiling heat transfer and pressure drop characteristics were obtained for this heat sink using water at near atmospheric pressure as the working fluid for inlet subcooling levels ranging from 20 to 80 deg C and mean mass flux levels ranging from 184-716 kg/m. 2s. Flow enhancements similar to singlephase flow were expected, as well as enhancements due to increased buoyant forces on vapor bubbles resulting from centripetal acceleration in the flow which will tend to draw the vapor towards the outlet. This can also aid in the reduction of vapor obstruction of the flow. The flow was identified as transitioning through three regimes as the heat rate was increased: partial subcooled flow boiling, oscillating boiling and fully developed flow boiling. During partial subcooled flow boiling, both forced convective and nucleate boiling effects are important. During oscillating boiling, the system fluctuated between partial subcooled flow boiling and fully developed nucleate boiling. Temperature and pressure oscillations were significant in this regime and are likely due to bubble constriction of flow in the microchannel. This regime of boiling is generally undesirable due to the large oscillations in temperatures and pressure and design constraints should be established to avoid large oscillations from occurring. During fully developed flow boiling, water vapor rapidly leaves the surface and the flow does not sustain large oscillations. Reducing inlet subcooling levels was found to reduce the magnitude of oscillations in the oscillating boiling regime. Additionally, reduced inlet subcooling levels reduced the average surface temperature at the highest heat flux levels tested when heat transfer was dominated by nucleate boiling, yet increased the average surface temperatures at low heat flux levels when heat transfer was dominated by forced convection. Experiments demonstrated heat fluxes up to 301 W/cm. 2at an average surface temperature of 134 deg C under partial subcooled flow boiling conditions. At this peak heat flux, the system required a pumping power to heat rate ratio of 0.01%. This heat flux is 2.4 times the typical values for critical heat flux in pool boiling under similar conditions.

Hemodynamic and neurochemical determinates of renal function in chronic heart failure.

PubMed

Gilbert, Cameron; Cherney, David Z I; Parker, Andrea B; Mak, Susanna; Floras, John S; Al-Hesayen, Abdul; Parker, John D

2016-01-15

Abnormal renal function is common in acute and chronic congestive heart failure (CHF) and is related to the severity of congestion. However, treatment of congestion often leads to worsening renal function. Our objective was to explore basal determinants of renal function and their response to hemodynamic interventions. Thirty-seven patients without CHF and 59 patients with chronic CHF (ejection fraction; 23 ± 8%) underwent right heart catheterization, measurements of glomerular filtration rate (GFR; inulin) and renal plasma flow (RPF; para-aminohippurate), and radiotracer estimates of renal sympathetic activity. A subset (26 without, 36 with CHF) underwent acute pharmacological intervention with dobutamine or nitroprusside. We explored the relationship between baseline and drug-induced hemodynamic changes and changes in renal function. In CHF, there was an inverse relationship among right atrial mean pressure (RAM) pressure, RPF, and GFR. By contrast, mean arterial pressure (MAP), cardiac index (CI), and measures of renal sympathetic activity were not significant predictors. In those with CHF there was also an inverse relationship among the drug-induced changes in RAM as well as pulmonary artery mean pressure and the change in GFR. Changes in MAP and CI did not predict the change in GFR in those with CHF. Baseline values and changes in RAM pressure did not correlate with GFR in those without CHF. In the CHF group there was a positive correlation between RAM pressure and renal sympathetic activity. There was also an inverse relationship among RAM pressure, GFR, and RPF in patients with chronic CHF. The observation that acute reductions in RAM pressure is associated with an increase in GFR in patients with CHF has important clinical implications. Copyright © 2016 the American Physiological Society.

Bubble dynamics, two-phase flow, and boiling heat transfer in a microgravity environment

NASA Technical Reports Server (NTRS)

Chung, Jacob N.

1994-01-01

The two-phase bubbly flow and boiling heat transfer in microgravity represents a substantial challenge to scientists and engineers and yet there is an urgent need to seek fundamental understanding in this area for future spacecraft design and space missions. At Washington State University, we have successfully designed, built and tested a 2.1 second drop tower with an innovation airbag deceleration system. Microgravity boiling experiments performed in our 0.6 second Drop Tower produced data flow visualizations that agree with published results and also provide some new understanding concerning flow boiling and microgravity bubble behavior. On the analytical and numerical work, the edge effects of finite divergent electrode plates on the forces experienced by bubbles were investigated. Boiling in a concentric cylinder microgravity and an electric field was numerically predicted. We also completed a feasibility study for microgravity boiling in an acoustic field.

Low gravity quenching of hot tubes with cryogens

NASA Technical Reports Server (NTRS)

Antar, Basil N.; Collins, Frank G.; Kawaji, M.

1992-01-01

An experimental proceedure for examining flow boiling in low gravity environment is presented. The proceedure involves both ground based and KC-135 flight experiments. Two experimental apparati were employed, one for studying subcooled liquid boiling and another for examining saturated liquid boiling. For the saturated flow experiments, liquid nitrogen was used while freon 113 was used for the subcooled flow experiments. The boiling phenomenon was investigated in both cases using flow visualization techniques as well as tube wall temperature measurements. The flow field in both cases was established by injecting cold liquid in a heated tube whose temperature was set above the saturation values. The tubes were both vertically and horizontally supported with the liquid injected from the lower end of the tube. The results indicate substantial differences in the flow patterns established during boiling between the ground based, (1-g), experiments and the flight experiments, (low-g). These differences in the flow patterns will be discussed and some explanations will be offered.

The renal nerves in chronic heart failure: efferent and afferent mechanisms

PubMed Central

Schiller, Alicia M.; Pellegrino, Peter R.; Zucker, Irving H.

2015-01-01

The function of the renal nerves has been an area of scientific and medical interest for many years. The recent advent of a minimally invasive catheter-based method of renal denervation has renewed excitement in understanding the afferent and efferent actions of the renal nerves in multiple diseases. While hypertension has been the focus of much this work, less attention has been given to the role of the renal nerves in the development of chronic heart failure (CHF). Recent studies from our laboratory and those of others implicate an essential role for the renal nerves in the development and progression of CHF. Using a rabbit tachycardia model of CHF and surgical unilateral renal denervation, we provide evidence for both renal efferent and afferent mechanisms in the pathogenesis of CHF. Renal denervation prevented the decrease in renal blood flow observed in CHF while also preventing increases in Angiotensin-II receptor protein in the microvasculature of the renal cortex. Renal denervation in CHF also reduced physiological markers of autonomic dysfunction including an improvement in arterial baroreflex function, heart rate variability, and decreased resting cardiac sympathetic tone. Taken together, the renal sympathetic nerves are necessary in the pathogenesis of CHF via both efferent and afferent mechanisms. Additional investigation is warranted to fully understand the role of these nerves and their role as a therapeutic target in CHF. PMID:26300788

Recent Work on Flow Boiling and Condensation in a Single Microchannel

NASA Astrophysics Data System (ADS)

Quan, Xiaojun; Wang, Guodong; Cheng, Ping; Wu, Huiying

2007-06-01

Recent visualization and measurements results on flow boiling of water and condensation of steam in a single microchannel, carried out at Shanghai Jiaotong University, is summarized in this paper. For flow boiling of water, experiments were conducted in a single microchannel with a trapezoidal cross-section having a hydraulic diameter of 186 μm and a length of 30 mm. A boiling flow pattern map in terms of heat flux versus mass flux, showing the unstable and stable boiling flow regimes in the microchannel, is obtained. For the investigation of condensation, experiments were carried out for steam condensing inside a single microchannel with a length of 60mm having a hydraulic diameter of 87 μm and 120μm respectively. The location of transition from annular flow to plug/slug flow in a microchannel is found to be dependent on both the dimensionless condensation heat transfer rate as well as the Reynolds number of the steam. The frequency for the occurrence of the injection flow is found to increase with the increasing mass flux.

Effects of treatment on respiratory rate, serum natriuretic peptide concentration, and Doppler echocardiographic indices of left ventricular filling pressure in dogs with congestive heart failure secondary to degenerative mitral valve disease and dilated cardiomyopathy.

PubMed

Schober, Karsten E; Hart, Taye M; Stern, Joshua A; Li, Xiaobai; Samii, Valerie F; Zekas, Lisa J; Scansen, Brian A; Bonagura, John D

2011-08-15

To evaluate the effects of treatment on respiratory rate, serum natriuretic peptide concentrations, and Doppler echocardiographic indices of left ventricular filling pressure in dogs with congestive heart failure (CHF) secondary to degenerative mitral valve disease (MVD) and dilated cardiomyopathy (DCM). Prospective cohort study. 63 client-owned dogs. Physical examination, thoracic radiography, analysis of natriuretic peptide concentrations, and Doppler echocardiography were performed twice, at baseline (examination 1) and 5 to 14 days later (examination 2). Home monitoring of respiratory rate was performed by the owners between examinations. In dogs with MVD, resolution of CHF was associated with a decrease in respiratory rate, serum N-terminal probrain natriuretic peptide (NT-proBNP) concentration, and diastolic functional class and an increase of the ratio of peak velocity of early diastolic transmitral flow to peak velocity of early diastolic lateral mitral annulus motion (E:Ea Lat). In dogs with DCM, resolution of CHF was associated with a decrease in respiratory rate and serum NT-proBNP concentration and significant changes in 7 Doppler echocardiographic variables, including a decrease of E:Ea Lat and the ratio of peak velocity of early diastolic transmitral flow to isovolumic relaxation time. Only respiratory rate predicted the presence of CHF at examination 2 with high accuracy. Resolution of CHF was associated with predictable changes in respiratory rate, serum NT-proBNP concentration, and selected Doppler echocardiographic variables in dogs with DCM and MVD. Home monitoring of respiratory rate was simple and was the most useful in the assessment of successful treatment of CHF.

Experimental research and numerical simulation on cryogenic line chill-down process

NASA Astrophysics Data System (ADS)

Jin, Lingxue; Cho, Hyokjin; Lee, Cheonkyu; Jeong, Sangkwon

2018-01-01

The empirical heat transfer correlations are suggested for the fast cool down process of the cryogenic transfer line from room temperature to cryogenic temperature. The correlations include the heat transfer coefficient (HTC) correlations for single-phase gas convection and film boiling regimes, minimum heat flux (MHF) temperature, critical heat flux (CHF) temperature and CHF. The correlations are obtained from the experimental measurements. The experiments are conducted on a 12.7 mm outer diameter (OD), 1.25 mm wall thickness and 7 m long stainless steel horizontal pipe with liquid nitrogen (LN2). The effect of the lengthwise position is verified by measuring the temperature profiles in near the inlet and the outlet of the transfer line. The newly suggested heat transfer correlations are applied to the one-dimensional homogeneous transient model to simulate the cryogenic line chill-down process, and the chill-down time and the cryogen consumption are well predicted in the mass flux range from 26.0 kg/m2 s to 73.6 kg/m2 s through the correlations.

Syngas fermentation to biofuel: evaluation of carbon monoxide mass transfer and analytical modeling using a composite hollow fiber (CHF) membrane bioreactor.

PubMed

Munasinghe, Pradeep Chaminda; Khanal, Samir Kumar

2012-10-01

In this study, the volumetric mass transfer coefficients (Ka) for CO were examined in a composite hollow fiber (CHF) membrane bioreactor. The mass transfer experiments were conducted at various inlet gas pressures (from 5 to 30 psig (34.5-206.8 kPa(g))) and recirculation flow rates (300, 600, 900, 1200 and 1500 mL/min) through CHF module. The highest Ka value of 946.6 1/h was observed at a recirculation rate of 1500 mL/min and at an inlet gas pressure of 30 psig(206.8 kPa(g)). The findings of this study confirm that the use of CHF membranes is effective and improves the efficiency CO mass transfer into the aqueous phase. Copyright © 2012 Elsevier Ltd. All rights reserved.

Pool and flow boiling in variable and microgravity

NASA Technical Reports Server (NTRS)

Merte, Herman, Jr.

1994-01-01

As is well known, boiling is an effective mode of heat transfer in that high heat flux levels are possible with relatively small temperature differences. Its optimal application requires that the process be adequately understood. A measure of the understanding of any physical event lies in the ability to predict its behavior in terms of the relevant parameters. Despite many years of research the predictability of boiling is currently possible only for quite specialized circumstances, e.g., the critical heat flux and film boiling for the pool boiling case, and then only with special geometries. Variable gravity down to microgravity provides the opportunity to test this understanding, but possibly more important, by changing the dimensional and time scales involved permits more detailed observations of elements involved in the boiling process, and perhaps discloses phenomena heretofore unknown. The focus here is on nucleate boiling although, as will be demonstrated below, under but certain circumstances in microgravity it can take place concurrently with the dryout process. In the presence of earth gravity or forced convection effects, the latter process is usually referred to as film boiling. However, no vapor film as such forms with pool boiling in microgravity, only dryout. Initial results are presented here for pool boiling in microgravity, and were made possible at such an early date by the availability of the Get-Away-Specials (GAS). Also presented here are some results of ground testing of a flow loop for the study of low velocity boiling, eventually to take place also in microgravity. In the interim, variable buoyancy normal to the heater surface is achieved by rotation of the entire loop relative to earth gravity. Of course, this is at the expense of varying the buoyancy parallel to the heater surface. Two questions which must be resolved early in the study of flow boiling in microgravity are (1) the lower limits of liquid flow velocity where buoyancy effects become significant to the boiling process (2) the effect of lower liquid flow velocities on the Critical Heat Flux when buoyancy is removed. Results of initial efforts in these directions are presented, albeit restricted currently to the ever present earth gravity.

Proposal of experimental setup on boiling two-phase flow on-orbit experiments onboard Japanese experiment module "KIBO"

NASA Astrophysics Data System (ADS)

Baba, S.; Sakai, T.; Sawada, K.; Kubota, C.; Wada, Y.; Shinmoto, Y.; Ohta, H.; Asano, H.; Kawanami, O.; Suzuki, K.; Imai, R.; Kawasaki, H.; Fujii, K.; Takayanagi, M.; Yoda, S.

2011-12-01

Boiling is one of the efficient modes of heat transfer due to phase change, and is regarded as promising means to be applied for the thermal management systems handling a large amount of waste heat under high heat flux. However, gravity effects on the two-phase flow phenomena and corresponding heat transfer characteristics have not been clarified in detail. The experiments onboard Japanese Experiment Module "KIBO" in International Space Station on boiling two-phase flow under microgravity conditions are proposed to clarify both of heat transfer and flow characteristics under microgravity conditions. To verify the feasibility of ISS experiments on boiling two-phase flow, the Bread Board Model is assembled and its performance and the function of components installed in a test loop are examined.

Incorporating Water Boiling in the Numerical Modelling of Thermal Remediation by Electrical Resistance Heating

NASA Astrophysics Data System (ADS)

Molnar, I. L.; Krol, M.; Mumford, K. G.

2017-12-01

Developing numerical models for subsurface thermal remediation techniques - such as Electrical Resistive Heating (ERH) - that include multiphase processes such as in-situ water boiling, gas production and recovery has remained a significant challenge. These subsurface gas generation and recovery processes are driven by physical phenomena such as discrete and unstable gas (bubble) flow as well as water-gas phase mass transfer rates during bubble flow. Traditional approaches to multiphase flow modeling soil remain unable to accurately describe these phenomena. However, it has been demonstrated that Macroscopic Invasion Percolation (MIP) can successfully simulate discrete and unstable gas transport1. This has lead to the development of a coupled Electro Thermal-MIP Model2 (ET-MIP) capable of simulating multiple key processes in the thermal remediation and gas recovery process including: electrical heating of soil and groundwater, water flow, geological heterogeneity, heating-induced buoyant flow, water boiling, gas bubble generation and mobilization, contaminant mass transport and removal, and additional mechanisms such as bubble collapse in cooler regions. This study presents the first rigorous validation of a coupled ET-MIP model against two-dimensional water boiling and water/NAPL co-boiling experiments3. Once validated, the model was used to explore the impact of water and co-boiling events and subsequent gas generation and mobilization on ERH's ability to 1) generate, expand and mobilize gas at boiling and NAPL co-boiling temperatures, 2) efficiently strip contaminants from soil during both boiling and co-boiling. In addition, a quantification of the energy losses arising from steam generation during subsurface water boiling was examined with respect to its impact on the efficacy of thermal remediation. While this study specifically targets ERH, the study's focus on examining the fundamental mechanisms driving thermal remediation (e.g., water boiling) renders these results applicable to a wide range of thermal and gas-based remediation techniques. 1. Mumford, K. G., et al. (2010), Adv. Water Resour. 2010, 33 (4), 504-513. 2. Krol, M. M., et al. (2011), Adv. Water Resour. 2011, 34 (4), 537-549. 3. Hegele, P. R. and Mumford, K. G. Journal of Contaminant Hydrology 2014, 165, 24-36.

Flow Boiling and Condensation Experiment (FBCE) for the International Space Station

NASA Technical Reports Server (NTRS)

Mudawar, Issam; Hasan, Mohammad M.; Kharangate, Chirag; O'Neill, Lucas; Konishi, Chris; Nahra, Henry; Hall, Nancy; Balasubramaniam, R.; Mackey, Jeffrey

2015-01-01

The proposed research aims to develop an integrated two-phase flow boiling/condensation facility for the International Space Station (ISS) to serve as primary platform for obtaining two-phase flow and heat transfer data in microgravity.

Anti-inflammatory effects of the new generation synthetic surfactant CHF5633 on Ureaplasma-induced cytokine responses in human monocytes.

PubMed

Glaser, Kirsten; Fehrholz, Markus; Henrich, Birgit; Claus, Heike; Papsdorf, Michael; Speer, Christian P

2017-02-01

Synthetic surfactants represent a promising alternative to animal-derived preparations in the treatment of neonatal respiratory distress syndrome. The synthetic surfactant CHF5633 has proven biophysical effectiveness and, moreover, demonstrated anti-inflammatory effects in LPS-stimulated monocytes. With ureaplasmas being relevant pathogens in preterm lung inflammation, the present study addressed immunomodulatory features on Ureaplasma-induced monocyte cytokine responses. Ureaplasma parvum-stimulated monocytes were exposed to CHF5633. TNF-α, IL-1β, IL-8, IL-10, TLR2 and TLR4 expression were analyzed using qPCR and flow cytometry. CHF5633 did not induce pro-inflammation, and did not aggravate Ureaplasma-induced pro-inflammatory cytokine responses. It suppressed U. parvum-induced intracellular TNF-α (p < 0.05) and IL-1β (p < 0.05) in neonatal monocytes and inhibited Ureaplasma-induced TNF-α mRNA (p < 0.05), TNF-α protein (p < 0.001), and IL-1β (p = 0.05) in adult monocytes. Ureaplasma-modulated IL-8, IL-10, TLR2 and TLR4 were unaffected. CHF5633 does neither act pro-apoptotic nor pro-inflammatory in native and Ureaplasma-infected monocytes. Suppression of Ureaplasma-induced TNF-α and IL-1β underlines anti-inflammatory features of CHF5633.

Investigation into flow boiling heat transfer in a minichannel with enhanced heating surface

NASA Astrophysics Data System (ADS)

Piasecka, Magdalena

2012-04-01

The paper presents results of flow boiling in a minichannel of 1.0 mm depth. The heating element for the working fluid (FC-72) that flows along the minichannel is a single-sided enhanced alloy foil made from Haynes-230. Microrecesses were formed on the selected area of the heating foil by laser technology. The observations of the flow structure were carried out through a piece of glass. Simultaneously, owing to the liquid crystal layer placed on the opposite side of the enhanced foil surface, it was possible to measure temperature distribution on the heating wall through another piece of glass. The experimental research has been focused on the transition from single phase forced convection to nucleate boiling, i.e. the zone of boiling incipience and further development of boiling. The objective of the paper is determining of the void fraction for some cross-sections of selected images for increasing heat fluxes supplied to the heating surface. The flow structure photos were processed in Corel graphics software and binarized. The analysis of phase volumes was developed in Techystem Globe software.

Heat transfer and structure of flow at boiling of refrigerant R134a in channels with inserts in the form of finned twisted tape

NASA Astrophysics Data System (ADS)

Shishkin, A. V.; Tarasevich, S. E.

2018-03-01

The paper presents the results of experimental study of heat transfer for the refrigerant R134a flow in the channels with finned twisted tape inserts at bubble boiling. The flow regimes implemented under the given conditions are shown. The stable cord-like flows appear at boiling in channels with twisted tape inserts and high vapor content when the liquid phase moves in the form of a stream (cord) along the central part of the tape, which is not an active heat exchange surface. At boiling this can lead to an increase in the length required for complete liquid evaporation. Existing geometric modifications of twisted tapes are used in the heat-exchange equipment at forced convection of the coolant and do not solve the problem of cord-like flows elimination. The present work discusses the experimental study of heat transfer at boiling of refrigerant R134a in the channels with twisted tape inserts that have fins on its surface.

Kinetics-based phase change approach for VOF method applied to boiling flow

NASA Astrophysics Data System (ADS)

Cifani, Paolo; Geurts, Bernard; Kuerten, Hans

2014-11-01

Direct numerical simulations of boiling flows are performed to better understand the interaction of boiling phenomena with turbulence. The multiphase flow is simulated by solving a single set of equations for the whole flow field according to the one-fluid formulation, using a VOF interface capturing method. Interface terms, related to surface tension, interphase mass transfer and latent heat, are added at the phase boundary. The mass transfer rate across the interface is derived from kinetic theory and subsequently coupled with the continuum representation of the flow field. The numerical model was implemented in OpenFOAM and validated against 3 cases: evaporation of a spherical uniformly heated droplet, growth of a spherical bubble in a superheated liquid and two dimensional film boiling. The computational model will be used to investigate the change in turbulence intensity in a fully developed channel flow due to interaction with boiling heat and mass transfer. In particular, we will focus on the influence of the vapor bubble volume fraction on enhancing heat and mass transfer. Furthermore, we will investigate kinetic energy spectra in order to identify the dynamics associated with the wakes of vapor bubbles. Department of Applied Mathematics, 7500 AE Enschede, NL.

Boiling-induced formation of colloidal gold in black smoker hydrothermal fluids

USGS Publications Warehouse

Gartman, Amy; Hannington, Mark; Jamieson, John W.; Peterkin, Ben; Garbe-Schönberg, Dieter; Findlay, Alyssa J; Fuchs, Sebastian; Kwasnitschka, Tom

2017-01-01

Gold colloids occur in black smoker fluids from the Niua South hydrothermal vent field, Lau Basin (South Pacific Ocean), confirming the long-standing hypothesis that gold may undergo colloidal transport in hydrothermal fluids. Six black smoker vents, varying in temperature from 250 °C to 325 °C, were sampled; the 325 °C vent was boiling at the time of sampling and the 250 °C fluids were diffusely venting. Native gold particles ranging from <50 nm to 2 µm were identified in 4 of the fluid samples and were also observed to precipitate on the sampler during collection from the boiling vent. Total gold concentrations (dissolved and particulate) in the fluid samples range from 1.6 to 5.4 nM in the high-temperature, focused flow vents. Although the gold concentrations in the focused flow fluids are relatively high, they are lower than potential solubilities prior to boiling and indicate that precipitation was boiling induced, with sulfide lost upon boiling to exsolution and metal sulfide formation. Gold concentrations reach 26.7 nM in the 250 °C diffuse flow sample, and abundant native gold particles were also found in the fluids and associated sulfide chimney and are interpreted to be a product of colloid accumulation and growth following initial precipitation upon boiling. These results indicate that colloid-driven precipitation as a result of boiling, the persistence of colloids after boiling, and the accumulation of colloids in diffuse flow fluids are important mechanisms for the enrichment of gold in seafloor hydrothermal systems.

System of closing relations of a two-fluid model for the HYDRA-IBRAE/LM/V1 code for calculation of sodium boiling in channels of power equipment

NASA Astrophysics Data System (ADS)

Usov, E. V.; Butov, A. A.; Dugarov, G. A.; Kudasov, I. G.; Lezhnin, S. I.; Mosunova, N. A.; Pribaturin, N. A.

2017-07-01

The system of equations from a two-fluid model is widely used in modeling thermohydraulic processes during accidents in nuclear reactors. The model includes conservation equations governing the balance of mass, momentum, and energy in each phase of the coolant. The features of heat and mass transfer, as well as of mechanical interaction between phases or with the channel wall, are described by a system of closing relations. Properly verified foreign and Russian codes with a comprehensive system of closing relations are available to predict processes in water coolant. As to the sodium coolant, only a few open publications on this subject are known. A complete system of closing relations used in the HYDRA-IBRAE/LM/V1 thermohydraulic code for calculation of sodium boiling in channels of power equipment is presented. The selection of these relations is corroborated on the basis of results of analysis of available publications with an account taken of the processes occurring in liquid sodium. A comparison with approaches outlined in foreign publications is presented. Particular attention has been given to the calculation of the sodium two-phase flow boiling. The flow regime map and a procedure for the calculation of interfacial friction and heat transfer in a sodium flow with account taken of high conductivity of sodium are described in sufficient detail. Correlations are presented for calculation of heat transfer for a single-phase sodium flow, sodium flow boiling, and sodium flow boiling crisis. A method is proposed for prediction of flow boiling crisis initiation.

Renal sympathetic denervation improves myocardial apoptosis in rats with isoproterenol-induced heart failure by downregulation of tumor necrosis factor-α and nuclear factor-κB.

PubMed

Yao, Wei; Wang, Neng; Qian, Jin; Bai, Lu; Zheng, Xiaoxin; Hou, Guo; Qiu, Xuan; Yang, Bo

2017-11-01

Chronic congestive heart failure (CHF) is the end outcome of organic heart diseases and one of the major diseases harmful to human health. Renal sympathetic denervation (RSD) is the anatomical basis of transcatheter renal sympathetic nerve ablation within the renal artery. To date, the roles of norepinephrine and angiotensin II (Ang II) in myocardial apoptosis and their underlying mechanisms have not been well explored. The aim of the present study was to verify the hypothesis that RSD is likely to inhibit myocardial apoptosis by inhibiting the release of norepinephrine and Ang II. An isoproterenol-induced CHF rat model was established, and the effects of RSD on myocardial apoptosis were examined using flow cytometry and TUNEL staining. The expression of factors associated with myocardial apoptosis, including p53, tumor necrosis factor-α (TNF-α), nuclear factor-κB (NF-κB), caspase-2 and -3, were measured using quantitative polymerase chain reaction and western blot analysis. The results indicated that the mRNA levels of p53, TNF-α, NF-κB, caspase-2 and -3 were significantly reduced in the myocardial tissues of rats in the CHF+RSD group when compared with the levels in the CHF+sham group (P<0.01 for all). In addition, the protein levels of p53, TNF-α, NF-κB and caspases-2 and -3 were decreased by 42.6, 41.3, 46.7, 30.0 and 35.8%, respectively, in myocardial tissues of rats in the CHF+RSD group in comparison with the CHF+sham group (P<0.01 for all). Furthermore, myocardial apoptosis was improved in rats in the CHF+RSD group compared with that in the CHF+sham group (P<0.01). In conclusion, the present study provides a theoretical basis for application of RSD in the treatment of CHF.

Renal sympathetic denervation improves myocardial apoptosis in rats with isoproterenol-induced heart failure by downregulation of tumor necrosis factor-α and nuclear factor-κB

PubMed Central

Yao, Wei; Wang, Neng; Qian, Jin; Bai, Lu; Zheng, Xiaoxin; Hou, Guo; Qiu, Xuan; Yang, Bo

2017-01-01

Chronic congestive heart failure (CHF) is the end outcome of organic heart diseases and one of the major diseases harmful to human health. Renal sympathetic denervation (RSD) is the anatomical basis of transcatheter renal sympathetic nerve ablation within the renal artery. To date, the roles of norepinephrine and angiotensin II (Ang II) in myocardial apoptosis and their underlying mechanisms have not been well explored. The aim of the present study was to verify the hypothesis that RSD is likely to inhibit myocardial apoptosis by inhibiting the release of norepinephrine and Ang II. An isoproterenol-induced CHF rat model was established, and the effects of RSD on myocardial apoptosis were examined using flow cytometry and TUNEL staining. The expression of factors associated with myocardial apoptosis, including p53, tumor necrosis factor-α (TNF-α), nuclear factor-κB (NF-κB), caspase-2 and −3, were measured using quantitative polymerase chain reaction and western blot analysis. The results indicated that the mRNA levels of p53, TNF-α, NF-κB, caspase-2 and −3 were significantly reduced in the myocardial tissues of rats in the CHF+RSD group when compared with the levels in the CHF+sham group (P<0.01 for all). In addition, the protein levels of p53, TNF-α, NF-κB and caspases-2 and −3 were decreased by 42.6, 41.3, 46.7, 30.0 and 35.8%, respectively, in myocardial tissues of rats in the CHF+RSD group in comparison with the CHF+sham group (P<0.01 for all). Furthermore, myocardial apoptosis was improved in rats in the CHF+RSD group compared with that in the CHF+sham group (P<0.01). In conclusion, the present study provides a theoretical basis for application of RSD in the treatment of CHF. PMID:29104628

Study on Fins' Effect of Boiling Flow in Millimeter Channel Heat Exchanger

NASA Astrophysics Data System (ADS)

Watanabe, Satoshi

2005-11-01

Recently, a lot of researches about compact heat exchangers with mini-channels have been carried out with the hope of obtaining a high-efficiency heat transfer, due to the higher ratio of surface area than existing heat exchangers. However, there are many uncertain phenomena in fields such as boiling flow in mini-channels. Thus, in order to understand the boiling flow in mini-channels to design high-efficiency heat exchangers, this work focused on the visualization measurement of boiling flow in a millimeter channel. A transparent acrylic channel (heat exchanger form), high-speed camera (2000 fps at 1024 x 1024 pixels), and halogen lamp (backup light) were used as the visualization system. The channel's depth is 2 mm, width is 30 mm, and length is 400 mm. In preparation for commercial use, two types of channels were experimented on: a fins type and a normal slit type (without fins). The fins are circular cylindrical obstacles (diameter is 5 mm) to promote heat transfer, set in a triangular array (distance between each center point is 10 mm). Especially in this work, boiling flow and heat transfer promotion in the millimeter channel heat exchanger with fins was evaluated using a high-speed camera.

[The proliferative characteristics of cells in culture during perfusion of the medium].

PubMed

Akatov, V S; Lavrovskaia, V P; Lezhnev, E I

1991-01-01

The proliferation of Chinese hamster fibroblasts (CHF) and NIH 3T3 cells was studied at different flow rates immediately above the cells. It is shown that there is a limiting density of saturation of the perfused culture that accounts for 1.7 x 10(6) - 2.0 x 10(6) cells/cm2 for NIH 3T3 cells, and for 6 x 10(6) - 7 x 10(6) cells/cm2 for CHF. The growth curves and the distribution of cells with respect to the phases of the cell cycle during cultivation with and without perfusion are presented. Based on the results obtained it is assumed that the limit of saturation density of perfused CHF culture is due to the mass transfer of the growth-inhibiting metabolites inside the multilayer structures. The assumption seems to hold true for NIH 3T3 cells, too, even though the multilayer character of growth of this culture is less pronounced than in CHF.

A study of boiling heat transfer as applied to the cooling of ball bearings in the high pressure oxygen turbopump of the space shuttle main engine

NASA Technical Reports Server (NTRS)

Schreiber, Will

1986-01-01

Two sets of ball bearings support the main shaft within the High Pressure Oxygen Turbopump (HPOTP) in the Space Shuttle Main Engine (SSME). In operation, these bearings are cooled and lubricated with high pressure liquid oxygen (LOX) flowing axially through the bearing assembly. Currently, modifications in the assembly design are being contemplated in order to enhance the lifetime of the bearings and to allow the HPOTP to operate under larger loads. An understanding of the fluid dynamics and heat transfer characteristics of the flowing LOX is necessary for the implementation of these design changes. The proposed computational model of the LOX fluid dynamics, in addition to dealing with a turbulent flow in a complex geometry, must address the complication associated with boiling and two-phase flow. The feasibility of and possible methods for modeling boiling heat transfer are considered. The theory of boiling as pertains to this particular problem is reviewed. Recommendations are given for experiments which would be necessary to establish validity for correlations needed to model boiling.

Reversal of OFI and CHF in Research Reactors Operating at 1 to 50 Bar. Version 1.0

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kalimullah, M.; Olson, A. P.; Dionne, B.

2014-02-28

The conditions at which the critical heat flux (CHF) and the heat flux at the onset of Ledinegg flow instability (OFI) are equal, are determined for a coolant channel with uniform heat flux as a function of five independent parameters: the channel exit pressure (P), heated length (Lh) , heated diameter (Dh), inlet temperature (Tin), and mass flux (G). A diagram is made by plotting the mass flux and heat flux at the OFI-CHF intersection (reversal from CHF > OFI to CHF < OFI as G increases) as a function of P (1 to 50 bar), for 36 combinations ofmore » the remaining three parameters (Lh , Dh , Tin): Lh = 0.28, 0.61, 1.18 m; Dh = 3, 4, 6, 8 mm; Tin = 30, 50, 70 °C. The use of the diagram to scope whether a research reactor is OFI-limited (below the curve) or CHF-limited based on the five parameters of its coolant channel is described. Justification for application of the diagram to research reactors with axially non-uniform heat flux is provided. Due to its limitations (uncertainties not included), the diagram cannot replace the detailed thermal-hydraulic analysis required for a reactor safety analysis. In order to make the OFI-CHF intersection diagram, two world-class CHF prediction methods (the Hall-Mudawar correlation and the extended Groeneveld 2006 table) are compared for 216 combinations of the five independent parameters. The two widely used OFI correlations (the Saha- Zuber and the Whittle-Forgan with η = 32.5) are also compared for the same combinations of the five parameters. The extended Groeneveld table and the Whittle-Forgan OFI correlation are selected for use in making the diagram. Using the above five design parameters, a research reactor can be represented by a point on the reversal diagram, and the diagram can be used to scope, without a thermal-hydraulic calculation, whether the OFI will occur before the CHF, or the CHF will occur before the OFI when the reactor power is increased keeping the five parameters fixed.« less

Experimental investigation on the heat transfer characteristics and flow pattern in vertical narrow channels heated from one side

NASA Astrophysics Data System (ADS)

Huang, Lihao; Li, Gang; Tao, Leren

2016-07-01

Experimental investigation for the flow boiling of water in a vertical rectangular channel was conducted to reveal the boiling heat transfer mechanism and flow patterns map aspects. The onset of nucleate boiling went upward with the increasing of the working fluid mass flow rate or the decreasing of the inlet working fluid temperature. As the vapour quality was increased, the local heat transfer coefficient increased first, then decreased, followed by various flow patterns. The test data from other researchers had a similar pattern transition for the bubble-slug flow and the slug-annular flow. Flow pattern transition model analysis was performed to make the comparison with current test data. The slug-annular and churn-annular transition models showed a close trend with current data except that the vapor phase superficial velocity of flow pattern transition was much higher than that of experimental data.

Studies on sodium boiling phenomena in out of pile rod bundles for various accidental situations in Liquid Metal Fast Breeder Reactors (LMFBR) experiments and interpretations

NASA Astrophysics Data System (ADS)

Seiler, J. M.; Rameau, B.

Bundle sodium boiling in nominal geometry for different accident conditions is reviewed. Voiding of a subassembly is controlled by not only hydrodynamic effects but mainly by thermal effects. There is a strong influence of the thermal inertia of the bundle material compared to the sodium thermal inertia. Flow instability, during a slow transient, can be analyzed with numerical tools and estimated using simplified approximations. Stable boiling operational conditions under bundle mixed convection (natural convection in the reactor) can be predicted. Voiding during a fast transient can be approximated from single channel calculations. The phenomenology of boiling behavior for a subassembly with inlet completely blocked, submitted to decay heat and lateral cooling; two-phase sodium flow pressure drop in a tube of large hydraulic diameter under adiabatic conditions; critical flow phenomena and voiding rate under high power, slow transient conditions; and onset of dry out under local boiling remains problematical.

Vascular oxidative stress and endothelial dysfunction in patients with chronic heart failure: role of xanthine-oxidase and extracellular superoxide dismutase.

PubMed

Landmesser, Ulf; Spiekermann, Stephan; Dikalov, Sergey; Tatge, Helma; Wilke, Ragna; Kohler, Christoph; Harrison, David G; Hornig, Burkhard; Drexler, Helmut

2002-12-10

Impaired flow-dependent, endothelium-mediated vasodilation (FDD) in patients with chronic heart failure (CHF) results, at least in part, from accelerated degradation of nitric oxide by oxygen radicals. The mechanisms leading to increased vascular radical formation, however, remain unclear. Therefore, we determined endothelium-bound activities of extracellular superoxide dismutase (ecSOD), a major vascular antioxidant enzyme, and xanthine-oxidase, a potent radical producing enzyme, and their relation to FDD in patients with CHF. ecSOD and xanthine-oxidase activities, released from endothelium into plasma by heparin bolus injection, were determined in 14 patients with CHF and 10 control subjects. FDD of the radial artery was measured using high-resolution ultrasound and was assessed before and after administration of the antioxidant vitamin C (25 mg/min; IA). In patients with CHF, endothelium-bound ecSOD activity was substantially reduced (5.0+/-0.7 versus 14.4+/-2.6 U x mL(-1) x min(-1); P<0.01) and closely related to FDD (r=0.61). Endothelium-bound xanthine-oxidase activity was increased by >200% (38+/-10 versus 12+/-4 nmol O2*- x microL(-1); P<0.05) and inversely related to FDD (r=-0.35) in patients with CHF. In patients with low ecSOD and high xanthine-oxidase activity, a greater benefit of vitamin C on FDD was observed, ie, the portion of FDD inhibited by radicals correlated negatively with ecSOD (r=-0.71) but positively with xanthine-oxidase (r=0.75). These results demonstrate that both increased xanthine-oxidase and reduced ecSOD activity are closely associated with increased vascular oxidative stress in patients with CHF. This loss of vascular oxidative balance likely represents a novel mechanism contributing to endothelial dysfunction in CHF.

The Effect of Dissolved Air on the Cooling Performance of a Partially Confined FC-72 Spray

DTIC Science & Technology

2008-07-01

95 iv LIST OF FIGURES Figure 1: Heat transfer coefficients: various processes and coolants ( Mudawar , 2001) .....1 Figure 2...various processes and coolants ( Mudawar , 2001). 2 In two-phase cooling a phase change of liquid to vapor, or boiling, occurs. The boiling...possible in flow boiling is also affected by the velocity of the flow and the amount of subcooling of the fluid ( Mudawar and Maddox, 1989). One highly

Acute impact of conventional and eccentric cycling on platelet and vascular function in patients with chronic heart failure.

PubMed

Haynes, Andrew; Linden, Matthew D; Chasland, Lauren C; Nosaka, Kazunori; Maiorana, Andrew; Dawson, Ellen A; Dembo, Lawrence H; Naylor, Louise H; Green, Daniel J

2017-06-01

Evidence-based guidelines recommend exercise therapy for patients with chronic heart failure (CHF). Such patients have increased atherothrombotic risk. Exercise can transiently increase platelet activation and reactivity and decrease vascular function in healthy participants, although data in CHF are scant. Eccentric (ECC) cycling is a novel exercise modality that may be particularly suited to patients with CHF, but the acute impacts of ECC cycling on platelet and vascular function are currently unknown. Our null hypothesis was that ECC and concentric (CON) cycling, performed at matched external workloads, would not induce changes in platelet or vascular function in patients with CHF. Eleven patients with heart failure with reduced ejection fraction (HFrEF) took part in discrete bouts of ECC and CON cycling. Before and immediately after exercise, vascular function was assessed by measuring diameter and flow-mediated dilation (FMD) of the brachial artery. Platelet function was measured by the flow cytometric determination of glycoprotein IIb/IIIa activation and granule exocytosis in the presence and absence of platelet agonists. ECC cycling increased baseline artery diameter (pre: 4.0 ± 0.8 mm vs. post: 4.2 ± 0.7 mm; P = 0.04) and decreased FMD%. When changes in baseline artery diameter were accounted for, the decrease in FMD post-ECC cycling was no longer significant. No changes were apparent after CON. Neither ECC nor CON cycling resulted in changes to any platelet-function measures (all P > 0.05). These results suggest that both ECC and CON cycling, at a moderate intensity and short duration, can be performed by patients with HFrEF without detrimental impacts on vascular or platelet function. NEW & NOTEWORTHY This is the first evidence to indicate that eccentric (ECC) cycling can be performed relatively safely by patients with chronic heart failure (CHF), as it did not result in impaired vascular or platelet function compared with conventional cycling. This is important, as acute exercise can transiently increase atherothrombotic risk, and ECC cycling is a novel exercise modality that may be particularly suited to patients with CHF. Copyright © 2017 the American Physiological Society.

Marangoni Effects on Near-Bubble Microscale Transport During Boiling of Binary Fluid Mixtures

NASA Technical Reports Server (NTRS)

V. Carey; Sun, C.; Carey, V. P.

2000-01-01

In earlier investigations, Marangoni effects were observed to be the dominant mechanism of boiling transport in 2-propanol/water mixtures under reduced gravity conditions. In this investigation we have examined the mechanisms of binary mixture boiling by exploring the transport near a single bubble generated in a binary mixture between a heated surface and cold surface. The temperature field created in the liquid around the bubble produces vaporization over the portion of its interface near the heated surface and condensation over portions of its interface near the cold surface. Experiments were conducted using different mixtures of water and 2-propanol under 1g conditions and under reduced gravity conditions aboard the KC135 aircraft. Since 2-propanol is more volatile than water, there is a lower concentration of 2-propanol near the hot surface and a higher concentration of 2-propanol near the cold plate relative to the bulk quantity. This difference in interface concentration gives rise to strong Marangoni effects that move liquid toward the hot plate in the near bubble region for 2-propanol and water mixtures. In the experiments in this study, the pressure of the test system was maintained at about 5 kPa to achieve the full spectrum of boiling behavior (nucleate boiling, critical heat flux and film boiling) at low temperature and heat flux levels. Heat transfer data and visual documentation of the bubble shape were extracted from the experimental results. In the 1-g experiments at moderate to high heat flux levels, the bubble was observed to grow into a mushroom shape with a larger top portion near the cold plate due to the buoyancy effect. The shape of the bubble was somewhat affected by the cold plate subcooling and the superheat of the heated surface. At low superheat levels for the heated surface, several active nucleation sites were observed, and the vapor stems from them merged to form a larger bubble. The generation rate of vapor is moderate in this regime and the bubble shape is cylindrical in appearance. In some instances, the bubble interface appeared to oscillate. At higher applied heat flux levels, the top of the bubble became larger, apparently to provide more condensing interface area adjacent to the cold plate. Increasing the applied heat flux ultimately led to dry-out of the heated surface, with conditions just prior to dryout corresponding to the maximum heat flux (CHF). A more stable bubble was observed when the system attained the minimum heat flux (for film boiling). In this regime, most of the surface under the bottom of the bubble was dry with nucleate boiling sometimes occuring around the contact perimeter of the bubble at heated surface. Different variations (e.g. gap between two plates, molar concentration of the liquid mixture) of the experiments were examined to determine parametric effects on the boiling process and to determine the best conditions for the KC135 reduced gravity tests. Variation of the gap was found to have a minor impact on the CHF. However, reducing the gap between the hot and cold surface was observed to significantly reduce the minimum heat flux for fixed molar concentration of 2-propanol. In the reduced gravity experiments aboard the KC135 aircraft, the bubble formed in the 6.4 mm gap was generally cylindrical or barrel shaped and it increased its extent laterally as the surface superheat increased. In reduced gravity experiments, dryout of the heated surface under the bubble was observed to occur at a lower superheated temperature than for 1g conditions. Observed features of the boiling process and heat transfer data under reduced gravity will be discussed in detail. The results of the reduced gravity experiments will also be compared to those obtained in comparable 1g experiments. In tandem with the experiments we are also developing a computational model of the transport in the liquid surrounding the bubble during the boiling process. The computational model uses a level set method to model motion of the interface. It will incorporate a macroscale treatment of the transport in the liquid gap between the surfaces and a microscale treatment of transport in the regions between the bubble interface and the solid surfaces. The features of the model will be described in detail. Future research directions suggested by the results to date will also be discussed.

Fast reactor safety and related physics. Volume IV. Phenomenology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1976-01-01

Separate abstracts are included for 58 papers concerning single-phase flow and sodium boiling; sodium boiling and subassembly flow blockages; transient-overpower and loss-of-flow experiments; fuel and cladding behavior and relocation; fuel and cladding freezing; molten-fuel-coolant interaction; aerosols and fission product release, and post-accident heat removal. Thirteen papers have been perivously abstracted and included in ERA.

Impact of selected parameters on the development of boiling and flow resistance in the minichannel

NASA Astrophysics Data System (ADS)

Piasecka, Magdalena; Ziętala, Kinga

2015-05-01

The paper presents results of flow boiling in a rectangular minichannel 1 mm deep, 40 mm wide and 360 mm long. The heating element for FC-72 flowing in the minichannel was the thin alloy foil designated as Haynes-230. There was a microstructure on the side of the foil which comes into contact with fluid in the channel. Two types of microstructured heating surfaces: one with micro-recesses distributed evenly and another with mini-recesses distributed unevenly were used. The paper compares the impact of the microstructured heating surface and minichannel positions on the development of boiling and two phase flow pressure drop. The local heat transfer coefficients and flow resistance obtained in experiment using three positions of the minichannel, e.g.: 0°, 90° and 180° were analyzed. The study of the selected thermal and flow parameters (mass flux density and inlet pressure), geometric parameters and type of cooling liquid on the boiling heat transfer was also conducted. The most important factor turned out to be channel orientation. Application of the enhanced heating surface caused the increase of the heat transfer coefficient from several to several tens per cent, in relation to the plain surface.

Atmospheric Lifetime of CHF2Br, a Proposed Substitute for Halons.

PubMed

Talukdar, R; Mellouki, A; Gierczak, T; Burkholder, J B; McKeen, S A; Ravishankara, A R

1991-05-03

The rate coefficients, k(1), for the reaction of OH with CHF(2)Br have been measured using pulsed photolysis and discharge flow techniques at temperatures (T) between 233 and 432 K to be k(1), = (7.4 +/- 1.6) x 10(-13) exp[-(1300 +/- 100)/T] cubic centimeters per molecule per second. The ultraviolet absorption cross sections, sigma, of this molecule between 190 and 280 nanometers were measured at 296 K. The k(1), and sigma values were used in a one-dimensional model to obtain an atmospheric lifetime of approximately 7 years for CHF(2)Br. This lifetime is shorter by approximately factors of 10 and 2 than those for CF(3)Br and CF(2)ClBr, respectively. The ozone depletion potentials of the three compounds will reflect these lifetimes.

Resting arterial hypoxaemia in subjects with chronic heart failure, pulmonary hypertension and patent foramen ovale.

PubMed

Lovering, Andrew T; Lozo, Mislav; Barak, Otto; Davis, James T; Lojpur, Mihajlo; Lozo, Petar; Čaljkušić, Krešimir; Dujić, Željko

2016-05-01

What is the central question of this study? Does a patent foramen ovale contribute to resting arterial hypoxaemia, defined as arterial oxygen saturation <95%, in subjects with chronic heart failure with or without pulmonary arterial hypertension? What is the main finding and its importance? The presence of a patent foramen ovale contributed to resting arterial hypoxaemia only in subjects with chronic heart failure with pulmonary arterial hypertension. These data suggest that the presence of a patent foramen ovale should be considered in chronic heart failure patients with arterial hypoxaemia and pulmonary hypertension. The roles of intrapulmonary and intracardiac shunt in contributing to arterial hypoxaemia at rest in subjects with chronic heart failure (CHF) have not been well investigated. We hypothesized that blood flow through intrapulmonary arteriovenous anastomoses (Q̇ IPAVA ) and/or patent foramen ovale (Q̇ PFO ) could potentially contribute to arterial hypoxaemia and, with pulmonary hypertension (PH) secondary to CHF, this contribution may be exacerbated. Fifty-six subjects with CHF (New York Heart Association Classes I-III), with (+) or without (-) PH [defined as peak tricuspid regurgitation velocity ≥2.9 m s(-1) (CHF PH+, n = 32) and peak tricuspid regurgitation velocity ≤2.8 m s(-1) (CHF PH-, n = 24)], underwent arterial blood gas analysis and transthoracic saline contrast echocardiography concomitant with transcranial Doppler to detect Q̇ IPAVA and Q̇ PFO . Seventeen of 56 subjects with CHF (30%) had Q̇ PFO , but only four of 56 subjects with CHF had Q̇ IPAVA (7%), both similar to age- and sex-matched control subjects. Mean arterial oxygen saturation (SaO2) was lower in subjects with Q̇ PFO . Only CHF PH+ subjects with Q̇ PFO had arterial hypoxaemia (mean SaO2 <95%). Bubble scores assessed using transthoracic saline contrast echocardiography were correlated with microembolic signals detected with transcranial Doppler in subjects with Q̇ PFO . Significant Q̇ IPAVA was not present in either CHF PH+ or PH- subjects, suggesting that Q̇ IPAVA is not dependent on increased pulmonary pressure and does not contribute significantly to arterial hypoxaemia in older subjects with CHF. Given that SaO2 was lower in all subjects with CHF who had Q̇ PFO compared with those without Q̇ PFO , a patent foramen ovale should be considered when determining potential causes of arterial hypoxaemia, because Q̇ PFO was present in 30% of these subjects. © 2016 The Authors. Experimental Physiology © 2016 The Physiological Society.

Preliminary design of flight hardware for two-phase fluid research

NASA Technical Reports Server (NTRS)

Hustvedt, D. C.; Oonk, R. L.

1982-01-01

This study defined the preliminary designs of flight software for the Space Shuttle Orbiter for three two-phase fluid research experiments: (1) liquid reorientation - to study the motion of liquid in tanks subjected to small accelerations; (2) pool boiling - to study low-gravity boiling from horizontal cylinders; and (3) flow boiling - to study low-gravity forced flow boiling heat transfer and flow phenomena in a heated horizontal tube. The study consisted of eight major tasks: reassessment of the existing experiment designs, assessment of the Spacelab facility approach, assessment of the individual carry-on approach, selection of the preferred approach, preliminary design of flight hardware, safety analysis, preparation of a development plan, estimates of detailed design, fabrication and ground testing costs. The most cost effective design approach for the experiments is individual carry-ons in the Orbiter middeck. The experiments were designed to fit into one or two middeck lockers. Development schedules for the detailed design, fabrication and ground testing ranged from 15 1/2 to 18 months. Minimum costs (in 1981 dollars) ranged from $463K for the liquid reorientation experiment to $998K for the pool boiling experiment.

Regional Frequency Computation Users Manual.

DTIC Science & Technology

1972-07-01

increment of flow used to prevent infinite logarithms for events with zero flow X = Mean logarithm of flow events N = Total years of record S = Unbiased...C LIBRARY 3’jr.RfUTINFES USEO--ALflGpSINvAB3 1002 c PRGRAM ~ SUBRflUTINES CR0UTpR,chfNN-SFE COt’MENTS I-N RNGEN 100 C REFERENCE TOl TAPE ? AT

Boiling local heat transfer enhancement in minichannels using nanofluids

PubMed Central

2013-01-01

This paper reports an experimental study on nanofluid convective boiling heat transfer in parallel rectangular minichannels of 800 μm hydraulic diameter. Experiments are conducted with pure water and silver nanoparticles suspended in water base fluid. Two small volume fractions of silver nanoparticles suspended in water are tested: 0.000237% and 0.000475%. The experimental results show that the local heat transfer coefficient, local heat flux, and local wall temperature are affected by silver nanoparticle concentration in water base fluid. In addition, different correlations established for boiling flow heat transfer in minichannels or macrochannels are evaluated. It is found that the correlation of Kandlikar and Balasubramanian is the closest to the water boiling heat transfer results. The boiling local heat transfer enhancement by adding silver nanoparticles in base fluid is not uniform along the channel flow. Better performances and highest effect of nanoparticle concentration on the heat transfer are obtained at the minichannels entrance. PMID:23506445

Enhanced boiling in microchannels due to recirculation induced by repeated saw-toothed cross-sectional geometry

NASA Astrophysics Data System (ADS)

Gao, Le; Bhavnani, Sushil H.

2017-10-01

A saw-toothed shaped microchannel heat sink is investigated for enhancing flow boiling heat transfer. Tests are conducted at mass fluxes of 444-1776 kg/m2 s and an inlet subcooling of 15 °C. The effects of channel geometry on boiling curves, flow patterns, pressure drops, and heat transfer coefficient are discussed in this letter. It is found that heat transfer performance is enhanced by up to 50% especially at heat flux levels associated with the current generation of microprocessors.

The heat transfer coefficient determination with the use of the Beck-Trefftz method in flow boiling in a minichannel

NASA Astrophysics Data System (ADS)

Strąk, Kinga; Maciejewska, Beata; Piasecka, Magdalena

2018-06-01

In this paper, the solution of the two-dimensional inverse heat transfer problem with the use of the Beck method coupled with the Trefftz method is proposed. This method was applied for solving an inverse heat conduction problem. The aim of the calculation was to determine the boiling heat transfer coefficient on the basis of temperature measurements taken by infrared thermography. The experimental data of flow boiling heat transfer in a single vertical minichannel of 1.7 mm depth, heated asymmetrically, were used in calculations. The heating element for two refrigerants (FC-72 and HFE-7100, 3M) flowing in the minichannel was the plate enhanced on the side contacting with the fluid. The analysis of the results was performed on the basis of experimental series obtained for the same heat flux and two different mass flow velocities. The results were presented as infrared thermographs, heated wall temperature and heat transfer coefficient as a function of the distance from the minichannel inlet. The results was discussed for the subcooled and saturated boiling regions separately.

Impact of Fe powder sintering and soldering in production of porous heating surface on flow boiling heat transfer in minichannels

NASA Astrophysics Data System (ADS)

Depczyński, Wojciech; Piasecki, Artur; Piasecka, Magdalena; Strąk, Kinga

2017-10-01

This paper focuses on identification of the impact of porous heated surface on flow boiling heat transfer in a rectangular minichannel. The heated element for Fluorinert FC-72 was a thin plate made of Haynes-230. Infrared thermography was used to determine changes in the temperature on its outer smooth side. The porous surface in contact with the fluid in the minichannel was produced in two processes: sintering or soldering of Fe powder to the plate. The results were presented as relationships between the heat transfer coefficient and the distance from the minichannel inlet and as boiling curves. Results obtained for using a smooth heated plate at the saturated boiling region were also presented to compare. In the subcooled boiling region, at a higher heat flux, the heat transfer coefficient was slightly higher for the surface prepared via soldering. In the saturated boiling region, the local heat transfer coefficients obtained for the smooth plate surface were slightly higher than those achieved from the sintered plate surface. The porous structures formed have low thermal conductivity. This may induce noticeable thermal resistance at the diffusion bridges of the sintered structures, in particular within the saturated boiling region.

Impact of different thickness of the smooth heated surface on flow boiling heat transfer

NASA Astrophysics Data System (ADS)

Strąk, Kinga; Piasecka, Magdalena

2018-06-01

This paper presents a comparison of the performance of three smooth heated surfaces with different thicknesses. Analysis was carried out on an experimental setup for flow boiling heat transfer. The most important element of the setup was the test section with a rectangular minichannel, 1.7 mm deep, 16 mm wide and 180 mm long, oriented vertically. The heated element for the FC-72 Fluorinert flowing in the minichannel was designated as a Haynes-230 alloy plate (0.10 mm and 0.45 mm thick) or a Hastelloy X alloy plate (0.65 mm thick). Infrared thermography was used to measure the temperature of the outer plate surface. The local values of the heat transfer coefficient for stationary state conditions were calculated using a simple one-dimensional method. The experimental results were presented as the relationship between the heat transfer coefficients in the subcooled boiling region and the distance along the minichannel length and boiling curves. The highest local heat transfer coefficients were recorded for the surface of 0.10 mm thick heated plate at the outlet and 0.45 mm thick plate at the minichannel inlet. All boiling curves were typical in shape.

Promoting universal financial protection: a case study of new management of community health insurance in Tanzania.

PubMed

Borghi, Josephine; Maluka, Stephen; Kuwawenaruwa, August; Makawia, Suzan; Tantau, Juma; Mtei, Gemini; Ally, Mariam; Macha, Jane

2013-06-13

The National Health Insurance Fund (NHIF), a compulsory formal sector scheme took over the management of the Community Health Fund (CHF), a voluntary informal sector scheme, in 2009. This study assesses the origins of the reform, its effect on management and reporting structures, financial flow adequacy, reform communication and acceptability to key stakeholders, and initial progress towards universal coverage. The study relied on national data sources and an in-depth collective case study of a rural and an urban district to assess awareness and acceptability of the reform, and fund availability and use relative to need in a sample of facilities. The reform was driven by a national desire to expand coverage and increase access to services. Despite initial delays, the CHF has been embedded within the NHIF organisational structure, bringing more intensive and qualified supervision closer to the district. National CHF membership has more than doubled. However, awareness of the reform was limited below the district level due to the reform's top-down nature. The reform was generally acceptable to key stakeholders, who expected that benefits between schemes would be harmonised.The reform was unable to institute changes to the CHF design or district management structures because it has so far been unable to change CHF legislation which also limits facility capacity to use CHF revenue. Further, revenue generated is currently insufficient to offset treatment and administration costs, and the reform did not improve the revenue to cost ratio. Administrative costs are also likely to have increased as a result of the reform. Informal sector schemes can benefit from merger with formal sector schemes through improved data systems, supervision, and management support. However, effects will be maximised if legal frameworks can be harmonised early on and a reduction in administrative costs is not guaranteed.

Heat Transfer Enhancement due to Bubble Pumping in FC-72 Near the Saturation Temperature

DTIC Science & Technology

1991-03-01

boiling, (2) reducing wall superheat during nucleate boiling and (3) enhancing critical heat flux ( Mudawar , 1990) . Since the heat transfer potential of...flux from a simulated electronic chip attached to the wall of a vertical rectangular channel was determined by Mudawar and Madox (1988). They concluded...Surface Boiling," Industrial and Engineering Chemistry, vol. 41, No. 9, 1949. Mudawar , I., and D.E. Maddox, Critical Heat Flux in Subcooled Flow Boiling

Cryogenic two-phase flow during chilldown: Flow transition and nucleate boiling heat transfer

NASA Astrophysics Data System (ADS)

Jackson, Jelliffe Kevin

The recent interest in space exploration has placed a renewed focus on rocket propulsion technology. Cryogenic propellants are the preferred fuel for rocket propulsion since they are more energetic and environmentally friendly compared with other storable fuels. Voracious evaporation occurs while transferring these fluids through a pipeline that is initially in thermal equilibrium with the environment. This phenomenon is referred to as line chilldown. Large temperature differences, rapid transients, pressure fluctuations and the transition from the film boiling to the nucleate boiling regime characterize the chilldown process. Although the existence of the chilldown phenomenon has been known for decades, the process is not well understood. Attempts have been made to model the chilldown process; however the results have been fair at best. A major shortcoming of these models is the use of correlations that were developed for steady, non-cryogenic flows. The development of reliable correlations for cryogenic chilldown has been hindered by the lack of experimental data. An experimental facility was constructed that allows the flow structure, the temperature history and the pressure history to be recorded during the line chilldown process. The temperature history is then utilized in conjunction with an inverse heat conduction procedure that was developed, which allows the unsteady heat transfer coefficient on the interior of the pipe wall to be extracted. This database is used to evaluate present predictive models and correlations for flow regime transition and nucleate boiling heat transfer. It is found that by calibrating the transition between the stratified-wavy and the intermittent/annular regimes of the Taitel and Dukler flow regime map, satisfactory predictions are obtained. It is also found that by utilizing a simple model that includes the effect of flow structure and incorporating the enhancement provided by the local heat flux, significant improvement in the predictive capabilities of the Muller-Steinhagen and Jamialahmadi correlation for nucleate flow boiling is achieved.

Criteria for approximating certain microgravity flow boiling characteristics in Earth gravity.

PubMed

Merte, Herman; Park, Jaeseok; Shultz, William W; Keller, Robert B

2002-10-01

The forces governing flow boiling, aside from system pressure, are buoyancy, liquid momentum, interfacial surface tensions, and liquid viscosity. Guidance for approximating certain aspects of the flow boiling process in microgravity can be obtained in Earth gravity research by the imposition of a liquid velocity parallel to a flat heater surface in the inverted position, horizontal, or nearly horizontal, by having buoyancy hold the heated liquid and vapor formed close to the heater surface. Bounds on the velocities of interest are obtained from several dimensionless numbers: a two-phase Richardson number, a two-phase Weber number, and a Bond number. For the fluid used in the experimental work here, liquid velocities in the range U = 5-10cm/sec are judged to be critical for changes in behavior of the flow boiling process. Experimental results are presented for flow boiling heat transfer, concentrating on orientations that provide the largest reductions in buoyancy parallel to the heater surface, varying +/-5 degrees from facing horizontal downward. Results are presented for velocity, orientation, and subcooling effects on nucleation, dryout, and heat transfer. Two different heater surfaces were used: a thin gold film on a polished quartz substrate, acting as a heater and resistance thermometer, and a gold-plated copper heater. Both transient and steady measurements of surface heat flux and superheat were made with the quartz heater; only steady measurements were possible with the copper heater. R-113 was the fluid used; the velocity varied over the interval 4-16cm/sec; bulk liquid subcooling varied over 2-20 degrees C; heat flux varied over 4-8W/cm(2).

Effect of K+ATP channel and adenosine receptor blockade during rest and exercise in congestive heart failure.

PubMed

Traverse, Jay H; Chen, YingJie; Hou, MingXiao; Li, Yunfang; Bache, Robert J

2007-06-08

K(+)(ATP) channels are important metabolic regulators of coronary blood flow (CBF) that are activated in the setting of reduced levels of ATP or perfusion pressure. In the normal heart, blockade of K(+)(ATP) channels results in a approximately 20% reduction in resting CBF but does not impair the increase in CBF that occurs during exercise. In contrast, adenosine receptor blockade fails to alter CBF or myocardial oxygen consumption (MVO(2)) in the normal heart but contributes to the increase in CBF during exercise when vascular K(+)(ATP) channels are blocked. Congestive heart failure (CHF) is associated with a decrease in CBF that is matched to a decrease in MVO(2) suggesting downregulation of myocardial energy utilization. Because myocardial ATP levels and coronary perfusion pressure are reduced in CHF, this study was undertaken to examine the role of K(+)(ATP) channels and adenosine in dogs with pacing-induced CHF. Myocardial blood flow (MBF) and MVO(2) were measured during rest and treadmill exercise before and after K(+)(ATP) channel blockade with glibenclamide (50 microg/kg/min ic) or adenosine receptor blockade with 8-phenyltheophylline (8-PT; 5 mg/kg iv). Inhibition of K(+)(ATP) channels resulted in a decrease in CBF and MVO(2) at rest and during exercise without a change in the relationship between CBF and MVO(2). In contrast, adenosine receptor blockade caused a significant increase in CBF that occurred secondary to an increase of MVO(2). These findings demonstrate that coronary K(+)(ATP) channel activity contribute to the regulation of resting MBF in CHF, and that endogenous adenosine may act to inhibit MVO(2) in the failing heart.

Exercise training improves function of circulating angiogenic cells in patients with chronic heart failure.

PubMed

Van Craenenbroeck, Emeline M; Hoymans, Vicky Y; Beckers, Paul J; Possemiers, Nadine M; Wuyts, Kurt; Paelinck, Bernard P; Vrints, Christiaan J; Conraads, Viviane M

2010-09-01

Alterations in circulating angiogenic cells (CAC) and endothelial progenitor cells (EPC), known to contribute to endothelial repair, could explain the reversal of endothelial function in response to exercise training. Moreover, training-induced vascular remodeling might affect the acute response of EPC and CAC following a single exercise bout. We studied the impact of exercise training on CAC function and numbers of CD34(+)/KDR(+) EPC in patients with chronic heart failure (CHF) and we assessed the effect of acute exercise on CAC and EPC in sedentary and trained patients. Twenty-one sedentary CHF patients underwent 6-month exercise training and were compared to a non-trained control group (n = 17) and 10 healthy age-matched subjects. At baseline and follow-up, flow-mediated dilation was assessed and graded exercise testing (GXT) was performed. Before and immediately after GXT, CAC migratory capacity was assessed in vitro and circulating CD34(+)/KDR(+) EPC were quantified using flow cytometry. At baseline, CAC migration was significantly impaired in sedentary CHF patients but normalized acutely after GXT. Training corrected endothelial dysfunction, which coincided with a 77% increase in CAC migration (P = 0.0001). Moreover, the GXT-induced improvement detected at baseline was no longer observed after training. Numbers of CD34(+)/KDR(+) EPC increased following 6-month exercise training (P = 0.021), but were not affected by GXT, either prior or post-training. In conclusion, the present findings demonstrate for the first time that exercise training in CHF reverses CAC dysfunction and increases numbers of CD34(+)/KDR(+) EPC, which is accompanied by improvement of peripheral endothelial function. The acute exercise-induced changes in CAC function wane with exercise training, suggesting that repetitive exercise bouts progressively lead to functional endothelial repair.

Nanoparticle coating of a microchannel surface is an effective method for increasing the critical heat flux

NASA Astrophysics Data System (ADS)

Shustov, M. V.; Kuzma-Kichta, Yu. A.; Lavrikov, A. V.

2017-04-01

Results are presented of an investigation into water boiling in a single microchannel 0.2 mm high, 3 mm wide, and 13.7 mm long with a smooth heating surface or with a coating from aluminum oxide nanoparticles. The experimental procedure and the test setup are described. The top wall of the microchannel is made of glass so that video recording in the reflected light of the process can be made. A coating of Al2O3 particles is applied onto the heating surface before the experiments using a method developed by the authors of the paper. The experiments yielded data on heat transfer and void fraction and its fluctuations for the bubble and transient boiling in the microchannel. The dependence was established of the heat flux on the temperature of the microchannel wall with a smooth surface or a surface with Al2O3 nanoparticle coating for various mass flows in the microchannel. The boiling crisis has been found to occur in the microchannel with a nanoparticle coating at a considerably higher heat flux than that in the channel without coating. The experimental data also suggest that the nanoparticle coating improves heat transfer in the transition boiling region. Processing of the data obtained using a high-speed video revealed void fraction fluctuations enabling us to describe two-phase flow regimes with the flow boiling in a microchannel. It has been found that a return flow occurs in the microchannel under certain conditions. A hypothesis for its causes is proposed. The dependence of the void fraction on the steam quality in the microchannel with or without a nanoparticle coating was determined from the video records. The experimental data on void fraction for boiling in the microchannel without coating are approximated by an empirical correlation. The experiments demonstrate that the void fraction during boiling in the microchannel with a nanoparticle coating is higher than during boiling in the channel without coating (where φ and x are the void fraction and the steam quality, respectively) in the region of a sharp increase in the φ( x) curve.

A Correlation for Forced Convective Boiling Heat Transfer of Refrigerants in a Microfin Tube

NASA Astrophysics Data System (ADS)

Momoki, Satoru; Yu, Jian; Koyama, Shigeru; Fujii, Tetsu; Honda, Hiroshi

The experimental study is reported on the forced convective boiling of pure refrigerants HCFC22, HFC134a and HCFC123 flowing in a horizontal microfin tube. The local heat transfer coefficient defined based on the actual inside surface area is measured in the ranges of mass velocity of 200 to 400 kg/m2s, heat flux of 5 to 64 kW/m2 and reduced pressure of 0.07 to 0.24. Using the Chen-type model, a new correlation for microfin tubes is proposed considering the enhancement effect of microfins on both the convective heat transfer and the nucleate boiling components. In the convective heat transfer component, the correlation to predict the heat transfer coefficient of liquid-only flow is determined from preliminary experiments on single-phase flow in microfin tubes, and the two-phase flow enhancement factor is determined from the present experimental data. For the nucleate boiling component, the correlation of Takamatsu et al. for smooth tube is modified. The prediction of the present correlation agrees well with present experimental data, and is available for several microfin tubes which were tested by other researchers.

New Correlation Methods of Evaporation Heat Transfer in Horizontal Microfine Tubes

NASA Astrophysics Data System (ADS)

Makishi, Osamu; Honda, Hiroshi

A stratified flow model and an annular flow model of evaporation heat transfer in horizontal microfin tubes have been proposed. In the stratified flow model, the contributions of thin film evaporation and nucleate boiling in the groove above a stratified liquid were predicted by a previously reported numerical analysis and a newly developed correlation, respectively. The contributions of nucleate boiling and forced convection in the stratified liquid region were predicted by the new correlation and the Carnavos equation, respectively. In the annular flow model, the contributions of nucleate boiling and forced convection were predicted by the new correlation and the Carnavos equation in which the equivalent Reynolds number was introduced, respectively. A flow pattern transition criterion proposed by Kattan et al. was incorporated to predict the circumferential average heat transfer coefficient in the intermediate region by use of the two models. The predictions of the heat transfer coefficient compared well with available experimental data for ten tubes and four refrigerants.

A new hydrodynamic prediction of the peak heat flux from horizontal cylinders in low speed upflow

NASA Technical Reports Server (NTRS)

Ungar, E. K.; Eichhorn, R.

1988-01-01

Flow-boiling data have been obtained for horizontal cylinders in saturated acetone, isopropanol, and water, yielding heat flux vs. wall superheat boiling curves for the organic liquids. A region of low speed upflow is identified in which long cylindrical bubbles break off from the wake with regular frequency. The Strouhal number of bubble breakoff is a function only of the Froude number in any liquid, and the effective wake thickness in all liquids is a function of the density ratio and the Froude number. A low speed flow boiling burnout prediction procedure is presented which yields accurate results in widely dissimilar liquids.

Flow boiling with enhancement devices for cold plate coolant channel design

NASA Technical Reports Server (NTRS)

Boyd, Ronald D., Sr.; Smith, Alvin

1990-01-01

The use of flow boiling for thermal energy transport is intended to provide an alternative for accommodating higher heat fluxes in commercial space systems. The objectives are to: (1) examine the variations in both the mean and local (axial and circumferential) heat transfer coefficients for a circular coolant channel with either smooth walls, spiral fins, or both spiral fins and a twisted tape; (2) examine the effects of channel diameter and subcooling; and (3) develop an improved reduction analysis and/or suggest possible heat transfer correlation of the present data. Freon-11 is the working fluid. Two-dimensional (circumferential and axial) wall temperature distributions were measured for coolant channels with the above noted internal geometries. The flow regimes which are being studied are: (1) single phase; (2) subcooled flow boiling; and (3) stratified flow boiling. The inside diameter of all test sections is near 1.0 cm. Cicumferentially averaged heat transfer coefficients at several axial locations were obtained for selected coolant channels for a mass velocity of 210 kg/sq m s, an exit pressure of 0.19 MPa (absolute), and an inlet subcooling of 20.8 C. Overall (averaged over the entire channel) heat transfer coefficients were compared for the above channel geometries. This comparison showed that the channel with large pitch spiral fins had higher heat transfer coefficients at all power levels.

Lattice Boltzmann modeling of boiling heat transfer: The boiling curve and the effects of wettability

DOE PAGES

Li, Q.; Kang, Q. J.; Francois, M. M.; ...

2015-03-03

A hybrid thermal lattice Boltzmann (LB) model is presented to simulate thermal multiphase flows with phase change based on an improved pseudopotential LB approach (Li et al., 2013). The present model does not suffer from the spurious term caused by the forcing-term effect, which was encountered in some previous thermal LB models for liquid–vapor phase change. Using the model, the liquid–vapor boiling process is simulated. The boiling curve together with the three boiling stages (nucleate boiling, transition boiling, and film boiling) is numerically reproduced in the LB community for the first time. The numerical results show that the basic featuresmore » and the fundamental characteristics of boiling heat transfer are well captured, such as the severe fluctuation of transient heat flux in the transition boiling and the feature that the maximum heat transfer coefficient lies at a lower wall superheat than that of the maximum heat flux. Moreover, the effects of the heating surface wettability on boiling heat transfer are investigated. It is found that an increase in contact angle promotes the onset of boiling but reduces the critical heat flux, and makes the boiling process enter into the film boiling regime at a lower wall superheat, which is consistent with the findings from experimental studies.« less

Prediction of forced convective heat transfer and critical heat flux for subcooled water flowing in miniature tubes

NASA Astrophysics Data System (ADS)

Shibahara, Makoto; Fukuda, Katsuya; Liu, Qiusheng; Hata, Koichi

2018-02-01

The heat transfer characteristics of forced convection for subcooled water in small tubes were clarified using the commercial computational fluid dynamic (CFD) code, PHENICS ver. 2013. The analytical model consists of a platinum tube (the heated section) and a stainless tube (the non-heated section). Since the platinum tube was heated by direct current in the authors' previous experiments, a uniform heat flux with the exponential function was given as a boundary condition in the numerical simulation. Two inner diameters of the tubes were considered: 1.0 and 2.0 mm. The upward flow velocities ranged from 2 to 16 m/s and the inlet temperature ranged from 298 to 343 K. The numerical results showed that the difference between the surface temperature and the bulk temperature was in good agreement with the experimental data at each heat flux. The numerical model was extended to the liquid sublayer analysis for the CHF prediction and was evaluated by comparing its results with the experimental data. It was postulated that the CHF occurs when the fluid temperature near the heated wall exceeds the saturated temperature, based on Celata et al.'s superheated layer vapor replenishment (SLVR) model. The suggested prediction method was in good agreement with the experimental data and with other CHF data in literature within ±25%.

Multiphysics modeling of two-phase film boiling within porous corrosion deposits

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jin, Miaomiao, E-mail: mmjin@mit.edu; Short, Michael, E-mail: hereiam@mit.edu

2016-07-01

Porous corrosion deposits on nuclear fuel cladding, known as CRUD, can cause multiple operational problems in light water reactors (LWRs). CRUD can cause accelerated corrosion of the fuel cladding, increase radiation fields and hence greater exposure risk to plant workers once activated, and induce a downward axial power shift causing an imbalance in core power distribution. In order to facilitate a better understanding of CRUD's effects, such as localized high cladding surface temperatures related to accelerated corrosion rates, we describe an improved, fully-coupled, multiphysics model to simulate heat transfer, chemical reactions and transport, and two-phase fluid flow within these deposits.more » Our new model features a reformed assumption of 2D, two-phase film boiling within the CRUD, correcting earlier models' assumptions of single-phase coolant flow with wick boiling under high heat fluxes. This model helps to better explain observed experimental values of the effective CRUD thermal conductivity. Finally, we propose a more complete set of boiling regimes, or a more detailed mechanism, to explain recent CRUD deposition experiments by suggesting the new concept of double dryout specifically in thick porous media with boiling chimneys. - Highlights: • A two-phase model of CRUD's effects on fuel cladding is developed and improved. • This model eliminates the formerly erroneous assumption of wick boiling. • Higher fuel cladding temperatures are predicted when accounting for two-phase flow. • Double-peaks in thermal conductivity vs. heat flux in experiments are explained. • A “double dryout” mechanism in CRUD is proposed based on the model and experiments.« less

Net vapor generation point in boiling flow of trichlorotrifluoroethane at high pressures

NASA Technical Reports Server (NTRS)

Dougall, R. S.; Lippert, T. E.

1973-01-01

The conditions at which the void in subcooled boiling starts to undergo a rapid increase were studied experimentally. The experiments were performed in a 12.7 x 9.5 mm rectangular channel. Heating was from a 3.2 mm wide strip embedded in one wall. The pressure ranged from 9.45 to 20.7 bar, mass velocity from 600 to 7000 kg/sq m sec, and subcooling from 16 to 67 C. Photographs were used to determine when detached bubbles first appeared in the bulk flow. Measurements of bubble layer thickness along the wall were also made. Results showed that the point of net vapor generation is close to the occurrence of fully-developed boiling.

Technology of forced flow and once-through boiling: A survey. [pressure distribution

NASA Technical Reports Server (NTRS)

Poppendieck, H. F.; Sabin, C. M.

1975-01-01

Representative boiling heat transfer and pressure drop information obtained primarily from past NASA and AEC programs is presented which is applicable to forced flow and once-through boiler systems. The forced convection boiler has a number of advantages: little possibility of flow mal-distribution; heat transfer characteristics are usually consistent; and conductances are predictable, so that higher heat fluxes may be employed with safety (which leads to more compact, lighter weight equipment). It was found that in gas-fired systems particularly, the controlling heat transfer resistance may be on the hot side, so that increased fluxes would require extended surfaces. If in a power generation system the working fluid is very expensive, a forced flow boiler can be designed especially for small holdup volume. If the fluid is temperature sensitive, the boiling side wall temperatures can be tailored to maintain maximum heat transfer rates without overheating the fluid. The forced flow and once-through configurations may be the only type which can satisfy a specific need (such as the automotive Rankine cycle power plant design having a very short time-response boiler).

Boiling heat transfer during flow of distilled water in an asymmetrically heated rectangular minichannel

NASA Astrophysics Data System (ADS)

Strąk, Kinga; Piasecka, Magdalena

This paper discusses test results concerning flow boiling heat transfer in a minichannel 1.7 mm in depth, 16 mm in width and 180 mm in length. The essential part of the experimental stand was a vertically oriented rectangular minichannel, which was heated asymmetrically with a plate made of Haynes-230 alloy. Distilled water was used as the cooling fluid. Changes in the temperature on the outer side of the heated plate in the central, axially symmetric part of the channel were measured using infrared thermography. Simultaneously, the other side of the heated plate in contact with the fluid was observed through a glass pane to identify the two-phase flow patterns. The one-dimensional model used for the heat transfer analysis took into account the heat flow direction, which was perpendicular to the direction of the fluid flow in the minichannel. The study involved determining local values of the heat transfer coefficient and generating boiling curves. The data for water were compared with the findings reported for the FC-72 fluid.

Promoting universal financial protection: a case study of new management of community health insurance in Tanzania

PubMed Central

2013-01-01

Background The National Health Insurance Fund (NHIF), a compulsory formal sector scheme took over the management of the Community Health Fund (CHF), a voluntary informal sector scheme, in 2009. This study assesses the origins of the reform, its effect on management and reporting structures, financial flow adequacy, reform communication and acceptability to key stakeholders, and initial progress towards universal coverage. Methods The study relied on national data sources and an in-depth collective case study of a rural and an urban district to assess awareness and acceptability of the reform, and fund availability and use relative to need in a sample of facilities. Results The reform was driven by a national desire to expand coverage and increase access to services. Despite initial delays, the CHF has been embedded within the NHIF organisational structure, bringing more intensive and qualified supervision closer to the district. National CHF membership has more than doubled. However, awareness of the reform was limited below the district level due to the reform’s top-down nature. The reform was generally acceptable to key stakeholders, who expected that benefits between schemes would be harmonised. The reform was unable to institute changes to the CHF design or district management structures because it has so far been unable to change CHF legislation which also limits facility capacity to use CHF revenue. Further, revenue generated is currently insufficient to offset treatment and administration costs, and the reform did not improve the revenue to cost ratio. Administrative costs are also likely to have increased as a result of the reform. Conclusion Informal sector schemes can benefit from merger with formal sector schemes through improved data systems, supervision, and management support. However, effects will be maximised if legal frameworks can be harmonised early on and a reduction in administrative costs is not guaranteed. PMID:23763711

Analysis of flow reversal test

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, L.Y.; Tichler, P.R.

A series of tests has been conducted to measure the dryout power associated with a flow transient whereby the coolant in a heated channel undergoes a change in flow direction. An analysis of the test was made with the aid of a system code, RELAP5. A dryout criterion was developed in terms of a time-averaged void fraction calculated by RELAP5 for the heated channel. The dryout criterion was also compared with several CHF correlations developed for the channel geometry.

Observations of the boiling process from a downward-facing torispherical surface: Confirmatory testing of the heavy water new production reactor flooded cavity design

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chu, T.Y.; Bentz, J.H.; Simpson, R.B.

1995-06-01

Reactor-scale ex-vessel boiling experiments were performed in the CYBL facility at Sandia National Laboratories. The boiling flow pattern outside the RPV bottom head shows a center pulsating region and an outer steady two-phase boundary layer region. The local heat transfer data can be correlated in terms of a modified Rohsenow correlation.

Feasibility study of a brine boiling machine by solar energy

NASA Astrophysics Data System (ADS)

Phayom, W.

2018-06-01

This study presented the technical and operational feasibility of brine boiling machine by using solar energy instead of firewood or husk for salt production. The solar salt brine boiling machine consisted of a boiling chamber with an enhanced thermal efficiency through use of a solar brine heater. The stainless steel solar salt brine boiling chamber had dimensions of 60 cm x 70 cm x 20 cm. The steel brine heater had dimensions of 70 cm x 80 cm x 20 cm. The tilt angle of both the boiling chamber and brine heater was 20 degrees from horizontal. The brine temperature in the reservoir tank was 42°C with a flow rate of 6.64 L/h discharging into the solar boiling machine. It was found that the thermal efficiency and overall efficiency of the solar salt brine boiling machine were 0.63 and 0.38, respectively at a solar irradiance of 787.6 W/m2. The results shows that the potential of using solar energy for salt production system is feasible.

Experimental Testing and Numerical Modeling of Spray Cooling Under Terrestrial Gravity Conditions

DTIC Science & Technology

2005-01-01

running safely. Mudawar (2000) identifies two heat flux ranges relative to the amount of heat dissipation. The high-flux range includes heat fluxes on...inferior to those of water ( Mudawar , 2000). Phase change cooling can exist in several forms, or cooling schemes. Pool boiling may be used in...addition to reducing the significant effects of flow orientation ( Mudawar , 2000). It is not fully known how low gravity affects flow boiling, as

Bubble Dynamics, Two-Phase Flow, and Boiling Heat Transfer in Microgravity

NASA Technical Reports Server (NTRS)

Chung, Jacob N.

1996-01-01

The objective of the research is to study the feasibility of employing an external force to replace the buoyancy force in order to maintain nucleate boiling in microgravity. We have found that a bulk velocity field, an electric field and an acoustic field could each play the role of the gravity field in microgravity. Nucleate boiling could be maintained by any one of the three external force fields in space.

MSG test report-steady-state heat transfer. [LMFBR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harty, R.B.

This report documents the results of the Steady-State Heat Transfer Tests conducted on the AI Modular Steam Generator (MSG), at the Sodium Component Test Installation (SCTI) of the Liquid Metal Engineering Center. Heat transfer and pressure drop performance data are given along with current predictions of performance. Departure from nucleate boiling characteristics is given. A dispersed flow film boiling model, employing thermal nonequilibrium, was used to analyze data in the film boiling region.

The effect of reduced gravity on cryogenic nitrogen boiling and pipe chilldown.

PubMed

Darr, Samuel; Dong, Jun; Glikin, Neil; Hartwig, Jason; Majumdar, Alok; Leclair, Andre; Chung, Jacob

2016-01-01

Manned deep space exploration will require cryogenic in-space propulsion. Yet, accurate prediction of cryogenic pipe flow boiling heat transfer is lacking, due to the absence of a cohesive reduced gravity data set covering the expected flow and thermodynamic parameter ranges needed to validate cryogenic two-phase heat transfer models. This work provides a wide range of cryogenic chilldown data aboard an aircraft flying parabolic trajectories to simulate reduced gravity. Liquid nitrogen is used to quench a 1.27 cm diameter tube from room temperature. The pressure, temperature, flow rate, and inlet conditions are reported from 10 tests covering liquid Reynolds number from 2,000 to 80,000 and pressures from 80 to 810 kPa. Corresponding terrestrial gravity tests were performed in upward, downward, and horizontal flow configurations to identify gravity and flow direction effects on chilldown. Film boiling heat transfer was lessened by up to 25% in reduced gravity, resulting in longer time and more liquid to quench the pipe to liquid temperatures. Heat transfer was enhanced by increasing the flow rate, and differences between reduced and terrestrial gravity diminished at high flow rates. The new data set will enable the development of accurate and robust heat transfer models of cryogenic pipe chilldown in reduced gravity.

The effect of reduced gravity on cryogenic nitrogen boiling and pipe chilldown

PubMed Central

Darr, Samuel; Dong, Jun; Glikin, Neil; Hartwig, Jason; Majumdar, Alok; Leclair, Andre; Chung, Jacob

2016-01-01

Manned deep space exploration will require cryogenic in-space propulsion. Yet, accurate prediction of cryogenic pipe flow boiling heat transfer is lacking, due to the absence of a cohesive reduced gravity data set covering the expected flow and thermodynamic parameter ranges needed to validate cryogenic two-phase heat transfer models. This work provides a wide range of cryogenic chilldown data aboard an aircraft flying parabolic trajectories to simulate reduced gravity. Liquid nitrogen is used to quench a 1.27 cm diameter tube from room temperature. The pressure, temperature, flow rate, and inlet conditions are reported from 10 tests covering liquid Reynolds number from 2,000 to 80,000 and pressures from 80 to 810 kPa. Corresponding terrestrial gravity tests were performed in upward, downward, and horizontal flow configurations to identify gravity and flow direction effects on chilldown. Film boiling heat transfer was lessened by up to 25% in reduced gravity, resulting in longer time and more liquid to quench the pipe to liquid temperatures. Heat transfer was enhanced by increasing the flow rate, and differences between reduced and terrestrial gravity diminished at high flow rates. The new data set will enable the development of accurate and robust heat transfer models of cryogenic pipe chilldown in reduced gravity. PMID:28725740

NADPH oxidase contributes to coronary endothelial dysfunction in the failing heart.

PubMed

Zhang, Ping; Hou, Mingxiao; Li, Yunfang; Xu, Xin; Barsoum, Michel; Chen, Yingjie; Bache, Robert J

2009-03-01

Increased reactive oxygen species (ROS) produced by the failing heart can react with nitric oxide (NO), thereby decreasing NO bioavailability. This study tested the hypothesis that increased ROS generation contributes to coronary endothelial dysfunction in the failing heart. Congestive heart failure (CHF) was produced in six dogs by ventricular pacing at 240 beats/min for 4 wk. Studies were performed at rest and during treadmill exercise under control conditions and after treatment with the NADPH oxidase inhibitor and antioxidant apocynin (4 mg/kg iv). Apocynin caused no significant changes in heart rate, aortic pressure, left ventricular (LV) systolic pressure, LV end-diastolic pressure, or maximum rate of LV pressure increase at rest or during exercise in normal or CHF dogs. Apocynin caused no change in coronary blood flow (CBF) in normal dogs but increased CBF at rest and during exercise in animals with CHF (P < 0.05). Intracoronary ACh caused dose-dependent increases of CBF that were blunted in CHF. Apocynin had no effect on the response to ACh in normal dogs but augmented the response to ACh in CHF dogs (P < 0.05). The oxidative stress markers nitrotyrosine and 4-hydroxy-2-nonenal were significantly greater in failing than in normal myocardium. Furthermore, coelenterazine chemiluminescence for O(2)(-) was more than twice normal in failing myocardium, and this difference was abolished by apocynin. Western blot analysis of myocardial lysates demonstrated that the p47(phox) and p22(phox) subunits of NADPH were significantly increased in the failing hearts, while real-time PCR demonstrated that Nox2 mRNA was significantly increased. The data indicate that increased ROS generation in the failing heart is associated with coronary endothelial dysfunction and suggest that NADPH oxidase may contribute to this abnormality.

A study of the flow boiling heat transfer in a minichannel for a heated wall with surface texture produced by vibration-assisted laser machining

NASA Astrophysics Data System (ADS)

Piasecka, Magdalena; Strąk, Kinga; Maciejewska, Beata; Grabas, Bogusław

2016-09-01

The paper presents results concerning flow boiling heat transfer in a vertical minichannel with a depth of 1.7 mm and a width of 16 mm. The element responsible for heating FC-72, which flowed laminarly in the minichannel, was a plate with an enhanced surface. Two types of surface textures were considered. Both were produced by vibration-assisted laser machining. Infrared thermography was used to record changes in the temperature on the outer smooth side of the plate. Two-phase flow patterns were observed through a glass pane. The main aim of the study was to analyze how the two types of surface textures affect the heat transfer coefficient. A two-dimensional heat transfer approach was proposed to determine the local values of the heat transfer coefficient. The inverse problem for the heated wall was solved using a semi-analytical method based on the Trefftz functions. The results are presented as relationships between the heat transfer coefficient and the distance along the minichannel length and as boiling curves. The experimental data obtained for the two types of enhanced heated surfaces was compared with the results recorded for the smooth heated surface. The highest local values of the heat transfer coefficient were reported in the saturated boiling region for the plate with the type 1 texture produced by vibration-assisted laser machining.

Heat and momentum transfer model studies applicable to once-through, forced convection potassium boiling

NASA Technical Reports Server (NTRS)

Sabin, C. M.; Poppendiek, H. F.

1971-01-01

A number of heat transfer and fluid flow mechanisms that control once-through, forced convection potassium boiling are studied analytically. The topics discussed are: (1) flow through tubes containing helical wire inserts, (2) motion of droplets entrained in vapor flow, (3) liquid phase distribution in boilers, (4) temperature distributions in boiler tube walls, (5) mechanisms of heat transfer regime change, and (6) heat transfer in boiler tubes. Whenever possible, comparisons of predicted and actual performances are made. The model work presented aids in the prediction of operating characteristics of actual boilers.

Transition from Pool to Flow Boiling: The Effect of Reduced Gravity

NASA Technical Reports Server (NTRS)

Dhir, Vijay K.

2004-01-01

Applications of boiling heat transfer in space can be found in the areas of thermal management, fluid handling and control, power systems, on-orbit storage and supply systems for cryogenic propellants and life support fluids, and for cooling of electronic packages for power systems associated with various instrumentation and control systems. Recent interest in exploration of Mars and other planets, and the concepts of in-situ resource utiliLation on Mars highlights the need to understand the effect of gravity on boiling heat transfer at gravity levels varying from 1>= g/g(sub e) >=10(exp -6). The objective of the proposed work was to develop a mechanistic understanding of nucleate boiling and critical heat flux under low and micro-gravity conditions when the velocity of the imposed flow is small. For pool boiling, the effect of reduced gravity is to stretch both the length scale as well as the time scale for the boiling process. At high flow velocities, the inertia of the liquid determines the time and the length scales and as such the gravitational acceleration plays little role. However, at low velocities and at low gravity levels both liquid inertia and buoyancy are of equal importance. At present, we have little understanding of the interacting roles of gravity and liquid inertia on the nucleate boiling process. Little data that has been reported in the literature does not have much practical value in that it can not serve as a basis for design of heat exchange components to be used in space. Both experimental and complete numerical simulations of the low velocity, low-gravity nucleate boiling process were carried out. A building block type of approach was used in that first the growth and detachment process of a single bubble and flow and heat transfer associated with the sliding motion of the bubble over the heater surface after detachment was studied. Liquid subcooling and flow velocity were varied parametrically. The experiments were conducted at 1 g(sub e), while varying the orientation of surface with respect to the gravity vector. In the laboratory experiments, holographic interferometry was used to obtain data on velocity and temperature fields associated with a bubble prior to, and after detachment and during sliding motion. A test rig for conducting experiments in the KC-135 was developed, but experiments could not be conducted due to the unavailability of the aircraft prior to completion of the project. Numerical simulations modeling the micro and macro regions of the bubble were carried out in three dimensions. The results of the experiments were used to validate analytical/numerical models.

The effect of heating direction on flow boiling heat transfer of R134a in micro-channels

NASA Astrophysics Data System (ADS)

Xu, Mingchen; Jia, Li; Dang, Chao; Peng, Qi

2017-04-01

This paper presents effects of heating directions on heat transfer performance of R134a flow boiling in micro- channel heat sink. The heat sink has 30 parallel rectangular channels with cross-sectional dimensions of 500μm width 500μm depth and 30mm length. The experimental operation condition ranges of the heat flux and the mass flux were 13.48 to 82.25 W/cm2 and 373.3 to 1244.4 kg/m2s respectively. The vapor quality ranged from 0.07 to 0.93. The heat transfer coefficients of top heating and bottom heating both were up to 25 kW/m2 K. Two dominate transfer mechanisms of nucleate boiling and convection boiling were observed according to boiling curves. The experimental results indicated that the heat transfer coefficient of bottom heating was 13.9% higher than top heating in low heat flux, while in high heat flux, the heat transfer coefficient of bottom heating was 9.9%.higher than the top heating, because bubbles were harder to divorce the heating wall. And a modified correlation was provided to predict heat transfer of top heating.

Experimental Study on Flow Boiling of Carbon Dioxide in a Horizontal Microfin Tube

NASA Astrophysics Data System (ADS)

Kuwahara, Ken; Ikeda, Soshi; Koyama, Shigeru

This paper deals with the experimental study on flow boiling heat transfer of carbon dioxide in a micro-fin tube. The geometrical parameters of micro-fin tube used in this study are 6.07 mm in outer diameter, 5.24 mm in average inner diameter, 0.256 mm in fin height, 20.4 in helix angle, 52 in number of grooves and 2.35 in area expansion ratio. Flow patterns and heat transfer coefficients were measured at 3-5 MPa in pressure, 300-540 kg/(m2s) in mass velocity and -5 to 15 °C in CO2 temperature. Flow patterns of wavy flow, slug flow and annular flow were observed. The measured heat transfer coefficients of micro-fin tube were 10-40 kW/(m2K). Heat transfer coefficients were strongly influenced by pressure.

A model for fluid flow during saturated boiling on a horizontal cylinder

NASA Technical Reports Server (NTRS)

Kheyrandish, K.; Dalton, C.; Lienhard, J. H.

1987-01-01

A model has been developed to represent the vapor removal pattern in the vicinity of a cylinder during nucleate flow boiling across a horizontal cylinder. The model is based on a potential flow representation of the liquid and vapor regions and an estimate of the losses that should occur in the flow. Correlation of the losses shows a weak dependence on the Weber number and a slightly stronger dependence on the saturated liquid-to-vapor density ratio. The vapor jet thickness, which is crucial to the prediction of the burnout heat flux, and the shape of the vapor film are predicted. Both are verified by qualitative experimental observations.

Inequitable provision of optimal services for patients with chronic heart failure: a national geo-mapping study.

PubMed

Clark, Robyn A; Driscoll, Andrea; Nottage, Justin; McLennan, Skye; Coombe, David M; Bamford, Errol J; Wilkinson, David; Stewart, Simon

2007-02-19

To compare the location and accessibility of current Australian chronic heart failure (CHF) management programs and general practice services with the probable distribution of the population with CHF. Data on the prevalence and distribution of the CHF population throughout Australia, and the locations of CHF management programs and general practice services from 1 January 2004 to 31 December 2005 were analysed using geographic information systems (GIS) technology. Distance of populations with CHF to CHF management programs and general practice services. The highest prevalence of CHF (20.3-79.8 per 1000 population) occurred in areas with high concentrations of people over 65 years of age and in areas with higher proportions of Indigenous people. Five thousand CHF patients (8%) discharged from hospital in 2004-2005 were managed in one of the 62 identified CHF management programs. There were no CHF management programs in the Northern Territory or Tasmania. Only four CHF management programs were located outside major cities, with a total case load of 80 patients (0.7%). The mean distance from any Australian population centre to the nearest CHF management program was 332 km (median, 163 km; range, 0.15-3246 km). In rural areas, where the burden of CHF management falls upon general practitioners, the mean distance to general practice services was 37 km (median, 20 km; range, 0-656 km). There is an inequity in the provision of CHF management programs to rural Australians.

Single-bubble boiling under Earth's and low gravity

NASA Astrophysics Data System (ADS)

Khusid, Boris; Elele, Ezinwa; Lei, Qian; Tang, John; Shen, Yueyang

2017-11-01

Miniaturization of electronic systems in terrestrial and space applications is challenged by a dramatic increase in the power dissipation per unit volume with the occurrence of localized hot spots where the heat flux is much higher than the average. Cooling by forced gas or liquid flow appears insufficient to remove high local heat fluxes. Boiling that involves evaporation of liquid in a hot spot and condensation of vapor in a cold region can remove a significantly larger amount of heat through the latent heat of vaporization than force-flow cooling can carry out. Traditional methods for enhancing boiling heat transfer in terrestrial and space applications focus on removal of bubbles from the heating surface. In contrast, we unexpectedly observed a new boiling regime of water under Earth's gravity and low gravity in which a bubble was pinned on a small heater up to 270°C and delivered a heat flux up to 1.2 MW/m2 that was as high as the critical heat flux in the classical boiling regime on Earth .Low gravity measurements conducted in parabolic flights in NASA Boeing 727. The heat flux in flight and Earth's experiments was found to rise linearly with increasing the heater temperature. We will discuss physical mechanisms underlying heat transfer in single-bubble boiling. The work supported by NASA Grants NNX12AM26G and NNX09AK06G.

TRACE/PARCS Analysis of ATWS with Instability for a MELLLA+BWR/5

DOE PAGES

L. Y. Cheng; Baek, J. S.; Cuadra, A.; ...

2016-06-06

A TRACE/PARCS model has been developed to analyze anticipated transient without SCRAM (ATWS) events for a boiling water reactor (BWR) operating in the maximum extended load line limit analysis-plus (MELLLA+) expanded operating domain. The MELLLA+ domain expands allowable operation in the power/flow map of a BWR to low flow rates at high power conditions. Such operation exacerbates the likelihood of large amplitude power/flow oscillations during certain ATWS scenarios. The analysis shows that large amplitude power/flow oscillations, both core-wide and out-of-phase, arise following the establishment of natural circulation flow in the reactor pressure vessel (RPV) after the trip of the recirculationmore » pumps and an increase in core inlet subcooling. The analysis also indicates a mechanism by which the fuel may experience heat-up that could result in localized fuel damage. TRACE predicts the heat-up to occur when the cladding surface temperature exceeds the minimum stable film boiling temperature after periodic cycles of dryout and rewet; and the fuel becomes “locked” into a film boiling regime. Further, the analysis demonstrates the effectiveness of the simulated manual operator actions to suppress the instability.« less

Performance Evaluation of the International Space Station Flow Boiling and Condensation Experiment (FBCE) Test Facility

NASA Technical Reports Server (NTRS)

Hasan, Mohammad; Balasubramaniam, R.; Nahra, Henry; Mackey, Jeff; Hall, Nancy; Frankenfield, Bruce; Harpster, George; May, Rochelle; Mudawar, Issam; Kharangate, Chirag R.;

Study of Critical Heat Flux and Two-Phase Pressure Drop Under Reduced Gravity

NASA Technical Reports Server (NTRS)

Abdollahian, Davood; Quintal, Joseph; Barez, Fred; Zahm, Jennifer; Lohr, Victor

1996-01-01

The design of the two-phase flow systems which are anticipated to be utilized in future spacecraft thermal management systems requires a knowledge of two-phase flow and heat transfer phenomena in reduced gravities. This program was funded by NASA headquarters in response to NRA-91-OSSA-17 and was managed by Lewis Research Center. The main objective of this program was to design and construct a two-phase test loop, and perform a series of normal gravity and aircraft trajectory experiments to study the effect of gravity on the Critical Heat Flux (CHF) and onset of instability. The test loop was packaged on two aircraft racks and was also instrumented to generate data for two-phase pressure drop. The normal gravity tests were performed with vertical up and downflow configurations to bound the effect of gravity on the test parameters. One set of aircraft trajectory tests was performed aboard the NASA DC-9 aircraft. These tests were mainly intended to evaluate the test loop and its operational performance under actual reduced gravity conditions, and to produce preliminary data for the test parameters. The test results were used to demonstrate the applicability of the normal gravity models for prediction of the two-phase friction pressure drop. It was shown that the two-phase friction multipliers for vertical upflow and reduced gravity conditions can be successfully predicted by the appropriate normal gravity models. Limited critical heat flux data showed that the measured CHF under reduced gravities are of the same order of magnitude as the test results with vertical upflow configuration. A simplified correlation was only successful in predicting the measured CHF for low flow rates. Instability tests with vertical upflow showed that flow becomes unstable and critical heat flux occurs at smaller powers when a parallel flow path exists. However, downflow tests and a single reduced gravity instability experiment indicated that the system actually became more stable with a parallel single-phase flow path. Several design modifications have been identified which will improve the system performance for generating reduced gravity data. The modified test loop can provide two-phase flow data for a range of operating conditions and can serve as a test bed for component evaluation.

Comparative study of flow condensation in conventional and small diameter tubes

NASA Astrophysics Data System (ADS)

Mikielewicz, Dariusz; Andrzejczyk, Rafał

2012-10-01

Flow boiling and flow condensation are often regarded as two opposite or symmetrical phenomena. Their description however with a single correlation has yet to be suggested. In the case of flow boiling in minichannels there is mostly encountered the annular flow structure, where the bubble generation is not present. Similar picture holds for the case of inside tube condensation, where annular flow structure predominates. In such case the heat transfer coefficient is primarily dependent on the convective mechanism. In the paper a method developed earlier by the first author is applied to calculations of heat transfer coefficient for inside tube condensation. The method has been verified using experimental data from literature on several fluids in different microchannels and compared to three well established correlations for calculations of heat transfer coefficient in flow condensation. It clearly stems from the results presented here that the flow condensation can be modeled in terms of appropriately devised pressure drop.

Congestive heart failure in children with pneumonia and respiratory failure.

PubMed

Nimdet, Kachaporn; Techakehakij, Win

2017-03-01

Congestive heart failure (CHF) is one of the most common cardiac complications of pneumonia in adulthood leading to increased risk of morbidity and mortality. Little is known, however, of CHF and pneumonia in children. The aim of this study was therefore to investigate the characteristics and factors associated with CHF in under-5 children with pneumonia and respiratory failure. A retrospective cohort was conducted in hospitalized patients aged 2-59 months with community-acquired pneumonia and respiratory failure from June 2011 to June 2014 at Suratthani Hospital, Thailand. The characteristics, therapeutic strategy, and clinical outcomes of CHF were reviewed. Baseline characteristics and basic laboratory investigations on admission were compared between the CHF and non-CHF groups. Of 135 patients, 14 (10%) had CHF. Compared with patients without CHF, the CHF group had prolonged intubation and hospital stay and high rates of associated complications such as ventilator-associated pneumonia, sepsis, shock, and 30 day mortality. CHF was significantly associated with certain characteristics, including male sex and bacterial pneumonia. Pneumonia with respiratory failure is associated with CHF even in healthy children without cardiac risks. The awareness and early recognition of CHF, particularly in male, and bacterial pneumonia, is important in order to provide immediate treatment to reduce complications. © 2016 Japan Pediatric Society.

An experimental study of the flow boiling of refrigerant-based nanofluids

NASA Astrophysics Data System (ADS)

Kolekar, Rahul Dadasaheb

The use of nanofluids for various heat transfer applications has been a topic of intense research over the last decade. A number of studies to evaluate the thermophysical properties and single-phase heat transfer behavior of nanofluids have been reported. The current study is focused on the use of nanofluids in flow boiling applications, with CO2 and R134a used as the base refrigerants. CuO nanoparticles 40nm in size, and TiO2 nanoparticles 200nm in size are used to create partially stable CO2-based nanofluids. Stable nanofluids are created in R134a by mixing it with dispersions of surface-treated nanoparticles in polyolester (POE) oil (RL22H and RL68H). The particles (Al 2O3, ZnO, CuO, and ATO) at particle mass fractions from 0.08% to 1.34%, with particle sizes of 20nm and 40nm are coated with polar and non-polar surface treatments. The thermal properties of R134a-based nanofluids are measured. Thermal conductivity shows limited improvements; the largest increase of 13% is observed with CuO nanoparticles. Significant increases in viscosity, as high as 2147%, are observed due to CuO nanoparticles. Only the ATO nanofluid exhibited a decrease in the measured viscosity. Heat transfer coefficients during flow boiling of nanofluids are measured over a range of mass flux from 100 to 1000 kg/m2s, with a heat flux from 5 to 25kW/m2, and vapor quality up to 1. The test section is a smooth copper tube, 6.23mm in diameter and 1.8m in length. Average decreases of 5% and 28% are observed in heat transfer coefficients during flow boiling of CuO/CO2 and TiO2/CO2 nanofluids, respectively. For the R134a-based nanofluids, average decreases in heat transfer during flow boiling at the highest particle mass fraction are 15% and 22% for Al2O3 and ZnO nanoparticles, respectively. CuO nanoparticles exhibit an average decrease of 7% for particle mass fraction of 0.08%. An average increase of 10% is observed with ATO nanoparticles at a 0.22% mass fraction. Heat transfer performance deteriorates with increase in viscosity and particle number density. The performance is also worse for partially stable nanofluids that modify the test section surface. Modifications to the thermophysical properties is the primary mechanism that affects heat transfer performance during flow boiling of nanofluids; increased thermal conductivity enhances while increased viscosity and surface tension reduce heat transfer in nucleate boiling-dominated flows. A secondary mechanism of nanoparticles filling up the micro-cavities on test surface is also responsible for decreased heat transfer and is a strong function of particle number density.

20. RW Meyer Sugar Mill: 18761889. Boiling House Interior, 1878. ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

20. RW Meyer Sugar Mill: 1876-1889. Boiling House Interior, 1878. View: Remains of south wall. The molasses storage pits are below the floor in the foreground. The remaining piece of floor indicates the form of the entire floor. The sorghum pan and boiling range flue slope from left to right (east to west) and permitted batches of cane juice to flow through the boiling pan by gravity. The beams, joists, truss work are built of northwest pine. The sides and floor boards are built of redwood. The boiling range flue is built of fire-brick, masonry, and portland cement. The corrugated roof appears to be a later addition, not contemporary with mill operation. - R. W. Meyer Sugar Mill, State Route 47, Kualapuu, Maui County, HI

CONTINUOUS ANALYZER UTILIZING BOILING POINT DETERMINATION

DOEpatents

Pappas, W.S.

1963-03-19

A device is designed for continuously determining the boiling point of a mixture of liquids. The device comprises a distillation chamber for boiling a liquid; outlet conduit means for maintaining the liquid contents of said chamber at a constant level; a reflux condenser mounted above said distillation chamber; means for continuously introducing an incoming liquid sample into said reflux condenser and into intimate contact with vapors refluxing within said condenser; and means for measuring the temperature of the liquid flowing through said distillation chamber. (AEC)

Zero Boil-Off Tank (ZBOT) Experiment

NASA Technical Reports Server (NTRS)

Mcquillen, John

2016-01-01

The Zero-Boil-Off Tank (ZBOT) experiment has been developed as a small scale ISS experiment aimed at delineating important fluid flow, heat and mass transport, and phase change phenomena that affect cryogenic storage tank pressurization and pressure control in microgravity. The experiments use a simulant transparent low boiling point fluid (PnP) in a sealed transparent Dewar to study and quantify: (a) fluid flow and thermal stratification during pressurization; (b) mixing, thermal destratification, depressurization, and jet-ullage penetration during pressure control by jet mixing. The experiment will provide valuable microgravity empirical two-phase data associated with the above-mentioned physical phenomena through highly accurate local wall and fluid temperature and pressure measurements, full-field phase-distribution and flow visualization. Moreover, the experiments are performed under tightly controlled and definable heat transfer boundary conditions to provide reliable high-fidelity data and precise input as required for validation verification of state-of-the-art two-phase CFD models developed as part of this research and by other groups in the international scientific and cryogenic fluid management communities.

Development and Capabilities of ISS Flow Boiling and Condensation Experiment

NASA Technical Reports Server (NTRS)

Nahra, Henry; Hasan, Mohammad; Balasubramaniam, R.; Patania, Michelle; Hall, Nancy; Wagner, James; Mackey, Jeffrey; Frankenfield, Bruce; Hauser, Daniel; Harpster, George;

Experimental analysis of refrigerants flow boiling inside small sized microfin tubes

NASA Astrophysics Data System (ADS)

Diani, Andrea; Rossetto, Luisa

2017-07-01

The refrigerant charge reduction is one of the most challenging issues that the scientific community has to cope to reduce the anthropic global warming. Recently, mini microfin tubes have been matter of research, since they can reach better thermal performance in small domains, leading to a further refrigerant charge reduction. This paper presents experimental results about R134a flow boiling inside a microfin tube having an internal diameter at the fin tip of 2.4 mm. The mass flux was varied between 375 and 940 kg m-2 s-1, heat flux from 10 to 50 kW m-2, vapor quality from 0.10 to 0.99. The saturation temperature at the inlet of the test section was kept constant and equal to 30 °C. R134a thermal and fluid dynamic performances are presented and compared against those obtained with R1234ze(E) and R1234yf and against values obtained during R134a flow boiling inside a 3.4 mm ID microfin tube.

Prevalence of Heart Failure and Adherence to Process Indicators: Which Socio-Demographic Determinants are Involved?

PubMed Central

Buja, Alessandra; Solinas, Giuliana; Visca, Modesta; Federico, Bruno; Gini, Rosa; Baldo, Vincenzo; Francesconi, Paolo; Sartor, Gino; Bellentani, Mariadonata; Damiani, Gianfranco

2016-01-01

Interest in chronic conditions reflects their role as the first cause of death and disability in developed countries; improving the management of these conditions is a priority for health care services. The aim of this study was to establish which sociodemographic factors influence adherence to standards of care for chronic heart failure (CHF). A generalized multilevel structural equation model was developed and applied to a sample of patients with CHF obtained from administrative data flows in six Italian regions to ascertain any associations between adherence to standards of care for CHF and sociodemographic variables. Indicators of compliance were adherence to beta-blocker therapy (BB-A) and Angiotensin Convertin Enzime inhibitor/Angiotensin Receptor Blocker therapy (ACE-A), and creatinine and electrolyte testing (CNK-T). All indicators were computed over a one-year follow-up. Among a cohort of 24,997 patients, the BB-A rate was 40.4%, the ACE-A rate 61.1%, and the CNK-T rate 57.0%. Factors found associated with adherence were gender, age, and citizenship. Our study shows an inadequate adherence to standards of care for CHF, particularly associated with certain sociodemographic characteristics. This suggests the need to improve the role of primary care in managing this chronic condition. The measures considered only apply to patients with a reduced Left Ventricular Ejection Fraction, hence a limitation of this analysis is the lack of information on left ventricular ejection. PMID:26907316

The physiological basis of rehabilitation in chronic heart and lung disease.

PubMed

Vogiatzis, Ioannis; Zakynthinos, Spyros

2013-07-01

Cardiopulmonary rehabilitation is recognized as a core component of management of individuals with congestive heart failure (CHF) or chronic obstructive pulmonary disease (COPD) that is designed to improve their physical and psychosocial condition without impacting on the primary organ impairment. This has lead the scientific community increasingly to believe that the main effects of cardiopulmonary rehabilitative exercise training are focused on skeletal muscles that are regarded as dysfunctional in both CHF and COPD. Accordingly, following completion of a cardiopulmonary rehabilitative exercise training program there are important peripheral muscular adaptations in both disease entities, namely increased capillary density, blood flow, mitochondrial volume density, fiber size, distribution of slow twitch fibers, and decreased lactic acidosis and vascular resistance. Decreased lactic acidosis at a given level of submaximal exercise not only offsets the occurrence of peripheral muscle fatigue, leading to muscle task failure and muscle discomfort, but also concurrently mitigates the additional burden on the respiratory muscles caused by the increased respiratory drive, thereby reducing dyspnea sensations. Furthermore in patients with COPD, exercise training reduces the degree of dynamic lung hyperinflation leading to improved arterial oxygen content and central hemodynamic responses, thus increasing systemic muscle oxygen availability. In patients with CHF, exercise training has beneficial direct and reflex sympathoinhibitory effects and favorable effects on normalization of neurohumoral excitation. These physiological benefits apply to all COPD and CHF patients independently of the degree of disease severity and are associated with improved exercise tolerance, functional capacity, and quality of life.

New Departure from Nucleate Boiling model relying on first principle energy balance at the boiling surface

NASA Astrophysics Data System (ADS)

Demarly, Etienne; Baglietto, Emilio

2017-11-01

Predictions of Departure from Nucleate Boiling have been a longstanding challenge when designing heat exchangers such as boilers or nuclear reactors. Many mechanistic models have been postulated over more than 50 years in order to explain this phenomenon but none is able to predict accurately the conditions which trigger the sudden change of heat transfer mode. This work aims at demonstrating the pertinence of a new approach for detecting DNB by leveraging recent experimental insights. The new model proposed departs from all the previous models by making the DNB inception come from an energy balance instability at the heating surface rather than a hydrodynamic instability of the bubbly layer above the surface (Zuber, 1959). The main idea is to modulate the amount of heat flux being exchanged via the nucleate boiling mechanism by the wetted area fraction on the surface, thus allowing a completely automatic trigger of DNB that doesn't require any parameter prescription. This approach is implemented as a surrogate model in MATLAB in order to validate the principles of the model in a simple and controlled geometry. Good agreement is found with the experimental data leveraged from the MIT Flow Boiling at various flow regimes. Consortium for Advanced Simulation of Light Water Reactors (CASL).

Contribution of peripheral and central chemoreceptors to sympatho‐excitation in heart failure

PubMed Central

Toledo, Camilo; Andrade, David C.; Lucero, Claudia; Schultz, Harold D.; Marcus, Noah; Retamal, Mauricio; Madrid, Carlos

2016-01-01

Abstract Chronic heart failure (CHF) is a major public health problem. Tonic hyper‐activation of sympathetic neural outflow is commonly observed in patients with CHF. Importantly, sympatho‐excitation in CHF exacerbates its progression and is strongly related to poor prognosis and high mortality risk. Increases in both peripheral and central chemoreflex drive are considered markers of the severity of CHF. The principal peripheral chemoreceptors are the carotid bodies (CBs) and alteration in their function has been described in CHF. Mainly, during CHF the CB chemosensitivity is enhanced leading to increases in ventilation and sympathetic outflow. In addition to peripheral control of breathing, central chemoreceptors (CCs) are considered a dominant mechanism in ventilatory regulation. Potentiation of the ventilatory and sympathetic drive in response to CC activation has been shown in patients with CHF as well as in animal models. Therefore, improving understanding of the contribution of the peripheral and central chemoreflexes to augmented sympathetic discharge in CHF could help in developing new therapeutic approaches intended to attenuate the progression of CHF. Accordingly, the main focus of this review is to discuss recent evidence that peripheral and central chemoreflex function are altered in CHF and that they contribute to autonomic imbalance and progression of CHF. PMID:27218485

Prevention of relapse in patients with congestive heart failure: the role of precipitating factors

PubMed Central

Feenstra, J; Grobbee, D; Jonkman, F; Hoes, A; Stricker, B

1998-01-01

Relapse of congestive heart failure (CHF) frequently occurs and has serious consequences in terms of morbidity, mortality, and health care expenditure. Many studies have investigated the aetiological and prognostic factors of CHF, but there are only limited data on the role of precipitating factors that trigger relapse of CHF. Knowledge of potential precipitating factors may help to optimise treatment and provide guidance for patients with CHF. The literature was reviewed to identify factors that may influence haemodynamic homeostasis in CHF. Precipitating factors that may offer opportunities for preventing relapse of CHF were selected. Potential precipitating factors are discussed in relation to the pathophysiology of CHF: alcohol, smoking, psychological stress, uncontrolled hypertension, cardiac arrhythmias, myocardial ischaemia, poor treatment compliance, and inappropriate medical treatment. Poor treatment compliance in particular is frequently encountered in patients with CHF. Furthermore, studies of medical treatment under everyday circumstances indicate that some aspects of the management of CHF can be improved. In conclusion, the identification of precipitating factors for relapse of CHF may strongly contribute to optimal treatment. Improvement of treatment compliance and optimalisation of medical treatment may offer important possibilities to clinicians to reduce the number of relapses in patients with CHF.

 Keywords: congestive heart failure;  precipitating factors;  prevention PMID:9930039

NLP based congestive heart failure case finding: A prospective analysis on statewide electronic medical records.

PubMed

Wang, Yue; Luo, Jin; Hao, Shiying; Xu, Haihua; Shin, Andrew Young; Jin, Bo; Liu, Rui; Deng, Xiaohong; Wang, Lijuan; Zheng, Le; Zhao, Yifan; Zhu, Chunqing; Hu, Zhongkai; Fu, Changlin; Hao, Yanpeng; Zhao, Yingzhen; Jiang, Yunliang; Dai, Dorothy; Culver, Devore S; Alfreds, Shaun T; Todd, Rogow; Stearns, Frank; Sylvester, Karl G; Widen, Eric; Ling, Xuefeng B

2015-12-01

In order to proactively manage congestive heart failure (CHF) patients, an effective CHF case finding algorithm is required to process both structured and unstructured electronic medical records (EMR) to allow complementary and cost-efficient identification of CHF patients. We set to identify CHF cases from both EMR codified and natural language processing (NLP) found cases. Using narrative clinical notes from all Maine Health Information Exchange (HIE) patients, the NLP case finding algorithm was retrospectively (July 1, 2012-June 30, 2013) developed with a random subset of HIE associated facilities, and blind-tested with the remaining facilities. The NLP based method was integrated into a live HIE population exploration system and validated prospectively (July 1, 2013-June 30, 2014). Total of 18,295 codified CHF patients were included in Maine HIE. Among the 253,803 subjects without CHF codings, our case finding algorithm prospectively identified 2411 uncodified CHF cases. The positive predictive value (PPV) is 0.914, and 70.1% of these 2411 cases were found to be with CHF histories in the clinical notes. A CHF case finding algorithm was developed, tested and prospectively validated. The successful integration of the CHF case findings algorithm into the Maine HIE live system is expected to improve the Maine CHF care. Copyright © 2015. Published by Elsevier Ireland Ltd.

Frequent coexistence of chronic heart failure and chronic obstructive pulmonary disease in respiratory and cardiac outpatients: Evidence from SUSPIRIUM, a multicentre Italian survey.

PubMed

Griffo, Raffaele; Spanevello, Antonio; Temporelli, Pier Luigi; Faggiano, Pompilio; Carone, Mauro; Magni, Giovanna; Ambrosino, Nicolino; Tavazzi, Luigi

2017-04-01

Background Chronic heart failure (CHF) and chronic obstructive pulmonary disease (COPD) frequently coexist but concurrent COPD + CHF has been little investigated. Design This multicentre survey (SUSPIRIUM) was designed to evaluate: the prevalence of COPD in stable CHF and CHF in stable COPD; diagnostic/therapeutic work-up for concurrent COPD + CHF; clinical profile of patients with COPD + CHF; predictors of COPD in CHF and CHF in COPD. Methods A 5-month-long cross-sectional prospective observational survey was conducted in 10 cardiac and 10 respiratory connected outpatient units. Results The prevalence of CHF in the 378 surveyed COPD patients was 11.9% (95% confidence interval 8.8-16.6) and the prevalence of COPD in 375 CHF patients was 31.5% (95% confidence interval 26.8-36.4). Diagnostic tests for suspected comorbidity were prescribed in 21.6% and 22.9% of COPD and CHF patients, respectively. Patients with coexisting CHF + COPD had a higher incidence of hypertension, physical inactivity and more frequently a GOLD score of 3 or greater. Compared to CHF only, CHF + COPD patients were significantly older, more frequently smokers, at worse respiratory risk and in a higher New York Heart Association class. Conversely, hypercholesterolaemia, a family history of ischaemic heart disease, fluid retention and comorbidities were more frequent in COPD + CHF than COPD-only patients. At multivariate analysis, a GOLD score of 3 or greater in CHF strongly predicted coexistent COPD (odds ratio 8.985, P < 0.0001) as did a history of other respiratory diseases (5.184, P < 0.0001). A history of ischaemic heart disease (4.868, P < 0.0001), atrial fibrillation (3.302, P < 0.0001) and sedentary lifestyle (2.814, P < 0.004) predicted coexistent CHF in COPD. Conclusion The high prevalence of COPD + CHF calls for integrated disease management between cardiologists and pulmonologists. SUSPIRIUM identifies which cardiac/pulmonary outpatients should be screened for the respective comorbidity.

Prescription of cardiovascular drugs in the French ODIN cohort of heart failure patients according to age and type of chronic heart failure.

PubMed

Juillière, Yves; Suty-Selton, Christine; Riant, Elisabeth; Darracq, Jean-Pierre; Dellinger, Arnaud; Labarre, Jean-Philippe; Druelle, Justine; Mulak, Geneviève; Danchin, Nicolas; Jourdain, Patrick

2014-01-01

Chronic heart failure (CHF) is a frequent severe disease. Disease-management programmes, which contain a therapeutic patient education component, will play a central role in improving delivery of care and reducing mortality and hospitalizations for CHF. In order to have an up-to-date overview of medical treatment of CHF in France implemented by hospital and clinic cardiologists especially interested in CHF and therapeutic patient education, we described the prescription of cardiovascular drugs in the large ODIN cohort of CHF patients, according to age and type of CHF. From 2007 to 2010 (median follow-up 27.2 months), CHF patients were prospectively enrolled in a multicentre 'real-world' French cohort by centres previously trained in therapeutic patient education. Patients were grouped according to age (< 60 years, 60 to<70 years, 70 to<80 years and ≥ 80 years) and type of CHF (characterized by level of LVEF: reduced, borderline or preserved). Medical prescription was described and mortality was assessed at long-term follow-up. The cohort consisted of 3237 patients (67.6 years; 69.4% men). The oldest age group had the highest LVEF. Blockers of the angiotensin-aldosterone system were prescribed progressively and significantly less frequently as the population advanced in age or as LVEF was more preserved. The mean dosages of the main prescribed CHF drugs remained ≥ 50% lower than those recommended for most drugs in all age and LVEF groups. Drug prescriptions were related to aetiology of reduced or preserved CHF. A global decrease in CHF drug prescription was observed for all medication classes except calcium blockers, according to maintenance of relatively or totally preserved LVEF. Survival was related to age but not to type of CHF. In CHF, and despite management by cardiologists particularly interested in CHF and specifically trained to deliver therapeutic patient education, medical prescription differed substantially from guidelines. Age and type of CHF (reduced versus preserved) appeared to be important factors in lack of adherence to guidelines. However, only age influenced mortality; the type of CHF did not affect survival. Copyright © 2013 Elsevier Masson SAS. All rights reserved.

Experimental Study on Flow Boiling of Deionized Water in a Horizontal Long Small Channel

NASA Astrophysics Data System (ADS)

Huang, Qian; Jia, Li; Dang, Chao; Yang, Lixin

2018-04-01

In this paper, an experimental investigation on the flow boiling heat transfer in a horizontal long mini-channel was carried out. The mini-channel was with 2 mm wide and 1 mm deep and 900 mm long. The material of the mini-channel was stainless. The working fluid was deionized water. The experiments were conducted with the conditions of inlet pressure in the range of 0.2 0.5 MPa, mass flux in the range of 196.57-548.96 kg/m2s, and the outlet vapor quality in the range of 0.2 to 1. The heat flux was in the range of 292.86 kW/m2 to 788.48 kW/m2, respectively. The influences of mass flux and heat flux were studied. At a certain mass flow rate, the local heat transfer coefficient increased with the increase of the heat flux. If dry-out occurred in the mini-channel, the heat transfer coefficient decreased. At the same heat flux, the local heat transfer coefficient would depend on the mass flux. It would increase with the mass flux in a certain range, and then decrease if the mass flux was beyond this range. Experimental data were compared with the results of previous studies. Flow visualization and measurements were conducted to identify flow regime transitions. Results showed that there were eight different kinds of flow patterns occurring during the flow boiling. It was found that flow pattern had a significant effect on heat transfer.

Definition of hydraulic stability of KVGM-100 hot-water boiler and minimum water flow rate

NASA Astrophysics Data System (ADS)

Belov, A. A.; Ozerov, A. N.; Usikov, N. V.; Shkondin, I. A.

2016-08-01

In domestic power engineering, the methods of quantitative and qualitative-quantitative adjusting the load of the heat supply systems are widely distributed; furthermore, during the greater part of the heating period, the actual discharge of network water is less than estimated values when changing to quantitative adjustment. Hence, the hydraulic circuits of hot-water boilers should ensure the water velocities, minimizing the scale formation and excluding the formation of stagnant zones. The results of the calculations of hot-water KVGM-100 boiler and minimum water flow rate for the basic and peak modes at the fulfillment of condition of the lack of surface boil are presented in the article. The minimal flow rates of water at its underheating to the saturation state and the thermal flows in the furnace chamber were defined. The boiler hydraulic calculation was performed using the "Hydraulic" program, and the analysis of permissible and actual velocities of the water movement in the pipes of the heating surfaces was carried out. Based on the thermal calculations of furnace chamber and thermal- hydraulic calculations of heating surfaces, the following conclusions were drawn: the minimum velocity of water movement (by condition of boiling surface) at lifting movement of environment increases from 0.64 to 0.79 m/s; it increases from 1.14 to 1.38 m/s at down movement of environmental; the minimum water flow rate by the boiler in the basic mode (by condition of the surface boiling) increased from 887 t/h at the load of 20% up to 1074 t/h at the load of 100%. The minimum flow rate is 1074 t/h at nominal load and is achieved at the pressure at the boiler outlet equal to 1.1 MPa; the minimum water flow rate by the boiler in the peak mode by condition of surface boiling increases from 1669 t/h at the load of 20% up to 2021 t/h at the load of 100%.

Estimating surface temperature in forced convection nucleate boiling - A simplified method

NASA Technical Reports Server (NTRS)

Hendricks, R. C.; Papell, S. S.

1977-01-01

A simplified expression to estimate surface temperatures in forced convection boiling was developed using a liquid nitrogen data base. Using the principal of corresponding states and the Kutateladze relation for maximum pool boiling heat flux, the expression was normalized for use with other fluids. The expression was applied also to neon and water. For the neon data base, the agreement was acceptable with the exclusion of one set suspected to be in the transition boiling regime. For the water data base at reduced pressure greater than 0.05 the agreement is generally good. At lower reduced pressures, the water data scatter and the calculated temperature becomes a function of flow rate.

Ares I Reaction Control System Propellant Feedline Decontamination Modeling

NASA Technical Reports Server (NTRS)

Pasch, James J.

2010-01-01

The objective of the work presented here is to quantify the effects of purge gas temperature, pressure, and mass flow rate on Hydrazine (Hz) decontamination rates of the Ares I Roll Control System and Reaction Control System. A survey of experts in this field revealed the absence of any decontamination rate prediction models. Three basic decontamination methods were identified for analysis and modeling. These include low pressure eduction, high flow rate purge, and pulse purge. For each method, an approach to predict the Hz mass transfer rate, as a function of system pressure, temperature, and purge gas mass flow rate, is developed based on the applicable physics. The models show that low pressure eduction is two orders of magnitude more effective than the high velocity purge, which in turn is two orders of magnitude more effective than the pure diffusion component of pulse purging of deadheads. Eduction subjects the system to low pressure conditions that promote the extraction of Hz vapors. At 120 F, Hz is saturated at approximately 1 psia. At lower pressures and 120 F, Hz will boil, which is an extremely efficient means to remove liquid Hz. The Hz boiling rate is predicted by equating the rate at which energy is added to the saturated liquid Hz through heaters at the tube outer wall with the energy removed from the liquid through evaporation. Boil-off fluxes were predicted by iterating through the range of local pressures with limits set by the minimum allowed pressure of 0.2 psia and maximum allowed wall temperature of 120 F established by the heaters, which gives a saturation pressure of approximately 1.0 psia. Figure 1 shows the resulting boil-off fluxes as a function of local eduction pressure. As depicted in figure 1, the flux is a strong inverse function of eduction pressure, and that minimizing the eduction pressure maximizes the boil-off flux. Also, higher outer wall temperatures lead to higher boil-off fluxes and allow for boil-off over a greater range of eduction pressures.

Gravity Effects in Microgap Flow Boiling

NASA Technical Reports Server (NTRS)

Robinson, Franklin; Bar-Cohen, Avram

2017-01-01

Increasing integration density of electronic components has exacerbated the thermal management challenges facing electronic system developers. The high power, heat flux, and volumetric heat generation of emerging devices are driving the transition from remote cooling, which relies on conduction and spreading, to embedded cooling, which facilitates direct contact between the heat-generating device and coolant flow. Microgap coolers employ the forced flow of dielectric fluids undergoing phase change in a heated channel between devices. While two phase microcoolers are used routinely in ground-based systems, the lack of acceptable models and correlations for microgravity operation has limited their use for spacecraft thermal management. Previous research has revealed that gravitational acceleration plays a diminishing role as the channel diameter shrinks, but there is considerable variation among the proposed gravity-insensitive channel dimensions and minimal research on rectangular ducts. Reliable criteria for achieving gravity-insensitive flow boiling performance would enable spaceflight systems to exploit this powerful thermal management technique and reduce development time and costs through reliance on ground-based testing. In the present effort, the authors have studied the effect of evaporator orientation on flow boiling performance of HFE7100 in a 218 m tall by 13.0 mm wide microgap cooler. Similar heat transfer coefficients and critical heat flux were achieved across five evaporator orientations, indicating that the effect of gravity was negligible.

A Ghost Fluid/Level Set Method for boiling flows and liquid evaporation: Application to the Leidenfrost effect

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rueda Villegas, Lucia; Alis, Romain; Lepilliez, Mathieu

2016-07-01

The development of numerical methods for the direct numerical simulation of two-phase flows with phase change, in the framework of interface capturing or interface tracking methods, is the main topic of this study. We propose a novel numerical method, which allows dealing with both evaporation and boiling at the interface between a liquid and a gas. Indeed, in some specific situations involving very heterogeneous thermodynamic conditions at the interface, the distinction between boiling and evaporation is not always possible. For instance, it can occur for a Leidenfrost droplet; a water drop levitating above a hot plate whose temperature is muchmore » higher than the boiling temperature. In this case, boiling occurs in the film of saturated vapor which is entrapped between the bottom of the drop and the plate, whereas the top of the water droplet evaporates in contact of ambient air. The situation can also be ambiguous for a superheated droplet or at the contact line between a liquid and a hot wall whose temperature is higher than the saturation temperature of the liquid. In these situations, the interface temperature can locally reach the saturation temperature (boiling point), for instance near a contact line, and be cooler in other places. Thus, boiling and evaporation can occur simultaneously on different regions of the same liquid interface or occur successively at different times of the history of an evaporating droplet. Standard numerical methods are not able to perform computations in these transient regimes, therefore, we propose in this paper a novel numerical method to achieve this challenging task. Finally, we present several accuracy validations against theoretical solutions and experimental results to strengthen the relevance of this new method.« less

Boiling of multicomponent working fluids used in refrigeration and cryogenic systems

NASA Astrophysics Data System (ADS)

Mogorychny, V. I.; Dolzhikov, A. S.

2017-11-01

Working fluids based on mixtures are widely used in cryogenic and refrigeration engineering. One of the main elements of low-temperature units is a recuperative heat exchanger where the return flow cools the direct (cold regeneration is carrying out) resulting in continuous boiling and condensation of the multicomponent working fluid in the channels. The temperature difference between the inlet and outlet of the heat exchanger can be more than 100K, which leads to a strong change in thermophysical properties along its length. In addition, the fraction of the liquid and vapor phases in the flow varies very much, which affects the observed flow regimes in the heat exchanger channels. At the moment there are not so many experimental data and analytical correlations that would allow to estimate the heat transfer coefficient during the flow of a two-phase mixture flow at low temperatures. The work is devoted to the study of the boiling process of multicomponent working fluids used in refrigeration and cryogenic engineering. The description of the method of determination of heat transfer coefficient during boiling of mixtures in horizontal heated channel is given as well as the design of the experimental stand allowing to make such measurements. This stand is designed on the basis of a refrigeration unit operating on the Joule-Thomson throttle cycle and makes it possible to measure the heat transfer coefficient with a good accuracy. Also, the calculated values of the heat transfer coefficient, obtained with the use of various correlations, are compared with the existing experimental data. Knowing of the heat transfer coefficient will be very useful in the design of heat exchangers for low-temperature units operating on a mixture refrigerant.

Flow-mediated changes in pulse wave velocity: a new clinical measure of endothelial function.

PubMed

Naka, Katerina K; Tweddel, Ann C; Doshi, Sagar N; Goodfellow, Jonathan; Henderson, Andrew H

2006-02-01

To test whether measuring hyperaemic changes in pulse wave velocity (PWV) could be used as a new method of assessing endothelial function for use in clinical practice. Flow-mediated changes in vascular tone may be used to assess endothelial function and may be induced by distal hyperaemia, while endothelium-mediated changes in vascular tone can influence PWV. These three known principles were combined to provide and test a novel method of measuring endothelial function by the acute effects of distal hyperaemia on upper and lower limb PWV (measured by a recently developed method). Flow-mediated changes in upper and lower limb PWV were compared in 17 healthy subjects and seven patients with stable chronic heart failure (CHF), as a condition where endothelial function is impaired but endothelium-independent dilator responses are retained. Corroborative measurements of PWV and brachial artery diameter responses to endothelium-dependent and -independent pharmacological stimuli were performed in a further eight healthy subjects. Flow-mediated reduction of PWV (by 14% with no change in blood pressure) was found in normal subjects but was almost abolished in patients with CHF. PWV responses appear to be inversely related to and relatively greater than brachial artery diameter responses. The method may offer potential advantages of practical use and sensitivity over conduit artery diameter responses to measure endothelial dysfunction.

Effects of moderate heart failure and functional overload on rat plantaris muscle

NASA Technical Reports Server (NTRS)

Spangenburg, Espen E.; Lees, Simon J.; Otis, Jeff S.; Musch, Timothy I.; Talmadge, Robert J.; Williams, Jay H.

2002-01-01

It is thought that changes in sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA) of skeletal muscle contribute to alterations in skeletal muscle function during congestive heart failure (CHF). It is well established that exercise training can improve muscle function. However, it is unclear whether similar adaptations will result from exercise training in a CHF patient. Therefore, the purpose of this study was to determine whether skeletal muscle during moderate CHF adapts to increased activity, utilizing the functional overload (FO) model. Significant increases in plantaris mass of the CHF-FO and sham-FO groups compared with the CHF and control (sham) groups were observed. Ca(2+) uptake rates were significantly elevated in the CHF group compared with all other groups. No differences were detected in Ca(2+) uptake rates between the CHF-FO, sham, and sham-FO groups. Increases in Ca(2+) uptake rates in moderate-CHF rats were not due to changes in SERCA isoform proportions; however, FO may have attenuated the CHF-induced increases through alterations in SERCA isoform expression. Therefore, changes in skeletal muscle Ca(2+) handling during moderate CHF may be due to alterations in regulatory mechanisms, which exercise may override, by possibly altering SERCA isoform expression.

Experimental Study of the Relation Between Heat Transfer and Flow Behavior in a Single Microtube

NASA Astrophysics Data System (ADS)

Huang, Shih-Che; Kawanami, Osamu; Kawakami, Kazunari; Honda, Itsuro; Kawashima, Yousuke; Ohta, Haruhiko

2008-09-01

The flow boiling heat transfer in microchannels have become important issue because it is extremely high-performance heat exchanger for electronic devices. For a detailed study on flow boiling heat transfer in a microtube, we have used a transparent heated microtube, which is coated with a thin gold film on its inner wall. The gold film is used as a resistance thermometer to directly evaluate the inner wall temperature averaged over the entire temperature measurement length. At the same time, the transparency of the film enables the observation of fluid behavior. Flow boiling experiments have been carried out using the microtube under the following conditions; mass velocity of 105 kg/m2 s, tube diameter of 1 mm, heat flux in the range of 10 380 kW/m2 s, and the test fluid used is ionized water. Under low heat flux conditions, the fluctuations in the inner wall temperature and mass velocity are closely related; the frequency of these fluctuations is the same. However, the fluctuations in the inner wall temperature and heat transfer coefficient are found to be independent of the fluctuation in the mass velocity under high heat flux conditions.

Forced Convection Heat Transfer of Subcooled Liquid Nitrogen in Horizontal Tube

NASA Astrophysics Data System (ADS)

Tatsumoto, H.; Shirai, Y.; Hata, K.; Kato, T.; Shiotsu, M.

2008-03-01

The knowledge of forced convection heat transfer of liquid hydrogen is important for the cooling design of a HTS superconducting magnet and a cold neutron moderator material. An experimental apparatus that could obtain forced flow without a pump was developed. As a first step of the study, the forced flow heat transfer of subcooled liquid nitrogen in a horizontal tube, instead of liquid hydrogen, was measured for the pressures ranging from 0.3 to 2.5 MPa. The inlet temperature was varied from 78 K to around its saturation temperature. The flow velocities were varied from 0.1 to 7 m/s. The heat transfer coefficients in the non-boiling region and the departure from nucleate boiling (DNB) heat fluxes were higher for higher flow velocity and higher subcooling. The measured values of Nu/Pr0.4 in the non-boiling region were proportional to Reynolds number (Re) to the power of 0.8. With a decrease in Re, Nu/Pr0.4 approached a constant value corresponding to that in a pool of liquid nitrogen. The correlation of DNB heat flux was derived that can describe the experimental data within ±15% difference.

The sudden coalescene model of the boiling crisis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carrica, P.M.; Clausse, A.

1995-09-01

A local two-phase flow integral model of nucleate boiling and crisis is presented. The model is based on average balances on a control volume, yielding to a set of three nonlinear differential equations for the local void fraction, bubble number density and velocity. Boiling crisis as critical heat flux is interpreted as a dynamic transition caused by the coalescence of bubbles near the heater. The theoretical dynamic model is compared with experimental results obtained for linear power ramps in a horizontal plate heater in R-113, showing an excellent qualitative agreement.

Effects of exercise training on circulating and skeletal muscle renin-angiotensin system in chronic heart failure rats.

PubMed

Gomes-Santos, Igor Lucas; Fernandes, Tiago; Couto, Gisele Kruger; Ferreira-Filho, Julio César Ayres; Salemi, Vera Maria Cury; Fernandes, Fernanda Barrinha; Casarini, Dulce Elena; Brum, Patricia Chakur; Rossoni, Luciana Venturini; de Oliveira, Edilamar Menezes; Negrao, Carlos Eduardo

2014-01-01

Accumulated evidence shows that the ACE-AngII-AT1 axis of the renin-angiotensin system (RAS) is markedly activated in chronic heart failure (CHF). Recent studies provide information that Angiotensin (Ang)-(1-7), a metabolite of AngII, counteracts the effects of AngII. However, this balance between AngII and Ang-(1-7) is still little understood in CHF. We investigated the effects of exercise training on circulating and skeletal muscle RAS in the ischemic model of CHF. Male Wistar rats underwent left coronary artery ligation or a Sham operation. They were divided into four groups: 1) Sedentary Sham (Sham-S), 2) exercise-trained Sham (Sham-Ex), sedentary CHF (CHF-S), and exercise-trained CHF (CHF-Ex). Angiotensin concentrations and ACE and ACE2 activity in the circulation and skeletal muscle (soleus and plantaris) were quantified. Skeletal muscle ACE and ACE2 protein expression, and AT1, AT2, and Mas receptor gene expression were also evaluated. CHF reduced ACE2 serum activity. Exercise training restored ACE2 and reduced ACE activity in CHF. Exercise training reduced plasma AngII concentration in both Sham and CHF rats and increased the Ang-(1-7)/AngII ratio in CHF rats. CHF and exercise training did not change skeletal muscle ACE and ACE2 activity and protein expression. CHF increased AngII levels in both soleus and plantaris muscle, and exercise training normalized them. Exercise training increased Ang-(1-7) in the plantaris muscle of CHF rats. The AT1 receptor was only increased in the soleus muscle of CHF rats, and exercise training normalized it. Exercise training increased the expression of the Mas receptor in the soleus muscle of both exercise-trained groups, and normalized it in plantaris muscle. Exercise training causes a shift in RAS towards the Ang-(1-7)-Mas axis in skeletal muscle, which can be influenced by skeletal muscle metabolic characteristics. The changes in RAS circulation do not necessarily reflect the changes occurring in the RAS of skeletal muscle.

Thermal-hydraulic simulation of natural convection decay heat removal in the High Flux Isotope Reactor (HFIR) using RELAP5 and TEMPEST: Part 2, Interpretation and validation of results

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ruggles, A.E.; Morris, D.G.

The RELAP5/MOD2 code was used to predict the thermal-hydraulic behavior of the HFIR core during decay heat removal through boiling natural circulation. The low system pressure and low mass flux values associated with boiling natural circulation are far from conditions for which RELAP5 is well exercised. Therefore, some simple hand calculations are used herein to establish the physics of the results. The interpretation and validation effort is divided between the time average flow conditions and the time varying flow conditions. The time average flow conditions are evaluated using a lumped parameter model and heat balance. The Martinelli-Nelson correlations are usedmore » to model the two-phase pressure drop and void fraction vs flow quality relationship within the core region. Systems of parallel channels are susceptible to both density wave oscillations and pressure drop oscillations. Periodic variations in the mass flux and exit flow quality of individual core channels are predicted by RELAP5. These oscillations are consistent with those observed experimentally and are of the density wave type. The impact of the time varying flow properties on local wall superheat is bounded herein. The conditions necessary for Ledinegg flow excursions are identified. These conditions do not fall within the envelope of decay heat levels relevant to HFIR in boiling natural circulation. 14 refs., 5 figs., 1 tab.« less

Physics of microstructures enhancement of thin film evaporation heat transfer in microchannels flow boiling

PubMed Central

Bigham, Sajjad; Fazeli, Abdolreza; Moghaddam, Saeed

2017-01-01

Performance enhancement of the two-phase flow boiling heat transfer process in microchannels through implementation of surface micro- and nanostructures has gained substantial interest in recent years. However, the reported results range widely from a decline to improvements in performance depending on the test conditions and fluid properties, without a consensus on the physical mechanisms responsible for the observed behavior. This gap in knowledge stems from a lack of understanding of the physics of surface structures interactions with microscale heat and mass transfer events involved in the microchannel flow boiling process. Here, using a novel measurement technique, the heat and mass transfer process is analyzed within surface structures with unprecedented detail. The local heat flux and dryout time scale are measured as the liquid wicks through surface structures and evaporates. The physics governing heat transfer enhancement on textured surfaces is explained by a deterministic model that involves three key parameters: the drying time scale of the liquid film wicking into the surface structures (τd), the heating length scale of the liquid film (δH) and the area fraction of the evaporating liquid film (Ar). It is shown that the model accurately predicts the optimum spacing between surface structures (i.e. pillars fabricated on the microchannel wall) in boiling of two fluids FC-72 and water with fundamentally different wicking characteristics. PMID:28303952

Chronic heart failure and aging - effects of exercise training on endothelial function and mechanisms of endothelial regeneration: Results from the Leipzig Exercise Intervention in Chronic heart failure and Aging (LEICA) study.

PubMed

Sandri, Marcus; Viehmann, Manuel; Adams, Volker; Rabald, Kristin; Mangner, Norman; Höllriegel, Robert; Lurz, Philipp; Erbs, Sandra; Linke, Axel; Kirsch, Katharina; Möbius-Winkler, Sven; Thiery, Joachim; Teupser, Daniel; Hambrecht, Rainer; Schuler, Gerhard; Gielen, Stephan

2016-03-01

A reduction in number and function of endothelial progenitor cells (EPCs) occurs in both physiologic aging and chronic heart failure (CHF). We assessed whether disease and aging have additive effects on EPCs or whether beneficial effects of exercise training are diminished in old age. We randomized 60 patients with stable CHF and 60 referent controls to a training or a control group. To detect possible aging effects we included subjects below 55 (young) and above 65 years (older). Subjects in the training group exercised four times daily at 60% to 70% of VO2max for four weeks under supervision. At baseline and after the intervention the number and function of EPCs were assessed. As compared with young referent controls, older referent controls showed at baseline a reduced EPC number (young: 190 ± 37 CD34/KDR positive cells/ml blood; older: 131 ± 26 CD34/KDR positive cells/ml blood; p < 0.05) and function (young: 230 ± 41 migrated cells/1000 plated cells; older: 185 ± 28 cells/1000 plated cells; p < 0.05). In young and older CHF patients EPC-number (young: 85 ± 21 CD34/KDR positive cells/ml blood; older: 78 ± 20 CD34/KDR positive cells/ml blood) and EPC-function (young: 113 ± 26 cells/1000 plated cells; older: 120 ± 27 cells/1000 plated cells) were impaired. As a result of exercise training, EPC function improved by 24% in older referent controls (p < 0.05), while it remained unchanged in young training referent controls and controls respectively. In young and older patients with CHF four weeks of exercise training resulted in a significant improvement in EPC numbers and EPC function (young: number +66% function +43%; p < 0.05; older: number +69% function +36%; p < 0.05). These results were accompanied by a significant increase in flow mediated dilatation in the training groups of young/older CHF patients and in older referent controls. Four weeks of exercise training are effective in improving EPC number and EPC function in CHF patients. These training effects were not impaired among older patients, emphasizing the potentials of rehabilitation interventions in a patient group where CHF has a high prevalence. © The European Society of Cardiology 2015.

Carbon-based nanostructured surfaces for enhanced phase-change cooling

NASA Astrophysics Data System (ADS)

Selvaraj Kousalya, Arun

To maintain acceptable device temperatures in the new generation of electronic devices under development for high-power applications, conventional liquid cooling schemes will likely be superseded by multi-phase cooling solutions to provide substantial enhancement to the cooling capability. The central theme of the current work is to investigate the two-phase thermal performance of carbon-based nanostructured coatings in passive and pumped liquid-vapor phase-change cooling schemes. Quantification of the critical parameters that influence thermal performance of the carbon nanostructured boiling surfaces presented herein will lead to improved understanding of the underlying evaporative and boiling mechanisms in such surfaces. A flow boiling experimental facility is developed to generate consistent and accurate heat transfer performance curves with degassed and deionized water as the working fluid. New means of boiling heat transfer enhancement by altering surface characteristics such as surface energy and wettability through light-surface interactions is explored in this work. In this regard, carbon nanotube (CNT) coatings are exposed to low-intensity irradiation emitted from a light emitting diode and the subcooled flow boiling performance is compared against a non-irradiated CNT-coated copper surface. A considerable reduction in surface superheat and enhancement in average heat transfer coefficient is observed. In another work involving CNTs, the thermal performance of CNT-integrated sintered wick structures is evaluated in a passively cooled vapor chamber. A physical vapor deposition process is used to coat the CNTs with varying thicknesses of copper to promote surface wetting with the working fluid, water. Thermal performance of the bare sintered copper powder sample and the copper-functionalized CNT-coated sintered copper powder wick samples is compared using an experimental facility that simulates the capillary fluid feeding conditions of a vapor chamber. Nanostructured samples having a thicker copper coating provided a considerable increase in dryout heat flux while maintaining lower surface superheat temperatures compared to a bare sintered powder sample; this enhancement is attributed primarily to the improved surface wettability. Dynamic contact angle measurements are conducted to quantitatively compare the surface wetting trends for varying copper coating thicknesses and confirm the increase in hydrophilicity with increasing coating thickness. The second and relatively new carbon nanostructured coating, carbon nanotubes decorated with graphitic nanopetals, are used as a template to manufacture boiling surfaces with heterogeneous wettability. Heat transfer surfaces with parallel alternating superhydrophobic and superhydrophilic stripes are fabricated by a combination of oxygen plasma treatment, Teflon coating and shadow masking. Such composite wetting surfaces exhibit enhanced flow-boiling performance compared to homogeneous wetting surfaces. Flow visualization studies elucidate the physical differences in nucleate boiling mechanisms between the different heterogeneous wetting surfaces. The third and the final carbon nanomaterial, graphene, is examined as an oxidation barrier coating for liquid and liquid-vapor phase-change cooling systems. Forced convection heat transfer experiments on bare and graphene-coated copper surfaces reveal nearly identical liquid-phase and two-phase thermal performance for the two surfaces. Surface analysis after thermal testing indicates significant oxide formation on the entire surface of the bare copper substrate; however, oxidation is observed only along the grain boundaries of the graphene-coated substrate. Results suggest that few-layer graphene can act as a protective layer even under vigorous flow boiling conditions, indicating a broad application space of few-layer graphene as an ultra-thin oxidation barrier coating.

Heat Transfer in Boiling Dilute Emulsion with Strong Buoyancy

NASA Astrophysics Data System (ADS)

Freeburg, Eric Thomas

Little attention has been given to the boiling of emulsions compared to that of boiling in pure liquids. The advantages of using emulsions as a heat transfer agent were first discovered in the 1970s and several interesting features have since been studied by few researchers. Early research focuses primarily on pool and flow boiling and looks to determine a mechanism by which the boiling process occurs. This thesis looks at the boiling of dilute emulsions in fluids with strong buoyant forces. The boiling of dilute emulsions presents many favorable characteristics that make it an ideal agent for heat transfer. High heat flux electronics, such as those seen in avionics equipment, produce high heat fluxes of 100 W/cm2 or more, but must be maintained at low temperatures. So far, research on single phase convection and flow boiling in small diameter channels have yet to provide an adequate solution. Emulsions allow the engineer to tailor the solution to the specific problem. The fluid can be customized to retain the high thermal conductivity and specific heat capacity of the continuous phase while enhancing the heat transfer coefficient through boiling of the dispersed phase component. Heat transfer experiments were carried out with FC-72 in water emulsions. FC-72 has a saturation temperature of 56 °C, far below that of water. The parameters were varied as follows: 0% ≤ epsilon ≤ 1% and 1.82 x 1012 ≤ RaH ≤ 4.42 x 1012. Surface temperatures along the heated surface reached temperature that were 20 °C in excess of the dispersed phase saturation temperature. An increase of ˜20% was seen in the average Nusselt numbers at the highest Rayleigh numbers. Holography was used to obtain images of individual and multiple FC-72 droplets in the boundary layer next to the heated surface. The droplet diameters ranged from 0.5 mm to 1.3 mm. The Magnus effect was observed when larger individual droplets were injected into the boundary layer, causing the droplets to be pushed outside the boundary layer. Vaporization of FC-72 droplets in the boundary layer next to the heated surface was not observed.

Conceptual design for spacelab pool boiling experiment

NASA Technical Reports Server (NTRS)

Lienhard, J. H.; Peck, R. E.

1978-01-01

A pool boiling heat transfer experiment to be incorporated with a larger two-phase flow experiment on Spacelab was designed to confirm (or alter) the results of earth-normal gravity experiments which indicate that the hydrodynamic peak and minimum pool boiling heat fluxes vanish at very low gravity. Twelve small sealed test cells containing water, methanol or Freon 113 and cylindrical heaters of various sizes are to be built. Each cell will be subjected to one or more 45 sec tests in which the surface heat flux on the heaters is increased linearly until the surface temperature reaches a limiting value of 500 C. The entire boiling process will be photographed in slow-motion. Boiling curves will be constructed from thermocouple and electric input data, for comparison with the motion picture records. The conduct of the experiment will require no more than a few hours of operator time.

Effect of metoprolol administration on renal sodium handling in experimental congestive heart failure.

PubMed

DiBona, G F; Sawin, L L

1999-07-06

Long-term metoprolol therapy improves cardiac performance and decreases mortality in patients with chronic congestive heart failure (CHF). This study examined the effect of long-term metoprolol therapy on renal sodium handling in an experimental rat model of CHF. Rats with left coronary ligation and myocardial infarction-induced CHF were treated with metoprolol (1.5 mg. kg-1. h-1) or vehicle for 3 weeks by osmotic minipump. They were then evaluated for their ability to excrete a short-term sodium load (5% body weight isotonic saline infusion over 30 minutes) and a long-term sodium load (change from low- to high-sodium diet over 8 days). All CHF rats had left ventricular end-diastolic pressure >10 mm Hg, and heart weight/body weight ratios averaged 0.68+/-0.02% (versus control of approximately 0.40%). Compared with vehicle CHF rats (n=19), metoprolol CHF rats (n=18) had lower basal values of mean arterial pressure (122+/-3 versus 112+/-3 mm Hg) and heart rate (373+/-14 versus 315+/-9 bpm) and decreased heart rate responses to intravenous doses of isoproterenol. During short-term isotonic saline volume loading, metoprolol CHF rats excreted 54+/-4% more of the sodium load than vehicle CHF rats. During long-term dietary sodium loading, metoprolol CHF rats retained 28+/-3% less sodium than vehicle CHF rats. Metoprolol treatment of rats with CHF results in an improved ability to excrete both short- and long-term sodium loads.

Visual analysis of flow boiling at different gravity levels in 4.0 mm tube

NASA Astrophysics Data System (ADS)

Valencia-Castillo, C. M.; Celata, G. P.; Saraceno, L.; Zummo, G.

2014-11-01

The aim of the present paper is to describe the results of flow boiling heat transfer at low gravity and compare them with those obtained at earth gravity, evaluating possible differences. The experimental campaigns at low gravity have been performed during the parabolic flight campaign of October-November 2013. The paper will show the analysis of differences between the heat transfer coefficients and vapour bubble parameters at normal and at zero gravity. The results of 4.0 mm tube are presented and discussed. With respect to terrestrial gravity, heat transfer is systematically lower at microgravity in the range of the experimental conditions. Heat transfer differences for the two gravity conditions are related to the different bubble size in each of them. The size of a bubble in flow boiling is affected by the gravity level, being larger at low gravity, unless inertial forces are largely predominant over buoyancy and other forces acting on the bubble itself when detaching from a heated wall. Vapour bubble parameters (bubble diameter, bubble length, width, and nose velocity) have been measured.

Boiling water neutronic reactor incorporating a process inherent safety design

DOEpatents

Forsberg, C.W.

1985-02-19

A boiling-water reactor core is positioned within a prestressed concrete reactor vessel of a size which will hold a supply of coolant water sufficient to submerge and cool the reactor core by boiling for a period of at least one week after shutdown. Separate volumes of hot, clean (nonborated) water for cooling during normal operation and cool highly borated water for emergency cooling and reactor shutdown are separated by an insulated wall during normal reactor operation with contact between the two water volumes being maintained at interfaces near the top and bottom ends of the reactor vessel. Means are provided for balancing the pressure of the two water volumes at the lower interface zone during normal operation to prevent entry of the cool borated water into the reactor core region, for detecting the onset of excessive power to coolant flow conditions in the reactor core and for detecting low water levels of reactor coolant. Cool borated water is permitted to flow into the reactor core when low reactor coolant levels or excessive power to coolant flow conditions are encountered.

Boiling water neutronic reactor incorporating a process inherent safety design

DOEpatents

Forsberg, Charles W.

1987-01-01

A boiling-water reactor core is positioned within a prestressed concrete reactor vessel of a size which will hold a supply of coolant water sufficient to submerge and cool the reactor core by boiling for a period of at least one week after shutdown. Separate volumes of hot, clean (non-borated) water for cooling during normal operation and cool highly borated water for emergency cooling and reactor shutdown are separated by an insulated wall during normal reactor operation with contact between the two water volumes being maintained at interfaces near the top and bottom ends of the reactor vessel. Means are provided for balancing the pressure of the two volumes at the lower interface zone during normal operation to prevent entry of the cool borated water into the reactor core region, for detecting the onset of excessive power to coolant flow conditions in the reactor core and for detecting low water levels of reactor coolant. Cool borated water is permitted to flow into the reactor core when low reactor coolant levels or excessive power to coolant flow conditions are encountered.

Numerical and experimental study of the dynamics of a superheated jet

NASA Astrophysics Data System (ADS)

Sinha, Avick; Gopalakrishnan, Shivasubramanian; Balasubramanian, Sridhar

2015-11-01

Flash-boiling is a phenomenon where a liquid experiences low pressures in a system resulting in it getting superheated. The sudden drop in pressures results in accelerated expansion and violent vapour formation. Understanding the physics behind the jet disintegration and flash-boiling phenomenon is still an open problem, with applications in automotive and aerospace combustors. The behaviour of a flash-boiling jet is highly dependent on the input parameters, inlet temperature and pressure. In the present study, the external (outside nozzle) and the internal (inside nozzle) flow characteristics of the two-phase flow has been studied numerically and experimentally. The phase change from liquid to vapour takes place over a finite period of time, modeled sing Homogeneous Relaxation Model (HRM). In order to validate the numerical results, controlled experiments were performed. Optical diagnostic techniques such as Particle Image Velocimetry (PIV) and Shadowgraphy were used to study the flow characteristics. Spray angle, penetration depth, droplet spectra were obtained which provides a better understanding of the break-up mechanism. Linear stability analysis is performed to study the stability characteristics of the jet.

The effect of congestive heart failure on sensor accuracy among hospitalized patients with type 2 diabetes.

PubMed

Dungan, Kathleen; Graessle, Kari; Sagrilla, Colleen

2013-10-01

Congestive heart failure (CHF) features disturbances in the interstitial environment that may affect the accuracy of subcutaneous continuous glucose monitoring (CGM). A pooled analysis of two studies of hospitalized patients with type 2 diabetes randomized to intravenous or subcutaneous insulin was conducted. One study enrolled patients with CHF exacerbation, whereas history of CHF was an exclusion criterion in the other. All patients wore a professional CGM device for at least 24 h. Intravenous insulin was administered according to the institution's nursing-run protocol (duration of 12 and 48 h in non-CHF and CHF protocols, respectively). Subcutaneous insulin was delivered similarly in both groups. Subjects with CHF (n=43) had higher admission glucose and hemoglobin A1c compared with non-CHF subjects (n=32), but the sensor glucose values were similar. Overall mean absolute relative difference (MARD) was similar between CHF and non-CHF subjects (0.11 vs. 0.08, respectively; P=0.12). MARD was higher in the 100-149 mg/dL (P=0.003) and >199 mg/dL (P = 0.02) strata among CHF subjects. Static glucose and continuous glucose error grid analyses favored the non-CHF group. In multivariable analyses, only glucose coefficient of variation and log sensor time were independent predictors of elevated overall MARD >0.10. After adjustment for other factors, only increasing log sensor time was a significant predictor of elevated MARD in the 100-149 mg/dL strata. Among hospitalized subjects with type 2 diabetes, CHF exacerbation is not associated with lower sensor accuracy after adjustment for other factors, but this requires confirmation over a wider glucose range.

The evaluation of β-adrenoceptor blocking agents in patients with COPD and congestive heart failure: a nationwide study

PubMed Central

Lin, Tien-Yu; Huang, Yaw-Bin; Chen, Chung-Yu

2017-01-01

Objective β-Blockers are safe and improve survival in patients with both congestive heart failure (CHF) and COPD. However, the superiority of different types of β-blockers is still unclear among patients with CHF and COPD. The association between β-blockers and CHF exacerbation as well as COPD exacerbation remains unclear. The objective of this study was to compare the outcome of different β-blockers in patients with concurrent CHF and COPD. Patients and methods We used the National Health Insurance Research Database in Taiwan to conduct a retrospective cohort study. The inclusion criteria for CHF were patients who were >20 years old and were diagnosed with CHF between January 1, 2005 and December 31, 2012. COPD patients included those who had outpatient visit claims ≥2 times within 365 days or 1 claim for hospitalization with a COPD diagnosis. A time-dependent Cox proportional hazards regression model was applied to evaluate the effectiveness of β-blockers in the study population. Results We identified 1,872 patients with concurrent CHF and COPD. Only high-dose bisoprolol significantly reduced the risk of death and slightly decreased the hospitalization rate due to CHF exacerbation (death: adjusted hazard ratio [aHR] =0.51, 95% confidence interval [CI] =0.29–0.89; hospitalization rate due to CHF exacerbation: aHR =0.48, 95% CI =0.23–1.00). No association was observed between β-blocker use and COPD exacerbation. Conclusion In patients with concurrent CHF and COPD, β-blockers reduced mortality, CHF exacerbation, and the need for hospitalization. Bisoprolol was found to reduce mortality and CHF exacerbation compared to carvedilol and metoprolol. PMID:28894360

GRACE score predicts heart failure admission following acute coronary syndrome.

PubMed

McAllister, David A; Halbesma, Nynke; Carruthers, Kathryn; Denvir, Martin; Fox, Keith A

2015-04-01

Congestive heart failure (CHF) is a common and preventable complication of acute coronary syndrome (ACS). Nevertheless, ACS risk scores have not been shown to predict CHF risk. We investigated whether the at-discharge Global Registry of Acute Coronary Events (GRACE) score predicts heart failure admission following ACS. Five-year mortality and hospitalization data were obtained for patients admitted with ACS from June 1999 to September 2009 to a single centre of the GRACE registry. CHF was defined as any admission assigned WHO International Classification of Diseases 10 diagnostic code I50. The hazard ratio (HR) for CHF according to GRACE score was estimated in Cox models adjusting for age, gender and the presence of CHF on index admission. Among 1,956 patients, CHF was recorded on index admission in 141 patients (7%), and 243 (12%) were admitted with CHF over 3.8 median years of follow-up. Compared to the lowest quintile, patients in the highest GRACE score quintile had more CHF admissions (116 vs 17) and a shorter time to first admission (1.2 vs 2.0 years, HR 9.87, 95% CI 5.93-16.43). Per standard deviation increment in GRACE score, the instantaneous risk was more than two-fold higher (HR 2.28; 95% CI 2.02-2.57), including after adjustment for CHF on index admission, age and gender (HR 2.49; 95% CI 2.06-3.02). The C-statistic for CHF admission at 1-year was 0.74 (95% CI 0.70-0.79). The GRACE score predicts CHF admission, and may therefore be used to target ACS patients at high risk of CHF with clinical monitoring and therapies. © The European Society of Cardiology 2014.

The Effect of Congestive Heart Failure on Sensor Accuracy Among Hospitalized Patients with Type 2 Diabetes

PubMed Central

Graessle, Kari; Sagrilla, Colleen

2013-01-01

Abstract Background Congestive heart failure (CHF) features disturbances in the interstitial environment that may affect the accuracy of subcutaneous continuous glucose monitoring (CGM). Subjects and Methods A pooled analysis of two studies of hospitalized patients with type 2 diabetes randomized to intravenous or subcutaneous insulin was conducted. One study enrolled patients with CHF exacerbation, whereas history of CHF was an exclusion criterion in the other. All patients wore a professional CGM device for at least 24 h. Intravenous insulin was administered according to the institution's nursing-run protocol (duration of 12 and 48 h in non-CHF and CHF protocols, respectively). Subcutaneous insulin was delivered similarly in both groups. Results Subjects with CHF (n=43) had higher admission glucose and hemoglobin A1c compared with non-CHF subjects (n=32), but the sensor glucose values were similar. Overall mean absolute relative difference (MARD) was similar between CHF and non-CHF subjects (0.11 vs. 0.08, respectively; P=0.12). MARD was higher in the 100–149 mg/dL (P=0.003) and >199 mg/dL (P=0.02) strata among CHF subjects. Static glucose and continuous glucose error grid analyses favored the non-CHF group. In multivariable analyses, only glucose coefficient of variation and log sensor time were independent predictors of elevated overall MARD >0.10. After adjustment for other factors, only increasing log sensor time was a significant predictor of elevated MARD in the 100–149 mg/dL strata. Conclusions Among hospitalized subjects with type 2 diabetes, CHF exacerbation is not associated with lower sensor accuracy after adjustment for other factors, but this requires confirmation over a wider glucose range. PMID:24050738

Endothelial dysfunction in patients with chronic heart failure is independently associated with increased incidence of hospitalization, cardiac transplantation, or death.

PubMed

Fischer, D; Rossa, S; Landmesser, U; Spiekermann, S; Engberding, N; Hornig, B; Drexler, H

2005-01-01

Endothelial dysfunction of coronary and peripheral arteries has been demonstrated in patients with chronic heart failure (CHF) and appears to be associated with functional implications. However, it is unknown whether endothelial dysfunction in CHF is independently associated with impaired outcome or progression of the disease. We assessed the follow-up of 67 consecutive patients with CHF [New York Heart Association (NYHA) functional class II-III] in which flow-dependent, endothelium-mediated vasodilation (FDD) of the radial artery was assessed by high resolution ultrasound. The primary endpoint was defined by cardiac death, hospitalization due to worsening of heart failure (NYHA class IV, pulmonary oedema), or heart transplantation. Cox regression analysis was used to determine whether FDD was associated with these heart failure-related events. During a median follow-up of 45.7 months 24 patients had an event: 18 patients were hospitalized due to worsening of heart failure or heart transplantation, six patients died for cardiac reasons. Cox regression analysis demonstrated that FDD (P<0.01), diabetes mellitus (P<0.01), and ejection fraction (P<0.01) were independent predictive factors for the occurrence of the primary endpoint. The Kaplan-Meier survival curve revealed a significantly better clinical outcome in patients with FDD above the median (6.2%) compared with those with FDD below the median (P<0.013). These observations suggest that endothelium-mediated vasodilation represents an independent predictor of cardiac death and hospitalization in patients with CHF, consistent with the notion that endothelium-derived nitric oxide may play a protective role in heart failure.

Chronic heart failure management in Australia -- time for general practice centred models of care?

PubMed

Scott, Ian; Jackson, Claire

2013-05-01

Chronic heart failure (CHF) is an increasingly prevalent problem within ageing populations and accounts for thousands of hospitalisations and deaths annually in Australia. Disease management programs for CHF (CHF-DMPs) aim to optimise care, with the predominant model being cardiologist led, hospital based multidisciplinary clinics with cardiac nurse outreach. However, findings from contemporary observational studies and clinical trials raise uncertainty around the effectiveness and sustainability of traditional CHF-DMPs in real-world clinical practice. To suggest an alternative model of care that involves general practitioners with a special interest in CHF liaising with, and being up-skilled by, specialists within community based, multidisciplinary general practice settings. Preliminary data from trials evaluating primary care based CHF-DMPs are encouraging, and further studies are underway comparing this model of care with traditional hospital based, specialist led CHF-DMPs. Results of studies of similar primary care models targeting diabetes and other chronic diseases suggest potential for its application to CHF.

Superconducting magnet cooling system

DOEpatents

Vander Arend, Peter C.; Fowler, William B.

1977-01-01

A device is provided for cooling a conductor to the superconducting state. The conductor is positioned within an inner conduit through which is flowing a supercooled liquid coolant in physical contact with the conductor. The inner conduit is positioned within an outer conduit so that an annular open space is formed therebetween. Through the annular space is flowing coolant in the boiling liquid state. Heat generated by the conductor is transferred by convection within the supercooled liquid coolant to the inner wall of the inner conduit and then is removed by the boiling liquid coolant, making the heat removal from the conductor relatively independent of conductor length.

Experimental heart failure causes depression-like behavior together with differential regulation of inflammatory and structural genes in the brain.

PubMed

Frey, Anna; Popp, Sandy; Post, Antonia; Langer, Simon; Lehmann, Marc; Hofmann, Ulrich; Sirén, Anna-Leena; Hommers, Leif; Schmitt, Angelika; Strekalova, Tatyana; Ertl, Georg; Lesch, Klaus-Peter; Frantz, Stefan

2014-01-01

Depression and anxiety are common and independent outcome predictors in patients with chronic heart failure (CHF). However, it is unclear whether CHF causes depression. Thus, we investigated whether mice develop anxiety- and depression-like behavior after induction of ischemic CHF by myocardial infarction (MI). In order to assess depression-like behavior, anhedonia was investigated by repeatedly testing sucrose preference for 8 weeks after coronary artery ligation or sham operation. Mice with large MI and increased left ventricular dimensions on echocardiography (termed CHF mice) showed reduced preference for sucrose, indicating depression-like behavior. 6 weeks after MI, mice were tested for exploratory activity, anxiety-like behavior and cognitive function using the elevated plus maze (EPM), light-dark box (LDB), open field (OF), and object recognition (OR) tests. In the EPM and OF, CHF mice exhibited diminished exploratory behavior and motivation despite similar movement capability. In the OR, CHF mice had reduced preference for novelty and impaired short-term memory. On histology, CHF mice had unaltered overall cerebral morphology. However, analysis of gene expression by RNA-sequencing in prefrontal cortical, hippocampal, and left ventricular tissue revealed changes in genes related to inflammation and cofactors of neuronal signal transduction in CHF mice, with Nr4a1 being dysregulated both in prefrontal cortex and myocardium after MI. After induction of ischemic CHF, mice exhibited anhedonic behavior, decreased exploratory activity and interest in novelty, and cognitive impairment. Thus, ischemic CHF leads to distinct behavioral changes in mice analogous to symptoms observed in humans with CHF and comorbid depression.

Experimental analysis of R134a flow boiling inside a 5 PPI copper foam

NASA Astrophysics Data System (ADS)

Diani, A.; Mancin, S.; Rossetto, L.

2014-04-01

Heat dissipation is one of the most important issues for the reliability of electronic equipment. Boiling can be a very efficient heat transfer mechanism when used to face with the electronic technology needs of efficient and compact heat sinks. Recently, cellular structured materials both stochastic and periodic, particularly open cell metal foams, have been proposed as possible enhanced surfaces to lower the junction temperatures at high heat fluxes. Up today, most of the research on metal foams only regards single phase flow, whereas the two phase flow is still almost unexplored. This paper presents an experimental study on the heat transfer of R134a during flow boiling inside a 5 PPI (Pores Per linear Inch) copper foam, which is 5 mm high, 10 mm wide and 200 mm long, and it is brazed on a 10 mm thick copper plate. The experimental measurements were carried out by imposing three different heat fluxes (50, 75, and 100 kW m-2) and by varying the refrigerant mass velocity between 50 and 200 kg m-2 s-1 and the vapour quality from 0.2 to 0.90, at constant saturation temperature (30°C). The effects of the refrigerant mass flow rate, heat flux and vapour quality on the heat transfer coefficient, dry out phenomenon, and pressure drop are studied.

Visualization and flow boiling heat transfer of hydrocarbons in a horizontal tube

NASA Astrophysics Data System (ADS)

Yang, Zhuqiang; Bi, Qincheng; Guo, Yong; Liu, Zhaohui; Yan, Jianguo

2013-07-01

Visualizations of a specific hydrocarbon fuel in a horizontal tube with 2.0 mm inside diameter were investigated. The experiments were conducted at mass velocity of 213.4, 426.5 and 640.2 kg/ (m2ṡs), diabatic lengths of 140, 240 and 420 mm under the pressure from 2.0-2.7 MPa. In the sub-pressure conditions, bubbly, intermittent, stratified-wave, churn and annular flow patterns were observed. The frictional pressure drops were also measured to distinguish the patterns. The development of flow patterns and frictional pressure drop were positively related to the mass velocity and the heat flux. However, the diabatic length of the tube takes an important part in the process. The residence time of the fluid does not only affect the transition of the patterns but influence the composition of the fuel manifested by the fuel color and carbon deposit. The special observational phenomenon was obtained for the supercritical pressure fluid. The flow in the tube became fuzzier and pressure drop changed sharply near the pseudocritical point. The flow boiling heat transfer characteristics of the hydrocarbons were also discussed respectively. The curve of critical heat flux about onset of nucleate boiling was plotted with different mass velocities and diabatic tube lengths. And heat transfer characteristics of supercritical fuel were proved to be better than that in subcritical conditions.

Heat Transfer and Fluid Mechanics Institute, Meeting, 25th, University of California, Davis, Calif., June 21-23, 1976, Proceedings

NASA Technical Reports Server (NTRS)

Mckillop, A. A.; Baughn, J. W.; Dwyer, H. A.

1976-01-01

Major research advances in heat transfer and fluid dynamics are outlined, with particular reference to relevant energy problems. Of significant importance are such topics as synthetic fuels in combustion, turbulence models, combustion modeling, numerical methods for interacting boundary layers, and light-scattering diagnostics for gases. The discussion covers thermal convection, two-phase flow and boiling heat transfer, turbulent flows, combustion, and aerospace heat transfer problems. Other areas discussed include compressible flows, fluid mechanics and drag, and heat exchangers. Featured topics comprise heat and salt transfer in double-diffusive systems, limits of boiling heat transfer in a liquid-filled enclosure, investigation of buoyancy-induced flow stratification in a cylindrical plenum, and digital algorithms for dynamic analysis of a heat exchanger. Individual items are announced in this issue.

Dynamic Modelling of the DEP Controlled Boiling in a Microchannel

NASA Astrophysics Data System (ADS)

Lackowski, Marcin; Kwidzinski, Roman

2018-04-01

The paper presents theoretical analysis of flow dynamics in a heated microchannel in which flow rate may be controlled by dielectrophoretic (DEP) forces. Proposed model equations were derived in terms of lumped parameters characterising the system comprising of DEP controller and the microchannel. In result, an equation for liquid height of rise in the controller was obtained from momentum balances in the two elements of the considered system. In the model, the boiling process in the heated section of microchannel is taken into account through a pressure drop, which is a function of flow rate and uniform heat flux. Presented calculation results show that the DEP forces influence mainly the flow rate in the microchannel. In this way, by proper modulation of voltage applied to the DEP controller, it is possible to lower the frequency of Ledinegg instabilities.

Boiling Heat-Transfer Processes and Their Application in the Cooling of High Heat Flux Devices

DTIC Science & Technology

1993-06-01

1991, pp. 395-397. 385. Galloway, J. E. and Mudawar , 1. "Critical Heat Flux Enhancement by Means of Liquid Subcooling and Centrifugal Force Induced...Flow Boiling Heat Transfer for a Spirally Fluted Tube." Heat Tran~ler Engineering, Vol. 13, No.1, 1992, pp. 42-52. 390. Willingham, T. C. and Mudawar

Effect of force fields on pool boiling flow patterns in normal and reduced gravity

NASA Astrophysics Data System (ADS)

di Marco, P.; Grassi, W.

2009-05-01

This paper reports the observations of boiling flow patterns in FC-72, performed during a microgravity experiment, recently flown aboard of Foton-M2 satellite, in some instances with the additional aid of an electrostatic field to replace the buoyancy force. The heater consisted of a flat plate, 20 × 20 mm2, directly heated by direct current. Several levels of liquid subcooling (from 20 to 6 K) and heat fluxes up to 200 kW/m2 were tested. A complete counterpart test, carried out on ground before the mission, allowed direct comparison with terrestrial data. The void fraction in microgravity revealed much larger than in normal gravity condition: this may be attributed to increased bubble coalescence that hinders vapor condensation in the bulk of the subcooled fluid. In several cases, an oscillatory boiling behavior was detected, leading to periodical variation of average wall overheating of some degrees. The electric field confirmed to be very effective, even at low values of applied voltage, in reducing bubble size, thus improving their condensation rate in the bulk fluid, and in enhancing heat transfer performance, suppressing the boiling oscillations and preventing surface dryout.

Numerical Simulation of Pulsation Flow in the Vapour Channel of Short Low Temperature Heat Pipes at High Heat Loads

NASA Astrophysics Data System (ADS)

Seryakov, A. V.; Konkin, A. V.

2017-11-01

The results of the numerical simulation of pulsations in the Laval-liked vapour channel of short low-temperature range heat pipes (HPs) are presented. The numerical results confirmed the experimentally obtained increase of the frequency of pulsations in the vapour channel of short HPs with increasing overheat of the porous evaporator relative to the boiling point of the working fluid. The occurrence of pressure pulsations inside the vapour channel in a short HPs is a complex phenomenon associated with the boiling beginning in the capillary-porous evaporator at high heat loads, and appearance the excess amount of vapour above it, leading to the increase in pressure P to a value at which the boiling point TB of the working fluid becomes higher than the evaporator temperature Tev. Vapour clot spreads through the vapour channel and condense, and then a rarefaction wave return from condenser in the evaporator, the boiling in which is resumed and the next cycle of the pulsations is repeated. Numerical simulation was performed using finite element method implemented in the commercial program ANSYS Multiphisics 14.5 in the two-dimensional setting of axis symmetric moist vapour flow with third kind boundary conditions.

On the definition of dominant force regimes for flow boiling heat transfer by using single mini-tubes

NASA Astrophysics Data System (ADS)

Baba, Soumei; Sawada, Kenichiro; Kubota, Chisato; Kawanami, Osamu; Asano, Hitoshi; Inoue, Koichi; Ohta, Haruhiko

Recent increase in the size of space platforms requires the management of larger amount of waste heat under high heat flux conditions and the transportation of it along a long distance to the radiator. Flow boiling applied to the thermal management system in space attracts much attention as promising means to realize high-performance heat transfer and transport because of large latent heat of vaporization. In microgravity two-phase flow phenomena are quite different from those under 1-g condition because buoyancy effects are significantly reduced and surface tension becomes dominant. By the similar reason, flow boiling characteristics in mini channels are not the same as those in channels of normal sizes. In the present stage, however, the boundary between the regimes of body force dominated and of surface tension dominated is not clear. The design of space thermal devices, operated under the conditions where no effect of gravity is expected, will improve the reliability of their ground tests, provided that the boundaries of dominant force regimes are clarified quantitatively in advance. In flow boiling in mini channels or in parallel channels, back flow could be occurred because of rapid growth of bubbles in a confined space, resulting flow rate fluctuation. Flow boiling heat transfer characteristics in mini channels can be changed considerably by the existence of inlet flow rate fluctuation. It is important to pay attention to experimental accuracy and to use a single circular mini-tube to compare heat transfer characteristics with those of normal size tubes. In the present paper, effects of tube orientations, i.e. vertical upward flow, vertical downward flow and horizontal flow, on flow boiling heat transfer characteristics is investigated for FC72 flowing in single mini-tubes with inner diameters of 0.13 and 0.51 mm to establish a reliable dominant force regime map. If the regime map is described by using dimensionless groups of Bond, Weber and Froude numbers, the boundary of dominant forces of inertia and body force is examined by using the mini-tube of the larger diameter at constant Bond number Bo = 0.51, and the boundary of inertia and surface tension by using the mini-tube of smaller diameter at Bo = 0.033. The influence of inertia is varied by the change of vapor quality, i.e. ratio of vapor mass flow rate to the total, under constant mass velocities, where the velocity of liquid-vapor mixtures is increased with increasing vapor quality. For the tube diameter of 0.51 mm, under low inertia conditions at Froude number Fr < 5, heat transfer coefficients were influenced by the tube orientation, while the heat transfer coefficients were almost independent of the orientation for Fr > 5. The results indicated that the boundary between the body force dominated and the inertia force dominated regimes was given by Froude number as Fr ˜ 5. On the other hand, for tube diameter of 0.13 mm, almost no effect of tube = orientation was observed for all combinations of mass velocity and vapor quality, and heat transfer coefficients were independent of vapor quality under low inertia conditions at Weber number We < 5, and vice versa. The results implied the boundary between the surface tension dominated and the inertia force dominated regimes was represented by We ˜ 5. = In addition, by the reflection of both results on the two-dimensional regime map, the boundary between the surface tension dominated and the body force dominated regimes was approx-imately evaluated as Bo ˜ 0.25 from the crossing point of two boundary lines. This value = located in the range of 0.033 < Bo < 0.51 is consistent with the boundaries between the sur-face tension dominated and the body force dominated regimes classified for the smaller and larger mini-tubes, respectively, under low inertia conditions.

Early Onset of Nucleate Boiling on Gas-covered Biphilic Surfaces.

PubMed

Shen, Biao; Yamada, Masayuki; Hidaka, Sumitomo; Liu, Jiewei; Shiomi, Junichiro; Amberg, Gustav; Do-Quang, Minh; Kohno, Masamichi; Takahashi, Koji; Takata, Yasuyuki

2017-05-17

For phase-change cooling schemes for electronics, quick activation of nucleate boiling helps safeguard the electronics components from thermal shocks associated with undesired surface superheating at boiling incipience, which is of great importance to the long-term system stability and reliability. Previous experimental studies show that bubble nucleation can occur surprisingly early on mixed-wettability surfaces. In this paper, we report unambiguous evidence that such unusual bubble generation at extremely low temperatures-even below the boiling point-is induced by a significant presence of incondensable gas retained by the hydrophobic surface, which exhibits exceptional stability even surviving extensive boiling deaeration. By means of high-speed imaging, it is revealed that the consequently gassy boiling leads to unique bubble behaviour that stands in sharp contrast with that of pure vapour bubbles. Such findings agree qualitatively well with numerical simulations based on a diffuse-interface method. Moreover, the simulations further demonstrate strong thermocapillary flows accompanying growing bubbles with considerable gas contents, which is associated with heat transfer enhancement on the biphilic surface in the low-superheat region.

Nucleate pool boiling: High gravity to reduced gravity; liquid metals to cryogens

NASA Technical Reports Server (NTRS)

Merte, Herman, Jr.

1988-01-01

Requirements for the proper functioning of equipment and personnel in reduced gravity associated with space platforms and future space station modules introduce unique problems in temperature control; power generation; energy dissipation; the storage, transfer, control and conditioning of fluids; and liquid-vapor separation. The phase change of boiling is significant in all of these. Although both pool and flow boiling would be involved, research results to date include only pool boiling because buoyancy effects are maximized for this case. The effective application of forced convection boiling heat transfer in the microgravity of space will require a well grounded and cogent understanding of the mechanisms involved. Experimental results are presented for pool boiling from a single geometrical configuration, a flat surface, covering a wide range of body forces from a/g = 20 to 1 to a/g = 0 to -1 for a cryogenic liquid, and from a/g = 20 to 1 for water and a liquid metal. Similarities in behavior are noted for these three fluids at the higher gravity levels, and may reasonably be expected to continue at reduced gravity levels.

Flow Visualization of Liquid Hydrogen Line Chilldown Tests

NASA Technical Reports Server (NTRS)

Rame, Enrique; Hartwig, Jason W.; McQuillen John B.

2014-01-01

We present experimental measurements of wall and fluid temperature during chill-down tests of a warm cryogenic line with liquid hydrogen. Synchronized video and fluid temperature measurements are used to interpret stream temperature profiles versus time. When cold liquid hydrogen starts to flow into the warm line, a sequence of flow regimes, spanning from all-vapor at the outset to bubbly with continuum liquid at the end can be observed at a location far downstream of the cold inlet. In this paper we propose interpretations to the observed flow regimes and fluid temperature histories for two chilldown methods, viz. trickle (i.e. continuous) flow and pulse flow. Calculations of heat flux from the wall to the fluid versus wall temperature indicate the presence of the transition/nucleate boiling regimes only. The present tests, run at typical Reynolds numbers of approx O(10 (exp 5)), are in sharp contrast to similar tests conducted at lower Reynolds numbers where a well-defined film boiling region is observed.

TVP1022 attenuates cardiac remodeling and kidney dysfunction in experimental volume overload-induced congestive heart failure.

PubMed

Abassi, Zaid A; Barac, Yaron D; Kostin, Sawa; Roguin, Ariel; Ovcharenko, Elena; Awad, Hoda; Blank, Ayelet; Bar-Am, Orit; Amit, Tamar; Schaper, Jutta; Youdim, Moussa; Binah, Ofer

2011-07-01

Despite the availability of many pharmacological and mechanical therapies, the mortality rate among patients with congestive heart failure (CHF) remains high. We tested the hypothesis that TVP1022 (the S-isomer of rasagiline; Azilect), a neuroprotective and cytoprotective molecule, is also cardioprotective in the settings of experimental CHF in rats. In rats with volume overload-induced CHF, we investigated the therapeutic efficacy of TVP1022 (7.5 mg/kg) on cardiac function, structure, biomarkers, and kidney function. Treatment with TVP1022 for 7 days before CHF induction prevented the increase in left ventricular end-diastolic area and end-systolic area, and the decrease in fractional shortening measured 14 days after CHF induction. Additionally, TVP1022 pretreatment attenuated CHF-induced cardiomyocyte hypertrophy, fibrosis, plasma and ventricular B-type natriuretic peptide levels, and reactive oxygen species expression. Further, in CHF rats, TVP1022 decreased cytochrome c and caspase 3 expression, thereby contributing to the cardioprotective efficacy of the drug. TVP1022 also enhanced the urinary Na(+) excretion and improved the glomerular filtration rate. Similar cardioprotective effects were obtained when TVP1022 was given to rats after CHF induction. TVP1022 attenuated the adverse functional, structural, and molecular alterations in CHF, rendering this drug a promising candidate for improving cardiac and renal function in this disease state.

Incremental burden of congestive heart failure among elderly with Alzheimer's.

PubMed

Chhatre, Sumedha; Weiner, Mark G; Jayadevappa, Ravishankar; Johnson, Jerry C

2009-07-01

A complex relationship exists between Alzheimer's disease (AD) and other co-existing co-morbidities such as congestive heart failure (CHF) with implications for health resource utilization (HRU) and cost of care. Study objective was to assess HRU and cost of care in elderly with AD and with or without concomitant CHF. All elderly (> or =65 years) from an academic healthcare system diagnosed with AD in 1999 (n = 904) and matched AD-free controls (n = 3616). Each group was subdivided into those with and without a CHF diagnosis. Costs and HRU were obtained from Medicare databases for 1999 and 2000. Costs and HRU were compared using ANOVA and Wilcoxon rank sum tests. Regressions were used to model the effect of AD and CHF on outcomes. Mean annual cost were 20,888 US dollars for AD + CHF group, 5,473 US dollars for only AD group, 17,700 US dollars for only CHF group and 4,578 US dollars for the control group (no-AD and no-CHF). After adjusting for covariates, AD + CHF group had an eight-fold increase in total cost, while only CHF group had five-fold increase in total cost, compared to the control group. Regressions for inpatient costs, outpatient costs and inpatient pharmacy costs exhibited comparable trends. For elderly AD patients, a co-occurring diagnosis of CHF can result in a substantial increase in cost and HRU. This necessitates additional considerations if health care expenditures are to be reduced, particularly inpatient expenditure.

Surfactant effects on interfacial flow and thermal transport processes during phase change in film boiling

NASA Astrophysics Data System (ADS)

Premnath, Kannan N.; Hajabdollahi, Farzaneh; Welch, Samuel W. J.

2018-04-01

The presence of surfactants in two-phase flows results in the transport and adsorption of surfactants to the interface, and the resulting local interfacial concentration significantly influences the surface tension between the liquid and vapor phases in a fluid undergoing phase change. This computational study is aimed at understanding and elucidating the mechanisms of enhanced flows and thermal transport processes in film boiling due to the addition of surfactants. A change in surface tension results in a change in the critical Rayleigh-Taylor wavelength leading to different bubble release patterns and a change in the overall heat transfer rates. Due to the presence of surfactants, an additional transport mechanism of the Marangoni convection arises from the resulting tangential gradients in the surfactant concentration along the phase interface. Our computational approach to study such phenomena consists of representing the interfacial motion by means of the coupled level set-volume-of-fluid method, the fluid motion via the classical marker-and-cell approach, as well as representations for the bulk transport of energy and surfactants, in conjunction with a phase change model and an interfacial surfactant model. Using such an approach, we perform numerical simulations of surfactant-laden single mode as well as multiple mode film boiling and study the effect of surfactants on the transport processes in film boiling, including bubble release patterns, vapor generation rates, and heat transfer rates at different surfactant concentrations. The details of the underlying mechanisms will be investigated and interpreted.

Relation of vitamin D status to congestive heart failure and cardiovascular events in dogs.

PubMed

Kraus, M S; Rassnick, K M; Wakshlag, J J; Gelzer, A R M; Waxman, A S; Struble, A M; Refsal, K

2014-01-01

Vitamin D plays a pivotal role in cardiac function, and there is increasing evidence that vitamin D deficiency is associated with the development of congestive heart failure (CHF) in people. Serum vitamin D concentration is lower in dogs with CHF compared with unaffected controls and serum vitamin D concentration is associated with clinical outcome in dogs with CHF. Eighty-two client-owned dogs. In this cross-sectional study, we examined the association between circulating 25-hydroxyvitamin D [25(OH)D], a measure of vitamin D status, and CHF in dogs. In the prospective cohort study, we examined whether 25(OH)D serum concentration was associated with clinical outcome in dogs with CHF. Mean 25(OH)D concentration (100 ± 44 nmol/L) in 31 dogs with CHF was significantly lower than that of 51 unaffected dogs (123 ± 42 nmol/L; P = .023). The mean calculated vitamin D intake per kg of metabolic body weight in dogs with CHF was no different from that of unaffected dogs (1.37 ± 0.90 μg/kg metabolic body weight versus 0.98 ± 0.59 μg/kg body weight, respectively, P = .097). There was a significant association of serum 25(OH)D concentration on time to clinical manifestation of CHF or sudden death (P = .02). These findings suggest that low concentrations of 25(OH)D may be a risk factor for CHF in dogs. Low serum 25(OH)D concentration was associated with poor outcome in dogs with CHF. Strategies to improve vitamin D status in some dogs with CHF may prove beneficial without causing toxicity. Copyright © 2013 by the American College of Veterinary Internal Medicine.

Experimental heart failure causes depression-like behavior together with differential regulation of inflammatory and structural genes in the brain

PubMed Central

Frey, Anna; Popp, Sandy; Post, Antonia; Langer, Simon; Lehmann, Marc; Hofmann, Ulrich; Sirén, Anna-Leena; Hommers, Leif; Schmitt, Angelika; Strekalova, Tatyana; Ertl, Georg; Lesch, Klaus-Peter; Frantz, Stefan

2014-01-01

Background: Depression and anxiety are common and independent outcome predictors in patients with chronic heart failure (CHF). However, it is unclear whether CHF causes depression. Thus, we investigated whether mice develop anxiety- and depression-like behavior after induction of ischemic CHF by myocardial infarction (MI). Methods and Results: In order to assess depression-like behavior, anhedonia was investigated by repeatedly testing sucrose preference for 8 weeks after coronary artery ligation or sham operation. Mice with large MI and increased left ventricular dimensions on echocardiography (termed CHF mice) showed reduced preference for sucrose, indicating depression-like behavior. 6 weeks after MI, mice were tested for exploratory activity, anxiety-like behavior and cognitive function using the elevated plus maze (EPM), light-dark box (LDB), open field (OF), and object recognition (OR) tests. In the EPM and OF, CHF mice exhibited diminished exploratory behavior and motivation despite similar movement capability. In the OR, CHF mice had reduced preference for novelty and impaired short-term memory. On histology, CHF mice had unaltered overall cerebral morphology. However, analysis of gene expression by RNA-sequencing in prefrontal cortical, hippocampal, and left ventricular tissue revealed changes in genes related to inflammation and cofactors of neuronal signal transduction in CHF mice, with Nr4a1 being dysregulated both in prefrontal cortex and myocardium after MI. Conclusions: After induction of ischemic CHF, mice exhibited anhedonic behavior, decreased exploratory activity and interest in novelty, and cognitive impairment. Thus, ischemic CHF leads to distinct behavioral changes in mice analogous to symptoms observed in humans with CHF and comorbid depression. PMID:25400562

Health care professionals' attitudes regarding palliative care for patients with chronic heart failure: an interview study.

PubMed

Ziehm, Jeanette; Farin, Erik; Seibel, Katharina; Becker, Gerhild; Köberich, Stefan

2016-08-15

Even though struggling with similar symptom burden, patients with chronic heart failure (CHF) receive less palliative care than patients suffering from malignant diseases. Researchers have found that this might be related to lack of knowledge about palliative care, insufficient interprofessional communication as well as the cyclic course of disease which makes accurate prognosis difficult. However, research findings have shown that patients with CHF benefit from palliative care. As there are no studies for the German health care system this study aimed to assess health care professionals' attitudes regarding palliative care of CHF patients in order to identify barriers and facilitators for this patient group and hence to develop recommendations for improvement of CHF patients' access to palliative care in Germany. Problem-centered interviews with 23 health care professionals involved in care of CHF patients (nurses: hospital, outpatient, heart failure, PC; physicians: hospital and resident cardiologists, general practitioners) were conducted and analysed according to Mayring's qualitative content analysis. Most interviewees perceived a need for palliative care for CHF patients. Regarding barriers patients', public's, and professionals' lack of knowledge of palliative care and CHF; shortcomings in communication and cooperation of different professional groups; inability of cardiology to accept medical limits; difficult prognosis of course of disease; and patients' concerns regarding palliative care were described. Different attitudes regarding appropriate time of initiation of palliative care for CHF patients (late vs. early) were found. Furthermore, better communication and closer cooperation between different professional groups and medical disciplines as well as better education about palliative care and CHF for professionals, patients, and public were cited. Palliative care for CHF patients is a neglected topic in both practice and research and should receive more attention. Barriers to palliative care for CHF patients might be overcome by: better education for the public, patients, and professionals, closer cooperation between the different professional groups involved as well as development of a joint agreement regarding the appropriate time to administer palliative care to CHF patients. DRKS00007119 .

Prospects for Boiling of Subcooled Dielectric Liquids for Supercomputer Cooling

NASA Astrophysics Data System (ADS)

Zeigarnik, Yu. A.; Vasil'ev, N. V.; Druzhinin, E. A.; Kalmykov, I. V.; Kosoi, A. S.; Khodakov, K. A.

2018-02-01

It is shown experimentally that using forced-convection boiling of dielectric coolants of the Novec 649 Refrigerant subcooled relative to the saturation temperature makes possible removing heat flow rates up to 100 W/cm2 from modern supercomputer chip interface. This fact creates prerequisites for the application of dielectric liquids in cooling systems of modern supercomputers with increased requirements for their operating reliability.

Low gravity transfer line chilldown

NASA Technical Reports Server (NTRS)

Antar, Basil N.; Collins, Frank G.; Kawaji, Masahiro

1992-01-01

The progress to date is presented in providing predictive capabilities for the transfer line chilldown problem in low gravity environment. A low gravity experimental set up was designed and flown onboard the NASA/KC-135 airplane. Some results of this experimental effort are presented. The cooling liquid for these experiments was liquid nitrogen. The boiling phenomenon was investigated in this case using flow visualization techniques as well as recording wall temperatures. The flow field was established by injecting cold liquid in a heated tube whose temperature was set above saturation values. The tubes were vertically supported with the liquid injected from the lower end of the tube. The results indicate substantial differences in the flow patterns established during boiling between the ground based, (1-g), experiments and the flight experiments, (low-g). These differences in the flow patterns will be discussed and some explanations will be offered.

The effects of dietary fish oil on exercising skeletal muscle vascular and metabolic control in chronic heart failure rats.

PubMed

Holdsworth, Clark T; Copp, Steven W; Hirai, Daniel M; Ferguson, Scott K; Sims, Gabrielle E; Hageman, Karen S; Stebbins, Charles L; Poole, David C; Musch, Timothy I

2014-03-01

Impaired vasomotor control in chronic heart failure (CHF) is due partly to decrements in nitric oxide synthase (NOS) mediated vasodilation. Exercising muscle blood flow (BF) is augmented with polyunsaturated fatty acid (PUFA) supplementation via fish oil (FO) in healthy rats. We hypothesized that FO would augment exercising muscle BF in CHF rats via increased NO-bioavailability. Myocardial infarction (coronary artery ligation) induced CHF in Sprague-Dawley rats which were subsequently randomized to dietary FO (20% docosahexaenoic acid, 30% eicosapentaenoic acid, n = 15) or safflower oil (SO, 5%, n = 10) for 6-8 weeks. Mean arterial pressure (MAP), blood [lactate], and hindlimb muscles BF (radiolabeled microspheres) were determined at rest, during treadmill exercise (20 m·min(-1), 5% incline) and exercise + N(G)-nitro-l-arginine-methyl-ester (l-NAME) (a nonspecific NOS inhibitor). FO did not change left ventricular end-diastolic pressure (SO: 14 ± 2; FO: 11 ± 1 mm Hg, p > 0.05). During exercise, MAP (SO: 128 ± 3; FO: 132 ± 3 mm Hg) and blood [lactate] (SO: 3.8 ± 0.4; FO: 4.6 ± 0.5 mmol·L(-1)) were not different (p > 0.05). Exercising hindlimb muscle BF was lower in FO than SO (SO: 120 ± 11; FO: 93 ± 4 mL·min(-1)·100 g(-1), p < 0.05) but was not differentially affected by l-NAME. Specifically, 17 of 28 individual muscle BF's were lower (p < 0.05) in FO demonstrating that PUFA supplementation with FO in CHF rats does not augment muscle BF during exercise but may lower metabolic cost.

Independent prognostic importance of respiratory instability and sympathetic nerve activity in patients with chronic heart failure.

PubMed

Asanoi, Hidetsugu; Harada, Daisuke; Oda, Yoshitaka; Ueno, Hiroshi; Takagawa, Junya; Ishise, Hisanari; Goso, Yukiko; Joho, Shuji; Inoue, Hiroshi

2017-11-01

Respiratory instability in chronic heart failure (CHF) is characterized by irregularly rapid respiration or non-periodic breathing rather than by Cheyne-Stokes respiration. We developed a new quantitative measure of respiratory instability (RSI) and examined its independent prognostic impact upon CHF. In 87 patients with stable CHF, respiratory flow and muscle sympathetic nerve activity (MSNA) were simultaneously recorded. RSI was calculated from the frequency distribution of respiratory spectral components and very low frequency components. During a mean follow-up of 85±38 months, 24 patients died. Sixteen patients who died of cardiac causes had a lower RSI (16±6 vs. 30±21, p<0.01), a lower specific activity scale (4.3±1.4 Mets vs. 5.7±1.4 Mets, p<0.005), a higher MSNA burst area (16±5% vs. 11±4%, p<0.001), and a higher brain natriuretic peptide (BNP) level (514±559pg/ml vs. 234±311pg/ml, p<0.05) than 71 patients who did not die of cardiac causes. Multivariate analysis revealed that RSI (p=0.015), followed by MSNA burst area (p=0.033), was an independent predictor of subsequent all-cause deaths and that RSI (p=0.026), MSNA burst area (p=0.001), and BNP (p=0.048) were independent predictors of cardiac deaths. Patients at very high risk of fatal outcome could be identified by an RSI<20. The daytime respiratory instability quantified by a new measure of RSI has prognostic importance independent of sympathetic nerve activation in patients with clinically stable CHF. An RSI of <20 identifies patients at very high risk for subsequent all-cause and cardiovascular death. Copyright © 2017. Published by Elsevier Ltd.

The Renal Arterial Resistance Index Predicts Worsening Renal Function in Chronic Heart Failure Patients

PubMed Central

Iacoviello, Massimo; Monitillo, Francesco; Leone, Marta; Citarelli, Gaetano; Doronzo, Annalisa; Antoncecchi, Valeria; Puzzovivo, Agata; Rizzo, Caterina; Lattarulo, Maria Silvia; Massari, Francesco; Caldarola, Pasquale; Ciccone, Marco Matteo

2016-01-01

Background/Aim The renal arterial resistance index (RRI) is a Doppler measure, which reflects abnormalities in the renal blood flow. The aim of this study was to verify the value of RRI as a predictor of worsening renal function (WRF) in a group of chronic heart failure (CHF) outpatients. Methods We enrolled 266 patients in stable clinical conditions and on conventional therapy. Peak systolic velocity and end diastolic velocity of a segmental renal artery were obtained by pulsed Doppler flow, and RRI was calculated. Creatinine serum levels were evaluated at baseline and at 1 year, and the changes were used to assess WRF occurrence. Results During follow-up, 34 (13%) patients showed WRF. RRI was associated with WRF at univariate (OR: 1.13; 95% CI: 1.07–1.20) as well as at a forward stepwise multivariate logistic regression analysis (OR: 1.09; 95% CI: 1.03–1.16; p = 0.005) including the other univariate predictors. Conclusions Quantification of arterial renal perfusion provides a new parameter that independently predicts the WRF in CHF outpatients. Its possible role in current clinical practice to better define the risk of cardiorenal syndrome progression is strengthened. PMID:27994601

Methods for calculating conjugate problems of heat transfer

NASA Astrophysics Data System (ADS)

Kalinin, E. K.; Dreitser, G. A.; Kostiuk, V. V.; Berlin, I. I.

Methods are examined for calculating various conjugate problems of heat transfer in channels and closed vessels in cases of single-phase and two-phase flow in steady and unsteady conditions. The single-phase-flow studies involve the investigation of gaseous and liquid heat-carriers in pipes, annular and plane channels, and pipe bundles in cases of cooling and heating. General relationships are presented for heat transfer in cases of film, transition, and nucleate boiling, as well as for boiling crises. Attention is given to methods for analyzing the filling and cooling of conduits and tanks by cryogenic liquids; and ways to intensify heat transfer in these conditions are examined.

Flow boiling with enhancement devices for cold plate coolant channel design

NASA Technical Reports Server (NTRS)

Boyd, Ronald D., Sr.

1989-01-01

A research program to study the effect of enhancement devices on flow boiling heat transfer in coolant channels, which are heated either from the top side or uniformly, is discussed. Freon 11 is the working fluid involved. The specific objectives are: (1) examine the variations in both the mean and local (axial and circumferential) heat transfer coefficients for a circular coolant channel with either smooth walls or with both a twisted tape and spiral finned walls, (2) examine the effect channel diameter (and the length-to-diameter aspect ratio) variations for the smooth wall channel, and (3) develop an improved data reduction analysis.

Energy conversion system involving change in the density of an upwardly moving liquid

DOEpatents

Petrick, Michael

1989-01-01

A system for converting thermal energy into electrical energy includes a fluid reservoir, a relatively high boiling point fluid such as lead or a lead alloy within the reservoir, a downcomer defining a vertical fluid flow path communicating at its upper end with the reservoir and an upcomer defining a further vertical fluid flow path communicating at its upper end with the reservoir. A variable area nozzle of rectangular section may terminate the upper end of the upcomer and the lower end of the of the downcomer communicates with the lower end of the upcomer. A mixing chamber is located at the lower end portion of the upcomer and receives a second relatively low boiling point fluid such as air, the mixing chamber serving to introduce the low boiling point fluid into the upcomer so as to produce bubbles causing the resultant two-phase fluid to move at high velocity up the upcomer. Means are provided for introducing heat into the system preferably between the lower end of the downcomer and the lower end of the upcomer. Power generating means are associated with the one of the vertical fluid flow paths one such power generating means being a magneto hydrodynamic electrical generator.

Variable Flow Pathways and Geochemical History of Seepage Under Mississippi River Levees: 2011, 2015, and 2016 Floods

NASA Astrophysics Data System (ADS)

Voll, K.; Davidson, G. R.; Borrok, D. M.; Corcoran, M. K.; Kelley, J.; Ma, L.

2017-12-01

Seepage beneath levees during flood stage is a concern when piping occurs, creating channels under the levee and forming sand boils where transported sediments discharge. The flow depth beneath a levee varies with surface geology, following deeper paths where the levee sits on channel fill deposits and shallower paths where it sits on sandbar deposits. Piping along shallow pathways poses an increased risk of levee failure. The Lower Mississippi River Valley alluvial aquifer is geochemically stratified, with reducing waters at greater depth, resulting in unique geochemical signatures for water passing beneath the Mississippi River levee along variable flow paths. Sampling from sand boils and flowing relief wells north of Vicksburg, MS, during the 2011, 2015, and 2016 flood events demonstrates the utility of using the geochemistry of discharge water to identify different flow pathways, and to provide greater insight on the variable water-rock interactions as a function of depth. Relief wells discharge water mainly from deeper zones, reflected by low redox potential, high Fe and As, and low 87Sr/86Sr ratios. High variability in As concentrations may result from varying degrees of reductive dissolution of Fe and Mn and release of co-precipitated As. At shallower depths the aquifer is mostly oxic, lower in Fe, As, and bicarbonate, and higher in sulfate concentrations and 87Sr/86Sr ratios. The geochemical signatures of sand-boil discharge varied between boils that were short distances apart. Water samples plotted on a Piper Diagram fell along two distinct trends starting with river water and diverging along pathways reflecting unique water-rock interaction at different depths. Strontium isotope ratios indicate differences in geochemistry are not just from variable redox reactions, but also reflect dissolution of primary minerals of unique composition or provenance. Oxygen and hydrogen isotopes of all subsurface samples reflect an unexpected level of evaporation of river water prior to recharge to the aquifer, attributed to the presence of numerous water-filled depressions between the river channel and levee system. Tritium levels from wells and boils ranged from 2.3 to 7.4 TU, with some high values coming from deeper zones indicating localized variation in the residence time of water at equal depths beneath levees.

Urinary Proteolytic Activation of Renal Epithelial Na+ Channels in Chronic Heart Failure.

PubMed

Zheng, Hong; Liu, Xuefei; Sharma, Neeru M; Li, Yulong; Pliquett, Rainer U; Patel, Kaushik P

2016-01-01

One of the key mechanisms involved in renal Na(+) retention in chronic heart failure (CHF) is activation of epithelial Na(+) channels (ENaC) in collecting tubules. Proteolytic cleavage has an important role in activating ENaC. We hypothesized that enhanced levels of proteases in renal tubular fluid activate ENaC, resulting in renal Na(+) retention in rats with CHF. CHF was produced by left coronary artery ligation in rats. By immunoblotting, we found that several urinary serine proteases were significantly increased in CHF rats compared with sham rats (fold increases: furin 6.7, prostasin 23.6, plasminogen 2.06, and plasmin 3.57 versus sham). Similar increases were observed in urinary samples from patients with CHF. Whole-cell patch clamp was conducted in cultured renal collecting duct M-1 cells to record Na(+) currents. Protease-rich urine (from rats and patients with CHF) significantly increased the Na(+) inward current in M-1 cells. Two weeks of protease inhibitor treatment significantly abrogated the enhanced diuretic and natriuretic responses to ENaC inhibitor benzamil in rats with CHF. Increased podocyte lesions were observed in the kidneys of rats with CHF by transmission electron microscopy. Consistent with these results, podocyte damage markers desmin and podocin expressions were also increased in rats with CHF (increased ≈2-folds). These findings suggest that podocyte damage may lead to increased proteases in the tubular fluid, which in turn contributes to the enhanced renal ENaC activity, providing a novel mechanistic insight for Na(+) retention commonly observed in CHF. © 2015 American Heart Association, Inc.

Urinary proteolytic activation of renal epithelial Na+ channels in chronic heart failure

PubMed Central

Zheng, Hong; Liu, Xuefei; Sharma, Neeru M.; Li, Yulong; Pliquett, Rainer U; Patel, Kaushik P.

2015-01-01

One of the key mechanisms involved in renal Na+ retention in chronic heart failure (CHF) is activation of epithelial Na+ channels (ENaC) in collecting tubules. Proteolytic cleavage has an important role in activating ENaC. We hypothesized that enhanced levels of proteases in renal tubular fluid activate ENaC resulting in renal Na+ retention in rats with CHF. CHF was produced by left coronary artery ligation in rats. By immunoblotting, we found that several urinary serine proteases were significantly increased in CHF rats compared to sham rats (fold increases: furin 6.7, prostasin 23.6, plasminogen 2.06 and plasmin 3.57 vs. sham). Similar increases were observed in urinary samples from patients with CHF. Whole-cell patch-clamp was conducted in cultured renal collecting duct M-1 cells to record Na+ currents. Protease-rich urine (from rats and patients with CHF) significantly increased the Na+ inward current in M-1 cells. Two weeks of protease inhibitor treatment significantly abrogated the enhanced diuretic and natriuretic responses to ENaC inhibitor benzamil in rats with CHF. Increased podocyte lesions were observed in the kidneys of rats with CHF by transmission electron microscopy. Consistent with these results, podocyte damage markers desmin and podocin expressions were also increased in rats with CHF (increased ~2 folds). These findings suggest that podocyte damage may lead to increased proteases in the tubular fluid which in turn contributes to the enhanced renal ENaC activity, providing a novel mechanistic insight for Na+ retention commonly observed in CHF. PMID:26628676

Abnormalities of capillary microarchitecture in a rat model of coronary ischemic congestive heart failure

PubMed Central

Chen, Jiqiu; Yaniz-Galende, Elisa; Kagan, Heather J.; Liang, Lifan; Hekmaty, Saboor; Giannarelli, Chiara

2015-01-01

The aim of the present study is to explore the role of capillary disorder in coronary ischemic congestive heart failure (CHF). CHF was induced in rats by aortic banding plus ischemia-reperfusion followed by aortic debanding. Coronary arteries were perfused with plastic polymer containing fluorescent dye. Multiple fluorescent images of casted heart sections and scanning electric microscope of coronary vessels were obtained to characterize changes in the heart. Cardiac function was assessed by echocardiography and in vivo hemodynamics. Stenosis was found in all levels of the coronary arteries in CHF. Coronary vasculature volume and capillary density in remote myocardium were significantly increased in CHF compared with control. This occurred largely in microvessels with a diameter of ≤3 μm. Capillaries in CHF had a tortuous structure, while normal capillaries were linear. Capillaries in CHF had inconsistent diameters, with assortments of narrowed and bulged segments. Their surfaces appeared rough, potentially indicating endothelial dysfunction in CHF. Segments of main capillaries between bifurcations were significantly shorter in length in CHF than in control. Transiently increasing preload by injecting 50 μl of 30% NaCl demonstrated that the CHF heart had lower functional reserve; this may be associated with congestion in coronary microcirculation. Ischemic coronary vascular disorder is not limited to the main coronary arteries, as it occurs in arterioles and capillaries. Capillary disorder in CHF included stenosis, deformed structure, proliferation, and roughened surfaces. This disorder in the coronary artery architecture may contribute to the reduction in myocyte contractility in the setting of heart failure. PMID:25659485

Experimental Study of a Nitrogen Natural Circulation Loop at Low Heat Flux

NASA Astrophysics Data System (ADS)

Baudouy, B.

2010-04-01

A natural convection circulation loop in liquid nitrogen, i.e. an open thermosiphon flow configuration, has been investigated experimentally near atmospheric pressure. The experiments were conducted on a 2 m high loop with a copper tube of 10 mm inner diameter uniformly heated over a length of 0.95 m. Evolution of the total mass flow rate of the loop and the pressure difference along the tube are described. We also report the boiling curves where single phase and two-phase flows are identified with increasing heat flux. We focus our heat transfer analysis on the single phase regime where mixed convection is encountered. A heat transfer coefficient correlation is proposed. We also examine the boiling incipience as a function of the tube height.

The SMART personalised self-management system for congestive heart failure: results of a realist evaluation.

PubMed

Bartlett, Yvonne K; Haywood, Annette; Bentley, Claire L; Parker, Jack; Hawley, Mark S; Mountain, Gail A; Mawson, Susan

2014-11-25

Technology has the potential to provide support for self-management to people with congestive heart failure (CHF). This paper describes the results of a realist evaluation of the SMART Personalised Self-Management System (PSMS) for CHF. The PSMS was used, at home, by seven people with CHF. Data describing system usage and usability as well as questionnaire and interview data were evaluated in terms of the context, mechanism and outcome hypotheses (CMOs) integral to realist evaluation. The CHF PSMS improved heart failure related knowledge in those with low levels of knowledge at baseline, through providing information and quizzes. Furthermore, participants perceived the self-regulatory aspects of the CHF PSMS as being useful in encouraging daily walking. The CMOs were revised to describe the context of use, and how this influences both the mechanisms and the outcomes. Participants with CHF engaged with the PSMS despite some technological problems. Some positive effects on knowledge were observed as well as the potential to assist with changing physical activity behaviour. Knowledge of CHF and physical activity behaviour change are important self-management targets for CHF, and this study provides evidence to direct the further development of a technology to support these targets.

Increase in atmospheric CHF2Cl (HCFC-22) over southern California from 1985 to 1990

NASA Technical Reports Server (NTRS)

Irion, Fredrick W.; Brown, Margaret; Toon, Geoffrey C.; Gunson, Michael R.

1994-01-01

Column densities of CHF2Cl (HCFC-22) have been measured over Table Mountain Facility (TMF), Wrightwood, California (34.4 deg N) using the Atmospheric Trace Molecule Spectroscopy (ATMOS) Fourier-transform infrared (FTIR) spectrometer. Between October 1985 and July 1990, the exponential column increase rate was (6.7 +/- 0.5)%/yr. Additionally, column measurements of CHF2Cl over McMurdo Sound, Antarctica (78 deg S) in September and October 1986 by the MarkIV FTIR spectrometer were used to derive a south-north interhemispheric ratio of (0.86 +/- 0.08). Model calculations investigated the feasibility of using CHF2Cl column measurements with a predicted global OH field to determine a globally averaged chemical lifetime for CHF2Cl, or equivalently, an estimate of the OH field using a predicted lifetime. The current uncertainty in historical CHF2Cl emissions is too large for CHF2Cl to be used to infer adequately either the lifetime or the OH field.

Liquid metal boiling inception

NASA Technical Reports Server (NTRS)

Sabin, C. M.; Poppendiek, H. F.; Mouritzen, G.; Meckel, P. T.; Cloakey, J. E.

1972-01-01

An experimental study of the inception of boiling in potassium in forced convection is reported. The boiler consisted of a 0.19-inch inside diameter, niobium-1% zirconium boiler tube approximately six feet long. Heating was accomplished by direct electrical tube wall conduction. Experiments were performed with both all-liquid fill and two-phase fill startup sequences and with a range of flow rates, saturation temperatures, inert gas levels, and fill liquid temperatures. Superheat of the liquid above the equilibrium saturation temperature was observed in all the experiments. Incipient boiling liquid superheat ranged from a few degrees to several hundred. Comparisons of these data with other data and with several analytical treatments are presented.

Experimental and numerical investigation of HyperVapotron heat transfer

NASA Astrophysics Data System (ADS)

Wang, Weihua; Deng, Haifei; Huang, Shenghong; Chu, Delin; Yang, Bin; Mei, Luoqin; Pan, Baoguo

2014-12-01

The divertor first wall and neutral beam injection (NBI) components of tokamak devices require high heat flux removal up to 20-30 MW m-2 for future fusion reactors. The water cooled HyperVapotron (HV) structure, which relies on internal grooves or fins and boiling heat transfer to maximize the heat transfer capability, is the most promising candidate. The HV devices, that are able to transfer large amounts of heat (1-20 MW m-2) efficiently, have therefore been developed specifically for this application. Until recently, there have been few attempts to observe the detailed bubble characteristics and vortex evolvement of coolant flowing inside their various parts and understand of the internal two-phase complex heat transfer mechanism behind the vapotron effect. This research builds the experimental facilities of HyperVapotron Loop-I (HVL-I) and Pressure Water HyperVapotron Loop-II (PWHL-II) to implement the subcooled boiling principle experiment in terms of typical flow parameters, geometrical parameters of test section and surface heat flux, which are similar to those of the ITER-like first wall and NBI components (EAST and MAST). The multiphase flow and heat transfer phenomena on the surface of grooves and triangular fins when the subcooled water flowed through were observed and measured with the planar laser induced fluorescence (PLIF) and high-speed photography (HSP) techniques. Particle image velocimetry (PIV) was selected to reveal vortex formation, the flow structure that promotes the vapotron effect during subcooled boiling. The coolant flow data for contributing to the understanding of the vapotron phenomenon and the assessment of how the design and operational conditions that might affect the thermal performance of the devices were collected and analysed. The subcooled flow boiling model and methods of HV heat transfer adopted in the considered computational fluid dynamics (CFD) code were evaluated by comparing the calculated wall temperatures with the experimentally measured values. It was discovered that the bubble and vortex characteristics in the HV are clearly heavily dependent on the internal geometry, flow conditions and input heat flux. The evaporation latent heat is the primary heat transfer mechanism of HV flow under the condition of high heat flux, and the heat transfer through convection is very limited. The percentage of wall heat flux going into vapour production is almost 70%. These relationships between the flow phenomena and thermal performance of the HV device are essential to study the mechanisms for the flow structure alterations for design optimization and improvements of the ITER-like devices' water cooling structure and plasma facing components for future fusion reactors.

Preparation of composite micro/nano structure on the silicon surface by reactive ion etching: Enhanced anti-reflective and hydrophobic properties

NASA Astrophysics Data System (ADS)

Zeng, Yu; Fan, Xiaoli; Chen, Jiajia; He, Siyu; Yi, Zao; Ye, Xin; Yi, Yougen

2018-05-01

A silicon substrate with micro-pyramid structure (black silicon) is prepared by wet chemical etching and then subjected to reactive ion etching (RIE) in the mixed gas condition of SF6, CHF3 and He. We systematically study the impacts of flow rates of SF6, CHF3 and He, the etching pressure and the etching time on the surface morphology and reflectivity through various characterizations. Meanwhile, we explore and obtain the optimal combination of parameters for the preparation of composite structure that match the RIE process based on the basis of micro-pyramid silicon substrate. The composite sample prepared under the optimum parameters exhibits excellent anti-reflective performance, hydrophobic, self-cleaning and anti-corrosive properties. Based on the above characteristics, the composite micro/nano structure can be applied to solar cells, photodetectors, LEDs, outdoor devices and other important fields.

The startup of the Dodewaard natural circulation boiling water reactor -- Experiences

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nissen, W.H.M.; Van Der Voet, J.; Karuza, J.

1994-07-01

Because of its similarity to the simplified boiling water reactor (SBWR), the Dodewaard natural circulation boiling water reactor (BWR) is of special interest to further development of the SBWR design. It has become especially important to gain more insight into the Dodewaard BWR behavior during startup, paying special attention to its stability. Therefore, special instrumentation was used by means of which a series of measurements were taken during the two startups in February and June 1992. The results obtained from these measurements are used to deepen insight into the recirculation flow and the stability of the reactor during startup undermore » conditions with a normal pressure/power trajectory. They have already shown a very early recirculation flow onset during low-power operation and no indication of reactor instability. Furthermore, they will be used as a basis for the research program investigating the reactor behavior under different pressure/power conditions, which is scheduled for next year.« less

Plasma sRAGE and N-(carboxymethyl) lysine in patients with CHF and/or COPD.

PubMed

Boschetto, Piera; Campo, Ilaria; Stendardo, Mariarita; Casimirri, Enrico; Tinelli, Carmine; Gorrini, Marina; Ceconi, Claudio; Fucili, Alessandro; Potena, Alfredo; Papi, Alberto; Ballerin, Licia; Fabbri, Leonardo M; Luisetti, Maurizio

2013-06-01

Knowledge of the role of the receptor for advanced glycation end products (RAGE), particularly its soluble form (sRAGE), and of its advanced glycation end product (AGE) ligand, N-(carboxymethyl)lysine adducts (CML), is limited in chronic heart failure (CHF) and in chronic obstructive pulmonary disease (COPD). We evaluated whether the AGE/RAGE system is activated in stable CHF and COPD, and whether plasma sRAGE and CML levels are affected by clinical and functional parameters. We measured plasma levels of sRAGE and CML using a sandwich enzyme-linked immunosorbent assay (ELISA) in 143 subjects, aged ≥ 65 years, divided into five groups: 58 with CHF, 23 with COPD, 27 with CHF+COPD and 35 controls (17 healthy smokers and 18 healthy nonsmokers). Individuals with diabetes were excluded from the study. Plasma levels of sRAGE and CML were higher in CHF patients than in controls [sRAGE: 0.48 (0.37-0.83) vs. 0.42 (0.29-0.52) ng/mL, P = 0.01; CML: 1.95 (1.58-2.38) vs. 1.68 (1.43-2.00) ng/mL, P = 0.01]. By contrast, sRAGE and CML were not different between both COPD and CHF+COPD patients and controls (P > 0.05). N-terminal pro-brain natriuretic peptide (Nt-pro BNP) correlated with sRAGE, but not with CML, in the patient groups: CHF (r = 0.43, P < 0.001), COPD (r = 0.77, P < 0.0001) and CHF/COPD (r = 0.43, P = 0.003). Plasma levels of sRAGE and CML are increased in CHF, but not in COPD patients. The robust association between NT-pro BNP, a diagnostic and prognostic marker in CHF, and sRAGE concentrations might suggest a possible BNP pathway of amplification of inflammation via the AGE/RAGE system. © 2013 Stichting European Society for Clinical Investigation Journal Foundation. Published by John Wiley & Sons Ltd.

SP-B and SP-C Containing New Synthetic Surfactant for Treatment of Extremely Immature Lamb Lung

PubMed Central

Sato, Atsuyasu; Ikegami, Machiko

2012-01-01

Although superiority of synthetic surfactant over animal-driven surfactant has been known, there is no synthetic surfactant commercially available at present. Many trials have been made to develop synthetic surfactant comparable in function to animal-driven surfactant. The efficacy of treatment with a new synthetic surfactant (CHF5633) containing dipalmitoylphosphatidylcholine, phosphatidylglycerol, SP-B analog, and SP-C analog was evaluated using immature newborn lamb model and compared with animal lung tissue-based surfactant Survanta. Lambs were treated with a clinical dose of 200 mg/kg CHF5633, 100 mg/kg Survanta, or air after 15 min initial ventilation. All the lambs treated with air died of respiratory distress within 90 min of age. During a 5 h study period, Pco2 was maintained at 55 mmHg with 24 cmH2O peak inspiratory pressure for both groups. The preterm newborn lamb lung functions were dramatically improved by CHF5633 treatment. Slight, but significant superiority of CHF5633 over Survanta was demonstrated in tidal volume at 20 min and dynamic lung compliance at 20 and 300 min. The ultrastructure of CHF5633 was large with uniquely aggregated lipid particles. Increased uptake of CHF5633 by alveolar monocytes for catabolism was demonstrated by microphotograph, which might be associated with the higher treatment dose of CHF5633. The higher catabolism of CHF5633 was also suggested by the similar amount of surfactant lipid in bronchoalveolar lavage fluid (BALF) between CHF5633 and Survanta groups, despite the 2-fold higher treatment dose of CHF5633. Under the present ventilation protocol, lung inflammation was minimal for both groups, evaluated by inflammatory cell numbers in BALF and expression of IL-1β, IL-6, IL-8, and TNFα mRNA in the lung tissue. In conclusion, the new synthetic surfactant CHF5633 was effective in treating extremely immature newborn lambs with surfactant deficiency during the 5 h study period. PMID:22808033

[Treatment motivation in patients with chronic cardiorenal syndrome].

PubMed

Efremova, E V; Shutov, A M; Borodulina, E O

2015-01-01

To study treatment motivation in patients with chronic heart failure (CHF) and in those with CHF concurrent with chronic kidney disease (CKD). A total of 203 patients (130 men and 73 women; mean age, 61.8±9.6 years) with CHF diagnosed and assessed in accordance with the National Guidelines of the All-Russian Research Society of Cardiology and the Heart Failure Society for the diagnosis and treatment of CHF (third edition, 2009) were examined. CKD was diagnosed according to the 2012 National Guidelines of the Research Nephrology Society of Russia. A group of patients with chronic cardiorenal syndrome (CRS) included those with CHF and CKD with a glomerular filtration rate (GFR) of <60 ml/min/1.73 m2. The clinical course of CHF, personality profile, and motivation for non-drug and drug treatments were assessed in patients with chronic CRS. CFR was 67.7±17.2 ml/min/1.73 m2; chronic CRS was observed in 89 (44%) patients. Psychological functioning assessment showed that the patients with chronic CRS as compared with those with CHF without CKD had high anxiety and maladaptive disease attitudes. CHF treatment motivation (compliance with lifestyle modification and medication) was proved inadequate and detected only in 31 (15.3%) patients with CHF regardless of the presence of CKD. The specific features of psychological functioning, which affected treatment motivation, were seen in patients with chronic CRS: those who were lowly motivated had a euphoric attitude towards their disease (p=0.03); those who were satisfactorily motivated showed an emotive accentuation of character (p=0.002). The presence of CKD aggravates the clinical course of CHF and negatively affects the psychological functioning of patients with CHF. The patients with chronic CRS are characterized by a low level of motivation for both drug and non-drug treatments, which should be taken into account when managing this cohort of patients.

On the Application of Image Processing Methods for Bubble Recognition to the Study of Subcooled Flow Boiling of Water in Rectangular Channels

PubMed Central

Paz, Concepción; Conde, Marcos; Porteiro, Jacobo; Concheiro, Miguel

2017-01-01

This work introduces the use of machine vision in the massive bubble recognition process, which supports the validation of boiling models involving bubble dynamics, as well as nucleation frequency, active site density and size of the bubbles. The two algorithms presented are meant to be run employing quite standard images of the bubbling process, recorded in general-purpose boiling facilities. The recognition routines are easily adaptable to other facilities if a minimum number of precautions are taken in the setup and in the treatment of the information. Both the side and front projections of subcooled flow-boiling phenomenon over a plain plate are covered. Once all of the intended bubbles have been located in space and time, the proper post-process of the recorded data become capable of tracking each of the recognized bubbles, sketching their trajectories and size evolution, locating the nucleation sites, computing their diameters, and so on. After validating the algorithm’s output against the human eye and data from other researchers, machine vision systems have been demonstrated to be a very valuable option to successfully perform the recognition process, even though the optical analysis of bubbles has not been set as the main goal of the experimental facility. PMID:28632158

Effect of angiotension II on voltage-gated sodium currents in aortic baroreceptor neurons and arterial baroreflex sensitivity in heart failure rats

PubMed Central

Zhang, Dongze; Liu, Jinxu; Zheng, Hong; Tu, Huiyin; Muelleman, Robert L.; Li, Yu-Long

2016-01-01

Impairment of arterial baroreflex sensitivity is associated with mortality in patients with chronic heart failure (CHF). Elevation of plasma angiotension II (Ang II) contributes to arterial baroreflex dysfunction in CHF. A reduced number of voltage-gated sodium (Nav) channels in aortic baroreceptor neurons are involved in CHF-blunted arterial baroreflex. In this study, we investigated acute effect of Ang II on Nav currents in the aortic baroreceptor neuron and on arterial baroreflex in sham and coronary artery ligation-induced CHF rats. Using Ang II 125I radioimmunoassay, real-time RT-PCR and western blot, we found that Ang II levels, and mRNA and protein expression of angiotension II type 1 receptor (AT1R) in nodose ganglia (NG) from CHF rats were higher than that from sham rats. Local microinjection of Ang II (0.2 nmol) into the NG decreased the arterial baroreflex sensitivity in sham rats, whereas losartan (1 nmol, an AT1R antagonist) improved the arterial baroreflex sensitivity in CHF rats. Data from patch-clamp recording showed that Ang II (100 nM) acutely inhibited Nav currents in the aortic baroreceptor neurons from sham and CHF rats. In particular, inhibitory effect of Ang II on Nav currents in the aortic baroreceptor neurons was larger in CHF rats than that in sham rats. Losartan (1 μM) totally abolished the inhibitory effect of Ang II on Nav currents in sham and CHF aortic baroreceptor neurons. These results suggest that elevation of endogenous Ang II in the NG contributes to impairment of the arterial baroreflex function in CHF rats through inhibiting Nav channels. PMID:25827427

Parametric analyses of DEMO Divertor using two dimensional transient thermal hydraulic modelling

NASA Astrophysics Data System (ADS)

Domalapally, Phani; Di Caro, Marco

2018-05-01

Among the options considered for cooling of the Plasma facing components of the DEMO reactor, water cooling is a conservative option because of its high heat removal capability. In this work a two-dimensional transient thermal hydraulic code is developed to support the design of the divertor for the projected DEMO reactor with water as a coolant. The mathematical model accounts for transient 2D heat conduction in the divertor section. Temperature-dependent properties are used for more accurate analysis. Correlations for single phase flow forced convection, partially developed subcooled nucleate boiling, fully developed subcooled nucleate boiling and film boiling are used to calculate the heat transfer coefficients on the channel side considering the swirl flow, wherein different correlations found in the literature are compared against each other. Correlation for the Critical Heat Flux is used to estimate its limit for a given flow conditions. This paper then investigates the results of the parametric analysis performed, whereby flow velocity, diameter of the coolant channel, thickness of the coolant pipe, thickness of the armor material, inlet temperature and operating pressure affect the behavior of the divertor under steady or transient heat fluxes. This code will help in understanding the basic parameterś effect on the behavior of the divertor, to achieve a better design from a thermal hydraulic point of view.

Organizational structure for chronic heart failure and chronic obstructive pulmonary disease.

PubMed

Rinne, Seppo T; Liu, Chuan-Fen; Wong, Edwin S; Hebert, Paul L; Heidenreich, Paul; Bastian, Lori A; Au, David H

2016-03-01

In contrast to chronic heart failure (CHF), measures of quality of care for chronic obstructive pulmonary disease (COPD) are poor. Our objective was to examine differences in organizational structure available to support quality of care for patients with CHF and COPD. We performed 2 nationwide surveys exploring organizational structure for the management of CHF and COPD. We surveyed the chief of medicine and the chief of cardiology and pulmonary medicine at 120 Veterans Affairs facilities in the United States. Analogous questions about organizational structure that enhanced adherence to guideline-based care were compared between CHF and COPD surveys. We found large and notable differences in the organizational structure for disease management, with systematically less attention given to COPD than CHF. These differences were evident in multiple processes of care. Key differences included fewer facilities: having COPD clinics than CHF clinics (12.7% vs 50.8%; P < .01), relating performance measures with COPD providers than CHF providers (17.1% vs 70%; P < .01), and having home monitoring programs for COPD than for CHF (50.5% vs 87.4%; P < .01). Despite the growing burden of COPD, less organizational structure existed for COPD than CHF. Lack of organizational structure for COPD likely impedes an organization's abilities to encourage high-quality care and avoid recently implemented hospital readmission penalties. Our results suggest the need to develop a systematic approach for healthcare systems to provide essential organizational structure based on the burden of disease in the population.

Efficacy of community-based multidisciplinary disease management of chronic heart failure.

PubMed

Omar, A R; Suppiah, N; Chai, P; Chan, Y H; Seow, Y H; Quek, L L; Poh, K K; Tan, H C

2007-06-01

A multidisciplinary disease management (DM) programme in chronic heart failure (CHF) improves clinical outcome. The efficacy of such a programme in a heterogeneous Asian community is not well established. Therefore, we undertook the evaluation of the efficacy of the multidisciplinary community-based DM CHF programme. This was a prospective study involving 154 patients (54 percent male) with a primary diagnosis of CHF, New York Heart Association functional class III/IV CHF, with left ventricular ejection fraction (LVEF) less than 40 percent. The mean age was 65 +/- 12 years and mean LVEF was 27 +/- 9 percent. We evaluated CHF hospitalisation, quality of life, activity status and quality of care (percentage of patients who received ACE inhibitors/angiotensin receptor blockers (ARB) and beta blockers after a period of six months. At six months, there was improvement in the quality of life and activity status (p < 0.001). ACE inhibitors/ARB were maintained in 97 percent of the patients and there was an increased usage of beta blockers (p-value equals 0.001). The rate of CHF hospitalisation was reduced by 68 percent (p-value is less than 0.001) and there was no mortality. The multidisciplinary DM of CHF in a heterogeneous Asian community showed significant improvement in quality of life, quality of care and reduction in CHF hospitalisation.

Chronic heart failure in Japan: implications of the CHART studies.

PubMed

Shiba, Nobuyuki; Shimokawa, Hiroaki

2008-01-01

The prognosis of patients with chronic heart failure (CHF) still remains poor, despite the recent advances in medical and surgical treatment. Furthermore, CHF is a major public health problem in most industrialized countries where the elderly population is rapidly increasing. Although the prevalence and mortality of CHF used to be relatively low in Japan, the disorder has been markedly increasing due to the rapid aging of the society and the Westernization of lifestyle that facilitates the development of coronary artery disease. The Chronic Heart Failure Analysis and Registry in the Tohoku District (CHART)-1 study was one of the largest cohorts in Japan. The study has clarified the characteristics and prognosis of Japanese patients with CHF, demonstrating that their prognosis was similarly poor compared with those in Western countries. However, we still need evidence for the prevention and treatment of CHF based on the large cohort studies or randomized treatment trials in the Japanese population. Since the strategy for CHF management is now changing from treatment to prevention, a larger-size prospective cohort, called the CHART-2 study, has been initiated to evaluate the risk factors of CHF in Japan. This review summarizes the current status of CHF studies in Japan and discusses their future perspectives.

Surface De-Wetting Based Critical Heat Flux Model Development and Validation

DTIC Science & Technology

2013-02-05

the onset of CHF. When the process of dewetting occurs at contact line and micro region, the temperature of dry spots increases, hence dryout areas...increase and the CHF occurs. Finally, we proposed the CHF mechanism based on the surface dewetting and experimental data. 15. SUBJECT TERMS spray...determines the overall heat transfer, contact line heat transfer wall is critically important to trigger the onset of CHF. When the process of dewetting

A PROCESS FOR SEPARATING AZEOTROPIC MIXTURES BY EXTRACTIVE AND CONVECTIVE DISTILLATION

DOEpatents

Frazer, J.W.

1961-12-19

A method is described for separating an azeotrope of carbon tetrachloride and 1,1,2,2-tetrafluorodinitroethane boiling at 60 deg C. The ndethod comnprises, specifically, feeding azeotrope vapors admixed with a non- reactive gas into an extractive distillation column heated to a temperature preferably somewhat above the boiling point of the constant boiling mixture. A solvent, di-n-butylphthalate, is metered into the column above the gas inlet and permitted to flow downward, earrying with it the higher bomling fraction, while the constituent having the lower boiling point passes out of the top of the column with the non-reactive gas and is collected in a nitrogen cold trap. Other solvents which alter the vapor pressure relationship may be substituted. The method is generally applicable to azeotropic mixtures. A number of specific mixtures whicb may be separated are disclosed. (AEC)

Post-test analysis of dryout test 7B' of the W-1 Sodium Loop Safety Facility Experiment with the SABRE-2P code. [LMFBR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rose, S.D.; Dearing, J.F.

An understanding of conditions that may cause sodium boiling and boiling propagation that may lead to dryout and fuel failure is crucial in liquid-metal fast-breeder reactor safety. In this study, the SABRE-2P subchannel analysis code has been used to analyze the ultimate transient of the in-core W-1 Sodium Loop Safety Facility experiment. This code has a 3-D simple nondynamic boiling model which is able to predict the flow instability which caused dryout. In other analyses dryout has been predicted for out-of-core test bundles and so this study provides additional confirmation of the model.

Different Factors Affecting Human ANP Amyloid Aggregation and Their Implications in Congestive Heart Failure

PubMed Central

Millucci, Lia; Paccagnini, Eugenio; Ghezzi, Lorenzo; Bernardini, Giulia; Braconi, Daniela; Laschi, Marcella; Consumi, Marco; Spreafico, Adriano; Tanganelli, Piero; Lupetti, Pietro; Magnani, Agnese; Santucci, Annalisa

2011-01-01

Aims Atrial Natriuretic Peptide (ANP)-containing amyloid is frequently found in the elderly heart. No data exist regarding ANP aggregation process and its link to pathologies. Our aims were: i) to experimentally prove the presumptive association of Congestive Heart Failure (CHF) and Isolated Atrial Amyloidosis (IAA); ii) to characterize ANP aggregation, thereby elucidating IAA implication in the CHF pathogenesis. Methods and Results A significant prevalence (85%) of IAA was immunohistochemically proven ex vivo in biopsies from CHF patients. We investigated in vitro (using Congo Red, Thioflavin T, SDS-PAGE, transmission electron microscopy, infrared spectroscopy) ANP fibrillogenesis, starting from α-ANP as well as the ability of dimeric β-ANP to promote amyloid formation. Different conditions were adopted, including those reproducing β-ANP prevalence in CHF. Our results defined the uncommon rapidity of α-ANP self-assembly at acidic pH supporting the hypothesis that such aggregates constitute the onset of a fibrillization process subsequently proceeding at physiological pH. Interestingly, CHF-like conditions induced the production of the most stable and time-resistant ANP fibrils suggesting that CHF affected people may be prone to develop IAA. Conclusions We established a link between IAA and CHF by ex vivo examination and assessed that β-ANP is, in vitro, the seed of ANP fibrils. Our results indicate that β-ANP plays a crucial role in ANP amyloid deposition under physiopathological CHF conditions. Overall, our findings indicate that early IAA-related ANP deposition may occur in CHF and suggest that these latter patients should be monitored for the development of cardiac amyloidosis. PMID:21814559

Improvement of exercise capacity of rats with chronic heart failure by long-term treatment with trandolapril

PubMed Central

Yamaguchi, Fuminari; Kawana, Ken-ichiro; Tanonaka, Kouichi; Kamano, Isamu; Igarashi, Takahiro; Gen, Eigyoku; Fujimoto, Yoko; Maki, Toshiyuki; Sanbe, Atsushi; Nasa, Yoshihisa; Takeo, Satoshi

1999-01-01

The effects of long-term treatment with trandolapril, an angiotensin I-converting enzyme inhibitor, on exercise capacity of rats with chronic heart failure (CHF) following coronary artery ligation were examined. CHF was developed by 8 weeks after the coronary artery ligation. The running time of rats with CHF in the treadmill test was shortened to approximately 65% of that of sham-operated rats (16.3±1.2 vs 25.1±1.6 min, n=7; P<0.05). ATP, creatine phosphate (CP), and lactate contents of the gracilis muscle of rats with CHF were similar to those of sham-operated rats before running. After running, ATP and CP were decreased and lactate was increased in both rats with CHF and sham-operated rats. There were no significant differences in the levels of energy metabolites between rats with CHF and sham-operated rats. The rates of decrease in ATP and CP and rate of increase in lactate in the gracilis muscle of rats with CHF during exercise were greater than those of sham operated rats (2.5, 2.0 and 1.5 fold high, respectively), suggesting wastage of energy during exercise in the animals with CHF. Myofibrillar Ca2+-stimulated ATPase (Ca-ATPase) activity of skeletal muscle of rats with CHF was increased over that of the sham-operated control (62.03±1.88 vs 52.34±1.19 μmol Pi mg−1 protein h−1 n=7; P<0.05). The compositions of myosin heavy chain (MHC) isoforms of gracilis muscle were altered by CHF; decreases in MHC types I and IIb and an increase in MHC type IIa were found (P<0.05). Rats with CHF were treated with 1 mg kg−1 day−1 trandolapril from the 2nd to 8th week after surgery. Treatment with trandolapril prolonged the running time, reversed the rates of decrease in ATP and CP and the rate of increase in lactate, and restored the Ca-ATPase activity (51.11±0.56 μmol Pi mg−1 protein h−1, n=7; P<0.05) and composition ratio of MHC isoforms in the gracilis muscle. The results suggest that long-term trandolapril treatment of rats with CHF may restore their ability to utilize energy without wastage and thus improve exercise capacity. PMID:10323590

Interaction of excited He and Ne rare gas metastable atoms with the CHF2Cl molecule

NASA Astrophysics Data System (ADS)

Chérid, M.; Ben Arfa, M.; Driss Khodja, M.

2005-06-01

We studied the Penning ionization of the CHF2Cl molecule with He and Ne metastable atoms (He* and Ne*). We measured the electron kinetic energy and the time-of-flight mass spectra; we also determined the branching ratio for the parent ion and charged CHF+2, CHFCl+, HCF+/CF+ and Cl+ fragments. These data led us to discuss the dissociation channels for all the energetically-accessible electronic states of the ionized molecule. We evidenced a marked contrast in the fragment ion proportions for Ne*-CHF2Cl and He*-CHF2Cl systems, and related it to the difference in polarizability and internal energy of the He* and Ne* atoms.

Direct molecular diffusion and micro-mixing for rapid dewatering of LiBr solution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bigham, S; Isfahani, RN; Moghaddam, S

2014-03-01

A slow molecular diffusion rate often limits the desorption process of an absorbate molecule from a liquid absorbent. To enhance the desorption rate, the absorbent is often boiled to increase the liquid vapor interfacial area. However, the growth of bubbles generated during the nucleate boiling process still remains mass-diffusion limited. Here, it is shown that a desorption rate higher than that of boiling can be achieved, if the vapor absorbent interface is continuously replenished with the absorbate-rich solution to limit the concentration boundary layer growth. The study is conducted in a LiBr-water-solution, in which the water molecules' diffusion rate ismore » quite slow. The manipulation of the vapor solution interface concentration distribution is enabled by the mechanical confinement of the solution flow within microchannels, using a hydrophobic vapor-venting membrane and the implementation of microstructures on the flow channel's bottom wall. The microstructures stretch and fold the laminar streamlines within the solution film and produce vortices. The vortices continuously replace the concentrated solution at the vapor solution interface with the water-rich solution brought from the bottom and middle of the flow channel. The physics of the process is described using a combination of experimental and numerical studies. Published by Elsevier Ltd.« less

Increased Rho kinase activity in congestive heart failure

PubMed Central

Dong, Ming; Liao, James K.; Fang, Fang; Lee, Alex Pui-Wai; Yan, Bryan Ping-Yen; Liu, Ming; Yu, Cheuk-Man

2012-01-01

Aims Rho kinases (ROCKs) are the best characterized effectors of the small G-protein RhoA, and play a role in enhanced vasoconstriction in animal models of congestive heart failure (CHF). This study examined if ROCK activity is increased in CHF and how it is associated with the outcome in CHF. Methods and results Patients admitted with CHF (n =178), disease controls (n =31), and normal subjects (n =30) were studied. Baseline ROCK activity was measured by phosphorylation of themyosin-binding subunit in peripheral leucocytes. The patients were followed up for 14.4 ± 7.2 months (range 0.5–26 months) or until the occurrence of cardiac death. The ROCK activity in CHF patients (2.93 ± 0.87) was significantly higher than that of the disease control (2.06 ± 0.38, P < 0.001) and normal control (1.57 ± 0.43, P < 0.001) groups. Similarly, protein levels of ROCK1 and ROCK2 as well as the activity of RhoA in CHF were significantly higher than in disease controls and normal controls (all P < 0.05). Dyspnoea at rest (β =0.338, P < 0.001), low left ventricular ejection fraction (β = –0.277, P < 0.001), and high creatinine (β =0.202, P =0.006) were independent predictors of the baseline ROCK activity in CHF. Forty-five patients died within 2 years follow-up (25.3%). Combining ROCK activity and N-terminal pro brain natriuretic peptide (NT-proBNP) had an incremental value (log rank χ2 =11.62) in predicting long-term mortality when compared with only NT-proBNP (log rank χ2 =5.16, P < 0.05). Conclusion ROCK activity is increased in CHF and it might be associated with the mortality in CHF. ROCK activity might be a complementary biomarker to CHF risk stratification. PMID:22588320

The Occurrence of Cheyne–Stokes Respiration in Congestive Heart Failure: The Effect of Age

PubMed Central

Peer, Avivit; Lorber, Abraham; Suraiya, Suheir; Malhotra, Atul; Pillar, Giora

2010-01-01

Introduction: Up to 50% of adults with congestive heart failure (CHF) and left ventricular dysfunction demonstrate Cheyne–Stokes respiration (CSR), although the mechanisms remain controversial. Because CSR has been minimally studied in children, we sought to assess the prevalence of CSR in children with low and high output cardiac failure. We hypothesized that the existence of CSR only in children with low output CHF would support the importance of circulatory delay as a CSR mechanism. Methods: Thirty patients participated: 10 children with CHF, 10 matched children with no heart disease, and 10 adults with CHF. All participants underwent an in-laboratory polysomnographic sleep study. Results: CHF children's average age (±SEM) was 3.6 ± 2.1 years vs. 3.7 ± 2 years in the age-matched control group. The average ejection fraction of three children with low output CHF was 22 ± 6.8%. The remaining seven had normal-high cardiac output. Compared to control children, CHF children were tachypneic and tachycardic during stable sleep (55.1 ± 6.7 vs. 26.9 ± 3 breath/min and 127.6 ± 8.7 vs. 97.6 ± 6.9 beats/min, respectively, p < 0.05 for both). They had shorter total sleep time (195 ± 49 vs. 373 ± 16 min, p < 0.05) with a low sleep efficiency of 65.6 ± 6%. None of the children had a pattern of CSR at any time during the studies while the adults with CHF had 40% prevalence of CSR. Conclusions: The complete absence of CSR in our sample of children with CHF compared to the 40% prevalence in the adults with CHF we studied, suggests that CSR may be an age-dependent phenomenon. Thus, we speculate that regardless of the exact mechanism which drives CSR, age is an over-riding factor. PMID:21423443

Anti-rheumatic drug use and risk of hospitalization for congestive heart failure in rheumatoid arthritis.

PubMed

Bernatsky, S; Hudson, M; Suissa, S

2005-05-01

To assess the risk of hospitalization for congestive heart failure (CHF) associated with the use of disease-modifying anti-rheumatic drugs (DMARDs) and other medications used in RA. We used a case-control design nested within an administrative database cohort of patients with rheumatoid arthritis (RA) who were dispensed a DMARD between September 1998 and December 2001. Subjects identified with a prior history of CHF were excluded. For each hospitalized case of CHF identified during follow-up, 10 controls matched on age and time were randomly selected from the cohort. Conditional logistic regression was used to estimate the rate ratio (RR) of hospitalizations for CHF associated with the current use of specific drugs, adjusted for sex and co-morbidity. The cohort included 41 885 patients; 75% were women, with an average age at cohort entry of 51 yr. During follow-up, 520 hospitalizations for CHF occurred, for a rate of 10.1 per 1000 per year. The adjusted RR of CHF for current use of any DMARD was 0.7 (95% CI 0.6-0.9) relative to no current use. By DMARD category, there was evidence of a beneficial effect for both tumour necrosis factor-alpha antagonists (RR 0.5, 95% CI 0.2-0.9) and methotrexate monotherapy (RR 0.8, 95% CI 0.6-1.0). For non-DMARD medications, the rate of CHF was not clearly increased or decreased, except for COX-2 inhibitors. The data suggested an increased risk of CHF with rofecoxib (RR 1.3, 95% CI 1.0-3.1) and a decreased risk of CHF with celecoxib (RR 0.6, 95% CI 0.4, 1.0). The use of DMARDs was associated with a reduction in the risk of hospitalizations for CHF in this RA cohort. The increased risk with rofecoxib alongside a decreased risk with celecoxib suggests the absence of a class effect with respect to COX-II inhibitors for some types of cardiovascular morbidity.

Sex-linked differences in the course of chronic kidney disease and congestive heart failure: a study in 5/6 nephrectomized Ren-2 transgenic hypertensive rats with volume overload induced using aorto-caval fistula.

PubMed

Červenka, Luděk; Škaroupková, Petra; Kompanowska-Jezierska, Elzbieta; Sadowski, Janusz

2016-10-01

The role of hypertension and the renin-angiotensin system (RAS) in sex-related differences in the course of chronic kidney disease (CKD) and congestive heart failure (CHF) remain unclear, especially when the two diseases are combined. In male and female Ren-2 transgenic rats (TGR), a model of hypertension with activation of endogenous RAS, CKD was induced by 5/6 renal mass reduction (5/6 NX) and CHF was elicited by volume overload achieved by creation of an aorto-caval fistula (ACF). The primary aim of the study was to examine long-term CKD- and CHF-related mortality, especially in animals with CKD and CHF combined, with particular interest in the potential sex-related differences. The follow-up period was 23 weeks after the first intervention (5/6 NX). We found, first, that TGR did not exhibit sexual dimorphism in the course of 5/6 NX-induced CKD. Second, in contrast, TGR exhibited important sex-related differences in the course of ACF-induced CHF-related mortality: intact female TGR showed higher survival rate than male TGR. This situation is reversed in the course of combined 5/6 NX-induced CKD and ACF-induced CHF-related mortality: intact female TGR exhibited poorer survival than male TGR. Third, the survival rate in animals with combined 5/6 NX-induced CKD and ACF-induced CHF was significantly worsened as compared with rat groups that were exposed to 'single organ disease'. Collectively, our present results clearly show that CKD aggravates long-term mortality of animals with CHF. In addition, TGR exhibit remarkable sexual dimorphism with respect to CKD- and CHF-related mortality, especially in animals with combined CKD and CHF. © 2016 John Wiley & Sons Australia, Ltd.

FIB-4 stage of liver fibrosis predicts incident heart failure among HIV-infected and uninfected patients.

PubMed

So-Armah, Kaku A; Lim, Joseph K; Lo Re, Vincent; Tate, Janet P; Chang, Chung-Chou H; Butt, Adeel A; Gibert, Cynthia L; Rimland, David; Marconi, Vincent C; Goetz, Matthew B; Rodriguez-Barradas, Maria C; Budoff, Matthew J; Tindle, Hilary A; Samet, Jeffrey H; Justice, Amy C; Freiberg, Matthew S

2017-10-01

Liver fibrosis is common, particularly in individuals who are infected with human immunodeficiency virus (HIV). HIV-infected individuals have excess congestive heart failure (CHF) risk compared with uninfected people. It remains unknown whether liver fibrosis stage influences the CHF risk or if HIV or hepatitis C virus (HCV) infection modifies this association. Our objectives were to assess whether 1) stage of liver fibrosis is independently associated with incident CHF and 2) the association between stage of liver fibrosis and incident CHF is modified by HIV/HCV status. Participants alive on or after April 1, 2003, in the Veterans Aging Cohort Study were included. Those without prevalent cardiovascular disease were followed until their first CHF event, death, last follow-up date, or December 31, 2011. Liver fibrosis was measured using the fibrosis 4 index (FIB-4), which is calculated using age, aminotransferases, and platelets. Cox proportional hazards regression models were adjusted for cardiovascular disease risk factors. Among 96,373 participants over 6.9 years, 3844 incident CHF events occurred. FIB-4 between 1.45 and 3.25 (moderate fibrosis) and FIB-4 > 3.25 (advanced fibrosis/cirrhosis) were associated with CHF (hazard ratio [95% confidence interval], 1.17 [1.07-1.27] and 1.65 [1.43-1.92], respectively). The association of advanced fibrosis/cirrhosis and incident CHF persisted regardless of HIV/HCV status. Moderate and advanced liver fibrosis/cirrhosis are associated with an increased risk of CHF. The association for advanced fibrosis/cirrhosis persists even among participants without hepatitis C and/or HIV infection. Assessing liver health may be important for reducing the risk of future CHF events, particularly among HIV and hepatitis C infected people among whom cardiovascular disease risk is elevated and liver disease is common. (Hepatology 2017;66:1286-1295). © 2017 by the American Association for the Study of Liver Diseases.

Can home care for homebound patients with chronic heart failure reduce hospitalizations and costs?

PubMed

Punchik, Boris; Komarov, Roman; Gavrikov, Dmitry; Semenov, Anna; Freud, Tamar; Kagan, Ella; Goldberg, Yury; Press, Yan

2017-01-01

Congestive heart failure (CHF), a common problem in adults, is associated with multiple hospitalizations, high mortality rates and high costs. To evaluate whether home care for homebound patients with CHF reduces healthcare service utilization and overall costs. A retrospective study of healthcare utilization among homebound patients who received home care for CHF from 2012-1015. The outcome measures were number of hospital admissions per month, total number of hospitalization days and days for CHF only, emergency room visits, and overall costs. A comparison was conducted between the 6-month period prior to entry into home care and the time in home care. Over the study period 196 patients were treated by home care for CHF with a mean age of 79.4±9.5 years. 113 (57.7%) were women. Compared to the six months prior to home care, there were statistically significant decreases in hospitalizations (46.3%), in the number of total in-hospital days (28.7%), in the number of in-hospital days for CHF (66.7%), in emergency room visits (47%), and in overall costs (23.9%). Home care for homebound adults with CHF can reduce healthcare utilization and healthcare costs.

Expression of pericardial fluid T-cells and related inflammatory cytokines in patients with chronic heart failure.

PubMed

Iskandar, Reinard; Liu, Shengchen; Xiang, Fei; Chen, Wen; Li, Liangpeng; Qin, Wei; Huang, Fuhua; Chen, Xin

2017-05-01

Pericardial fluid, as a biochemical indicator of heart status, directly indicates pathological alteration to the heart. The accumulation of pericardial fluid can be attributed to an underlying systemic or local inflammatory process. However, the pericardial fluid expression of cellular surface markers, as well as several cytokines in chronic heart failure (CHF), remain unclear. In order to evaluate these issues further the pericardial fluid expression of several cytokines and the surface expression of activity markers between CHF patients and non-heart failure (NHF) patients were analyzed. The pericardial fluid expression of cytokines was measured by immunofluorescence and biomarker of plasma N-terminal propeptide of B-type natriuretic peptide (NT-proBNP), while pericardial fluid levels of soluble glycoprotein 130 (sgp130) were analyzed by ELISA in 50 CHF and 24 NHF patients. In addition, the surface expression of activation markers for T-cells was measured by immunohistochemistry. Patients with CHF demonstrated increased levels of plasma NT-proBNP and pericardial fluid sgp130. Surface expression of cellular activation markers CD25 and Foxp3 in the pericardial fluid was increased in patients with CHF. Moreover, the pro- and anti-inflammatory cytokines interferon (IFN)-γ, interleukin (IL)-6 and IL-10 in patients with CHF also demonstrated an increased expression within its pericardial fluid. In addition, there was infiltration of inflammatory cells and enhanced expression of inflammatory cytokines in the pericardial fluid of patients with CHF, which may reflect T cell activation, suggesting that systemic inflammation is important in the progression of CHF. This evidence could indicate a possible novel target for future therapeutics and prevention of CHF.

AGXT2 rs37369 polymorphism predicts the renal function in patients with chronic heart failure.

PubMed

Hu, Xiao-Lei; Zeng, Wen-Jing; Li, Mu-Peng; Yang, Yong-Long; Kuang, Da-Bin; Li, He; Zhang, Yan-Jiao; Jiang, Chun; Peng, Li-Ming; Qi, Hong; Zhang, Ke; Chen, Xiao-Ping

2017-12-30

Patients with chronic heart failure (CHF) are often accompanied with varying degrees of renal diseases. The purpose of this study was to identify rs37369 polymorphism of AGXT2 specific to the renal function of CHF patients. A total of 1012 southern Chinese participants, including 487 CHF patients without history of renal diseases and 525 healthy volunteers, were recruited for this study. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was used to determine the genotypes of AGXT2 rs37369 polymorphism. Levels of blood urea nitrogen (BUN) and serum creatinine (SCr) were detected to indicate the renal function of the participants. BUN level was significantly higher in CHF patients without history of renal diseases compared with healthy volunteers (p=0.000). And the similar result was also obtained for SCr (p=0.000). Besides, our results indicated that the level of BUN correlated significantly with SCr in both the CHF patients without renal diseases (r=0.4533, p<0.0001) and volunteers (r=0.2489, p<0.0001). Furthermore, we found that the AGXT2 rs37369 polymorphism could significantly affect the level of BUN in CHF patients without history of renal diseases (p=0.036, AA+AG vs GG). Patients with rs37369 GG genotype showed a significantly reduced level of BUN compared to those with the AA genotype (p=0.024), and the significant difference was still observed in the smokers of CHF patients without renal diseases (p=0.023). In conclusion, we found that CHF might induce the impairment of kidney and cause deterioration of renal function. AGXT2 rs37369 polymorphism might affect the renal function of CHF patients free from renal diseases, especially in patients with cigarette smoking. Copyright © 2017. Published by Elsevier B.V.

Management and outcomes following an acute coronary event in patients with chronic heart failure 1999-2007.

PubMed

Ranasinghe, Isuru; Naoum, Chris; Aliprandi-Costa, Bernadette; Sindone, Andrew P; Steg, P Gabriel; Elliott, John; McGarity, Bruce; Lefkovits, Jeffrey; Brieger, David

2012-05-01

The outcome of patients with chronic heart failure (CHF) following an ischaemic event is poorly understood. We evaluated the management and outcomes of CHF patients presenting with an acute coronary syndrome (ACS) and explored changes in outcomes over time. A total of 5556 patients enrolled in the Australia-New Zealand population of the Global Registry of Acute Coronary Events (GRACE) between 1999 and 2007 were included. Patients with CHF (n = 609) were compared with those without CHF (n = 4947). Patients with CHF were on average 10 years older, were more likely to be female, had more co-morbidities and cardiac risk factors, and were more likely to have a prior history of angina, myocardial infarction, and revascularization by coronary artery bypass graft (CABG) when compared with those without CHF. CHF was associated with a substantial increase in in-hospital renal failure [odds ratio (OR) 1.76, 95% confidence interval (CI) 1.15-2.71], readmission post-discharge (OR 1.47, 95% CI 1.17-1.90), and 6-month mortality (OR 2.25, 95% CI 1.55-3.27). Over the 9 year study period, in-hospital and 6 month mortality in those with CHF declined by absolute rates of 7.5% and 14%, respectively. This was temporally associated with an increase in prescription of thienopyridines, beta-blockers, statins, and angiotensin II receptor blockers, increased rates of coronary angiography, and 31.8% absolute increase in referral rates for cardiac rehabilitation. Acute coronary syndrome patients with pre-existing CHF are a very high risk group and carry a disproportionate mortality burden. Encouragingly, there was a marked temporal improvement in outcomes over a 9 year period with an increase in evidence-based treatments and secondary preventative measures.

Incidence and risk factors for congestive heart failure in patients with early breast cancer who received anthracycline and/or trastuzumab: a big data analysis of the Korean Health Insurance Review and Assessment service database.

PubMed

Choi, Jung Yoon; Cho, Eun Young; Choi, Yoon Ji; Lee, Jeong Hyeon; Jung, Seung Pil; Cho, Kyu Ran; Kim, Chul Yong; Kim, Yeul Hong; Park, Kyong Hwa

2018-05-08

We aimed to analyze the incidence, time to occurrence, and congestive heart failure (CHF) risk factors for early breast cancer patients treated with anthracycline (AC)-based chemotherapy and/or trastuzumab (T) therapy in Korea. We included female patients > 19 years old from the Health Insurance Review and Assessment Service database who had no prior CHF history and had been diagnosed with early breast cancer between January 2007 and October 2016. We included 83,544 patients in our analysis. In terms of crude incidence for CHF, AC followed by T showed the highest incidence (6.3%). However, 3.1 and 4.2% of the patients had CHF due to AC-based chemotherapy and non-AC followed by T, respectively. The median times to occurrence of CHF were different according to adjuvant treatments, approximately 2 years (701.0 days) in the AC-based chemotherapy group vs 1 year (377.5 days) AC followed by T group. T therapy was associated with earlier development of CHF irrespective of previous chemotherapy, but late risk of CHF 1.2 years after T therapy rapidly decreased in both chemotherapy groups. Multivariate Cox regression analysis revealed that the adjusted hazard ratio for CHF was increased in the group of older patients (≥ 65 years old) who underwent AC followed by T therapy, with Charlson comorbidity index scores of ≥ 2. Our study showed that neo-/adjuvant chemotherapy using T irrespective of previous chemotherapy (AC or non-AC) was associated with significantly increased risk of CHF compared with AC-based chemotherapy in Korean patients with early breast cancer.

Numerical Modeling of Propellant Boil-Off in a Cryogenic Storage Tank

NASA Technical Reports Server (NTRS)

Majumdar, A. K.; Steadman, T. E.; Maroney, J. L.; Sass, J. P.; Fesmire, J. E.

2007-01-01

A numerical model to predict boil-off of stored propellant in large spherical cryogenic tanks has been developed. Accurate prediction of tank boil-off rates for different thermal insulation systems was the goal of this collaboration effort. The Generalized Fluid System Simulation Program, integrating flow analysis and conjugate heat transfer for solving complex fluid system problems, was used to create the model. Calculation of tank boil-off rate requires simultaneous simulation of heat transfer processes among liquid propellant, vapor ullage space, and tank structure. The reference tank for the boil-off model was the 850,000 gallon liquid hydrogen tank at Launch Complex 39B (LC- 39B) at Kennedy Space Center, which is under study for future infrastructure improvements to support the Constellation program. The methodology employed in the numerical model was validated using a sub-scale model and tank. Experimental test data from a 1/15th scale version of the LC-39B tank using both liquid hydrogen and liquid nitrogen were used to anchor the analytical predictions of the sub-scale model. Favorable correlations between sub-scale model and experimental test data have provided confidence in full-scale tank boil-off predictions. These methods are now being used in the preliminary design for other cases including future launch vehicles

The dryout region in frictionally heated sliding contacts

NASA Technical Reports Server (NTRS)

Hendricks, R. C.; Braun, J.; Arp, V.; Giarratano, P. J.

1982-01-01

Some conditions under which boiling and two-phase flow can occur in or near a wet sliding contact are determined and illustrated. The experimental apparatus consisted of a tool pressed against an instrumented slider plate and motion picture sequences at 4000 frames/sec. The temperature and photographic data demonstrated surface conditions of boiling, drying, trapped gas evolution (solutions), and volatility of fluid mixture components. The theoretical modeling and analysis are in reasonable agreement with experimental data.

Controlled boiling on Enceladus. 2. Model of the liquid-filled cracks

NASA Astrophysics Data System (ADS)

Ingersoll, Andrew P.; Nakajima, Miki

2016-07-01

Controlled boiling will occur on Enceladus whenever a long, narrow conduit connects liquid water to the vacuum of space. In a companion paper we focus on the upward flow of the vapor and show how it controls the evaporation rate through backpressure, which arises from friction on the walls. In this paper we focus on the liquid and show how it flows through the conduit up to its level of neutral buoyancy. For an ice shell 20 km thick, the liquid water interface could be 2 km below the surface. We find that the evaporating surface can be narrow. There is no need for a large vapor chamber that acts as a plume source. Freezing on the icy walls and the evaporating surface is avoided if the crack width averaged over the length of the tiger stripes is greater than 1 m and the salinity of the liquid is greater than 20 g kg-1. Controlled boiling plays a crucial role in our model, which makes it different from earlier published models. The liquids on Enceladus are boiling because there is no overburden pressure-the saturation vapor pressure is equal to the total pressure. Salinity plays a crucial role in preventing freezing, and we argue that the subsurface oceans of icy satellites can have water vapor plumes only if their salinities are greater than about 20 g kg-1.

Development of Electrical Capacitance Sensors for Accident Tolerant Fuel (ATF) Testing at the Transient Reactor Test (TREAT) Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Maolong; Ryals, Matthew; Ali, Amir

2016-08-01

A variety of instruments are being developed and qualified to support the Accident Tolerant Fuels (ATF) program and future transient irradiations at the Transient Reactor Test (TREAT) facility at Idaho National Laboratory (INL). The University of New Mexico (UNM) is working with INL to develop capacitance-based void sensors for determining the timing of critical boiling phenomena in static capsule fuel testing and the volume-averaged void fraction in flow-boiling in-pile water loop fuel testing. The static capsule sensor developed at INL is a plate-type configuration, while UNM is utilizing a ring-type capacitance sensor. Each sensor design has been theoretically and experimentallymore » investigated at INL and UNM. Experiments are being performed at INL in an autoclave to investigate the performance of these sensors under representative Pressurized Water Reactor (PWR) conditions in a static capsule. Experiments have been performed at UNM using air-water two-phase flow to determine the sensitivity and time response of the capacitance sensor under a flow boiling configuration. Initial measurements from the capacitance sensor have demonstrated the validity of the concept to enable real-time measurement of void fraction. The next steps include designing the cabling interface with the flow loop at UNM for Reactivity Initiated Accident (RIA) ATF testing at TREAT and further characterization of the measurement response for each sensor under varying conditions by experiments and modeling.« less

Analyzing and Post-modelling the High Speed Images of a Wavy Laser Induced Boiling Front

NASA Astrophysics Data System (ADS)

Matti, R. S.; Kaplan, A. F. H.

The boiling front in laser materials processing like remote fusion cutting, keyhole welding or drilling can nowadays be recorded by high speed imaging. It was recently observed that bright waves flow down the front. Several complex physical mechanisms are associated with a stable laser-induced boiling front, like beam absorption, shadowing, heating, ablation pressure, fluid flow, etc. The evidence of dynamic phenomena from high speed imaging is closely linked to these phenomena. As a first step, the directly visible phenomena were classified and analyzed. This has led to the insight that the appearance of steady flow of the bright front peaks is a composition of many short flashing events of 20-50 μs duration, though composing a rather constant melt film flow downwards. Five geometrical front shapes of bright and dark domains were categorized, for example long inclined dark valleys. In addition, the special top and bottom regions of the front are distinguished. As a second step, a new method of post-modelling based on the greyscale variation of the images was applied, to approximately reconstruct the topology of the wavy front and subsequently to calculate the absorption across the front. Despite certain simplifications this kind of analysis provides a variety of additional information, including statistical analysis. In particular, the model could show the sensitivity of front waves to the formation of shadow domains and the robustness of fiber lasers to keep most of an irradiated steel surface in an absorptivity window between 35 to 43%.

High resolution FTIR spectroscopic study of the ν4 band of CH 3CHF 2 enclosed in a flow of cold N 2 gas

NASA Astrophysics Data System (ADS)

Appadoo, Dominique R. T.; Robertson, Evan G.; McNaughton, Don

2003-01-01

An enclosive flow cooling (EFC) cell has been constructed, and coupled to a Brüker IFS 120HR high resolution Fourier transform spectrometer to record rotationally cold absorption spectra of gases of atmospheric interest at high spectral resolution. The new system has been characterized using N 2O, revealing that rotational temperatures as cold as 110 K are readily attainable using liquid nitrogen as a cryogen. Infrared spectra of the ν4 band of 1,1-difluoroethane (R152a), CH 3CHF 2, cooled in the EFC cell have been measured at a resolution of 0.0019 cm-1. Eight hundred and twenty rovibrational transitions of the weak ν4 band with 2⩽ J'⩽46 and Kc'⩽16 were assigned and fitted to Watson's A-reduced Hamiltonian. The ν4 CH 3 symmetric deformation ( a/c-type) was found to be coupled to the ν13 asymmetric deformation ( b-type) via an a-axis Coriolis interaction. In the ensuing analysis, values of spectroscopic constants were obtained for both the ν4 and dark ν13 states. Supporting ab initio calculations up to the MP2/TZV+(3 df,3 p) level are presented.

Pool boiling with high heat flux enabled by a porous artery structure

NASA Astrophysics Data System (ADS)

Bai, Lizhan; Zhang, Lianpei; Lin, Guiping; Peterson, G. P.

2016-06-01

A porous artery structure utilizing the concept of "phase separation and modulation" is proposed to enhance the critical heat flux of pool boiling. A series of experiments were conducted on a range of test articles in which multiple rectangular arteries were machined directly into the top surface of a 10.0 mm diameter copper rod. The arteries were then covered by a 2.0 mm thickness microporous copper plate through silver brazing. The pool wall was fabricated from transparent Pyrex glass to allow a visualization study, and water was used as the working fluid. Experimental results confirmed that the porous artery structure provided individual flow paths for the liquid supply and vapor venting, and avoided the detrimental effects of the liquid/vapor counter flow. As a result, a maximum heat flux of 610 W/cm2 over a heating area of 0.78 cm2 was achieved with no indication of dryout, prior to reaching the heater design temperature limit. Following the experimental tests, the mechanisms responsible for the boiling critical heat flux and performance enhancement of the porous artery structure were analyzed.

R245fa Flow Boiling inside a 4.2 mm ID Microfin Tube

NASA Astrophysics Data System (ADS)

Longo, G. A.; Mancin, S.; Righetti, G.; Zilio, C.

2017-11-01

This paper presents the R245fa flow boiling heat transfer and pressure drop measurements inside a mini microfin tube with internal diameter at the fin tip of 4.2 mm, having 40 fins, 0.15 mm high with a helix angle of 18°. The tube was brazed inside a copper plate and electrically heated from the bottom. Sixteen T-type thermocouples are located in the copper plate to monitor the wall temperature. The experimental measurements were carried out at constant mean saturation temperature of 30 °C, by varying the refrigerant mass velocity between 100 kg m-2 s-1 and 300 kg m-2 s-1, the vapour quality from 0.15 to 0.95, at two different heat fluxes: 30 and 60 kW m-2. The experimental results are presented in terms of two-phase heat transfer coefficient, onset dryout vapour quality, and frictional pressure drop. Moreover, the experimental measurements are compared against the most updated models for boiling heat transfer coefficient and frictional pressure drop estimations available in the open literature for microfin tubes.

Soviet-West German Symposium on Heat Transfer in Cryogenic Systems, 3rd, Kharkov, Ukrainian SSR, Oct. 9-11, 1989, Proceedings

NASA Astrophysics Data System (ADS)

1990-04-01

The papers presented in this volume describe a rotating cryostat for the simulation of mechanical, thermal, and hydraulic processes in superconducting rotors; the problems of cooling the fully superconducting generator stator; an investigation of natural circulation by optical methods; and a method of calculating void fraction for vapor-liquid or gas-liquid flow conditions. Attention is given to an experimental study of the processes of He-3 boiling and condensation, heat transfer in He II at a slow variation of the heat load, an investigation of He II flow crisis in porous media, and cryogenic heat pipes. Other papers are on the stability of rotating superconducting windings for electric machines, the stability of high-temperature superconductors cooled by liquid nitrogen, a calculation of the transpiration cooling of a cylindrical porous wall, and pressure losses in boiling nitrogen flow through horizontal channels.

Radial basis functions in mathematical modelling of flow boiling in minichannels

NASA Astrophysics Data System (ADS)

Hożejowska, Sylwia; Hożejowski, Leszek; Piasecka, Magdalena

The paper addresses heat transfer processes in flow boiling in a vertical minichannel of 1.7 mm depth with a smooth heated surface contacting fluid. The heated element for FC-72 flowing in a minichannel was a 0.45 mm thick plate made of Haynes-230 alloy. An infrared camera positioned opposite the central, axially symmetric part of the channel measured the plate temperature. K-type thermocouples and pressure converters were installed at the inlet and outlet of the minichannel. In the study radial basis functions were used to solve a problem concerning heat transfer in a heated plate supplied with the controlled direct current. According to the model assumptions, the problem is treated as twodimensional and governed by the Poisson equation. The aim of the study lies in determining the temperature field and the heat transfer coefficient. The results were verified by comparing them with those obtained by the Trefftz method.

A Remote Patient Monitoring System for Congestive Heart Failure

PubMed Central

Suh, Myung-kyung; Chen, Chien-An; Woodbridge, Jonathan; Tu, Michael Kai; Kim, Jung In; Nahapetian, Ani; Evangelista, Lorraine S.; Sarrafzadeh, Majid

2011-01-01

Congestive heart failure (CHF) is a leading cause of death in the United States affecting approximately 670,000 individuals. Due to the prevalence of CHF related issues, it is prudent to seek out methodologies that would facilitate the prevention, monitoring, and treatment of heart disease on a daily basis. This paper describes WANDA (Weight and Activity with Blood Pressure Monitoring System); a study that leverages sensor technologies and wireless communications to monitor the health related measurements of patients with CHF. The WANDA system is a three-tier architecture consisting of sensors, web servers, and back-end databases. The system was developed in conjunction with the UCLA School of Nursing and the UCLA Wireless Health Institute to enable early detection of key clinical symptoms indicative of CHF-related decompensation. This study shows that CHF patients monitored by WANDA are less likely to have readings fall outside a healthy range. In addition, WANDA provides a useful feedback system for regulating readings of CHF patients. PMID:21611788

An experimental study of evaporation waves in a superheated liquid

NASA Astrophysics Data System (ADS)

Hill, Larry G.

1990-01-01

Evaporation waves in superheated liquids are studied using a rapid-depressurization facility consisting of a vertical glass test cell situated beneath a large, low-pressure reservoir. The objective of this study is to learn more about the physical mechanisms of explosive boiling (of which an evaporation wave is a specific example), as well as properties of the flow it produces.The test cell is initially sealed from the reservoir by a foil diaphragm, and is partially filled with a volatile liquid (Refrigerant 12 or 114). An experiment is initiated by rupturing the diaphragm via a pneumatically driven cutter. The instrumentation consists of fast-response pressure measurements, high-speed motion pictures, and spark-illuminated still photographs. The liquid temperature is typically 20°C; the liquid superheat is controlled by setting the reservoir pressure to values between vacuum and 1 atm. The pressures subsequent to depressurization are very much less than the critical pressure, and the initial temperatures are sufficiently low that, although the test liquid is highly superheated, the superheat limit is not approached. Evaporation waves in which bubble nucleation within the liquid column is suppressed entirely are considered almost exclusively.When the diaphragm is ruptured, the liquid pressure drops to virtually the reservoir value within a few milliseconds. Provided that the liquid superheat so obtained is sufficiently high, the free surface then erupts in a process known as explosive boiling, which is characterized by violent, fine-scale fragmentation of the superheated liquid and extremely rapid evaporation. The explosive boiling process proceeds as a "wavefront" into the liquid column, producing a highspeed, two-phase flow that travels upward into the low-pressure reservoir, emptying the test cell in a few hundred milliseconds. The speed of the wavefront varies between 0.2 and 0.6 m/s, depending on run conditions; the corresponding two-phase flow varies between about 5 and 35 m/s.In the highest superheat case for the more volatile liquid (Refrigerant 12), explosive boiling usually initiates by the rapid formation of nucleation sites at random spots on the liquid free surface and at the glass/free-surface contact line. Boiling spreads to the remaining surface within 160 [...]. In the highest superheat case for the less volatile liquid (Refrigerant 114), nucleation begins only at the glass/free-surface contact line. Boiling then spreads radially inward toward the center. In the lower superheated cases for both liquids, nucleation begins at one or more sites on the glass/free-surface contact line, and propagates across the free surface.At the higher superheats, explosive boiling initiates within a few milliseconds from diaphragm burst, the same time scale as that of liquid depressurization. No distinction is made between the onset of nucleation and that of explosive boiling. However, if the reservoir pressure is raised above a certain approximate value, the onset of explosive boiling is delayed. During the delay period, relatively slow bubbling (initiated at one or more nucleation sites at the glass/free-surface contact line) occurs, and a cluster of bubbles forms in the vicinity of the initial site. The bubble cluster then "explodes," marking the transition to explosive boiling. The delay period increases significantly as the reservoir pressure is raised slightly further. Reservoir pressures corresponding to a delay period of order 100 ms define an approximate self-start threshold pressure, above which the transition to explosive boiling does not occur. Within about 10 ms of initiation, the wave reaches a quasi-steady condition in which the average wave speed, two-phase flow speed, and base and exit pressures are constant. However, the instantaneous propagation rate and the mechanisms that generate the mean flow are observed to be highly nonsteady. The wavefront appears to propagate by heterogeneous bubble nucleation at its leading edge, and any given region of the wavefront tends to propagate in surges associated with new nucleation and/or very fine-scale surface perturbations. Measurements of the instantaneous position of the upstream tip of the wavefront indicate that local velocity fluctuations are the same order as the mean velocity. The leading-edge bubble lifetimes and diameters are statistically distributed; mean values are of order 1 ms and 1 mm, respectively. The leading-edge bubbles are fragmented in violent "bursts" of aerosol. Bursts have a tendency to sweep over the leading-edge bubble layer in a wavelike manner: They are "large-scale structures" associated with the fragmentation of many bubbles.Fragmentation, rapid evaporation, flow acceleration, and pressure drop occur primarily within about 1 cm of the leading edge. Downstream of this region, the average speed and appearance of the flow are virtually constant. This developed flow is a highly nonuniform, two-phase spray containing streaklike structures. Its liquid phase is composed of drops (with a maximum diameter of about 100 [...]), as well as clusters and chains of bubbles (with a diameter of a few hundred microns). A thin liquid layer begins climbing the wall upon wave initiation. Its speed is a few m/s-significantly slower than that of the two-phase flow through the center. Exit pressure measurements indicate that the flow chokes for sufficiently low reservoir pressure; at higher reservoir pressures the flow is unchoked.The self-start threshold is not a propagation threshold, as waves are observed to propagate at somewhat lower superheats if started artificially. This is accomplished in Refrigerant 114 by "jump-starting" the wave, using the more volatile Refrigerant 12. For sufficiently high reservoir pressures, an "absolute" threshold is reached at which the quasi-steady rapid evaporation processes break down.Possible mechanisms for explosive boiling are discussed in light of the present results. While neither of the two previous schools of thought (interfacial instability hypotheses and the secondary nucleation hypothesis) are alone adequate to explain the observed behavior, there is evidence that both may play a role. It is here proposed that the bursting phenomenon and bubble nucleation at the wavefront leading edge are mutually interactive processes-bursting occurring as the violent breakup of interstitial bubble liquid, and nucleation (and fine-scale perturbations) being caused by burst-generated aerosol striking the leading-edge surface. It is not understood what role interfacial instability may play in the bursting process.An evaporation wave is analogous to a premixed flame in that both are classified as "weak deflagration" waves in gasdynamic theory. It is shown that using several approximations that are valid for the type of evaporation waves studied, the conservation equations (jump conditions) can be reduced to a single, simple expression in terms of readily measured and inferred properties.

Effect of Ambient Air Pollution on Hospitalization for Heart Failure in 26 of China's Largest Cities.

PubMed

Liu, Hui; Tian, Yaohua; Song, Jing; Cao, Yaying; Xiang, Xiao; Huang, Chao; Li, Man; Hu, Yonghua

2018-03-01

There is growing interest in the association between ambient air pollution and congestive heart failure (CHF), but research data from developing countries are very limited. The primary aim of this study was to examine the association between short-term exposure to air pollution and hospital admission for CHF in China. A time-stratified case-crossover study was conducted between 2014 and 2015 in 26 large Chinese cities among 105,501 CHF hospitalizations. Conditional logistic regression models were applied to estimate the percentage changes in CHF admissions in relation to per interquartile range increases in air pollutant concentrations. Air pollution was positively associated with CHF hospitalizations. An interquartile range increase in fine particulate, particulate matter less than 10 µm in aerodynamic diameter, sulfur dioxide, nitrogen dioxide, carbon monoxide, and ozone concentrations on the current day corresponded to 1.2% (95% confidence interval [CI] 0.5%, 1.8%), 1.3% (95% CI 0.5%, 2.0%), 1.0% (95% CI 0.2%, 1.7%), 1.6% (95% CI 0.6%, 2.5%), 1.2% (95% CI 0.5%, 1.9%), and 0.4% (95% CI -0.9%, 1.7%) increases in CHF admissions, respectively. In conclusion, our findings contribute to the limited scientific literature concerning the effects of air pollution on CHF risk for high-exposure settings typical in developing countries, which may have significant public health implications for prevention of CHF in China. Copyright © 2017 Elsevier Inc. All rights reserved.

Nutritional and Anti-Inflammatory Interventions in Chronic Heart Failure

PubMed Central

Kalantar-Zadeh, Kamyar; Anker, Stefan D; Horwich, Tamara B; Fonarow, Gregg C

2017-01-01

Summary Five million individuals with chronic heart failure (CHF) in the United States have poor clinical outcomes including high death rates. Observational studies have indicated a reverse epidemiology of traditional cardiovascular risk factors in CHF; in contrast to trends seen in the general population, obesity and hypercholesterolemia are associated with improved survival. The temporal discordance between the overnutrition (long-term killer) and undernutrition (short-term killer) not only can explain some of the observed paradoxes but also may indicate a role for malnutrition, inflammation and oxidative stress that result in cachexia contributing to poor survival in CHF. Diminished appetite or anorexia may be both a cause and a consequence of this so-called malnutrition-inflammation-cachexia (MIC) or wasting syndrome in CHF. Neurohumoral activation, insulin resistance, cytokine activation and survival selection resultant genetic polymorphisms may also contribute to the prominent inflammatory and oxidative characteristics of this population. In CHF patients with wasting, nutritional strategies may be a promising therapeutic approach in CHF, especially if the provision of additional protein and energy also includes nutrients with anti-inflammatory and anti-oxidant properties. Regardless of the etiology of anorexia, appetite stimulating agents especially with anti-inflammatory properties such as megesterol acetate or pentoxyphylline may be appropriate adjuncts to dietary supplementation. Understanding the factors that modulate the MIC and wasting and their associations with clinical outcomes in CHF may lead to the development of nutritional strategies that alter the pathophysiology of CHF and improve outcomes PMID:18514634

Aldosterone synthase inhibition improves cardiovascular function and structure in rats with heart failure: a comparison with spironolactone.

PubMed

Mulder, Paul; Mellin, Virginie; Favre, Julie; Vercauteren, Magali; Remy-Jouet, Isabelle; Monteil, Christelle; Richard, Vincent; Renet, Sylvanie; Henry, Jean Paul; Jeng, Arco Y; Webb, Randy L; Thuillez, Christian

2008-09-01

Inhibition of aldosterone synthase, the key enzyme in aldosterone formation, could be an alternative strategy for mineralocorticoid-receptor antagonists in congestive heart failure (CHF), but its effect in CHF is unknown. We compared, in rats with CHF, the effects of a 7 day and a 12 week treatment with the aldosterone synthase inhibitor FAD286 (4 mg kg(-1) day(-1)) with those induced by spironolactone (80 mg kg(-1) day(-1)). FAD286/spironolactone increased cardiac output without modifying arterial pressure. Long-term FAD286 and spironolactone reduced left ventricular (LV) end-diastolic pressure, LV relaxation constant, and LV dilatation, and these effects were more marked with FAD286, whereas both drugs reduced LV hypertrophy and collagen accumulation to the same extent. Long-term FAD286/spironolactone prevented CHF-related enhancement in LV ACE and reduction in LV ACE-2, but only FAD286 prevented the reduction in LV AT(2) receptors. FAD286, but not long-term spironolactone, reduced the CHF-related enhancements in LV reactive oxygen species, reduced-oxidized glutathione ratio, and aortic nicotinamide adenine dinucleotide phosphate oxidase activity. FAD286 normalized the CHF-induced impairment of endothelium-dependent vasodilatation. In experimental CHF, FAD286 and spironolactone improve LV haemodynamics, remodelling, and function, but only FAD286 persistently normalizes LV 'redox status'. These results suggest that aldosterone synthase inhibition is a potential therapeutic strategy for the treatment of CHF.

Multiphase flow and phase change in microgravity: Fundamental research and strategic research for exploration of space

NASA Technical Reports Server (NTRS)

Singh, Bhim S.

2003-01-01

NASA is preparing to undertake science-driven exploration missions. The NASA Exploration Team's vision is a cascade of stepping stones. The stepping-stone will build the technical capabilities needed for each step with multi-use technologies and capabilities. An Agency-wide technology investment and development program is necessary to implement the vision. The NASA Exploration Team has identified a number of areas where significant advances are needed to overcome all engineering and medical barriers to the expansion of human space exploration beyond low-Earth orbit. Closed-loop life support systems and advanced propulsion and power technologies are among the areas requiring significant advances from the current state-of-the-art. Studies conducted by the National Academy of Science's National Research Council and Workshops organized by NASA have shown that multiphase flow and phase change play a crucial role in many of these advanced technology concepts. Lack of understanding of multiphase flow, phase change, and interfacial phenomena in the microgravity environment has been a major hurdle. An understanding of multiphase flow and phase change in microgravity is, therefore, critical to advancing many technologies needed. Recognizing this, the Office of Biological and Physical Research (OBPR) has initiated a strategic research thrust to augment the ongoing fundamental research in fluid physics and transport phenomena discipline with research especially aimed at understanding key multiphase flow related issues in propulsion, power, thermal control, and closed-loop advanced life support systems. A plan for integrated theoretical and experimental research that has the highest probability of providing data, predictive tools, and models needed by the systems developers to incorporate highly promising multiphase-based technologies is currently in preparation. This plan is being developed with inputs from scientific community, NASA mission planners and industry personnel. The fundamental research in multiphase flow and phase change in microgravity is aimed at developing better mechanistic understanding of pool boiling and ascertaining the effects of gravity on heat transfer and the critical heat flux. Space flight experiments conducted in space have shown that nucleate pool boiling can be sustained under certain conditions in the microgravity environment. New space flight experiments are being developed to provide more quantitative information on pool boiling in microgravity. Ground-based investigations are also being conducted to develop mechanistic models for flow and pool boiling. An overview of the research plan and roadmap for the strategic research in multiphase flow and phase change as well as research findings from the ongoing program will be presented.

Flow boiling with enhancement devices for cold plate coolant channel design

NASA Technical Reports Server (NTRS)

Boyd, Ronald D.; Turknett, Jerry C.; Smith, Alvin

1989-01-01

The effects of enhancement devices on flow boiling heat transfer in circular coolant channels, which are heated over a fraction of their perimeters, are studied. The variations were examined in both the mean and local (axial, and circumferential) heat transfer coefficients for a circular coolant channel with either smooth walls or with both a twisted tape and spiral finned walls. Improvements were initiated in the present data reduction analysis. These efforts should lead to the development of heat transfer correlations which include effects of single side heat flux and enhancement device configuration. It is hoped that a stage will be set for the study of heat transfer and pressure drop in single sided heated systems under zero gravity conditions.

Plasma and serum serotonin concentrations and surface-bound platelet serotonin expression in Cavalier King Charles Spaniels with myxomatous mitral valve disease.

PubMed

Cremer, Signe E; Kristensen, Annemarie T; Reimann, Maria J; Eriksen, Nynne B; Petersen, Stine F; Marschner, Clara B; Tarnow, Inge; Oyama, Mark A; Olsen, Lisbeth H

2015-06-01

To investigate serum and plasma serotonin concentrations, percentage of serotonin-positive platelets, level of surface-bound platelet serotonin expression (mean fluorescence intensity [MFI]), and platelet activation (CD62 expression) in platelet-rich plasma from Cavalier King Charles Spaniels with myxomatous mitral valve disease (MMVD). Healthy dogs (n = 15) and dogs with mild MMVD (18), moderate-severe MMVD (19), or severe MMVD with congestive heart failure (CHF; 10). Blood samples were collected from each dog. Serum and plasma serotonin concentrations were measured with an ELISA, and surface-bound platelet serotonin expression and platelet activation were determined by flow cytometry. Dogs with mild MMVD had higher median serum (746 ng/mL) and plasma (33.3 ng/mL) serotonin concentrations, compared with MMVD-affected dogs with CHF (388 ng/mL and 9.9 ng/mL, respectively), but no other group differences were found. Among disease groups, no differences in surface-bound serotonin expression or platelet activation were found. Thrombocytopenic dogs had lower serum serotonin concentration (482 ng/mL) than nonthrombocytopenic dogs (731 ng/mL). In 26 dogs, a flow cytometry scatterplot subpopulation (FSSP) of platelets was identified; dogs with an FSSP had a higher percentage of serotonin-positive platelets (11.0%), higher level of surface-bound serotonin expression (MFI, 32,068), and higher platelet activation (MFI, 2,363) than did dogs without an FSSP (5.7%, 1,230, and 1,165, respectively). An FSSP was present in 93.8% of thrombocytopenic dogs and in 29.5% of nonthrombocytopenic dogs. A substantive influence of circulating serotonin on MMVD stages prior to CHF development in Cavalier King Charles Spaniels was not supported by the study findings. An FSSP of highly activated platelets with pronounced serotonin binding was strongly associated with thrombocytopenia but not MMVD.

Generation and evolution of hydrothermal fluids at Yellowstone: Insights from the Heart Lake Geyser Basin

NASA Astrophysics Data System (ADS)

Lowenstern, J. B.; Bergfeld, D.; Evans, W. C.; Hurwitz, S.

2012-01-01

We sampled fumaroles and hot springs from the Heart Lake Geyser Basin (HLGB), measured water and gas discharge, and estimated heat and mass flux from this geothermal area in 2009. The combined data set reveals that diverse fluids share an origin by mixing of deep solute-rich parent water with dilute heated meteoric water, accompanied by subsequent boiling. A variety of chemical and isotopic geothermometers are consistent with a parent water that equilibrates with rocks at 205°C ± 10°C and then undergoes 21% ± 2% adiabatic boiling. Measured diffuse CO2 flux and fumarole compositions are consistent with an initial dissolved CO2 concentration of 21 ± 7 mmol upon arrival at the caldera boundary and prior to southeast flow, boiling, and discharge along the Witch Creek drainage. The calculated advective flow from the basin is 78 ± 16 L s-1of parent thermal water, corresponding to 68 ± 14 MW, or ˜1% of the estimated thermal flux from Yellowstone. Helium and carbon isotopes reveal minor addition of locally derived crustal, biogenic, and meteoric gases as this fluid boils and degasses, reducing the He isotope ratio (Rc/Ra) from 2.91 to 1.09. The HLGB is one of the few thermal areas at Yellowstone that approaches a closed system, where a series of progressively boiled waters can be sampled along with related steam and noncondensable gas. At other Yellowstone locations, steam and gas are found without associated neutral Cl waters (e.g., Hot Spring Basin) or Cl-rich waters emerge without significant associated steam and gas (Upper Geyser Basin).

Generation and evolution of hydrothermal fluids at Yellowstone: Insights from the Heart Lake Geyser Basin

USGS Publications Warehouse

Lowenstern, J. B.; Bergfeld, D.; Evans, William C.; Hurwitz, S.

2012-01-01

We sampled fumaroles and hot springs from the Heart Lake Geyser Basin (HLGB), measured water and gas discharge, and estimated heat and mass flux from this geothermal area in 2009. The combined data set reveals that diverse fluids share an origin by mixing of deep solute-rich parent water with dilute heated meteoric water, accompanied by subsequent boiling. A variety of chemical and isotopic geothermometers are consistent with a parent water that equilibrates with rocks at 205°C ± 10°C and then undergoes 21% ± 2% adiabatic boiling. Measured diffuse CO2 flux and fumarole compositions are consistent with an initial dissolved CO2 concentration of 21 ± 7 mmol upon arrival at the caldera boundary and prior to southeast flow, boiling, and discharge along the Witch Creek drainage. The calculated advective flow from the basin is 78 ± 16 L s−1 of parent thermal water, corresponding to 68 ± 14 MW, or –1% of the estimated thermal flux from Yellowstone. Helium and carbon isotopes reveal minor addition of locally derived crustal, biogenic, and meteoric gases as this fluid boils and degasses, reducing the He isotope ratio (Rc/Ra) from 2.91 to 1.09. The HLGB is one of the few thermal areas at Yellowstone that approaches a closed system, where a series of progressively boiled waters can be sampled along with related steam and noncondensable gas. At other Yellowstone locations, steam and gas are found without associated neutral Cl waters (e.g., Hot Spring Basin) or Cl-rich waters emerge without significant associated steam and gas (Upper Geyser Basin).

Application of Jacobian-free Newton–Krylov method in implicitly solving two-fluid six-equation two-phase flow problems: Implementation, validation and benchmark

DOE PAGES

Zou, Ling; Zhao, Haihua; Zhang, Hongbin

2016-03-09

This work represents a first-of-its-kind successful application to employ advanced numerical methods in solving realistic two-phase flow problems with two-fluid six-equation two-phase flow model. These advanced numerical methods include high-resolution spatial discretization scheme with staggered grids (high-order) fully implicit time integration schemes, and Jacobian-free Newton–Krylov (JFNK) method as the nonlinear solver. The computer code developed in this work has been extensively validated with existing experimental flow boiling data in vertical pipes and rod bundles, which cover wide ranges of experimental conditions, such as pressure, inlet mass flux, wall heat flux and exit void fraction. Additional code-to-code benchmark with the RELAP5-3Dmore » code further verifies the correct code implementation. The combined methods employed in this work exhibit strong robustness in solving two-phase flow problems even when phase appearance (boiling) and realistic discrete flow regimes are considered. Transitional flow regimes used in existing system analysis codes, normally introduced to overcome numerical difficulty, were completely removed in this work. As a result, this in turn provides the possibility to utilize more sophisticated flow regime maps in the future to further improve simulation accuracy.« less

Can home care for homebound patients with chronic heart failure reduce hospitalizations and costs?

PubMed Central

Punchik, Boris; Komarov, Roman; Gavrikov, Dmitry; Semenov, Anna; Freud, Tamar; Kagan, Ella; Goldberg, Yury

2017-01-01

Background Congestive heart failure (CHF), a common problem in adults, is associated with multiple hospitalizations, high mortality rates and high costs. Purpose To evaluate whether home care for homebound patients with CHF reduces healthcare service utilization and overall costs. Methods A retrospective study of healthcare utilization among homebound patients who received home care for CHF from 2012–1015. The outcome measures were number of hospital admissions per month, total number of hospitalization days and days for CHF only, emergency room visits, and overall costs. A comparison was conducted between the 6-month period prior to entry into home care and the time in home care. Results Over the study period 196 patients were treated by home care for CHF with a mean age of 79.4±9.5 years. 113 (57.7%) were women. Compared to the six months prior to home care, there were statistically significant decreases in hospitalizations (46.3%), in the number of total in-hospital days (28.7%), in the number of in-hospital days for CHF (66.7%), in emergency room visits (47%), and in overall costs (23.9%). Conclusion Home care for homebound adults with CHF can reduce healthcare utilization and healthcare costs. PMID:28753675

Quality of Low Fat Chicken Nuggets: Effect of Sodium Chloride Replacement and Added Chickpea (Cicer arietinum L.) Hull Flour

PubMed Central

Verma, Arun K.; Banerjee, Rituparna; Sharma, B. D.

2012-01-01

While attempting to develop low salt, low fat and high fibre chicken nuggets, the effect of partial (40%) common salt substitution and incorporation of chickpea hull flour (CHF) at three different levels viz., 5, 7.5 and 10% (Treatments) in pre-standardized low fat chicken nuggets (Control) were observed. Common salt replacement with salt substitute blend led to a significant decrease in pH, emulsion stability, moisture, ash, hardness, cohesiveness, gumminess and chewiness values while incorporation of CHF in low salt, low fat products resulted in decreased emulsion stability, cooking yield, moisture, protein, ash, color values, however dietary fibre and textural properties were increased (p<0.01). Lipid profile revealed a decrease in total cholesterol and glycolipid contents with the incorporation of CHF (p<0.01). All the sensory attributes except appearance and flavor, remained unaffected with salt replacement, while addition of CHF resulted in lower sensory scores (p<0.01). Among low salt, low fat chicken nuggets with CHF, incorporation CHF at 5% level was found optimum having sensory ratings close to very good. Thus most acceptable low salt, low fat and high fibre chicken nuggets could be developed by a salt replacement blend and addition of 5% CHF. PMID:25049565

Mass Spectrometric and Langmuir Probe Measurements in Inductively Coupled Plasmas in Ar, CHF3/Ar and CHF3/Ar/O2 Mixtures

NASA Technical Reports Server (NTRS)

Kim, J. S.; Rao, M. V. V. S.; Cappelli, M. A.; Sharma, S. P.; Meyyappan, M.; Arnold, Jim (Technical Monitor)

2000-01-01

Absolute fluxes and energy distributions of ions in inductively coupled plasmas of Ar, CHF3/Ar, and CHF3/Ar/O2 have been measured. These plasmas were generated in a Gaseous Electronics Conference (GEC) cell modified for inductive coupling at pressures 10-50 mTorr and 100-300 W of 13.56 MHz radio frequency (RF) power in various feedgas mixtures. In pure Ar plasmas, the Ar(+) flux increases linearly with pressure as well as RF-power. Total ion flux in CHF3 mixtures decreases with increase in pressure and also CHF3 concentration. Relative ion fluxes observed in the present studies are analyzed with the help of available cross sections for electron impact ionization and charge-exchange ion-molecule reactions. Measurements of plasma potential, electron and ion number densities, electron energy distribution function, and mean electron energy have also been made in the center of the plasma with a RF compensated Langmuir probe. Plasma potential values are compared with the mean ion energies determined from the measured ion energy distributions and are consistent. Electron temperature, plasma potential, and mean ion energy vary inversely with pressure, but increase with CHF3 content in the mixture.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wexler, J.P.; Davis, L.; Mancini, D.

Cardioactive drugs may effect both the central and peripheral circulatory systems. The effects on the central and peripheral circulatory systems of chronic Captorpril therapy in 7 pts with severe congestive heart failure (CHF) were evaluated simultaneously. Skeletal muscle blood flow (SMBF) determined using 133-Xe washout and a Cd/Te detector, oxygen consumption (VO/sub 2/), and radial artery and femoral vein O/sub 2/ concentration difference (A-V) were determined at rest and peak upright bicycle exercise before (BT) and after (AT) 6-12 weeks of Captopril therapy. In CI pts there was a significant increase in VO/sub 2/ and SMBF AT vs BT. Inmore » contrast, in CNC pts there was no change in VO/sub 2/ and a significant decrease in SMBF AT vs BT. In pts with severe CHF who are CI, there is an apparent fall in peripheral vascular resistance (PVR). In contrast, in CNC pts there is an increase in PVR. This study demonstrates that SMBF determines using 133-Xe is an important method for determining the effects of cardioactive drugs.« less

A Review of Boiling Heat Transfer Processes at High Heat Flux

DTIC Science & Technology

1991-04-01

Hydrogen on Burnout for Water Flowing Vertically Upward in Round Tubes at 2000 psia," WAPD - TH-318, April 1957. 100. Doroschuck, V. E. and Lantsman, F. P...34Forced-Convection Heat Transfer Burnout Studies for Water in Rectangular Channels and Round Tubes at Pressures above 500 psia," USAEC Rept. WAPD ...Volumes in Subcooled Boiling Systems, ASME Paper 58-HT-19, 1958. 264 . Core, T. C. and Sato, K., "Determination of Burnout Limits of Polyphenyl Coolants

CHIMNEY FOR BOILING WATER REACTOR

DOEpatents

Petrick, M.

1961-08-01

A boiling-water reactor is described which has vertical fuel-containing channels for forming steam from water. Risers above the channels increase the head of water radially outward, whereby water is moved upward through the channels with greater force. The risers are concentric and the radial width of the space between them is somewhat small. There is a relatively low rate of flow of water up through the radially outer fuel-containing channels, with which the space between the risers is in communication. (AE C)

Fluid Studies on the International Space Station

NASA Technical Reports Server (NTRS)

Motil, Brian J.

2016-01-01

Will discuss the recent activities on the international space station, including the adiabatic two phase flow, capillary flow and interfacial phenomena, and boiling and condensation. Will also give a historic introduction to Microgravity Studies at Glenn Research Center. Talk will be given to students and faculty at University of Louisville.

Flow Regime Identification of Horizontal Two Phase Refrigerant R-134a Flow Using Neural Networks (Postprint)

DTIC Science & Technology

2013-11-01

Flows in Microchannels ," Heat Transfer Engineering, Vol. 27, No. 9, 2006, pp. 4-19. 2Kandlikar, S. G., " Heat Transfer Mechanisms During Flow...Boiling in Microchannels ," Journal of Heat Transfer , Vol. 126, No. 1, 2004, pp. 8-16. 3Kreitzer, P. J., Byrd, L., and Willebrand, B. J., "Initial...an integral aspect of modeling two phase flows as most pressure drop and heat transfer correlations rely on a priori knowledge of the flow regime for

Crackle pitch and rate do not vary significantly during a single automated-auscultation session in patients with pneumonia, congestive heart failure, or interstitial pulmonary fibrosis.

PubMed

Vyshedskiy, Andrey; Ishikawa, Sadamu; Murphy, Raymond L H

2011-06-01

To determine the variability of crackle pitch and crackle rate during a single automated-auscultation session with a computerized 16-channel lung-sound analyzer. Forty-nine patients with pneumonia, 52 with congestive heart failure (CHF), and 18 with interstitial pulmonary fibrosis (IPF) performed breathing maneuvers in the following sequence: normal breathing, deep breathing, cough several times; deep breathing, vital-capacity maneuver, and deep breathing. From the auscultation recordings we measured the crackle pitch and crackle rate. Crackle pitch variability, expressed as a percentage of the average crackle pitch, was small in all patients and in all maneuvers: pneumonia 11%, CHF 11%, pulmonary fibrosis 7%. Crackle rate variability was also small: pneumonia 31%, CHF 32%, IPF 24%. Compared to the first deep-breathing maneuver (100%), the average crackle pitch did not significantly change following coughing (pneumonia 100%, CHF 103%, IPF 100%), the vital-capacity maneuver (pneumonia 100%, CHF 92%, IPF 104%), or during quiet breathing (pneumonia 97%, CHF 100%, IPF 104%). Similarly, the average crackle rate did not change significantly following coughing (pneumonia 105%, CHF 110%, IPF 90%) or the vital-capacity maneuver (pneumonia 102%, CHF 101%, IPF 99%). However, during normal breathing the crackle rate was significantly lower in the patients with pneumonia (74%, P < .001) and significantly higher in the patients with IPF (147%, P < .05) than it was during deep breathing. In patients with CHF the average crackle rate during normal breathing was not significantly different from that during the first deep-breathing maneuver (108%). Crackle pitch and rate were surprisingly stable in all 3 conditions. Neither crackle pitch nor crackle rate changed significantly from breath to breath or from one deep-breathing maneuver to another, even when the maneuvers were separated by cough or the vital-capacity maneuver. The observation that crackle rate is a reproducible measurement during one automated-auscultation session suggests that crackle rate can be used to follow the course of cardiopulmonary illnesses such as pneumonia, IPF, and CHF.

Morning surge of ventricular arrhythmias in a new arrhythmogenic canine model of chronic heart failure is associated with attenuation of time-of-day dependence of heart rate and autonomic adaptation, and reduced cardiac chaos.

PubMed

Zhu, Yujie; Hanafy, Mohamed A; Killingsworth, Cheryl R; Walcott, Gregory P; Young, Martin E; Pogwizd, Steven M

2014-01-01

Patients with chronic heart failure (CHF) exhibit a morning surge in ventricular arrhythmias, but the underlying cause remains unknown. The aim of this study was to determine if heart rate dynamics, autonomic input (assessed by heart rate variability (HRV)) and nonlinear dynamics as well as their abnormal time-of-day-dependent oscillations in a newly developed arrhythmogenic canine heart failure model are associated with a morning surge in ventricular arrhythmias. CHF was induced in dogs by aortic insufficiency & aortic constriction, and assessed by echocardiography. Holter monitoring was performed to study time-of-day-dependent variation in ventricular arrhythmias (PVCs, VT), traditional HRV measures, and nonlinear dynamics (including detrended fluctuations analysis α1 and α2 (DFAα1 & DFAα2), correlation dimension (CD), and Shannon entropy (SE)) at baseline, as well as 240 days (240 d) and 720 days (720 d) following CHF induction. LV fractional shortening was decreased at both 240 d and 720 d. Both PVCs and VT increased with CHF duration and showed a morning rise (2.5-fold & 1.8-fold increase at 6 AM-noon vs midnight-6 AM) during CHF. The morning rise in HR at baseline was significantly attenuated by 52% with development of CHF (at both 240 d & 720 d). Morning rise in the ratio of low frequency to high frequency (LF/HF) HRV at baseline was markedly attenuated with CHF. DFAα1, DFAα2, CD and SE all decreased with CHF by 31, 17, 34 and 7%, respectively. Time-of-day-dependent variations in LF/HF, CD, DFA α1 and SE, observed at baseline, were lost during CHF. Thus in this new arrhythmogenic canine CHF model, attenuated morning HR rise, blunted autonomic oscillation, decreased cardiac chaos and complexity of heart rate, as well as aberrant time-of-day-dependent variations in many of these parameters were associated with a morning surge of ventricular arrhythmias.

Morning Surge of Ventricular Arrhythmias in a New Arrhythmogenic Canine Model of Chronic Heart Failure Is Associated with Attenuation of Time-Of-Day Dependence of Heart Rate and Autonomic Adaptation, and Reduced Cardiac Chaos

PubMed Central

Zhu, Yujie; Hanafy, Mohamed A.; Killingsworth, Cheryl R.; Walcott, Gregory P.; Young, Martin E.; Pogwizd, Steven M.

2014-01-01

Patients with chronic heart failure (CHF) exhibit a morning surge in ventricular arrhythmias, but the underlying cause remains unknown. The aim of this study was to determine if heart rate dynamics, autonomic input (assessed by heart rate variability (HRV)) and nonlinear dynamics as well as their abnormal time-of-day-dependent oscillations in a newly developed arrhythmogenic canine heart failure model are associated with a morning surge in ventricular arrhythmias. CHF was induced in dogs by aortic insufficiency & aortic constriction, and assessed by echocardiography. Holter monitoring was performed to study time-of-day-dependent variation in ventricular arrhythmias (PVCs, VT), traditional HRV measures, and nonlinear dynamics (including detrended fluctuations analysis α1 and α2 (DFAα1 & DFAα2), correlation dimension (CD), and Shannon entropy (SE)) at baseline, as well as 240 days (240d) and 720 days (720d) following CHF induction. LV fractional shortening was decreased at both 240d and 720d. Both PVCs and VT increased with CHF duration and showed a morning rise (2.5-fold & 1.8-fold increase at 6 AM-noon vs midnight-6 AM) during CHF. The morning rise in HR at baseline was significantly attenuated by 52% with development of CHF (at both 240d & 720d). Morning rise in the ratio of low frequency to high frequency (LF/HF) HRV at baseline was markedly attenuated with CHF. DFAα1, DFAα2, CD and SE all decreased with CHF by 31, 17, 34 and 7%, respectively. Time-of-day-dependent variations in LF/HF, CD, DFA α1 and SE, observed at baseline, were lost during CHF. Thus in this new arrhythmogenic canine CHF model, attenuated morning HR rise, blunted autonomic oscillation, decreased cardiac chaos and complexity of heart rate, as well as aberrant time-of-day-dependent variations in many of these parameters were associated with a morning surge of ventricular arrhythmias. PMID:25140699

Laparoscopy is safe among patients with congestive heart failure undergoing general surgery procedures.

PubMed

Speicher, Paul J; Ganapathi, Asvin M; Englum, Brian R; Vaslef, Steven N

2014-08-01

Over the past 2 decades, laparoscopy has been established as a superior technique in many general surgery procedures. Few studies, however, have examined the impact of the use of a laparoscopic approach in patients with symptomatic congestive heart failure (CHF). Because pneumoperitoneum has known effects on cardiopulmonary physiology, patients with CHF may be at increased risk. This study examines current trends in approaches to patients with CHF and effects on perioperative outcomes. The 2005-2011 National Surgical Quality Improvement Program Participant User File was used to identify patients who underwent the following general surgery procedures: Appendectomy, segmental colectomy, small bowel resection, ventral hernia repair, and splenectomy. Included for analysis were those with newly diagnosed CHF or chronic CHF with new signs or symptoms. Trends of use of laparoscopy were assessed across procedure types. The primary endpoint was 30-day mortality. The independent effect of laparoscopy in CHF was estimated with a multiple logistic regression model. A total of 265,198 patients were included for analysis, of whom 2,219 were identified as having new or recently worsened CHF. Of these patients, there were 1,300 (58.6%) colectomies, 486 (21.9%) small bowel resections, 216 (9.7%) ventral hernia repairs, 141 (6.4%) appendectomies, and 76 (3.4%) splenectomies. Laparoscopy was used less frequently in patients with CHF compared with their non-CHF counterparts, particularly for nonelective procedures. Baseline characteristics were similar for laparoscopy versus open procedures with the notable exception of urgent/emergent case status (36.4% vs 71.3%; P < .001). After multivariable adjustment, laparoscopy seemed to have a protective effect against mortality (adjusted odds ratio, 0.45; P = .04), but no differences in other secondary endpoints. For patients with CHF, an open operative approach seems to be utilized more frequently in general surgery procedures, particularly in urgent/emergent cases. Despite these patterns and apparent preferences, laparoscopy seems to offer a safe alternative in appropriately selected patients. Because morbidity and mortality were considerable regardless of approach, further understanding of appropriate management in this population is necessary. Copyright © 2014 Mosby, Inc. All rights reserved.

Laparoscopy is safe among patients with congestive heart failure undergoing general surgery procedures

PubMed Central

Speicher, Paul J.; Ganapathi, Asvin M.; Englum, Brian R.; Vaslef, Steven N.

2015-01-01

Background Over the past 2 decades, laparoscopy has been established as a superior technique in many general surgery procedures. Few studies, however, have examined the impact of the use of a laparoscopic approach in patients with symptomatic congestive heart failure (CHF). Because pneumoperitoneum has known effects on cardiopulmonary physiology, patients with CHF may be at increased risk. This study examines current trends in approaches to patients with CHF and effects on perioperative outcomes. Methods The 2005–2011 National Surgical Quality Improvement Program Participant User File was used to identify patients who underwent the following general surgery procedures: Appendectomy, segmental colectomy, small bowel resection, ventral hernia repair, and splenectomy. Included for analysis were those with newly diagnosed CHF or chronic CHF with new signs or symptoms. Trends of use of laparoscopy were assessed across procedure types. The primary endpoint was 30-day mortality. The independent effect of laparoscopy in CHF was estimated with a multiple logistic regression model. Results A total of 265,198 patients were included for analysis, of whom 2,219 were identified as having new or recently worsened CHF. Of these patients, there were 1,300 (58.6%) colectomies, 486 (21.9%) small bowel resections, 216 (9.7%) ventral hernia repairs, 141 (6.4%) appendectomies, and 76 (3.4%) splenectomies. Laparoscopy was used less frequently in patients with CHF compared with their non-CHF counterparts, particularly for nonelective procedures. Baseline characteristics were similar for laparoscopy versus open procedures with the notable exception of urgent/emergent case status (36.4% vs 71.3%; P < .001). After multivariable adjustment, laparoscopy seemed to have a protective effect against mortality (adjusted odds ratio, 0.45; P = .04), but no differences in other secondary endpoints. Conclusion For patients with CHF, an open operative approach seems to be utilized more frequently in general surgery procedures, particularly in urgent/emergent cases. Despite these patterns and apparent preferences, laparoscopy seems to offer a safe alternative in appropriately selected patients. Because morbidity and mortality were considerable regardless of approach, further understanding of appropriate management in this population is necessary. PMID:24947641

Nutritional status of outpatients with chronic stable heart failure based on serum amino acid concentration.

PubMed

Tsuji, Shuhei; Koyama, Satoshi; Taniguchi, Ryoji; Fujiwara, Takako; Fujiwara, Hisayoshi; Sato, Yukihito

2018-06-06

Loss of skeletal muscle mass and low nutritional status are major complications of severe chronic heart failure (CHF) and have been associated with poor prognosis. This study aimed to identify the nutritional status of outpatients with CHF based on their body composition, such as skeletal muscle index (SMI) and serum amino acid concentration. We compared the body composition data and results of blood samples, including the serum amino acid concentration, of patients with CHF and those of controls. No significant difference was found in total amino acid concentration between 105 patients with CHF (62% men, mean age: 71.0±11.0 years) and 106 controls (67% men, mean age: 69.1±9.4 years) (CHF: 3459.1±504.9nmol/ml, control: 3575.8±513.1nmol/ml; p=0.072). However, the concentration of essential amino acids (EAA) (CHF: 949.5±197.9nmol/ml, control: 1034.1±207.3nmol/ml; p=0.002) and branched-chain amino acid (BCAA) (CHF: 449.3±114.3nmol/ml, control: 503.9±118.2nmol/ml; p<0.001) and Fischer's ratio (CHF: 2.86±0.62, control: 3.17±0.50; p<0.001) were significantly lower in patients with CHF. Integrated analysis of these data revealed that SMI was negatively correlated with age [correlation coefficient (R), -0.313; 95% confidence interval (CI), -0.514 to -0.079; p=0.010], but positively correlated with EAA concentration (R, 0.256; 95% CI, 0.017-0.467; p=0.037), BCAA concentration (R, 0.362; 95% CI, 0.134-0.554; p=0.003), and Fischer's ratio (R, 0.573; 95% CI, 0.386-0.715; p<0.001). Serum concentrations of EAA and BCAA and Fischer's ratio were lower in patients with CHF than in controls, while SMI correlated with EAA, BCAA, and Fischer's ratio. Copyright © 2018 Japanese College of Cardiology. Published by Elsevier Ltd. All rights reserved.

Evaluation of CFD Methods for Simulation of Two-Phase Boiling Flow Phenomena in a Helical Coil Steam Generator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pointer, William David; Shaver, Dillon; Liu, Yang

The U.S. Department of Energy, Office of Nuclear Energy charges participants in the Nuclear Energy Advanced Modeling and Simulation (NEAMS) program with the development of advanced modeling and simulation capabilities that can be used to address design, performance and safety challenges in the development and deployment of advanced reactor technology. The NEAMS has established a high impact problem (HIP) team to demonstrate the applicability of these tools to identification and mitigation of sources of steam generator flow induced vibration (SGFIV). The SGFIV HIP team is working to evaluate vibration sources in an advanced helical coil steam generator using computational fluidmore » dynamics (CFD) simulations of the turbulent primary coolant flow over the outside of the tubes and CFD simulations of the turbulent multiphase boiling secondary coolant flow inside the tubes integrated with high resolution finite element method assessments of the tubes and their associated structural supports. This report summarizes the demonstration of a methodology for the multiphase boiling flow analysis inside the helical coil steam generator tube. A helical coil steam generator configuration has been defined based on the experiments completed by Polytecnico di Milano in the SIET helical coil steam generator tube facility. Simulations of the defined problem have been completed using the Eulerian-Eulerian multi-fluid modeling capabilities of the commercial CFD code STAR-CCM+. Simulations suggest that the two phases will quickly stratify in the slightly inclined pipe of the helical coil steam generator. These results have been successfully benchmarked against both empirical correlations for pressure drop and simulations using an alternate CFD methodology, the dispersed phase mixture modeling capabilities of the open source CFD code Nek5000.« less

Diagnostic value of pleural fluid N-terminal pro-brain natriuretic peptide levels in patients with cardiovascular diseases.

PubMed

Liao, Huai; Na, Moon Jun; Dikensoy, Oner; Lane, Kirk B; Randal, Barnette; Light, Richard W

2008-01-01

The diagnosis of the cause of pleural effusions caused by cardiovascular diseases such as congestive heart failure (CHF) and acute pulmonary embolism is sometimes difficult. The purpose of the present study was to evaluate the utility of pleural fluid levels of N-terminal pro-brain natriuretic peptide (NT-proBNP) in differentiating pleural effusions due to CHF, pulmonary embolism and post-coronary artery bypass graft (CABG) surgery. The levels of pleural fluid NT-proBNP were measured by ELISA in a total of 40 patients: 10 with CHF, 10 with pulmonary embolism, 10 post-CABG and 10 with carcinoma. The median level of NT-proBNP in the pleural fluid of patients with CHF was 5390 pg/mL (25th to 75th percentiles, 4566 to 8158 pg/mL), which was significantly higher than that in patients with post-CABG effusions (424 pg/mL, 352 to 873), with pulmonary embolism (311 pg/mL, 212 to 1159), or with carcinoma (302 pg/mL, 208 to 626) (P < 0.001, CHF group vs all other groups). In receiver-operating curve analysis, an NT-proBNP level of >or=2220 pg/mL demonstrated a sensitivity of 100% and a specificity of 96.7% for the identification of CHF. Measurement of the NT-proBNP level in pleural fluid is accurate in diagnosing the etiology of the effusion as CHF. Pleural fluid levels above 2220 pg/mL are essentially diagnostic that the pleural effusion is due to CHF.

Total inpatient treatment costs in patients with severe burns: towards a more accurate reimbursement model.

PubMed

Mehra, Tarun; Koljonen, Virve; Seifert, Burkhardt; Volbracht, Jörk; Giovanoli, Pietro; Plock, Jan; Moos, Rudolf Maria

2015-01-01

Reimbursement systems have difficulties depicting the actual cost of burn treatment, leaving care providers with a significant financial burden. Our aim was to establish a simple and accurate reimbursement model compatible with prospective payment systems. A total of 370 966 electronic medical records of patients discharged in 2012 to 2013 from Swiss university hospitals were reviewed. A total of 828 cases of burns including 109 cases of severe burns were retained. Costs, revenues and earnings for severe and nonsevere burns were analysed and a linear regression model predicting total inpatient treatment costs was established. The median total costs per case for severe burns was tenfold higher than for nonsevere burns (179 949 CHF [167 353 EUR] vs 11 312 CHF [10 520 EUR], interquartile ranges 96 782-328 618 CHF vs 4 874-27 783 CHF, p <0.001). The median of earnings per case for nonsevere burns was 588 CHF (547 EUR) (interquartile range -6 720 - 5 354 CHF) whereas severe burns incurred a large financial loss to care providers, with median earnings of -33 178 CHF (30 856 EUR) (interquartile range -95 533 - 23 662 CHF). Differences were highly significant (p <0.001). Our linear regression model predicting total costs per case with length of stay (LOS) as independent variable had an adjusted R2 of 0.67 (p <0.001 for LOS). Severe burns are systematically underfunded within the Swiss reimbursement system. Flat-rate DRG-based refunds poorly reflect the actual treatment costs. In conclusion, we suggest a reimbursement model based on a per diem rate for treatment of severe burns.

Gas chemistry and thermometry of the Cerro Prieto, Mexico, geothermal field

USGS Publications Warehouse

Nehring, N.L.; D'Amore, F.

1984-01-01

Gas compositions of Cerro Prieto wells in 1977 reflected strong boiling in the reservoir around wells M-20 and M-25. This boiling zone appeared to be collapsing in 1982 when a number of wells in this area of the field were shut-in. In 1977 and 1982, gas compositions also showed boiling zones corresponding to faults H and L postulated by Halfman et al. (1982). Four gas geothermometers were applied, based on reservoir equilibria and calculated fugacities. The Fisher - Tropsch reaction predicted high temperatures and appeared to re-equilibrate slowly, whereas the H2S reaction predicted low temperatures and appeared to re-equilibrate rapidly. Hydrogen and NH3 reactions were intermediate. Like gas compositions, the geothermometers reflected reservoir processes, such as boiling. Surface gas compositions are related to well compositions, but contain large concentrations of N2 originating from air dissolved in groundwater. The groundwater appears to originate in the east and flow over the production field before mixing with reservoir gases near the surface. ?? 1984.

Increasing Healthcare Burden of Chronic Liver Disease Compared to Other Chronic Diseases, 2004-2013.

PubMed

Asrani, Sumeet K; Kouznetsova, Maria; Ogola, Gerald; Taylor, Thomas; Masica, Andrew; Pope, Brandon; Trotter, James; Kamath, Patrick; Kanwal, Fasiha

2018-05-23

Chronic liver disease (CLD) is a common and expensive condition, and studies of CLD-related hospitalizations have underestimated the true burden of disease. We analyzed data from a large diverse healthcare system to compare time trends in CLD-related hospitalizations with those of congestive heart failure (CHF) or chronic obstructive pulmonary disease (COPD). We collected data from a large healthcare system in Texas on hospitalizations related to CLD (n=27,783), CHF (n=60,415), and COPD (n=34,199) from January 1, 2004 through December 31, 2013. We calculated annual hospitalization rates (per 100,000) and compared hospital course, inpatient mortality, ancillary services and re-admissions. Compared to patients with CHF (median age, 71 years) or COPD (median age 69 years), patients with CLD were significantly younger (median age 57 years; P<.01 vs CHF and COPD). Higher proportions of patients with CLD were uninsured (11.7% vs 5.4% for CHF and 5.4% for COPD; P<.01) and Hispanic (17% for CLD vs 9.3% for CHF and 5.0% for COPD; P<.01). A lower proportion of patients with CLD had Medicare (41.5% vs 68.6% with CHF and 70.1% with COPD; P<0.01). From 2004 through 2013, the rate of CLD-related hospitalization increased by 92% (from 1295/100,000 to 2490/100,000), compared to 6.7% for CHF (from 3843/100,000 to 4103/100,000) and 48.8% for COPD (from 1775/100,000 to 2642/100,000). During this time period, CLD-related hospitalizations covered by Medicare increased from 31.8% to 41.5%, whereas hospitalizations covered by Medicare did not change for CHF (remained at 70%) or COPD (remained at 70%). Patients with CLD had longer hospital stays (7.3 days vs 6.2 days for CHF or 5.9 days for COPD; P<.01). A higher proportion of patients with CLD died or were discharged to hospice (14.2% vs 11.5% of patients with CHF and 9.3% of patients with COPD P<.01), and a smaller proportion had access to post-acute care (13.2% vs 23.2% of patients with CHF and 27.4% of patients with COPD; P<.01). A higher proportion of patients with CLD were readmitted to the hospital within 30 days (25% vs 21.9% of patients with CHF and 20.6% with COPD; P<.01). Patients with chronic liver disease, compared to selected other chronic diseases, had increasing rates of hospitalization, longer hospital stays, more readmissions, and, despite these adverse outcomes, less access to post-acute care. Disease management models for chronic liver disease are greatly needed to manage the anticipated increase in hospitalizations for CLD. Copyright © 2018 AGA Institute. Published by Elsevier Inc. All rights reserved.

Heart Failure and Exercise: A Narrative Review of the Role of Self-Efficacy.

PubMed

Ha, Francis J; Hare, David L; Cameron, James D; Toukhsati, Samia R

2018-01-01

Chronic heart failure (CHF) is a common, debilitating condition associated with significant health and economic burden. CHF management is multidisciplinary, however, achieving better health relies on a collaborative effort and patient engagement in self-care. Despite the importance of self-care in CHF, many patients have poor adherence to their medical and lifestyle regimens, in particular with regards to engaging in physical exercise. The patient's confidence in their ability, otherwise known as self-efficacy, is an important determinant of CHF health outcomes, most likely due to its effect on the uptake of CHF self-care activities especially exercise initiation and maintenance. Self-efficacy is responsive to experience such as exercise training, however the critical components of exercise interventions to improve self-efficacy have yet to be determined. This narrative review provides an overview of the role of self-efficacy in exercise adherence in CHF. Copyright © 2017 Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) and the Cardiac Society of Australia and New Zealand (CSANZ). Published by Elsevier B.V. All rights reserved.

Critical Heat Flux Phenomena at HighPressure & Low Mass Fluxes: NEUP Final Report Part I: Experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Corradini, Michael; Wu, Qiao

2015-04-30

This report is a preliminary document presenting an overview of the Critical Heat Flux (CHF) phenomenon, the High Pressure Critical Heat Flux facility (HPCHF), preliminary CHF data acquired, and the future direction of the research. The HPCHF facility has been designed and built to study CHF at high pressure and low mass flux ranges in a rod bundle prototypical of conceptual Small Modular Reactor (SMR) designs. The rod bundle is comprised of four electrically heated rods in a 2x2 square rod bundle with a prototypic chopped-cosine axial power profile and equipped with thermocouples at various axial and circumferential positions embeddedmore » in each rod for CHF detection. Experimental test parameters for CHF detection range from pressures of ~80 – 160 bar, mass fluxes of ~400 – 1500 kg/m2s, and inlet water subcooling from ~30 – 70°C. The preliminary data base established will be further extended in the future along with comparisons to existing CHF correlations, models, etc. whose application ranges may be applicable to the conditions of SMRs.« less

GPCR-autoantibodies in chronic heart failure.

PubMed

Boivin-Jahns, Valerie; Jahns, Roland

2018-06-01

Chronic heart failure (CHF) is a syndrome characterized by shortness of breath, fluid retention, and a progressive reduction in cardiac function. More than 60% of the cases are ischemic in origin (i.e., due to myo-cardial infarction) and about 30% are caused by non-ischemic myocardial damage (i.e., due to genetic or non-genetic causes like myocardial inflammation). Because of alterations in both cellular and humoral immunity patients with non-ischemic CHF often develop abnormal or misled immune responses, including cross-reacting antibodies and/or autoantibodies to various cardiac anti-gens. Non-ischemic myo-cardial damage was found to progress to CHF particularly, when associated (a) with the generation of autoantibodies directed against distinct myocyte membrane proteins critically involved in cardiac function - like G-protein coup-led membrane receptors (GPCRs), or (b) with virus persistence in the myocardium. This article will review current knowledge on the pathophysiological relevance of GPCR-autoreactivity in CHF by giving an overview on the so far available evidence from pre-clinical, clinical and epidemiological studies on the CHF-inducing potential of GPCR-autoantibodies and thereon based novel therapeutic approaches in GPCR autoantibody-associated CHF.

Self-care and depression in patients with chronic heart failure.

PubMed

Holzapfel, Nicole; Löwe, Bernd; Wild, Beate; Schellberg, Dieter; Zugck, Christian; Remppis, Andrew; Katus, Hugo A; Haass, Markus; Rauch, Bernhard; Jünger, Jana; Herzog, Wolfgang; Müller-Tasch, Thomas

2009-01-01

Although chronic heart failure (CHF) is often complicated by comorbid depression and poor self-care, little is known about their specific association in patients with CHF. To investigate self-care behavior among patients with CHF with different degrees of depression severity. A total of 287 patients with documented CHF, New York Heart Association functional class II to IV, completed the European Heart Failure Self-Care Behavior Scale. The Structured Clinical Interview for DSM (SCID) IV served as the criterion standard for the presence of a depressive disorder. Analyses of covariance and linear regression analyses revealed that patients with CHF with minor depression reported significantly lower levels of self-care than patients with major depression (P = .003) and nondepressed patients (P = .014). In addition to minor depression, age (P < or = .001), multimorbidity (P = .01), left ventricular ejection fraction (P = .001), and family status (P = .01) were determinants of self-care. Our results demonstrate that patients with CHF with minor depression and not major depression are at higher risk for poor self-care and its resulting consequences, such as symptom deterioration and frequent hospitalization.

Treating anemia in heart failure patients: a review of erythropoiesis-stimulating agents.

PubMed

Geisler, Benjamin P

2010-08-01

Prevalence of chronic heart failure (CHF) is increasing, and despite improvements in the past decade the prognosis in terms of mortality and health-related quality of life remains poor. Anemia is often found concomitantly in CHF patients. Erythropoiesis-stimulating agents (ESAs) are a new treatment option for these anemic CHF patients, promising to decrease mortality and hospitalizations, and increase health-related quality of life. CHF epidemiology is briefly discussed. Currently available clinical efficacy and safety data are critically appraised. Health care utilization by CHF patients, particularly hospitalizations, are reviewed in order predict cost-effectiveness of ESAs. The efficacy for the most pertinent endpoints has not been proven by a pivotal trial or a meta-analysis free of bias, and there might be increased cardiovascular events and cancer incidence rates above a currently unknown target value or with multiple doses. However, subgroups should be identified in which ESAs might prove to be more efficacious and as safe as usual care and either cost-saving or cost-effective. Nevertheless, depending on the subgroup, the budget effect for payors might be dramatic due to the large number of CHF patients.

Modeling and forecasting foreign exchange daily closing prices with normal inverse Gaussian

NASA Astrophysics Data System (ADS)

Teneng, Dean

2013-09-01

We fit the normal inverse Gaussian(NIG) distribution to foreign exchange closing prices using the open software package R and select best models by Käärik and Umbleja (2011) proposed strategy. We observe that daily closing prices (12/04/2008 - 07/08/2012) of CHF/JPY, AUD/JPY, GBP/JPY, NZD/USD, QAR/CHF, QAR/EUR, SAR/CHF, SAR/EUR, TND/CHF and TND/EUR are excellent fits while EGP/EUR and EUR/GBP are good fits with a Kolmogorov-Smirnov test p-value of 0.062 and 0.08 respectively. It was impossible to estimate normal inverse Gaussian parameters (by maximum likelihood; computational problem) for JPY/CHF but CHF/JPY was an excellent fit. Thus, while the stochastic properties of an exchange rate can be completely modeled with a probability distribution in one direction, it may be impossible the other way around. We also demonstrate that foreign exchange closing prices can be forecasted with the normal inverse Gaussian (NIG) Lévy process, both in cases where the daily closing prices can and cannot be modeled by NIG distribution.

Left lateral decubitus position on patients with atrial fibrillation and congestive heart failure

NASA Astrophysics Data System (ADS)

Varadan, Vijay K.; Kumar, Prashanth S.; Ramasamy, Mouli

2017-04-01

Congestive Heart Failure (CHF) is a cardiovascular disease that affects about 5.7 million people in the US. The most prevalent comorbidity to CHF is Atrial Fibrillation (AF). These two pathologies present in a mutually worsening manner in that patients diagnosed with CHF are more likely to develop AF and patients who are diagnosed with AF are more likely to develop CHF. The underlying pathophysiological mechanisms have been studied for several years and the most recent efforts are in the cellular and molecular basis. In this paper, we focus on manifestation of CHF and AF symptoms as influenced by the posture assumed by a patient. We consider three postures - Left lateral decubitus, right lateral decubitus and supine. We review the clinical evidence gathered thus far relating enhanced sympathetic activity to the left lateral decubitus and supine positions with equivalent evidence on the enhanced vagal activity when the right lateral decubitus posture is assumed. We conclude with a compilation of all the hypotheses on the mechanism by which the right lateral decubitus posture alleviates the symptoms of CHF and AF, and future avenues for investigation.

Modified-Collins cryocooler for zero-boiloff storage of cryogenic fuels in space

NASA Astrophysics Data System (ADS)

Hannon, Charles L.; Krass, Brady; Hogan, Jake; Brisson, John

2012-06-01

Future lunar and planetary explorations will require the storage of cryogenic propellants, particularly liquid oxygen (LOX) and liquid hydrogen (LH2), in low earth orbit (LEO) for periods of time ranging from days to months, and possibly longer. Without careful thermal management, significant quantities of stored liquid cryogens can be lost due to boil-off. Boil-off can be minimized by a variety of passive means including insulation, sun shades and passive radiational cooling. However, it has been shown that active cooling using space cryocoolers has the potential to result in Zero Boil-Off (ZBO) and the launch-mass savings using active cooling exceeds that of passive cooling of LOX for mission durations in LEO of less than 1 week, and for LH2 after about 2 months in LEO. Large-scale DC-flow cryogenic refrigeration systems operate at a fraction of the specific power levels required by small-scale AC-flow cryocoolers. The efficiency advantage of DC-flow cryogenic cycles motivates the current development of a cryocooler based on a modification of the Collins Cycle. The modified Collins cycle design employs piston type expanders that support high operating pressure ratios, electromagnetic valves that enable "floating pistons", and recuperative heat transfer. This paper will describe the design of a prototype Modified-Collins cryocooler for ZBO storage of cryogenic fuels in space.

Evaporation of oil-water emulsion drops when heated at high temperature

NASA Astrophysics Data System (ADS)

Strizhak, P. A.; Piskunov, M. V.; Kuznetsov, G. V.; Voytkov, I. S.

2017-10-01

An experimental study on conditions and main characteristics for high-temperature (more than 700 K) evaporation of oil-water drops is presented. The high-temperature water purification from impurities can be the main practical application of research results. Thus, the heating of drops is implemented by the two typical schemes: on a massive substrate (the heating conditions are similar to those achieved in a heating chamber) and in a flow of the heated air. In the latter case, the heating conditions correspond to those attained while moving water drops with impurities in a counter high-temperature gaseous flow in the process of water purification. Evaporation time as function of heating temperature is presented. The influence of oil product concentration in an emulsion drop on evaporation characteristics is discussed. The conditions for intensive flash boiling of an emulsion drop and its explosive breakup with formation of the fine droplets cloud are pointed out. Heat fluxes required for intensive flash boiling and explosive breakup of a drop with further formation of the fine aerosol are determined in the boundary layer of a drop. The fundamental differences between flash boiling and explosive breakup of an emulsion drop when heated on a substrate and in a flow of the heated air are described. The main prospects for the development of the high-temperature water purification technology are detailed taking into account the fast emulsion drop breakup investigated in the paper.

The application of the high-speed photography in the experiments of boiling liquid expanding vapor explosions

NASA Astrophysics Data System (ADS)

Chen, Sining; Sun, Jinhua; Chen, Dongliang

2007-01-01

The liquefied-petroleum gas tank in some failure situations may release its contents, and then a series of hazards with different degrees of severity may occur. The most dangerous accident is the boiling liquid expanding vapor explosion (BLEVE). In this paper, a small-scale experiment was established to experimentally investigate the possible processes that could lead to a BLEVE. As there is some danger in using LPG in the experiments, water was used as the test fluid. The change of pressure and temperature was measured during the experiment. The ejection of the vapor and the sequent two-phase flow were recorded by a high-speed video camera. It was observed that two pressure peaks result after the pressure is released. The vapor was first ejected at a high speed; there was a sudden pressure drop which made the liquid superheated. The superheated liquid then boiled violently causing the liquid contents to swell, and also, the vapor pressure in the tank increased rapidly. The second pressure peak was possibly due to the swell of this two-phase flow which was likely to violently impact the wall of the tank with high speed. The whole evolution of the two-phase flow was recorded through photos captured by the high-speed video camera, and the "two step" BLEVE process was confirmed.

Myocardial deletion of transcription factor CHF1/Hey2 results in altered myocyte action potential and mild conduction system expansion but does not alter conduction system function or promote spontaneous arrhythmias.

PubMed

Hartman, Matthew E; Liu, Yonggang; Zhu, Wei-Zhong; Chien, Wei-Ming; Weldy, Chad S; Fishman, Glenn I; Laflamme, Michael A; Chin, Michael T

2014-07-01

CHF1/Hey2 is a Notch-responsive basic helix-loop-helix transcription factor involved in cardiac development. Common variants in Hey2 are associated with Brugada syndrome. We hypothesized that absence of CHF1/Hey2 would result in abnormal cellular electrical activity, altered cardiac conduction system (CCS) development, and increased arrhythmogenesis. We isolated neonatal CHF/Hey2-knockout (KO) cardiac myocytes and measured action potentials and ion channel subunit gene expression. We also crossed myocardial-specific CHF1/Hey2-KO mice with cardiac conduction system LacZ reporter mice and stained for conduction system tissue. We also performed ambulatory ECG monitoring for arrhythmias and heart rate variability. Neonatal cardiomyocytes from CHF1/Hey2-KO mice demonstrate a 50% reduction in action potential dV/dT, a 50-75% reduction in SCN5A, KCNJ2, and CACNA1C ion channel subunit gene expression, and an increase in delayed afterdepolarizations from 0/min to 12/min. CHF1/Hey2 cKO CCS-lacZ mice have a ∼3-fold increase in amount of CCS tissue. Ambulatory ECG monitoring showed no difference in cardiac conduction, arrhythmias, or heart rate variability. Wild-type cells or animals were used in all experiments. CHF1/Hey2 may contribute to Brugada syndrome by influencing the expression of SCN5A and formation of the cardiac conduction system, but its absence does not cause baseline conduction defects or arrhythmias in the adult mouse.-Hartman, M. E., Liu, Y., Zhu, W.-Z., Chien, W.-M., Weldy, C. S., Fishman, G. I., Laflamme, M. A., Chin, M. T. Myocardial deletion of transcription factor CHF1/Hey2 results in altered myocyte action potential and mild conduction system expansion but does not alter conduction system function or promote spontaneous arrhythmias. © FASEB.

Incidence, Prognostic Impact, and Predictive Factors of Readmission for Heart Failure After Transcatheter Aortic Valve Replacement.

PubMed

Durand, Eric; Doutriaux, Maxime; Bettinger, Nicolas; Tron, Christophe; Fauvel, Charles; Bauer, Fabrice; Dacher, Jean-Nicolas; Bouhzam, Najime; Litzler, Pierre-Yves; Cribier, Alain; Eltchaninoff, Hélène

2017-12-11

The aim of this study was to assess the incidence, prognostic impact, and predictive factors of readmission for congestive heart failure (CHF) in patients with severe aortic stenosis treated by transcatheter aortic valve replacement (TAVR). TAVR is indicated in patients with severe symptomatic aortic stenosis in whom surgery is considered high risk or is contraindicated. Readmission for CHF after TAVR remains a challenge, and data on prognostic and predictive factors are lacking. All patients who underwent TAVR from January 2010 to December 2014 were included. Follow-up was achieved for at least 1 year and included clinical and echocardiographic data. Readmission for CHF was analyzed retrospectively. This study included 546 patients, 534 (97.8%) of whom were implanted with balloon-expandable valves preferentially via the transfemoral approach in 87.8% of cases. After 1 year, 285 patients (52.2%) had been readmitted at least once, 132 (24.1%) for CHF. Patients readmitted for CHF had an increased risk for death (p < 0.0001) and cardiac death (p < 0.0001) compared with those not readmitted for CHF. On multivariate analysis, aortic mean gradient (hazard ratio [HR]: 0.88; 95% confidence interval [CI]: 0.79 to 0.99; p = 0.03), post-procedural blood transfusion (HR: 2.27; 95% CI: 1.13 to 5.56; p = 0.009), severe post-procedural pulmonary hypertension (HR: 1.04; 95% CI: 1.00 to 1.07; p < 0.0001), and left atrial diameter (HR: 1.47; 95% CI: 1.08 to 2.01; p = 0.02) were independently associated with CHF readmission at 1 year. Readmission for CHF after TAVR was frequent and was strongly associated with 1-year mortality. Low gradient, persistent pulmonary hypertension, left atrial dilatation, and transfusions were predictive of readmission for CHF. Copyright © 2017 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

Cautious Application of Pleural N-Terminal Pro-B-Type Natriuretic Peptide in Diagnosis of Congestive Heart Failure Pleural Effusions among Critically Ill Patients

PubMed Central

Yeh, Jiann-Horng; Huang, Chun-Ta; Liu, Chia-Hsiung; Ruan, Sheng-Yuan; Tsai, Yi-Ju; Chien, Ying-Chun; Yang, Ching-Yao; Huang, Chun-Kai; Hsu, Chia-Lin; Kuo, Lu-Cheng; Lee, Pei-Lin; Ku, Shih-Chi; Kuo, Ping-Hung; Yu, Chong-Jen

2014-01-01

Background and Objective Several studies on diagnostic accuracy of pleural N-terminal pro-B-type natriuretic peptide (NT-pro-BNP) for effusions from congestive heart failure (CHF) conclude that pleural NT-pro-BNP is a useful biomarker with high diagnostic accuracy for distinguishing CHF effusions. However, its applicability in critical care settings remains uncertain and requires further investigations. Methods NT-proBNP was measured in pleural fluid samples of a prospective cohort of intensive care unit patients with pleural effusions. Receiver operating characteristic curve analysis was performed to determine diagnostic accuracy of pleural NT-proBNP for prediction of CHF effusions. Results One hundred forty-seven critically ill patients were evaluated, 38 (26%) with CHF effusions and 109 (74%) with non-CHF effusions of various causes. Pleural NT-proBNP levels were significantly elevated in patients with CHF effusions. Pleural NT-pro-BNP demonstrated the area under the curve of 0.87 for diagnosing effusions due to CHF. With a cutoff of 2200 pg/mL, pleural NT-proBNP displayed high sensitivity (89%) but moderate specificity (73%). Notably, 29 (27%) of 109 patients with non-CHF effusions had pleural NT-proBNP levels >2200 pg/mL and these patients were more likely to experience septic shock (18/29 vs. 10/80, P<0.001) or acute kidney injury (19/29 vs. 9/80, P<0.001). Conclusions Among critically ill patients, pleural NT-proBNP measurements remain a useful diagnostic aid in evaluation of pleural effusions. However, patients with non-CHF effusions may exhibit high pleural NT-proBNP concentrations if they suffer from septic shock or acute kidney injury. Accordingly, it is suggested that clinical context should be taken into account when interpreting pleural NT-proBNP values in critical care settings. PMID:25502236

Inhibition of soluble epoxide hydrolase does not improve the course of congestive heart failure and the development of renal dysfunction in rats with volume overload induced by aorto-caval fistula

PubMed Central

Červenka, Luděk; Melenovský, Vojtěch; Husková, Zuzana; Sporková, Alexandra; Bürgelová, Marcela; Škaroupková, Petra; Hwang, Sung Hee; Hammock, Bruce D.; Imig, John D.; Sadowski, Janusz

2016-01-01

The detailed mechanisms determining the course of congestive heart failure (CHF) and associated renal dysfunction remain unclear. In a volume overload model of CHF induced by creation of aorto-caval fistula (ACF) in Hannover Sprague-Dawley (HanSD) rats we explored the putative pathogenetic contribution of epoxyeicosatrienoic acids (EETs), active products of CYP-450 dependent epoxygenase pathway of arachidonic acid metabolism, and compared it with the role of the renin-angiotensin system (RAS). Chronic treatment with cis-4-[4-(3-adamantan-1-yl-ureido) cyclohexyloxy]benzoic acid (c-AUCB, 3 mg/L in drinking water), an inhibitor of soluble epoxide hydrolase (sEH) which normally degrades EETs, increased intrarenal and myocardial EETs to levels observed in sham-operated HanSD rats, but did not improve the survival or renal function impairment. In contrast, chronic angiotensin-converting enzyme inhibition (ACEi, trandolapril, 6 mg/L in drinking water) increased renal blood flow, fractional sodium excretion and markedly improved survival, without affecting left ventricular structure and performance. Hence, renal dysfunction rather than cardiac remodeling determines long-term mortality in advanced stage of CHF due to volume overload. Strong protective actions of ACEi were associated with suppression of the vasoconstrictor/sodium retaining axis and activation of vasodilatory/natriuretic axis of the renin-angiotensin system in the circulating blood and kidney tissue. PMID:26047375

First on-sun test of NaK pool-boiler solar receiver

NASA Astrophysics Data System (ADS)

Moreno, J. B.; Andraka, C. E.; Moss, T. A.; Cordeiro, P. G.; Dudley, V. E.; Rawlinson, K. S.

During 1989-1990, a refluxing liquid-metal pool-boiler solar receiver designed for dish/Stirling application at 75 kW(sub t) throughput was successfully demonstrated at Sandia National Laboratories. Significant features of this receiver included (1) boiling sodium as the heat transfer medium, and (2) electric-discharge-machined (EDM) cavities as artificial nucleation sites to stabilize boiling. Following this first demonstration, a second-generation pool-boiler receiver that brings the concept closer to commercialization has been designed, constructed, and successfully tested. For long life, the new receiver is built from Haynes Alloy 230. For increased safety factors against film boiling and flooding, the absorber area and vapor-flow passages have been enlarged. To eliminate the need for trace heating, sodium has been replaced by the sodium-potassium alloy NaK-78. To reduce manufacturing costs, the receiver has a powdered-metal coating instead of EDM cavities for stabilization of boiling. To control incipient-boiling superheats, especially during hot restarts, it contains a small amount of xenon. In this paper, we present the receiver design and report the results of on-sun tests using a nominal 75 kW(sub t) test-bed concentrator to characterize boiling stability, hot-restart behavior, and thermal efficiency at temperatures up to 750 C. We also report briefly on late results from an advanced-concepts pool-boiler receiver.

Pancreatic exocrine insufficiency in patients with chronic heart failure and its possible association with appetite loss.

PubMed

Xia, Tingting; Chai, Xichen; Shen, Jiaqing

2017-01-01

Appetite loss is one complication of chronic heart failure (CHF), and its association with pancreatic exocrine insufficiency (PEI) is not well investigated in CHF. We attempted to detect the association between PEI and CHF-induced appetite. Patients with CHF were enrolled, and body mass index (BMI), left ventricular ejection fraction (LVEF), New York Heart Association (NYHA) cardiac function grading, B-type natriuretic peptide (BNP), serum albumin, pro-albumin and hemoglobin were evaluated. The pancreatic exocrine function was measured by fecal elastase-1 (FE-1) levels in the enrolled patients. Appetite assessment was tested by completing the simplified nutritional appetite questionnaire (SNAQ). The improvement of appetite loss by supplemented pancreatic enzymes was also researched in this study. The decrease of FE-1 levels was found in patients with CHF, as well as SNAQ scores. A positive correlation was observed between SNAQ scores and FE-1 levels (r = 0.694, p < 0.001). Pancreatic enzymes supplement could attenuate the decrease of SNAQ scores in CHF patients with FE-1 levels <200 μg/g stool and SNAQ < 14. Appetite loss is commonly seen in CHF, and is partially associated with pancreatic exocrine insufficiency. Oral pancreatic enzyme replacement therapy attenuates the chronic heart failure-induced appetite loss. These results suggest a possible pancreatic-cardiac relationship in chronic heart failure, and further experiment is needed for clarifying the possible mechanisms.

Prognostic significance of hemoglobin level in patients with congestive heart failure and normal ejection fraction.

PubMed

Varadarajan, Padmini; Gandhi, Siddharth; Sharma, Sanjay; Umakanthan, Branavan; Pai, Ramdas G

2006-10-01

Previous studies have shown low hemoglobin (Hb) to have an adverse effect on survival in patients with congestive heart failure (CHF) and reduced left ventricular (LV) ejection fraction (EF); but its effect on survival in patients with CHF and normal EF is not known. This study sought to determine whether low Hb has an effect on survival in patients with both CHF and normal EF. Detailed chart reviews were performed by medical residents on 2,246 patients (48% with normal EF) with a discharge diagnosis of CHF in a large tertiary care hospital from 1990 to 1999. The CHF diagnosis was validated using the Framingham criteria. Mortality data were obtained from the National Death Index. Survival analysis was performed using Kaplan-Meier and Cox regression models. By Kaplan-Meier analysis, low Hb (< 12 gm/dl) compared with normal hemoglobin was associated with a lower 5-year survival in patients with CHF and both normal (38 vs. 50%, p = 0.0008) and reduced (35 vs. 48%, p = 0.0009) EF. Using the Cox regression model, low Hb was an independent predictor of mortality after adjusting for age, gender, renal dysfunction, diabetes mellitus, hypertension, and EF in both groups of patients. Low Hb has an independent adverse effect on survival in patients with CHF and both normal and reduced EF in both groups of patients.

Thiazolidinediones and congestive heart failure in veterans with type 2 diabetes.

PubMed

Toprani, A; Fonseca, V

2011-03-01

The thiazolidinedione (TZD) class of antihyperglycaemic agents has been shown to improve glycaemic control by improving peripheral insulin sensitivity but may worsen or precipitate congestive heart failure (CHF). Randomized controlled trials have shown an increased risk of CHF in patients treated with TZDs. The use of TZDs in clinical practice has the potential to increase morbidity and health care costs. The purpose of this study was to compare the incidence of CHF in TZD and non-TZD-treated patients in a clinical setting. A retrospective cohort study of all male patients with type 2 diabetes seen in the South Central US Veterans Administration health care network between 1 October 1996 and 31 December 2004. We constructed a Cox proportional hazards model to evaluate the impact of TZD therapy on time to incidence of CHF. Of 3956 patients, 29% (n = 1157) developed CHF during the study period. The incidence of CHF was higher in patients who received TZD medications than in those who received TZDs. After adjustment for multiple cardiac risk factors, the hazard ratio for the development of CHF for TZD versus non-TZD-treated patients was 0.69 with a 95% confidence interval of 0.60-0.79. Patients in this cohort who received TZD medications had a lower incidence of heart failure than patients who did not receive TZDs. © 2011 Blackwell Publishing Ltd.

Automated diagnosis of congestive heart failure using dual tree complex wavelet transform and statistical features extracted from 2s of ECG signals.

PubMed

Sudarshan, Vidya K; Acharya, U Rajendra; Oh, Shu Lih; Adam, Muhammad; Tan, Jen Hong; Chua, Chua Kuang; Chua, Kok Poo; Tan, Ru San

2017-04-01

Identification of alarming features in the electrocardiogram (ECG) signal is extremely significant for the prediction of congestive heart failure (CHF). ECG signal analysis carried out using computer-aided techniques can speed up the diagnosis process and aid in the proper management of CHF patients. Therefore, in this work, dual tree complex wavelets transform (DTCWT)-based methodology is proposed for an automated identification of ECG signals exhibiting CHF from normal. In the experiment, we have performed a DTCWT on ECG segments of 2s duration up to six levels to obtain the coefficients. From these DTCWT coefficients, statistical features are extracted and ranked using Bhattacharyya, entropy, minimum redundancy maximum relevance (mRMR), receiver-operating characteristics (ROC), Wilcoxon, t-test and reliefF methods. Ranked features are subjected to k-nearest neighbor (KNN) and decision tree (DT) classifiers for automated differentiation of CHF and normal ECG signals. We have achieved 99.86% accuracy, 99.78% sensitivity and 99.94% specificity in the identification of CHF affected ECG signals using 45 features. The proposed method is able to detect CHF patients accurately using only 2s of ECG signal length and hence providing sufficient time for the clinicians to further investigate on the severity of CHF and treatments. Copyright © 2017 Elsevier Ltd. All rights reserved.

NASA Physical Sciences - Presentation to Annual Two Phase Heat Transfer International Topical Team Meeting

NASA Technical Reports Server (NTRS)

Chiaramonte, Francis; Motil, Brian; McQuillen, John

2014-01-01

The Two-phase Heat Transfer International Topical Team consists of researchers and members from various space agencies including ESA, JAXA, CSA, and RSA. This presentation included descriptions various fluid experiments either being conducted by or planned by NASA for the International Space Station in the areas of two-phase flow, flow boiling, capillary flow, and crygenic fluid storage.

Preliminary Study of a Piston Pump for Cryogenic Fluids

NASA Technical Reports Server (NTRS)

Biermann, Arnold E.; Kohl, Robert C.

1959-01-01

Preliminary data are presented covering the performance of a low-speed, five-cylinder piston pump designed for handling boiling hydrogen. This pump was designed for a flow of 55 gallons per minute at 240 rpm with a discharge pressure of 135 pounds per square inch. Tests were made using JP-4 fuel, liquid nitrogen, and liquid hydrogen. Pump delivery and endurance characteristics were satisfactory for the range of operation covered. In connection with the foregoing pump development, the cavitation characteristics of a preliminary visual model, glass-cylinder pump and of a simple reciprocating disk were studied. Subcooling of approximately 0.60 F was obtained from the cavitation produced by reciprocating a disk in boiling nitrogen and in boiling water. The subcooling obtained in a similar manner with liquid hydrogen was somewhat less.

Impact of sacubitril–valsartan combination in patients with chronic heart failure and sleep apnoea syndrome: the ENTRESTO‐SAS study design

PubMed Central

Jaffuel, Dany; Molinari, Nicolas; Berdague, Philippe; Pathak, Atul; Galinier, Michel; Dupuis, Marion; Ricci, Jean‐Etienne; Mallet, Jean‐Pierre; Bourdin, Arnaud

2018-01-01

Abstract Aims Sleep‐disordered breathing (SDB) is a highly prevalent co‐morbidity in patients with chronic heart failure (CHF) and can play a detrimental role in the pathophysiology course of CHF. However, the best way to manage SDB in CHF remains a matter of debate. Sacubitril–valsartan has been included in the 2016 European Society of Cardiology guidelines as an alternative to angiotensin‐converting enzyme inhibitors to further reduce the risk of progression of CHF, CHF hospitalization, and death in ambulatory patients. Sacubitril and valsartan are good candidates for correcting SDB of CHF patients because their known mechanisms of action are likely to counteract the pathophysiology of SDB in CHF. Methods and results The ENTRESTO‐SAS trial is a 3‐month, multicentric, prospective, open‐label real‐life cohort study. Patients eligible for sacubitril–valsartan treatment (i.e. adults with left ventricular ejection fraction ≤35%, who remain symptomatic despite optimal treatment with an angiotensin‐converting enzyme inhibitor, a beta‐blocker, and a mineralocorticoid receptor antagonist) will be evaluated before and after 3 months of treatment (nocturnal ventilatory polygraphy, echocardiography, laboratory testing, and quality‐of‐life and SDB questionnaires). The primary outcome is the change in the Apnoea–Hypopnoea Index, before and after 3 months of treatment. One hundred twenty patients are required to detect a significant 20% improvement of the Apnoea–Hypopnoea Index with a power of 90% at an alpha risk of 5%. Conclusions In the context of the SERVE‐HF study, physicians are waiting for new trials and alternative therapies. We sought to assess in the ENTRESTO‐SAS trial whether sacubitril–valsartan could improve the outcome of SDB in CHF patients. PMID:29469206

Effect of post-discharge follow-up care on re-admissions among US veterans with congestive heart failure: a rural-urban comparison.

PubMed

Muus, Kyle J; Knudson, Alana; Klug, Marilyn G; Gokun, Jane; Sarrazin, Mary; Kaboli, Peter

2010-01-01

Hospital re-admissions for patients with congestive heart failure (CHF) are relatively common and costly occurrences within the US health infrastructure, including the Veterans Affairs (VA) healthcare system. Little is known about CHF re-admissions among rural veteran patients, including the effects of socio-demographics and follow-up outpatient visits on these re-admissions. To examine socio-demographics of US veterans with CHF who had 30 day potentially preventable re-admissions and compare the effect of 30 day VA post-discharge service use on these re-admissions for rural- and urban-dwelling veterans. The 2005-2007 VA data were analyzed to examine patient characteristics and hospital admissions for 36 566 veterans with CHF. The CHF patients who were and were not re-admitted to a VA hospital within 30 days of discharge were identified. Logistic regression was used to examine and compare the effect of VA post-acute service use on re-admissions between rural- and urban-dwelling veterans. Re-admitted veterans tended to be older (p=.002), had disability status (p=.024) and had longer hospital stays (p<.001). Veterans Affairs follow-up visits were negatively associated with re-admissions for both rural and urban veterans with CHF (ORs 0.16-0.76). Rural veterans aged 65 years and older who had VA emergency room visits following discharge were at high risk for re-admission (OR=2.66). Post-acute follow-up care is an important factor for promoting recovery and good health among hospitalized veterans with CHF, regardless of their rural or urban residence. Older, rural veterans with CHF are in need of special attention for VA discharge planning and follow up with primary care providers.

Innovative Telemonitoring Enhanced Care Programme for Chronic Heart Failure (ITEC-CHF) to improve guideline compliance and collaborative care: protocol of a multicentre randomised controlled trial

PubMed Central

Jayasena, Rajiv; Maiorana, Andrew; Dowling, Alison; Chen, Sheau Huey; Karunanithi, Mohan; Layland, Jamie; Edwards, Iain

2017-01-01

Introduction Chronic heart failure (CHF) is a life-threatening chronic disease characterised by periodic exacerbations and recurrent hospitalisations. In the management of CHF, patient compliance with evidence-based clinical guidelines is essential, but remains difficult practically. The objective of this study is to examine whether an Innovative Telemonitoring Enhanced Care Programme for CHF (ITEC-CHF) improves patients’ compliance, and associated health and economic outcomes. Methods and analysis An open multicentre randomised controlled trial has been designed. Patients will be recruited and randomised to receive either ITEC-CHF (n=150) or usual care CHF (n=150) for at least 6 months. ITEC-CHF combines usual care and an additional telemonitoring service including remote weight monitoring, structured telephone support and nurse-led collaborative care. The primary outcomes are the compliance rates with the best-practice guidelines for daily weight monitoring. The secondary outcomes include the compliance with other guideline recommendations (health maintenance, medication, diet and exercise), health (health-related quality of life, risk factors, functional capacity and psychological states) and economic outcomes related to the use of healthcare resources such as hospital readmissions and general practitioner/emergency department visits. Ethics and dissemination The clinical trial has been approved by Peninsula Health Human Research Ethics Committee (HREC Reference: HREC/14/PH/27), Royal Perth Hospital Human Research Ethics Committee (Reference: 15-081) and the Curtin University Human Research Ethics Committee (Reference: HR 181/2014). We will disseminate the final results to the public via conferences and journal publications. A final study report will also be provided to the ethics committees. Trial registration number Registered with Australian New Zealand Clinical Trial Registry (ACTRN12614000916640). PMID:28993389

Heart failure disease management program experience in 4,545 heart failure admissions to a community hospital.

PubMed

Pazin-Filho, Antonio; Peitz, Pamela; Pianta, Thomas; Carson, Kathryn A; Russell, Stuart D; Boulware, Leigh Ebony; Coresh, Josef

2009-09-01

Disease management programs (DMPs) are developed to address the high morbi-mortality and costs of congestive heart failure (CHF). Most studies have focused on intensive programs in academic centers. Washington County Hospital (WCH) in Hagerstown, MD, the primary reference to a semirural county, established a CHF DMP in 2001 with standardized documentation of screening and participation. Linkage to electronic records and state vital statistics enabled examination of the CHF population including individuals participating and those ineligible for the program. All WCH inpatients with CHF International Classification of Diseases, Ninth Revision code in any position of the hospital list discharged alive. Of 4,545 consecutive CHF admissions, only 10% enrolled and of those only 52.2% made a call. Enrollment in the program was related to: age (OR 0.64 per decade older, 95% CI 0.58-0.70), CHF as the main reason for admission (OR 3.58, 95% CI 2.4-4.8), previous admission for CHF (OR 1.14, 95% CI 1.09-1.2), and shorter hospital stay (OR 0.94 per day longer, 95% CI 0.87-0.99). Among DMP participants mortality rates were lowest in the first month (80/1000 person-years) and increased subsequently. The opposite mortality trend occurred in nonenrolled groups with mortality in the first month of 814 per 1000 person-years in refusers and even higher in ineligible (1569/1000 person-years). This difference remained significant after adjustment. Re-admission rates were lower among participants who called consistently (adjusted incidence rate ratio 0.62, 95% CI 0.52-0.77). Only a small and highly select group participated in a low-intensity DMP for CHF in a community-based hospital. Design of DMPs should incorporate these strong selective factors to maximize program impact.

The role of erythropoiesis stimulating agents and intravenous (IV) iron in the cardio renal anemia syndrome.

PubMed

Silverberg, Donald S

2011-11-01

Anemia is common in Congestive Heart Failure (CHF) and is associated with an increased mortality, morbidity and progressive renal failure. The most common causes of the anemia in CHF are (1) the associated Chronic Kidney Disease (CKD), which causes depression of erythropoietin (EPO) production in the kidney, and (2) excessive cytokine production in CHF, which can cause both depression of erythropoietin production in the kidney and depression of erythropoietin response in the bone marrow. The cytokines can also induce iron deficiency by increasing hepcidin production from the liver, which both reduces gastrointestinal iron absorption and reduces iron release from iron stores located in the macrophages and hepatocytes. It appears that iron deficiency is very common in CHF and is rarely recognized or treated. The iron deficiency can cause a thrombocytosis that might contribute to cardiovascular complications in both CHF and CKD and is reversible with iron treatment. Thus, attempts to control this anemia in CHF will have to take into consideration both the use of both Erythropoiesis Stimulating Agents (ESA) such as EPO and oral and, probably more importantly, intravenous (IV) iron. Many studies of anemia in CHF with ESA and oral or IV iron and even with IV iron without ESA have shown a positive effect on hospitalization, New York Heart Association functional class, cardiac and renal function, quality of life, exercise capacity and reduced Beta Natriuretic Peptide and have not demonstrated an increase in cardiovascular damage related to the therapy. However, adequately powered long-term placebo-controlled studies of ESA and of IV iron in CHF are still needed and are currently being carried out.

Multidisciplinary management of chronic heart failure: principles and future trends.

PubMed

Davidson, Patricia M; Newton, Phillip J; Tankumpuan, Thitipong; Paull, G; Dennison-Himmelfarb, Cheryl

2015-10-01

Globally, the management of chronic heart failure (CHF) challenges health systems. The high burden of disease and the costs associated with hospitalization adversely affect individuals, families, and society. Improved quality, access, efficiency, and equity of CHF care can be achieved by using multidisciplinary care approaches if there is adherence and fidelity to the program's elements. The goal of this article was to summarize evidence and make recommendations for advancing practice, education, research, and policy in the multidisciplinary management of patients with CHF. Essential elements of multidisciplinary management of CHF were identified from meta-analyses and clinical practice guidelines. The study factors were discussed from the perspective of the health care system, providers, patients, and their caregivers. Identified gaps in evidence were used to identify areas for future focus in CHF multidisciplinary management. Although there is high-level evidence (including several meta-analyses) for the efficacy of management programs for CHF, less evidence exists to determine the benefit attributable to individual program components or to identify the specific content of effective components and the manner of their delivery. Health care system, provider, and patient factors influence health care models and the effective management of CHF and require focus and attention. Extrapolating trial findings to clinical practice settings is limited by the heterogeneity of study populations and the implementation of models of intervention beyond academic health centers, where practice environments differ considerably. Ensuring that individual programs are both developed and assessed that consider these factors is integral to ensuring adherence and fidelity with the core dimensions of disease management necessary to optimize patient and organizational outcomes. Recognizing the complexity of the multidisciplinary CHF interventions will be important in advancing the design, implementation, and evaluation of the interventions. Copyright © 2015 Elsevier HS Journals, Inc. All rights reserved.

Structural changes of gut microbiota in a rat non-alcoholic fatty liver disease model treated with a Chinese herbal formula.

PubMed

Yin, Xiaochen; Peng, Jinghua; Zhao, Liping; Yu, Yunpeng; Zhang, Xu; Liu, Ping; Feng, Qin; Hu, Yiyang; Pang, Xiaoyan

2013-05-01

Accumulating evidence indicates that disruption of the gut microbiota by a high-fat diet (HFD) may play a pivotal role in the progression of metabolic disorders such as non-alcoholic fatty liver disease (NAFLD). In this study, the structural changes of gut microbiota were analyzed in an HFD-induced NAFLD rat model during treatment with an ancient Chinese herbal formula (CHF) used in clinical practice -Qushi Huayu Fang. CHF treatment significantly reduced body weight, alleviated hepatic steatosis, and decreased the content of triglycerides and free fatty acids in the livers of the rats. Gut microbiota of treated and control rats were profiled with polymerase chain reaction-denaturing gradient gel electrophoresis and bar-coded pyrosequencing of the V3 region of 16S rRNA genes. Both analyses indicated that the CHF-treated group harbored significantly different gut microbiota from that of model rats. Partial least squares discriminant analysis and taxonomy-based analysis were further employed to identify key phylotypes responding to HFD and CHF treatment. Most notably, the genera Escherichia/Shigella, containing opportunistic pathogens, were significantly enriched in HFD-fed rats compared to controls fed normal chow (P<0.05) but they decreased to control levels after CHF treatment. Collinsella, a genus with short chain fatty acid producers, was significantly elevated in CHF-treated rats compared to HFD-fed rats (P<0.05). The results revealed that the bacterial profiles of HFD-induced rats could be modulated by the CHF. Elucidation of these differences in microbiota composition provided a basis for further understanding the pharmacological mechanism of the CHF. Copyright © 2013 Elsevier GmbH. All rights reserved.

Increased NT-proANP predicts risk of congestive heart failure in Cavalier King Charles spaniels with mitral regurgitation caused by myxomatous valve disease.

PubMed

Eriksson, Anders S; Häggström, Jens; Pedersen, Henrik Duelund; Hansson, Kerstin; Järvinen, Anna-Kaisa; Haukka, Jari; Kvart, Clarence

2014-09-01

To evaluate the predictive value of plasma N-terminal pro-atrial natriuretic peptide (NT-proANP) and nitric oxide end-products (NOx) as markers for progression of mitral regurgitation caused by myxomatous mitral valve disease. Seventy-eight privately owned Cavalier King Charles spaniels with naturally occurring myxomatous mitral valve disease. Prospective longitudinal study comprising 312 measurements over a 4.5 year period. Clinical values were recorded, NT-proANP concentrations were measured by radioimmunoassay, and NOx were analyzed colorimetrically. To predict congestive heart failure (CHF), Cox proportional hazards models with time-varying covariates were constructed. The hazard ratio for NT-proANP (per 1000 pmol/l increase) to predict future CHF was 6.7 (95% confidence interval, 3.6-12.5; p < 0.001). The median time to CHF for dogs with NT-proANP levels >1000 pmol/l was 11 months (95% confidence interval, 5.6-12.6 months), compared to 54 months (46 - infinity) for dogs with concentrations ≤ 1000 pmol/l (p < 0.001). Due to intra- and inter-individual variability, most corresponding analyses for NOx were insignificant but dogs reaching CHF had a lower mean NOx concentration than dogs not reaching CHF (23 vs. 28 μmol/l, p = 0.016). Risk of CHF increased with increase in heart rate (>130 beats per minute) and grade of murmur (≥ 3/6). The risk of CHF due to mitral regurgitation is increased in dogs with blood NT-proANP concentrations above 1000 pmol/l. Measurement of NT-proANP can be a valuable tool to identify dogs that may develop CHF within months. Copyright © 2014 Elsevier B.V. All rights reserved.

Usefulness of running wheel for detection of congestive heart failure in dilated cardiomyopathy mouse model.

PubMed

Sugihara, Masami; Odagiri, Fuminori; Suzuki, Takeshi; Murayama, Takashi; Nakazato, Yuji; Unuma, Kana; Yoshida, Ken-ichi; Daida, Hiroyuki; Sakurai, Takashi; Morimoto, Sachio; Kurebayashi, Nagomi

2013-01-01

Inherited dilated cardiomyopathy (DCM) is a progressive disease that often results in death from congestive heart failure (CHF) or sudden cardiac death (SCD). Mouse models with human DCM mutation are useful to investigate the developmental mechanisms of CHF and SCD, but knowledge of the severity of CHF in live mice is necessary. We aimed to diagnose CHF in live DCM model mice by measuring voluntary exercise using a running wheel and to determine causes of death in these mice. A knock-in mouse with a mutation in cardiac troponin T (ΔK210) (DCM mouse), which results in frequent death with a t(1/2) of 70 to 90 days, was used as a DCM model. Until 2 months of age, average wheel-running activity was similar between wild-type and DCM mice (approximately 7 km/day). At approximately 3 months, some DCM mice demonstrated low running activity (LO: <1 km/day) while others maintained high running activity (HI: >5 km/day). In the LO group, the lung weight/body weight ratio was much higher than that in the other groups, and the lungs were infiltrated with hemosiderin-loaded alveolar macrophages. Furthermore, echocardiography showed more severe ventricular dilation and a lower ejection fraction, whereas Electrocardiography (ECG) revealed QRS widening. There were two patterns in the time courses of running activity before death in DCM mice: deaths with maintained activity and deaths with decreased activity. Our results indicate that DCM mice with low running activity developed severe CHF and that running wheels are useful for detection of CHF in mouse models. We found that approximately half of ΔK210 DCM mice die suddenly before onset of CHF, whereas others develop CHF, deteriorate within 10 to 20 days, and die.

Influence of heart failure on resting lung volumes in patients with COPD

PubMed Central

de Souza, Aline Soares; Sperandio, Priscila Abreu; Mazzuco, Adriana; Alencar, Maria Clara; Arbex, Flávio Ferlin; de Oliveira, Mayron Faria; O'Donnell, Denis Eunan; Neder, José Alberto

2016-01-01

ABSTRACT Objective: To evaluate the influence of chronic heart failure (CHF) on resting lung volumes in patients with COPD, i.e., inspiratory fraction-inspiratory capacity (IC)/TLC-and relative inspiratory reserve-[1 − (end-inspiratory lung volume/TLC)]. Methods: This was a prospective study involving 56 patients with COPD-24 (23 males/1 female) with COPD+CHF and 32 (28 males/4 females) with COPD only-who, after careful clinical stabilization, underwent spirometry (with forced and slow maneuvers) and whole-body plethysmography. Results: Although FEV1, as well as the FEV1/FVC and FEV1/slow vital capacity ratios, were higher in the COPD+CHF group than in the COPD group, all major "static" volumes-RV, functional residual capacity (FRC), and TLC-were lower in the former group (p < 0.05). There was a greater reduction in FRC than in RV, resulting in the expiratory reserve volume being lower in the COPD+CHF group than in the COPD group. There were relatively proportional reductions in FRC and TLC in the two groups; therefore, IC was also comparable. Consequently, the inspiratory fraction was higher in the COPD+CHF group than in the COPD group (0.42 ± 0.10 vs. 0.36 ± 0.10; p < 0.05). Although the tidal volume/IC ratio was higher in the COPD+CHF group, the relative inspiratory reserve was remarkably similar between the two groups (0.35 ± 0.09 vs. 0.44 ± 0.14; p < 0.05). Conclusions: Despite the restrictive effects of CHF, patients with COPD+CHF have relatively higher inspiratory limits (a greater inspiratory fraction). However, those patients use only a part of those limits, probably in order to avoid critical reductions in inspiratory reserve and increases in elastic recoil. PMID:27832235

Impact of sacubitril-valsartan combination in patients with chronic heart failure and sleep apnoea syndrome: the ENTRESTO-SAS study design.

PubMed

Jaffuel, Dany; Molinari, Nicolas; Berdague, Philippe; Pathak, Atul; Galinier, Michel; Dupuis, Marion; Ricci, Jean-Etienne; Mallet, Jean-Pierre; Bourdin, Arnaud; Roubille, François

2018-06-01

Sleep-disordered breathing (SDB) is a highly prevalent co-morbidity in patients with chronic heart failure (CHF) and can play a detrimental role in the pathophysiology course of CHF. However, the best way to manage SDB in CHF remains a matter of debate. Sacubitril-valsartan has been included in the 2016 European Society of Cardiology guidelines as an alternative to angiotensin-converting enzyme inhibitors to further reduce the risk of progression of CHF, CHF hospitalization, and death in ambulatory patients. Sacubitril and valsartan are good candidates for correcting SDB of CHF patients because their known mechanisms of action are likely to counteract the pathophysiology of SDB in CHF. The ENTRESTO-SAS trial is a 3-month, multicentric, prospective, open-label real-life cohort study. Patients eligible for sacubitril-valsartan treatment (i.e. adults with left ventricular ejection fraction ≤35%, who remain symptomatic despite optimal treatment with an angiotensin-converting enzyme inhibitor, a beta-blocker, and a mineralocorticoid receptor antagonist) will be evaluated before and after 3 months of treatment (nocturnal ventilatory polygraphy, echocardiography, laboratory testing, and quality-of-life and SDB questionnaires). The primary outcome is the change in the Apnoea-Hypopnoea Index, before and after 3 months of treatment. One hundred twenty patients are required to detect a significant 20% improvement of the Apnoea-Hypopnoea Index with a power of 90% at an alpha risk of 5%. In the context of the SERVE-HF study, physicians are waiting for new trials and alternative therapies. We sought to assess in the ENTRESTO-SAS trial whether sacubitril-valsartan could improve the outcome of SDB in CHF patients. © 2018 The Authors. ESC Heart Failure published by John Wiley & Sons Ltd on behalf of the European Society of Cardiology.

Three dimensional simulation of nucleate boiling heat and mass transfer in cooling passages of internal combustion engines

NASA Astrophysics Data System (ADS)

Mehdipour, R.; Baniamerian, Z.; Delauré, Y.

2016-05-01

An accurate knowledge of heat transfer and temperature distribution in vehicle engines is essential to have a good management of heat transfer performance in combustion engines. This may be achieved by numerical simulation of flow through the engine cooling passages; but the task becomes particularly challenging when boiling occurs. Neglecting two phase flow processes in the simulation would however result in significant inaccuracy in the predictions. In this study a three dimensional numerical model is proposed using Fluent 6.3 to simulate heat transfer of fluid flowing through channels of conventional size. Results of the present theoretical and numerical model are then compared with some empirical results. For high fluid flow velocities, departure between experimental and numerical results is about 9 %, while for lower velocity conditions, the model inaccuracy increases to 18 %. One of the outstanding capabilities of the present model, beside its ability to simulate two phase fluid flow and heat transfer in three dimensions, is the prediction of the location of bubble formation and condensation which can be a key issue in the evaluation of the engine performance and thermal stresses.

Multiphase Flow Technology Impacts on Thermal Control Systems for Exploration

NASA Technical Reports Server (NTRS)

McQuillen, John; Sankovic, John; Lekan, Jack

2006-01-01

The Two-Phase Flow Facility (TPHIFFy) Project focused on bridging the critical knowledge gap by developing and demonstrating critical multiphase fluid products for advanced life support, thermal management and power conversion systems that are required to enable the Vision for Space Exploration. Safety and reliability of future systems will be enhanced by addressing critical microgravity fluid physics issues associated with flow boiling, condensation, phase separation, and system stability. The project included concept development, normal gravity testing, and reduced gravity aircraft flight campaigns, in preparation for the development of a space flight experiment implementation. Data will be utilized to develop predictive models that could be used for system design and operation. A single fluid, two-phase closed thermodynamic loop test bed was designed, assembled and tested. The major components in this test bed include: a boiler, a condenser, a phase separator and a circulating pump. The test loop was instrumented with flow meters, thermocouples, pressure transducers and both high speed and normal speed video cameras. A low boiling point surrogate fluid, FC-72, was selected based on scaling analyses using preliminary designs for operational systems. Preliminary results are presented which include flow regime transitions and some observations regarding system stability.

Atmospheric Pressure Effects on Cryogenic Storage Tank Boil-Off

NASA Technical Reports Server (NTRS)

Sass, J. P.; Frontier, C. R.

2007-01-01

The Cryogenics Test Laboratory (CTL) at the Kennedy Space Center (KSC) routinely utilizes cryostat test hardware to evaluate comparative and absolute thermal conductivities of a wide array of insulation systems. The test method is based on measurement of the flow rate of gas evolved due to evaporative boil-off of a cryogenic liquid. The gas flow rate typically stabilizes after a period of a couple of hours to a couple of days, depending upon the test setup. The stable flow rate value is then used to calculate the thermal conductivity for the insulation system being tested. The latest set of identical cryostats, 1,000-L spherical tanks, exhibited different behavior. On a macro level, the flow rate did stabilize after a couple of days; however the stable flow rate was oscillatory with peak to peak amplitude of up to 25 percent of the nominal value. The period of the oscillation was consistently 12 hours. The source of the oscillation has been traced to variations in atmospheric pressure due to atmospheric tides similar to oceanic tides. This paper will present analysis of this phenomenon, including a calculation that explains why other cryostats are not affected by it.

Elephantiasis Nostras Verrucosa (ENV): a complication of congestive heart failure and obesity.

PubMed

Baird, Drew; Bode, David; Akers, Troy; Deyoung, Zachariah

2010-01-01

Congestive heart failure (CHF) and obesity are common medical conditions that have many complications and an increasing incidence in the United States. Presented here is a case of a disfiguring skin condition that visually highlights the dermatologic consequences of poorly controlled CHF and obesity. This condition will probably become more common as CHF and obesity increase in the US.

Experimental Investigation of Flow Condensation in Microgravity

NASA Technical Reports Server (NTRS)

Lee, Hyoungsoon; Park, Ilchung; Konishi, Christopher; Mudawar, Issam; May, Rochelle I.; Juergens, Jeffery R.; Wagner, James D.; Hall, Nancy R.; Nahra, Henry K.; Hasan, Mohammed M.;

Congestive heart failure and central sleep apnea.

PubMed

Sands, Scott A; Owens, Robert L

2015-07-01

Congestive heart failure (CHF) is among the most common causes of admission to hospitals in the United States, especially in those over age 65. Few data exist regarding the prevalence CHF of Cheyne-Stokes respiration (CSR) owing to congestive heart failure in the intensive care unit (ICU). Nevertheless, CSR is expected to be highly prevalent among those with CHF. Treatment should focus on the underlying mechanisms by which CHF increases loop gain and promotes unstable breathing. Few data are available to determine prevalence of CSR in the ICU, or how CSR might affect clinical management and weaning from mechanical ventilation. Copyright © 2015 Elsevier Inc. All rights reserved.

Congestive Heart Failure and Central Sleep Apnea.

PubMed

Sands, Scott A; Owens, Robert L

2016-03-01

Congestive heart failure (CHF) is among the most common causes of admission to hospitals in the United States, especially in those over age 65. Few data exist regarding the prevalence CHF of Cheyne-Stokes respiration (CSR) owing to congestive heart failure in the intensive care unit (ICU). Nevertheless, CSR is expected to be highly prevalent among those with CHF. Treatment should focus on the underlying mechanisms by which CHF increases loop gain and promotes unstable breathing. Few data are available to determine prevalence of CSR in the ICU, or how CSR might affect clinical management and weaning from mechanical ventilation. Copyright © 2016 Elsevier Inc. All rights reserved.

Circular harmonic filters for the recognition of marine microorganisms

NASA Astrophysics Data System (ADS)

Zavala-Hamz, Victor Antonio; Alvarez-Borrego, Josué

1997-01-01

We present an application of circular-harmonic filters (CHF s) for the recognition of planktonic microorganisms. CHF s discriminated both genera Acartia and Calanus . The symmetry of genus Acartia permitted discrimination to the species and sex levels, whereas the asymmetry of the genus Calanus permitted discrimination only to the generic level. The differences among organisms of different sex of the genus Calanus could not be detected by these particular CHF s. More research needs to be carried out with more complex CHF s to enhance their performance and to permit the implementation of an automated optodigital system to identify and count marine microorganisms.

Allopurinol reduces B-type natriuretic peptide concentrations and haemoglobin but does not alter exercise capacity in chronic heart failure.

PubMed

Gavin, A D; Struthers, A D

2005-06-01

To study whether the effect of allopurinol on improvement of endothelial dysfunction in chronic heart failure (CHF) translates into improved exercise capacity and to examine whether allopurinol also improves B-type natriuretic peptide (BNP), the other important prognostic marker of CHF. Randomised, double blind, placebo controlled crossover trial. Teaching hospital. 50 patients with CHF (New York Heart Association functional classes II and III) were recruited. 50 patients with CHF were randomly assigned to three months' treatment with allopurinol (300 mg/day) or placebo. At two and three months into treatment, they underwent a modified Bruce exercise protocol and a six minute walk test. Blood was taken for BNP and haemoglobin analysis. Neither exercise test was altered by allopurinol. However, plasma BNP concentrations fell significantly (p = 0.035) with allopurinol (11.9 pmol/l) versus placebo (14.4 pmol/l). Haemoglobin concentrations also fell highly significantly with allopurinol (p = 0.001). An important negative finding is that despite high hopes for it, allopurinol had no effect on exercise capacity in CHF. On the other hand, allopurinol did reduce BNP, which is the best available surrogate marker for prognosis in CHF.

Visualisation of flow patterns in straight and C-shape thermosyphons

NASA Astrophysics Data System (ADS)

Ong, K. S.; Tshai, K. H.; Firwana, A.

2017-04-01

A heat pipe is a passive heat transfer device capable of transferring a large quantity of heat effectively and efficiently over a long distance and with a small temperature difference between the heat source and heat sink. A heat pipe consists of a metal pipe initially vacuumed and then filled with a small quantity of fluid inside. The pipe is separated into a heating (evaporator) section and a cooling (condenser) section by an adiabatic section. In a run-around-coil heating, ventilation and air conditioning system, a wrap-around heat pipe heat exchanger could be employed to increase dehumidification and to reduce cooling costs. The thermal performance of a thermosyphon is dependent upon type of fill liquid, fill ratio, power input, pipe inclination and pipe dimensions. The boiling and condensation processes that occur inside a thermosyphon are quite complex. During operation, dry-out, burn-out or boiling limit, entrainment or flooding limit and geysering occur. These phenomena would lead to non-uniform axial wall temperature distribution in the pipe, or worse still, ineffective operation. In order to have a better understanding of the internal heat transfer phenomena, a visual study using transparent glass tubes and high speed camera recording of the internal flow patterns would be most helpful. This paper reports on an experimental investigation conducted to visualise the flow patterns in straight and C-shape thermosyphons. The pictures recorded enabled the internal flow boiling and condensation pattern occurring inside a straight and a C-shape thermosyphon to be observed. The thermosyphons were fabricated from 10 mm O/D × 8 mm I/D × 300 mm long glass tubes and filled with water with fill ratios from 0.5 - 1.5. The evaporator sections of the thermosyphons were immersed into a hot water tank that was electrically heated from cold at ambient temperature till boiling. Cooling of the condenser section was achieved using a fan. Preliminary results showed that dry-out occurred earlier at lower evaporator temperatures with small fill ratios. Further investigations to determine saturation and thermosyphon wall temperatures with various fill liquids and at different fill ratios, inclinations and pipe sizes are necessary with a more sophisticated video recording system.

Lessons learned: design, start-up, and operation of cryogenic systems

NASA Astrophysics Data System (ADS)

Bell, W. M.; Bagley, R. E.; Motew, S.; Young, P.-W.

2014-11-01

Cryogenic systems involving a pumped cryogenic fluid, such as liquid nitrogen (LN2), require careful design since the cryogen is close to its boiling point and cold. At 1 atmosphere, LN2 boils at 77.4 K (-320.4 F). These systems, typically, are designed to transport the cryogen, use it for process heat removal, or for generation of gas (GN2) for process use. As the design progresses, it is important to consider all aspects of the design including, cryogen storage, pressure control and safety relief systems, thermodynamic conditions, equipment and instrument selection, materials, insulation, cooldown, pump start-up, maximum design and minimum flow rates, two phase flow conditions, heat flow, process control to meet and maintain operating conditions, piping integrity, piping loads on served equipment, warm-up, venting, and shut-down. "Cutting corners" in the design process can result in stalled start-ups, field rework, schedule hits, or operational restrictions. Some of these "lessoned learned" are described in this paper.

Boiling Water at Hot Creek - The Dangerous and Dynamic Thermal Springs in California's Long Valley Caldera

USGS Publications Warehouse

Farrar, Christopher D.; Evans, William C.; Venezky, Dina Y.; Hurwitz, Shaul; Oliver, Lynn K.

2007-01-01

The beautiful blue pools and impressive boiling fountains along Hot Creek in east-central California have provided enjoyment to generations of visitors, but they have also been the cause of injury or death to some who disregarded warnings and fences. The springs and geysers in the stream bed and along its banks change location, temperature, and flow rates frequently and unpredictably. The hot springs and geysers of Hot Creek are visible signs of dynamic geologic processes in this volcanic region, where underground heat drives thermal spring activity.

Review of nucleation and incipient boiling under pool and forced convection conditions

NASA Technical Reports Server (NTRS)

Merte, Herman, Jr.

1987-01-01

An overview of liquid-vapor nucleation is given. The result of thermodynamic equilibrium across curved liquid-vapor interfaces is presented. The extension of this to include the interaction with idealizations of surface cavities is made to demonstrate how superheat requirements for nucleation will be affected by surface roughness, flow velocity and buoyancy. Experimental measurements of high liquid superheats and nucleation delay times are presented as examples of homogeneous nucleation. Examples of nucleation and boiling on smooth glass substrates and on metal surfaces with various surface roughnesses are presented.

Pancreatic exocrine insufficiency in patients with chronic heart failure and its possible association with appetite loss

PubMed Central

2017-01-01

Background Appetite loss is one complication of chronic heart failure (CHF), and its association with pancreatic exocrine insufficiency (PEI) is not well investigated in CHF. Aim We attempted to detect the association between PEI and CHF-induced appetite. Methods Patients with CHF were enrolled, and body mass index (BMI), left ventricular ejection fraction (LVEF), New York Heart Association (NYHA) cardiac function grading, B-type natriuretic peptide (BNP), serum albumin, pro-albumin and hemoglobin were evaluated. The pancreatic exocrine function was measured by fecal elastase-1 (FE-1) levels in the enrolled patients. Appetite assessment was tested by completing the simplified nutritional appetite questionnaire (SNAQ). The improvement of appetite loss by supplemented pancreatic enzymes was also researched in this study. Results The decrease of FE-1 levels was found in patients with CHF, as well as SNAQ scores. A positive correlation was observed between SNAQ scores and FE-1 levels (r = 0.694, p < 0.001). Pancreatic enzymes supplement could attenuate the decrease of SNAQ scores in CHF patients with FE-1 levels <200 μg/g stool and SNAQ < 14. Conclusions Appetite loss is commonly seen in CHF, and is partially associated with pancreatic exocrine insufficiency. Oral pancreatic enzyme replacement therapy attenuates the chronic heart failure-induced appetite loss. These results suggest a possible pancreatic-cardiac relationship in chronic heart failure, and further experiment is needed for clarifying the possible mechanisms. PMID:29155861

Digital vs. conventional implant prosthetic workflows: a cost/time analysis.

PubMed

Joda, Tim; Brägger, Urs

2015-12-01

The aim of this prospective cohort trial was to perform a cost/time analysis for implant-supported single-unit reconstructions in the digital workflow compared to the conventional pathway. A total of 20 patients were included for rehabilitation with 2 × 20 implant crowns in a crossover study design and treated consecutively each with customized titanium abutments plus CAD/CAM-zirconia-suprastructures (test: digital) and with standardized titanium abutments plus PFM-crowns (control conventional). Starting with prosthetic treatment, analysis was estimated for clinical and laboratory work steps including measure of costs in Swiss Francs (CHF), productivity rates and cost minimization for first-line therapy. Statistical calculations were performed with Wilcoxon signed-rank test. Both protocols worked successfully for all test and control reconstructions. Direct treatment costs were significantly lower for the digital workflow 1815.35 CHF compared to the conventional pathway 2119.65 CHF [P = 0.0004]. For subprocess evaluation, total laboratory costs were calculated as 941.95 CHF for the test group and 1245.65 CHF for the control group, respectively [P = 0.003]. The clinical dental productivity rate amounted to 29.64 CHF/min (digital) and 24.37 CHF/min (conventional) [P = 0.002]. Overall, cost minimization analysis exhibited an 18% cost reduction within the digital process. The digital workflow was more efficient than the established conventional pathway for implant-supported crowns in this investigation. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Telemedicine Facilitates CHF Home Health Care for Those with Systolic Dysfunction

PubMed Central

Seibert, Pennie S.; Whitmore, Tiffany A.; Patterson, Carin; Parker, Patrick D.; Otto, Caitlin; Basom, Jean; Whitener, Nichole; Zimmerman, Christian G.

2008-01-01

An estimated 5 million Americans have congestive heart failure (CHF) and one in five over the age of 40 will develop CHF. There are numerous examples of CHF patients living beyond the years normally expected for people with the disease, usually attributed to taking an active role in disease management. A relatively new alternative for CHF outpatient care is telemedicine and e-health. We investigated the effects of a 6-week in-home telemedicine education and monitoring program for those with systolic dysfunction on the utilization of health care resources. We also measured the effects of the unit 4.5 months after its removal (a total of 6 months post introduction of the unit into the home). Concurrently, we assessed participants' perceptions of the value of having a telemedicine unit. Participants in the telemedicine group reported weighing more times a week with less variability than did the control group. Telemedicine led to a reduction in physician and emergency department visits and those in the experimental group reported the unit facilitating self-care, though this was not significantly different from the control group (possibly due to small sample size). These findings suggest a possibility for improvement in control of CHF when telemedicine is implemented. Our review of the literature also supports the role of telemedicine in facilitating home health care and self-management for CHF patients. There are many challenges still to be addressed before this potential can be reached and further research is needed to identify opportunities in telemedicine. PMID:18369411

Ambulatory Monitoring of Congestive Heart Failure by Multiple Bioelectric Impedance Vectors

PubMed Central

Khoury, Dirar S.; Naware, Mihir; Siou, Jeff; Blomqvist, Andreas; Mathuria, Nilesh S.; Wang, Jianwen; Shih, Hue-Teh; Nagueh, Sherif F.; Panescu, Dorin

2009-01-01

Objectives To investigate properties of multiple bioelectric impedance signals recorded during congestive heart failure (CHF) by utilizing various electrode configurations of an implanted cardiac resynchronization therapy (CRT) system. Background Monitoring of CHF has relied mainly on right-heart sensors. Methods Fifteen normal dogs underwent implantation of CRT systems using standard leads. An additional left atrial (LA) pressure lead-sensor was implanted in 5 dogs. Continuous rapid right ventricular (RV) pacing was applied over several weeks. Left ventricular (LV) catheterization and echocardiography were performed biweekly. Six steady-state impedance signals, utilizing intrathorcaic and intracardiac vectors, were measured via ring (r), coil (c), and device Can electrodes. Results All animals developed CHF after 2–4 weeks of pacing. Impedance diminished gradually during CHF induction, but at varying rates for different vectors. Impedance during CHF decreased significantly in all measured vectors: LVr-Can, −17%; LVr-RVr, −15%; LVr-RAr, −11%; RVr-Can, −12%; RVc-Can, −7%; RAr-Can, −5%. The LVr-Can vector reflected both the fastest and largest change in impedance in comparison to vectors employing only right-heart electrodes, and was highly reflective of changes in LV end-diastolic volume and LA pressure. Conclusions Impedance, acquired via different lead-electrodes, have variable responses to CHF. Impedance vectors employing a LV lead are highly responsive to physiologic changes during CHF. Measuring multiple impedance signals could be useful for optimizing ambulatory monitoring in heart failure patients. PMID:19298923

Method and apparatus for processing a test sample to concentrate an analyte in the sample from a solvent in the sample

DOEpatents

Turner, Terry D.; Beller, Laurence S.; Clark, Michael L.; Klingler, Kerry M.

1997-01-01

A method of processing a test sample to concentrate an analyte in the sample from a solvent in the sample includes: a) boiling the test sample containing the analyte and solvent in a boiling chamber to a temperature greater than or equal to the solvent boiling temperature and less than the analyte boiling temperature to form a rising sample vapor mixture; b) passing the sample vapor mixture from the boiling chamber to an elongated primary separation tube, the separation tube having internal sidewalls and a longitudinal axis, the longitudinal axis being angled between vertical and horizontal and thus having an upper region and a lower region; c) collecting the physically transported liquid analyte on the internal sidewalls of the separation tube; and d) flowing the collected analyte along the angled internal sidewalls of the separation tube to and pass the separation tube lower region. The invention also includes passing a turbulence inducing wave through a vapor mixture to separate physically transported liquid second material from vaporized first material. Apparatus are also disclosed for effecting separations. Further disclosed is a fluidically powered liquid test sample withdrawal apparatus for withdrawing a liquid test sample from a test sample container and for cleaning the test sample container.

Method and apparatus for processing a test sample to concentrate an analyte in the sample from a solvent in the sample

DOEpatents

Turner, T.D.; Beller, L.S.; Clark, M.L.; Klingler, K.M.

1997-10-14

A method of processing a test sample to concentrate an analyte in the sample from a solvent in the sample includes: (a) boiling the test sample containing the analyte and solvent in a boiling chamber to a temperature greater than or equal to the solvent boiling temperature and less than the analyte boiling temperature to form a rising sample vapor mixture; (b) passing the sample vapor mixture from the boiling chamber to an elongated primary separation tube, the separation tube having internal sidewalls and a longitudinal axis, the longitudinal axis being angled between vertical and horizontal and thus having an upper region and a lower region; (c) collecting the physically transported liquid analyte on the internal sidewalls of the separation tube; and (d) flowing the collected analyte along the angled internal sidewalls of the separation tube to and pass the separation tube lower region. The invention also includes passing a turbulence inducing wave through a vapor mixture to separate physically transported liquid second material from vaporized first material. Apparatus is also disclosed for effecting separations. Further disclosed is a fluidically powered liquid test sample withdrawal apparatus for withdrawing a liquid test sample from a test sample container and for cleaning the test sample container. 8 figs.

Modeling of coupled heat transfer and reactive transport processesin porous media: Application to seepage studies at Yucca Mountain, Nevada

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mukhopadhyay, Sumit; Sonnenthal, Eric L.; Spycher, Nicolas

When hot radioactive waste is placed in subsurface tunnels, a series of complex changes occurs in the surrounding medium. The water in the pore space of the medium undergoes vaporization and boiling. Subsequently, vapor migrates out of the matrix pore space, moving away from the tunnel through the permeable fracture network. This migration is propelled by buoyancy, by the increased vapor pressure caused by heating and boiling, and through local convection. In cooler regions, the vapor condenses on fracture walls, where it drains through the fracture network. Slow imbibition of water thereafter leads to gradual rewetting of the rock matrix.more » These thermal and hydrological processes also bring about chemical changes in the medium. Amorphous silica precipitates from boiling and evaporation, and calcite from heating and CO2 volatilization. The precipitation of amorphous silica, and to a much lesser extent calcite, results in long-term permeability reduction. Evaporative concentration also results in the precipitation of gypsum (or anhydrite), halite, fluorite and other salts. These evaporative minerals eventually redissolve after the boiling period is over, however, their precipitation results in a significant temporary decrease in permeability. Reduction of permeability is also associated with changes in fracture capillary characteristics. In short, the coupled thermal-hydrological-chemical (THC) processes dynamically alter the hydrological properties of the rock. A model based on the TOUGHREACT reactive transport software is presented here to investigate the impact of THC processes on flow near an emplacement tunnel at Yucca Mountain, Nevada. We show how transient changes in hydrological properties caused by THC processes often lead to local flow channeling and saturation increases above the tunnel. For models that include only permeability changes to fractures, such local flow channeling may lead to seepage relative to models where THC effects are ignored. However, coupled THC seepage models that include both permeability and capillary changes to fractures may not show this additional seepage.« less

Modeling of coupled heat transfer and reactive transport processesin porous media: Application to seepage studies at Yucca Mountain, Nevada

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mukhopadhyay, S.; Sonnenthal, E.L.; Spycher, N.

When hot radioactive waste is placed in subsurface tunnels, a series of complex changes occurs in the surrounding medium. The water in the pore space of the medium undergoes vaporization and boiling. Subsequently, vapor migrates out of the matrix pore space, moving away from the tunnel through the permeable fracture network. This migration is propelled by buoyancy, by the increased vapor pressure caused by heating and boiling, and through local convection. In cooler regions, the vapor condenses on fracture walls, where it drains through the fracture network. Slow imbibition of water thereafter leads to gradual rewetting of the rock matrix.more » These thermal and hydrological processes also bring about chemical changes in the medium. Amorphous silica precipitates from boiling and evaporation, and calcite from heating and CO{sub 2} volatilization. The precipitation of amorphous silica, and to a much lesser extent calcite, results in long-term permeability reduction. Evaporative concentration also results in the precipitation of gypsum (or anhydrite), halite, fluorite and other salts. These evaporative minerals eventually redissolve after the boiling period is over, however, their precipitation results in a significant temporary decrease in permeability. Reduction of permeability is also associated with changes in fracture capillary characteristics. In short, the coupled thermal-hydrological-chemical (THC) processes dynamically alter the hydrological properties of the rock. A model based on the TOUGHREACT reactive transport software is presented here to investigate the impact of THC processes on flow near an emplacement tunnel at Yucca Mountain, Nevada. We show how transient changes in hydrological properties caused by THC processes often lead to local flow channeling and saturation increases above the tunnel. For models that include only permeability changes to fractures, such local flow channeling may lead to seepage relative to models where THC effects are ignored. However, coupled THC seepage models that include both permeability and capillary changes to fractures may not show this additional seepage.« less

An Investigation Into: I) Active Flow Control for Cold-Start Performance Enhancement of a Pump-Assisted, Capillary-Driven, Two-Phase Cooling Loop II) Surface Tension of n-Pentanol + Water, a Self-Rewetting Working Fluid, From 25 °C to 85 °C

NASA Astrophysics Data System (ADS)

Bejarano, Roberto Villa

Cold-start performance enhancement of a pump-assisted, capillary-driven, two-phase cooling loop was attained using proportional integral and fuzzy logic controls to manage the boiling condition inside the evaporator. The surface tension of aqueous solutions of n-Pentanol, a self-rewetting fluid, was also investigated for enhancing heat transfer performance of capillary driven (passive) thermal devices was also studied. A proportional-integral control algorithm was used to regulate the boiling condition (from pool boiling to thin-film boiling) and backpressure in the evaporator during cold-start and low heat input conditions. Active flow control improved the thermal resistance at low heat inputs by 50% compared to the baseline (constant flow rate) case, while realizing a total pumping power savings of 56%. Temperature overshoot at start-up was mitigated combining fuzzy-logic with a proportional-integral controller. A constant evaporator surface temperature of 60°C with a variation of +/-8°C during start-up was attained with evaporator thermal resistances as low as 0.10 cm2--K/W. The surface tension of aqueous solutions of n-Pentanol, a self-rewetting working fluid, as a function of concentration and temperature were also investigated. Self-rewetting working fluids are promising in two-phase heat transfer applications because they have the ability to passively drive additional working fluid towards the heated surface; thereby increasing the dryout limitations of the thermal device. Very little data is available in literature regarding the surface tension of these fluids due to the complexity involved in fluid handling, heating, and experimentation. Careful experiments were performed to investigate the surface tension of n-Pentanol + water. The concentration and temperature range investigated were from 0.25%wt. to1.8%wt and 25°C to 85°C, respectively.

2. RW Meyer Sugar Mill: 18761899. Threeroll sugar mill, oneton ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

2. RW Meyer Sugar Mill: 1876-1899. Three-roll sugar mill, one-ton daily processing capacity. Manufactured by Edwin Maw, Liverpool, England, ca. 1855-1870. View: Top roll and one bottom roll, mill housing or cheeks, and spur pinion gears. The broken projection on the mill beside the bottom roll indicates the location of the cane tray. The cane juice crushed from the cane flowed into the juice tray below the bottom rolls. It then flowed into a wooden gutter and through a short tunnel in the mill's masonry enclosure and on to the boiling house for further processing. The opening at the base of the masency wall (In the photograph) is where the gutter ran from the mill to the boiling house. - R. W. Meyer Sugar Mill, State Route 47, Kualapuu, Maui County, HI

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barber, Jacqueline; Aix-Marseille Universite; Brutin, David

Boiling in microchannels remains elusive due to the lack of full understanding of the mechanisms involved. A powerful tool in achieving better comprehension of the mechanisms is detailed imaging and analysis of the two-phase flow at a fundamental level. Boiling is induced in a single microchannel geometry (hydraulic diameter 727 {mu}m), using a refrigerant FC-72, to investigate the effect of channel confinement on bubble growth. A transparent, metallic, conductive deposit has been developed on the exterior of the rectangular microchannel, allowing simultaneous uniform heating and visualisation to be achieved. The data presented in this paper is for a particular casemore » with a uniform heat flux applied to the microchannel and inlet liquid mass flowrate held constant. In conjunction with obtaining high-speed images and videos, sensitive pressure sensors are used to record the pressure drop across the microchannel over time. Bubble nucleation and growth, as well as periodic slug flow, are observed in the microchannel test section. The periodic pressure fluctuations evidenced across the microchannel are caused by the bubble dynamics and instances of vapour blockage during confined bubble growth in the channel. The variation of the aspect ratio and the interface velocities of the growing vapour slug over time, are all observed and analysed. We follow visually the nucleation and subsequent both 'free' and 'confined' growth of a vapour bubble during flow boiling of FC-72 in a microchannel, from analysis of our results, images and video sequences with the corresponding pressure data obtained. (author)« less

Using noble gases measured in spring discharge to trace hydrothermal processes in the Norris Geyser Basin, Yellowstone National Park, U.S.A.

USGS Publications Warehouse

Gardner, W.P.; Susong, D.D.; Solomon, D.K.; Heasler, H.P.

2010-01-01

Dissolved noble gas concentrations in springs are used to investigate boiling of hydrothermal water and mixing of hydrothermal and shallow cool water in the Norris Geyser Basin area. Noble gas concentrations in water are modeled for single stage and continuous steam removal. Limitations on boiling using noble gas concentrations are then used to estimate the isotopic effect of boiling on hydrothermal water, allowing the isotopic composition of the parent hydrothermal water to be determined from that measured in spring. In neutral chloride springs of the Norris Geyser Basin, steam loss since the last addition of noble gas charged water is less than 30% of the total hydrothermal discharge, which results in an isotopic shift due to boiling of ?? 2.5% ??D. Noble gas concentrations in water rapidly and predictably change in dual phase systems, making them invaluable tracers of gas-liquid interaction in hydrothermal systems. By combining traditional tracers of hydrothermal flow such as deuterium with dissolved noble gas measurements, more complex hydrothermal processes can be interpreted. ?? 2010 Elsevier B.V.

A User’s Guide to the PLTEMP/ANL Code

DOE Office of Scientific and Technical Information (OSTI.GOV)

Olson, A. P.; Kalimullah, M.; Feldman, E. E.

2016-07-25

PLTEMP/ANL V4.2 is a program that obtains a steady-state flow and temperature solution for a nuclear reactor core, or for a single fuel assembly. It is based on an evolutionary sequence of codes originally used for plate temperatures, hence “PLTEMP”, developed at Argonne National Laboratory over several decades. Fueled and non-fueled regions are modeled. Each fuel assembly consists of one or more plates or tubes separated by coolant channels. The fuel plates may have one to five layers of different materials, each with heat generation. The width of a fuel plate may be divided into multiple longitudinal stripes, each withmore » its own axial power shape. The temperature solution is effectively 2-dimensional. It begins with a one-dimensional solution across all coolant channels and fuel plates or tubes within a given fuel assembly, at the entrance to the assembly. The temperature solution is repeated for each axial node along the length of the fuel assembly. The geometry may be either slab or radial, corresponding to fuel assemblies made of a series of flat (or slightly curved) plates, or of nested tubes. A variety of thermal-hydraulic correlations are available with which to determine safety margins such as onset-of-nucleate boiling ratio(ONBR), departure from nucleate boiling ratio (DNBR), and onset of flow instability ratio (OFIR). Coolant properties for either light or heavy water are obtained from FORTRAN functions rather than from tables. The code is intended for thermal-hydraulic analysis of research reactor performance in the sub-cooled boiling regime. Both turbulent and laminar flow regimes can be modeled. Options to calculate both forced flow and natural circulation are available. A general search capability is available (Appendix XII) to greatly reduce the reactor analyst’s time.« less

Cheyne-Stokes respiration in patients with congestive heart failure.

PubMed

Brack, Thomas

2003-12-13

Cheyne-Stokes Respiration (CSR) is a breathing pattern characterised by rhythmic oscillation of tidal volume with regularly recurring periods of hyperpnoea, hypopnoea and apnoea. CSR is no longer solely regarded as a symptom of severe congestive heart failure (CHF), but has been recognised as an independent risk factor for worsening heart failure and reduced survival in patients with CHF. CSR is associated with frequent awakening that fragment sleep and with concomitant sympathetic activation both of which may worsen CHF. Cheyne-Stokes Respiration is very common in patients with severe CHF and its prevalence may have been underestimated in the past due to technical limitations that precluded respiratory monitoring outside sleep laboratories. Since treatment of CSR appears to be beneficial and safe, patients at risk should be promptly diagnosed and treated. Treatment of CSR has been demonstrated to improve left ventricular ejection fraction and potentially prolongs survival in patients with severe CHF. This article briefly summarises the current knowledge of the patho-physiology, prevalence and therapy of Cheyne-Stokes respiration.

Evaluation of a nurse practitioner disease management model for chronic heart failure: a multi-site implementation study.

PubMed

Lowery, Julie; Hopp, Faith; Subramanian, Usha; Wiitala, Wyndy; Welsh, Deborah E; Larkin, Angela; Stemmer, Karen; Zak, Cassandra; Vaitkevicius, Peter

2012-01-01

While disease management appears to be effective in selected, small groups of CHF patients from randomized controlled trials, its effectiveness in a broader CHF patient population is not known. This prospective, quasi-experimental study compared patient outcomes under a nurse practitioner-led disease management model (intervention group) with outcomes under usual care (control group) in both primary and tertiary medical centers. The study included 969 veterans (458 intervention, 511 control) treated for CHF at six VA medical centers. Intervention patients had significantly fewer (p<0.05) CHF and all-cause admissions at one-year follow-up, and lower mortality at both one- and two-year follow-up. These data provide support for the potential effectiveness of the intervention, and suggest that the evidence from RCTs of disease management models for CHF can be translated into clinical practice, even without the benefits of a selected patient population and dedicated resources often found in RCTs. © 2011 Wiley Periodicals, Inc.

Reduced Data Dualscale Entropy Analysis of HRV Signals for Improved Congestive Heart Failure Detection

NASA Astrophysics Data System (ADS)

Kuntamalla, Srinivas; Lekkala, Ram Gopal Reddy

2014-10-01

Heart rate variability (HRV) is an important dynamic variable of the cardiovascular system, which operates on multiple time scales. In this study, Multiscale entropy (MSE) analysis is applied to HRV signals taken from Physiobank to discriminate Congestive Heart Failure (CHF) patients from healthy young and elderly subjects. The discrimination power of the MSE method is decreased as the amount of the data reduces and the lowest amount of the data at which there is a clear discrimination between CHF and normal subjects is found to be 4000 samples. Further, this method failed to discriminate CHF from healthy elderly subjects. In view of this, the Reduced Data Dualscale Entropy Analysis method is proposed to reduce the data size required (as low as 500 samples) for clearly discriminating the CHF patients from young and elderly subjects with only two scales. Further, an easy to interpret index is derived using this new approach for the diagnosis of CHF. This index shows 100 % accuracy and correlates well with the pathophysiology of heart failure.

Future forest aboveground carbon dynamics in the central United States: the importance of forest demographic processes

Treesearch

Wenchi Jin; Hong S. He; Frank R. Thompson; Wen J. Wang; Jacob S. Fraser; Stephen R. Shifley; Brice B. Hanberry; William D. Dijak

2017-01-01

The Central Hardwood Forest (CHF) in the United States is currently a major carbon sink, there are uncertainties in how long the current carbon sink will persist and if the CHF will eventually become a carbon source. We used a multi-model ensemble to investigate aboveground carbon density of the CHF from 2010 to 2300 under current climate. Simulations were done using...

An Investigation of Emotion Recognition and Theory of Mind in People with Chronic Heart Failure

PubMed Central

Habota, Tina; McLennan, Skye N.; Cameron, Jan; Ski, Chantal F.; Thompson, David R.; Rendell, Peter G.

2015-01-01

Objectives Cognitive deficits are common in patients with chronic heart failure (CHF), but no study has investigated whether these deficits extend to social cognition. The present study provided the first empirical assessment of emotion recognition and theory of mind (ToM) in patients with CHF. In addition, it assessed whether each of these social cognitive constructs was associated with more general cognitive impairment. Methods A group comparison design was used, with 31 CHF patients compared to 38 demographically matched controls. The Ekman Faces test was used to assess emotion recognition, and the Mind in the Eyes test to measure ToM. Measures assessing global cognition, executive functions, and verbal memory were also administered. Results There were no differences between groups on emotion recognition or ToM. The CHF group’s performance was poorer on some executive measures, but memory was relatively preserved. In the CHF group, both emotion recognition performance and ToM ability correlated moderately with global cognition (r = .38, p = .034; r = .49, p = .005, respectively), but not with executive function or verbal memory. Conclusion CHF patients with lower cognitive ability were more likely to have difficulty recognizing emotions and inferring the mental states of others. Clinical implications of these findings are discussed. PMID:26529409

Serum level of uric acid, partly secreted from the failing heart, is a prognostic marker in patients with congestive heart failure.

PubMed

Sakai, Hiroshi; Tsutamoto, Takayoshi; Tsutsui, Takashi; Tanaka, Toshinari; Ishikawa, Chitose; Horie, Minoru

2006-08-01

A recent study suggested that xanthine oxidase is activated in congestive heart failure (CHF). However, whether uric acid (UA) is secreted from the failing heart remains unknown, so it is currently unclear whether serum UA can provide prognostic information independent of brain natriuretic peptide (BNP). Serum UA was measured in the aortic root (AO) and the coronary sinus (CS) of 74 patients with CHF. The serum UA level was significantly higher in the CS than in the AO. The transcardiac gradient of UA (CS-AO) increased with the severity of CHF, inversely correlated with left ventricular ejection fraction (LVEF) and positively correlated with left ventricular end-diastolic volume index. The plasma levels of norepinephrine, BNP, UA, and LVEF were monitored prospectively in 150 CHF patients for a mean follow-up of 3 years. High plasma levels of UA (p<0.001) and BNP (p<0.001) were shown by multivariate stepwise analysis to be independent predictors of mortality. High plasma UA level, partly secreted from the failing heart, is a prognostic predictor independent of BNP in patients with CHF. Monitoring a combination of BNP and UA may be useful for the management of patients with CHF.

Cerebral metabolic abnormalities in congestive heart failure detected by proton magnetic resonance spectroscopy.

PubMed

Lee, C W; Lee, J H; Kim, J J; Park, S W; Hong, M K; Kim, S T; Lim, T H; Park, S J

1999-04-01

Using proton magnetic resonance spectroscopy, we investigated cerebral metabolism and its determinants in congestive heart failure (CHF), and the effects of cardiac transplantation on these measurements. Few data are available about cerebral metabolism in CHF. Fifty patients with CHF (ejection fraction < or = 35%) and 20 healthy volunteers were included for this study. Of the patients, 10 patients underwent heart transplantation. All subjects performed symptom-limited bicycle exercise test. Proton magnetic resonance spectroscopy (1H MRS) was obtained from localized regions (8 to 10 ml) of occipital gray matter (OGM) and parietal white matter (PWM). Absolute levels of the metabolites (N-acetylaspartate, creatine, choline, myo-inositol) were calculated. In PWM only creatine level was significantly lower in CHF than in control subjects, but in OGM all four metabolite levels were decreased in CHF. The creatine level was independently correlated with half-recovery time and duration of heart failure symptoms in PWM (r = -0.56, p < 0.05), and with peak oxygen consumption and serum sodium concentration in OGM (r = 0.58, p < 0.05). Cerebral metabolic abnormalities were improved after successful cardiac transplantation. This study shows that cerebral metabolism is abnormally deranged in advanced CHF and it may serve as a potential marker of the disease severity.

Determining the Concentrations and Temperatures of Products in a CF_4/CHF_3/N_2 Plasma via Submillimeter Absorption Spectroscopy

NASA Astrophysics Data System (ADS)

Helal, Yaser H.; Neese, Christopher F.; De Lucia, Frank C.; Ewing, Paul R.; Agarwal, Ankur; Craver, Barry; Stout, Phillip J.; Armacost, Michael D.

2017-06-01

Plasmas used for the manufacturing of semiconductor devices are similar in pressure and temperature to those used in the laboratory for the study of astrophysical species in the submillimeter (SMM) spectral region. The methods and technology developed in the SMM for these laboratory studies are directly applicable for diagnostic measurements in the semiconductor manufacturing industry. Many of the molecular neutrals, radicals, and ions present in processing plasmas have been studied and their spectra have been cataloged or are in the literature. In this work, a continuous wave, intensity calibrated SMM absorption spectrometer was developed as a remote sensor of gas and plasma species. A major advantage of intensity calibrated rotational absorption spectroscopy is its ability to determine absolute concentrations and temperatures of plasma species from first principles without altering the plasma environment. An important part of this work was the design of the optical components which couple 500-750 GHz radiation through a commercial inductively coupled plasma chamber. The measurement of transmission spectra was simultaneously fit for background and absorption signal. The measured absorption was used to calculate absolute densities and temperatures of polar species. Measurements for CHF_3, CF_2, FCN, HCN, and CN made in a CF_4/CHF_3/N_2 plasma will be presented. Temperature equilibrium among species will be shown and the common temperature is leveraged to obtain accurate density measurements for simultaneously observed species. The densities and temperatures of plasma species are studied as a function of plasma parameters, including flow rate, pressure, and discharge power.

Experimental evidence for the blue-shifted hydrogen-bonded complexes of CHF3 with π-electron donors.

PubMed

Gopi, R; Ramanathan, N; Sundararajan, K

2017-06-15

Blue-shifted hydrogen-bonded complexes of fluoroform (CHF 3 ) with benzene (C 6 H 6 ) and acetylene (C 2 H 2 ) have been investigated using matrix isolation infrared spectroscopy and ab initio computations. For CHF 3 -C 6 H 6 complex, calculations performed at the B3LYP and MP2 levels of theory using 6-311++G (d,p) and aug-cc-pVDZ basis sets discerned two minima corresponding to a 1:1 hydrogen-bonded complex. The global minimum correlated to a structure, where the interaction is between the hydrogen of CHF 3 and the π-electrons of C 6 H 6 and a weak local minimum was stabilized through H…F interaction. For the CHF 3 -C 2 H 2 complex, computation performed at MP2/aug-cc-pVDZ level of theory yielded two minima, corresponding to the cyclic C-H…π complex A (global) and a linear C-H…F (n-σ) complex B (local). Experimentally a blue-shift of 32.3cm -1 and 7.7cm -1 was observed in the ν 1 C-H stretching mode of CHF 3 sub-molecule in Ar matrix for the 1:1 C-H…π complexes of CHF 3 with C 6 H 6 and C 2 H 2 respectively. Natural bond orbital (NBO), Atoms-in-molecule (AIM) and energy decomposition (EDA) analyses were carried out to explain the blue-shifting and the nature of the interaction in these complexes. Copyright © 2017 Elsevier B.V. All rights reserved.

Genome-wide sequencing and quantification of circulating microRNAs for dogs with congestive heart failure secondary to myxomatous mitral valve degeneration.

PubMed

Jung, SeungWoo; Bohan, Amy

2018-02-01

OBJECTIVE To characterize expression profiles of circulating microRNAs via genome-wide sequencing for dogs with congestive heart failure (CHF) secondary to myxomatous mitral valve degeneration (MMVD). ANIMALS 9 healthy client-owned dogs and 8 age-matched client-owned dogs with CHF secondary to MMVD. PROCEDURES Blood samples were collected before administering cardiac medications for the management of CHF. Isolated microRNAs from plasma were classified into microRNA libraries and subjected to next-generation sequencing (NGS) for genome-wide sequencing analysis and quantification of circulating microRNAs. Quantitative reverse transcription PCR (qRT-PCR) assays were used to validate expression profiles of differentially expressed circulating microRNAs identified from NGS analysis of dogs with CHF. RESULTS 326 microRNAs were identified with NGS analysis. Hierarchical analysis revealed distinct expression patterns of circulating microRNAs between healthy dogs and dogs with CHF. Results of qRT-PCR assays confirmed upregulation of 4 microRNAs (miR-133, miR-1, miR-let-7e, and miR-125) and downregulation of 4 selected microRNAs (miR-30c, miR-128, miR-142, and miR-423). Results of qRT-PCR assays were highly correlated with NGS data and supported the specificity of circulating microRNA expression profiles in dogs with CHF secondary to MMVD. CONCLUSIONS AND CLINICAL RELEVANCE These results suggested that circulating microRNA expression patterns were unique and could serve as molecular biomarkers of CHF in dogs with MMVD.

Exercise training leads to a reduction of elevated myostatin levels in patients with chronic heart failure.

PubMed

Lenk, Karsten; Erbs, Sandra; Höllriegel, Robert; Beck, Ephraim; Linke, Axel; Gielen, Stephan; Winkler, Sven Möbius; Sandri, Marcus; Hambrecht, Rainer; Schuler, Gerhard; Adams, Volker

2012-06-01

In chronic heart failure (CHF), cardiac cachexia is often associated with the terminal stage of this disease. In animal studies it has been demonstrated that myostatin, a key regulator of skeletal muscle mass, is elevated in advanced stages of this syndrome. The aim of the present study was to investigate the expression of myostatin in patients with late stage CHF (NYHA IIIb) in comparison to healthy subjects. Furthermore the effects of physical exercise on myostatin were analyzed. Twenty-four patients were either randomized to a sedentary control group (CHF-S) or exercise training (CHF-E). At baseline and after 12 weeks mRNA and myostatin protein in the peripheral skeletal muscle as well as myostatin serum concentration were measured. Furthermore 12 age-matched healthy men were compared to all patients at baseline (HC). CHF patients showed a two-fold increase of myostatin mRNA (p = 0.05) and a 1.7-fold (p = 0.01) augmentation of protein content in skeletal muscle compared to healthy subjects. In late-stage CHF, exercise training led to a 36% reduction of the mRNA and a 23% decrease of the myostatin protein compared to baseline. The serum concentration of myostatin revealed no significant alteration between the groups. In the skeletal muscle, myostatin increases significantly in the course of CHF. The observed effects of a significant reduction of myostatin in skeletal muscle after 12 weeks of exercise training demonstrate the reversibility of molecular changes that might be able to halt the devastating process of muscle wasting in chronic heart failure.

Minimal important difference for 6-minute walk test distances among patients with chronic heart failure.

PubMed

Täger, Tobias; Hanholz, Wiebke; Cebola, Rita; Fröhlich, Hanna; Franke, Jennifer; Doesch, Andreas; Katus, Hugo A; Wians, Frank H; Frankenstein, Lutz

2014-09-01

The 6-minute walk test (6 WT) is an established tool in the assessment of endurance and prognosis in patients with chronic heart failure (CHF). For these patients there is very limited data on biological variation of 6 WT distances. We determined the minimal important difference (MID) for the 6 WT in patients with stable systolic CHF. Two cohorts of patients with stable systolic CHF were included from the outpatients' clinic of the University of Heidelberg. In these cohorts, two 6 WT measurements were performed - in cohort 1 (n=461) 180 days and in cohort 2 (n=512) 365 days apart. Stability was defined as the absence of clinical events (3 months before the first test, between both tests, and 6 months after the second test) and stability of symptoms (NYHA) between tests. Using a standard error of measurement (SEM)-based approach, we determined the MID for both cohorts. The intraclass correlation coefficient was 0.89 at 180 days and 0.88 at 365 days. The results were consistent for groups stratified for age, gender, etiology of CHF, and individual NYHA class. The MID for the 6 WT in stable CHF patients was 35 m and 37 m between presentation and 180 and 365 days, respectively. Submaximal exercise capacity as represented by the 6 WT varies little in stable CHF patients for up to 1-year intervals. The MID for changes in 6 WT values in patients with stable CHF over a period of 6 to 12 months is ~ 36 m. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

[Matrix metalloproteinases and their inhibitors in lung cancer with malignant pleural effusion].

PubMed

Moche, M; Hui, D S C; Huse, K; Chan, K S; Choy, D K L; Scholz, G H; Gosse, H; Winkler, J; Schauer, J; Sack, U; Hoheisel, G

2005-08-01

Matrix metalloproteinases (MMP) and tissue inhibitors of metalloproteinases (TIMP) play a crucial role in physiological and pathological matrix turnover. This study aimed to determine the occurrence of MMP and TIMP in lung cancer patients with malignant pleural effusions (CA). MMP-1, MMP-2, MMP-3, MMP-8, MMP-9, TIMP-1, and IMP-2 oncentrations were determined by ELISA and zymography in pleural effusions and plasma of 31 CA and 14 congestive heart failure (CHF) patients and in plasma of 18 healthy controls (CON). MMP-2, TIMP-1, and TIMP-2 ELISA-concentrations were increased in CA pleural fluid vs. CA plasma (p < 0.005, p < 0.005, p < 0.05), in contrast to MMP-9 being higher in plasma (p < 0.005). Pleural fluid MMP-1 and MMP-8 were increased in CA vs. CHF (p < 0.05, p < 0.005). MMP and TIMP plasma concentrations were not different in CA vs. CHF, but MMP-9, TIMP-1, and TIMP-2 were increased vs. CON (p < 0.005, each). Gelatine zymography MMP-9/MMP-2 ratios were increased in CA plasma vs. effusion fluid (p < 0.005), in CA vs. CHF plasma, CA vs. CHF effusions (p < 0.005 each), and in CA vs. CON plasma (p < 0.05). MMP-2, TIMP-1, and TIMP-2 accumulate in the pleural compartment in CA and CHF, probably reflecting an unspecific pleural reaction. MMP-1 and MMP-8 are increased in cellular rich CA pleural effusions only. The determination of MMP-9/MMP-2 ratios in pleural fluid may contribute to differentiate CHF from CA effusions.

Patient preferences for the delivery of disease management in chronic heart failure: a qualitative study.

PubMed

Whitty, Jennifer A; Carrington, Melinda J; Stewart, Simon; Holliday, Julie; Marwick, Thomas H; Scuffham, Paul A

2012-01-01

Chronic heart failure (CHF) management programs (CHF-MPs) are applied in different ways including via face-to-face settings. However, we know little about consumer preferences when applying CHF-MPs via a patient's home or specialist hospital clinic. The aim of this pilot study was to explore CHF-MP characteristics that are considered desirable by patients with CHF. Semistructured interviews with a purposive sample of 12 CHF patients. Participants had a mean age of 61 (SD, 17) years, 3 were female, and the majority was of white background. Most were assessed as either functional New York Heart Association class III (n = 3) or IV (n = 6). Home- and clinic-based CHF-MPs were preferred by 5 and 7 participants, respectively. Key themes around patient preferences related to practical aspects of program delivery and social and peer support, as well as health-related benefits that translate to traditional outcomes in program evaluations. Participants identified transport, cost, and ill health as barriers to attending a clinic-based program. However, they also highlighted benefits (eg, the ability to share experiences with other patients) that may be difficult to provide with a home-based service unless specifically organized. These preliminary data suggest that patients value aspects of a program beyond those directly related to health outcomes. They also recognize a need for flexibility in program delivery, with potential preferences for home- or clinic-based programs depending largely on individual patient circumstances. More definitive studies are required to explore how best to cater for individual preferences while optimizing health outcomes.

[Changes of heart-type fatty acid-binding protein in children with chronic heart failure and its significance].

PubMed

Sun, Yu-Ping; Wang, Wen-Di; Ma, Shao-Chun; Wang, Li-Yan; Qiao, Ling-Yan; Zhang, Li-Ping

2013-02-01

To study serum levels of heart-type fatty acid-binding protein (h-FABP) in children with chronic heart failure (CHF), and the correlation between heart function and the level of h-FABP, with the aim of studying the significance of h-FABP in CHF. Thirty-six children with CHF, including 16 cases of endocardial fibroelastosis (EFE) and 20 cases of dilated cardiomyopathy (DCM) were enrolled in the study. Thirty healthy children sevred as the control group. Serum levels of h-FABP were determined using ELISA, and left ventricular ejection fraction (LVEF), cardiac index (CI) and fractional shortening of the left ventricle (LVSF) were measured by two-dimensional echocardiography in the CHF group. Mean levels of h-FABP in the CHF group were significantly higher than in the control group (21.7±4.3 ng/mL vs 6.2±1.7 ng/mL; P<0.01). The worse the heart function, the higher the h-FABP levels (P<0.01). Mean levels of h-FABP in both the EFE and DCM groups were significantly higher than in the control group (P<0.01). Serum h-FABP concentrations were negatively correlated with LVEF, CI and LVSF (r=-0.65, -0.64 and -0.71 respectively; P<0.01) in the CHF group. Serum h-FABP levels increase in children with CHF and are closely related to the severity of the condition. Serum h-FABP levels can be used as a biomarker for the diagnosis of heart failure and the evaluation of its severity.

Improved quality of care for cardiovascular disease for Latinos seen in high proportion Latino vs low proportion Latino clinics.

PubMed

López, Lenny; Cook, Nakela; Hicks, Leroi

2015-01-01

Primary care practices that concentrate linguistically and culturally appropriate services for Latinos may result in higher cardiology consultation rates and improved process measure performance for patients with coronary artery disease (CAD) and congestive heart failure (CHF). Multivariable Cox proportional-hazards regression was used to assess differences in referral at high proportion (HP) vs low proportion (LP) practices. Multivariable Poisson regression was used to assess the frequency of follow-up consultation. Among the 9,761 patients, 9,168 had CAD, 4,444 had CHF, and 3,851 had both conditions. Latinos comprised 11% of the CAD cohort and 11% of the CHF cohort. Multivariable analyses showed higher consultation rates for Latinos at HP practices for CAD and CHF. Blacks and Whites at HP practices had no significant differences in rates of consultation compared to those in LP practices. Latinos at HP practices had 25% more consultations for CAD and 23% more consultations for CHF than Latinos at LP practices. Latinos at HP clinics had higher overall mean quality performance on clinical measures for both CAD and CHF. Latinos at an LP clinic had the largest improvement in quality performance with consultation. Among Latinos with CAD or CHF receiving care within a single large academic care network, Latino patients at HP practices have higher rates of cardiologist consultation and performance on CVD process measures compared to Latino patients at LP practices. Elucidating the essential components of individual practice environments that provide higher quality of care for Latinos will allow for well designed systems to reduce health care disparities.

Risk distribution across multiple health insurance funds in rural Tanzania.

PubMed

Chomi, Eunice Nahyuha; Mujinja, Phares Gamba; Enemark, Ulrika; Hansen, Kristian; Kiwara, Angwara Dennis

2014-01-01

Multiple insurance funds serving different population groups may compromise equity due to differential revenue raising capacity and an unequal distribution of high risk members among the funds. This occurs when the funds exist without mechanisms in place to promote income and risk cross-subsidisation across the funds. This paper analyses whether the risk distribution varies across the Community Health Fund (CHF) and National Health Insurance Fund (NHIF) in two districts in Tanzania. Specifically we aim to 1) identify risk factors associated with increased utilisation of health services and 2) compare the distribution of identified risk factors among the CHF, NHIF and non-member households. Data was collected from a survey of 695 households. A multivariate logisitic regression model was used to identify risk factors for increased health care utilisation. Chi-square tests were performed to test whether the distribution of identified risk factors varied across the CHF, NHIF and non-member households. There was a higher concentration of identified risk factors among CHF households compared to those of the NHIF. Non-member households have a similar wealth status to CHF households, but a lower concentration of identified risk factors. Mechanisms for broader risk spreading and cross-subsidisation across the funds are necessary for the promotion of equity. These include risk equalisation to adjust for differential risk distribution and revenue raising capacity of the funds. Expansion of CHF coverage is equally important, by addressing non-financial barriers to CHF enrolment to encourage wealthy non-members to join, as well as subsidised membership for the poorest.

Patient preferences and willingness-to-pay for a home or clinic based program of chronic heart failure management: findings from the Which? trial.

PubMed

Whitty, Jennifer A; Stewart, Simon; Carrington, Melinda J; Calderone, Alicia; Marwick, Thomas; Horowitz, John D; Krum, Henry; Davidson, Patricia M; Macdonald, Peter S; Reid, Christopher; Scuffham, Paul A

2013-01-01

Beyond examining their overall cost-effectiveness and mechanisms of effect, it is important to understand patient preferences for the delivery of different modes of chronic heart failure management programs (CHF-MPs). We elicited patient preferences around the characteristics and willingness-to-pay (WTP) for a clinic or home-based CHF-MP. A Discrete Choice Experiment was completed by a sub-set of patients (n = 91) enrolled in the WHICH? trial comparing home versus clinic-based CHF-MP. Participants provided 5 choices between hypothetical clinic and home-based programs varying by frequency of nurse consultations, nurse continuity, patient costs, and availability of telephone or education support. Participants (aged 71±13 yrs, 72.5% male, 25.3% NYHA class III/IV) displayed two distinct preference classes. A latent class model of the choice data indicated 56% of participants preferred clinic delivery, access to group CHF education classes, and lower cost programs (p<0.05). The remainder preferred home-based CHF-MPs, monthly rather than weekly visits, and access to a phone advice service (p<0.05). Continuity of nurse contact was consistently important. No significant association was observed between program preference and participant allocation in the parent trial. WTP was estimated from the model and a dichotomous bidding technique. For those preferring clinic, estimated WTP was ≈AU$9-20 per visit; however for those preferring home-based programs, WTP varied widely (AU$15-105). Patient preferences for CHF-MPs were dichotomised between a home-based model which is more likely to suit older patients, those who live alone, and those with a lower household income; and a clinic-based model which is more likely to suit those who are more socially active and wealthier. To optimise the delivery of CHF-MPs, health care services should consider their patients' preferences when designing CHF-MPs.

Prevalence and prognosis of congestive heart failure in Saudi patients admitted with acute coronary syndrome (from SPACE registry).

PubMed

Albackr, Hanan B; Alhabib, Khalid F; Ullah, Anhar; Alfaleh, Hussam; Hersi, Ahmad; Alshaer, Fayez; Alnemer, Khalid; Al Saif, Shukri; Taraben, Amir; Kashour, Tarek

2013-11-01

The aim of this study was to assess the prevalence, clinical features, and in-hospital outcomes of heart failure in patients with acute coronary syndrome (ACS). The Saudi Project for Assessment of Coronary Events recruited patients admitted with ACS from 17 hospitals in Saudi Arabia from 2005 to 2007. The outcomes of ACS patients with congestive heart failure (CHF) compared with those without CHF were analyzed. A total of 4523 patients with ACS were identified, of whom 905 (20%) had CHF. Compared with no CHF, patients with CHF were older (62±13.1 vs. 57±12.9 years; P=0.001), less likely to be men (70 vs. 79%; P=0.001), likely to present with non-ST-segment elevation myocardial infarction (48 vs. 36%; P=0.001), likely to have diabetes (71 vs. 54%; P=0.001), hypertension (64 vs. 54%; P=0.001) and previous history of coronary artery disease (53 vs. 43%; P=0.001), and likely to have significant left ventricular systolic dysfunction (left ventricular ejection fraction <35%) (56 vs. 30%; P=0.001). Patients with CHF were less likely to receive in-hospital β-blockers (74 vs. 86%; P=0.001) and a percutaneous coronary intervention (19 vs. 50%; P=0.001). Adjusted in-hospital mortality and cardiogenic shock were higher in the CHF group (odds ratio 4.43, 95% confidence interval 2.52-7.78; and odds ratio 3.51, 95% confidence interval 2.23-5.52), respectively. ACS patients with CHF in the Saudi Project for Assessment of Coronary Events were older, more likely to have more cardiac risk factors, and less likely to be treated with optimum medical treatment on admission. These findings were associated with higher incidence of their in-hospital adverse outcomes. More aggressive treatment is warranted to improve prognosis.

The association between hospital volume and processes, outcomes, and costs of care for congestive heart failure

PubMed Central

Joynt, Karen E.; Orav, E. John; Jha, Ashish K.

2012-01-01

Background Congestive Heart Failure (CHF) is common and costly, and despite pharmacologic and technical advances, outcomes remain suboptimal. Objective To examine whether hospitals that have more experience caring for patients with CHF provide better, more efficient care. Design We used national Medicare claims data from 2006–2007 to examine the relationship between hospitals’ case volume and quality, outcomes, and costs for patients with CHF. Setting 4,095 U.S. hospitals Patients Medicare fee-for-service patients with a primary discharge diagnosis of CHF Measurements Hospital Quality Alliance (HQA) CHF process measures, 30-day risk-adjusted mortality rates, 30-day risk-adjusted readmission rates, and costs per discharge. Results Hospitals in the lowest volume group had lower performance on HQA measures than medium- or high-volume hospitals (80.2% versus 87.0% versus 89.1%, p<0.001). Within the low volume group, being admitted to a hospital with a higher case volume was associated with lower mortality, lower readmission, and higher costs. For example, in the lowest volume group of hospitals, an increase of 10 cases of CHF was associated with 1% lower odds of mortality, 1% lower odds of readmissions and $22 higher costs per case. We found similar though smaller relationships between case volume and both mortality and costs in the medium and high-volume hospital cohorts. Limitations Our analysis was limited to Medicare patients 65 years of age or older; risk adjustment was performed using administrative data. Conclusions Experience with managing CHF, as measured by an institution’s volume, is associated with higher quality of care and better outcomes for patients, but at a higher cost. Understanding which practices employed by high-volume institutions account for these advantages can help improve quality of care and clinical outcomes for all CHF patients. PMID:21242366

Positive interaction of the β2-agonist CHF 4226.01 with budesonide in the control of bronchoconstriction induced by acetaldehyde in the guinea-pigs

PubMed Central

Rossoni, Giuseppe; Manfredi, Barbara; Razzetti, Roberta; Civelli, Maurizio; Bongrani, Stefano; Berti, Ferruccio

2005-01-01

Pretreatment of anaesthetized guinea-pigs with either CHF 4226.01 (8-hydroxy-5-[(1R)-1-hydroxy-2-[N-[(1R)-2-(p-methoxyphenyl)-1-methylethyl]amino]ethyl] carbostyril hydrochloride), formoterol or budesonide reduced acetaldehyde (AcCHO)-evoked responses in the lungs with a rank order of potency CHF 4226.01 (ED50 values, from 1.88 to 3.31 pmol) > formoterol (ED50 values, from 3.03 to 5.51 pmol) ≫ budesonide (ED50 values, from 335 to 458 nmol). The duration of action of CHF 4226.01 in antagonizing the airway obstruction elicited by AcCHO was also substantially longer than formoterol (area under the curve) at 10 pmol, 763±58 and 480±34, respectively; P<0.01). Continuous infusion of a subthreshold dose of AcCHO enhanced the intratracheal pressure (ITP) increases caused by subsequent challenges with substance P (from 9.7±0.8 to 27.5±1.6 cm H2O as a peak, P<0.001). Pretreatment with either CHF 4226.01 or formoterol prevented the sensitizing effect of AcCHO on substance P responses (ED50 values, 2.85 and 6.11 pmol, respectively; P<0.01). The ED50 value of budesonide (396 nmol) in preventing AcCHO-evoked ITP increase was reduced when this glucocorticoid was combined with 0.1 pmol CHF 4226.01 (ED50 76 nmol; P<0.001). CHF 4226.01/budesonide was two-fold more effective (P<0.01) than the formoterol/budesonide combination. These results suggest that CHF 4226.01/budesonide, by optimizing each other's beneficial potential in the control of pulmonary changes caused by AcCHO in the guinea-pigs, may represent a new fixed combination in asthma. PMID:15655502

Experimental and numerical simulation of dissolution and precipitation: implications for fracture sealing at Yucca Mountain, Nevada

NASA Astrophysics Data System (ADS)

Dobson, Patrick F.; Kneafsey, Timothy J.; Sonnenthal, Eric L.; Spycher, Nicolas; Apps, John A.

2003-05-01

Plugging of flow paths caused by mineral precipitation in fractures above the potential repository at Yucca Mountain, Nevada could reduce the probability of water seeping into the repository. As part of an ongoing effort to evaluate thermal-hydrological-chemical (THC) effects on flow in fractured media, we performed a laboratory experiment and numerical simulations to investigate mineral dissolution and precipitation under anticipated temperature and pressure conditions in the repository. To replicate mineral dissolution by vapor condensate in fractured tuff, water was flowed through crushed Yucca Mountain tuff at 94 °C. The resulting steady-state fluid composition had a total dissolved solids content of about 140 mg/l; silica was the dominant dissolved constituent. A portion of the steady-state mineralized water was flowed into a vertically oriented planar fracture in a block of welded Topopah Spring Tuff that was maintained at 80 °C at the top and 130 °C at the bottom. The fracture began to seal with amorphous silica within 5 days. A 1-D plug-flow numerical model was used to simulate mineral dissolution, and a similar model was developed to simulate the flow of mineralized water through a planar fracture, where boiling conditions led to mineral precipitation. Predicted concentrations of the major dissolved constituents for the tuff dissolution were within a factor of 2 of the measured average steady-state compositions. The mineral precipitation simulations predicted the precipitation of amorphous silica at the base of the boiling front, leading to a greater than 50-fold decrease in fracture permeability in 5 days, consistent with the laboratory experiment. These results help validate the use of a numerical model to simulate THC processes at Yucca Mountain. The experiment and simulations indicated that boiling and concomitant precipitation of amorphous silica could cause significant reductions in fracture porosity and permeability on a local scale. However, differences in fluid flow rates and thermal gradients between the experimental setup and anticipated conditions at Yucca Mountain need to be factored into scaling the results of the dissolution/precipitation experiments and associated simulations to THC models for the potential Yucca Mountain repository.

Controlling the Internal Heat Transfer Coefficient by the Characteristics of External Flows

NASA Astrophysics Data System (ADS)

Zhuromskii, V. M.

2018-01-01

The engineering-physical fundamentals of substance synthesis in a boiling apparatus are presented. We have modeled a system of automatic stabilization of the maximum internal heat transfer coefficient in such an apparatus by the characteristics of external flows on the basis of adaptive seeking algorithms. The results of operation of the system in the shop are presented.

Food waste in the Swiss food service industry - Magnitude and potential for reduction.

PubMed

Betz, Alexandra; Buchli, Jürg; Göbel, Christine; Müller, Claudia

2015-01-01

Food losses occur across the whole food supply chain. They have negative effects on the economy and the environment, and they are not justifiable from an ethical point of view. The food service industry was identified by Beretta et al. (2013) as the third largest source of food waste based on food input at each stage of the value added chain. The total losses are estimated 18% of the food input, the avoidable losses 13.5%. However, these estimations are related with considerable uncertainty. To get more reliable and detailed data of food losses in this sector, the waste from two companies (in the education and business sectors) was classified into four categories (storage losses, preparation losses, serving losses, and plate waste) and seven food classes and measured for a period of five days. A questionnaire evaluated customer reaction, and a material flow analysis was used to describe the mass and monetary losses within the process chain. The study found that in company A (education sector) 10.73% and in company B (business sector) 7.69% of the mass of all food delivered was wasted during the process chain. From this, 91.98% of the waste in company A and 78.14% in company B were classified as avoidable. The highest proportion of waste occurred from serving losses with starch accompaniments and vegetables being the most frequently wasted items. The quantities of waste per meal were 91.23 g (value CHF 0.74) and 85.86 g (value CHF 0.44) for company A and company B, respectively. The annual loss averaged 10.47 tonnes (value CHF 85,047) in company A and 16.55 tonnes (value CHF 85,169) in company B. The customer survey showed that 15.79% (n=356) of the respondents in company A and 18.32% (n=382) in company B produced plate waste. The main causes of plate waste cited were 'portion served by staff too large' and 'lack of hunger'. Sustainable measures need to be implemented in the food service industry to reduce food waste and to improve efficiency. Copyright © 2014 Elsevier Ltd. All rights reserved.

Numerical Simulation of Liquid Nitrogen Chilldown of a Vertical Tube

NASA Technical Reports Server (NTRS)

Darr, Samuel; Hu, Hong; Schaeffer, Reid; Chung, Jacob; Hartwig, Jason; Majumdar, Alok

2015-01-01

This paper presents the results of a one-dimensional numerical simulation of the transient chilldown of a vertical stainless steel tube with liquid nitrogen. The direction of flow is downward (with gravity) through the tube. Heat transfer correlations for film, transition, and nucleate boiling, as well as critical heat flux, rewetting temperature, and the temperature at the onset of nucleate boiling were used to model the convection to the tube wall. Chilldown curves from the simulations were compared with data from 55 recent liquid nitrogen chilldown experiments. With these new correlations the simulation is able to predict the time to rewetting temperature and time to onset of nucleate boiling to within 25% for mass fluxes ranging from 61.2 to 1150 kg/(sq m s), inlet pressures from 175 to 817 kPa, and subcooled inlet temperatures from 0 to 14 K below the saturation temperature.

Cost-effectiveness of roflumilast in combination with bronchodilator therapies in patients with severe and very severe COPD in Switzerland

PubMed Central

Samyshkin, Yevgeniy; Schlunegger, Michael; Haefliger, Susan; Ledderhose, Sabine; Radford, Matthew

2013-01-01

Objective Chronic obstructive pulmonary disease (COPD) represents a burden on patients and health systems. Roflumilast, an oral, selective phosphodiesterase-4-inhibitor reduces exacerbations and improves lung function in severe/very severe COPD patients with a history of exacerbations. This study aimed to estimate the lifetime cost and outcomes of roflumilast added-on to commonly used COPD regimens in Switzerland. Methods A Markov cohort model was developed to simulate COPD progression in patients with disease states of severe, very severe COPD, and death. The exacerbation rate was assumed to be two per year in severe COPD. COPD progression rates were drawn from the published literature. Efficacy was expressed as relative ratios of exacerbation rates associated with roflumilast, derived from a mixed-treatment comparison. A cost-effectiveness analysis was conducted for roflumilast added to long-acting muscarinic antagonists (LAMA), long-acting β2-agonist/ inhaled corticosteroids (LABA/ICS), and LAMA + LABA/ICS. The analysis was conducted from the Swiss payer perspective, with costs and outcomes discounted at 2.5% annually. Parameter uncertainties were explored in one-way and probabilistic sensitivity analyses. Results In each of the comparator regimens mean life expectancy was 9.28 years and quality-adjusted life years (QALYs) gained were 6.19. Mean estimated lifetime costs per patient in the comparator arms were CHF 83,364 (LAMA), CHF 88,161 (LABA/ICS), and CHF 95,564 (LAMA + LABA/ICS) respectively. Adding roflumilast resulted in a mean cost per patient per lifetime of CHF 86,754 (LAMA + roflumilast), CHF 91,470 (LABA/ICS + roflumilast), and CHF 99,364 (LAMA + LABA/ICS + roflumilast), respectively. Life-expectancy and quality-adjusted life-expectancy were 9.63 years and 6.47 QALYs (LAMA + roflumilast), 9.64 years and 6.48 QALYs (LABA/ICS + roflumilast), and 9.63 years and 6.47 QALYs (LAMA + LABA/ ICS + roflumilast). Incremental cost-effectiveness ratios were CHF 12,313, CHF 11,456, and CHF 13,671 per QALY when roflumilast was added to the three regimens. Conclusion Treatment with roflumilast is estimated to reduce the health and economic burden of COPD exacerbations and represent a cost-effective treatment option for patients with frequent exacerbations in Switzerland. PMID:23386787

Interaction of cold-water aquifers with exploited reservoirs of the Cerro Prieto geothermal system

USGS Publications Warehouse

Truesdell, Alfred; Lippmann, Marcelo

1990-01-01

Cerro Prieto geothermal reservoirs tend to exhibit good hydraulic communication with adjacent cool groundwater aquifers. Under natural state conditions the hot fluids mix with the surrounding colder waters along the margins of the geothermal system, or discharge to shallow levels by flowing up fault L. In response to exploitation reservoir pressures decrease, leading to changes in the fluid flow pattern in the system and to groundwater influx. The various Cerro Prieto reservoirs have responded differently to production, showing localized near-well or generalized boiling, depending on their access to cool-water recharge. Significant cooling by dilution with groundwater has only been observed in wells located near the edges of the field. In general, entry of cool water at Cerro Prieto is beneficial because it tends to maintain reservoir pressures, restrict boiling, and lengthen the life and productivity of wells.

Experimental study on flow boiling heat transfer of LNG in a vertical smooth tube

NASA Astrophysics Data System (ADS)

Chen, Dongsheng; Shi, Yumei

2013-10-01

An experimental apparatus is set up in this work to study the upward flow boiling heat transfer characteristics of LNG (liquefied natural gas) in vertical smooth tubes with inner diameters of 8 mm and 14 mm. The experiments were performed at various inlet pressures from 0.3 to 0.7 MPa. The results were obtained over the mass flux range from 16 to 200 kg m-2 s-1 and heat fluxes ranging from 8.0 to 32 kW m-2. The influences of quality, heat flux and mass flux, tube diameter on the heat transfer characteristic are examined and discussed. The comparisons of the experimental heat transfer coefficients with the predicted values from the existing correlations are analyzed. The correlation by Zou et al. [16] shows the best accuracy with the RMS deviation of 31.7% in comparison with the experimental data.

Italian Survey on Prevalence and Disease Management of Chronic Heart Failure and Chronic Obstructive Pulmonary Disease comorbidity in ambulatory patients. SUSPIRIUM study rationale and design.

PubMed

Griffo, Raffaele; Spanevello, Antonio; Temporelli, Pier Luigi; Faggiano, Pompilio; Carones, Mauro; Magni, Giovanna; Ambrosino, Nicolino; Tavazzi, Luigi

2014-03-01

Chronic heart failure (CHF) and chronic obstructive pulmonary disease (COPD) are leading causes of morbidity and mortality worldwide. Through shared risk factors and pathophysiological mechanisms, CHF and COPD frequently coexist. The concurrent disease has important therapeutic implications and independently predicts worsened mortality, impaired functional status, and health service use. However, assessment of the comorbidity varies widely according to the population studied, diagnostic criteria and measurement tools applied. Both syndromes have been studied extensively but largely separately, mostly in the domain of the pulmonologist for COPD and in the domain of the cardiologist for CHF. The aim of the study is to evaluate in an Italian outpatients setting (10 cardiology and 10 pulmonology centers from the same institution) the prevalence, clinical profile and the routine diagnostic, functional and therapeutic work-up applied by cardiologists and pulmonologists in the presence/suspicion of concurrent disease in patients in a stable phase of their disease. For this purpose, CHF and COPU outpatients will be enrolled in a multicenter, nationwide, prospective observational study. Risk estimation of comorbidity will be based on suspected, documented or patient-reported diagnosis of COPD/CHF. In the absence of documented concurrent diagnosis, each specialist will describe the diagnostic, functional and therapeutic work-up applied. The design of the study focused on the diagnostic validation of the CHF-COPD comorbidity aims to provide relevant new information on the assessment of the coexistent condition in the cardiac and pulmonary outpatients setting and on specialty-related different diagnostic and therapeutic strategies of comorbidity utilized in real life clinical practice. The symptomatic and prognostic benefits resulting from a combined approach to CHF/COPD could outweigh those attainable by treating either condition alone.

Examination of the Effect of Implantable Cardioverter-Defibrillators on Health-Related Quality of Life

PubMed Central

Noyes, Katia; Corona, Ethan; Veazie, Peter; Dick, Andrew W.; Zhao, Hongwei; Moss, Arthur J.

2015-01-01

Background While implantable cardioverter-defibrillators (ICDs) improve survival, their benefit in terms of health-related quality of life (HRQOL) is negligible. Objective To examine how shocks and congestive heart failure (CHF) mediate the effect of ICDs on HRQOL. Methods The US patients from the MADIT-II (Multicenter Automatic Defibrillator Trial-II) trial (n = 983) were randomized to receive an ICD or medical treatment only. HRQOL was assessed using the Health Utility Index 3 at baseline and 3, 12, 24, and 36 months following randomization. Logistic regressions were used to test for the effect of ICDs on the CHF indicator, and linear regressions were used to examine the effect of ICD shocks and CHF on HRQOL in living patients. We used a Monte Carlo simulation and a parametric Weibull distribution survival model to test for the effect of selective attrition. Observations were clustered by patients and robust standard errors (RSEs) were used to control for the non-independence of multiple observations provided by the same patient. Results Patients in the ICD arm had 41% higher odds of experiencing CHF since their last assessment compared with those in the control arm (RSE = 0.19, p = 0.01). Developing CHF reduced HRQOL at the subsequent visit by 0.07 (p < 0.01). Having ICD shocks reduced overall HRQOL by 0.04 (p = 0.04) at the subsequent assessment. The negative effect of ICD firing on HRQOL was an order of magnitude greater than the effect of CHF. Conclusions A higher prevalence of CHF and shocks among patients with ICDs and their negative effect on HRQOL may partially explain the lack of HRQOL benefit of ICD therapy. PMID:19929037

Central command dysfunction in rats with heart failure is mediated by brain oxidative stress and normalized by exercise training.

PubMed

Koba, Satoshi; Hisatome, Ichiro; Watanabe, Tatsuo

2014-09-01

Sympathoexcitation elicited by central command, a parallel activation of the motor and autonomic neural circuits in the brain, has been shown to become exaggerated in chronic heart failure (CHF). The present study tested the hypotheses that oxidative stress in the medulla in CHF plays a role in exaggerating central command-elicited sympathoexcitation, and that exercise training in CHF suppresses central command-elicited sympathoexcitation through its antioxidant effects in the medulla. In decerebrate rats, central command was activated by electrically stimulating the mesencephalic locomotor region (MLR) after neuromuscular blockade. The MLR stimulation at a current intensity greater than locomotion threshold in rats with CHF after myocardial infarction (MI) evoked larger (P < 0.05) increases in renal sympathetic nerve activity and arterial pressure than in sham-operated healthy rats (Sham) and rats with CHF that had completed longterm (8–12 weeks) exercise training (MI + TR). In the Sham and MI + TR rats, bilateral microinjection of a superoxide dismutase (SOD) mimetic Tempol into the rostral ventrolateral medulla (RVLM) had no effects on MLR stimulation-elicited responses. By contrast, in MI rats, Tempol treatment significantly reduced MLR stimulation-elicited responses. In a subset of MI rats, treatment with Tiron, another SOD mimetic, within the RVLM also reduced responses. Superoxide generation in the RVLM, as evaluated by dihydroethidium staining, was enhanced in MI rats compared with that in Sham and MI + TR rats. Collectively, these results support the study hypotheses. We suggest that oxidative stress in the medulla in CHF mediates central command dysfunction, and that exercise training in CHF is capable of normalizing central command dysfunction through its antioxidant effects in the medulla.

Free triiodothyronine levels and short-term prognosis in chronic heart failure patients with type 2 diabetes.

PubMed

Chen, Pingan; Li, Shaonan; Lei, Xiaoming; Liu, Zhen; Wu, Daihong; Luo, Yi; Xu, Dingli

2015-08-01

In chronic heart failure (CHF) patients with type 2 diabetes mellitus (T2DM), the role of thyroid hormone (TH) in predicting CHF severity and prognosis is unclear. The authors therefore investigated the role of TH in predicting CHF severity and prognosis in these specific patients. A total of 224 CHF patients (114 with T2DM) over a mean follow-up time of 6.56 ± 0.18 months were studied. TH, N-terminal pro-B-type natriuretic peptide (NT-proBNP) and other parameters were measured. Free triiodothyronine (FT3) levels were lower in the T2DM group compared with the nondiabetes group (P = 0.026) and higher in the New York Heart Association (NYHA) I group than in the NYHA III and IV groups (both P < 0.05). Compared with the low NT-proBNP group, the high NT-proBNP group had lower FT3 levels (P < 0.01). NT-proBNP correlated with NYHA classes (r = 0.541, P < 0.001), and inversely correlated with left ventricular ejection fraction (r = -0.431, P < 0.001) and FT3 levels (r = -0.335, P < 0.001). In multiple linear regression analysis, NT-proBNP was significantly correlated with NYHA classes (P < 0.001), left ventricular ejection fraction (P < 0.001) and FT3 (P = 0.004). Kaplan-Meier curves showed that the low FT3 group had an increased rate of short-term adverse outcomes of CHF (log rank, χ = 9.794, P = 0.002). FT3 levels are associated with the severity of CHF and seem to reflect short-term outcomes in CHF patients with T2DM.

Cognitive Dysfunction and Malnutrition Are Independent Predictor of Dysphagia in Patients with Acute Exacerbation of Congestive Heart Failure

PubMed Central

Yamanaka, Shinsuke; Takahashi, Yoshimi; Fujita, Hiroshi; Yamaguchi, Nobuhiro; Onoue, Noriko; Ishizuka, Takeshi; Shinozaki, Tsuyoshi; Kohzuki, Masahiro

2016-01-01

Early detection and intervention for dysphagia is important in patients with congestive heart failure (CHF). However, previous studies have focused on how many patients with dysphagia develop CHF. Studies focusing on the comorbidity of dysphagia in patients with CHF are rare. Additionally, risk factors for dysphagia in patients with CHF are unclear. Thus, the aim of this study was to clarify risk factors for dysphagia in patients with acute exacerbation of CHF. A total of 105 patients, who were admitted with acute exacerbation of CHF, were enrolled. Clinical interviews, blood chemistry analysis, electrocardiography, echocardiography, Mini-Mental State Examination (MMSE), exercise tolerance tests, phonatory function tests, and evaluation of activities of daily living (ADL) and nutrition were conducted on admission. After attending physicians permitted the drinking of water, swallowing screening tests were performed. Patients were divided into a dysphagia group (DG) or a non-dysphagia group (non-DG) based on Functional Oral Intake Scale level. Among the 105 patients, 38 had dysphagia. A greater number of patients had history of aspiration pneumonia and dementia, and there was a higher age, N-terminal pro-B-type natriuretic peptide level in the DG compared with the non-DG. MMSE scores, exercise tolerance, phonatory function, status of ADL, nutrition, albumin, and transthyretin were lower in the DG compared with the non-DG. In multivariate analysis, after adjusting for age and sex, MMSE, BI score, and transthyretin was independently associated with dysphagia. Comorbidity of dysphagia was 36.1% in patients with acute exacerbation of CHF, and cognitive dysfunction and malnutrition may be an independent predictor of dysphagia. PMID:27898735

Cognitive Dysfunction and Malnutrition Are Independent Predictor of Dysphagia in Patients with Acute Exacerbation of Congestive Heart Failure.

PubMed

Yokota, Junichi; Ogawa, Yoshiko; Yamanaka, Shinsuke; Takahashi, Yoshimi; Fujita, Hiroshi; Yamaguchi, Nobuhiro; Onoue, Noriko; Ishizuka, Takeshi; Shinozaki, Tsuyoshi; Kohzuki, Masahiro

2016-01-01

Early detection and intervention for dysphagia is important in patients with congestive heart failure (CHF). However, previous studies have focused on how many patients with dysphagia develop CHF. Studies focusing on the comorbidity of dysphagia in patients with CHF are rare. Additionally, risk factors for dysphagia in patients with CHF are unclear. Thus, the aim of this study was to clarify risk factors for dysphagia in patients with acute exacerbation of CHF. A total of 105 patients, who were admitted with acute exacerbation of CHF, were enrolled. Clinical interviews, blood chemistry analysis, electrocardiography, echocardiography, Mini-Mental State Examination (MMSE), exercise tolerance tests, phonatory function tests, and evaluation of activities of daily living (ADL) and nutrition were conducted on admission. After attending physicians permitted the drinking of water, swallowing screening tests were performed. Patients were divided into a dysphagia group (DG) or a non-dysphagia group (non-DG) based on Functional Oral Intake Scale level. Among the 105 patients, 38 had dysphagia. A greater number of patients had history of aspiration pneumonia and dementia, and there was a higher age, N-terminal pro-B-type natriuretic peptide level in the DG compared with the non-DG. MMSE scores, exercise tolerance, phonatory function, status of ADL, nutrition, albumin, and transthyretin were lower in the DG compared with the non-DG. In multivariate analysis, after adjusting for age and sex, MMSE, BI score, and transthyretin was independently associated with dysphagia. Comorbidity of dysphagia was 36.1% in patients with acute exacerbation of CHF, and cognitive dysfunction and malnutrition may be an independent predictor of dysphagia.

Prognostic value of plasma midregional pro-adrenomedullin and C-terminal-pro-endothelin-1 in chronic heart failure outpatients.

PubMed

Adlbrecht, Christopher; Hülsmann, Martin; Strunk, Guido; Berger, Rudolf; Mörtl, Deddo; Struck, Joachim; Morgenthaler, Nils G; Bergmann, Andreas; Jakowitsch, Johannes; Maurer, Gerald; Lang, Irene M; Pacher, Richard

2009-04-01

The identification of chronic heart failure (CHF) patients at high risk of adverse outcome remains a challenge. New peptides are emerging that may give additional information. In CHF patients, endothelin (ET) levels predict mortality risk. Adrenomedullin has been shown to predict mortality in ischaemic heart failure, but not in unselected or non-ischaemic CHF patients. Moreover, ADM and ET have never been assessed in one model. The aim of the present study was to assess the prognostic value of midregional-pro-adrenomedullin (MR-proADM) and C-terminal-pro-endothelin-1 (CT-proET-1) in outpatients with CHF. We measured plasma MR-proADM and CT-proET-1 levels in 786 consecutive CHF outpatients and compared them with B-type natriuretic peptide (BNP) levels. At 24-month follow-up, 233 patients had died. A stepwise forward Cox regression model with age, sex, estimated glomerular filtration rate, NYHA > II, left ventricular ejection fraction (LVEF), MR-proADM, CT-proET-1, and BNP as possible predictors revealed that MR-proADM levels [hazard ratio (HR) = 1.77, P < 0.001] in addition to age (HR = 1.02, P = 0.004), ejection fraction (HR = 0.98, P = 0.004), and NYHA > II (HR = 1.86, P < 0.001) were predictors of death at 24 months. When the analysis was repeated dependent on NYHA-stage, MR-proADM (HR = 2.12, P < 0.001) and LVEF (HR = 0.96, P = 0.006) were significant markers, but only in patients with mild/moderate CHF. Our data suggest that MR-proADM may be an important prognostic humoral marker, especially in mild/moderately symptomatic and non-ischaemic CHF patients.

The PDE4 inhibitor CHF-6001 and LAMAs inhibit bronchoconstriction-induced remodeling in lung slices.

PubMed

Kistemaker, Loes E M; Oenema, Tjitske A; Baarsma, Hoeke A; Bos, I Sophie T; Schmidt, Martina; Facchinetti, Fabrizio; Civelli, Maurizio; Villetti, Gino; Gosens, Reinoud

2017-09-01

Combination therapy of PDE4 inhibitors and anticholinergics induces bronchoprotection in COPD. Mechanical forces that arise during bronchoconstriction may contribute to airway remodeling. Therefore, we investigated the impact of PDE4 inhibitors and anticholinergics on bronchoconstriction-induced remodeling. Because of the different mechanism of action of PDE4 inhibitors and anticholinergics, we hypothesized functional interactions of these two drug classes. Guinea pig precision-cut lung slices were preincubated with the PDE4 inhibitors CHF-6001 or roflumilast and/or the anticholinergics tiotropium or glycopyorrolate, followed by stimulation with methacholine (10 μM) or TGF-β 1 (2 ng/ml) for 48 h. The inhibitory effects on airway smooth muscle remodeling, airway contraction, and TGF-β release were investigated. Methacholine-induced protein expression of smooth muscle-myosin was fully inhibited by CHF-6001 (0.3-100 nM), whereas roflumilast (1 µM) had smaller effects. Tiotropium and glycopyrrolate fully inhibited methacholine-induced airway remodeling (0.1-30 nM). The combination of CHF-6001 and tiotropium or glycopyrrolate, in concentrations partially effective by themselves, fully inhibited methacholine-induced remodeling in combination. CHF-6001 did not affect airway closure and had limited effects on TGF-β 1 -induced remodeling, but rather, it inhibited methacholine-induced TGF-β release. The PDE4 inhibitor CHF-6001, and to a lesser extent roflumilast, and the LAMAs tiotropium and glycopyrrolate inhibit bronchoconstriction-induced remodeling. The combination of CHF-6001 and anticholinergics was more effective than the individual compounds. This cooperativity might be explained by the distinct mechanisms of action inhibiting TGF-β release and bronchoconstriction. Copyright © 2017 the American Physiological Society.

A geochemical model of the Platanares geothermal system, Honduras

USGS Publications Warehouse

Janik, C.J.; Truesdell, A.H.; Goff, F.; Shevenell, L.; Stallard, M.L.; Trujillo, P.E.; Counce, D.

1991-01-01

Results of exploration drilling combined with results of geologic, geophysical, and hydrogeochemical investigations have been used to construct a geochemical model of the Platanares geothermal system, Honduras. Three coreholes were drilled, two of which produced fluids from fractured Miocene andesite and altered Cretaceous to Eocene conglomerate at 450 to 680 m depth. Large volume artesian flows of 160-165??C, predominantly bicarbonate water are chemically similar to, but slightly less saline than widespread boiling hot-spring waters. The chemistry of the produced fluid is dominated by equilibrium reactions in sedimentary rocks at greater depths and higher temperatures than those measured in the wells. Chemical, isotope, and gas geothermometers indicate a deep fluid temperature of 200-245??C and reflect a relatively short residence time in the fractures feeding the wells. Chloride-enthalpy relations as well as isotopic and chemical compositions of well discharges, thermal springs, and local cold waters support a conceptual model of ascending high-temperature (minimum 225??C) parent fluid that has cooled conductively to form the 160-165??C shallow (to 680 m) fluid encountered by the wells. The hot-spring waters are formed by boiling and steam loss from more or less conductively cooled parent fluid. The more dilute boiling spring waters (Cl = ???32 mg/kg) have cooled from > 225??C to about 160??C by conduction and from 160??C to 98??C by boiling. The most concentrated boiling spring waters (Cl = 37 mg/kg) have cooled from > 225??C to about 200??C by conduction and from 200??C to 98??C by boiling. Intermediate concentrations reflect mixed cooling paths. ?? 1991.

Obesity and chronic kidney disease in patients with chronic heart failure: an insight from the China Heart Survey.

PubMed

Liu, Hao; Shi, Hong; Yu, Jinming; Chen, Fang; Jiang, Qingwu; Hu, Dayi

2011-08-01

Obesity and decreased kidney function have been shown to be prevalent in Western patients with heart failure; however, whether this phenomenon exists in Chinese patients with chronic heart failure (CHF) is not known. One thousand and nine patients with CHF from the China Heart Survey were assessed. The prevalence of chronic kidney disease (CKD) was 34.2%, and there was a stepwise increase in the prevalence of CKD with New York Heart Association (NYHA) classes (P < 0.001). Moreover, patients with CKD had a significantly elevated risk for developing severe extent of CHF (OR = 1.69, 95% CI: 1.27-2.24, P < 0.001). The prevalence of obesity and central obesity was 35.7% and 62.5%, respectively. Notably, there was a downward trend in the prevalence of obesity with advanced NYHA classes (trend test, P = 0.003). Multivariate analysis further supported the finding that obesity, but not central obesity, was inversely associated with the extent of CHF (OR = 0.72, 95% CI: 0.55-0.94, P = 0.017). Renal dysfunction is common in Chinese patients with CHF and is independently associated with advanced NYHA classes. Obesity was inversely associated with the extent of CHF, which further supports the notion that obesity confers improved prognosis in patients with heart failure.

Single-bubble dynamics in pool boiling of one-component fluids.

PubMed

Xu, Xinpeng; Qian, Tiezheng

2014-06-01

We numerically investigate the pool boiling of one-component fluids with a focus on the effects of surface wettability on the single-bubble dynamics. We employed the dynamic van der Waals theory [Phys. Rev. E 75, 036304 (2007)], a diffuse-interface model for liquid-vapor flows involving liquid-vapor transition in nonuniform temperature fields. We first perform simulations for bubbles on homogeneous surfaces. We find that an increase in either the contact angle or the surface superheating can enhance the bubble spreading over the heating surface and increase the bubble departure diameter as well and therefore facilitate the transition into film boiling. We then examine the dynamics of bubbles on patterned surfaces, which incorporate the advantages of both hydrophobic and hydrophilic surfaces. The central hydrophobic region increases the thermodynamic probability of bubble nucleation while the surrounding hydrophilic region hinders the continuous bubble spreading by pinning the contact line at the hydrophobic-hydrophilic intersection. This leads to a small bubble departure diameter and therefore prevents the transition from nucleate boiling into film boiling. With the bubble nucleation probability increased and the bubble departure facilitated, the efficiency of heat transfer on such patterned surfaces is highly enhanced, as observed experimentally [Int. J. Heat Mass Transfer 57, 733 (2013)]. In addition, the stick-slip motion of contact line on patterned surfaces is demonstrated in one-component fluids, with the effect weakened by surface superheating.

Self Managing Heart Failure in Remote Australia - Translating Concepts into Clinical Practice

PubMed Central

Iyngkaran, Pupalan; Toukhsati, Samia R.; Harris, Melanie; Connors, Christine; Kangaharan, Nadarajan; Ilton, Marcus; Nagel, Tricia; Moser, Debra K.; Battersby, Malcolm

2016-01-01

Congestive heart failure (CHF) is an ambulatory health care condition characterized by episodes of decompensation and is usually without cure. It is a leading cause for morbidity and mortality and the lead cause for hospital admissions in older patients in the developed world. The long-term requirement for medical care and pharmaceuticals contributes to significant health care costs. CHF management follows a hierarchy from physician prescription to allied health, predominately nurse-led, delivery of care. Health services are easier to access in urban compared to rural settings. The differentials for more specialized services could be even greater. Remote Australia is thus faced with unique challenges in delivering CHF best practice. Chronic disease self-management programs (CDSMP) were designed to increase patient participation in their health and alleviate stress on health systems. There have been CDSMP successes with some diseases, although challenges still exist for CHF. These challenges are amplified in remote Australia due to geographic and demographic factors, increased burden of disease, and higher incidence of comorbidities. In this review we explore CDSMP for CHF and the challenges for our region. PMID:27397492

The Indian Consensus Document on cardiac biomarker.

PubMed

Satyamurthy, I; Dalal, Jamshed J; Sawhney, J P S; Mohan, J C; Chogle, Shubha A; Desai, Nagaraj; Sathe, Shireesh P; Maisel, Alan S

2014-01-01

Despite recent advances, the diagnosis and management of heart failure evades the clinicians. The etiology of congestive heart failure (CHF) in the Indian scenario comprises of coronary artery disease, diabetes mellitus and hypertension. With better insights into the pathophysiology of CHF, biomarkers have evolved rapidly and received diagnostic and prognostic value. In CHF biomarkers prove as measures of the extent of pathophysiological derangement; examples include biomarkers of myocyte necrosis, myocardial remodeling, neurohormonal activation, etc. In CHF biomarkers act as indicators for the presence, degree of severity and prognosis of the disease, they may be employed in combination with the present conventional clinical assessments. These make the biomarkers feasible options against the present expensive measurements and may provide clinical benefits. Copyright © 2014 Cardiological Society of India. Published by Elsevier B.V. All rights reserved.

Heart Failure in Minority Populations - Impediments to Optimal Treatment in Australian Aborigines

PubMed Central

Iyngkaran, Pupalan; Kangaharan, Nadarajan; Zimmet, Hendrik; Arstall, Margaret; Minson, Rob; Thomas, Merlin C.; Bergin, Peter; Atherton, John; MacDonald, Peter; Hare, David L.; Horowitz, John D.; Ilton, Marcus

2016-01-01

Chronic heart failure (CHF) among Aboriginal/Indigenous Australians is endemic. There are also grave concerns for outcomes once acquired. This point is compounded by a lack of prospective and objective studies to plan care. To capture the essence of the presented topic it is essential to broadly understand Indigenous health. Key words such as ‘worsening’, ‘gaps’, ‘need to do more’, ‘poorly studied’, or ‘future studies should inform’ occur frequently in contrast to CHF research for almost all other groups. This narrative styled opinion piece attempts to discuss future directions for CHF care for Indigenous Australians. We provide a synopsis of the problem, highlight the treatment gaps, and define the impediments that present hurdles in optimising CHF care for Indigenous Australians. PMID:27280307

Forced Convection Boiling and Critical Heat Flux of Ethanol in Electrically Heated Tube Tests

NASA Technical Reports Server (NTRS)

Meyer, Michael L.; Linne, Diane L.; Rousar, Donald C.

1998-01-01

Electrically heated tube tests were conducted to characterize the critical heat flux (transition from nucleate to film boiling) of subcritical ethanol flowing at conditions relevant to the design of a regeneratively cooled rocket engine thrust chamber. The coolant was SDA-3C alcohol (95% ethyl alcohol, 5% isopropyl alcohol by weight), and tests were conducted over the following ranges of conditions: pressure from 144 to 703 psia, flow velocities from 9.7 to 77 ft/s, coolant subcooling from 33 to 362 F, and critical heat fluxes up to 8.7 BTU/in(exp 2)/sec. For the data taken near 200 psia, critical heat flux was correlated as a function of the product of velocity and fluid subcooling to within +/- 20%. For data taken at higher pressures, an additional pressure term is needed to correlate the critical heat flux. It was also shown that at the higher test pressures and/or flow rates, exceeding the critical heat flux did not result in wall burnout. This result may significantly increase the engine heat flux design envelope for higher pressure conditions.

Quantifying the evolution of flow boiling bubbles by statistical testing and image analysis: toward a general model.

PubMed

Xiao, Qingtai; Xu, Jianxin; Wang, Hua

2016-08-16

A new index, the estimate of the error variance, which can be used to quantify the evolution of the flow patterns when multiphase components or tracers are difficultly distinguishable, was proposed. The homogeneity degree of the luminance space distribution behind the viewing windows in the direct contact boiling heat transfer process was explored. With image analysis and a linear statistical model, the F-test of the statistical analysis was used to test whether the light was uniform, and a non-linear method was used to determine the direction and position of a fixed source light. The experimental results showed that the inflection point of the new index was approximately equal to the mixing time. The new index has been popularized and applied to a multiphase macro mixing process by top blowing in a stirred tank. Moreover, a general quantifying model was introduced for demonstrating the relationship between the flow patterns of the bubble swarms and heat transfer. The results can be applied to investigate other mixing processes that are very difficult to recognize the target.

Quantifying the evolution of flow boiling bubbles by statistical testing and image analysis: toward a general model

PubMed Central

Xiao, Qingtai; Xu, Jianxin; Wang, Hua

2016-01-01

A new index, the estimate of the error variance, which can be used to quantify the evolution of the flow patterns when multiphase components or tracers are difficultly distinguishable, was proposed. The homogeneity degree of the luminance space distribution behind the viewing windows in the direct contact boiling heat transfer process was explored. With image analysis and a linear statistical model, the F-test of the statistical analysis was used to test whether the light was uniform, and a non-linear method was used to determine the direction and position of a fixed source light. The experimental results showed that the inflection point of the new index was approximately equal to the mixing time. The new index has been popularized and applied to a multiphase macro mixing process by top blowing in a stirred tank. Moreover, a general quantifying model was introduced for demonstrating the relationship between the flow patterns of the bubble swarms and heat transfer. The results can be applied to investigate other mixing processes that are very difficult to recognize the target. PMID:27527065

Wall Area of Influence and Growing Wall Heat Transfer due to Sliding Bubbles in Subcooled Boiling Flow

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yoo, Junsoo; Estrada-Perez, Carlos E.; Hassan, Yassin A.

A variety of dynamical features of sliding bubbles and their impact on wall heat transfer were observed at subcooled flow boiling conditions in a vertical square test channel. Among the wide range of parameters observed, we particularly focus in this paper on (i) the sliding bubbles’ effect on wall heat transfer (supplemantry discussion to the authors’ previous work in Yoo et al. (2016a,b)) and (ii) the wall area influenced by sliding bubbles in subcooled boiling flow. At first, this study reveals that the degree of wall heat transfer improvement due to sliding bubbles depended less on the wall superheat conditionmore » as the mass flux increased. Also, the sliding bubble trajectory was found to be one of the critical factors in order to properly describe the wall heat transfer associated with sliding bubbles. In particular, the wall area influenced by sliding bubbles depended strongly on both sliding bubble trajectory and sliding bubble size; the sliding bubble trajectory was also observed to be closely related to the sliding bubble size. Importantly, these results indicate the limitation of current approach in CFD analyses especially for the wall area of bubble influence. In addition, the analyses on the temporal fraction of bubbles’ residence (FR) along the heated wall show that the sliding bubbles typically travel through narrow path with high frequency while the opposite was observed downstream. That is, both FR and sliding bubble trajectory depended substantially on the distance from nucleation site, which is expected to be similar for the quenching heat transfer mode induced by sliding bubbles.« less

Use of the short form 36 in a primary care based disease management program for patients with congestive heart failure.

PubMed

Sidorov, Jaan; Shull, Robert D; Girolami, Sabrina; Mensch, Debra

2003-01-01

While disease management has been described as an important strategy for the care of patients with congestive heart failure (CHF) in the managed care setting, little is known about the impact of this approach on overall health-related quality of life. In this study the Short Form 36 (SF-36) was administered to all patients entering CHF disease management at the time of program entry and at 1 year following entry. Scores on the eight subscales and the two composite scales were calculated and compared before and after. Patients were enrolled from a mixed-model health maintenance organization (HMO) with 34,740 Medicare + Choice enrollees residing in 38 counties in central and northeastern Pennsylvania. Two hundred sixty-eight continuously enrolled patients in an HMO-sponsored CHF disease state management program with completed baseline and follow-up SF-36 surveys were sampled. All patients entered into disease management received primary care based, nurse-directed education about CHF self-management including instruction on etiology of CHF, the importance of medication compliance, home care services if indicated, monitoring weight gain, increased understanding of the warning signs of worsening CHF, and coaching on strategies to contact a physician in a timely manner when CHF worsens. Nurses also facilitated for CHF guidelines among primary care physicians, including the need to obtain a baseline assessment of cardiac function, prescribe angiotensin I-converting enzyme (ACE) inhibitors and beta blockers when appropriate, and initiated appropriate specialist referral. Compared with enrollees who did not complete a pair of SF-36 surveys, the 268 respondents were younger and had a significantly higher rate of cardiac imaging as well as use of ACE inhibitors and beta blocker medications. Analysis of the SF-36 data revealed that three of the eight (Role Physical, General Health Perceptions, and Role Emotional) subscales increased in a statistically significant manner, as did the Mental Health Composite Score. No statistically significant declines in SF-36 scores were observed. Despite limitations to our study, we found disease management for patients with CHF can be associated with significant improvements in quality of life as measured by the SF-36. Compared with nonrespondents, respondents had a higher prevalence of cardiac imaging, ACE inhibitor use, and beta blocker medication use. Our findings are also limited by a lack of a control group with the possibility that the improvements we observed were unrelated to the disease management intervention. However, our findings and success with the use of this tool indicate the SF-36 can be an important part of the ongoing assessment of patients in a disease management program for CHF.

Entropy generation analysis for film boiling: A simple model of quenching

NASA Astrophysics Data System (ADS)

Lotfi, Ali; Lakzian, Esmail

2016-04-01

In this paper, quenching in high-temperature materials processing is modeled as a superheated isothermal flat plate. In these phenomena, a liquid flows over the highly superheated surfaces for cooling. So the surface and the liquid are separated by the vapor layer that is formed because of the liquid which is in contact with the superheated surface. This is named forced film boiling. As an objective, the distribution of the entropy generation in the laminar forced film boiling is obtained by similarity solution for the first time in the quenching processes. The PDE governing differential equations of the laminar film boiling including continuity, momentum, and energy are reduced to ODE ones, and a dimensionless equation for entropy generation inside the liquid boundary and vapor layer is obtained. Then the ODEs are solved by applying the 4th-order Runge-Kutta method with a shooting procedure. Moreover, the Bejan number is used as a design criterion parameter for a qualitative study about the rate of cooling and the effects of plate speed are studied in the quenching processes. It is observed that for high speed of the plate the rate of cooling (heat transfer) is more.

Increasing Boiling Heat Transfer using Low Conductivity Materials

PubMed Central

Mahamudur Rahman, Md; Pollack, Jordan; McCarthy, Matthew

2015-01-01

We report the counterintuitive mechanism of increasing boiling heat transfer by incorporating low-conductivity materials at the interface between the surface and fluid. By embedding an array of non-conductive lines into a high-conductivity substrate, in-plane variations in the local surface temperature are created. During boiling the surface temperature varies spatially across the substrate, alternating between high and low values, and promotes the organization of distinct liquid and vapor flows. By systematically tuning the peak-to-peak wavelength of this spatial temperature variation, a resonance-like effect is seen at a value equal to the capillary length of the fluid. Replacing ~18% of the surface with a non-conductive epoxy results in a greater than 5x increase in heat transfer rate at a given superheat temperature. This drastic and counterintuitive increase is shown to be due to optimized bubble dynamics, where ordered pathways allow for efficient removal of vapor and the return of replenishing liquid. The use of engineered thermal gradients represents a potentially disruptive approach to create high-efficiency and high-heat-flux boiling surfaces which are naturally insensitive to fouling and degradation as compared to other approaches. PMID:26281890

Inflammatory mediators in chronic heart failure in North India.

PubMed

Fedacko, Jan; Singh, Ram B; Gupta, Aditya; Hristova, Krasimira; Toda, Eri; Kumar, Adarsh; Saxena, Manoj; Baby, Anjum; Singh, Ranjana; Toru, Takahashi; Wilson, Douglas W

2014-08-01

Recent evidence shows that pro-inflammatory cytokines may be important in the assessment of severity and prognosis in congestive heart failure (CHF). In the present study, we examine the association of cytokines with causes, grade and prognosis of CHF patients. Of 127 patients with CHF, 11 were excluded and the remaining 116 patients with different aetiologies of CHF, and 250 age- and sex-matched control subjects, were evaluated in this case study. Severity of disease based on the New York Heart Association (NYHA) standards, fell within functional classes II to IV. The diagnosis of HF was based on clinical manifestations as well as on echocardiographic heart enlargement. Cytokines were measured by chemiluminescence. Causes of death were assessed based on death certificates. Multivariate logistic regression analysis was used to determine the risk factors of heart failure. Echocardiographic ejection fraction was 39.1 +/- 8.2% (mean +/- SD) in the study group indicating class II-IV heart failure. Laboratory data showed increase in biomarkers of oxidative stress, among HF patients compared to healthy subjects. Pro-inflammatory cytokines; IL-6 and TNF-alpha were significantly higher among HF patients compared to healthy subjects. TNF-alpha and IL-6, showed significant increase among patients with CHF due to ischaemic heart disease and cardiomyopathy compared to levels among CHF patients with valvular heart disease and hypertensive heart diseases. The levels of the cytokines were significantly higher among patients with class III and IV heart failure and those who died, compared to patients with class II heart failure. Multivariate logistic regression analysis revealed that CAD, cardiomyopathy, and IL-6 were strongly associated--and low ejection fraction and TNF-alpha--weakly associated with HF. Of 116 patients, 20 (17.2%) died during a follow-up of two years, and the deaths were mainly among NYHA class III and IV patients in whom the cause of CHF was CAD (10.9%) and cardiomyopathy (6.9%) which had greater levels of cytokines. The findings indicated that pro-inflammatory cytokines may be important indicators of causes, severity of CHF and prognosis among these patients.

Barriers and facilitators to enrollment and re-enrollment into the community health funds/Tiba Kwa Kadi (CHF/TIKA) in Tanzania: a cross-sectional inquiry on the effects of socio-demographic factors and social marketing strategies.

PubMed

Kapologwe, Ntuli A; Kagaruki, Gibson B; Kalolo, Albino; Ally, Mariam; Shao, Amani; Meshack, Manoris; Stoermer, Manfred; Briet, Amena; Wiedenmayer, Karin; Hoffman, Axel

2017-04-27

Introduction of a health insurance scheme is one of the ways to enhance access to health care services and to protect individuals from catastrophic health expenditures. Little is known on the influence of socio-demographic and social marketing strategies on enrollment and re-enrollment in the Community Health Fund/Tiba Kwa Kadi (CHF/TIKA) in Tanzania. This cross-sectional study employed quantitative methods for data collection between November 2014 and March 2015 in Singida and Shinyanga regions. Relationship between variables was obtained through Chi-square test and multivariate logistic regression. We recruited 496 participants in the study. Majority (92.7%) of participants consented to participate, with 229 (49.8%) and 231 (50.2%) members and non members of CHF/TIKA respectively. Majority (90.9%) were aware of CHF/TIKA. Majority of CHF/TIKA members and non-members (90% and 68.3% respectively) reported health facility-based sensitization as the most common social marketing approach employed to market the CHF/TIKA. The most popular marketing strategies in the country including traditional dances, football games, radio, television, news papers, and mosques/church were reported by few CHF and non CHF members. Multivariate Logistic regression models revealed no significant association between social marketing strategies and enrollment, but only socio-demographics; including marital status (AOR = 2.0, 95% CI 1.1-3.8) and family size (household with ≥ 6 members) (AOR = 1.5, 95% CI 1.0-2.5), were significant factors associated with enrollment/re-enrollment rate. This study indicated that low level of utilization of available social marketing strategies and socio-demographic factors are the barriers for attracting members to join the schemes. There is a need for applying various social marketing strategies and considering different facilitating and impending socio-demographic factors for the growth and sustainability of the scheme as we move towards universal health coverage.

Behavioral Effects of Systemic, Infralimbic and Prelimbic Injections of a Serotonin 5-HT2A Antagonist in Carioca High- and Low-Conditioned Freezing Rats

PubMed Central

León, Laura A.; Castro-Gomes, Vitor; Zárate-Guerrero, Santiago; Corredor, Karen; Mello Cruz, Antonio P.; Brandão, Marcus L.; Cardenas, Fernando P.; Landeira-Fernandez, J.

2017-01-01

The role of serotonin (5-hydroxytryptamine [5-HT]) and 5-HT2A receptors in anxiety has been extensively studied, mostly without considering individual differences in trait anxiety. Our laboratory developed two lines of animals that are bred for high and low freezing responses to contextual cues that are previously associated with footshock (Carioca High-conditioned Freezing [CHF] and Carioca Low-conditioned Freezing [CLF]). The present study investigated whether ketanserin, a preferential 5-HT2A receptor blocker, exerts distinct anxiety-like profiles in these two lines of animals. In the first experiment, the animals received a systemic injection of ketanserin and were exposed to the elevated plus maze (EPM). In the second experiment, these two lines of animals received microinjections of ketanserin in the infralimbic (IL) and prelimbic (PL) cortices and were exposed to either the EPM or a contextual fear conditioning paradigm. The two rat lines exhibited bidirectional effects on anxiety-like behavior in the EPM and opposite responses to ketanserin. Both systemic and intra-IL cortex injections of ketanserin exerted anxiolytic-like effects in CHF rats but anxiogenic-like effects in CLF rats. Microinjections of ketanserin in the PL cortex also exerted anxiolytic-like effects in CHF rats but had no effect in CLF rats. These results suggest that the behavioral effects of 5-HT2A receptor antagonism might depend on genetic variability associated with baseline reactions to threatening situations and 5-HT2A receptor expression in the IL and PL cortices. Highlights -CHF and CLF rats are two bidirectional lines that are based on contextual fear conditioning.-CHF rats have a more “anxious” phenotype than CLF rats in the EPM.-The 5-HT2A receptor antagonist ketanserin had opposite behavioral effects in CHF and CLF rats.-Systemic and IL injections either decreased (CHF) or increased (CLF) anxiety-like behavior.-PL injections either decreased (CHF) anxiety-like behavior or had no effect (CLF). PMID:28736518

N-terminal fraction of pro-B-type natriuretic peptide versus clinical risk scores for prognostic stratification in chronic systolic heart failure.

PubMed

Arzilli, Chiara; Aimo, Alberto; Vergaro, Giuseppe; Ripoli, Andrea; Senni, Michele; Emdin, Michele; Passino, Claudio

2018-05-01

Background The Seattle heart failure model or the cardiac and comorbid conditions (3C-HF) scores may help define patient risk in heart failure. Direct comparisons between them or versus N-terminal fraction of pro-B-type natriuretic peptide (NT-proBNP) have never been performed. Methods Data from consecutive patients with stable systolic heart failure and 3C-HF data were examined. A subgroup of patients had the Seattle heart failure model data available. The endpoints were one year all-cause or cardiovascular death. Results The population included 2023 patients, aged 68 ± 12 years, 75% were men. At the one year time-point, 198 deaths were recorded (10%), 124 of them (63%) from cardiovascular causes. While areas under the curve were not significantly different, NT-proBNP displayed better reclassification capability than the 3C-HF score for the prediction of one year all-cause and cardiovascular death. Adding NT-proBNP to the 3C-HF score resulted in a significant improvement in risk prediction. Among patients with Seattle heart failure model data available ( n = 798), the area under the curve values for all-cause and cardiovascular death were similar for the Seattle heart failure model score (0.790 and 0.820), NT-proBNP (0.783 and 0.803), and the 3C-HF score (0.770 and 0.800). The combination of the 3C-HF score and NT-proBNP displayed a similar prognostic performance to the Seattle heart failure model score for both endpoints. Adding NT-proBNP to the Seattle heart failure model score performed better than the Seattle heart failure model alone in terms of reclassification, but not discrimination. Conclusions Among systolic heart failure patients, NT-proBNP levels had better reclassification capability for all-cause and cardiovascular death than the 3C-HF score. The inclusion of NT-proBNP to the 3C-HF and Seattle heart failure model score resulted in significantly better risk stratification.

RUBI -a Reference mUltiscale Boiling Investigation for the Fluid Science Laboratory

NASA Astrophysics Data System (ADS)

Schweizer, Nils; Stelzer, Marco; Schoele-Schulz, Olaf; Picker, Gerold; Ranebo, Hans; Dettmann, Jan; Minster, Olivier; Toth, Balazs; Winter, Josef; Tadrist, Lounes; Stephan, Peter; Grassi, Walter; di Marco, Paolo; Colin, Catherine; Piero Celata, Gian; Thome, John; Kabov, Oleg

Boiling is a two-phase heat transfer process where large heat fluxes can be transferred with small driving temperature differences. The high performance of boiling makes the process very interesting for heat transfer applications and it is widely used in industry for example in power plants, refrigeration systems, and electronics cooling. Nevertheless, due to the large number of involved phenomena and their often highly dynamic nature a fundamental understanding and closed theoretical description is not yet accomplished. The design of systems incorporating the process is generally based on empirical correlations, which are commonly accompanied by large uncertainties and, thus, has to be verified by expensive test campaigns. Hence, strong efforts are currently made to develop applicable numerical tools for a reliable prediction of the boiling heat transfer performance and limits. In order to support and validate this development and, in particular as a precondition, to enhance the basic knowledge about boiling the comprehensive multi-scale experiment RUBI (Reference mUlti-scale Boiling Investigation) for the Fluid Science Laboratory on board the ISS is currently in preparation. The scientific objectives and requirements of RUBI have been defined by the members of the ESA topical team "Boiling and Multiphase Flow" and addresses fundamental aspects of boiling phenomena. The main objectives are the measurement of wall temperature and heat flux distribution underneath vapour bubbles with high spatial and tem-poral resolution by means of IR thermography accompanied by the synchronized high-speed observation of the bubble shapes. Furthermore, the fluid temperature in the vicinity and inside of the bubbles will be measured by a micro sensor array. Additional stimuli are the generation of an electric field above the heating surface and a shear flow created by a forced convection loop. The objective of these stimuli is to impose forces on the bubbles and investigate the resulting bubble behaviour such as bubble sliding on and detaching from the surface. The experiments benefits from the absence of vapour buoyancy and natural convection in the high quality and long-term microgravity of the ISS. Effects and phenomena like thermocapillary convection that are hardly observable in normal gravity conditions can be investigated. Clearly predefined conditions particularly of the thermal layer at the heating surface can be established without disturbances by natural convection. Vapour buoyancy as the main detaching force in normal gravity is missing. Hence, it is possible to study stationary, attached bubbles and alternative detaching forces. With RUBI a long history of boiling experiments is perpetuated that used microgravity as a tool for a deeper understanding of the fundamental phenomena. Several precursor experiments closely related to the RUBI project have already been conducted on parabolic flights. The subject of the paper is to provide an overview on the RUBI project, its scientific objectives and the corresponding experimental principle. The current design of the experiment container that is under development at ASTRIUM Space Transportation in Friedrichshafen will be introduced. Furthermore, results from the precursor experiments are presented. The industrial activities of the RUBI project are funded and the science team is supported by ESA.

A Report from the Thermal Science Research Center (TSRC)

NASA Technical Reports Server (NTRS)

Boyd, Ronald D.

1998-01-01

A vertical flow loop was designed and assembled to determine the local (circumferential and axial) and mean wall temperature distributions for single-phase and two-phase (subcooled and saturated) downward flow in both uniformly-heated and single-side heated vertical channels. Freon-11 was used as the working fluid in order to directly relate and compare the results with a previous experimental campaign which employed this same working fluid. For a given steady-state experiment, the following parameters were held constant: (1) exit pressure, (2) inlet temperature, and (3) mass velocity. For a given configuration of the 2.2 m long cylindrical channel test section, which had a 1.2 m long heated section, the applied heat rate was varied from zero through successive quasi-steady states to a level which corresponded to localized film boiling in the test section. The measurements showed that the boiling curve changes significantly at higher mass velocities with respect to both the circumferential and axial directions. The slope of the boiling curve changes in a non-monotonic fashion with respect to the circumferential directions. The slope of the boiling curve changes in a non-monotonic fashion with respect to the circumferential direction. The measurements point to the existence of a dry-out phenomenon occurring at multiple levels of the applied heat for the single-side heated channel. In comparing the heat transfer for horizontal channel flow with a vertically downward flow, the results show that significantly lower heat transfer occurs in the horizontal flow. However, this trend reverses as both the Reynolds number and the applied heat rate increase. Both the Liu-Winterton and Shah correlations were compared with the experimental data. The Shah correlation predicted the uniformly heated tube data better. When a thermal hydraulic diameter approach was used for the single-side heated case, the data at upstream locations for Z/L less than 0.5 was bounded above by the Liu-Winterton correlation and below by the Shah correlation. At Z/L = 0.5, the Shah correlation bounded the data; and for Z/L greater than 0.5, both correlations overpredicted the data with the Shah correlation being closest to the data. The present results indicate that additional correlational development is needed. In addressing some of the advanced space thermal management objectives concerning accommodating high heat fluxes in non-uniformly heated systems, a large battery of experiments 88 have been completed where local two-dimensional wall temperature variations were measured for both single-phase and two-phase flow in a single-side heated circular tube. As noted above, the results show significant axial and circumferential variations. Accurately accounting for such variations can result in optimized future advanced space, enhanced (high heat flux) thermal management systems.

Bi/In thermal resist for both Si anisotropic wet etching and Si/SiO2 plasma etching

NASA Astrophysics Data System (ADS)

Chapman, Glenn H.; Tu, Yuqiang; Peng, Jun

2004-01-01

Bi/In thermal resist is a bilayer structure of Bi over In films which can be exposed by laser with a wide range of wavelengths and can be developed by diluted RCA2 solutions. Current research shows bimetallic resist can work as etch masking layer for both dry plasma etching and wet anisotropic etching. It can act as both patterning and masking layers for Si and SiO2 with plasma "dry" etch using CF4/CHF3. The etching condition is CF4 flow rate 50 sccm, pressure 150 mTorr, and RF power 100 - 600W. The profile of etched structures can be tuned by adding CHF3 and other gases such as Ar, and by changing the CF4/CHF3 ratio. Depending on the fluorocarbon plasma etching recipe the etch rate of laser exposed Bi/In can be as low as 0.1 nm/min, 500 times lower than organic photoresists. O2 plasma ashing has little etching effect on exposed Bi/In. Bi/In also creates etch masking layers for alkaline-based (KOH, TMAH and EDP) "wet" anisotropic bulk Si etch without the need of SiO2 masking steps. The laser exposed Bi/In etches two times more slowly than SiO2. Experiment result shows that single metal Indium film exhibits thermal resist characteristics but at twice the exposure levels. It can be developed in diluted RCA2 solution and used as an etch mask layer for Si anisotropic etch. X-ray diffraction analysis shows that laser exposure causes both Bi and In single film to oxidize. In film may become amorphous when exposed to high laser power.

An Automated Approach for Ranking Journals to Help in Clinician Decision Support

PubMed Central

Jonnalagadda, Siddhartha R.; Moosavinasab, Soheil; Nath, Chinmoy; Li, Dingcheng; Chute, Christopher G.; Liu, Hongfang

2014-01-01

Point of care access to knowledge from full text journal articles supports decision-making and decreases medical errors. However, it is an overwhelming task to search through full text journal articles and find quality information needed by clinicians. We developed a method to rate journals for a given clinical topic, Congestive Heart Failure (CHF). Our method enables filtering of journals and ranking of journal articles based on source journal in relation to CHF. We also obtained a journal priority score, which automatically rates any journal based on its importance to CHF. Comparing our ranking with data gathered by surveying 169 cardiologists, who publish on CHF, our best Multiple Linear Regression model showed a correlation of 0.880, based on five-fold cross validation. Our ranking system can be extended to other clinical topics. PMID:25954382

B-type natriuretic peptides. A diagnostic breakthrough in heart failure.

PubMed

McCullough, P A

2003-04-01

B-type natriuretic peptide (BNP) is a neurohormone synthesized in the cardiac ventricles, which is released as N-terminal pro-brain natriuretic peptide (NT-proBNP) and then enzymatically cleaved in to the NT fragment and the immunoreactive BNP. Both tests have been used to identify patients with congestive heart failure (CHF). Important considerations for these tests include their half-lives in plasma, dependence on renal function for clearance, and the interpretation of their units of measure. In general, a BNP level below 100 pg/mL has strong negative predictive value in the assessment of patients with dyspnea caused by a disorder other than CHF. In addition, BNP levels can be used to gauge the effect of short-term treatment of acutely decompensated heart failure, and the peptide has been shown to be a reliable independent predictor of sudden cardiac death. In the absence of renal dysfunction NT-proBNP has also been shown to be an independent predictor of sudden death in CHF patients. Because both a large area of myonecrosis or concomitant left ventricular failure are related to prognosis in acute coronary syndromes, B-type natriuretic peptides have also been linked to outcomes in this condition. This article describes the physiology and timing of release of B-type natriuretic peptides and the rationale for their use in the following settings: 1) evaluation of decompensated CHF, 2) screening for chronic CHF, 3) prognosis of CHF and sudden death, and 4) prognosis in acute coronary syndromes with inferred left ventricular dysfunction.

The gap between policy and practice: a systematic review of patient-centred care interventions in chronic heart failure.

PubMed

Kane, P M; Murtagh, F E M; Ryan, K; Mahon, N G; McAdam, B; McQuillan, R; Ellis-Smith, C; Tracey, C; Howley, C; Raleigh, C; O'Gara, G; Higginson, I J; Daveson, B A

2015-11-01

Patient-centred care (PCC) is recommended in policy documents for chronic heart failure (CHF) service provision, yet it lacks an agreed definition. A systematic review was conducted to identify PCC interventions in CHF and to describe the PCC domains and outcomes. Medline, Embase, CINAHL, PsycINFO, ASSIA, the Cochrane database, clinicaltrials.gov, key journals and citations were searched for original studies on patients with CHF staged II-IV using the New York Heart Association (NYHA) classification. Included interventions actively supported patients to play informed, active roles in decision-making about their goals of care. Search terms included 'patient-centred care', 'quality of life' and 'shared decision making'. Of 13,944 screened citations, 15 articles regarding 10 studies were included involving 2540 CHF patients. Three studies were randomised controlled trials, and seven were non-randomised studies. PCC interventions focused on collaborative goal setting between patients and healthcare professionals regarding immediate clinical choices and future care. Core domains included healthcare professional-patient collaboration, identification of patient preferences, patient-identified goals and patient motivation. While the strength of evidence is poor, PCC has been shown to reduce symptom burden, improve health-related quality of life, reduce readmission rates and enhance patient engagement for patients with CHF. There is a small but growing body of evidence, which demonstrates the benefits of a PCC approach to care for CHF patients. Research is needed to identify the key components of effective PCC interventions before being able to deliver on policy recommendations.

[Effects of trimetazidine on serum oxygen free radicals in congestive heart failure].

PubMed

Ma, Qi-lin; Xie, Yong; Zhang, Sai-dan

2002-12-28

To investigate the level of serum superoxide dismutase (SOD) and maiondialdehyde (MDA) and left ventricular systolic function in congestive heart failure (CHF) and to evaluate the influence of trimetazidine on them. Serum SOD and MDA were measured in 50 patients with heart function from grade two to four and 15 normal subjects. All the persons underwent echocardiography to determine the left ventricular end-systolic volume index (LVESVI) and the left ventricular ejection fraction (EF). The patients with CHF were randomly treated with trimetazidine plus routine therapy (n = 25) or routine therapy only (n = 25) for 8 weeks with evaluations made before and after the treatment. The SOD level and EF in the patients with CHF significantly decreased and the MDA level and LVESVI in those patients significantly increased compared with the normal subjects (P < 0.05); the severer the CHF, the greater the changes. After the treatment, the SOD level and EF increased significantly and MDA and LVESVI decreased significantly (P < 0.01) in both the trimetazidine and the conventional groups. And these changes were more obvious in the trimetazidine group than in the conventional group(P < 0.01). Oxygen free radicals play an important role in the pathophysiologic changes of CHF. The level of serum SOD and MDA can indicate the degree of CHF. Trimetazidine not only increases the level of SOD and decreases the level of MDA, but also improves the left ventricular systolic function.

Influenza infection and heart failure-vaccination may change heart failure prognosis?

PubMed

Kadoglou, Nikolaos P E; Bracke, Frank; Simmers, Tim; Tsiodras, Sotirios; Parissis, John

2017-05-01

The interaction of influenza infection with the pathogenesis of acute heart failure (AHF) and the worsening of chronic heart failure (CHF) is rather complex. The deleterious effects of influenza infection on AHF/CHF can be attenuated by specific immunization. Our review aimed to summarize the efficacy, effectiveness, safety, and dosage of anti-influenza vaccination in HF. In this literature review, we searched MEDLINE and EMBASE from January 1st 1966 to December 31st, 2016, for studies examining the association between AHF/CHF, influenza infections, and anti-influenza immunizations. We used broad criteria to increase the sensitivity of the search. HF was a prerequisite for our search. The search fields used included "heart failure," "vaccination," "influenza," "immunization" along with variants of these terms. No restrictions on the type of study design were applied. The most common clinical scenario is exacerbation of pre-existing CHF by influenza infection. Scarce evidence supports a potential positive association of influenza infection with AHF. Vaccinated patients with pre-existing CHF have reduced all-cause morbidity and mortality, but effects are not consistently documented. Immunization with higher antigen quantity may confer additional protection, but such aggressive approach has not been generally advocated. Further studies are needed to delineate the role of influenza infection on AHF/CHF pathogenesis and maintenance. Annual anti-influenza vaccination appears to be an effective measure for secondary prevention in HF. Better immunization strategies and more efficacious vaccines are urgently necessary.

An intervention to promote physical activity and self-management in people with stable chronic heart failure The Home-Heart-Walk study: study protocol for a randomized controlled trial

PubMed Central

2011-01-01

Background Chronic heart failure (CHF) is a chronic debilitating condition with economic consequences, mostly because of frequent hospitalisations. Physical activity and adequate self-management capacity are important risk reduction strategies in the management of CHF. The Home-Heart-Walk is a self-monitoring intervention. This model of intervention has adapted the 6-minute walk test as a home-based activity that is self-administered and can be used for monitoring physical functional capacity in people with CHF. The aim of the Home-Heart-Walk program is to promote adherence to physical activity recommendations and improving self-management in people with CHF. Methods/Design A randomised controlled trial is being conducted in English speaking people with CHF in four hospitals in Sydney, Australia. Individuals diagnosed with CHF, in New York Heart Association Functional Class II or III, with a previous admission to hospital for CHF are eligible to participate. Based on a previous CHF study and a loss to follow-up of 10%, 166 participants are required to be able to detect a 12-point difference in the study primary endpoint (SF-36 physical function domain). All enrolled participant receive an information session with a cardiovascular nurse. This information session covers key self-management components of CHF: daily weight; diet (salt reduction); medication adherence; and physical activity. Participants are randomised to either intervention or control group through the study randomisation centre after baseline questionnaires and assessment are completed. For people in the intervention group, the research nurse also explains the weekly Home-Heart-Walk protocol. All participants receive monthly phone calls from a research coordinator for six months, and outcome measures are conducted at one, three and six months. The primary outcome of the trial is the physical functioning domain of quality of life, measured by the physical functioning subscale of the Medical Outcome Study Short Form -36. Secondary outcomes include physical functional capacity measured by the standard six minute walk test, self-management capacity, health related quality of life measured by Medical Outcome Study Short Form -36 and Minnesota Living With Heart Failure Questionnaire, self-efficacy and self-care behaviour. Discussion A self-monitoring intervention that can improve individual's exercise self-efficacy, self-management capacity could have potential significance in improving the management of people with chronic heart failure in community settings. Trial Registration Australian New Zealand Clinical Trial Registry 12609000437268 PMID:21366927

An intervention to promote physical activity and self-management in people with stable chronic heart failure The Home-Heart-Walk study: study protocol for a randomized controlled trial.

PubMed

Du, Hui Y; Newton, Phillip J; Zecchin, Robert; Denniss, Robert; Salamonson, Yenna; Everett, Bronwyn; Currow, David C; Macdonald, Peter S; Davidson, Patricia M

2011-03-02

Chronic heart failure (CHF) is a chronic debilitating condition with economic consequences, mostly because of frequent hospitalisations. Physical activity and adequate self-management capacity are important risk reduction strategies in the management of CHF. The Home-Heart-Walk is a self-monitoring intervention. This model of intervention has adapted the 6-minute walk test as a home-based activity that is self-administered and can be used for monitoring physical functional capacity in people with CHF. The aim of the Home-Heart-Walk program is to promote adherence to physical activity recommendations and improving self-management in people with CHF. A randomised controlled trial is being conducted in English speaking people with CHF in four hospitals in Sydney, Australia. Individuals diagnosed with CHF, in New York Heart Association Functional Class II or III, with a previous admission to hospital for CHF are eligible to participate. Based on a previous CHF study and a loss to follow-up of 10%, 166 participants are required to be able to detect a 12-point difference in the study primary endpoint (SF-36 physical function domain).All enrolled participant receive an information session with a cardiovascular nurse. This information session covers key self-management components of CHF: daily weight; diet (salt reduction); medication adherence; and physical activity. Participants are randomised to either intervention or control group through the study randomisation centre after baseline questionnaires and assessment are completed. For people in the intervention group, the research nurse also explains the weekly Home-Heart-Walk protocol. All participants receive monthly phone calls from a research coordinator for six months, and outcome measures are conducted at one, three and six months. The primary outcome of the trial is the physical functioning domain of quality of life, measured by the physical functioning subscale of the Medical Outcome Study Short Form -36. Secondary outcomes include physical functional capacity measured by the standard six minute walk test, self-management capacity, health related quality of life measured by Medical Outcome Study Short Form -36 and Minnesota Living With Heart Failure Questionnaire, self-efficacy and self-care behaviour. A self-monitoring intervention that can improve individual's exercise self-efficacy, self-management capacity could have potential significance in improving the management of people with chronic heart failure in community settings. Australian New Zealand Clinical Trial Registry 12609000437268.

Modeling of two-phase flow instabilities during startup transients utilizing RAMONA-4B methodology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paniagua, J.; Rohatgi, U.S.; Prasad, V.

1996-10-01

RAMONA-4B code is currently under development for simulating thermal hydraulic instabilities that can occur in Boiling Water Reactors (BWRs) and the Simplified Boiling Water Reactor (SBWR). As one of the missions of RAMONA-4B is to simulate SBWR startup transients, where geysering or condensation-induced instability may be encountered, the code needs to be assessed for this application. This paper outlines the results of the assessments of the current version of RAMONA-4B and the modifications necessary for simulating the geysering or condensation-induced instability. The test selected for assessment are the geysering tests performed by Prof Aritomi (1993).

Centrifugal inertia effects in two-phase face seal films

NASA Technical Reports Server (NTRS)

Basu, P.; Hughes, W. F.; Beeler, R. M.

1987-01-01

A simplified, semianalytical model has been developed to analyze the effect of centrifugal inertia in two-phase face seals. The model is based on the assumption of isothermal flow through the seal, but at an elevated temperature, and takes into account heat transfer and boiling. Using this model, seal performance curves are obtained with water as the working fluid. It is shown that the centrifugal inertia of the fluid reduces the load-carrying capacity dramatically at high speeds and that operational instability exists under certain conditions. While an all-liquid seal may be starved at speeds higher than a 'critical' value, leakage always occurs under boiling conditions.

The administrative costs of community-based health insurance: a case study of the community health fund in Tanzania

PubMed Central

Borghi, Josephine; Makawia, Suzan; Kuwawenaruwa, August

2015-01-01

Community-based health insurance expansion has been proposed as a financing solution for the sizable informal sector in low-income settings. However, there is limited evidence of the administrative costs of such schemes. We assessed annual facility and district-level costs of running the Community Health Fund (CHF), a voluntary health insurance scheme for the informal sector in a rural and an urban district from the same region in Tanzania. Information on resource use, CHF membership and revenue was obtained from district managers and health workers from two facilities in each district. The administrative cost per CHF member household and the cost to revenue ratio were estimated. Revenue collection was the most costly activity at facility level (78% of total costs), followed by stewardship and management (13%) and pooling of funds (10%). Stewardship and management was the main activity at district level. The administration cost per CHF member household ranged from USD 3.33 to USD 12.12 per year. The cost to revenue ratio ranged from 50% to 364%. The cost of administering the CHF was high relative to revenue generated. Similar studies from other settings should be encouraged. PMID:24334331

Hospitalization for congestive heart failure: is it still a cardiology business?

PubMed

Grigioni, Francesco; Carinci, Valeria; Favero, Luca; Bacchi Reggiani, Letizia; Magnani, Gaia; Potena, Luciano; Barbieri, Alessandra; Magelli, Carlo; Branzi, Angelo; Magnani, Bruno

2002-01-01

Hospital management of CHF and predictors of hospital mortality remain unclear. To address these issues, we analyzed the hospital admissions for CHF during 1996 in a large university hospital. Patients discharged with the principal diagnosis of CHF were considered eligible for the study. Among the 1511 patients (3% of all discharges) who satisfied the inclusion criteria, 75% were treated in general medicine departments (GMD) and 22% in cardiology units (CU). Patients admitted to GMD were older than those treated in CU (79+/-10 vs. 68+/-15 years, P<0.001), included a higher proportion of females (56% vs. 37%, P<0.001), and presented a higher rate of hospital mortality (13% vs. 4%, P<0.001). The overall mean length of stay was 11+/-9 days. At multivariate analysis, length of stay was not associated with the department (i.e. GMD/CU) (P=0.273). CHF is a common lethal condition often requiring treatment in GMD. Length of stay appears to depend more on patients' characteristics than on differences in practice between GMD and CU. Patients admitted to GMD present higher rates of comorbidity and hospital mortality. Strategies are urgently needed to improve hospital management of CHF.

[Pathogenetic and Prognostic Role of Growth Factors in the Development of Chronic Heart Failure].

PubMed

Teplyakov, A T; Berezikova, E N; Shilov, S N; Efremova, A V; Pustovetova, M G; Popova, A A; Grakova, E V; Torim, Y Y; Safronov, I D; Andriyanova, A V

2017-10-01

To study the role of growth factors ((vascular endothelial growth factor (VEGF), platelet derived growth factor AB (PDGF-AB) and basic fibroblast growth factor (FGF-basic)) in the development and progression of chronic heart failure (CHF) in patients with ishcemic heart disease (IHD). We included in this study 94 patients with CHF. The control group comprised 32 persons. Blood serum levels of growth factors were determined at baseline and after 12 months of observation by enzyme-linked immunosorbent assay. VEGF, PDGF-AB and FGF-basic play an important role in the pathogenesis and progression of heart failure in patients with IHD, determining the increased risk of adverse cardiovascular events in this pathology. Serum activity of growth factors characterizes the severity and course of CHF: with disease progression levels of VEGF and FGF-basic decrease and PDGF-AB concentration increases. Initial low level of VEGF expression regardless of the sex of the patient's sex, significantly low level of FGF-basic and significantly high PDGF-AB in men characterizes unfavorable course of CHF. A correlation has been established between blood serum levels of VEGF, PDGF-AB and FGF-basic and severity and course of CHF.

Phase relations and adiabats in boiling seafloor geothermal systems

USGS Publications Warehouse

Bischoff, J.L.; Pitzer, Kenneth S.

1985-01-01

Observations of large salinity variations and vent temperatures in the range of 380-400??C suggest that boiling or two-phase separation may be occurring in some seafloor geothermal systems. Consideration of flow rates and the relatively small differences in density between vapors and liquids at the supercritical pressures at depth in these systems suggests that boiling is occurring under closed-system conditions. Salinity and temperature of boiling vents can be used to estimate the pressure-temperature point in the subsurface at which liquid seawater first reached the two-phase boundary. Data are reviewed to construct phase diagrams of coexisting brines and vapors in the two-phase region at pressures corresponding to those of the seafloor geothermal systems. A method is developed for calculating the enthalpy and entropy of the coexisting mixtures, and results are used to construct adiabats from the seafloor to the P-T two-phase boundary. Results for seafloor vents discharging at 2300 m below sea level indicate that a 385??C vent is composed of a brine (7% NaCl equivalent) in equilibrium with a vapor (0.1% NaCl). Brine constitutes 45% by weight of the mixture, and the fluid first boiled at approximately 1 km below the seafloor at 415??C, 330 bar. A 400??C vent is primarily vapor (88 wt.%, 0.044% NaCl) with a small amount of brine (26% NaCl) and first boiled at 2.9 km below the seafloor at 500??C, 520 bar. These results show that adiabatic decompression in the two-phase region results in dramatic cooling of the fluid mixture when there is a large fraction of vapor. ?? 1985.

Distribution of Trichloroethylene and Geologic Controls on Contaminant Pathways near the Royal River, McKin Superfund Site Area, Gray, Maine

USGS Publications Warehouse

Lyford, Forest P.; Flight, L.E.; Stone, Janet Radway; Clifford, Scott

1999-01-01

Vapor-diffusion samplers were used in the autumn of 1997 to determine the lateral extent and distribution of concentrations of a trichloroethylene (TCE) plume in the ground-water discharge area near the McKin Superfund Site, Gray, Maine. Analyses of vapor in the samplers identified a plume about 800 feet wide entering the river near Boiling Springs, an area of ground-water discharge on the flood plain of the Royal River. The highest observed concentration of TCE in vapor was in an area of sand boils on the western bank of the river and about 200 feet downstream from Boiling Springs. Previous studies showed that most of the TCE load in the river originated in the area of the sand boils. In general, highest concentrations were observed on the western side of the river on the upgradient side of the plume, but TCE also was detected at numerous locations in the center and eastern bank of the river. The TCE plume discharges to the river where fine-grained glaciomarine sediments of the Presumpscot Formation are absent and where coarse-grained facies of buried glaciomarine fan deposits provide a pathway for ground-water flow. Based on results of analyses of vapor-diffusion samples and other previous studies, the plume appears to pass under and beyond the river near Boiling Springs and along the river for about 300 feet downstream from the sand boils. A coarse-grained, organic-rich layer at the base of the alluvial flood plain sediments is confined by overlying fine-grained alluvial sediments and may provide a conduit for ground-water leaking upward from buried glaciomarine fan deposits.

AUTOSOMAL RECESSIVE POLYCYSTIC KIDNEY DISEASE AND CONGENITAL HEPATIC FIBROSIS: SUMMARY STATEMENT OF A FIRST NATIONAL INSTITUTES OF HEALTH/OFFICE OF RARE DISEASES CONFERENCE

PubMed Central

Gunay-Aygun, Meral; Avner, Ellis D.; Bacallo, Robert L.; Choyke, Peter L.; Flynn, Joseph T.; Germino, Gregory G.; Guay-Woodford, Lisa; Harris, Peter; Heller, Theo; Ingelfinger, Julie; Kaskel, Frederick; Kleta, Robert; LaRusso, Nicholas F.; Mohan, Parvathi; Pazour, Gregory J.; Shneider, Benjamin L.; Torres, Vicente E.; Wilson, Patricia; Zak, Colleen; Zhou, Jing; Gahl, William A.

2010-01-01

Researchers and clinicians with expertise in autosomal recessive polycystic kidney disease and congenital hepatic fibrosis (ARPKD/CHF) and related fields met on May 5-6, 2005, on the National Institutes of Health (NIH) campus for a 1.5-day symposium sponsored by the NIH Office of Rare Diseases, the National Human Genome Research Institute (NHGRI), and in part by the ARPKD/CHF Alliance. The meeting addressed the present status and the future of ARPKD/CHF research. PMID:16887426

Single-bubble dynamics in pool boiling of one-component fluids

NASA Astrophysics Data System (ADS)

Xu, Xinpeng; Qian, Tiezheng

2014-06-01

We numerically investigate the pool boiling of one-component fluids with a focus on the effects of surface wettability on the single-bubble dynamics. We employed the dynamic van der Waals theory [Phys. Rev. E 75, 036304 (2007), 10.1103/PhysRevE.75.036304], a diffuse-interface model for liquid-vapor flows involving liquid-vapor transition in nonuniform temperature fields. We first perform simulations for bubbles on homogeneous surfaces. We find that an increase in either the contact angle or the surface superheating can enhance the bubble spreading over the heating surface and increase the bubble departure diameter as well and therefore facilitate the transition into film boiling. We then examine the dynamics of bubbles on patterned surfaces, which incorporate the advantages of both hydrophobic and hydrophilic surfaces. The central hydrophobic region increases the thermodynamic probability of bubble nucleation while the surrounding hydrophilic region hinders the continuous bubble spreading by pinning the contact line at the hydrophobic-hydrophilic intersection. This leads to a small bubble departure diameter and therefore prevents the transition from nucleate boiling into film boiling. With the bubble nucleation probability increased and the bubble departure facilitated, the efficiency of heat transfer on such patterned surfaces is highly enhanced, as observed experimentally [Int. J. Heat Mass Transfer 57, 733 (2013), 10.1016/j.ijheatmasstransfer.2012.10.080]. In addition, the stick-slip motion of contact line on patterned surfaces is demonstrated in one-component fluids, with the effect weakened by surface superheating.

Small interfering RNA therapy against carbohydrate sulfotransferase 15 inhibits cardiac remodeling in rats with dilated cardiomyopathy.

PubMed

Watanabe, Kenichi; Arumugam, Somasundaram; Sreedhar, Remya; Thandavarayan, Rajarajan A; Nakamura, Takashi; Nakamura, Masahiko; Harima, Meilei; Yoneyama, Hiroyuki; Suzuki, Kenji

2015-07-01

Carbohydrate sulfotransferase 15 (CHST15) is a sulfotransferase responsible for biosynthesis of chondroitin sulfate E (CS-E), which plays important roles in numerous biological events such as biosynthesis of proinflammatory cytokines. However, the effects of CHST15 siRNA in rats with chronic heart failure (CHF) after experimental autoimmune myocarditis (EAM) have not yet been investigated. CHF was elicited in Lewis rats by immunization with cardiac myosin, and after immunization, the rats were divided into two groups and treated with either CHST15 siRNA (2μg/week) or vehicle. Age matched normal rats without immunizations were also included in this study. After 7weeks of treatment, we investigated the effects of CHST15 siRNA on cardiac function, proinflammatory cytokines, and cardiac remodeling in EAM rats. Myocardial functional parameters measured by hemodynamic and echocardiographic studies were significantly improved by CHST15 siRNA treatment in rats with CHF compared with that of vehicle-treated CHF rats. CHST15 siRNA significantly reduced cardiac fibrosis, and hypertrophy and its marker molecules (left ventricular (LV) mRNA expressions of transforming growth factor beta1, collagens I and III, and atrial natriuretic peptide) compared with vehicle-treated CHF rats. CHF-induced increased myocardial mRNA expressions of proinflammatory cytokines [interleukin (IL)-6, IL-1β], monocyte chemoattractant protein-1, and matrix metalloproteinases (MMP-2 and -9), and CHST15 were also suppressed by the treatment with CHST15 siRNA. Western blotting study has confirmed the results obtained from mRNA analysis as CHST15 siRNA treated rats expressed reduced levels of inflammatory and cardiac remodeling marker proteins. Our results demonstrate for the first time, that CHST15 siRNA treatment significantly improved LV function and ameliorated the progression of cardiac remodeling in rats with CHF after EAM. Copyright © 2015 Elsevier Inc. All rights reserved.

Muscle oxygen transport and utilization in heart failure: implications for exercise (in)tolerance.

PubMed

Poole, David C; Hirai, Daniel M; Copp, Steven W; Musch, Timothy I

2012-03-01

The defining characteristic of chronic heart failure (CHF) is an exercise intolerance that is inextricably linked to structural and functional aberrations in the O(2) transport pathway. CHF reduces muscle O(2) supply while simultaneously increasing O(2) demands. CHF severity varies from moderate to severe and is assessed commonly in terms of the maximum O(2) uptake, which relates closely to patient morbidity and mortality in CHF and forms the basis for Weber and colleagues' (167) classifications of heart failure, speed of the O(2) uptake kinetics following exercise onset and during recovery, and the capacity to perform submaximal exercise. As the heart fails, cardiovascular regulation shifts from controlling cardiac output as a means for supplying the oxidative energetic needs of exercising skeletal muscle and other organs to preventing catastrophic swings in blood pressure. This shift is mediated by a complex array of events that include altered reflex and humoral control of the circulation, required to prevent the skeletal muscle "sleeping giant" from outstripping the pathologically limited cardiac output and secondarily impacts lung (and respiratory muscle), vascular, and locomotory muscle function. Recently, interest has also focused on the dysregulation of inflammatory mediators including tumor necrosis factor-α and interleukin-1β as well as reactive oxygen species as mediators of systemic and muscle dysfunction. This brief review focuses on skeletal muscle to address the mechanistic bases for the reduced maximum O(2) uptake, slowed O(2) uptake kinetics, and exercise intolerance in CHF. Experimental evidence in humans and animal models of CHF unveils the microvascular cause(s) and consequences of the O(2) supply (decreased)/O(2) demand (increased) imbalance emblematic of CHF. Therapeutic strategies to improve muscle microvascular and oxidative function (e.g., exercise training and anti-inflammatory, antioxidant strategies, in particular) and hence patient exercise tolerance and quality of life are presented within their appropriate context of the O(2) transport pathway.

Effect of functional electrical stimulation on cardiovascular outcomes in patients with chronic heart failure.

PubMed

Kadoglou, Nikolaos Pe; Mandila, Christina; Karavidas, Apostolos; Farmakis, Dimitrios; Matzaraki, Vasiliki; Varounis, Christos; Arapi, Sofia; Perpinia, Anastasia; Parissis, John

2017-05-01

Background/design Functional electrical stimulation of lower limb muscles is an alternative method of training in patients with chronic heart failure (CHF). Although it improves exercise capacity in CHF, we performed a randomised, placebo-controlled study to investigate its effects on long-term clinical outcomes. Methods We randomly assigned 120 patients, aged 71 ± 8 years, with stable CHF (New York Heart Association (NYHA) class II/III (63%/37%), mean left ventricular ejection fraction 28 ± 5%), to either a 6-week functional electrical stimulation training programme or placebo. Patients were followed for up to 19 months for death and/or hospitalisation due to CHF decompensation. Results At baseline, there were no significant differences in demographic parameters, CHF severity and medications between groups. During a median follow-up of 383 days, 14 patients died (11 cardiac, three non-cardiac deaths), while 40 patients were hospitalised for CHF decompensation. Mortality did not differ between groups (log rank test P = 0.680), while the heart failure-related hospitalisation rate was significantly lower in the functional electrical stimulation group (hazard ratio (HR) 0.40, 95% confidence interval (CI) 0.21-0.78, P = 0.007). The latter difference remained significant after adjustment for prognostic factors: age, gender, baseline NYHA class and left ventricular ejection fraction (HR 0.22, 95% CI 0.10-0.46, P < 0.001). Compared to placebo, functional electrical stimulation training was associated with a lower occurrence of the composite endpoint (death or heart failure-related hospitalisation) after adjustment for the above-mentioned prognostic factors (HR 0.21, 95% CI 0.103-0.435, P < 0.001). However, that effect was mostly driven by the favourable change in hospitalisation rates. Conclusions In CHF patients, 6 weeks functional electrical stimulation training reduced the risk of heart failure-related hospitalisations, without affecting the mortality rate. The beneficial long-term effects of this alternative method of training require further investigation.

Effectiveness of an educational self-management program for outpatients with chronic heart failure.

PubMed

Otsu, Haruka; Moriyama, Michiko

2011-12-01

The occurrence rate of chronic heart failure (CHF) in Japan is estimated to be 50,000 per one million persons. It is important for the Japanese medical financial system to institute a program of disease management in order to prevent the deterioration of persons with CHF. However, there are still few studies on the disease management of CHF in Japan. Therefore, the purpose of this study was to provide an educational self-management program to Japanese outpatients with CHF in order to improve their clinical outcomes. A randomized, controlled trial with 102 outpatients with CHF was conducted. There were 50 participants in the intervention group and 52 participants in the control group. The control group received medical treatment and standard care. In addition to this, the intervention group also received an educational program for 6 months. The program consisted of six nurse-directed sessions that were provided to each outpatient once per month in a clinical setting for a total of 6 months. A follow-up session was conducted each month for 6 months. The data collection was carried out at the start of the program and at 3, 6, 9, and 12 months. Significant differences could be observed in the primary and secondary outcomes and in the process indicators between the two groups after the program began. In other words, all the indicators improved for the intervention group, compared to the control group. Therefore, this program was considered to be effective. Further long-term care is necessary for outpatients with CHF in order to prevent their deterioration and to maintain their health status, even though this 6 month program did provide them with proper knowledge regarding self-care for CHF and affected their therapy results. © 2010 The Authors. Japan Journal of Nursing Science © 2010 Japan Academy of Nursing Science.

Soluble Urokinase-Type Plasminogen Activator Receptor Improves Risk Prediction in Patients With Chronic Heart Failure.

PubMed

Koller, Lorenz; Stojkovic, Stefan; Richter, Bernhard; Sulzgruber, Patrick; Potolidis, Christos; Liebhart, Florian; Mörtl, Deddo; Berger, Rudolf; Goliasch, Georg; Wojta, Johann; Hülsmann, Martin; Niessner, Alexander

2017-04-01

This study investigated the predictive value of soluble urokinase-type plasminogen activator receptor (suPAR) in patients with chronic heart failure (CHF). SuPAR originates from proteolytic cleavage of the membrane-bound receptor from activated immune and endothelial cells and reflects the level of immune activation. As inflammation plays a crucial role in the complex pathophysiology of CHF, we hypothesized that suPAR might be a suitable prognostic biomarker in patients with CHF. SuPAR levels were determined in 319 patients with CHF admitted to our outpatient department for heart failure and in a second cohort consisting of 346 patients with CHF, for validation. During a median follow-up time of 3.2 years, 119 patients (37.3%) died. SuPAR was a strong predictor of mortality with a crude hazard ratio (HR) per increase of 1 SD (HR per 1 SD) of 1.96 (95% confidence interval [CI]: 1.63 to 2.35; p < 0.001) in univariate analysis and remained significant after comprehensive multivariate adjustment with an adjusted HR per 1 SD of 1.38 (95% CI: 1.04 to 1.83; p = 0.026). SuPAR added prognostic value beyond the multivariate model indicated by improvements in C-statistics (area under the curve: 0.72 vs 0.74, respectively; p = 0.02), the category-free net reclassification index (24.9%; p = 0.032), and the integrated discrimination improvement (0.011; p = 0.05). Validation in the second cohort yielded consistent results. SuPAR is a strong and independent predictor of mortality in patients with CHF, potentially suitable to refine risk assessment in this vulnerable group of patients. Our results emphasize the impact of immune activation on survival in patients with CHF. Copyright © 2017 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

Analysis of a large cohort of health maintenance organization patients with congestive heart failure.

PubMed

Gladowski, Patricia; Fetterolf, Donald; Beals, Susan; Holleran, Mary Kay; Reich, Sanford

2003-01-01

The aim of this article was to measure guideline compliance in the care of health plan members diagnosed with congestive heart failure (CHF). Chart review was conducted on members with a discharge diagnosis of CHF (n = 2,697). Information was entered onto a scannable form designed by the health plan, which was coupled to an optical character recognition reader and entered into a database. Eighty-four percent of the patients had an ejection fraction (EF) measured. An angiotensin-converting enzyme inhibitor was prescribed to 72% of patients with an EF less than 40%. Comorbidities and other measures were evaluated and based on guideline recommendations. Most of the CHF patients in this health plan are being treated appropriately during posthospitalization for CHF. The use of a novel, cost-effective method for data collection resulted in the rapid acquisition of clinical data for analysis.

Severe congestive heart failure patient on amiodarone presenting with myxedemic coma: a case report.

PubMed

Shaheen, Mazen

2009-01-01

This is a case report of myxedema coma secondary to amiodarone-induced hypothyroidism in a patient with severe congestive heart failure (CHF). To our knowledge and after reviewing the literature there is one case report of myxedema coma during long term amiodarone therapy. Myxedema coma is a life threatening condition that carries a mortality reaching as high as 20% with treatment. The condition is treated with intravenous thyroxine (T4) or intravenous tri-iodo-thyronine (T3). Patients with CHF on amiodarone may suffer serious morbidity and mortality from hypothyroidism, and thus may deserve closer follow up for thyroid stimulating hormone (TSH) levels. This case report carries an important clinical application given the frequent usage of amiodarone among CHF patients. The myriad clinical presentation of myxedema coma and its serious morbidity and mortality stresses the need to suspect this clinical syndrome among CHF patients presenting with hypotension, weakness or other unexplained symptoms.

[The role of hypotension as a factor of unfavorable prognosis in patients with chronic heart failure].

PubMed

Kapanadze, L G; Petrukhina, A A; Nasonova, S N; Skvortsov, A A; Mareev, V Iu

2011-01-01

Despite obvious achievements during last decades in studies of pathogenesis and search for effective ways of treatment of chronic heart failure (CHF) it remains one of most severe and prognostically unfavorable diseases of the cardiovascular system. Thereby determination of predictors of death and detection of high risk patients for more active drug interventions on CHF progression appears to be actual. It has been shown in a number of epidemiological and cohort studies that low arterial pressure (AP) serves as an independent risk factor of prognosis in patients with CHF. In this paper we present short literature review on this theme, consideration of possible mechanisms of negative effect of arterial hypotension on function of vitally important organs in patients with CHF, and summation of data of studies which have demonstrated relationship between low level of AP and worsening of prognosis.

Barriers and facilitators to self-care in chronic heart failure: a meta-synthesis of qualitative studies.

PubMed

Siabani, Soraya; Leeder, Stephen R; Davidson, Patricia M

2013-01-01

Chronic heart failure (CHF) is a costly condition that places large demands on self-care. Failure to adhere with self-care recommendations is common and associated with frequent hospitalization. Understanding the factors that enable or inhibit self-care is essential in developing effective health care interventions. This qualitative review was conducted to address the research question, "What are the barriers and facilitators to self-care among patients with CHF?" Electronic databases including Medline, EMBASE, CINAHL, Web of Science, Scopus and Google scholar were searched. Articles were included if they were peer reviewed (1995 to 2012), in English language and investigated at least one contextual or individual factor impacting on self-care in CHF patients > 18years. The criteria defined by Kuper et al. including clarity and appropriateness of sampling, data collection and data analysis were used to appraise the quality of articles. Twenty-three articles met the inclusion criteria. Factors impacting on self-care were included factors related to symptoms of CHF and the self-care process; factors related to personal characteristics; and factors related to environment and self-care system. Important factors such as socioeconomic situation and education level have not been explored extensively and there were minimal data on the influence of age, gender, self-confidence and duration of disease. Although there is an emerging literature, further research is required to address the barriers and facilitators to self-care in patients with CHF in order to provide an appropriate guide for intervention strategies to improve self-care in CHF.

Interdisciplinary approach to compensation of hypoglycemia in diabetic patients with chronic heart failure.

PubMed

Anfinogenova, Yana; Grakova, Elena V; Shvedova, Maria; Kopieva, Kristina V; Teplyakov, Alexander T; Popov, Sergey V

2018-05-01

Diabetes mellitus is a chronic disease requiring lifelong control with hypoglycemic agents that must demonstrate excellent efficacy and safety profiles. In patients taking glucose-lowering drugs, hypoglycemia is a common cause of death associated with arrhythmias, increased thrombus formation, and specific effects of catecholamines due to sympathoadrenal activation. Focus is now shifting from merely glycemic control to multifactorial approach. In the context of individual drugs and classes, this article reviews interdisciplinary strategies evaluating metabolic effects of drugs for treatment of chronic heart failure (CHF) which can mask characteristic hypoglycemia symptoms. Hypoglycemia unawareness and cardiac autonomic neuropathy are discussed. Data suggesting that hypoglycemia modulates immune response are reviewed. The potential role of gut microbiota in improving health of patients with diabetes and CHF is emphasized. Reports stating that nondiabetic CHF patients can have life-threatening hypoglycemia associated with imbalance of thyroid hormones are discussed. Regular glycemic control based on HbA1c measurements and adequate pharmacotherapy remain the priorities in diabetes management. New antihyperglycemic drugs with safer profiles should be preferred in vulnerable CHF patients. Multidrug interactions must be considered. Emerging therapies with reduced hypoglycemia risk, telemedicine, sensor technologies, and genetic testing predicting hypoglycemia risk may help solving the challenges of hypoglycemia in CHF patients with diabetes. Interdisciplinary work may involve cardiologists, diabetologists/endocrinologists, immunologists, gastroenterologists, microbiologists, nutritionists, imaging specialists, geneticists, telemedicine experts, and other relevant specialists. This review emphasizes that systematic knowledge on pathophysiology of hypoglycemia in diabetic patients with CHF is largely lacking and the gaps in our understanding require further discoveries.

Australia's health care reform agenda: implications for the nurses' role in chronic heart failure management.

PubMed

Betihavas, Vasiliki; Newton, Phillip J; Du, Hui Yun; Macdonald, Peter S; Frost, Steven A; Stewart, Simon; Davidson, Patricia M

2011-08-01

The importance of the nursing role in chronic heart failure (CHF) management is increasingly recognised. With the recent release of the National Health and Hospitals Reform Commission (NHHRC) report in Australia, a review of nursing roles in CHF management is timely and appropriate. This paper aims to discuss the implications of the NHHRC report and nursing roles in the context of CHF management in Australia. The electronic databases, Thomson Rheuters Web of Knowledge, Scopus and the Cumulative Index to Nursing and Allied Health Literature (CINAHL), were searched using keywords including; "heart failure", "management", "Australia" and "nursing". In addition policy documents were reviewed including statements and reports from key professional organisations and Government Departments to identify issues impacting on nursing roles in CHF management. There is a growing need for the prevention and control of chronic conditions, such as CHF. This involves an increasing emphasis on specialist cardiovascular nurses in community based settings, both in outreach and inreach health service models. This review has highlighted the need to base nursing roles on evidence based principles and identify the importance of the nursing role in coordinating and managing CHF care in both independent and collaborative practice settings. The importance of the nursing role in early chronic disease symptom recognition and implementing strategies to prevent further deterioration of individuals is crucial to improving health outcomes. Consideration should be given to ensure that evidence based principles are adopted in models of nursing care. Copyright © 2010 Australian College of Critical Care Nurses Ltd. Published by Elsevier Ltd. All rights reserved.

Doppler Assessment of Diastolic Function Reflect the Severity of Injury in Rats With Chronic Heart Failure.

PubMed

Sanchez, Pablo; Lancaster, Jordan J; Weigand, Kyle; Mohran, Saffie-Alrahman Ezz-Eldin; Goldman, Steven; Juneman, Elizabeth

2017-10-01

For chronic heart failure (CHF), more emphasis has been placed on evaluation of systolic as opposed to diastolic function. Within the study of diastology, measurements of left ventricular (LV) longitudinal myocardial relaxation have the most validation. Anterior wall radial myocardial tissue relaxation velocities along with mitral valve inflow (MVI) patterns are applicable diastolic parameters in the differentiation between moderate and severe disease in the ischemic rat model of CHF. Myocardial tissue relaxation velocities correlate with traditional measurements of diastolic function (ie, hemodynamics, Tau, and diastolic pressure-volume relationships). Male Sprague-Dawley rats underwent left coronary artery ligation or sham operation. Echocardiography was performed at 3 and 6 weeks after coronary ligation to evaluate LV ejection fraction (EF) and LV diastolic function through MVI patterns (E, A, and E/A) and Doppler imaging of the anterior wall (e' and a'). The rats were categorized into moderate or severe CHF according to their LV EF at 3 weeks postligation. Invasive hemodynamic measurements with solid-state pressure catheters were obtained at the 6-week endpoint. Moderate (N = 20) and severe CHF (N = 22) rats had significantly (P < .05) different EFs, hemodynamics, and diastolic pressure-volume relationships. Early diastolic anterior wall radial relaxation velocities as well as E/e' ratios separated moderate from severe CHF and both diastolic parameters had strong correlations with invasive hemodynamic measurements of diastolic function. Radial anterior wall e' and E/e' can be used for serial assessment of diastolic function in rats with moderate and severe CHF. Copyright © 2017 Elsevier Inc. All rights reserved.

Size and shape of right heart chambers in mitral valve regurgitation in small-breed dogs.

PubMed

Carlsson, C; Häggström, J; Eriksson, A; Järvinen, A -K; Kvart, C; Lord, P

2009-01-01

The contribution of right heart (RH) chamber enlargement to general heart enlargement seen on thoracic radiographs in mitral regurgitation (MR) is not known. To determine the size and shape of the RH chambers in normal dogs and dogs with varying degrees of MR. Fifty-four privately owned dogs: 13 normal, 41 with varying degrees of MR including 25 with congestive heart failure (CHF). Archived first pass radionuclide angiocardiograms were used to produce static images of the RH and left heart (LH) chambers. Indexes of size and shape of the RH and LH chambers were related to severity of MR determined by heart rate-normalized pulmonary transit time (nPTT), vertebral heart scale (VHS), and clinical status. RH shape was measured by a circularity index of RH short axis/long axis. A 2nd degree polynomial fit best described the ratios; RH/LH dimension to nPTT (R(2)= 0.62) and to VHS (R(2)= 0.43), RH/LH area to nPTT (R(2)= 0.64) and to VHS (R(2)= 0.58), all P < .001. RH circularity was decreased in CHF, P < .001. In CHF, the RH chambers of 16 dogs were both flattened and enlarged, whereas 9 had convex septal borders. RH chambers are not significantly dilated in dogs with mild to moderate MR without CHF. In CHF, RH chambers enlarge and also may be compressed by the LH chambers. Pulmonary hypertension probably is present in some dogs with CHF. Increased sternal contact is not a useful sign of right-sided heart dilatation in MR.

Intelligent data analysis: the best approach for chronic heart failure (CHF) follow up management.

PubMed

Mohammadzadeh, Niloofar; Safdari, Reza; Baraani, Alireza; Mohammadzadeh, Farshid

2014-08-01

Intelligent data analysis has ability to prepare and present complex relations between symptoms and diseases, medical and treatment consequences and definitely has significant role in improving follow-up management of chronic heart failure (CHF) patients, increasing speed ​​and accuracy in diagnosis and treatments; reducing costs, designing and implementation of clinical guidelines. The aim of this article is to describe intelligent data analysis methods in order to improve patient monitoring in follow and treatment of chronic heart failure patients as the best approach for CHF follow up management. Minimum data set (MDS) requirements for monitoring and follow up of CHF patient designed in checklist with six main parts. All CHF patients that discharged in 2013 from Tehran heart center have been selected. The MDS for monitoring CHF patient status were collected during 5 months in three different times of follow up. Gathered data was imported in RAPIDMINER 5 software. Modeling was based on decision trees methods such as C4.5, CHAID, ID3 and k-Nearest Neighbors algorithm (K-NN) with k=1. Final analysis was based on voting method. Decision trees and K-NN evaluate according to Cross-Validation. Creating and using standard terminologies and databases consistent with these terminologies help to meet the challenges related to data collection from various places and data application in intelligent data analysis. It should be noted that intelligent analysis of health data and intelligent system can never replace cardiologists. It can only act as a helpful tool for the cardiologist's decisions making.

Numerical Modeling of Saturated Boiling in a Heated Tube

NASA Technical Reports Server (NTRS)

Majumdar, Alok; LeClair, Andre; Hartwig, Jason

2017-01-01

This paper describes a mathematical formulation and numerical solution of boiling in a heated tube. The mathematical formulation involves a discretization of the tube into a flow network consisting of fluid nodes and branches and a thermal network consisting of solid nodes and conductors. In the fluid network, the mass, momentum and energy conservation equations are solved and in the thermal network, the energy conservation equation of solids is solved. A pressure-based, finite-volume formulation has been used to solve the equations in the fluid network. The system of equations is solved by a hybrid numerical scheme which solves the mass and momentum conservation equations by a simultaneous Newton-Raphson method and the energy conservation equation by a successive substitution method. The fluid network and thermal network are coupled through heat transfer between the solid and fluid nodes which is computed by Chen's correlation of saturated boiling heat transfer. The computer model is developed using the Generalized Fluid System Simulation Program and the numerical predictions are compared with test data.

Numerical modeling of thermal conductive heating in fractured bedrock.

PubMed

Baston, Daniel P; Falta, Ronald W; Kueper, Bernard H

2010-01-01

Numerical modeling was employed to study the performance of thermal conductive heating (TCH) in fractured shale under a variety of hydrogeological conditions. Model results show that groundwater flow in fractures does not significantly affect the minimum treatment zone temperature, except near the beginning of heating or when groundwater influx is high. However, fracture and rock matrix properties can significantly influence the time necessary to remove all liquid water (i.e., reach superheated steam conditions) in the treatment area. Low matrix permeability, high matrix porosity, and wide fracture spacing can contribute to boiling point elevation in the rock matrix. Consequently, knowledge of these properties is important for the estimation of treatment times. Because of the variability in boiling point throughout a fractured rock treatment zone and the absence of a well-defined constant temperature boiling plateau in the rock matrix, it may be difficult to monitor the progress of thermal treatment using temperature measurements alone. Copyright © 2010 The Author(s). Journal compilation © 2010 National Ground Water Association.

Association of Hospital Spending Intensity With Mortality and Readmission Rates in Ontario Hospitals

PubMed Central

Stukel, Therese A.; Fisher, Elliott S.; Alter, David A.; Guttmann, Astrid; Ko, Dennis T.; Fung, Kinwah; Wodchis, Walter P.; Baxter, Nancy N.; Earle, Craig C.; Lee, Douglas S.

2012-01-01

Context The extent to which better spending produces higher-quality care and better patient outcomes in a universal health care system with selective access to medical technology is unknown. Objective To assess whether acute care patients admitted to higher-spending hospitals have lower mortality and readmissions. Design, Setting, and Patients The study population comprised adults (> 18 years) in Ontario, Canada, with a first admission for acute myocardial infarction (AMI) (n=179 139), congestive heart failure (CHF) (n=92 377), hip fracture (n=90 046), or colon cancer (n=26 195) during 1998–2008, with follow-up to 1 year. The exposure measure was the index hospital’s end-of-life expenditure index for hospital, physician, and emergency department services. Main Outcome Measures The primary outcomes were 30-day and 1-year mortality and readmissions and major cardiac events (readmissions for AMI, angina, CHF, or death) for AMI and CHF. Results Patients’ baseline health status was similar across hospital expenditure groups. Patients admitted to hospitals in the highest- vs lowest-spending intensity terciles had lower rates of all adverse outcomes. In the highest- vs lowest-spending hospitals, respectively, the age- and sex-adjusted 30-day mortality rate was 12.7% vs 12.8% for AMI, 10.2% vs 12.4% for CHF, 7.7% vs 9.7% for hip fracture, and 3.3% vs 3.9% for CHF; fully adjusted relative 30-day mortality rates were 0.93 (95% CI, 0.89–0.98) for AMI, 0.81 (95% CI, 0.76–0.86) for CHF, 0.74 (95% CI, 0.68–0.80) for hip fracture, and 0.78 (95% CI, 0.66–0.91) for colon cancer. Results for 1-year mortality, readmissions, and major cardiac events were similar. Higher-spending hospitals had higher nursing staff ratios, and their patients received more inpatient medical specialist visits, interventional (AMI cohort) and medical (AMI and CHF cohorts) cardiac therapies, preoperative specialty care (colon cancer cohort), and postdischarge collaborative care with a cardiologist and primary care physician (AMI and CHF cohorts). Conclusion Among Ontario hospitals, higher spending intensity was associated with lower mortality, readmissions, and cardiac event rates. PMID:22416099

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yoo, Jun Soo

The bubble departure diameter and bubble release frequency were obtained through the analysis of TAMU subcooled flow boiling experimental data. The numerous images of bubbles at departure were analyzed for each experimental condition to achieve the reliable statistics of the measured bubble parameters. The results are provided in this report with simple discussion.

Numerical Simulation of Tuff Dissolution and Precipitation Experiments: Validation of Thermal-Hydrologic-Chemical (THC) Coupled-Process Modeling

NASA Astrophysics Data System (ADS)

Dobson, P. F.; Kneafsey, T. J.

2001-12-01

As part of an ongoing effort to evaluate THC effects on flow in fractured media, we performed a laboratory experiment and numerical simulations to investigate mineral dissolution and precipitation. To replicate mineral dissolution by condensate in fractured tuff, deionized water equilibrated with carbon dioxide was flowed for 1,500 hours through crushed Yucca Mountain tuff at 94° C. The reacted water was collected and sampled for major dissolved species, total alkalinity, electrical conductivity, and pH. The resulting steady-state fluid composition had a total dissolved solids content of about 140 mg/L; silica was the dominant dissolved constituent. A portion of the steady-state reacted water was flowed at 10.8 mL/hr into a 31.7-cm tall, 16.2-cm wide vertically oriented planar fracture with a hydraulic aperture of 31 microns in a block of welded Topopah Spring tuff that was maintained at 80° C at the top and 130° C at the bottom. The fracture began to seal within five days. A 1-D plug-flow model using the TOUGHREACT code developed at Berkeley Lab was used to simulate mineral dissolution, and a 2-D model was developed to simulate the flow of mineralized water through a planar fracture, where boiling conditions led to mineral precipitation. Predicted concentrations of the major dissolved constituents for the tuff dissolution were within a factor of 2 of the measured average steady-state compositions. The fracture-plugging simulations result in the precipitation of amorphous silica at the base of the boiling front, leading to a hundred-fold decrease in fracture permeability in less than 6 days, consistent with the laboratory experiment. These results help validate the use of the TOUGHREACT code for THC modeling of the Yucca Mountain system. The experiment and simulations indicate that boiling and concomitant precipitation of amorphous silica could cause significant reductions in fracture porosity and permeability on a local scale. The TOUGHREACT code will be used to evaluate larger-scale silica sealing observed in a portion of the Yellowstone geothermal system, a natural analog for the precipitation-experiment processes.

Single-side conduction modeling for high heat flux coolant channels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boyd, R.D. Sr.

In the development of plasma-facing components (PFCs), most investigators have erroneously postulated negligible water critical heat flux dependence on the coolant channel length-to-diameter (L/D) ratio above a constant value of L/D. Although encouraging results have been obtained in characterizing peaking factors for local two-dimensional boiling curves and critical heat flux, additional experimental data and theoretical model development are needed to validate the applicability to PFCs. Both these and related issues will affect the flow boiling correlation and data reduction associated with the development of PFCs for fusion reactors and other physical problems that are dependent on conduction modeling in themore » heat flux spectrum of applications. Both exact solutions and numerical conjugate analyses are presented for a one-side heated (OSH) geometry. The results show (a) the coexistence of three flow regimes inside an OSH circular geometry, (b) the correlational dependence of the inside wall heat flux and temperature, and (c) inaccuracies that could arise in some data reduction procedures.« less

A study of the flow boiling heat transfer in an annular heat exchanger with a mini gap

NASA Astrophysics Data System (ADS)

Musiał, Tomasz; Piasecka, Magdalena; Hożejowska, Sylwia

In this paper the research on flow boiling heat transfer in an annular mini gap was discussed. A one- dimensional mathematical approach was proposed to describe stationary heat transfer in the gap. The mini gap 1 mm wide was created between a metal pipe with enhanced exterior surface and an external tempered glass pipe positioned along the same axis. The experimental test stand consists of several systems: the test loop in which distilled water circulates, the data and image acquisition system and the supply and control system. Known temperature distributions of the metal pipe with enhanced surface and of the working fluid helped to determine, from the Robin boundary condition, the local heat transfer coefficients at the fluid - heated surface contact. In the proposed mathematical model it is assumed that the cylindrical wall is a planar multilayer wall. The numerical results are presented on a chart as function of the heat transfer coefficient along the length of the mini gap.

Analysis of moving surface structures at a laser-induced boiling front

NASA Astrophysics Data System (ADS)

Matti, R. S.; Kaplan, A. F. H.

2014-10-01

Recently ultra-high speed imaging enabled to observe moving wave patterns on metal melts that experience laser-induced boiling. In laser materials processing a vertical laser-induced boiling front governs processes like keyhole laser welding, laser remote fusion cutting, laser drilling or laser ablation. The observed waves originate from temperature variations that are closely related to the melt topology. For improved understanding of the essential front mechanisms and of the front topology, for the first time a deeper systematic analysis of the wave patterns was carried out. Seven geometrical shapes of bright or dark domains were distinguished and categorized, in particular bright peaks of three kinds and dark valleys, often inclined. Two categories describe special flow patterns at the top and bottom of the front. Dynamic and statistical analysis has revealed that the shapes often combine or separate from one category to another when streaming down the front. The brightness of wave peaks typically fluctuates during 20-50 μs. This variety of thermal wave observations is interpreted with respect to the accompanying surface topology of the melt and in turn for governing local mechanisms like absorption, shadowing, boiling, ablation pressure and melt acceleration. The findings can be of importance for understanding the key process mechanisms and for optimizing laser materials processing.

Experimental evidence for blue-shifted hydrogen bonding in the fluoroform-hydrogen chloride complex: a matrix-isolation infrared and ab initio study.

PubMed

Gopi, R; Ramanathan, N; Sundararajan, K

2014-07-24

The 1:1 hydrogen-bonded complex of fluoroform and hydrogen chloride was studied using matrix-isolation infrared spectroscopy and ab initio computations. Using B3LYP and MP2 levels of theory with 6-311++G(d,p) and aug-cc-pVDZ basis sets, the structures of the complexes and their energies were computed. For the 1:1 CHF3-HCl complexes, ab initio computations showed two minima, one cyclic and the other acyclic. The cyclic complex was found to have C-H · · · Cl and C-F · · · H interactions, where CHF3 and HCl sub-molecules act as proton donor and proton acceptor, respectively. The second minimum corresponded to an acyclic complex stabilized only by the C-F · · · H interaction, in which CHF3 is the proton acceptor. Experimentally, we could trap the 1:1 CHF3-HCl cyclic complex in an argon matrix, where a blue-shift in the C-H stretching mode of the CHF3 sub-molecule was observed. To understand the nature of the interactions, Atoms in Molecules and Natural Bond Orbital analyses were carried out to unravel the reasons for blue-shifting of the C-H stretching frequency in these complexes.

First experience of using new adaptive servo-ventilation device for Cheyne-Stokes respiration with central sleep apnea among Japanese patients with congestive heart failure: report of 4 clinical cases.

PubMed

Kasai, Takatoshi; Narui, Koji; Dohi, Tomotaka; Takaya, Hisashi; Yanagisawa, Naotake; Dungan, George; Ishiwata, Sugao; Ohno, Minoru; Ymaguchi, Tetsu; Momomura, Shin-ichi

2006-09-01

Cheyne-Stokes respiration with central sleep apnea (CSR-CSA) in congestive heart failure (CHF) is generally considered a poor prognostic indicator, but treatment of CSR-CSA using an adaptive servo-ventilation (ASV) device has been developed. This is the first evaluation of its use in the management of CSR-CSA in Japanese CHF patients. Four CHF patients with CSR-CSA that was unresponsive to conventional positive airway pressure (CPAP) underwent 3 nights of polysomnography: baseline, CPAP or bi-level PAP, and on the ASV. The apnea - hypopnea index (AHI) and central-AHI (CAHI) were markedly improved on ASV (AHI 62.7+/-10.1 to 5.9+/-2.2 /h, p=0.0006, CAHI 54.5+/-6.7 to 5.6+/-2.3 /h, p=0.007). In addition, the sleep quality improved significantly on ASV, including arousal index (62.0+/-10.5 to 18.7 +/-6.2 /h, p=0.012), percentage of slow-wave sleep (2.6+/-2.6 to 19.4+/-4.8 %, p=0.042). ASV markedly improved CSR-CSA in patients with CHF. It is a promising treatment for Japanese patients with CHF.

Energy transfer of highly vibrationally excited naphthalene: collisions with CHF3, CF4, and Kr.

PubMed

Chen Hsu, Hsu; Tsai, Ming-Tsang; Dyakov, Yuri A; Ni, Chi-Kung

2011-08-07

Energy transfer of highly vibrationally excited naphthalene in the triplet state in collisions with CHF(3), CF(4), and Kr was studied using a crossed-beam apparatus along with time-sliced velocity map ion imaging techniques. Highly vibrationally excited naphthalene (2.0 eV vibrational energy) was formed via the rapid intersystem crossing of naphthalene initially excited to the S(2) state by 266 nm photons. The shapes of the collisional energy-transfer probability density functions were measured directly from the scattering results of highly vibrationally excited naphthalene. In comparison to Kr atoms, the energy transfer in collisions between CHF(3) and naphthalene shows more forward scatterings, larger cross section for vibrational to translational (V → T) energy transfer, smaller cross section for translational to vibrational and rotational (T → VR) energy transfer, and more energy transferred from vibration to translation, especially in the range -ΔE(d) = -100 to -800 cm(-1). On the other hand, the difference of energy transfer properties between collisional partners Kr and CF(4) is small. The enhancement of the V → T energy transfer in collisions with CHF(3) is attributed to the large attractive interaction between naphthalene and CHF(3) (1-3 kcal/mol).

Improved detection of congestive heart failure via probabilistic symbolic pattern recognition and heart rate variability metrics.

PubMed

Mahajan, Ruhi; Viangteeravat, Teeradache; Akbilgic, Oguz

2017-12-01

A timely diagnosis of congestive heart failure (CHF) is crucial to evade a life-threatening event. This paper presents a novel probabilistic symbol pattern recognition (PSPR) approach to detect CHF in subjects from their cardiac interbeat (R-R) intervals. PSPR discretizes each continuous R-R interval time series by mapping them onto an eight-symbol alphabet and then models the pattern transition behavior in the symbolic representation of the series. The PSPR-based analysis of the discretized series from 107 subjects (69 normal and 38 CHF subjects) yielded discernible features to distinguish normal subjects and subjects with CHF. In addition to PSPR features, we also extracted features using the time-domain heart rate variability measures such as average and standard deviation of R-R intervals. An ensemble of bagged decision trees was used to classify two groups resulting in a five-fold cross-validation accuracy, specificity, and sensitivity of 98.1%, 100%, and 94.7%, respectively. However, a 20% holdout validation yielded an accuracy, specificity, and sensitivity of 99.5%, 100%, and 98.57%, respectively. Results from this study suggest that features obtained with the combination of PSPR and long-term heart rate variability measures can be used in developing automated CHF diagnosis tools. Copyright © 2017 Elsevier B.V. All rights reserved.

Heart rate variability enhances the prognostic value of established parameters in patients with congestive heart failure.

PubMed

Krüger, C; Lahm, T; Zugck, C; Kell, R; Schellberg, D; Schweizer, M W F; Kübler, W; Haass, M

2002-12-01

This prospective study evaluated whether heart rate variability (HRV) assessed from Holter ECG has prognostic value in addition to established parameters in patients with congestive heart failure (CHF). The study included 222 patients with CHF due to dilated or ischemic cardiomyopathy (left ventricular ejection fraction LVEF 21+/-1%; mean+/-SEM). During a mean follow-up of 15+/-1 months, 38 (17%) patients died and 45 (20%) were hospitalized due to worsening of CHF. The HRV parameter SDNN (standard deviation of all intervals between normal beats) was significantly lower in non-surviving or hospitalized than in event-free patients (118+/-6 vs 142+/-5 ms), as were LVEF (18+/-1 vs 23+/-1%), and peak oxygen uptake during exercise (peak VO(2)) (12.8+/-0.5 vs 15.6+/-0.5 ml/min/kg). While each of these parameters was a risk predictor in univariate analysis, multivariate analysis revealed that HRV provides both independent and additional prognostic information with respect to the risk 'cardiac mortality or deterioration of CHF'. It is concluded that the determination of HRV enhances the prognostic power given by the most widely used parameters LVEF and peak VO(2) in the prediction of mortality or deterioration of CHF and thus enables to improve risk stratification.

Characteristics associated with mortality in patients with chronic obstructive pulmonary disease (COPD)-heart failure coexistence.

PubMed

Plachi, Franciele; Balzan, Fernanda M; Sanseverino, Renata A; Palombini, Dora V; Marques, Renata D; Clausell, Nadine O; Knorst, Marli M; Neder, J Alberto; Berton, Danilo C

2018-02-21

Aim To investigate if cardiac/pulmonary functional tests and variables obtained from clinical practice (body mass index, dyspnea, functional class, clinical judgment of disability to perform an exercise test and previous hospitalization rate) are related to mortality in patients with overlap chronic obstructive pulmonary disease (COPD) and chronic heart failure (CHF). Although the coexistence of COPD and CHF has been growingly reported, description of survival predictors considering the presence of both conditions is still scarce. Using a cohort design, outpatients with the previous diagnosis of COPD and/or CHF that performed both spirometry and echocardiography in the same year were followed-up during a mean of 20.9±8.5 months. Findings Of the 550 patients initially evaluated, 301 had both spirometry and echocardiography: 160 (53%) with COPD on isolation; 100 (33%) with CHF on isolation; and 41 (14%) with overlap. All groups presented similar mortality: COPD 17/160 (11%); CHF 12/100 (12%); and overlap 7/41 (17%) (P=0.73). In the overlap group (n=41), inability to exercise and hospitalization rate were the unique parameters associated with higher mortality (seven events) in univariate analyses. In conclusion, inability to exercise and hospitalization rate emerged as the unique parameters associated with mortality in our sample.

The Performance of Short-Term Heart Rate Variability in the Detection of Congestive Heart Failure

PubMed Central

Barros, Allan Kardec; Ohnishi, Noboru

2016-01-01

Congestive heart failure (CHF) is a cardiac disease associated with the decreasing capacity of the cardiac output. It has been shown that the CHF is the main cause of the cardiac death around the world. Some works proposed to discriminate CHF subjects from healthy subjects using either electrocardiogram (ECG) or heart rate variability (HRV) from long-term recordings. In this work, we propose an alternative framework to discriminate CHF from healthy subjects by using HRV short-term intervals based on 256 RR continuous samples. Our framework uses a matching pursuit algorithm based on Gabor functions. From the selected Gabor functions, we derived a set of features that are inputted into a hybrid framework which uses a genetic algorithm and k-nearest neighbour classifier to select a subset of features that has the best classification performance. The performance of the framework is analyzed using both Fantasia and CHF database from Physionet archives which are, respectively, composed of 40 healthy volunteers and 29 subjects. From a set of nonstandard 16 features, the proposed framework reaches an overall accuracy of 100% with five features. Our results suggest that the application of hybrid frameworks whose classifier algorithms are based on genetic algorithms has outperformed well-known classifier methods. PMID:27891509

Myogenic constriction is increased in mesenteric resistance arteries from rats with chronic heart failure: instantaneous counteraction by acute AT1 receptor blockade

PubMed Central

Gschwend, S; Henning, R H; Pinto, Y M; de Zeeuw, D; van Gilst, W H; Buikema, H

2003-01-01

Increased vascular resistance in chronic heart failure (CHF) has been attributed to stimulated neurohumoral systems. However, local mechanisms may also importantly contribute to set arterial tone. Our aim, therefore, was to test whether pressure-induced myogenic constriction of resistance arteries in vitro – devoid of acute effects of circulating factors – is increased in CHF and to explore underlying mechanisms. At 12 weeks after coronary ligation-induced myocardial infarction or SHAM-operations in rats, we studied isolated mesenteric arteries for myogenic constriction, determined as the active constriction (% of passive diameter) in response to stepwise increase in intraluminal pressure (20 – 160 mmHg), in the absence and presence of inhibitors of potentially involved modulators of myogenic constriction. We found that myogenic constriction in mesenteric arteries from CHF rats was markedly increased compared to SHAM over the whole pressure range, the difference being most pronounced at 60 mmHg (24±2 versus 4±3%, respectively, P<0.001). Both removal of the endothelium as well as inhibition of NO production (L-NG-monomethylarginine, 100 μM) significantly increased myogenic constriction (+16 and +25%, respectively), the increase being similar in CHF- and SHAM-arteries (P=NS). Neither endothelin type A (ETA)-receptor blockade (BQ123, 1 μM) nor inhibition of perivascular (sympathetic) nerve conduction (tetrodotoxin, 100 nM) affected the myogenic response in either group. Interestingly, increased myogenic constriction in CHF was fully reversed after angiotensin II type I (AT1)-receptor blockade (candesartan, 100 nM; losartan, 10 μM), which was without effect in SHAM. In contrast, neither angiotensin-converting enzyme (ACE) inhibition (lisinopril, 1 μM; captopril, 10 μM) or AT2-receptor blockade (PD123319, 1 μM), nor inhibition of superoxide production (superoxide dismutase, 50 U ml−1), TXA2-receptor blockade (SQ29,548, 1 μM) or inhibition of cyclooxygenase-derived prostaglandins (indomethacin, 10 μM) affected myogenic constriction. Sensitivity of mesenteric arteries to angiotensin II (10 nM – 100 μM) was increased (P<0.05) in CHF (pD2 7.1±0.4) compared to SHAM (pD2 6.2±0.3), while the sensitivity to KCl and phenylephrine was not different. Our results demonstrate increased myogenic constriction in small mesenteric arteries of rats with CHF, potentially making it an important target for therapy in counteracting increased vascular resistance in CHF. Our results further suggest active and instantaneous participation of AT1-receptors in increased myogenic constriction in CHF, involving increased sensitivity of AT1-receptors rather than apparent ACE-mediated local angiotensin II production. PMID:12890711

Prognostic value of systolic mitral annular velocity measured with Doppler tissue imaging in patients with chronic heart failure caused by left ventricular systolic dysfunction

PubMed Central

Nikitin, N P; Loh, P H; de Silva, R; Ghosh, J; Khaleva, O Y; Goode, K; Rigby, A S; Alamgir, F; Clark, A L; Cleland, J G F

2006-01-01

Objective To assess the prognostic value of various conventional and novel echocardiographic indices in patients with chronic heart failure (CHF) caused by left ventricular (LV) systolic dysfunction. Methods 185 patients with a mean (SD) age of 67 (11) years with CHF and LV ejection fraction < 45% despite optimal pharmacological treatment were prospectively enrolled. The patients underwent two dimensional echocardiography with tissue harmonic imaging to assess global LV systolic function and obtain volumetric data. Transmitral flow was assessed with conventional pulse wave Doppler. Systolic (Sm), early, and late diastolic mitral annular velocities were measured with the use of colour coded Doppler tissue imaging. Results During a median follow up of 32 months (range 24–38 months in survivors), 34 patients died and one underwent heart transplantation. Sm velocity (hazard ratio (HR) 0.648, 95% confidence interval (CI) 0.463 to 0.907, p  =  0.011), diastolic arterial pressure (HR 0.965, 95% CI 0.938 to 0.993, p  =  0.015), serum creatinine (HR 1.006, 95% CI 1.001 to 1.011, p  =  0.023), LV ejection fraction (HR 0.945, 95% CI 0.899 to 0.992, p  =  0.024), age (HR 1.035, 95% CI 1.000 to 1.071, p  =  0.052), LV end systolic volume index (HR 1.009, 95% CI 0.999 to 1.019, p  =  0.067), and restrictive pattern of transmitral flow (HR 0.543, 95% CI 0.278 to 1.061, p  =  0.074) predicted the outcome of death or transplantation on univariate analysis. On multivariate analysis, only Sm velocity (HR 0.648, 95% CI 0.460 to 0.912, p  =  0.013) and diastolic arterial pressure (HR 0.966, 95% CI 0.938 to 0.994, p  =  0.016) emerged as independent predictors of outcome. Conclusions In patients with CHF and LV systolic dysfunction despite optimal pharmacological treatment, the strongest independent echocardiographic predictor of prognosis was Sm velocity measured with quantitative colour coded Doppler tissue imaging. PMID:16251233

Passive containment cooling system with drywell pressure regulation for boiling water reactor

DOEpatents

Hill, Paul R.

1994-01-01

A boiling water reactor having a regulating valve for placing the wetwell in flow communication with an intake duct of the passive containment cooling system. This subsystem can be adjusted to maintain the drywell pressure at (or slightly below or above) wetwell pressure after the initial reactor blowdown transient is over. This addition to the PCCS design has the benefit of eliminating or minimizing steam leakage from the drywell to the wetwell in the longer-term post-LOCA time period and also minimizes the temperature difference between drywell and wetwell. This in turn reduces the rate of long-term pressure buildup of the containment, thereby extending the time to reach the design pressure limit.

Collins Cryocooler Design for Zero-Boil Storage of Liquid Hydrogen and Oxygen in Space

NASA Astrophysics Data System (ADS)

Segado, M. A.; Hannon, C. L.; Brisson, J. G.

2010-04-01

Several models of multi-stage cryocoolers are developed for zero-boil-off storage of liquid hydrogen and oxygen in space. The thermodynamic cycles are based on a modified Collins cycle being developed by MIT and AMTI, and each configuration is optimized for maximum efficiency by varying the mass flows, heat exchanger UA distribution, and other variables where applicable, subject to the required heat loads of 100 W at 100 K and 20 W at 25 K. By using double expanders connected in series with the heat loads in one or more stages of the cooler, we were able to achieve predicted efficiency gains of 10-24% over single expander designs.