Parasitic heat loss reduction in AMTEC cells by heat shield optimization

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

Borkowski, C.A.; Svedberg, R.C.; Hendricks, T.J.

1997-12-31

Alkali metal thermal to electric conversion (AMTEC) cell performance can be increased by the proper design of thermal radiative shielding internal to the AMTEC cell. These heat shields essentially lower the radiative heat transfer between the heat input zone of the cell and the heat rejection zone of the cell. In addition to lowering the radiative heat transfer between the heat input and heat rejection surfaces of the cell, the shields raise the AMTEC cell performance by increasing the temperature of the beta alumina solid electrolyte (BASE). This increase in temperature of the BASE tube allows the evaporator temperature tomore » be increased without sodium condensing within the BASE tubes. Experimental testing and theoretical analysis have been performed to compare the relative merits of two candidate heat shield packages: (1) chevron, and (2) cylindrical heat shields. These two heat shield packages were compared to each other and a baseline cell which had no heat shields installed. For the two heat shield packages, the reduction in total heat transfer is between 17--27% for the heat input surface temperature varying from 700 C, 750 C, and 800 C with the heat rejection surface temperature kept at 300 C.« less

Artificial neural network modeling of a deflector in a grooved channel as well as optimization of its effective parameters

NASA Astrophysics Data System (ADS)

Abdollahi, Azita; Shams, Mehrzad; Abdollahi, Anita

2018-01-01

One of methods available to increase the rate of heat transfer in channels with parallel plates is making grooves in them. But, the fundamental problem of this method is the formation of stagnation zone in the grooves and as a result formation a zone with low energy transfer. In this paper, the effect of placing curved deflectors (geometries with elliptical forms) in channel on thermal and hydraulic characteristic of the fluid flow- with the aim of directing of the flow into the grooves and as a result increasing the rate of heat transfer in this zone- are investigated and heat transfer coefficient and pressure drop are calculated for different values of Reynolds number and geometrical parameters of the deflector (its small and large radiuses). The results show that the presence of the deflector in the channel significantly increases the heat transfer rate compare to the channel without deflector. Of course, it should be noted that this work also increases the pressure drop. So, finally in order to determine configurations of the deflector causing minimum pressure drop, maximum Nusselt number or a balance between them, optimization algorithm consisting of artificial neural network and multi-objective genetic algorithm was utilized to calculate the optimal values of these parameters.

Experimental study on the heat transfer characteristics of waste printed circuit boards pyrolysis.

PubMed

Ma, Hongting; Du, Na; Lin, Xueyin; Li, Chen; Lai, Junwen; Li, Zihao

2018-08-15

In order to study the appropriate and advanced technology for recycling waste printed circuit boards (PCBs), a fixed bed pyrolysis device with stirring function has been designed and developed. The effect of rotating speed on the temperature distribution and mass change in the pyrolysis process of FR-4 PCB has been analyzed. The heat transfer and pyrolysis characteristics of different granular layers with and without stirring have been investigated. The results indicate that the stirring can change the main way of heat transfer from conduction to convection in the PCB layers. As the increase of rotating speed, the temperature rising rate of material at the bottom of the pyrolysis furnace gradually decreases, while the heating rate is increasing at the upper layer, and the temperature difference between the upper and bottom layers is gradually reduced. When the rotating speed varies from 0r/min to 18r/min, the weight loss of the material increases from 3.97% to 6.76%, and the overall pyrolysis degree is improved. During the pyrolysis process, the material layer can be divided into three zones along the vertical direction, namely complete pyrolysis zone, partial pyrolysis zone and non-pyrolysis zone. As the rotating speed is 0r/min, the thickness of each zones is 6cm, 6cm and 3cm, respectively. However, when the rotating speed is increased to 18r/min, the non-pyrolysis zone disappears, and the thickness of complete pyrolysis zone and partial pyrolysis zone increase to 9cm and 6cm, respectively. Copyright © 2018 Elsevier B.V. All rights reserved.

Thermocapillary flow and melt/solid interfaces in floating-zone crystal growth under microgravity

NASA Technical Reports Server (NTRS)

Lan, C. W.; Kou, Sindo

1990-01-01

Computer simulation of steady-state axisymmetrical heat transfer and fluid flow was conducted to study thermocapillary flow and melt/solid interfaces in floating-zone crystal growth under microgravity. The effects of key variables on the extent of thermocapillary flow in the melt zone, the shapes of melt/solid interfaces and the length of the melt zone were discussed. These variables are: (1) the temperature coefficient of surface tension (or the Marangoni number), (2) the pulling speed (or the Peclet number), (3) the feed rod radius, (4) the ambient temperature distribution, (5) the heat transfer coefficient (or the Biot number), and (6) the thermal diffusivity of the material (or the Prandtl number).

The numerical simulation of heat transfer during a hybrid laser-MIG welding using equivalent heat source approach

NASA Astrophysics Data System (ADS)

Bendaoud, Issam; Matteï, Simone; Cicala, Eugen; Tomashchuk, Iryna; Andrzejewski, Henri; Sallamand, Pierre; Mathieu, Alexandre; Bouchaud, Fréderic

2014-03-01

The present study is dedicated to the numerical simulation of an industrial case of hybrid laser-MIG welding of high thickness duplex steel UR2507Cu with Y-shaped chamfer geometry. It consists in simulation of heat transfer phenomena using heat equivalent source approach and implementing in finite element software COMSOL Multiphysics. A numerical exploratory designs method is used to identify the heat sources parameters in order to obtain a minimal required difference between the numerical results and the experiment which are the shape of the welded zone and the temperature evolution in different locations. The obtained results were found in good correspondence with experiment, both for melted zone shape and thermal history.

Numerical simulations of inductive-heated float-zone growth

NASA Technical Reports Server (NTRS)

Chan, Y. T.; Choi, S. K.

1992-01-01

The present work provides an improved fluid flow and heat-transfer modeling of float-zone growth by introducing a RF heating model so that an ad hoc heating temperature profile is not necessary. Numerical simulations were carried out to study the high-temperature float-zone growth of titanium carbide single crystal. The numerical results showed that the thermocapillary convection occurring inside the molten zone tends to increase the convexity of the melt-crystal interface and decrease the maximum temperature of the molten zone, while the natural convection tends to reduce the stability of the molten zone by increasing its height. It was found that the increase of induced heating due to the increase of applied RF voltage is reduced by the decrease of zone diameter. Surface tension plays an important role in controlling the amount of induced heating. Finally, a comparison of the computed shape of the free surface with a digital image obtained during a growth run showed adequate agreement.

Particle dispersion and turbulence modification in a dilute mist non-isothermal turbulent flow downstream of a sudden pipe expansion

NASA Astrophysics Data System (ADS)

Terekhov, V. I.; Pakhomov, M. A.

2011-12-01

Flow, particles dispersion and heat transfer of dilute gas-droplet turbulent flow downstream of a pipe sudden expansion have been numerically investigated for the conditions of heated dry wall. An Euler two-fluid model with additional turbulence transport equations for gas and particulate phases was employed in the study. Gas phase turbulence was modelled using the elliptic blending Reynolds stress model of Fadai-Ghotbi et al. (2008). Two-way coupling is achieved between the dispersed and carrier phases. The partial equations of Reynolds stresses and temperature fluctuations, and the turbulent heat flux equations in dispersed phase by Zaichik (1999) were applied. Fine droplets get readily entrained with the detached flow, spread throughout the whole pipe cross-section. On the contrary, large particles, due to their inertia, do not appear in the recirculation zone and are presented only in the shear layer region. The presence of fine dispersed droplets in the flow attenuates the gas phase turbulence of up 25 %. Heat transfer in the mist flow increased (more than twice in comparison with the single-phase air flow). Intensification of heat transfer is observed both in the recirculation zone and flow development region in the case of fine particles. Large particles enhanced heat transfer only in the reattachment zone. Comparison between simulated results and experimental data of Hishida et al. (1995) for mist turbulent separated flow behind a backward-facing step shows quite good agreement.

Heat transfer Effect by soil temperature changes under shallow groundwater in the Mu Us desert, Northern China

NASA Astrophysics Data System (ADS)

Qiao, X.; Lu, R.; Donghui, C.

2015-12-01

Soil temperature change is principle elements to biological growth, soil freeze or thawing process. A situ field was conducted in the Mu Us desert of Wushen Qi County, Inner Mongolia, to mainly monitor soil temperature, moisture content and groundwater level. The unconfined aquifer constituted by Quaternary fine eolian sand, groundwater level is 125cm. This paper, choosing date from May 1, 2013 to April 30, 2014, soil day temperature is conducted by 3:00, 6:00,till 24:00, vertical spacing including 2cm,5 cm、10 cm、15 cm、20 cm, 75cm,125cm,which its symbol is T10, T15, T20, T75, T125 respectively. Here, surface layer temperature TS calculated by soil temperature of 2-5cm depth. Due to only 5 minutes interval, this state was taken as a state one. (1) soil temperature has mixture change on surface layer and its temperature different is over 35 ℃. (2) Surface layer temperature changes of every month have three stages and its conducted heat, which calculated between TS and T10. Since TS exceeds T10 and heat transfer direction is from surface to underground in May, June and July 2013, even heat transfer amounts reduced by participation in July. However, TS is inferior to T10 and conduced heat direction reverse in August till to February 2014.Continually conduced heat start to next circulation and then it's heat direction from surface to underground due to TS exceeds T10 again in March and April 2014. (3) Temperature changes of phreatic water table every month have also three stages and its conducted heat which calculated between T75 and T125, heat transfer direction from unsaturated zone to saturated zone due to T75 exceeds T125 from May till middle September 2013. However, T75 is inferior to T125 and heat direction reverse from late September 2013 till May 2014, but conduced heat direction starts to change from unsaturated zone to saturated zone again in early April 2014.The result can imply shallow gruondwater has some contribution to surface layer temperature in different seasons.

Aerodynamic and heat transfer analysis of the low aspect ratio turbine using a 3D Navier-Stokes code

NASA Astrophysics Data System (ADS)

Choi, D.; Knight, C. J.

1991-06-01

The single-stage, high-pressure ratio Garrett Low Aspect Ratio Turbine (LART) test data obtained in a shock tunnel are employed as a basis for evaluating a new three-dimensional Navier Stokes code based on the O-H grid system. It uses Coakley's two-equation turbulence modeling with viscous sublayer resolution. For the nozzle guide vanes, calculations were made based on two grid zones: an O-grid zone wrapping around airfoil and an H-grid zone outside of the O-grid zone, including the regions upstream of the leadig edge and downstream of the trailing edge. For the rotor blade row, a third O-grid zone was added for the tip-gap region leakage flow. The computational results compare well with experiment. These comparisons include heat transfer distributions on the airfoils and end-walls. The leakage flow through the tip-gap clearance is well resolved.

The human thermoneutral and thermal comfort zones: Thermal comfort in your own skin blood flow.

PubMed

Schlader, Zachary J

2015-01-01

Human thermoregulation is achieved via autonomic and behavioral responses. Autonomic responses involve 2 synchronous 'components'. One counteracts large thermal perturbations, eliciting robust heat loss or gain (i.e., sweating or shivering). The other fends off smaller insults, relying solely on changes in sensible heat exchange (i.e., skin blood flow). This sensible component occurs within the thermoneutral zone [i.e., the ambient temperature range in which temperature regulation is achieved only by sensible heat transfer, without regulatory increases in metabolic heat production (e.g., shivering) or evaporative heat loss (e.g., sweating)].(1) The combination of behavior and sensible heat exchange permits a range of conditions that are deemed thermally comfortable, which is defined as the thermal comfort zone.(1) Notably, we spend the majority of our lives within the thermoneutral and thermal comfort zones. It is only when we are unable to stay within these zones that deleterious health and safety outcomes can occur (i.e., hypo- or hyperthermia). Oddly, although the thermoneutral zone and thermal preference (a concept similar to the thermal comfort zone) has been extensively studied in non-human animals, our understanding of human thermoregulation within the thermoneutral and thermal comfort zones remains rather crude.

Tower reactors for bioconversion of lignocellulosic material

DOEpatents

Nguyen, Quang A.

1999-01-01

An apparatus for enzymatic hydrolysis and fermentation of pretreated lignocellulosic material, in the form of a tower bioreactor, having mixers to achieve intermittent mixing of the material. Precise mixing of the material is important for effective heat and mass transfer requirements without damaging or denaturing the enzymes or fermenting microorganisms. The pretreated material, generally in the form of a slurry, is pumped through the bioreactor, either upwards or downwards, and is mixed periodically as it passes through the mixing zones where the mixers are located. For a thin slurry, alternate mixing can be achieved by a pumping loop which also serves as a heat transfer device. Additional heat transfer takes place through the reactor heat transfer jackets.

Tower reactors for bioconversion of lignocellulosic material

DOEpatents

Nguyen, Quang A.

1998-01-01

An apparatus for enzymatic hydrolysis and fermentation of pretreated lignocellulosic material, in the form of a tower bioreactor, having mixers to achieve intermittent mixing of the material. Precise mixing of the material is important for effective heat and mass transfer requirements without damaging or denaturing the enzymes or fermenting microorganisms. The pretreated material, generally in the form of a slurry, is pumped through the bioreactor, either upwards of downwards, and is mixed periodically as it passes through the mixing zones where the mixers are located. For a thin slurry, alternate mixing can be achieved by a pumping loop which also serves as a heat transfer device. Additional heat transfer takes place through the reactor heat transfer jackets.

Local heat transfer in turbine disk-cavities. I - Rotor and stator cooling with hub injection of coolant

NASA Astrophysics Data System (ADS)

Bunker, R. S.; Metzger, D. E.; Wittig, S.

1990-06-01

Detailed radial heat-transfer coefficient distributions applicable to the cooling of disk-cavity regions of gas turbines are obtained experimentally from local heat-transfer data on both the rotating and stationary surfaces of a parallel-geometry disk-cavity system. Attention is focused on the hub injection of a coolant over a wide range of parameters including disk rotational Reynolds numbers of 200,000 to 50,000, rotor/stator spacing-to-disk ratios of 0.025 to 0.15, and jet mass flow rates between 0.10 and 0.40 times the turbulent pumped flow rate of a free disk. It is shown that rotor heat transfer exhibits regions of impingement and rotational domination with a transition region between, while stator heat transfer displays flow reattachment and convection regions with an inner recirculation zone.

Heat Transfer Search Algorithm for Non-convex Economic Dispatch Problems

NASA Astrophysics Data System (ADS)

Hazra, Abhik; Das, Saborni; Basu, Mousumi

2018-06-01

This paper presents Heat Transfer Search (HTS) algorithm for the non-linear economic dispatch problem. HTS algorithm is based on the law of thermodynamics and heat transfer. The proficiency of the suggested technique has been disclosed on three dissimilar complicated economic dispatch problems with valve point effect; prohibited operating zone; and multiple fuels with valve point effect. Test results acquired from the suggested technique for the economic dispatch problem have been fitted to that acquired from other stated evolutionary techniques. It has been observed that the suggested HTS carry out superior solutions.

Heat Transfer Search Algorithm for Non-convex Economic Dispatch Problems

NASA Astrophysics Data System (ADS)

Hazra, Abhik; Das, Saborni; Basu, Mousumi

2018-03-01

This paper presents Heat Transfer Search (HTS) algorithm for the non-linear economic dispatch problem. HTS algorithm is based on the law of thermodynamics and heat transfer. The proficiency of the suggested technique has been disclosed on three dissimilar complicated economic dispatch problems with valve point effect; prohibited operating zone; and multiple fuels with valve point effect. Test results acquired from the suggested technique for the economic dispatch problem have been fitted to that acquired from other stated evolutionary techniques. It has been observed that the suggested HTS carry out superior solutions.

Conjugate heat transfer of a finned tube. Part B: Heat transfer augmentation and avoidance of heat transfer reversal by longitudinal vortex generators

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

Fiebig, M.; Chen, Y.; Grosse-Gorgemann, A.

1995-08-01

Numerical investigations of three-dimensional flow and heat transfer in a finned tube with punched longitudinal vortex generators (LVG`s) are carried out for Reynolds number of 250 and 300. Air with a Prandtl number of 0.7 is used as the fluid. The flow is both thermally and hydrodynamically developing. The LVG is a delta winglet pair (DWP) punched out of the fin and is located directly behind the tube, symmetrically separated by one tube diameter. The DWP generates longitudinal vortices in the wake of the tube, defers flow separation on the tube, deflects the main stream into the tube wake, andmore » strong reduces the ``dead water zone.`` Heat transfer reversal is avoided by the DWP. Comparison of the span-averaged Nusselt numbers for the fin with and without DWP shows significant local heat transfer enhancement of several hundred percent in the tube wake. For Re = 300 and Fi = 200 the global heat transfer augmentation by a DWP, which amounts to only 2.5% of the fin area, is 31%.« less

HEAT AND MASS TRANSFER IN THE VADOSE ZONE WITH PLANT ROOTS. (R825414)

EPA Science Inventory

Abstract

The vadose zone is the intermediate medium between the atmosphere and groundwater. The modeling of the processes taking place in the vadose zone needs different approaches to those needed for groundwater transport problems because of the marked changes in envi...

Tower reactors for bioconversion of lignocellulosic material

DOEpatents

Nguyen, Q.A.

1998-03-31

An apparatus is disclosed for enzymatic hydrolysis and fermentation of pretreated lignocellulosic material. The apparatus consists of a tower bioreactor which has mixers to achieve intermittent mixing of the material. Precise mixing of the material is important for effective heat and mass transfer requirements without damaging or denaturing the enzymes or fermenting microorganisms. The pretreated material, generally in the form of a slurry, is pumped through the bioreactor, either upwards or downwards, and is mixed periodically as it passes through the mixing zones where the mixers are located. For a thin slurry, alternate mixing can be achieved by a pumping loop which also serves as a heat transfer device. Additional heat transfer takes place through the reactor heat transfer jackets. 5 figs.

Tower reactors for bioconversion of lignocellulosic material

DOEpatents

Nguyen, Q.A.

1999-03-30

An apparatus is described for enzymatic hydrolysis and fermentation of pretreated lignocellulosic material, in the form of a tower bioreactor, having mixers to achieve intermittent mixing of the material. Precise mixing of the material is important for effective heat and mass transfer requirements without damaging or denaturing the enzymes or fermenting microorganisms. The pretreated material, generally in the form of a slurry, is pumped through the bioreactor, either upwards or downwards, and is mixed periodically as it passes through the mixing zones where the mixers are located. For a thin slurry, alternate mixing can be achieved by a pumping loop which also serves as a heat transfer device. Additional heat transfer takes place through the reactor heat transfer jackets. 5 figs.

Critical Evaluation of State-of-the-Art In Situ Thermal Treatment Technologies for DNAPL Source Zone Treatment. State-of-the-Practice Overview

DTIC Science & Technology

2009-05-01

recovery in their design. Electrodes have been constructed from steel pipe , copper plate for heating distinct zones, and sheet pile. Sheet pile...energy transfer/ heating in the subsurface) The components required to implement ERH include: • Electrodes (steel pipe , copper plate, well points...including piping , blower, and condenser • A vapor treatment system Electrical Resistance Heating (Smith) A-3 • An ERH power control unit to

Production from multiple zones of a tar sands formation

DOEpatents

Karanikas, John Michael; Vinegar, Harold J

2013-02-26

A method for treating a tar sands formation includes providing heat to at least part of a hydrocarbon layer in the formation from a plurality of heaters located in the formation. The heat is allowed to transfer from the heaters to at least a portion of the formation. Fluids are produced from the formation through at least one production well that is located in at least two zones in the formation. The first zone has an initial permeability of at least 1 darcy. The second zone has an initial of at most 0.1 darcy. The two zones are separated by a substantially impermeable barrier.

The human thermoneutral and thermal comfort zones: Thermal comfort in your own skin blood flow

PubMed Central

Schlader, Zachary J

2015-01-01

Human thermoregulation is achieved via autonomic and behavioral responses. Autonomic responses involve 2 synchronous ‘components’. One counteracts large thermal perturbations, eliciting robust heat loss or gain (i.e., sweating or shivering). The other fends off smaller insults, relying solely on changes in sensible heat exchange (i.e., skin blood flow). This sensible component occurs within the thermoneutral zone [i.e., the ambient temperature range in which temperature regulation is achieved only by sensible heat transfer, without regulatory increases in metabolic heat production (e.g., shivering) or evaporative heat loss (e.g., sweating)].1 The combination of behavior and sensible heat exchange permits a range of conditions that are deemed thermally comfortable, which is defined as the thermal comfort zone.1 Notably, we spend the majority of our lives within the thermoneutral and thermal comfort zones. It is only when we are unable to stay within these zones that deleterious health and safety outcomes can occur (i.e., hypo- or hyperthermia). Oddly, although the thermoneutral zone and thermal preference (a concept similar to the thermal comfort zone) has been extensively studied in non-human animals, our understanding of human thermoregulation within the thermoneutral and thermal comfort zones remains rather crude. PMID:27226992

Control of heat transfer in continuous-feeding Czochralski-silicon crystal growth with a water-cooled jacket

NASA Astrophysics Data System (ADS)

Zhao, Wenhan; Liu, Lijun

2017-01-01

The continuous-feeding Czochralski method is an effective method to reduce the cost of single crystal silicon. By promoting the crystal growth rate, the cost can be reduced further. However, more latent heat will be released at the melt-crystal interface under a high crystal growth rate. In this study, a water-cooled jacket was applied to enhance the heat transfer at the melt-crystal interface. Quasi-steady-state numerical calculation was employed to investigate the impact of the water-cooled jacket on the heat transfer at the melt-crystal interface. Latent heat released during the crystal growth process at the melt-crystal interface and absorbed during feedstock melting at the feeding zone was modeled in the simulations. The results show that, by using the water-cooled jacket, heat transfer in the growing crystal is enhanced significantly. Melt-crystal interface deflection and thermal stress increase simultaneously due to the increase of radial temperature at the melt-crystal interface. With a modified heat shield design, heat transfer at the melt-crystal interface is well controlled. The crystal growth rate can be increased by 20%.

Mushy zone modeling

NASA Astrophysics Data System (ADS)

Glicksman, Martin E.; Smith, Richard N.; Marsh, Steven P.; Kuklinski, Robert

A key element of mushy zone modeling is the description of the microscopic evolution of the lengthscales within the mushy zone and the influence of macroscopic transport processes. This paper describes some recent progress in developing a mean-field statistical theory of phase coarsening in adiabatic mushy zones. The main theoretical predictions are temporal scaling laws that indicate that average lengthscale increases as time 1/3, a self-similar distribution of mushy zone lengthscales based on spherical solid particle shapes, and kinetic rate constants which provide the dependences of the coarsening process on material parameters and the volume fraction of the solid phase. High precision thermal decay experiments are described which verify aspects of the theory in pure material mushy zones held under adiabatic conditions. The microscopic coarsening theory is then integrated within a macroscopic heat transfer model of one-dimensional alloy solidification, using the Double Integral Method. The method demonstrates an ability to predict the influence of macroscopic heat transfer on the evolution of primary and secondary dendrite arm spacings in Al-Cu alloys. Finally, some suggestions are made for future experimental and theoretical studies required in developing comprehensive solidification processing models.

Interstitial hyperthermia treatment of countercurrent vascular tissue: a comparison of Pennes, WJ and porous media bioheat models.

PubMed

Hassanpour, Saied; Saboonchi, Ahmad

2014-12-01

Development of appropriate heat transfer models to investigate the thermal behavior of living tissues has become increasingly important in simulations of cancer hyperthermia. In this paper, a review is initially presented of the more important general models developed for heat transfer description of perfused tissues. Comparisons are then made between Pennes' simplified Weinbaum and Jiji "WJ" and the more recent porous media "PM" bioheat models. For this purpose, a mathematical model is developed for the heat transfer in a cylindrical medium containing parallel counter-current pairs of small vessels with characteristics as much as possible similar to those of living tissues. The validity of the models is examined and confirmed using the Pennes in vivo experiments and one-dimensional analytical solutions. For consideration of interstitial hyperthermia treatment the smaller cylindrical zone with typical heat generation, is assumed in the center of the main cylinder. The numerical simulation results revealed that, despite difference in temperature distributions calculated by these three models at normal condition, the heat affected zone at hyperthermic condition predicted by all three models are similar. Copyright © 2014 Elsevier Ltd. All rights reserved.

Two-phase flows and heat transfer within systems with ambient pressure above the thermodynamic critical pressure

NASA Technical Reports Server (NTRS)

Hendricks, R. C.; Braun, M. J.; Mullen, R. L.

1986-01-01

In systems where the design inlet and outlet pressures P sub amb are maintained above the thermodynamic critical pressure P sub c, it is often assumed that heat and mass transfer are governed by single-phase relations and that two-phase flows cannot occur. This simple rule of thumb is adequate in many low-power designs but is inadequate for high-performance turbomachines, boilers, and other systems where two-phase regions can exist even though P sub amb P sub c. Heat and mass transfer and rotordynamic-fluid-mechanic restoring forces depend on momentum differences, and those for a two-phase zone can differ significantly from those for a single-phase zone. By using a laminar, variable-property bearing code and a rotating boiler code, pressure and temperature surfaces were determined that illustrate nesting of a two-phase region within a supercritical pressure region. The method of corresponding states is applied to bearings with reasonable rapport.

Two-phase flows and heat transfer within systems with ambient pressure above the thermodynamic critical pressure

NASA Technical Reports Server (NTRS)

Hendricks, R. C.; Braun, M. J.; Mullen, R. L.

1986-01-01

In systems where the design inlet and outlet pressure P sub amb are maintained above the thermodynamic critical pressure P sub c, it is often assumed that heat and mass transfer are governed by single-phase relations and that two-phase flows cannot occur. This simple rule of thumb is adequate in many low-power designs but is inadequate for high-performance turbomachines, boilers, and other systems where two-phase regions can exist even though P sub amb P sub c. Heat and mass transfer and rotordynamic-fluid-mechanic restoring forces depend on momentum differences, and those for a two-phase zone can differ significantly from those for a single-phase zone. By using a laminar, variable-property bearing code and a rotating boiler code, pressure and temperature surfaces were determined that illustrate nesting of a two-phase region within a supercritical pressure region. The method of corresponding states is applied to bearings with reasonable rapport.

Revisiting concepts of thermal physiology: Predicting responses of mammals to climate change.

PubMed

Mitchell, Duncan; Snelling, Edward P; Hetem, Robyn S; Maloney, Shane K; Strauss, Willem Maartin; Fuller, Andrea

2018-02-26

The accuracy of predictive models (also known as mechanistic or causal models) of animal responses to climate change depends on properly incorporating the principles of heat transfer and thermoregulation into those models. Regrettably, proper incorporation of these principles is not always evident. We have revisited the relevant principles of thermal physiology and analysed how they have been applied in predictive models of large mammals, which are particularly vulnerable, to climate change. We considered dry heat exchange, evaporative heat transfer, the thermoneutral zone and homeothermy, and we examined the roles of size and shape in the thermal physiology of large mammals. We report on the following misconceptions in influential predictive models: underestimation of the role of radiant heat transfer, misassignment of the role and misunderstanding of the sustainability of evaporative cooling, misinterpretation of the thermoneutral zone as a zone of thermal tolerance or as a zone of sustainable energetics, confusion of upper critical temperature and critical thermal maximum, overestimation of the metabolic energy cost of evaporative cooling, failure to appreciate that the current advantages of size and shape will become disadvantageous as climate change advances, misassumptions about skin temperature and, lastly, misconceptions about the relationship between body core temperature and its variability with body mass in large mammals. Not all misconceptions invalidate the models, but we believe that preventing inappropriate assumptions from propagating will improve model accuracy, especially as models progress beyond their current typically static format to include genetic and epigenetic adaptation that can result in phenotypic plasticity. © 2018 The Authors. Journal of Animal Ecology © 2018 British Ecological Society.

A New Methodology for Turbulence Modelers Using DNS Database Analysis

NASA Technical Reports Server (NTRS)

Parneix, S.; Durbin, P.

1996-01-01

Many industrial applications in such fields as aeronautical, mechanical, thermal, and environmental engineering involve complex turbulent flows containing global separations and subsequent reattachment zones. Accurate prediction of this phenomena is very important because separations influence the whole fluid flow and may have an even bigger impact on surface heat transfer. In particular, reattaching flows are known to be responsible for large local variations of the local wall heat transfer coefficient as well as modifying the overall heat transfer. For incompressible, non-buoyant situations, the fluid mechanics have to be accurately predicted in order to have a good resolution of the temperature field.

Numerical modeling of heat transfer and pasteurizing value during thermal processing of intact egg.

PubMed

Abbasnezhad, Behzad; Hamdami, Nasser; Monteau, Jean-Yves; Vatankhah, Hamed

2016-01-01

Thermal Pasteurization of Eggs, as a widely used nutritive food, has been simulated. A three-dimensional numerical model, computational fluid dynamics codes of heat transfer equations using heat natural convection, and conduction mechanisms, based on finite element method, was developed to study the effect of air cell size and eggshell thickness. The model, confirmed by comparing experimental and numerical results, was able to predict the temperature profiles, the slowest heating zone, and the required heating time during pasteurization of intact eggs. The results showed that the air cell acted as a heat insulator. Increasing the air cell volume resulted in decreasing of the heat transfer rate, and the increasing the required time of pasteurization (up to 14%). The findings show that the effect on thermal pasteurization of the eggshell thickness was not considerable in comparison to the air cell volume.

Influence of a Simple Heat Loss Profile on a Pure Diffusion Flame

NASA Technical Reports Server (NTRS)

Ray, Anjan; Wichman, Indrek S.

1996-01-01

The presence of soot on the fuel side of a diffusion flame results in significant radiative heat losses. The influence of a fuel side heat loss zone on a pure diffusion flame established between a fuel and an oxidizer wall is investigated by assuming a hypothetical sech(sup 2) heat loss profile. The intensity and width of the loss zone are parametrically varied. The loss zone is placed at different distances from the Burke-Schumann flame location. The migration of the temperature and reactivity peaks are examined for a variety of situations. For certain cases the reaction zone breaks through the loss zone and relocates itself on the fuel side of the loss zone. In all cases the temperature and reactivity peaks move toward the fuel side with increased heat losses. The flame structure reveals that the primary balance for the energy equation is between the reaction term and the diffusion term. Extinction plots are generated for a variety of situations. The heat transfer from the flame to the walls and the radiative fraction is also investigated, and an analytical correlation formula, derived in a previous study, is shown to produce excellent predictions of our numerical results when an O(l) numerical multiplicative constant is employed.

How Many Convective Zones Are There in the Atmosphere of Venus?

NASA Astrophysics Data System (ADS)

Moroz, V. I.; Rodin, A. V.

2002-11-01

The qualitative characteristics of the vertical structure of the atmospheres of Venus and the Earth essentially differ. For instance, there are at least two, instead of one, zones with normal (thermal) convection on Venus. The first one is near the surface (a boundary layer); the second is at the altitudes of the lower part of the main cloud layer between 49 and 55 km. Contrary to the hypotheses proposed by Izakov (2001, 2002), the upper convective zone prevents energy transfer from the upper clouds to the subcloud atmosphere by ``anomalous turbulent heat conductivity.'' It is possible, however, that the anomalous turbulent heat conductivity takes part in the redistribution of the heat fluxes within the lower (subcloud) atmosphere.

Numerical Simulation of the Thermal Process in a W-Shape Radiant Tube Burner

NASA Astrophysics Data System (ADS)

Wang, Yi; Li, Jiyong; Zhang, Lifeng; Ling, Haitao; Li, Yanlong

2014-07-01

In the current work, three-dimensional mathematical models were developed for the heat transfer and combustion in a W-shape radiant tube burner (RTB) and were solved using Fluent software (ANSYS Inc., Canonsburg, PA). The standard k- ɛ model, nonpremixed combustion model, and the discrete ordinate model were used for the modeling of turbulence, combustion, and radiant heat transfer, respectively. In addition, the NO x postprocessor was used for the prediction of the NO emission. A corresponding experiment was performed for the validation of mathematical models. The details of fluid flow, heat transfer, and combustion in the RTB were investigated. Moreover, the effect of the air/fuel ratio (A/F) and air staging on the performance of RTB was studied with the reference indexes including heat efficiency, maximum temperature difference on shell wall, and NO emission at the outlet. The results indicated that a low speed zone formed in the vicinity of the combustion chamber outlet, and there were two relative high-temperature zones in the RTB, one in combustion chamber that favored the flame stability and the other from the main flame in the RTB. The maximum temperature difference was 95.48 K. As the A/F increased, the temperature increased first and then decreased. As the ratio of the primary to secondary air increased, the recirculation zone at the outlet of combustion chamber shrank gradually to disappear, and the flame length was longer and the temperature in flame decreased correspondingly.

Percolation induced heat transfer in deep unsaturated zones

USGS Publications Warehouse

Lu, N.; LeCain, G.D.

2003-01-01

Subsurface temperature data from a borehole located in a desert wash were measured and used to delineate the conductive and advective heat transfer regimes, and to estimate the percolation quantity associated with the 1997-1998 El Ni??no precipitation. In an arid environment, conductive heat transfer dominates the variation of shallow subsurface temperature most of the time, except during sporadic precipitation periods. The subsurface time-varying temperature due to conductive heat transfer is highly correlated with the surface atmospheric temperature variation, whereas temperature variation due to advective heat transfer is strongly correlated with precipitation events. The advective heat transfer associated with precipitation and infiltration is the focus of this paper. Disruptions of the subsurface conductive temperature regime, associated with the 1997-1998 El Ni??no precipitation, were detected and used to quantify the percolation quantity. Modeling synthesis using a one-dimensional coupled heat and unsaturated flow model indicated that a percolation per unit area of 0.7 to 1.3 m height of water in two weeks during February 1998 was responsible for the observed temperature deviations down to a depth of 35.2 m. The reported study demonstrated quantitatively, for the first time, that the near surface temperature variation due to advective heat transfer can be significant at a depth greater than 10 m in unsaturated soils and can be used to infer the percolation amount in thick unsaturated soils.

Thermal modeling of grinding for process optimization and durability improvements

NASA Astrophysics Data System (ADS)

Hanna, Ihab M.

Both thermal and mechanical aspects of the grinding process are investigated in detail in an effort to predict grinding induced residual stresses. An existing thermal model is used as a foundation for computing heat partitions and temperatures in surface grinding. By numerically processing data from IR temperature measurements of the grinding zone; characterizations are made of the grinding zone heat flux. It is concluded that the typical heat flux profile in the grinding zone is triangular in shape, supporting this often used assumption found in the literature. Further analyses of the computed heat flux profiles has revealed that actual grinding zone contact lengths exceed geometric contact lengths by an average of 57% for the cases considered. By integrating the resulting heat flux profiles; workpiece energy partitions are computed for several cases of dry conventional grinding of hardened steel. The average workpiece energy partition for the cases considered was 37%. In an effort to more accurately predict grinding zone temperatures and heat fluxes, refinements are made to the existing thermal model. These include consideration of contact length extensions due to local elastic deformations, variations of the assumed contact area ratio as a function of grinding process parameters, consideration of coolant latent heat of vaporization and its effect on heat transfer beyond the coolant boiling point, and incorporation of coolant-workpiece convective heat flux effects outside the grinding zone. The result of the model refinements accounting for contact length extensions and process-dependant contact area ratios is excellent agreement with IR temperature measurements over a wide range of grinding conditions. By accounting for latent heat of vaporization effects, grinding zone temperature profiles are shown to be capable of reproducing measured profiles found in the literature for cases on the verge of thermal surge conditions. Computed peak grinding zone temperatures for the aggressive grinding examples given are 30--50% lower than those computed using the existing thermal model formulation. By accounting for convective heat transfer effects outside the grinding zone, it is shown that while surface temperatures in the wake of the grinding zone may be significantly affected under highly convective conditions, computed residual stresses are less sensitive to such conditions. Numerical models are used to evaluate both thermally and mechanically induced stress fields in an elastic workpiece, while finite element modeling is used to evaluate residual stresses for workpieces with elastic-plastic material properties. Modeling of mechanical interactions at the local grit-workpiece length scale is used to create the often measured effect of compressive surface residual stress followed by a subsurface tensile peak. The model is shown to be capable of reproducing trends found in the literature of surface residual stresses which are compressive for low temperature grinding conditions, with surface stresses increasing linearly and becoming tensile with increasing temperatures. Further modifications to the finite element model are made to allow for transiently varying inputs for more complicated grinding processes of industrial components such as automotive cam lobes.

Flow in Rotating Serpentine Coolant Passages With Skewed Trip Strips

NASA Technical Reports Server (NTRS)

Tse, David G.N.; Steuber, Gary

1996-01-01

Laser velocimetry was utilized to map the velocity field in serpentine turbine blade cooling passages with skewed trip strips. The measurements were obtained at Reynolds and Rotation numbers of 25,000 and 0.24 to assess the influence of trips, passage curvature and Coriolis force on the flow field. The interaction of the secondary flows induced by skewed trips with the passage rotation produces a swirling vortex and a corner recirculation zone. With trips skewed at +45 deg, the secondary flows remain unaltered as the cross-flow proceeds from the passage to the turn. However, the flow characteristics at these locations differ when trips are skewed at -45 deg. Changes in the flow structure are expected to augment heat transfer, in agreement with the heat transfer measurements of Johnson, et al. The present results show that trips are skewed at -45 deg in the outward flow passage and trips are skewed at +45 deg in the inward flow passage maximize heat transfer. Details of the present measurements were related to the heat transfer measurements of Johnson, et al. to relate fluid flow and heat transfer measurements.

Catalytic reactor

DOEpatents

Aaron, Timothy Mark [East Amherst, NY; Shah, Minish Mahendra [East Amherst, NY; Jibb, Richard John [Amherst, NY

2009-03-10

A catalytic reactor is provided with one or more reaction zones each formed of set(s) of reaction tubes containing a catalyst to promote chemical reaction within a feed stream. The reaction tubes are of helical configuration and are arranged in a substantially coaxial relationship to form a coil-like structure. Heat exchangers and steam generators can be formed by similar tube arrangements. In such manner, the reaction zone(s) and hence, the reactor is compact and the pressure drop through components is minimized. The resultant compact form has improved heat transfer characteristics and is far easier to thermally insulate than prior art compact reactor designs. Various chemical reactions are contemplated within such coil-like structures such that as steam methane reforming followed by water-gas shift. The coil-like structures can be housed within annular chambers of a cylindrical housing that also provide flow paths for various heat exchange fluids to heat and cool components.

NOx Emission Reduction by Oscillating combustion

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

Institute of Gas Technology

2004-01-30

High-temperature, natural gas-fired furnaces, especially those fired with preheated air, produce large quantities of NO{sub x} per ton of material processed. Regulations on emissions from industrial furnaces are becoming increasingly more stringent. In addition, competition is forcing operators to make their furnaces more productive and/or efficient. Switching from preheated air to industrial oxygen can increase efficiency and reduce NO{sub x}, but oxygen is significantly more costly than air and may not be compatible with the material being heated. What was needed, and what was developed during this project, is a technology that reduces NO{sub x} emissions while increasing furnace efficiencymore » for both air- and oxy-fired furnaces. Oscillating combustion is a retrofit technology that involves the forced oscillation of the fuel flow rate to a furnace. These oscillations create successive, fuel-rich and fuel-lean zones within the furnace. Heat transfer from the flame to the load increases due to the more luminous fuel-rich zones, a longer overall flame length, and the breakup of the thermal boundary layer. The increased heat transfer shortens heat up times, thereby increasing furnace productivity, and reduces the heat going up the stack, thereby increasing efficiency. The fuel-rich and fuel-lean zones also produce substantially less NO{sub x} than firing at a constant excess air level. The longer flames and higher heat transfer rate reduces overall peak flame temperature and thus reduces additional NO{sub x} formation from the eventual mixing of the zones and burnout of combustibles from the rich zones. This project involved the development of hardware to implement oscillating combustion on an industrial scale, the laboratory testing of oscillating combustion on various types of industrial burners, and the field testing of oscillating combustion on several types of industrial furnace. Before laboratory testing began, a market study was conducted, based on the attributes of oscillating combustion and on the results of an earlier project at GTI and Air Liquide, to determine which applications for oscillating combustion would show the greatest probability for technical success and greatest probability for market acceptability. The market study indicated that furnaces in the steel, glass, and metal melting industries would perform well in both categories. These findings guided the selection of burners for laboratory testing and, with the results of the laboratory testing, guided the selection of field test sites.« less

NOx Emission Reduction by Oscillating Combustion

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

John C. Wagner

2004-03-31

High-temperature, natural gas-fired furnaces, especially those fired with preheated air, produce large quantities of NO{sub x} per ton of material processed. Regulations on emissions from industrial furnaces are becoming increasingly more stringent. In addition, competition is forcing operators to make their furnaces more productive and/or efficient. Switching from preheated air to industrial oxygen can increase efficiency and reduce NO{sub x}, but oxygen is significantly more costly than air and may not be compatible with the material being heated. What was needed, and what was developed during this project, is a technology that reduces NO{sub x} emissions while increasing furnace efficiencymore » for both air- and oxy-fired furnaces. Oscillating combustion is a retrofit technology that involves the forced oscillation of the fuel flow rate to a furnace. These oscillations create successive, fuel-rich and fuel-lean zones within the furnace. Heat transfer from the flame to the load increases due to the more luminous fuel-rich zones, a longer overall flame length, and the breakup of the thermal boundary layer. The increased heat transfer shortens heat up times, thereby increasing furnace productivity, and reduces the heat going up the stack, thereby increasing efficiency. The fuel-rich and fuel-lean zones also produce substantially less NO{sub x} than firing at a constant excess air level. The longer flames and higher heat transfer rate reduces overall peak flame temperature and thus reduces additional NO{sub x} formation from the eventual mixing of the zones and burnout of combustibles from the rich zones. This project involved the development of hardware to implement oscillating combustion on an industrial scale, the laboratory testing of oscillating combustion on various types of industrial burners, and the field testing of oscillating combustion on several types of industrial furnace. Before laboratory testing began, a market study was conducted, based on the attributes of oscillating combustion and on the results of an earlier project at GTI and Air Liquide, to determine which applications for oscillating combustion would show the greatest probability for technical success and greatest probability for market acceptability. The market study indicated that furnaces in the steel, glass, and metal melting industries would perform well in both categories. These findings guided the selection of burners for laboratory testing and, with the results of the laboratory testing, guided the selection of field test sites.« less

Study of the stability of electrode metal melting and transfer in the process of consumable electrode welding powered by supplies with differing dynamic characteristics

NASA Astrophysics Data System (ADS)

Saraev, Y. N.; Chinakhov, D. A.; Il'yashchenko, D. P.; Kiselev, A. S.; Gardiner, A. S.; Raev, I. V.

2016-11-01

In the paper we present the results of the study of the power supply characteristics effect upon the stability of electrode metal melting and transfer into the weld pool in the process of consumable electrode welding. It was shown that application of inverter type welding power supplies of the new generation results in changing the characteristics of the heat and mass transfer which has a decisive impact upon the heat content of the weld pool, reduction of residual stresses in the heat-affected zone (HAZ). The authors also substantiate the tendency to the reduction of the structural constituents in the area of the permanent joint.

Mathematical Model of Two Phase Flow in Natural Draft Wet-Cooling Tower Including Flue Gas Injection

NASA Astrophysics Data System (ADS)

Hyhlík, Tomáš

2016-03-01

The previously developed model of natural draft wet-cooling tower flow, heat and mass transfer is extended to be able to take into account the flow of supersaturated moist air. The two phase flow model is based on void fraction of gas phase which is included in the governing equations. Homogeneous equilibrium model, where the two phases are well mixed and have the same velocity, is used. The effect of flue gas injection is included into the developed mathematical model by using source terms in governing equations and by using momentum flux coefficient and kinetic energy flux coefficient. Heat and mass transfer in the fill zone is described by the system of ordinary differential equations, where the mass transfer is represented by measured fill Merkel number and heat transfer is calculated using prescribed Lewis factor.

Experimental Investigation of Turbojet Thrust Augmentation Using an Ejector

DTIC Science & Technology

2007-03-01

mechanisms in which a particle can exchange energy. Thrust augmenting devices can be divided into two categories: ones that exchange net work or heat and...two categories from the energy equation discussion above. Thrust augmentation is achieved through turbulent entrainment where work and/or heat is...front sustained by compression waves from a trailing reaction zone. A deflagration wave is a subsonic flame front sustained by heat transfer

3-D Transient Heat Transfer Analysis of Slab Heating Characteristics in a Reheating Furnace in Hot Strip Mills

NASA Astrophysics Data System (ADS)

Jang, J. Y.; Lee, Y. W.; Lin, C. N.; Wang, C. H.

2016-05-01

A three-dimensional mathematical transient heat transfer model for the prediction of temperature distribution within the slab has been developed by considering the thermal radiation in the walking-beam-type reheating furnace chamber. The steel slabs are heated up through the non-firing, preheating, 1st-heating, 2nd-heating, and soaking zones in the furnace, respectively, where the furnace wall temperature is function of time. Comparison with the in-situ experimental data from Steel Company in Taiwan shows that the present heat transfer model works well for the prediction of thermal behavior of the slab in the reheating furnace. The effects of different skid button height (H=60mm, 90mm, and 120mm) and different gap distance between two slabs (S=50mm, 75mm, and 100mm) on the slab skid mark formation and temperature profiles are investigated. It is found that the skid mark severity decreases with an increase in the skid button height. The effect of gap distance is important only for the slab edge planes, while it is insignificant for the slab central planes.

Thermal history of the Acoculco geothermal system, eastern Mexico: Insights from numerical modeling and radiocarbon dating

NASA Astrophysics Data System (ADS)

Canet, Carles; Trillaud, Frederic; Prol-Ledesma, Rosa María; González-Hernández, Galia; Peláez, Berenice; Hernández-Cruz, Berenice; Sánchez-Córdova, María M.

2015-10-01

Acoculco is a geothermal prospective area hosted by a volcanic caldera complex in the eastern Trans-Mexican Volcanic Belt. Surface manifestations are scarce and consist of gas discharges (CO2-rich) and acid-sulfate springs of low temperature, whereas hydrothermal explosive activity is profusely manifested by meter-scale craters and mounds of hydrothermal debris and breccias. Silicic alteration extends for several square kilometers around the zone with gas manifestations and explosive features, affecting surficial volcanic rocks, primarily tuffs and breccias. In the subsurface, an argillic alteration zone (ammonium illite) extends down to a depth of ∼ 600 m, and underneath it a propylitic zone (epidote-calcite-chlorite) occurs down to ∼ 1000 m. Thermal logs from an exploratory borehole (EAC-1, drilled in 1995 down to 1810 m) showed a conductive heat transfer regime under high geothermal gradient (∼ 140 °C/1000 m). In contrast, the thermal profile established from temperatures of homogenization of fluid inclusions-measured on core samples from the same drill hole-suggests that convection occurred in the past through the upper ~ 1400 m of the geothermal system. A drop in permeability due to the precipitation of alteration minerals would have triggered the cessation of the convective heat transfer regime to give place to a conductive one. With the purpose of determining when the transition of heat transfer regime occurred, we developed a 1D model that simulates the time-depth distribution of temperature. According to our numerical simulations, this transition happened ca. 7000 years ago; this date is very recent compared to the lifespan of the geothermal system. In addition, radiocarbon chronology indicates that the hydrothermal explosive activity postdates the end of the convective heat transfer regime, having dated at least three explosive events, at 4867-5295, 1049-1417 and 543-709 y cal. BP. Therefore, hydrothermal explosions arise from the self-sealing of the Acoculco geothermal system, involving a natural hazard that could affect future geothermal-power infrastructure.

The experimental study of heat transfer around molds inside a model autoclave

NASA Astrophysics Data System (ADS)

Ghamlouch, Taleb; Roux, Stéphane; Lefèvre, Nicolas; Bailleul, Jean-Luc; Sobotka, Vincent

2018-05-01

The temperature distribution within composite parts manufactured inside autoclaves plays a key role in determining the parts quality at the end of the curing cycle. Indeed, heat transfer between the parts and the surroundings inside an autoclave is strongly coupled with the flow field around the molds and can be modeled through the convective heat transfer coefficient (HTC). The aerodynamically unsuitable geometry of the molds generates complex turbulent non-uniform flows around them accompanied with the presence of dead zones. This heterogeneity can imply non-uniform convective heat transfers leading to temperature gradients inside parts that can be prejudicial. Given this fact, the purpose of this study is to perform experimental measurements in order to describe the flow field and the convective heat transfer behavior around representative industrial molds installed inside a home-made model. A key point of our model autoclave is the ease of use of non-intrusive measuring instruments: the Particle Image Velocimetry (PIV) technique and infrared imaging camera for the study of the flow field and the heat transfer coefficient distribution around the molds respectively. The experimental measurements are then compared to computational fluid dynamics (CFD) calculations performed on the computer code ANSYS Fluent 16.0®. This investigation has revealed, as expected, a non-uniform distribution of the convective heat transfer coefficient around the molds and therefore the presence of thermal gradients which can reduce the composite parts quality during an autoclave process. A good agreement has been achieved between the experimental and the numerical results leading then to the validation of the performed numerical simulations.

Probing heat transfer, fluid flow and microstructural evolution during fusion welding of alloys

NASA Astrophysics Data System (ADS)

Zhang, Wei

The composition, geometry, structure and properties of the welded joints are affected by the various physical processes that take place during fusion welding. Understanding these processes has been an important goal in the contemporary welding research to achieve structurally sound and reliable welds. In the present thesis research, several important physical processes including the heat transfer, fluid flow and microstructural evolution in fusion welding were modeled based on the fundamentals of transport phenomena and phase transformation theory. The heat transfer and fluid flow calculation is focused on the predictions of the liquid metal convection in the weld pool, the temperature distribution in the entire weldment, and the shape and size of the fusion zone (FZ) and heat affected zone (HAZ). The modeling of microstructural evolution is focused on the quantitative understanding of phase transformation kinetics during welding of several important alloys under both low and high heating and cooling conditions. Three numerical models were developed in the present thesis work: (1) a three-dimensional heat transfer and free surface flow model for the gas metal arc (GMA) fillet welding considering the complex weld joint geometry, (2) a phase transformation model based on the Johnson-Mehl-Avrami (JMA) theory, and (3) a one-dimensional numerical diffusion model considering multiple moving interfaces. To check the capabilities of the developed models, several cases were investigated, in which the predictions from the models were compared with the experimental results. The cases studied are the follows. For the modeling of heat transfer and fluid flow, the welding processes studied included gas tungsten arc (GTA) linear welding, GTA transient spot welding, and GMA fillet welding. The calculated weldment geometry and thermal cycles was validated against the experimental data under various welding conditions. For the modeling of microstructural evolution, the welded materials investigated included AISI 1005 low-carbon steel, 1045 medium-carbon steel, 2205 duplex stainless steel (DSS) and Ti-6Al-4V alloy. The calculated phase transformation kinetics were compared with the experimental results obtained using an x-ray diffraction technique by Dr. John W. Elmer of Lawrence Livermore National Laboratory. (Abstract shortened by UMI.)

Convection effects on radial segregation and crystal melt interface in vertical Bridgman growth

NASA Technical Reports Server (NTRS)

Tanveer, S.

1993-01-01

We analytically study the influence of convection caused by horizontal heat transfer through the sides of a vertical Bridgman apparatus. We consider the case when the heat transfer across the side walls is small so that the resulting interfacial deformation and fluid velocities are also small. This allows us to linearize the Navier-Stokes equations and express the interfacial conditions about a planar interface through a Taylor expansion. Using a no tangential stress conditions on the side walls, asymptotic expressions for both the interfacial slope, and radial segregation at the crystal-melt interface are obtained in closed form in the limit of large thermal Rayleigh number. It is suggested that these can be reduced by appropriately controlling a specific heat transfer property at the edge of the insulation zone in the solid side.

Startup analysis for a high temperature gas loaded heat pipe

NASA Technical Reports Server (NTRS)

Sockol, P. M.

1973-01-01

A model for the rapid startup of a high-temperature gas-loaded heat pipe is presented. A two-dimensional diffusion analysis is used to determine the rate of energy transport by the vapor between the hot and cold zones of the pipe. The vapor transport rate is then incorporated in a simple thermal model of the startup of a radiation-cooled heat pipe. Numerical results for an argon-lithium system show that radial diffusion to the cold wall can produce large vapor flow rates during a rapid startup. The results also show that startup is not initiated until the vapor pressure p sub v in the hot zone reaches a precise value proportional to the initial gas pressure p sub i. Through proper choice of p sub i, startup can be delayed until p sub v is large enough to support a heat-transfer rate sufficient to overcome a thermal load on the heat pipe.

Tidally-induced thermal runaway on extrasolar Earth: Impact on habitability

NASA Astrophysics Data System (ADS)

Behounkova, M.; Tobie, G.; Choblet, G.; Cadek, O.

2010-12-01

Low mass extrasolar bodies start to be discovered owing to the increased precision of detection surveys. As the detection probability decreases with the star-body distance, these planets (and the numerous candidates already announced for the coming years) are likely to orbit their parent stars in a close distance. These short-period planets undergo a strong tidal forcing and their orbits are tidally locked. The associated heat production may influence the internal thermal evolution of these bodies: it has even been suggested that the habitable zone could be influenced by tidal heating (Barnes et al. 2008; Henning et al. 2009). In this study, we further investigate the effect of tidal heating on thermal evolution of tidally locked Earth-like planets. Owing to the strong temperature dependence of the mechanical properties of both the long-term evolution and the tidal deformations, the two processes are coupled. Nevertheless, the tidal deformation has no direct effect on the convective flow and only the dissipative part is included as a heat source for mantle dynamics since the time scales of the two processes strongly differs. For significant tidal dissipation rates, the strong positive feedback leads, in some cases, to thermal runaways. We focus here on the susceptibility of Earth-like planets to tidal dissipation for fixed orbital parameters (eccentricity, orbital period and the spin-orbit resonance type) and on the associated timescales for runaway (if any). In order to describe this behavior and the three dimensional nature of both the tidal forcing and the temperature anomalies, a fully three-dimensional approach solving the two processes simultaneously is employed (Běhounková et al., JGR, in press). We consider an extrasolar planet having the internal properties similar to the Earth. Two modes for heat transfer are modeled through the choice of convective parameters (Rayleigh number and temperature dependence of viscosity, amount of radiogenic heating): a relatively effective plate-tectonics-like regime and a one-plate (stagnant lid) regime. For all numerical experiments sharing the same initial temperature conditions, the reciprocal value of the runaway timescale depends linearly on the initial tidal dissipation. Moreover, the occurrence of tidally driven runaways is associated to large scale melting of the interior having an impact on the habitability of the planet. In the case of runaway timescales between 0.1 and 1Gy and for the plate-tectonics-like heat transfer, the habitable zone is affected by the thermal runaway only for high eccentricities (e≳0.2) for 0.1M sun stars and 1:1 resonance. In the case of the 3:2 orbital resonance, whatever the eccentricity is, the runaway affects the habitable zone for orbital periods lower than 7-12 days. The impact on the habitable zone is even higher for one-plate planets due to the ineffective heat transfer. For more massive stars (>0.5M sun), tidal heating in the habitable zone is not significant and has no impact on the internal evolution.

Models of the thermal effects of melt migration at continental interiors, with applications to the Colorado Plateau

NASA Astrophysics Data System (ADS)

Roy, M.; Rios, D.; Cosburn, K.

2017-12-01

Shear between the moving lithosphere and the underlying asthenospheric mantle can produce dynamic pressure gradients that control patterns of melt migration by percolative flow. Within continental interiors these pressure gradients may be large enough to focus melt migration into zones of low dynamic pressure and thus influence the surface distribution of magmatism. We build upon previous work to show that for a lithospheric keel that protrudes into the "mantle wind," spatially-variable melt migration can lead to spatially-variable thermal weakening of the lithosphere. Our models treat advective heat transfer in porous flow in the limit that heat transfer between the melt and surrounding matrix dominates over conductive heat transfer within either the melt or the solid alone. The models are parameterized by a heat transfer coefficient that we interpret to be related to the efficiency of heat transfer across the fluid-rock interface, related to the geometry and distribution of porosity. Our models quantitatively assess the viability of spatially variable thermal-weakening caused by melt-migration through continental regions that are characterized by variations in lithospheric thickness. We speculate upon the relevance of this process in producing surface patterns of Cenozoic magmatism and heatflow at the Colorado Plateau in the western US.

Enhanced condensation heat transfer with wettability patterning

NASA Astrophysics Data System (ADS)

Sinha Mahapatra, Pallab; Ghosh, Aritra; Ganguly, Ranjan; Megaridis, Constantine

2015-11-01

Condensation of water vapor on metal surfaces is useful for many engineering applications. A facile and scalable method is proposed for removing condensate from a vertical plate during dropwise condensation (DWC) in the presence of non-condensable gases (NCG). We use wettability-patterned superhydrophilic tracks (filmwise condensing domains) on a mirror-finish (hydrophilic) aluminum surface that promotes DWC. Tapered, horizontal ``collection'' tracks are laid to create a Laplace pressure driven flow, which collects condensate from the mirror-finish domains and sends it to vertical ``drainage tracks'' for gravity-induced shedding. An optimal design is achieved by changing the fractional area of superhydrophilic tracks with respect to the overall plate surface, and augmenting capillary-driven condensate-drainage by adjusting the track spatial layout. The design facilitates pump-less condensate drainage and enhances DWC heat transfer on the mirror-finish regions. The study highlights the relative influences of the promoting and retarding effects of dropwise and filmwise condensation zones on the overall heat transfer improvement on the substrate. The study demonstrated ~ 34% heat transfer improvement on Aluminum surface for the optimized design.

Thermal behavior in the cracking reaction zone of scramjet cooling channels at different channel aspect ratios

NASA Astrophysics Data System (ADS)

Zhang, Silong; Feng, Yu; Jiang, Yuguang; Qin, Jiang; Bao, Wen; Han, Jiecai; Haidn, Oskar J.

2016-10-01

To study the thermal behavior in the cracking reaction zone of regeneratively cooled scramjet cooling channels at different aspect ratios, 3-D model of fuel flow in terms of the fuel's real properties and cracking reaction is built and validated through experiments. The whole cooling channel is divided into non-cracking and cracking reaction zones. Only the cracking reaction zone is studied in this article. The simulation results indicate that the fuel conversion presents a similar distribution with temperature because the fuel conversion in scramjet cooling channels is co-decided by the temperature and velocity but the temperature plays the dominate role. For the cases given in this paper, increasing the channel aspect ratio will increase the pressure drop and it is not beneficial for reducing the wall temperature because of the much severer thermal stratification, larger conversion non-uniformity, the corresponding M-shape velocity profile which will cause local heat transfer deterioration and the decreased chemical heat absorption. And the decreased chemical heat absorption caused by stronger temperature and conversion non-uniformities is bad for the utilization of chemical heat sink, chemical recuperation process and the ignition performance.

Coupling the Multizone Airflow and Contaminant Transport Software CONTAM with EnergyPlus Using Co-Simulation.

PubMed

Dols, W Stuart; Emmerich, Steven J; Polidoro, Brian J

2016-08-01

Building modelers need simulation tools capable of simultaneously considering building energy use, airflow and indoor air quality (IAQ) to design and evaluate the ability of buildings and their systems to meet today's demanding energy efficiency and IAQ performance requirements. CONTAM is a widely-used multizone building airflow and contaminant transport simulation tool that requires indoor temperatures as input values. EnergyPlus is a prominent whole-building energy simulation program capable of performing heat transfer calculations that require interzone and infiltration airflows as input values. On their own, each tool is limited in its ability to account for thermal processes upon which building airflow may be significantly dependent and vice versa. This paper describes the initial phase of coupling of CONTAM with EnergyPlus to capture the interdependencies between airflow and heat transfer using co-simulation that allows for sharing of data between independently executing simulation tools. The coupling is accomplished based on the Functional Mock-up Interface (FMI) for Co-simulation specification that provides for integration between independently developed tools. A three-zone combined heat transfer/airflow analytical BESTEST case was simulated to verify the co-simulation is functioning as expected, and an investigation of a two-zone, natural ventilation case designed to challenge the coupled thermal/airflow solution methods was performed.

Numerical simulation of fluid flow and heat transfer in enhanced copper tube

NASA Astrophysics Data System (ADS)

Rahman, M. M.; Zhen, T.; Kadir, A. K.

2013-06-01

Inner grooved tube is enhanced with grooves by increasing the inner surface area. Due to its high efficiency of heat transfer, it is used widely in power generation, air conditioning and many other applications. Heat exchanger is one of the example that uses inner grooved tube to enhance rate heat transfer. Precision in production of inner grooved copper tube is very important because it affects the tube's performance due to various tube parameters. Therefore, it is necessary to carry out analysis in optimizing tube performance prior to production in order to avoid unnecessary loss. The analysis can be carried out either through experimentation or numerical simulation. However, experimental study is too costly and takes longer time in gathering necessary information. Therefore, numerical simulation is conducted instead of experimental research. Firstly, the model of inner grooved tube was generated using SOLIDWORKS. Then it was imported into GAMBIT for healing, followed by meshing, boundary types and zones settings. Next, simulation was done in FLUENT where all the boundary conditions are set. The simulation results were observed and compared with published experimental results. It showed that heat transfer enhancement in range of 649.66% to 917.22% of inner grooved tube compared to plain tube.

Gas-grain energy transfer in solar nebula shock waves: Implications for the origin of chondrules

NASA Technical Reports Server (NTRS)

Hood, L. L.; Horanyi, M.

1993-01-01

Meteoritic chondrules provide evidence for the occurrence of rapid transient heating events in the protoplanetary nebula. Astronomical evidence suggests that gas dynamic shock waves are likely to be excited in protostellar accretion disks by processes such as protosolar mass ejections, nonaxisymmetric structures in an evolving disk, and impact on the nebula surface of infalling 'clumps' of circumstellar gas. Previous detailed calculations of gas-grain energy and momentum transfer have supported the possibility that such shock waves could have melted pre-existing chondrule-sized grains. The main requirement for grains to reach melting temperatures in shock waves with plausibly low Mach numbers is that grains existed in dust-rich zones (optical depth greater than 1) where radiative cooling of a given grain can be nearly balanced by radiation from surrounding grains. Localized dust-rich zones also provide a means of explaining the apparent small spatial scale of heating events. For example, the scale size of at least some optically thick dust-rich zones must have been relatively small (less than 10 kilometers) to be consistent with petrologic evidence for accretion of hot material onto cold chondrules. The implied number density of mm-sized grains for these zones would be greater than 30 m(exp -3). In this paper, we make several improvements of our earlier calculations to include radiation self-consistently in the shock jump conditions, and we include heating of grains due to radiation from the shocked gas. In addition, we estimate the importance of momentum feedback of dust concentrations onto the shocked gas which would tend to reduce the efficiency of gas dynamic heating of grains in the center of the dust cloud.

Modeling of Melt Growth During Carbothermal Processing of Lunar Regolith

NASA Technical Reports Server (NTRS)

Balasubramaniam, R.; Gokoglu S.; Hegde, U.

2012-01-01

The carbothermal processing of lunar regolith has been proposed as a means to produce carbon monoxide and ultimately oxygen to support human exploration of the moon. In this process, gaseous methane is pyrolyzed as it flows over the hot surface of a molten zone of lunar regolith and is converted to carbon and hydrogen. Carbon gets deposited on the surface of the melt, and mixes and reacts with the metal oxides in it to produce carbon monoxide that bubbles out of the melt. Carbon monoxide is further processed in other reactors downstream to ultimately produce oxygen. The amount of oxygen produced crucially depends on the amount of regolith that is molten. In this paper we develop a model of the heat transfer in carbothermal processing. Regolith in a suitable container is heated by a heat flux at its surface such as by continuously shining a beam of solar energy or a laser on it. The regolith on the surface absorbs the energy and its temperature rises until it attains the melting point. The energy from the heat flux is then used for the latent heat necessary to change phase from solid to liquid, after which the temperature continues to rise. Thus a small melt pool appears under the heated zone shortly after the heat flux is turned on. As time progresses, the pool absorbs more heat and supplies the energy required to melt more of the regolith, and the size of the molten zone increases. Ultimately, a steady-state is achieved when the heat flux absorbed by the melt is balanced by radiative losses from the surface. In this paper, we model the melting and the growth of the melt zone with time in a bed of regolith when a portion of its surface is subjected to a constant heat flux. The heat flux is assumed to impinge on a circular area. Our model is based on an axisymmetric three-dimensional variation of the temperature field in the domain. Heat transfer occurs only by conduction, and effects of convective heat transport are assumed negligible. Radiative heat loss from the surface of the melt and the regolith to the surroundings is permitted. We perform numerical computations to determine the shape and the mass of the melt at steady state and its time evolution. We first neglect the volume change upon melting, and subsequently perform calculations including it. Predictions from our model are compared to test data to determine the effective thermal conductivities of the regolith and the melt that are compatible with the data

Nonstationary heat and mass transfer in the multilayer building construction with ventilation channels

NASA Astrophysics Data System (ADS)

Kharkov, N. S.

2017-11-01

Results of numerical modeling of the coupled nonstationary heat and mass transfer problem under conditions of a convective flow in facade system of a three-layer concrete panel for two different constructions (with ventilation channels and without) are presented. The positive effect of ventilation channels on the energy and humidity regime over a period of 12 months is shown. Used new method of replacement a solid zone (requiring specification of porosity and material structure, what complicates process of convergence of the solution) on quasi-solid in form of a multicomponent mixture (with restrictions on convection and mass fractions).

Closing the Loop on Space Waste

NASA Astrophysics Data System (ADS)

Meier, A. J.; Hintze, P. E.

2018-02-01

A heat transfer study of mission mixed waste streams in a reactor hot zone, along with solid, tar, and water recovery. This research enables reliability and benefit on waste conversion systems to manage our environmental impact, on- and off-Earth.

Natural convection flows and associated heat transfer processes in room fires

NASA Astrophysics Data System (ADS)

Sargent, William Stapf

This report presents the results of experimental investigations of natural convection flows and associated heat transfer processes produced by small fires in rooms with a single door or window opening. Calculation procedures have been developed to model the major aspects of these flows.Two distinct sets of experiments were undertaken.First, in a roughly 1/4 scale facility, a slightly dense solution of brine was allowed to flow into a tank of fresh water. The resulting density difference produced a flow which simulated a very small fire in a room with adiabatic walls. Second, in an approximately 1/2 scale test room, a nearly stoichioinetric mixture of air and natural gas was burned at floor level to model moderate strength fires. In this latter facility, we directly measured the heat conducted through the walls, in addition to determining the gas temperature and composition throughout the room.These two facilities complemented each other. The former offered good flow visualization and allowed us to observe the basic flow phenomena in the absence of heat transfer effects. On the other hand, the latter, which involved relatively larger fires, was a more realistic simulation of an actual room fire, and allowed us to calculate the convective heat transfer to the ceiling and walls. In addition, the stronger sources present in these 1/2 scale tests produced significant secondary flows. These secondary flows along with heat transfer effects act to modify the gas temperature or density profiles within the room from those observed in the 1/4 scale experiments.Several calculation procedures have been developed, based on the far field properties of plumes when the density differences are small (the Boussinesq approximation). The simple point source plume solution is used along with hydraulic analysis of flow through an orifice to estimate the temperatures of the hot ceiling layer gas and of the cooler floor zone fluid, as well as the height of the interface between them. A finite source plume model is combined with conservation equations across the interface to compute the evolution of the plume above the interface. This calculation then provides the starting point for an integral analysis of the flow and heat transfer in the turbulent ceiling jet.The computed results both for the average floor and ceiling zone gas temperatures, and for the connective heat transfer in the ceiling jet agreed reasonably well with our experimental data. This agreement suggests that our computational procedures can be applied to answer practical questions, such as whether the connective heat flux from a given fire in a real room would be sufficient to trigger sprinklers or other detection systems in a given amount of time.

Heat transfer within hydrodissection fluids: An analysis of thermal conduction and convection using liquid and gel materials.

PubMed

Johnson, Alexander; Brace, Christopher

2015-01-01

Interventional oncology procedures such as thermal ablation are becoming widely used for many tumours in the liver, kidney and lung. Thermal ablation refers to the focal destruction of tissue by generating cytotoxic temperatures in the treatment zone. Hydrodissection - separating tissues with fluids - protects healthy tissues adjacent to the ablation treatment zone to improve procedural safety, and facilitate more aggressive power application or applicator placement. However, fluids such as normal saline and 5% dextrose in water (D5W) can migrate into the peritoneum, reducing their protective efficacy. As an alternative, a thermo-gelable poloxamer 407 (P407) solution has been recently developed to facilitate hydrodissection procedures. We hypothesise that the P407 gel material does not provide convective heat dissipation from the ablation site, and therefore may alter the heat transfer dynamics compared to liquid materials during hydrodissection-assisted thermal ablation. The purpose of this study was to investigate the heat dissipation mechanics within D5W, liquid P407 and gel P407 hydrodissection barriers. Overall it was shown that the gel P407 dissipated heat primarily through conduction, whereas the liquid P407 and D5W dissipated heat through convection. Furthermore, the rate of temperature change within the gel P407 was greater than liquid P407 and D5W. Testing to evaluate the in vivo efficacy of the fluids with different modes of heat dissipation seems warranted for further study.

Faults Get Colder Through Transient Granular Vortices

NASA Astrophysics Data System (ADS)

Einav, I.; Rognon, P.; Miller, T.; Sulem, J.

2018-03-01

Fault temperatures govern their weakening and control the dynamics of earthquakes during slip. Despite predictions of significant temperature rise within fault gouges during earthquake events, observations of frictional melting zones along exhumed faults are relatively rare. Could there be a heat transfer mechanism, previously not considered, that results in ubiquitously colder faults during earthquakes? We demonstrate that the remarkable, previously neglected mechanism of heat transfer through transient granular vortices may be at the core of this. We present and analyze results from perpetual simple shear experiments on a system of granular disks with which we are able to quantify the sizes and lifetimes of granular vortices within fault gouges during earthquakes. We then develop a formula that captures the contribution these vortices have on heat transfer. Using this formula, we show that crustal faults such as those in the San Andreas system may experience a maximum temperature rise 5 to 10 times lower than previously thought.

Detailed heat/mass transfer distributions in a rotating two pass coolant channel with engine-near cross section and smooth walls.

PubMed

Rathjen, L; Hennecke, D K; Bock, S; Kleinstück, R

2001-05-01

This paper shows results obtained by experimental and numerical investigations concerning flow structure and heat/mass transfer in a rotating two-pass coolant channel with engine-near geometry. The smooth two passes are connected by a 180 degrees U-bend in which a 90 degrees turning vane is mounted. The influence of rotation number, Reynolds number and geometry is investigated. The results show a detailed picture of the flow field and distributions of Sherwood number ratios determined experimentally by the use of the naphthalene sublimation technique as well as Nusselt number ratios obtained from the numerical work. Especially the heat/mass transfer distributions in the bend and in the region after the bend show strong gradients, where several separation zones exist and the flow is forced to follow the turbine airfoil shape. Comparisons of numerical and experimental results show only partly good agreement.

An analytical approach to thermal modeling of Bridgman-type crystal growth. I - One-dimensional analysis

NASA Technical Reports Server (NTRS)

Naumann, R. J.

1982-01-01

A relatively simple one-dimensional thermal model of the Bridgman growth process has been developed which is applicable to the growth of small diameter samples with conductivities similar to those of metallic alloys. The heat flow in a translating rod is analyzed in a way that is applicable to Biot numbers less than unity. The model accommodates an adiabatic zone, different heat transfer coefficients in the hot and cold zones, and changes in sample material properties associated with phase change. The analysis is applied to several simplified cases. The effect of the rod's motion is studied in a three-zone furnace for a rod sufficiently long that end effects can be neglected; end effects are then investigated for a motionless rod. Finally, the addition of a fourth zone, an independently controlled booster heater between the main heater and the adiabatic zone, is evaluated for its ability to increase the gradient in the sample at the melt interface and to control the position of the interface.

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

Elrod, D.

FED reduces the effort required to obtain the necessary geometric input for problems which are to be solved using the heat-transfer code, TRUMP. TRUMP calculates transient and steady-state temperature distributions in multidimensional systems. FED can properly zone any body of revolution in one, two, or three dimensions.

Modelling of nitrogen oxides distribution in the hearth of gas-fired industrial furnace

NASA Astrophysics Data System (ADS)

Zhubrin, S.; Glazov, V.; Guzhov, S.

2017-11-01

A model is proposed for calculating the formation and transportation of nitrogen oxides in the combustion chamber of an industrial furnace heated by gaseous fuels burning. The calculations use a three-dimensional stationary description of turbulent flow and mixing of fuel and oxidizer flows in the presence of heat transfer, mass transfer, and momentum between them transfer. Simulation of the spatial pattern of nitrogen oxides formation in the working space of the furnace is performed in the programming and computing suite SCAN. It is shown that the temperature non-uniformity over the hearth surface is not too pronounced due to the organization of the inclined flow inlet in the direction of the hearth, which is a desirable feature of the furnace operation. The highest concentration of combustion products is observed in the zone of maximum temperatures. In addition, the existence of two zones of the highest generation of oxides has been determined. The first zone is located approximately in the center of the hearth, and the second is located on the far external surface of the furnace. The possibility of using the developed model in the SCAN complex for carrying out parametric studies and engineering calculations, as well as for modification in the direction of adjusting and adapting the model to the regime-constructive features of specific energy technological devices, is noted.

The Influence of Static and Rotating Magnetic Fields on Heat and Mass Transfer in Silicon Floating Zones

NASA Technical Reports Server (NTRS)

Croll, A.; Dold, P.; Kaiser, Th.; Szofran, F. R.; Benz, K. W.

1999-01-01

Heat and mass transfer in float-zone processing are strongly influenced by convective flows in the zone. They are caused by buoyancy convection, thermocapillary (Marangoni) convection, or artificial sources such as rotation and radio-frequency heating. Flows in conducting melts can be controlled by the use of magnetic fields, either by damping fluid motion with static fields or by generating a defined flow with rotating fields. The possibilities of using static and rotating magnetic fields in silicon floating-zone growth have been investigated by experiments in axial static fields up to 5 T and in transverse rotating magnetic fields up to 7.5 mT. Static fields of a few 100 mT already suppress most striations but are detrimental to the radial segregation by introducing a coring effect. A complete suppression of dopant striations caused by time-dependent thermocapillary convection and a reduction of the coring to insignificant values, combined with a shift of the axial segregation profile toward a more diffusion-limited case, is possible with static fields greater than or equal to 1 T. However, under certain conditions the use of high axial magnetic fields can lead to the appearance of a new type of pronounced dopant striations, caused by thermoelectromagnetic convection. The use of a transverse rotating magnetic field influences the microscopic segregation at quite low inductions, of the order of a few millitesla. The field shifts time- dependent flows and the resulting striation patterns from a broad range of low frequencies at high amplitudes to a few high frequencies at low amplitudes.

Calibration of the heat balance model for prediction of car climate

NASA Astrophysics Data System (ADS)

Pokorný, Jan; Fišer, Jan; Jícha, Miroslav

2012-04-01

In the paper, the authors refer to development a heat balance model to predict car climate and power heat load. Model is developed in Modelica language using Dymola as interpreter. It is a dynamical system, which describes a heat exchange between car cabin and ambient. Inside a car cabin, there is considered heat exchange between air zone, interior and air-conditioning system. It is considered 1D heat transfer with a heat accumulation and a relative movement Sun respect to the car cabin, whilst car is moving. Measurements of the real operating conditions of gave us data for model calibration. The model was calibrated for Škoda Felicia parking-summer scenarios.

Laser Assisted Micro Wire GMAW and Droplet Welding

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

FUERSCHBACH, PHILLIP W.; LUCK, D. L.; BERTRAM, LEE A.

2002-03-01

Laser beam welding is the principal welding process for the joining of Sandia weapon components because it can provide a small fusion zone with low overall heating. Improved process robustness is desired since laser energy absorption is extremely sensitive to joint variation and filler metal is seldom added. This project investigated the experimental and theoretical advantages of combining a fiber optic delivered Nd:YAG laser with a miniaturized GMAW system. Consistent gas metal arc droplet transfer employing a 0.25 mm diameter wire was only obtained at high currents in the spray transfer mode. Excessive heating of the workpiece in this modemore » was considered an impractical result for most Sandia micro-welding applications. Several additional droplet detachment approaches were investigated and analyzed including pulsed tungsten arc transfer(droplet welding), servo accelerated transfer, servo dip transfer, and electromechanically braked transfer. Experimental observations and rigorous analysis of these approaches indicate that decoupling droplet detachment from the arc melting process is warranted and may someday be practical.« less

Effect of Compositional Variation in TiO2-Based Flux-Cored Arc Welding Fluxes on the Thermo-physical Properties and Mechanical Behavior of a Weld Zone

NASA Astrophysics Data System (ADS)

Kim, J. B.; Lee, T. H.; Sohn, I.

2018-04-01

The effect of compositional variation in TiO2-based flux-cored arc welding fluxes on viscosity, wettability, and electronegativity was studied. The thermo-physical properties of the retrieved fluxes and their relationship with the mechanical properties of the weld zone, including tensile strength and micro-Vickers hardness, after welding were identified. Microstructural observation under similar welding conditions revealed significant grain coarsening at a corrected optical basicity (Λcorr) of 0.62, resulting in reduced strength and hardness due to greater heat transfer. Welding fluxes containing TiO2-based simple structural units should result in greater heat transfer due to the deficiency in complex [AlO4]5-- and [SiO4]4--based structural units, as identified through spectroscopic analyses using fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. The electronegativity of the retrieved fluxes was also evaluated since higher electronegativity results in greater absorption of electrons in the arc, resulting in arc condensation towards the center direction. Consequently, deeper penetration could be obtained, where the highest electronegativity was identified to be approximately 0.62 of the corrected optical basicity. Thus, both the thermal conductivity and electronegativity of the welding fluxes were identified to determine the heat transfer phenomenon during flux-cored arc welding.

Effect of Compositional Variation in TiO2-Based Flux-Cored Arc Welding Fluxes on the Thermo-physical Properties and Mechanical Behavior of a Weld Zone

NASA Astrophysics Data System (ADS)

Kim, J. B.; Lee, T. H.; Sohn, I.

2018-07-01

The effect of compositional variation in TiO2-based flux-cored arc welding fluxes on viscosity, wettability, and electronegativity was studied. The thermo-physical properties of the retrieved fluxes and their relationship with the mechanical properties of the weld zone, including tensile strength and micro-Vickers hardness, after welding were identified. Microstructural observation under similar welding conditions revealed significant grain coarsening at a corrected optical basicity (Λcorr) of 0.62, resulting in reduced strength and hardness due to greater heat transfer. Welding fluxes containing TiO2-based simple structural units should result in greater heat transfer due to the deficiency in complex [AlO4]5-- and [SiO4]4--based structural units, as identified through spectroscopic analyses using fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. The electronegativity of the retrieved fluxes was also evaluated since higher electronegativity results in greater absorption of electrons in the arc, resulting in arc condensation towards the center direction. Consequently, deeper penetration could be obtained, where the highest electronegativity was identified to be approximately 0.62 of the corrected optical basicity. Thus, both the thermal conductivity and electronegativity of the welding fluxes were identified to determine the heat transfer phenomenon during flux-cored arc welding.

Low-Temperature Thermochronology for Unraveling Thermal Processes and Dating of Fault Zones

NASA Astrophysics Data System (ADS)

Tagami, T.

2016-12-01

Thermal signatures as well as timing of fault motions can be constrained by thermochronological analyses of fault-zone rocks (e.g., Tagami, 2012). Fault-zone materials suitable for such analyses are produced by tectocic and geochemical processes, such as (1) mechanical fragmentation of host rocks, grain-size reduction of fragments and recrystallization of grains to form mica and clay minerals, (2) secondary heating/melting of host rocks by frictional fault motions, and (3) mineral vein formation as a consequence of fluid advection associated with fault motions. The geothermal structure of fault zones are primarily controlled by the following three factors: (a) regional geothermal structure around the fault zone that reflect background thermo-tectonic history of studied province, (b) frictional heating of wall rocks by fault motions and resultant heat transfer into surrounding rocks, and (c) thermal influences by hot fluid advection in and around the fault zone. Thermochronological methods widely applied in fault zones are K-Ar (40Ar/39Ar), fission-track (FT), and U-Th methods. In addition, OSL, TL, ESR and (U-Th)/He methods are applied in some fault zones, in order to extract temporal imformation related to low temperature and/or very recent fault activities. Here I briefly review the thermal sensitivity of individual thermochronological systems, which basically controls the response of each method against faulting processes. Then, the thermal sensitivity of FTs is highlighted, with a particular focus on the thermal processes characteristic to fault zones, i.e., flash and hydrothermal heating. On these basis, representative examples as well as key issues, including sampling strategy, are presented to make thermochronologic analysis of fault-zone materials, such as fault gouges, pseudotachylytes and mylonites, along with geological, geomorphological and seismological implications. Finally, the thermochronologic analyses of the Nojima fault are overviewed, as an example of multidisciplinary investigations of an active seismogenic fault system. References: T. Tagami, 2012. Thermochronological investigation of fault zones. Tectonophys., 538-540, 67-85, doi:10.1016/j.tecto.2012.01.032.

Estimation of transient heat flux density during the heat supply of a catalytic wall steam methane reformer

NASA Astrophysics Data System (ADS)

Settar, Abdelhakim; Abboudi, Saïd; Madani, Brahim; Nebbali, Rachid

2018-02-01

Due to the endothermic nature of the steam methane reforming reaction, the process is often limited by the heat transfer behavior in the reactors. Poor thermal behavior sometimes leads to slow reaction kinetics, which is characterized by the presence of cold spots in the catalytic zones. Within this framework, the present work consists on a numerical investigation, in conjunction with an experimental one, on the one-dimensional heat transfer phenomenon during the heat supply of a catalytic-wall reactor, which is designed for hydrogen production. The studied reactor is inserted in an electric furnace where the heat requirement of the endothermic reaction is supplied by electric heating system. During the heat supply, an unknown heat flux density, received by the reactive flow, is estimated using inverse methods. In the basis of the catalytic-wall reactor model, an experimental setup is engineered in situ to measure the temperature distribution. Then after, the measurements are injected in the numerical heat flux estimation procedure, which is based on the Function Specification Method (FSM). The measured and estimated temperatures are confronted and the heat flux density which crosses the reactor wall is determined.

3D magneto-convective heat transfer in CNT-nanofluid filled cavity under partially active magnetic field

NASA Astrophysics Data System (ADS)

Al-Rashed, Abdullah A. A. A.; Kolsi, Lioua; Oztop, Hakan F.; Aydi, Abdelkarim; Malekshah, Emad Hasani; Abu-Hamdeh, Nidal; Borjini, Mohamed Naceur

2018-05-01

A computational study has been performed to investigate the effects of partially active magnetic field on natural convection heat transfer in CNT-nanofluid filled and three-dimensional differentially heated closed space. Two cases are considered to see this effect as magnetic field is applied to upper half (Case I) and lower half (Case II) while remaining walls are insulated. The finite volume method is used to solve governing equations and results are obtained for different governing parameters as Hartmann number (0 ≤ Ha ≤ 100), nanoparticle volume fraction (0 ≤ φ ≤ 0.05) and height of the active zone (0 ≤ LB ≤ 1). It is found that location of magnetic field plays an important role even at the same Hartmann number. Thus, it can be a good parameter to control heat and fluid flow inside the closed space.

Nozzle cooling of hot surfaces with various orientations

NASA Astrophysics Data System (ADS)

Ondrouskova, Jana; Luks, Tomas; Horsky, Jaroslav

2012-04-01

The aim of this research is an investigation of hot surface orientation influence on heat transfer during cooling by a nozzle. Two types of nozzles were used for the experiments (air-mist nozzle and hydraulic nozzle). A test plate was cooled in three positions - top, side and bottom position. The aim was to simulate a cooling situation in the secondary zone of a continuous casting machine. Temperature was measured in seven locations under the cooled surface by thermocouples. These data were used for an inverse heat conduction problem and then boundary conditions were computed. These boundary conditions are represented by surface temperature, heat transfer coefficient and heat flux. Results from an inverse calculation were compared in each position of thermocouples separately. The total cooling intensity was specified for all configurations of nozzles and test plate orientation. Results are summarised in a graphical and numerical format.

Study of the technology of heat pipe on prevention wildfire of coal gangue hill

NASA Astrophysics Data System (ADS)

Deng, Jun; Li, Bei; Ding, Ximei; Ma, Li

2017-04-01

Self-ignitable coal gangue hill (CGH) is one kind of special combustion system, which has the characteristics of low self-ignite point, large heat storage, and easy reignition. The currently industrial fire extinguishing methods, such as inhibiting tendency of coal self-ignition, loessial overburden, and cement grouting, had unsatisfied effects for dispersing the heat out in time. Correspondingly, the CGH will lead reignition more frequently with the passage of time. The high underground temperature of CGH threatens the process of ecological and vegetation construction. Therefore, the elimination of high temperature is a vital issue to be solved urgently for habitat restoration. To achieve the ultimately ecological management goal of self-ignitable CGH - extinguishing the fire completely and never reignited, it is crucial to break the heat accumulation. Heat-pipe (HP) has a character of high efficient heat transfer capacity for eliminating the continuously high temperature in CGH. An experimental system was designed to test the heat transfer performance of HP for preventing and extinguishing the spontaneous combustion of coal gangue. Based on the heat transfer theory, the resistance network of the coal-HP heat removal system was analyzed for studying the cooling effect of HP. The experimental results show that the HP can accelerate the heat release in coal gangue pile. The coal temperature could be controlled at 59.6 ˚ C with HP in 7 h and the highest cooling value is 39.4 % with HP in 150 h, which can effectively cool the temperatures of high temperature zones. As a powerful heat transfer components, as soon as HPs were inserted into the CGH with a reasonable distance, it can completely play a vital role in inhibiting the coal self-ignition process.

Numerical analysis of conjugate heat transfer due to oblique impingement of turbulent slot jet onto a flat plate

NASA Astrophysics Data System (ADS)

Shashikant, Patel, Devendra Kumar; Kumar, Jayesh; Kumar, Vishwajeet

2018-04-01

The conjugate heat transfer due to oblique impingement of two-dimensional, steady state, incompressible, turbulent slot jet on a uniformly heated flat plate has been studied in the present work. The standard high Reynolds number two-equation k - ɛ eddy viscosity model has been used for numerical simulation. The Reynolds number based on the hydraulic diameter of nozzle exit and turbulent intensity maintained at 9, 900 and 2% respectively. The angle of inclination 30°, 45°, 60° and, 75° degrees are considered for the numerical study. A uniform temperature higher than the jet exit temperature is provided to the bottom surface of the plate. The flow field have been studied using the contour plots of pressure and velocity in the fluid domain. The influence of inclination on the distribution of the local Nusselt number over the surface of impingement have been presented. It is found that the angle of impingement influences the flow field and heat transfer characteristics more in the downhill direction of the stagnation zone compared to the uphill direction.

Design and performance considerations of evaporative-pad, waste-heat greenhouses

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

Olszewski, M.

1978-01-01

Rising fuel costs and limited fuel availability have forced greenhouse operators to seek alternative means of heating their greenhouses in an effort to reduce production costs and conserve energy. One such alternative uses power plant reject heat, which is contained in the condenser cooling water, and a bank of evaporative pads to provide winter heating. The design technique used to size the evaporative pad system to meet both summer cooling and winter heating demands is described. Additionally, a computational scheme that simulates the system performance is presented. This analytical model is used to determine the greenhouse operating conditions that maintainmore » the vegetation in its thermal comfort zone. The evaporative pad model uses the Merkel total heat approximation and an experimentally derived transfer coefficient. Energy balance considerations on the vegetation provide a means of viewing optimal vegetation growth in terms of greenhouse environmental factors. In general, the results indicate that the vegetation can be maintained within its thermal comfort zone if sufficient warm water is available to the pads and the air stream flow is properly adjusted.« less

Salt loaded heat pipes: steady-state operation and related heat and mass transport

NASA Astrophysics Data System (ADS)

Simakin, A.; Ghassemi, A.

2003-10-01

Fluids in the deep-seated zones (3.5-4.5 km) of active geothermal zones are known to have increased salinity and acidity that can enhance interaction with surrounding porous rocks. A possible mechanism for brine generation is the separation of the rising magmatic fluid into a gas-like and a liquid-like component. This work illustrates the main features of this mechanism by investigating the conditions for heat pipe convection of natural brines in hydrothermal systems. The well-established heat pipe regime for convection of two-phase pure water (vapor-liquid) in a porous column is extended to the case of boiling brines. In particular, the NaCl-H 2O system is used to model the 1-D reactive flow with dissolution-precipitation in geothermal reservoirs. The quasi steady-state equations of the conservation of matter, Darcy's law for the gas and liquid phases, and the heat balance equation have been examined while neglecting the temporal variation of porosity. A semi-analytical procedure is used to solve these equations for a two-phase fluid in equilibrium with a solid salt. The solution is in the form of the dependence of liquid volume fraction as a function of temperature for different heat fluxes. The solution is separated into two isolated regions by the temperature T=596°C, at the maximum fluid pressure for three-phase (H-L-V) equilibrium. In the case of unsaturated two-phase flow at the reference permeability of porous rocks (3·10 -16 m 2), the maximum heat flux that can be transferred through the porous column via convection is analytically estimated to be 4.3 W/m 2. This is close to the corresponding value for the three-phase case that is numerically calculated to be 6 W/m 2. Due to dissolution (partial leaching of oxide components by acid condensates) and precipitation of salt at the boiling front, heat transfer in a heat pipe in soluble media occurs in a direction opposite to the associated mass transfer. This can cause deep hydrothermal karsting that is manifested as surface subsidence at rates of about several cm/yr as observed in some active geothermal fields.

Control of final moisture content of food products baked in continuous tunnel ovens

NASA Astrophysics Data System (ADS)

McFarlane, Ian

2006-02-01

There are well-known difficulties in making measurements of the moisture content of baked goods (such as bread, buns, biscuits, crackers and cake) during baking or at the oven exit; in this paper several sensing methods are discussed, but none of them are able to provide direct measurement with sufficient precision. An alternative is to use indirect inferential methods. Some of these methods involve dynamic modelling, with incorporation of thermal properties and using techniques familiar in computational fluid dynamics (CFD); a method of this class that has been used for the modelling of heat and mass transfer in one direction during baking is summarized, which may be extended to model transport of moisture within the product and also within the surrounding atmosphere. The concept of injecting heat during the baking process proportional to the calculated heat load on the oven has been implemented in a control scheme based on heat balance zone by zone through a continuous baking oven, taking advantage of the high latent heat of evaporation of water. Tests on biscuit production ovens are reported, with results that support a claim that the scheme gives more reproducible water distribution in the final product than conventional closed loop control of zone ambient temperatures, thus enabling water content to be held more closely within tolerance.

Numerical simulation of multiple-physical fields coupling for thermal anomalies before earthquakes: A case study of the 2008 Wenchuan Ms8.0 earthquake in southwest China

NASA Astrophysics Data System (ADS)

Deng, Z.

2017-12-01

It has become a highly focused issue that thermal anomalies appear before major earthquakes. There are various hypotheses about the mechanism of thermal anomalies. Because of lacking of enough evidences, the mechanism is still require to be further researched. Gestation and occurrence of a major earthquake is related with the interaction of multi-physical fields. The underground fluid surging out the surface is very likely to be the reason for the thermal anomaly. This study tries to answer some question, such as how the geothermal energy transfer to the surface, and how the multiple-physical fields interacted. The 2008 Wenchuan Ms8.0 earthquake, is one of the largest evens in the last decade in China mainland. Remote sensing studies indicate that distinguishable thermal anomalies occurred several days before the earthquake. The heat anomaly value is more than 3 times the average in normal time and distributes along the Longmen Shan fault zone. Based on geological and geophysical data, 2D dynamic model of coupled stress, seepage and thermal fields (HTM model) is constructed. Then using the COMSOL multi-physics filed software, this work tries to reveal the generation process and distribution patterns of thermal anomalies prior to thrust-type major earthquakes. The simulation get the results: (1)Before the micro rupture, with the increase of compression, the heat current flows to the fault in the footwall on the whole, while in the hanging wall of the fault, particularly near the ground surface, the heat flow upward. In the fault zone, heat flow upward along the fracture surface, heat flux in the fracture zone is slightly larger than the wall rock;, but the value is all very small. (2)After the occurrence of the micro fracture, the heat flow rapidly collects to the faults. In the fault zones, the heat flow accelerates up along the fracture surfaces, the heat flux increases suddenly, and the vertical heat flux reaches to the maximum. The heat flux in the 3 fracture zones is obviously larger than that in the non fracture zone. The high heat flux anomaly can continue several days to one month. The simulation results is consistent with the reality earthquake cases.

Individual thermal profiles as a basis for comfort improvement in space and other environments

NASA Technical Reports Server (NTRS)

Koscheyev, V. S.; Coca, A.; Leon, G. R.; Dancisak, M. J.

2002-01-01

BACKGROUND: The development of individualized countermeasures to address problems in thermoregulation is of considerable importance for humans in space and other extreme environments. A methodology is presented for evaluating minimal/maximal heat flux from the total human body and specific body zones, and for assessing individual differences in the efficiency of heat exchange from these body areas. The goal is to apply this information to the design of individualized protective equipment. METHODS: A multi-compartment conductive plastic tubing liquid cooling/warming garment (LCWG) was developed. Inlet water temperatures of 8-45 degrees C were imposed sequentially to specific body areas while the remainder of the garment was maintained at 33 degrees C. RESULTS: There were significant differences in heat exchange level among body zones in both the 8 degrees and 45 degrees C temperature conditions (p < 0.001). The greatest amount of heat was absorbed/released by the following areas: thighs (8 degrees C: -2.12 +/- 0.14 kcal min(-1); 45 degrees C: +1.58 +/- 0.23); torso (8 degrees C: -2.12 +/- 0.13 kcal min(-1); 45 degrees C: +1.31 +/- 0.27); calves (8 degrees C: -1.59 +/- 0.26 kcal min(-1); 45 degrees C: +1.53 +/- 0.24); and forearms (8 degrees C: -1.67 +/- 0.29 kcal x min(-1); 45 degrees C: +1.45 +/- 0.20). These are primarily zones with relatively large muscle mass and adipose tissue. Calculation of absorption/release heat rates standardized per unit tube length and flow rate instead of zonal surface area covered showed that there was significantly greater heat transfer in the head, hands, and feet (p < 0.001). The areas in which there was considerable between-subject variability in rates of heat transfer and thus most informative for individual profile design were the torso, thighs, shoulders, and calves or forearms. CONCLUSIONS: The methodology developed is sensitive to individual differences in the process of heat exchange and variations in different body areas, depending on their size and tissue mass content. The design of individual thermal profiles is feasible for better comfort of astronauts on long-duration missions and personnel in other extreme environments.

Influence of rainfalls on heat and steam fluxes of fumarolic zones: Six months records along the Ty fault (Soufrière of Guadeloupe, Lesser Antilles)

NASA Astrophysics Data System (ADS)

Gaudin, Damien; Finizola, Anthony; Delcher, Eric; Beauducel, François; Allemand, Pascal; Delacourt, Christophe; Brothelande, Elodie; Peltier, Aline; Di Gangi, Fabio

2015-09-01

Fumarolic zones are permeable areas where both steam and heat are expelled to the atmosphere. Surface fluxes and flows, which are representative of the intensity of the hydrothermal circulation in depth, can be monitored by thermometers, thermal infrared cameras, spectrometers, or condensers. However, the superficial activity of fumarolic zones can be modified by the meteorological conditions, in particular the rainfalls, which might result in erroneous estimations. From this perspective, we developed a set of physical equations to quantify the effects of rainfalls on the thermal behavior of fumarolic zones. Results were faced to continuous measurements achieved at the Ty fault fumarolic zone (La Soufrière volcano, Guadeloupe, Lesser Antilles) during six months in 2010, using six vertical series of thermometers measuring the heat transfer in the ground and one condenser measuring the rising steam flux. Results demonstrate that in the absence of rainfalls, heat and steam flux reach an equilibrium that is representative of the geothermal flux in depth. Conversely, after the rainfalls, the cooling of the ground provokes a deepening of the condensation level. The related soil temperature drop can be estimated by computing the heat required to warm the infiltrated water up to boiling temperature while the recovery rate is directly linked to the geothermal flux. Our observations allow defining in which conditions flux are at steady state, but also to build a first-order numerical model allowing estimating both the physical parameters of the ground (thermal conductivity, precipitation efficiency coefficient and surface flux constant) and the long-term thermal behavior of the hydrothermal system. In particular, our results predict that the hydrothermal activity must vanish on the zones where the geothermal flux drops under a certain threshold (60 W/m2 at La Soufrière). The existence of this limit may have strong implications for the precipitation rate of minerals and the possible reactivation of the fumarolic zones during volcanic crises.

Progress in catalytic ignition fabrication, modeling and infrastructure : (part 2) development of a multi-zone engine model simulated using MATLAB software.

DOT National Transportation Integrated Search

2014-02-01

A mathematical model was developed for the purpose of providing students with data : acquisition and engine modeling experience at the University of Idaho. In developing the : model, multiple heat transfer and emissions models were researched and com...

Numerical modelling of convective heat transport by air flow in permafrost talus slopes

NASA Astrophysics Data System (ADS)

Wicky, Jonas; Hauck, Christian

2017-06-01

Talus slopes are a widespread geomorphic feature in the Alps. Due to their high porosity a gravity-driven internal air circulation can be established which is forced by the gradient between external (air) and internal (talus) temperature. The thermal regime is different from the surrounding environment, leading to the occurrence of permafrost below the typical permafrost zone. This phenomenon has mainly been analysed by field studies and only few explicit numerical modelling studies exist. Numerical simulations of permafrost sometimes use parameterisations for the effects of convection but mostly neglect the influence of convective heat transfer in air on the thermal regime. In contrast, in civil engineering many studies have been carried out to investigate the thermal behaviour of blocky layers and to improve their passive cooling effect. The present study further develops and applies these concepts to model heat transfer in air flows in a natural-scale talus slope. Modelling results show that convective heat transfer has the potential to develop a significant temperature difference between the lower and the upper parts of the talus slope. A seasonally alternating chimney-effect type of circulation develops. Modelling results also show that this convective heat transfer leads to the formation of a cold reservoir in the lower part of the talus slope, which can be crucial for maintaining the frozen ground conditions despite increasing air temperatures caused by climate change.

Optimization for energy efficiency of underground building envelope thermal performance in different climate zones of China

NASA Astrophysics Data System (ADS)

Shi, Luyang; Liu, Jing; Zhang, Huibo

2017-11-01

The object of this article is to investigate the influence of thermal performance of envelopes in shallow-buried buildings on energy consumption for different climate zones of China. For the purpose of this study, an effective building energy simulation tool (DeST) developed by Tsinghua University was chosen to model the heat transfer in underground buildings. Based on the simulative results, energy consumption for heating and cooling for the whole year was obtained. The results showed that the relationship between energy consumption and U-value of envelopes for underground buildings is different compared with above-ground buildings: improving thermal performance of exterior walls cannot reduce energy consumption, on the contrary, may result in more energy cost. Besides, it is can be derived that optimized U-values of underground building envelopes vary with climate zones of China in this study. For severe cold climate zone, the optimized U-value of underground building envelopes is 0.8W/(m2·K); for cold climate zone, the optimized U-value is 1.5W/(m2·K); for warm climate zone, the U-value is 2.0W/(m2·K).

Numerical investigation of mist/air impingement cooling on ribbed blade leading-edge surface.

PubMed

Bian, Qingfei; Wang, Jin; Chen, Yi-Tung; Wang, Qiuwang; Zeng, Min

2017-12-01

The working gas turbine blades are exposed to the environment of high temperature, especially in the leading-edge region. The mist/air two-phase impingement cooling has been adopted to enhance the heat transfer on blade surfaces and investigate the leading-edge cooling effectiveness. An Euler-Lagrange particle tracking method is used to simulate the two-phase impingement cooling on the blade leading-edge. The mesh dependency test has been carried out and the numerical method is validated based on the available experimental data of mist/air cooling with jet impingement on a concave surface. The cooling effectiveness on three target surfaces is investigated, including the smooth and the ribbed surface with convex/concave columnar ribs. The results show that the cooling effectiveness of the mist/air two-phase flow is better than that of the single-phase flow. When the ribbed surfaces are used, the heat transfer enhancement is significant, the surface cooling effectiveness becomes higher and the convex ribbed surface presents a better performance. With the enhancement of the surface heat transfer, the pressure drop in the impingement zone increases, but the incremental factor of the flow friction is smaller than that of the heat transfer enhancement. Copyright © 2017 Elsevier Ltd. All rights reserved.

The development and investigation of a strongly non-equilibrium model of heat transfer in fluid with allowance for the spatial and temporal non-locality and energy dissipation

NASA Astrophysics Data System (ADS)

Kudinov, V. A.; Eremin, A. V.; Kudinov, I. V.

2017-11-01

The differential equation of heat transfer with allowance for energy dissipation and spatial and temporal nonlocality has been derived by the relaxation of heat flux and temperature gradient in the Fourier law formula for the heat flux at the use of the heat balance equation. An investigation of the numerical solution of the heat-transfer problem at a laminar fluid flow in a plane duct has shown the impossibility of an instantaneous acceptance of the boundary condition of the first kind — the process of its settling at small values of relaxation coefficients takes a finite time interval the duration of which is determined by the thermophysical and relaxation properties of the fluid. At large values of relaxation coefficients, the use of the boundary condition of the first kind is possible only at Fo → ∞. The friction heat consideration leads to the alteration of temperature profiles, which is due to the rise of the intervals of elevated temperatures in the zone of the maximal velocity gradients. With increasing relaxation coefficients, the smoothing of temperature profiles occurs, and at their certain high values, the fluid cooling occurs at a gradientless temperature variation along the transverse spatial variable and, consequently, the temperature proves to be dependent only on time and on longitudinal coordinate.

Impact of permafrost development on groundwater flow patterns: a numerical study considering freezing cycles on a two-dimensional vertical cut through a generic river-plain system

NASA Astrophysics Data System (ADS)

Grenier, Christophe; Régnier, Damien; Mouche, Emmanuel; Benabderrahmane, Hakim; Costard, François; Davy, Philippe

2013-02-01

The impact of glaciation cycles on groundwater flow was studied within the framework of nuclear waste storage in underground geological formations. The eastern section of the Paris Basin (a layered aquifer with impervious/pervious alternations) in France was considered for the last 120 ka. Cold periods corresponded with arid climates. The issue of talik development below water bodies was addressed. These unfrozen zones can maintain open pathways for aquifer recharge. Transient thermal evolution was simulated on a small-scale generic unit of the landscape including a "river" and "plain". Coupled thermo-hydraulic modeling and simplified conductive heat transfer were considered for a broad range of scenarios. The results showed that when considering the current limited river dimensions and purely conductive heat transfer, taliks are expected to close within a few centuries. However, including coupled advection for flows from the river to the plain (probably pertinent for the eastern Paris Basin aquifer recharge zones) strongly delays talik closure (millennium scale). The impact on regional underground flows is expected to vary from a complete stop of recharge to a reduced recharge, corresponding to the talik zones. Consequences for future modeling approaches of the Paris Basin are discussed.

Matrix-assisted energy conversion in nanostructured piezoelectric arrays

DOEpatents

Sirbuly, Donald J.; Wang, Xianying; Wang, Yinmin

2013-01-01

A nanoconverter is capable of directly generating electricity through a nanostructure embedded in a polymer layer experiencing differential thermal expansion in a stress transfer zone. High surface-to-volume ratio semiconductor nanowires or nanotubes (such as ZnO, silicon, carbon, etc.) are grown either aligned or substantially vertically aligned on a substrate. The resulting nanoforest is then embedded with the polymer layer, which transfers stress to the nanostructures in the stress transfer zone, thereby creating a nanostructure voltage output due to the piezoelectric effect acting on the nanostructure. Electrodes attached at both ends of the nanostructures generate output power at densities of .about.20 nW/cm.sup.2 with heating temperatures of .about.65.degree. C. Nanoconverters arrayed in a series parallel arrangement may be constructed in planar, stacked, or rolled arrays to supply power to nano- and micro-devices without use of external batteries.

Turbulent Mixing and Vertical Heat Transfer in the Surface Mixed Layer of the Arctic Ocean: Implication of a Cross-Pycnocline High-Temperature Anomaly

NASA Astrophysics Data System (ADS)

Kawaguchi, Yusuke; Takeda, Hiroki

2017-04-01

This study focuses on the mixing processes in the vicinity of surface mixed layer (SML) of the Arctic Ocean. Turbulence activity and vertical heat transfer are quantitatively characterized in the Northwind Abyssal Plain, based on the RV Mirai Arctic cruise, during the transition from late summer to early winter 2014. During the cruise, noticeable storm events were observed, which came over the ship's location and contributed to the deepening of the SML. According to the ship-based microstructure observation, within the SML, the strong wind events produced enhanced dissipation rates of turbulent kinetic energy in the order of magnitude of ɛ = 10-6-10-4W kg-1. On thermal variance dissipation rate, χ increases toward the base of SML, reaching O(10-7) K2 s-1, resulting in vertical heat flux of O(10) W m-2. During the occasional energetic mixing events, the near-surface warm water was transferred downward and penetrated through the SML base, creating a cross-pycnocline high-temperature anomaly (CPHTA) at approximately 20-30 m depth. Near CPHTA, the vertical heat flux was anomalously magnified to O(10-100) W m-2. Following the fixed-point observation, in the regions of marginal and thick ice zones, the SML heat content was monitored using an autonomous drifting buoy, UpTempO. During most of the ice-covered period, the ocean-to-ice turbulent heat flux was dominant, rather than the diapycnal heat transfer across the SML bottom interface.

Computational Modeling of Microstructural-Evolution in AISI 1005 Steel During Gas Metal Arc Butt Welding

NASA Astrophysics Data System (ADS)

Grujicic, M.; Ramaswami, S.; Snipes, J. S.; Yavari, R.; Arakere, A.; Yen, C.-F.; Cheeseman, B. A.

2013-05-01

A fully coupled (two-way), transient, thermal-mechanical finite-element procedure is developed to model conventional gas metal arc welding (GMAW) butt-joining process. Two-way thermal-mechanical coupling is achieved by making the mechanical material model of the workpiece and the weld temperature-dependent and by allowing the potential work of plastic deformation resulting from large thermal gradients to be dissipated in the form of heat. To account for the heat losses from the weld into the surroundings, heat transfer effects associated with natural convection and radiation to the environment and thermal-heat conduction to the adjacent workpiece material are considered. The procedure is next combined with the basic physical-metallurgy concepts and principles and applied to a prototypical (plain) low-carbon steel (AISI 1005) to predict the distribution of various crystalline phases within the as-welded material microstructure in different fusion zone and heat-affected zone locations, under given GMAW-process parameters. The results obtained are compared with available open-literature experimental data to provide validation/verification for the proposed GMAW modeling effort.

Process for operating equilibrium controlled reactions

DOEpatents

Nataraj, Shankar; Carvill, Brian Thomas; Hufton, Jeffrey Raymond; Mayorga, Steven Gerard; Gaffney, Thomas Richard; Brzozowski, Jeffrey Richard

2001-01-01

A cyclic process for operating an equilibrium controlled reaction in a plurality of reactors containing an admixture of an adsorbent and a reaction catalyst suitable for performing the desired reaction which is operated in a predetermined timed sequence wherein the heating and cooling requirements in a moving reaction mass transfer zone within each reactor are provided by indirect heat exchange with a fluid capable of phase change at temperatures maintained in each reactor during sorpreaction, depressurization, purging and pressurization steps during each process cycle.

The Coupling of Macrosegregation with Grain Nucleation, Growth and Motion in DC Cast Aluminum Alloy Ingots

NASA Astrophysics Data System (ADS)

Založnik, Miha; Kumar, Arvind; Combeau, Hervé; Bedel, Marie; Jarry, Philippe; Waz, Emmanuel

The phenomena responsible for the formation of macrosegregations, and grain structures during solidification are closely intertwined. We present a model study of the formation of macrosegregation and grain structure in an industrial sized (350 mm thick) direct chill (DC) cast aluminum alloy slab. The modeling of these phenomena in DC casting is a challenging problem mainly due to the size of the products, the variety of the phenomena to be accounted for, and the non-linearities involved. We used a volume-averaged multiscale model that describes nucleation on grain refiner particles and grain growth, coupled with macroscopic transport: fluid flow driven by natural convection and shrinkage, transport of free-floating globular equiaxed grains, heat transfer, and solute transport. We analyze the heat and mass transfer in the slurry moving-grain zone that is a result of the coupling of the fluid flow and of the grain nucleation, growth and motion. We discuss the impact of the flow structure in the slurry zone and of the grain packing fraction on the macrosegregation.

High-efficiency condenser of steam from a steam-gas mixture

NASA Astrophysics Data System (ADS)

Milman, O. O.; Krylov, V. S.; Ptakhin, A. V.; Kondratev, A. V.; Yankov, G. G.

2017-12-01

The design of a module for a high-efficiency condenser of steam with a high content (up to 15%) of noncondensable gases (NCGs) with a nearly constant steam-gas mixture (SGM) velocity during the condensation of steam has been developed. This module provides the possibility to estimate the operational efficiency of six condenser zones during the motion of steam from the inlet to the SGM suction point. Some results of the experimental tests of the pilot high-efficiency condenser module are presented. The dependence of the average heat transfer coefficient k¯ on the volumetric NCG concentration v¯ has been derived. It is shown that the high-efficiency condenser module can provide a moderate decrease in k¯ from 4400-4600 to 2600-2800 W/(m2 K) at v¯ ≈ 0.5-9.0%. The heat transfer coefficient distribution over different module zones at a heat duty close to its nominal value has been obtained. From this distribution, it can be seen that the average heat transfer coefficient decreases to 2600 W/(m2 K) at an NCG concentration v¯ = 7.5%, but the first condenser sections ( 1- 3) retain high values of k¯ at a level of no lower than 3200 W/(m2 K), and the last sections operate less well, having k¯ at a level of 1700 W/(m2 K). The dependence of the average heat transfer coefficient on the water velocity in condenser tubes has been obtained at a nearly nominal duty such that the extrapolation of this dependence to the water velocity of 2 m/s may be expected to give k¯ = 5000 W/(m2 K) for relatively pure steam, but an increase in k¯ at v¯ = 8% will be smaller. The effect of the gas removal device characteristic on the operation of the high-efficiency condenser module is described. The design developed for the steam condenser of a gas-turbine plant with a power of 25 MW, a steam flow rate of 40.2 t/h, and a CO2 concentration of up to 12% with consideration for the results of performed studies is presented.

High-pressure calorimeter chamber tests for liquid oxygen/kerosene (LOX/RP-1) rocket combustion

NASA Technical Reports Server (NTRS)

Masters, Philip A.; Armstrong, Elizabeth S.; Price, Harold G.

1988-01-01

An experimental program was conducted to investigate the rocket combustion and heat transfer characteristics of liquid oxygen/kerosene (LOX/RP-1) mixtures at high chamber pressures. Two water-cooled calorimeter chambers of different combustion lengths were tested using 37- and 61-element oxidizer-fuel-oxidizer triplet injectors. The tests were conducted at nominal chamber pressures of 4.1, 8.3, and 13.8 MPa abs (600, 1200, and 2000 psia). Heat flux Q/A data were obtained for the entire calorimeter length for oxygen/fuel mixture ratios of 1.8 to 3.3. Test data at 4.1 MPa abs compared favorably with previous test data from another source. Using an injector with a fuel-rich outer zone reduced the throat heat flux by 47 percent with only a 4.5 percent reduction in the characteristic exhaust velocity efficiency C* sub eff. The throat heat transfer coefficient was reduced approximately 40 percent because of carbon deposits on the chamber wall.

Hot air impingement on a flat plate using Large Eddy Simulation (LES) technique

NASA Astrophysics Data System (ADS)

Plengsa-ard, C.; Kaewbumrung, M.

2018-01-01

Impinging hot gas jets to a flat plate generate very high heat transfer coefficients in the impingement zone. The magnitude of heat transfer prediction near the stagnation point is important and accurate heat flux distribution are needed. This research studies on heat transfer and flow field resulting from a single hot air impinging wall. The simulation is carried out using computational fluid dynamics (CFD) commercial code FLUENT. Large Eddy Simulation (LES) approach with a subgrid-scale Smagorinsky-Lilly model is present. The classical Werner-Wengle wall model is used to compute the predicted results of velocity and temperature near walls. The Smagorinsky constant in the turbulence model is set to 0.1 and is kept constant throughout the investigation. The hot gas jet impingement on the flat plate with a constant surface temperature is chosen to validate the predicted heat flux results with experimental data. The jet Reynolds number is equal to 20,000 and a fixed jet-to-plate spacing of H/D = 2.0. Nusselt number on the impingement surface is calculated. As predicted by the wall model, the instantaneous computed Nusselt number agree fairly well with experimental data. The largest values of calculated Nusselt number are near the stagnation point and decrease monotonically in the wall jet region. Also, the contour plots of instantaneous values of wall heat flux on a flat plate are captured by LES simulation.

Dissipation of Electrical Energy in Submerged Arc Furnaces Producing Silicomanganese and High-Carbon Ferromanganese

NASA Astrophysics Data System (ADS)

Steenkamp, Joalet Dalene; Hockaday, Christopher James; Gous, Johan Petrus; Nzima, Thabo Witness

2017-09-01

Submerged-arc furnace technology is applied in the primary production of ferroalloys. Electrical energy is dissipated to the process via a combination of arcing and resistive heating. In processes where a crater forms between the charge zone and the reaction zone, electrical energy is dissipated mainly through arcing, e.g., in coke-bed based processes, through resistive heating. Plant-based measurements from a device called "Arcmon" indicated that in silicomanganese (SiMn) production, at times up to 15% of the electrical energy used is transferred by arcing, 30% in high-carbon ferromanganese (HCFeMn) production, compared with 5% in ferrochromium and 60% in ferrosilicon production. On average, the arcing is much less at 3% in SiMn and 5% in HCFeMn production.

Natural convection heat transfer in water near its density maximum

NASA Astrophysics Data System (ADS)

Yen, Yin-Chao

1990-12-01

This monograph reviews and summarizes to date the experimental and analytical results on the effect of water density near its maximum convection, transient flow and temperature structure characteristics: (1) in a vertical enclosure; (2) in a vertical annulus; (3) between horizontal concentric cylinders; (4) in a square enclosure; (5) in a rectangular enclosure; (6) in a horizontal layer; (7) in a circular confined melt layer; and (8) in bulk water during melting. In a layer of water containing a maximum density temperature of 4 C, the onset of convection (the critical number) is found not to be a constant value as in the classical normal fluid but one that varies with the imposed thermal and hydrodynamic boundaries. In horizontal layers, a nearly constant temperature zone forms and continuously expands between the warm and cold boundaries. A minimum heat transfer exists in most of the geometries studied and, in most cases, can be expressed in terms of a density distribution parameter. The effect of this parameter on a cells formation, disappearance and transient structure is discussed, and the effect of split boundary flow on heat transfer is presented.

Solar retorting of oil shale

DOEpatents

Gregg, David W.

1983-01-01

An apparatus and method for retorting oil shale using solar radiation. Oil shale is introduced into a first retorting chamber having a solar focus zone. There the oil shale is exposed to solar radiation and rapidly brought to a predetermined retorting temperature. Once the shale has reached this temperature, it is removed from the solar focus zone and transferred to a second retorting chamber where it is heated. In a second chamber, the oil shale is maintained at the retorting temperature, without direct exposure to solar radiation, until the retorting is complete.

Numerical investigation of roughness effects in aircraft icing calculations

NASA Astrophysics Data System (ADS)

Matheis, Brian Daniel

2008-10-01

Icing codes are playing a role of increasing significance in the design and certification of ice protected aircraft surfaces. However, in the interest of computational efficiency certain small scale physics of the icing problem are grossly approximated by the codes. One such small scale phenomena is the effect of ice roughness on the development of the surface water film and on the convective heat transfer. This study uses computational methods to study the potential effect of ice roughness on both of these small scale phenomena. First, a two-dimensional condensed layer code is used to examine the effect of roughness on surface water development. It is found that the Couette approximation within the film breaks down as the wall shear goes to zero, depending on the film thickness. Roughness elements with initial flow separation in the air induce flow separation in the water layer at steady state, causing a trapping of the film. The amount of trapping for different roughness configurations is examined. Second, a three-dimensional incompressible Navier-Stokes code is developed to examine large scale ice roughness on the leading edge. The effect on the convective heat transfer and potential effect on the surface water dynamics is examined for a number of distributed roughness parameters including Reynolds number, roughness height, streamwise extent, roughness spacing and roughness shape. In most cases the roughness field increases the net average convective heat transfer on the leading edge while narrowing surface shear lines, indicating a choking of the surface water flow. Both effects show significant variation on the scale of the ice roughness. Both the change in heat transfer as well as the potential change in surface water dynamics are presented in terms of the development of singularities in the surface shear pattern. Of particular interest is the effect of the smooth zone upstream of the roughness which shows both a relatively large increase in convective heat transfer as well as excessive choking of the surface shear lines at the upstream end of the roughness field. A summary of the heat transfer results is presented for both the averaged heat transfer as well as the maximum heat transfer over each roughness element, indicating that the roughness Reynolds number is the primary parameter which characterizes the behavior of the roughness for the problem of interest.

Boundary layer development as a function of chamber pressure in the NASA Lewis 1030:1 area ratio rocket nozzle

NASA Technical Reports Server (NTRS)

Smith, Tamara A.

1988-01-01

Through the use of theoretical predictions of fluid properties and experimental heat transfer and thrust measurements, the zones of laminar, transitional, and turbulent boundary layer flow were defined for the NASA Lewis 1039:1 area ratio rocket nozzle. Tests were performed on the nozzle at chamber pressures from 350 to 100 psia. For these conditions, the throat diameter Reynolds numbers varied from 300,000 to 1 million. The propellants used were gaseous hydrogen and gaseous oxygen. Thrust measurements and nozzle outer wall temperature measurements were taken during the 3-sec test runs. Comparison of experimental heat transfer and thrust data with the corresponding predictions from the Two-Dimensional Kinetics (TDK) nozzle analysis program indicated laminar flow in the nozzle at a throat diameter Reynolds number of 320,000 or chamber pressure of 360 psia. Comparison of experimental and predicted heat transfer data indicated transitional flow up to and including a chamber pressure of 1000 psia. Predicted values of the axisymmetric acceleration parameter within the convergent and divergent nozzle were consistent with the above results. Based upon an extrapolation of the heat transfer data and predicted distributions of the axisymmetric acceleration parameter, transitional flow was predicted up to a throat diameter Reynolds number of 220,000 or 2600-psia chamber pressure. Above 2600-psia chamber pressure, fully developed turbulent flow was predicted.

Boundary layer development as a function of chamber pressure in the NASA Lewis 1030:1 area ratio rocket nozzle

NASA Technical Reports Server (NTRS)

Smith, Tamara A.

1988-01-01

Through the use of theoretical predictions of fluid properties and experimental heat transfer and thrust measurements, the zones of laminar, transitional, and turbulent boundary layer flow were defined for the NASA Lewis 1030:1 area ratio rocket nozzle. Tests were performed on the nozzle at chamber pressures from 350 to 100 psia. For these conditions, the throat diameter Reynolds numbers varied from 300,000 to 1 million. The propellants used were gaseous hydrogen and gaseous oxygen. Thrust measurements and nozzle outer wall temperature measurements were taken during the 3-sec test runs. Comparison of experimental heat transfer and thrust data with the corresponding predictions from the Two-Dimensional Kinetics (TDK) nozzle analysis program indicated laminar flow in the nozzle at a throat diameter Reynolds number of 320,000 or chamber pressure of 360 psia. Comparison of experimental and predicted heat transfer data indicated transitional flow up to and including a chamber pressure of 1000 psia. Predicted values of the axisymmetric acceleration parameter within the convergent and divergent nozzle were consistent with the above results. Based upon an extrapolation of the heat transfer data and predicted distributions of the axisymmetric acceleration parameter, transitional flow was predicted up to a throat diameter Reynolds number of 220,000 or 2600-psia chamber pressure. Above 2600-psia chamber pressure, fully developed turbulent flow was predicted.

Heat and mass transfer at gas-phase ignition of grinded coal layer by several metal particles heated to a high temperature

NASA Astrophysics Data System (ADS)

Glushkov, D. O.; Kuznetsov, G. V.; Strizhak, P. A.

2017-07-01

Characteristics of gas-phase ignition of grinded brown coal (brand 2B, Shive-Ovoos deposit in Mongolia) layer by single and several metal particles heated to a high temperature (above 1000 K) have been investigated numerically. The developed mathematical model of the process takes into account the heating and thermal decomposition of coal at the expense of the heat supplied from local heat sources, release of volatiles, formation and heating of gas mixture and its ignition. The conditions of the joint effect of several hot particles on the main characteristic of the process-ignition delay time are determined. The relation of the ignition zone position in the vicinity of local heat sources and the intensity of combustible gas mixture warming has been elucidated. It has been found that when the distance between neighboring particles exceeds 1.5 hot particle size, an analysis of characteristics and regularities of coal ignition by several local heat sources can be carried out within the framework of the model of "single metal particle / grinded coal / air". Besides, it has been shown with the use of this model that the increase in the hot particle height leads, along with the ignition delay time reduction, to a reduction of the source initial temperatures required for solid fuel ignition. At an imperfect thermal contact at the interface hot particle / grinded coal due to the natural porosity of the solid fuel structure, the intensity of ignition reduces due to a less significant effect of radiation in the area of pores on the heat transfer conditions compared to heat transfer by conduction in the near-surface coal layer without regard to its heterogeneous structure.

Application of a stepwise method for analyzing fouling in shell-and-tube exchangers

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

Prieto, M.M.; Miranda, J.; Sigales, B.

1999-12-01

This article presents the results of the application of a quite simple method for analyzing shell-side fouling in shell-and-tube exchangers, capable of taking into account the formation or irregular fouling deposits with variable thermal conductivity. This method, based on the utilization of elementary heat exchangers, has been implemented for E-shell TEMA-type heat exchangers with two tube passes. Several fouling deposit distributions have been simulated so as to ascertain their effects on the heat transfer rate. These distributions consider that fouling is concentrated in zones where the temperature of the fluids is maximum or minimum.

Geochronologic Constraints on Duration of Magma Emplacement and Heat Transfer in the Deep Crust: new data from the Ivrea Zone, Western Alps, Italy

NASA Astrophysics Data System (ADS)

Peressini, G.; Quick, J. E.; Poller, U.; Todt, W.; Mayer, A.; Sinigoi, S.; Hofmann, A. W.

2002-12-01

The Mafic Complex (MC) of the Ivrea Zone is one of the largest gabbro bodies in the Alps (ca 8 km thick and 30 km long); it intruded the already metamorphic volcano-sedimentary sequence of the Kinzigite Formation (KF) at a depth of more than 20 km during the Late Paleozoic. New geochronologic data constrain the duration of the intrusion. The crustal section, uplifted, tilted and exposed in Alpine time, is tectonically bounded, but essentially undisturbed by Alpine tectonics; the internal structure of the MC and its relations with the KF are well preserved. Intrusion of the MC in extending continental crust is suggested by pre-Triassic, high-T, extensional shear zones in the Ivrea Zone, and is consistent with the internal arcuate structure of the MC, which is defined by high-T foliation and banding, that are discordant to the roof of the intrusion. Rocks in the roof of the MC attain upper-amphibolite grade and show evidence of partial melting within about 2 km of the MC. The country rock was melted as a consequence of heat released by the crystallizing mafic body; the chemistry of the mafic rocks was affected by up to 30% crustal contamination that occurred partially in situ, by mixing of the basaltic melts with anatectic melts derived from depleted crustal rocks. A thin (less than 20 m) seam of leucogranite crystallized from anatectic melt is present at the MC-KF contact. Syntectonic intrusion of leucogranite along shear zones within the KF demonstrates migration of anatectic melts to higher crustal levels. U/Pb SHRIMP ages on magmatic zircons range from 295+4 and 287+4 Ma for the MC, and 280+4 Ma for syntectonic leucogranites in the KF. Thus, intrusion of the MC may have taken as long as 10-15 Ma. Nd-Sm mineral isochrones for the MC range from 244 to 274, indicating that the Complex cooled to temperatures below 750C within about 40 Ma of final crystallization. The heat of crystallization of the MC was accommodated by anatexis and assimilation, and syntectonic migration of anatectic melts transferred heat to higher crustal levels.

Laboratory Experiments Lead to a New Understanding of Wildland Fire Spread

NASA Astrophysics Data System (ADS)

Cohen, J. D.; Finney, M.; McAllister, S.

2015-12-01

Wildfire flame spread results from a sequence of ignitions where adjacent fuel particles heat from radiation and convection leading to their ignition. Surprisingly, after decades of fire behavior research an experimentally based, fundamental understanding of wildland fire spread processes has not been established. Modelers have commonly assumed radiation to be the dominant heating mechanism; that is, radiation heat transfer primarily determines wildland fire spread. We tested this assumption by focusing on how fuel ignition occurs with a renewed emphasis on experimental research. Our experiments show that fuel particle size can non-linearly influence a fuel particle's convective heat transfer. Fine fuels (less than 1 mm) can convectively cool in ambient air such that radiation heating is insufficient for ignition and thus fire spread. Given fire spread with insufficient radiant heating, fuel particle ignition must occur convectively from flame contact. Further experimentation reveals that convective heating and particle ignition occur when buoyancy-induced instabilities and vorticity force flames down and forward to produce intermittent contact with the adjacent fuel bed. Experimental results suggest these intermittent forward flame extensions are buoyancy driven with predictable average frequencies for flame zones ranging from laboratory (10-2 m) to field scales (101m). Measured fuel particle temperatures and boundary conditions during spreading laboratory fires reveal that convection heat transfer from intermittent flame contact is the principal mechanism responsible for heating fine fuel particles to ignition. Our experimental results describe how fine fuel particles convectively heat to ignition from flame contact related to the buoyant dynamics of spreading flame fronts. This research has caused a rethinking of some of the most basic concepts in wildland fuel particle ignition and flame spread.

Momentum and Heat Transfer Models for Detonation in Nitromethane with Metal Particles

NASA Astrophysics Data System (ADS)

Ripley, Robert; Zhang, Fan; Lien, Fue-Sang

2009-06-01

Models for momentum and heat exchange have been derived from the results of previous 3D mesoscale simulations of detonation in packed aluminum particles saturated with nitromethane, where the shock interaction timescale was resolved. In these models, particle acceleration and heating within the shock and detonation zone have been expressed in terms of velocity and temperature transmission factors, which are a function of metal to explosive density ratio, metal volume fraction and ratio of particle size to detonation zone thickness. These models are incorporated as source terms in the governing equations for continuum dense two-phase flow and macroscopic simulation is then applied to detonation of nitromethane/aluminum in lightly-cased cylinders. Heterogeneous detonation features such as velocity deficit, enhanced pressure, and critical diameter effects are reproduced. Various spherical particle diameters from 3 -- 30 μm are utilized where most of the particles react in the expanding detonation products. Results for detonation velocity, pressure history, failure and U-shaped critical diameter behavior are compared to the existing experiments.

Momentum and Heat Transfer Models for Detonation in Nitromethane with Metal Particles

NASA Astrophysics Data System (ADS)

Ripley, R. C.; Zhang, F.; Lien, F.-S.

2009-12-01

Models for momentum and heat exchange have been derived from the results of previous 3D mesoscale simulations of detonation in packed aluminum particles saturated with nitromethane, where the shock interaction timescale was resolved. In these models, particle acceleration and heating within the shock and detonation zone are expressed in terms of velocity and temperature transmission factors, which are a function of the metal to explosive density ratio, solid volume fraction and ratio of particle size to detonation zone thickness. These models are incorporated as source terms in the governing equations for continuum dense two-phase flow, and then applied to macroscopic simulation of detonation of nitromethane/aluminum in lightly-cased cylinders. Heterogeneous detonation features such as velocity deficit, enhanced pressure, and critical diameter effects are demonstrated. Various spherical particle diameters from 3-350 μm are utilized where most of the particles react in the expanding detonation products. Results for detonation velocity, pressure history, failure and U-shaped critical diameter behavior are compared to existing experiments.

The Influence of Static and Rotating Magnetic Fields on Heat and Mass Transfer in Silicon Floating Zones

NASA Technical Reports Server (NTRS)

Croell, Arne; Dold, P.; Kaiser, Th.; Szofran, Frank; Benz, K. W.

1999-01-01

Hear and mass transfer in float-zone processing are strongly influenced by convective flows in the zone. They are caused by buoyancy convection, thermocapillary (Marangoni) convection, or artificial sources such as rotation and radio frequency heating. Flows in conducting melts can be controlled by the use of magnetic fields, either by damping fluid motion with static fields or by generating a def@ned flow with rotating fields. The possibilities of using static and rotating magnetic fields in silicon floating-zone growth have been investigated by experiments in axial static fields up to ST and in transverse rotating magnetic fields up to 7.S mT. Static fields of a few 100 MT already suppress most striations but are detrimental to the radial segregation by introducing a coring effect. A complete suppression of dopant striations caused by time-dependent thermocapillary convection and a reduction of the coring to insignificant values, combined with a shift of the axial segregation profile towards a more diffusion-limited case, is possible with static fields ? 1T. However, under certain conditions the use of high axial magnetic fields can lead to the appearance of a new type of pronounced dopant striations, caused by thermoelec:romagnetic convection. The use of a transverse rotating magnetic field influences the microscopic segregation at quite low inductions, of the order of a few mT. The field shifts time-dependent flows and the resulting striation patterns from a broad range of low frequencies at high amplitudes to a few high frequencies at low amplitudes

Evaluation of Temperature Gradient in Advanced Automated Directional Solidification Furnace (AADSF) by Numerical Simulation

NASA Technical Reports Server (NTRS)

Bune, Andris V.; Gillies, Donald C.; Lehoczky, Sandor L.

1996-01-01

A numerical model of heat transfer using combined conduction, radiation and convection in AADSF was used to evaluate temperature gradients in the vicinity of the crystal/melt interface for variety of hot and cold zone set point temperatures specifically for the growth of mercury cadmium telluride (MCT). Reverse usage of hot and cold zones was simulated to aid the choice of proper orientation of crystal/melt interface regarding residual acceleration vector without actual change of furnace location on board the orbiter. It appears that an additional booster heater will be extremely helpful to ensure desired temperature gradient when hot and cold zones are reversed. Further efforts are required to investigate advantages/disadvantages of symmetrical furnace design (i.e. with similar length of hot and cold zones).

Temperature control and measurement with tunable femtosecond optical tweezers

NASA Astrophysics Data System (ADS)

Mondal, Dipankar; Goswami, Debabrata

2016-09-01

We present the effects of wavelength dependent temperature rise in a femtosecond optical tweezers. Our experiments involve the femtosecond trapping laser tunable from 740-820 nm at low power 25 mW to cause heating in the trapped volume within a homogeneous solution of sub micro-molar concentration of IR dye. The 780 nm high repetition rate laser acts as a resonant excitation source which helps to create the local heating effortlessly within the trapping volume. We have used both position autocorrelation and equipartion theorem to evaluate temperature at different wavelength having different absorption coefficient. Fixing the pulse width in the temporal domain gives constant bandwidth at spatial domain, which makes our system behave as a tunable temperature rise device with high precision. This observation leads us to calculate temperature as well as viscosity within the vicinity of the trapping zone. A mutual energy transfer occurs between the trapped bead and solvents that leads to transfer the thermal energy of solvents into the kinetic energy of the trap bead and vice-versa. Thus hot solvated molecules resulting from resonant and near resonant excitation of trapping wavelength can continuously dissipate heat to the trapped bead which will be reflected on frequency spectrum of Brownian noise exhibited by the bead. Temperature rise near the trapping zone can significantly change the viscosity of the medium. We observe temperature rise profile according to its Gaussian shaped absorption spectrum with different wavelength.

INTERACTION OF LASER RADIATION WITH MATTER: Calculation of the kinetics of heating and structural changes in the cartilaginous tissue under the action of laser radiation

NASA Astrophysics Data System (ADS)

Sobol', E. N.; Kitai, M. S.

1998-07-01

A theoretical model is developed for the calculation of the temperature fields and determination of the size of a zone with structural changes in the cartilaginous tissue. The model is based on a simultaneous analysis of the heat and mass transfer processes and it takes into account the bulk absorption of laser radiation by the tissue, surface evaporation of water, and temperature dependences of the diffusion coefficients. It is assumed that under the influence of a phase transition between free and bound water, caused by heating of the cartilage to 70°C, the proteoglycans of the cartilage matrix become mobile and, as a result of such mass transfer, structural changes are induced in the cartilaginous tissue causing relaxation of stresses or denaturation. It is shown that the maximum temperature is then reached not on the irradiated surface but at some distance from it, and that the size of the zones of structural changes (denaturation depth) depends strongly on the energy density of the laser radiation and its wavelength, on the duration of the irradiation, and on the cartilage thickness. This model makes it possible to calculate the temperature fields and the depth of structural changes in laser-induced relaxation of stresses and changes in the shape of the cartilaginous tissue.

Smouldering (thermal) remediation of soil contaminated with industrial organic liquids: novel insights into heat transfer and kinetics uncovered by integrating experiments and modelling

NASA Astrophysics Data System (ADS)

Gerhard, J.; Zanoni, M. A. B.; Torero, J. L.

2017-12-01

Smouldering (i.e., flameless combustion) underpins the technology Self-sustaining Treatment for Active Remediation (STAR). STAR achieves the in situ destruction of nonaqueous phase liquids (NAPLs) by generating a self-sustained smouldering reaction that propagates through the source zone. This research explores the nature of the travelling reaction and the influence of key in situ and engineered characteristics. A novel one-dimensional numerical model was developed (in COMSOL) to simulate the smouldering remediation of bitumen-contaminated sand. This model was validated against laboratory column experiments. Achieving model validation depended on correctly simulating the energy balance at the reaction front, including properly accounting for heat transfer, smouldering kinetics, and heat losses. Heat transfer between soil and air was demonstrated to be generally not at equilibrium. Moreover, existing heat transfer correlations were found to be inappropriate for the low air flow Reynold's numbers (Re < 30) relevant in this and similar thermal remediation systems. Therefore, a suite of experiments were conducted to generate a new heat transfer correlation, which generated correct simulations of convective heat flow through soil. Moreover, it was found that, for most cases of interest, a simple two-step pyrolysis/oxidation set of kinetic reactions was sufficient. Arrhenius parameters, calculated independently from thermogravimetric experiments, allowed the reaction kinetics to be validated in the smouldering model. Furthermore, a simple heat loss term sufficiently accounted for radial heat losses from the column. Altogether, these advances allow this simple model to reasonably predict the self-sustaining process including the peak reaction temperature, the reaction velocity, and the complete destruction of bitumen behind the front. Simulations with the validated model revealed numerous unique insights, including how the system inherently recycles energy, how air flow rate and NAPL saturation dictate contaminant destruction rates, and the extremes that lead to extinction. Overall, this research provides unique insights into the complex interplay of thermochemical processes that govern the success of smouldering as well as other thermal remediation approaches.

Low temperature heat treatments of AA5754-Ti6Al4V dissimilar laser welds: Microstructure evolution and mechanical properties

NASA Astrophysics Data System (ADS)

Leo, P.; D'Ostuni, S.; Casalino, G.

2018-03-01

This paper presents the effects of the post welding heat treatments (PWHT) performed at 350 °C and 450 °C on the microstructure evolution and mechanical properties of AA5754 and Ti6Al4V dissimilar laser welds. The microstructure and tensile properties of the welds before and after low temperature treatment were analyzed. The off-set welding technique was applied to limit the formation of brittle intermetallic compounds during the welding process. The laser beam was directed onto the titanium side at a small distance from the aluminum edge. The keyhole formed and the full penetration was reached in the titanium side of the weld. Thereafter, the aluminum side melted as the heat that formed the keyhole transferred from the titanium fused zone. Two different energy lines (32 J/mm and 76 J/mm) were used. In this manner, a fused and a heat affected zones was revealed on both sides of the weld. Several intermetallic compounds formed in the intermetallic layer between the two metals. The thickness and the composition of the intermetallic layer depended on the welding parameters and the post welding heat treatment. The hardness and tensile properties of the welds before and after the post welding heat treatment were measured and analyzed.

Magnetohydrodynamic flow and heat transfer around a heated cylinder of arbitrary conductivity

NASA Astrophysics Data System (ADS)

Tassone, A.; Nobili, M.; Caruso, G.

2017-11-01

The interaction of the liquid metal with the plasma confinement magnetic field constitutes a challenge for the design of fusion reactor blankets, due to the arise of MHD effects: increased pressure drops, heat transfer suppression, etc. To overcome these issues, a dielectric fluid can be employed as coolant for the breeding zone. A typical configuration involves pipes transverse to the liquid metal flow direction. This numerical study is conducted to assess the influence of pipe conductivity on the MHD flow and heat transfer. The CFD code ANSYS CFX was employed for this purpose. The fluid is assumed to be bounded by rectangular walls with non-uniform thickness and subject to a skewed magnetic field with the main component aligned with the cylinder axis. The simulations were restricted to Re = (20; 40) and M = (10; 50). Three different scenarios for the obstacle were considered: perfectly insulating, finite conductivity and perfectly conducting. The electrical conductivity was found to affect the channel pressure penalty due to the obstacle insertion only for M = 10 and just for the two limiting cases. A general increment of the heat transfer with M was found due to the tendency of the magnetic field to equalize the flow rate between the sub-channels individuated by the pipe. The best results were obtained with the insulating pipe, due to the reduced electromagnetic drag. The generation of counter-rotating vortices close to the lateral duct walls was observed for M = 50 and perfectly conducting pipe as a result of the modified currents distribution.

Method And Apparatus For Converting Hydrocarbon Fuel Into Hydrogen Gas And Carbon Dioxide

DOEpatents

Clawson, Lawrence G.; Mitchell, William L.; Bentley, Jeffrey M.; Thijssen, Johannes H. J.

2001-03-27

A hydrocarbon fuel reforming method is disclosed suitable for producing synthesis hydrogen gas from reactions with hydrocarbons fuels, oxygen, and steam. A first mixture of an oxygen-containing gas and a first fuel is directed into a first tube 108 to produce a first reaction reformate. A second mixture of steam and a second fuel is directed into a second tube 116 annularly disposed about the first tube 108 to produce a second reaction reformate. The first and second reaction reformates are then directed into a reforming zone 144 and subject to a catalytic reforming reaction. In another aspect of the method, a first fuel is combusted with an oxygen-containing gas in a first zone 108 to produce a reformate stream, while a second fuel under steam reforming in a second zone 116. Heat energy from the first zone 108 is transferred to the second zone 116.

Convective Enhancement of Icing Roughness Elements in Stagnation Region Flows

NASA Technical Reports Server (NTRS)

Hughes, Michael T.; McClain, Stephen T.; Vargas, Mario; Broeren, Andy

2015-01-01

To improve existing ice accretion simulation codes, more data regarding ice roughness and its effects on convective heat transfer are required. To build on existing research on this topic, this study used the Vertical Icing Studies Tunnel (VIST) at NASA Glenn Research to model realistic ice roughness in the stagnation region of a NACA 0012 airfoil. Using the VIST, a test plate representing the leading 2% chord of the airfoil was subjected to flows of 7.62 m/s (25 ft/s), 12.19 m/s (40 ft/s), and 16.76 m/s (55 ft/s). The test plate was fitted with 3 surfaces, each with a different representation of ice roughness: 1) a control surface with no ice roughness, 2) a surface with ice roughness with element height scaled by 10x and streamwise rough zone width from the stagnation point scaled by 10x, and 3) a surface with ice roughness with element height scaled by 10x and streamwise rough zone width from the stagnation point scaled by 25x. Temperature data from the tests were recorded using an infrared camera and thermocouples imbedded in the test plate. From the temperature data, a convective heat transfer coefficient map was created for each case. Additional testing was also performed to validate the VIST's flow quality. These tests included five-hole probe and hot-wire probe velocity traces to provide flow visualization and to study boundary layer formation on the various test surfaces. The knowledge gained during the experiments will help improve ice accretion codes by providing heat transfer coefficient validation data and by providing flow visualization data helping understand current and future experiments performed in the VIST.

Laser treatment of female stress urinary incontinence: optical, thermal, and tissue damage simulations

NASA Astrophysics Data System (ADS)

Hardy, Luke A.; Chang, Chun-Hung; Myers, Erinn M.; Kennelly, Michael J.; Fried, Nathaniel M.

2016-02-01

Treatment of female stress urinary incontinence (SUI) by laser thermal remodeling of subsurface tissues is studied. Light transport, heat transfer, and thermal damage simulations were performed for transvaginal and transurethral methods. Monte Carlo (MC) provided absorbed photon distributions in tissue layers (vaginal wall, endopelvic fascia, urethral wall). Optical properties (n,μa,μs,g) were assigned to each tissue at λ=1064 nm. A 5-mm-diameter laser beam and power of 5 W for 15 s was used, based on previous experiments. MC output was converted into absorbed energy, serving as input for ANSYS finite element heat transfer simulations of tissue temperatures over time. Convective heat transfer was simulated with contact cooling probe set at 0 °C. Thermal properties (κ,c,ρ) were assigned to each tissue layer. MATLAB code was used for Arrhenius integral thermal damage calculations. A temperature matrix was constructed from ANSYS output, and finite sum was incorporated to approximate Arrhenius integral calculations. Tissue damage properties (Ea,A) were used to compute Arrhenius sums. For the transvaginal approach, 37% of energy was absorbed in endopelvic fascia layer with 0.8% deposited beyond it. Peak temperature was 71°C, treatment zone was 0.8-mm-diameter, and almost all of 2.7-mm-thick vaginal wall was preserved. For transurethral approach, 18% energy was absorbed in endopelvic fascia with 0.3% deposited beyond it. Peak temperature was 80°C, treatment zone was 2.0-mm-diameter, and only 0.6 mm of 2.4-mm-thick urethral wall was preserved. A transvaginal approach is more feasible than transurethral approach for laser treatment of SUI.

Operating results of a thermocline thermal energy storage included in a parabolic trough mini power plant

NASA Astrophysics Data System (ADS)

Fasquelle, Thomas; Falcoz, Quentin; Neveu, Pierre; Lecat, Florent; Boullet, Nicolas; Flamant, Gilles

2017-06-01

A thermocline thermal energy storage tank consists in using one single tank to store sensible heat. At almost any time, three zones coexist in the tank: a hot fluid zone at the top, a cold fluid zone at the bottom, and an intermediate zone called thermocline. Filling the tank with solid materials enables to reduce cost and to maintain the thermal stratification during stand-by periods. The present paper deals with a 230 kWh experimental thermocline tank that is included into a 150 kWth parabolic trough mini power plant. The heat transfer fluid is a non-pressurized synthetic oil (dibenzyltoluene) that flows through alumina spheres in the storage tank. The solid materials are contained into baskets in order to facilitate their removing and replacement. Thermocouples measure temperature along the center of the cylinder and along its radius. It is therefore possible to study the thermocline behavior thanks to the measured temperature profiles. A typical charge, a typical discharge and a stand-by process are presented and storage performances are discussed. The behavior of the tank in a dynamic system is also considered, by analyzing a typical day of solar production and storage of the energy surplus.

A Model for coupled heat and moisture transfer in permafrost regions of three rivers source areas, Qinghai, China

NASA Astrophysics Data System (ADS)

Wu, X. L.; Xiang, X. H.; Wang, C. H.; Shao, Q. Q.

2012-04-01

Soil freezing occurs in winter in many parts of the world. The transfer of heat and moisture in freezing and thawing soil is interrelated, and this heat and moisture transport plays an important role in hydrological activity of seasonal frozen region especially for three rivers sources area of China. Soil freezing depth and ice content in frozen zone will significantly influence runoff and groundwater recharge. The purpose of this research is to develop a numerical model to simulate water and heat movement in the soil under freezing and thawing conditions. The basic elements of the model are the heat and water flow equations, which are heat conduction equation and unsaturated soil fluid mass conservation equation. A full-implicit finite volume scheme is used to solve the coupled equations in space. The model is calibrated and verified against the observed moisture and temperature of soil during freezing and thawing period from 2005 to 2007. Different characters of heat and moisture transfer are testified, such as frozen depth, temperature field of 40 cm depth and topsoil moisture content, et al. The model is calibrated and verified against observed value, which indicate that the new model can be used successfully to simulate numerically the coupled heat and mass transfer process in permafrost regions. By simulating the runoff generation process and the driven factors of seasonal changes, the agreement illustrates that the coupled model can be used to describe the local phonemes of hydrologic activities and provide a support to the local Ecosystem services. This research was supported by the National Natural Science Foundation of China (No. 51009045; 40930635; 41001011; 41101018; 51079038), the National Key Program for Developing Basic Science (No. 2009CB421105), the Fundamental Research Funds for the Central Universities (No. 2009B06614; 2010B00414), the National Non Profit Research Program of China (No. 200905013-8; 201101024; 20101224).

Thermo-chemical modelling of a village cookstove for design improvement

NASA Astrophysics Data System (ADS)

Honkalaskar, Vijay H.; Sohoni, Milind; Bhandarkar, Upendra V.

2014-05-01

Cookstove operation comprises three basic processes, namely combustion of firewood, natural air draft due to the buoyancy induced by the temperature difference between the hearth and its surroundings, and heat transfer to the pot, stove body and surrounding atmosphere. Owing to the heterogenous and unsteady burning of solid fuel, there exist nonlinear and dynamic interrelationships among these process parameters. A steady-state analytical model of the cookstove operation is developed for its design improvement by splitting the hearth into three zones to study char combustion, volatile combustion and heat transfer to the pot bottom separately. It comprises a total of seven relations corresponding to a thorough analysis of the three basic processes. A novel method is proposed to model the combustion of wood to mimic the realities closely. Combustion space above the fuel bed is split into 1000 discrete parts to study the combustion of volatiles by considering a set of representative volatile gases. Model results are validated by comparing them with a set of water boiling tests carried on a traditional cookstove in the laboratory. It is found that the major thrust areas to improve the thermal performance are combustion of volatiles and the heat transfer to the pot. It is revealed that the existing design dimensions of the traditional cookstove are close to their optimal values. Addition of twisted-tape inserts in the hearth of the cookstove shows an improvement in the thermal performance due to increase in the heat transfer coefficient to the pot bottom and improved combustion of volatiles.

Final Report: A Transport Phenomena Based Approach to Probe Evolution of Weld Macro and Microstructures and A Smart Bi-directional Model of Fusion Welding

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

Dr. Tarasankar DebRoy

In recent years, applications of numerical heat transfer and fluid flow models of fusion welding have resulted in improved understanding of both the welding processes and welded materials. They have been used to accurately calculate thermal cycles and fusion zone geometry in many cases. Here we report the following three major advancements from this project. First, we show how microstructures, grain size distribution and topology of welds of several important engineering alloys can be computed starting from better understanding of the fusion welding process through numerical heat transfer and fluid flow calculations. Second, we provide a conclusive proof that themore » reliability of numerical heat transfer and fluid flow calculations can be significantly improved by optimizing several uncertain model parameters. Third, we demonstrate how the numerical heat transfer and fluid flow models can be combined with a suitable global optimization program such as a genetic algorithm for the tailoring of weld attributes such as attaining a specified weld geometry or a weld thermal cycle. The results of the project have been published in many papers and a listing of these are included together with a list of the graduate thesis that resulted from this project. The work supported by the DOE award has resulted in several important national and international awards. A listing of these awards and the status of the graduate students are also presented in this report.« less

Numerical simulation of turbulent flow and heat transfer in the wedge-shaped liquid metal pool of a twin-roll caster

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

Seyedein, S.H.; Hasan, H.

1997-03-01

Controlled flow and heat transfer are important for the quality of a strip in a twin-roll continuous casting process. A numerical study was carried out to investigate the two-dimensional turbulent flow and heat transfer in the liquid stainless-steel-filled wedge-shaped cavity formed by the two counterrotating rolls in a twin-roll continuous casting system. The turbulent characteristics of the flow were modeled using a low-Reynolds-number {kappa}-{epsilon} turbulence model due to Launder and Sharma. The arbitrary nature of the computational domain was accounted for through the use of a nonorthogonal boundary-fitted coordinate system on a staggered grid. A control-volume-based finite difference scheme wasmore » used to solve the transformed transport equations. This study is primarily focused on elucidating the inlet superheat dissipation in the melt pool with the rolls being maintained at a constant liquidus temperature of the steel. A parametric study was carried out to ascertain the effect of the inlet superheat, the casting speed, and the roll gap at the nip of the rotating rolls on the flow and heat transfer characteristics. The velocity fields show two counterrotating recirculation zones in the upstream region. The local Nusselt number on the roll surface shows significant variations. The contours of temperature and turbulent viscosity show the complex nature of the turbulent transport phenomena to be expected in a twin-roll casting process.« less

Computational model of miniature pulsating heat pipes

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

Martinez, Mario J.; Givler, Richard C.

The modeling work described herein represents Sandia National Laboratories (SNL) portion of a collaborative three-year project with Northrop Grumman Electronic Systems (NGES) and the University of Missouri to develop an advanced, thermal ground-plane (TGP), which is a device, of planar configuration, that delivers heat from a source to an ambient environment with high efficiency. Work at all three institutions was funded by DARPA/MTO; Sandia was funded under DARPA/MTO project number 015070924. This is the final report on this project for SNL. This report presents a numerical model of a pulsating heat pipe, a device employing a two phase (liquid andmore » its vapor) working fluid confined in a closed loop channel etched/milled into a serpentine configuration in a solid metal plate. The device delivers heat from an evaporator (hot zone) to a condenser (cold zone). This new model includes key physical processes important to the operation of flat plate pulsating heat pipes (e.g. dynamic bubble nucleation, evaporation and condensation), together with conjugate heat transfer with the solid portion of the device. The model qualitatively and quantitatively predicts performance characteristics and metrics, which was demonstrated by favorable comparisons with experimental results on similar configurations. Application of the model also corroborated many previous performance observations with respect to key parameters such as heat load, fill ratio and orientation.« less

Three phase heat and mass transfer model for unsaturated soil freezing process: Part 1 - model development

NASA Astrophysics Data System (ADS)

Xu, Fei; Zhang, Yaning; Jin, Guangri; Li, Bingxi; Kim, Yong-Song; Xie, Gongnan; Fu, Zhongbin

2018-04-01

A three-phase model capable of predicting the heat transfer and moisture migration for soil freezing process was developed based on the Shen-Chen model and the mechanisms of heat and mass transfer in unsaturated soil freezing. The pre-melted film was taken into consideration, and the relationship between film thickness and soil temperature was used to calculate the liquid water fraction in both frozen zone and freezing fringe. The force that causes the moisture migration was calculated by the sum of several interactive forces and the suction in the pre-melted film was regarded as an interactive force between ice and water. Two kinds of resistance were regarded as a kind of body force related to the water films between the ice grains and soil grains, and a block force instead of gravity was introduced to keep balance with gravity before soil freezing. Lattice Boltzmann method was used in the simulation, and the input variables for the simulation included the size of computational domain, obstacle fraction, liquid water fraction, air fraction and soil porosity. The model is capable of predicting the water content distribution along soil depth and variations in water content and temperature during soil freezing process.

The Lassen hydrothermal system

USGS Publications Warehouse

Ingebritsen, Steven E.; Bergfeld, Deborah; Clor, Laura; Evans, William C.

2016-01-01

The active Lassen hydrothermal system includes a central vapor-dominated zone or zones beneath the Lassen highlands underlain by ~240 °C high-chloride waters that discharge at lower elevations. It is the best-exposed and largest hydrothermal system in the Cascade Range, discharging 41 ± 10 kg/s of steam (~115 MW) and 23 ± 2 kg/s of high-chloride waters (~27 MW). The Lassen system accounts for a full 1/3 of the total high-temperature hydrothermal heat discharge in the U.S. Cascades (140/400 MW). Hydrothermal heat discharge of ~140 MW can be supported by crystallization and cooling of silicic magma at a rate of ~2400 km3/Ma, and the ongoing rates of heat and magmatic CO2 discharge are broadly consistent with a petrologic model for basalt-driven magmatic evolution. The clustering of observed seismicity at ~4–5 km depth may define zones of thermal cracking where the hydrothermal system mines heat from near-plastic rock. If so, the combined areal extent of the primary heat-transfer zones is ~5 km2, the average conductive heat flux over that area is >25 W/m2, and the conductive-boundary length <50 m. Observational records of hydrothermal discharge are likely too short to document long-term transients, whether they are intrinsic to the system or owe to various geologic events such as the eruption of Lassen Peak at 27 ka, deglaciation beginning ~18 ka, the eruptions of Chaos Crags at 1.1 ka, or the minor 1914–1917 eruption at the summit of Lassen Peak. However, there is a rich record of intermittent hydrothermal measurement over the past several decades and more-frequent measurement 2009–present. These data reveal sensitivity to climate and weather conditions, seasonal variability that owes to interaction with the shallow hydrologic system, and a transient 1.5- to twofold increase in high-chloride discharge in response to an earthquake swarm in mid-November 2014.

Flow-dependent vascular heat transfer during microwave thermal ablation.

PubMed

Chiang, Jason; Hynes, Kieran; Brace, Christopher L

2012-01-01

Microwave tumor ablation is an attractive option for thermal ablation because of its inherent benefits over radiofrequency ablation (RFA) in the treatment of solid tumors such as hepatocellular carcinoma (HCC). Microwave energy heats tissue to higher temperatures and at a faster rate than RFA, creating larger, more homogenous ablation zones. In this study, we investigate microwave heating near large vasculature using coupled fluid-flow and thermal analysis. Low-flow conditions are predicted to be more likely to cause cytotoxic heating and, therefore, vessel thrombosis and endothelial damage of downstream tissues. Such conditions may be more prevalent in patient with severe cirrhosis or compromised blood flow. High-flow conditions create the more familiar heat-sink effect that can protect perivascular tissues from the intended thermal damage. These results may help guide placement and use of microwave ablation technologies in future studies.

Using laser radiation for the formation of capillary structure in flat ceramic heat pipes

NASA Astrophysics Data System (ADS)

Nikolaenko, Yu. E.; Rotner, S. M.

2012-12-01

The possibility of using laser radiation with a wavelength of 1.064 μm for the formation of a capillary structure in the evaporation zone of flat ceramic heat pipes has been experimentally confirmed. Using a technological regime with established parameters, a capillary structure was formed in AlN and Al2O3 ceramic plates with a thickness of 1-2 mm and lateral dimensions of 48 × 60 and 100 × 100 mm, which ensured absorption of heat-transfer fluids (distilled water, ethyl alcohol, acetone) to a height of 100 mm against gravity forces. The thermal resistance of flat ceramic heat pipes with this capillary structure reaches 0.07°C/W, which is quite acceptable for their use as heat sinks in systems of thermal regime control for electronic components and as heat exchange plates for large-size thermoelectric conversion units.

A review and analysis of boundary layer transition data for turbine application

NASA Technical Reports Server (NTRS)

Gaugler, R. E.

1984-01-01

A symposium on transition in turbines was held at the NASA Lewis Research Center. One recommendation of the working groups was the collection of existing transition data to provide standard cases against which models could be tested. A number of data sets from the open literature that include heat transfer data in apparently transitional boundary layers, with particular application to the turbine environment, were reviewed and analyzed to extract transition information from the heat transfer data. The data sets reviewed cover a wide range of flow conditions, from low speed, flat plate tests to full scale turbine airfoils operating at simulated turbine engine conditions. The results indicate that free stream turbulence and pressure gradient have strong, and opposite, effects on the location of the start of transition and on the length of the transition zone.

A review and analysis of boundary layer transition data for turbine application

NASA Technical Reports Server (NTRS)

Gaugler, R. E.

1985-01-01

A symposium on transition in turbines was held at the NASA Lewis Research Center. One recommendation of the working groups was the collection of existing transition data to provide standard cases against which models could be tested. A number of data sets from the open literature that include heat transfer data in apparently transitional boundary layers, with particular application to the turbine environment, were reviewed and analyzed to extract transition information from the heat transfer data. The data sets reviewed cover a wide range of flow conditions, from low speed, flat plate tests to full scale turbine airfoils operating at simulated turbine engine conditions. The results indicate that free stream turbulence and pressure gradient have strong, and opposite, effects on the location of the start of transition and on the length of the transition zone.

A Sequential Fluid-mechanic Chemical-kinetic Model of Propane HCCI Combustion

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

Aceves, S M; Flowers, D L; Martinez-Frias, J

2000-11-29

We have developed a methodology for predicting combustion and emissions in a Homogeneous Charge Compression Ignition (HCCI) Engine. This methodology combines a detailed fluid mechanics code with a detailed chemical kinetics code. Instead of directly linking the two codes, which would require an extremely long computational time, the methodology consists of first running the fluid mechanics code to obtain temperature profiles as a function of time. These temperature profiles are then used as input to a multi-zone chemical kinetics code. The advantage of this procedure is that a small number of zones (10) is enough to obtain accurate results. Thismore » procedure achieves the benefits of linking the fluid mechanics and the chemical kinetics codes with a great reduction in the computational effort, to a level that can be handled with current computers. The success of this procedure is in large part a consequence of the fact that for much of the compression stroke the chemistry is inactive and thus has little influence on fluid mechanics and heat transfer. Then, when chemistry is active, combustion is rather sudden, leaving little time for interaction between chemistry and fluid mixing and heat transfer. This sequential methodology has been capable of explaining the main characteristics of HCCI combustion that have been observed in experiments. In this paper, we use our model to explore an HCCI engine running on propane. The paper compares experimental and numerical pressure traces, heat release rates, and hydrocarbon and carbon monoxide emissions. The results show an excellent agreement, even in parameters that are difficult to predict, such as chemical heat release rates. Carbon monoxide emissions are reasonably well predicted, even though it is intrinsically difficult to make good predictions of CO emissions in HCCI engines. The paper includes a sensitivity study on the effect of the heat transfer correlation on the results of the analysis. Importantly, the paper also shows a numerical study on how parameters such as swirl rate, crevices and ceramic walls could help in reducing HC and CO emissions from HCCI engines.« less

Energy Savings of Low-E Storm Windows and Panels across US Climate Zones

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

Culp, Thomas D.; Cort, Katherine A.

This report builds off of previous modeling work related to low-e storm windows used to create a "Database of U.S. Climate-Based Analysis for Low-E Storm Windows." This work updates similar studies using new fuel costs and examining the separate contributions of reduced air leakage and reduced coefficients of overall heat transfer and solar heat gain. In this report we examine the energy savings and cost effectiveness of low-E storm windows in residential homes across a broad range of U.S. climates, excluding the impact from infiltration reductions, which tend to vary using the National Energy Audit Tool (NEAT) and RESFEN modelmore » calculations. This report includes a summary of the results, NEAT and RESFEN background, methodology, and input assumptions, and an appendix with detailed results and assumptions by climate zone.« less

Stress loading from viscous flow in the lower crust and triggering of aftershocks following the 1994 Northridge, California, earthquake

USGS Publications Warehouse

Deng, J.; Hudnut, K.; Gurnis, M.; Hauksson, E.

1999-01-01

Following the M(w) 6.7 Northridge earthquake, significant postseismic displacements were resolved with GPS. Using a three-dimensional viscoelastic model, we suggest that this deformation is mainly driven by viscous flow in the lower crust. Such flow can transfer stress to the upper crust and load the rupture zone of the main shock at a decaying rate. Most aftershocks within the rupture zone, especially those that occurred after the first several weeks of the main shock, may have been triggered by continuous stress loading from viscous flow. The long-term decay time of aftershocks (about 2 years) approximately matches the decay of viscoelastic loading, and thus is controlled by the viscosity of the lower crust. Our model provides a physical interpretation of the observed correlation between aftershock decay rate and surface heat flow.Following the Mw 6.7 Northridge earthquake, significant postseismic displacements were resolved with GPS. Using a three-dimensional viscoelastic model, we suggest that this deformation is mainly driven by viscous flow in the lower crust. Such flow can transfer stress to the upper crust and load the rupture zone of the main shock at a decaying rate. Most aftershocks within the rupture zone, especially those that occurred after the first several weeks of the main shock, may have been triggered by continuous stress loading from viscous flow. The long-term decay time of aftershocks (about 2 years) approximately matches the decay of viscoelastic loading, and thus is controlled by the viscosity of the lower crust. Our model provides a physical interpretation of the observed correlation between aftershock decay rate and surface heat flow.

Energy saving potential of a two-pipe system for simultaneous heating and cooling of office buildings

DOE PAGES

Maccarini, Alessandro; Wetter, Michael; Afshari, Alireza; ...

2016-10-31

This paper analyzes the performance of a novel two-pipe system that operates one water loop to simultaneously provide space heating and cooling with a water supply temperature of around 22 °C. To analyze the energy performance of the system, a simulation-based research was conducted. The two-pipe system was modelled using the equation-based Modelica modeling language in Dymola. A typical office building model was considered as the case study. Simulations were run for two construction sets of the building envelope and two conditions related to inter-zone air flows. To calculate energy savings, a conventional four-pipe system was modelled and used formore » comparison. The conventional system presented two separated water loops for heating and cooling with supply temperatures of 45 °C and 14 °C, respectively. Simulation results showed that the two-pipe system was able to use less energy than the four-pipe system thanks to three effects: useful heat transfer from warm to cold zones, higher free cooling potential and higher efficiency of the heat pump. In particular, the two-pipe system used approximately between 12% and 18% less total annual primary energy than the four-pipe system, depending on the simulation case considered.« less

A dual-mode textile for human body radiative heating and cooling

DOE PAGES

Hsu, Po -Chun; Liu, Chong; Song, Alex Y.; ...

2017-11-10

Maintaining human body temperature is one of the most basic needs for living, which often consumes a huge amount of energy to keep the ambient temperature constant. To expand the ambient temperature range while maintaining human thermal comfort, the concept of personal thermal management has been recently demonstrated in heating and cooling textiles separately through human body infrared radiation control. Realizing these two opposite functions within the same textile would represent an exciting scientific challenge and a significant technological advancement. We demonstrate a dual-mode textile that can perform both passive radiative heating and cooling using the same piece of textilemore » without any energy input. The dual-mode textile is composed of a bilayer emitter embedded inside an infrared-transparent nanoporous polyethylene (nanoPE) layer. We demonstrate that the asymmetrical characteristics of both emissivity and nanoPE thickness can result in two different heat transfer coefficients and achieve heating when the low-emissivity layer is facing outside and cooling by wearing the textile inside out when the high-emissivity layer is facing outside. This can expand the thermal comfort zone by 6.5°C. As a result, numerical fitting of the data further predicts 14.7°C of comfort zone expansion for dual-mode textiles with large emissivity contrast.« less

Energy saving potential of a two-pipe system for simultaneous heating and cooling of office buildings

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

Maccarini, Alessandro; Wetter, Michael; Afshari, Alireza

This paper analyzes the performance of a novel two-pipe system that operates one water loop to simultaneously provide space heating and cooling with a water supply temperature of around 22 °C. To analyze the energy performance of the system, a simulation-based research was conducted. The two-pipe system was modelled using the equation-based Modelica modeling language in Dymola. A typical office building model was considered as the case study. Simulations were run for two construction sets of the building envelope and two conditions related to inter-zone air flows. To calculate energy savings, a conventional four-pipe system was modelled and used formore » comparison. The conventional system presented two separated water loops for heating and cooling with supply temperatures of 45 °C and 14 °C, respectively. Simulation results showed that the two-pipe system was able to use less energy than the four-pipe system thanks to three effects: useful heat transfer from warm to cold zones, higher free cooling potential and higher efficiency of the heat pump. In particular, the two-pipe system used approximately between 12% and 18% less total annual primary energy than the four-pipe system, depending on the simulation case considered.« less

A dual-mode textile for human body radiative heating and cooling

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

Hsu, Po -Chun; Liu, Chong; Song, Alex Y.

Maintaining human body temperature is one of the most basic needs for living, which often consumes a huge amount of energy to keep the ambient temperature constant. To expand the ambient temperature range while maintaining human thermal comfort, the concept of personal thermal management has been recently demonstrated in heating and cooling textiles separately through human body infrared radiation control. Realizing these two opposite functions within the same textile would represent an exciting scientific challenge and a significant technological advancement. We demonstrate a dual-mode textile that can perform both passive radiative heating and cooling using the same piece of textilemore » without any energy input. The dual-mode textile is composed of a bilayer emitter embedded inside an infrared-transparent nanoporous polyethylene (nanoPE) layer. We demonstrate that the asymmetrical characteristics of both emissivity and nanoPE thickness can result in two different heat transfer coefficients and achieve heating when the low-emissivity layer is facing outside and cooling by wearing the textile inside out when the high-emissivity layer is facing outside. This can expand the thermal comfort zone by 6.5°C. As a result, numerical fitting of the data further predicts 14.7°C of comfort zone expansion for dual-mode textiles with large emissivity contrast.« less

A dual-mode textile for human body radiative heating and cooling

PubMed Central

Hsu, Po-Chun; Liu, Chong; Song, Alex Y.; Zhang, Ze; Peng, Yucan; Xie, Jin; Liu, Kai; Wu, Chun-Lan; Catrysse, Peter B.; Cai, Lili; Zhai, Shang; Majumdar, Arun; Fan, Shanhui; Cui, Yi

2017-01-01

Maintaining human body temperature is one of the most basic needs for living, which often consumes a huge amount of energy to keep the ambient temperature constant. To expand the ambient temperature range while maintaining human thermal comfort, the concept of personal thermal management has been recently demonstrated in heating and cooling textiles separately through human body infrared radiation control. Realizing these two opposite functions within the same textile would represent an exciting scientific challenge and a significant technological advancement. We demonstrate a dual-mode textile that can perform both passive radiative heating and cooling using the same piece of textile without any energy input. The dual-mode textile is composed of a bilayer emitter embedded inside an infrared-transparent nanoporous polyethylene (nanoPE) layer. We demonstrate that the asymmetrical characteristics of both emissivity and nanoPE thickness can result in two different heat transfer coefficients and achieve heating when the low-emissivity layer is facing outside and cooling by wearing the textile inside out when the high-emissivity layer is facing outside. This can expand the thermal comfort zone by 6.5°C. Numerical fitting of the data further predicts 14.7°C of comfort zone expansion for dual-mode textiles with large emissivity contrast. PMID:29296678

Heat Transfer Through Turbulent Friction Layers

NASA Technical Reports Server (NTRS)

Reichardt, H.

1943-01-01

The "general Prandtl number" Pr(exp 1) - A(sub q)/A Pr, aside from the Reynolds number determines the ratio of turbulent to molecular heat transfer, and the temperature distribution in turbulent friction layers. A(sub q) = exchange coefficient for heat; A = exchange coefficient for momentum transfer. A formula is derived from the equation defining the general Prandtl number which describes the temperature as a function of the velocity. For fully developed thermal boundary layers all questions relating to heat transfer to and from incompressible fluids can be treated in a simple manner if the ratio of the turbulent shear stress to the total stress T(sub t)/T in the layers near the wall is known, and if the A(sub q)/A can be regarded as independent of the distance from the wall. The velocity distribution across a flat smooth channel and deep into the laminar sublayer was measured for isothermal flow to establish the shear stress ratio T(sub t)/T and to extend the universal wall friction law. The values of T(sub t)/T which resulted from these measurements can be approximately represented by a linear function of the velocity in the laminar-turbulent transition zone. The effect of the temperature relationship of the material values on the flow near the wall is briefly analyzed. It was found that the velocity at the laminar boundary (in contrast to the thickness of the laminar layer) is approximately independent of the temperature distribution. The temperature gradient at the wall and the distribution of temperature and heat flow in the turbulent friction layers were calculated on the basis of the data under two equations. The derived formulas and the figures reveal the effects of the Prandtl number, the Reynolds number, the exchange quantities and the temperature relationship of the material values.

Single Step Laser Transfer and Laser Curing of Ag NanoWires: A Digital Process for the Fabrication of Flexible and Transparent Microelectrodes.

PubMed

Zacharatos, Filimon; Karvounis, Panagiotis; Theodorakos, Ioannis; Hatziapostolou, Antonios; Zergioti, Ioanna

2018-06-19

Ag nanowire (NW) networks have exquisite optical and electrical properties which make them ideal candidate materials for flexible transparent conductive electrodes. Despite the compatibility of Ag NW networks with laser processing, few demonstrations of laser fabricated Ag NW based components currently exist. In this work, we report on a novel single step laser transferring and laser curing process of micrometer sized pixels of Ag NW networks on flexible substrates. This process relies on the selective laser heating of the Ag NWs induced by the laser pulse energy and the subsequent localized melting of the polymeric substrate. We demonstrate that a single laser pulse can induce both transfer and curing of the Ag NW network. The feasibility of the process is confirmed experimentally and validated by Finite Element Analysis simulations, which indicate that selective heating is carried out within a submicron-sized heat affected zone. The resulting structures can be utilized as fully functional flexible transparent electrodes with figures of merit even higher than 100. Low sheet resistance (<50 Ohm/sq) and high visible light transparency (>90%) make the reported process highly desirable for a variety of applications, including selective heating or annealing of nanocomposite materials and laser processing of nanostructured materials on a large variety of optically transparent substrates, such as Polydimethylsiloxane (PDMS).

Active chimney effect using heated porous layers: optimum heat transfer

NASA Astrophysics Data System (ADS)

Mehiris, Abdelhak; Ameziani, Djamel-Edine; Rahli, Omar; Bouhadef, Khadija; Bennacer, Rachid

2017-05-01

The purpose of the present work is to treat numerically the problem of the steady mixed convection that occurs in a vertical cylinder, opened at both ends and filled with a succession of three fluid saturated porous elements, namely a partially porous duct. The flow conditions fit with the classical Darcy-Brinkman model allowing analysing the flow structure on the overall domain. The induced heat transfer, in terms of local and average Nusselt numbers, is discussed for various controlling parameters as the porous medium permeability, Rayleigh and Reynolds numbers. The efficiency of the considered system is improved by the injection/suction on the porous matrices frontier. The undertaken numerical exploration particularly highlighted two possible types of flows, with and without fluid recirculation, which principally depend on the mixed convection regime. Thus, it is especially shown that recirculation zones appear in some domain areas under specific conditions, obvious by a negative central velocity and a prevalence of the natural convection effects, i.e., turnoff flow swirls. These latter are more accentuated in the areas close to the porous obstacles and for weak permeability. Furthermore, when fluid injection or suction is considered, the heat transfer increases under suction and reduces under injection. Contribution to the topical issue "Materials for Energy Harvesting, Conversion and Storage II (ICOME 2016)", edited by Jean-Michel Nunzi, Rachid Bennacer and Mohammed El Ganaoui

19 CFR 146.70 - Transfer of zone-restricted merchandise into Customs territory.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 19 Customs Duties 2 2010-04-01 2010-04-01 false Transfer of zone-restricted merchandise into... HOMELAND SECURITY; DEPARTMENT OF THE TREASURY (CONTINUED) FOREIGN TRADE ZONES Transfer of Merchandise From a Zone § 146.70 Transfer of zone-restricted merchandise into Customs territory. (a) General. Zone...

19 CFR 146.70 - Transfer of zone-restricted merchandise into Customs territory.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 19 Customs Duties 2 2014-04-01 2014-04-01 false Transfer of zone-restricted merchandise into... HOMELAND SECURITY; DEPARTMENT OF THE TREASURY (CONTINUED) FOREIGN TRADE ZONES Transfer of Merchandise From a Zone § 146.70 Transfer of zone-restricted merchandise into Customs territory. (a) General. Zone...

19 CFR 146.70 - Transfer of zone-restricted merchandise into Customs territory.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 19 Customs Duties 2 2013-04-01 2013-04-01 false Transfer of zone-restricted merchandise into... HOMELAND SECURITY; DEPARTMENT OF THE TREASURY (CONTINUED) FOREIGN TRADE ZONES Transfer of Merchandise From a Zone § 146.70 Transfer of zone-restricted merchandise into Customs territory. (a) General. Zone...

19 CFR 146.70 - Transfer of zone-restricted merchandise into Customs territory.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 19 Customs Duties 2 2011-04-01 2011-04-01 false Transfer of zone-restricted merchandise into... HOMELAND SECURITY; DEPARTMENT OF THE TREASURY (CONTINUED) FOREIGN TRADE ZONES Transfer of Merchandise From a Zone § 146.70 Transfer of zone-restricted merchandise into Customs territory. (a) General. Zone...

19 CFR 146.70 - Transfer of zone-restricted merchandise into Customs territory.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 19 Customs Duties 2 2012-04-01 2012-04-01 false Transfer of zone-restricted merchandise into... HOMELAND SECURITY; DEPARTMENT OF THE TREASURY (CONTINUED) FOREIGN TRADE ZONES Transfer of Merchandise From a Zone § 146.70 Transfer of zone-restricted merchandise into Customs territory. (a) General. Zone...

Static Magnetic Fields in Semiconductor Floating-Zone Growth

NASA Technical Reports Server (NTRS)

Croll, Arne; Benz, K. W.

1999-01-01

Heat and mass transfer in semiconductor float-zone processing are strongly influenced by convective flows in the zone, originating from sources such as buoyancy convection, thermocapillary (Marangoni) convection, differential rotation, or radio frequency heating. Because semiconductor melts are conducting, flows can be damped by the use of static magnetic fields to influence the interface shape and the segregation of dopants and impurities. An important objective is often the suppression of time-dependent flows and the ensuing dopant striations. In RF-heated Si-FZ - crystals, fields up to O.STesla show some flattening of the interface curvature and a reduction of striation amplitudes. In radiation-heated (small-scale) SI-FZ crystals, fields of 0.2 - 0.5 Tesla already suppress the majority of the dopant striations. The uniformity of the radial segregation is often compromised by using a magnetic field, due to the directional nature of the damping. Transverse fields lead to an asymmetric interface shape and thus require crystal rotation (resulting in rotational dopant striations) to achieve a radially symmetric interface, whereas axial fields introduce a coring effect. A complete suppression of dopant striations and a reduction of the coring to insignificant values, combined with a shift of the axial segregation profile towards a more diffusion-limited case, are possible with axial static fields in excess of 1 Tesla. Strong static magnetic fields, however, can also lead to the appearance of thermoelectromagnetic convection, caused by the interaction of thermoelectric currents with the magnetic field.

Current COIL research in Samara

NASA Astrophysics Data System (ADS)

Nikolaev, Valeri D.

1996-02-01

Development of the high pressure singlet oxygen generator (SOG) is a very important aspect for chemical oxygen-iodine laser (COIL). Increasing of oxygen pressure up to 30 torr and more at conserving high O2(1(Delta) ) yield and maintaining BHP temperature at minus (10 divided by 20) degrees Celsius permits us to decrease ration [H2O]/[O2] to 5% and less. In this case COIL can operate successfully without a water vapor trap. With raising the total pressure Reynolds number increases too, diminishing boundary layers in supersonic nozzles and improving pressure recovery. The weight and dimensions of the SOG and laser become reduced for the same gas flow rate. For solving these problems the jet SOG has been suggested and developed in Lebedev Physical Institute, Samara Branch. The advantages of the jet SOG consist of the following: (1) Large and controlled specific surface of contact liquid-gas provides for high mass transfer efficiency. (2) High jets velocity guarantees fast basic hydrogen peroxide (BHP) surface renovation. (3) High gas velocity in the reaction zone diminishes O2(1(Delta) ) quenching. (4) Efficient gas-liquid heat exchange eliminates the gas heating and generation water vapor due O2(1(Delta) ) quenching. (5) Counterflowing design of the jet SOG produces the best conditions for self-cleaning gas flow of droplets in the reaction zone and gives the possibility of COIL operation without droplets separator. High pressure jet SOG has some features connected with intrachannel jet formation, free space jets reconstruction, interaction jets ensemble with counter moving gas flow and drag part of gas by jets, disintegrating jets, generation and separation of droplets, heat effects, surface renovation, impoverishment BHP surface by HO2- ions, moving solution film on the reaction zone walls, etc. In this communication our current understanding of the major processes in the jet SOG is set forth. The complex gas and hydrodynamic processes with heat and mass transfer, chemical reactions, generation of the relaxing components with high energy store take place in the SOG reaction zone. It is impossible to create a sufficiently exact model of such a jet SOG taking into account all the enumerated processes. But some approximations and simplifications allow us to determine what the main jet SOG parameters parts are for designing COIL.

Transparent multi-zone crystal growth furnace and method for controlling the same

NASA Technical Reports Server (NTRS)

Batur, Celal (Inventor); Bennett, Robert J. (Inventor); Duval, Walter (Inventor)

2000-01-01

A crystal growth system, comprising: a furnace; a plurality of heating elements coupled to said furnace, each said plurality of heating elements defining a heat zone, each said heating element set to a desired temperature value; a plurality of thermocouples associated with respective heat zones to detect a temperature value; a translation system for passing an ampoule containing crystal growth material through said furnace into said heat zones and providing a positional location of said ampoule and; a multi-variable self-tuning temperature controller connected to said plurality of heating elements, said plurality of thermocouples and said translation system, said controller monitoring each said zone temperature value and upon considering the thermal interaction of heating zones and the moving thermal inertia of the ampoule, adjusting voltage input to said heat zones to obtain optimal crystal growth within said ampoule.

Transparent multi-zone crystal growth furnace and method for controlling the same

NASA Technical Reports Server (NTRS)

Batur, Celal (Inventor); Duval, Walter (Inventor); Bennett, Robert J. (Inventor)

2001-01-01

A crystal growth system, comprising: a furnace; a plurality of heating elements coupled to said furnace, each said plurality of heating elements defining a heat zone, each said heating element set to a desired temperature value; a plurality of thermocouples associated with respective heat zones to detect a temperature value; a translation system for passing an ampoule containing crystal growth material through said furnace into said heat zones and providing a positional location of said ampoule and; a multi-variable self-tuning temperature controller connected to said plurality of heating elements, said plurality of thermocouples and said translation system, said controller monitoring each said zone temperature value and upon considering the thermal interaction of heating zones and the moving thermal inertia of the ampoule, adjusting voltage input to said heat zones to obtain optimal crystal growth within said ampoule.

An open-loop ground-water heat pump system: transient numerical modeling and site experimental results

NASA Astrophysics Data System (ADS)

Lo Russo, S.; Taddia, G.; Gnavi, L.

2012-04-01

KEY WORDS: Open-loop ground water heat pump; Feflow; Low-enthalpy; Thermal Affected Zone; Turin; Italy The increasing diffusion of low-enthalpy geothermal open-loop Groundwater Heat Pumps (GWHP) providing buildings air conditioning requires a careful assessment of the overall effects on groundwater system, especially in the urban areas where several plants can be close together and interfere. One of the fundamental aspects in the realization of an open loop low-enthalpy geothermal system is therefore the capacity to forecast the effects of thermal alteration produced in the ground, induced by the geothermal system itself. The impact on the groundwater temperature in the surrounding area of the re-injection well (Thermal Affected Zone - TAZ) is directly linked to the aquifer properties. The transient dynamic of groundwater discharge and temperature variations should be also considered to assess the subsurface environmental effects of the plant. The experimental groundwater heat pump system used in this study is installed at the "Politecnico di Torino" (NW Italy, Piedmont Region). This plant provides summer cooling needs for the university buildings. This system is composed by a pumping well, a downgradient injection well and a control piezometer. The system is constantly monitored by multiparameter probes measuring the dynamic of groundwater temperature. A finite element subsurface flow and transport simulator (FEFLOW) was used to investigate the thermal aquifer alteration. Simulations were continuously performed during May-October 2010 (cooling period). The numerical simulation of the heat transport in the aquifer was solved with transient conditions. The simulation was performed by considering only the heat transfer within the saturated aquifer, without any heat dispersion above or below the saturated zone due to the lack of detailed information regarding the unsaturated zone. Model results were compared with experimental temperature data derived from groundwater monitoring in the surrounding area of the injection well. Such analysis showed that the measured values differ slightly from the simulated values. That small difference is probably due to the simplification assumptions in the modelling. This hypothesis is still under investigation.

Performance evaluation of an evaporative pad greenhouse system for utilization of power plant reject heat

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

Olszewski, M.; Trezek, G.J.

1976-01-01

The overall performance of an evaporative pad greenhouse is considered in terms of the pad heat and mass transfer, the energy budget of the vegetation, and the performance of the power plant. An analytical predictive model for the pad performance was developed utilizing the Merkel total heat approximation. Data obtained from actual greenhouse performance provides an experimental verification of the pad model. Energy balance considerations on the vegetation provide a means of viewing optimal plant growth in terms of the power plant energy dissipation. In general, the results indicate that when an evaporative pad greenhouse system is used for wastemore » heat dispersal, the vegetation can be maintained within its thermal requirement zone, crop irrigation requirements are significantly reduced, and the power plant performance is comparable with conventional closed loop heat rejection systems.« less

Detonation Velocity Calculations of Explosives with Slowly-Burning Constituents

NASA Astrophysics Data System (ADS)

Howard, W. Michael; Souers, P. Clark; Fried, Laurence E.

1997-07-01

The thermochemical code Equilbrium CHEETAH has been modified to allow partial reaction of constituents and partial flow of heat. Solid or liquid reactants are described by Einstein oscillators, whose temperatures can be changed to allow heat transfer. Hydroxy-terminated-poly-budadiene, mixed with RDX or HMX, does not react, as shown by the effect on the calculated detonation velocity. Aluminum and ammonium perchlorate in composites also do not react. Only partial heat flow also takes place in the unreacted materials. These results show that the usual assumption of total burn in a thermochemical code is probably incorrect, at least in the sonic reaction zone that drives the detonation velocity. A kinetic code would be the logical extension of this work.

System and method for making metallic iron with reduced CO.sub.2 emissions

DOEpatents

Kiesel, Richard F; Englund, David J; Schlichting, Mark; Meehan, John; Crouch, Jeremiah; Wilson, Logan

2014-10-14

A method and system for making metallic iron nodules with reduced CO.sub.2 emissions is disclosed. The method includes: assembling a linear hearth furnace having entry and exit portions, at least a conversion zone and a fusion zone, and a moving hearth adapted to move reducible iron bearing material through the furnace on contiguous hearth sections; assembling a shrouded return substantially free of air ingress extending adjacent at least the conversion and fusion zones of the furnace through which hearth sections can move from adjacent the exit portion to adjacent the entry portion of the furnace; transferring the hearth sections from the furnace to the shrouded return adjacent the exit portion; reducing reducible material in the linear hearth furnace to metallic iron nodules; and transporting gases from at least the fusion zone to the shrouded return to heat the hearth sections while in the shrouded return.

Model of large pool fires.

PubMed

Fay, J A

2006-08-21

A two zone entrainment model of pool fires is proposed to depict the fluid flow and flame properties of the fire. Consisting of combustion and plume zones, it provides a consistent scheme for developing non-dimensional scaling parameters for correlating and extrapolating pool fire visible flame length, flame tilt, surface emissive power, and fuel evaporation rate. The model is extended to include grey gas thermal radiation from soot particles in the flame zone, accounting for emission and absorption in both optically thin and thick regions. A model of convective heat transfer from the combustion zone to the liquid fuel pool, and from a water substrate to cryogenic fuel pools spreading on water, provides evaporation rates for both adiabatic and non-adiabatic fires. The model is tested against field measurements of large scale pool fires, principally of LNG, and is generally in agreement with experimental values of all variables.

Numerical solutions of pulsating flow and heat transfer characteristics in a channel with a backward-facing step

NASA Astrophysics Data System (ADS)

Valencia, A.; Hinojosa, L.

The incompressible laminar flow of air and heat transfer in a channel with a backward-facing step is studied for steady cases and for pulsatile inlet conditions. For steady flows the influence of the inlet velocity profile, the height of the step and the Reynolds number on the reattachment length is investigated. A parabolic entrance profile was used for pulsatile flow. It was found with amplitude of oscillation of one by Re=100 that the primary vortex breakdown through one pulsatile cycle. The wall shear rate in the separation zone varied markedly with pulsatile flows and the wall heat transfer remained relatively constant. The time-average pulsatile heat transfer at the walls was greater as with steady flow with the same mean Reynolds number. Zusammenfassung Es wird eine zweidimensionale numerische Untersuchung des instationären Wärmeübergangs und Druckverlustes im laminar durchströmten Spaltkanal mit einer plötzlichen Kanalerweiterung dargelegt und zwar für stationäre und periodische Geschwindigkeitsprofile am Eintritt des Kanals. Für stationäre Strömungen wurden die Form des Eintrittsprofils, die Reynoldszahl und die Kanalerweiterung variiert. Als Lösung der Navier/Stokes-und der Energiegleichungen mit periodischen Randbedingungen resultiert eine oszillierende Strömung, die das Aufplatzen des Primärwirbels in einer Schwingungsperiode zur Folge hat. Der Einfluß dieser Oszillation auf den Wärmeübergang und den Strömungsverlust wurde für die maximale Amplitude und für Re=100 eingehend untersucht.

19 CFR 146.66 - Transfer of merchandise from one zone to another.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 19 Customs Duties 2 2010-04-01 2010-04-01 false Transfer of merchandise from one zone to another... SECURITY; DEPARTMENT OF THE TREASURY (CONTINUED) FOREIGN TRADE ZONES Transfer of Merchandise From a Zone § 146.66 Transfer of merchandise from one zone to another. (a) At the same port. A transfer of...

19 CFR 146.66 - Transfer of merchandise from one zone to another.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 19 Customs Duties 2 2012-04-01 2012-04-01 false Transfer of merchandise from one zone to another... SECURITY; DEPARTMENT OF THE TREASURY (CONTINUED) FOREIGN TRADE ZONES Transfer of Merchandise From a Zone § 146.66 Transfer of merchandise from one zone to another. (a) At the same port. A transfer of...

19 CFR 146.66 - Transfer of merchandise from one zone to another.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 19 Customs Duties 2 2014-04-01 2014-04-01 false Transfer of merchandise from one zone to another... SECURITY; DEPARTMENT OF THE TREASURY (CONTINUED) FOREIGN TRADE ZONES Transfer of Merchandise From a Zone § 146.66 Transfer of merchandise from one zone to another. (a) At the same port. A transfer of...

19 CFR 146.66 - Transfer of merchandise from one zone to another.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 19 Customs Duties 2 2013-04-01 2013-04-01 false Transfer of merchandise from one zone to another... SECURITY; DEPARTMENT OF THE TREASURY (CONTINUED) FOREIGN TRADE ZONES Transfer of Merchandise From a Zone § 146.66 Transfer of merchandise from one zone to another. (a) At the same port. A transfer of...

19 CFR 146.66 - Transfer of merchandise from one zone to another.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 19 Customs Duties 2 2011-04-01 2011-04-01 false Transfer of merchandise from one zone to another... SECURITY; DEPARTMENT OF THE TREASURY (CONTINUED) FOREIGN TRADE ZONES Transfer of Merchandise From a Zone § 146.66 Transfer of merchandise from one zone to another. (a) At the same port. A transfer of...

Multi Seasonal and Diurnal Characterization of Sensible Heat Flux in an Arid Land Environment

NASA Astrophysics Data System (ADS)

Al-Mashharawi, S.; Aragon, B.; McCabe, M.

2017-12-01

In sparsely vegetated arid and semi-arid regions, the available energy is transformed primarily into sensible heat, with little to no energy partitioned into latent heat. The characterization of bare soil arid environments are rather poorly understood in the context of both local, regional and global energy budgets. Using data from a long-term surface layer scintillometer and co-located meteorological installation, we examine the diurnal and seasonal patterns of sensible heat flux and the net radiation to soil heat flux ratio. We do this over a bare desert soil located adjacent to an irrigated agricultural field in the central region of Saudi Arabia. The results of this exploratory analysis can be used to inform upon remote sensing techniques for surface flux estimation, to derive and monitor soil heat flux dynamics, estimate the heat transfer resistance and the thermal roughness length over bare soils, and to better inform efforts that model the advective effects that complicate the accurate representation of agricultural energy budgets in the arid zone.

ACHILLES: Heat Transfer in PWR Core During LOCA Reflood Phase

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

2013-11-01

1. NAME AND TITLE OF DATA LIBRARY ACHILLES -Heat Transfer in PWR Core During LOCA Reflood Phase. 2. NAME AND TITLE OF DATA RETRIEVAL PROGRAMS N/A 3. CONTRIBUTOR AEA Technology, Winfrith Technology Centre, Dorchester DT2 8DH United Kingdom through the OECD Nuclear Energy Agency Data Bank, Issy-les-Moulineaux, France. 4. DESCRIPTION OF TEST FACILITY The most important features of the Achilles rig were the shroud vessel, which contained the test section, and the downcomer. These may be thought of as representing the core barrel and the annular downcomer in the reactor pressure vessel. The test section comprises a cluster of 69more » rods in a square array within a circular shroud vessel. The rod diameter and pitch (9.5 mm and 12.6 mm) were typical of PWR dimensions. The internal diameter of the shroud vessel was 128 mm. Each rod was electrically heated over a length of 3.66 m, which is typical of the nuclear heated length in a PWR fuel rod, and each contained 6 internal thermocouples. These were arranged in one of 8 groupings which concentrated the thermocouples in different axial zones. The spacer grids were at prototypic PWR locations. Each grid had two thermocouples attached to its trailing edge at radial locations. The axial power profile along the rods was an 11 step approximation to a "chopped cosine". The shroud vessel had 5 heating zones whose power could be independently controlled. 5. DESCRIPTION OF TESTS The Achilles experiments investigated the heat transfer in the core of a Pressurized Water Reactor during the re-flood phase of a postulated large break loss of coolant accident. The results provided data to validate codes and to improve modeling. Different types of experiments were carried out which included single phase cooling, re-flood under low flow conditions, level swell and re-flood under high flow conditions. Three series of experiments were performed. The first and the third used the same test section but the second used another test section, similar in all respects except that it contained a partial blockage formed by attaching sleeves (or "balloons") to some of the rods. 6. SOURCE AND SCOPE OF DATA Phenomena Tested - Heat transfer in the core of a PWR during a re-flood phase of postulated large break LOCA. Test Designation - Achilles Rig. The programme includes the following types of experiments: - on an unballooned cluster: -- single phase air flow -- low pressure level swell -- low flooding rate re-flood -- high flooding rate re-flood - on a ballooned cluster containing 80% blockage formed by 16 balloon sleeves -- single phase air flow -- low flooding rate re-flood 7. DISCUSSION OF THE DATA RETRIEVAL PROGRAM N/A 8. DATA FORMAT AND COMPUTER Many Computers (M00019MNYCP00). 9. TYPICAL RUNNING TIME N/A 11. CONTENTS OF LIBRARY The ACHILLES package contains test data and associated data processing software as well as the documentation listed above. 12. DATE OF ABSTRACT November 2013. KEYWORDS: DATABASES, BENCHMARKS, HEAT TRANSFER, LOSS-OF-COLLANT ACCIDENT, PWR REACTORS, REFLOODING« less

Numerical analysis of impurity separation from waste salt by investigating the change of concentration at the interface during zone refining process

NASA Astrophysics Data System (ADS)

Choi, Ho-Gil; Shim, Moonsoo; Lee, Jong-Hyeon; Yi, Kyung-Woo

2017-09-01

The waste salt treatment process is required for the reuse of purified salts, and for the disposal of the fission products contained in waste salt during pyroprocessing. As an alternative to existing fission product separation methods, the horizontal zone refining process is used in this study for the purification of waste salt. In order to evaluate the purification ability of the process, three-dimensional simulation is conducted, considering heat transfer, melt flow, and mass transfer. Impurity distributions and decontamination factors are calculated as a function of the heater traverse rate, by applying a subroutine and the equilibrium segregation coefficient derived from the effective segregation coefficients. For multipass cases, 1d solutions and the effective segregation coefficient obtained from three-dimensional simulation are used. In the present study, the topic is not dealing with crystal growth, but the numerical technique used is nearly the same since the zone refining technique was just introduced in the treatment of waste salt from nuclear power industry because of its merit of simplicity and refining ability. So this study can show a new application of single crystal growth techniques to other fields, by taking advantage of the zone refining multipass possibility. The final goal is to achieve the same high degree of decontamination in the waste salt as in zone freezing (or reverse Bridgman) method.

Combustion and Heat Transfer Studies Utilizing Advanced Diagnostics: Combustion Studies

DTIC Science & Technology

1992-11-01

Research Zone With Combustion," Turbulent Shear Flows. VoL 5. pp. 337- and Development Center, Aero Propulsion and Power 346, Springer Verlg, New ...200 words) A long-term goal of the Air Force is to develop near-stoichiometric gas turbine combustors that will burn broad-specification fuels, and...laboratory combustors. Two novel methods for CARS slit function were developed ; these made possible precise and unambiguous measurements of flame

A global model for steady state and transient S.I. engine heat transfer studies

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

Bohac, S.V.; Assanis, D.N.; Baker, D.M.

1996-09-01

A global, systems-level model which characterizes the thermal behavior of internal combustion engines is described in this paper. Based on resistor-capacitor thermal networks, either steady-state or transient thermal simulations can be performed. A two-zone, quasi-dimensional spark-ignition engine simulation is used to determine in-cylinder gas temperature and convection coefficients. Engine heat fluxes and component temperatures can subsequently be predicted from specification of general engine dimensions, materials, and operating conditions. Emphasis has been placed on minimizing the number of model inputs and keeping them as simple as possible to make the model practical and useful as an early design tool. The successmore » of the global model depends on properly scaling the general engine inputs to accurately model engine heat flow paths across families of engine designs. The development and validation of suitable, scalable submodels is described in detail in this paper. Simulation sub-models and overall system predictions are validated with data from two spark ignition engines. Several sensitivity studies are performed to determine the most significant heat transfer paths within the engine and exhaust system. Overall, it has been shown that the model is a powerful tool in predicting steady-state heat rejection and component temperatures, as well as transient component temperatures.« less

Incorporating Cutting Edge Scientific Results from the Margins-Geoprisms Program into the Undergraduate Curriculum: The Subduction Factory

NASA Astrophysics Data System (ADS)

Penniston-Dorland, S.; Stern, R. J.; Edwards, B. R.; Kincaid, C. R.

2014-12-01

The NSF-MARGINS Program funded a decade of research on continental margin processes. The NSF-GeoPRISMS Mini-lesson Project, funded by NSF-TUES, is designed to integrate fundamental results from the MARGINS program into open-source college-level curriculum. Three Subduction Factory (SubFac) mini-lessons were developed as part of this project. These include hands-on examinations of data sets representing 3 key components of the subduction zone system: 1) Heat transfer in the subducted slab; 2) Metamorphic processes happening at the plate interface; and 3) Typical magmatic products of arc systems above subduction zones. Module 1: "Slab Temperatures Control Melting in Subduction Zones, What Controls Slab Temperature?" allows students to work in groups using beads rolling down slopes as an analog for the mathematics of heat flow. Using this hands-on, exploration-based approach, students develop an intuition for the mathematics of heatflow and learn about heat conduction and advection in the subduction zone environment. Module 2: "Subduction zone metamorphism" introduces students to the metamorphic rocks that form as the subducted slab descends and the mineral reactions that characterize subduction-related metamorphism. This module includes a suite of metamorphic rocks available for instructors to use in a lab, and exercises in which students compare pressure-temperature estimates obtained from metamorphic rocks to predictions from thermal models. Module 3: "Central American Arc Volcanoes, Petrology and Geochemistry" introduces students to basic concepts in igneous petrology using the Central American volcanic arc, a MARGINS Subduction Factory focus site, as an example. The module relates data from two different volcanoes - basaltic Cerro Negro (Nicaragua) and andesitic Ilopango (El Salvador) including hand sample observations and major element geochemistry - to explore processes of mantle and crustal melting and differentiation in arc volcanism.

On the Onset of Thermocapillary Convection in a Liquid bridge

NASA Astrophysics Data System (ADS)

Shukla, Kedar

Thermo capillary convection refers to motion driven by the application of a temperature gradient along the interface. The temperature gradient may be large enough to cause oscillations in the basic state of the fluid. The vast majority of the liquid bridge investigations performed aboard on the sounding rockets or the space shuttles [1, 2] focused on the float zone processes because the process has been regarded as a candidate for the space based manufacturing of semiconductor materials. Although the buoyancy effect is avoided in the floating zone techniques during space operation, it experiences surface tension driven convection initiated by the temperature gradient along the free surface of the zone [3]. The appearance of the oscillatory thermo capillary convection couples with the solidification processes leads to the striations and results into the degradation of the crystals [4, 5]. The half zone consists of the liquid bridge held between two solid, planar end walls across which a temperature gradient is applied. Thus the basic state of thermo capillary convection consists of a single toroidal roll with the surface motion directed downwards from the hot upper disc to the cold lower one. Bennacer et al [6] studied how different axial profiles of the heat flux affect the flow patterns and transition from ax symmetric steady to ax symmetric oscillatory flow. The three dimensional instability of liquid bridges located between isothermal differentially heated disks were studied by several authors [7-14]. The interface deformation caused by the gravity jitters depends on the volume of the liquid bridge and cause changes in the physical properties of the liquid, which ultimately influence the basic state of the fluid [15-16]. The paper discusses Marangoni convection in a liquid bridge subject to g-jitters in a micro gravity environment. The parametric excitement of the liquid bridge with surface tension variation along with the free surface is considered. We will follow the method of Shukla [17] for Boussinesq flow to model the convective instability in an axisymmetric flow in the liquid bridge. The surface deformation caused by g-jitters and its effects on the onset of oscillatory flow will be examined. References: [1] Grodzka, P.G. and Bannister, T.C., Heat flow and convection demonstration experiments abord Appolo 14, Science (Washington, D.C.), Vol.176, May 1972, pp. 506-508. [2] Bannister, T C., etal, NASA, TMX-64772, 1973. [3] Shukla, K.N. Hydrodynamics of Diffusive Processes, Applied Mechanics Review, Vol.54, No.5, 2001, pp. 391-404. [4] Chen, G., Lizee, A., Roux, B.,, Bifurcation analysis of the thermo capillary convection in cylindrical liquid bridge, J Crystal growth, Vol. 180, 1997, pp.638-647. [5] Imaishi, N., Yasuhiro, S., Akiyama, Y and Yoda, S., Numerical simulation of oscillatory Marangoni flow in half zone liquid bridge of low Prandtl number fluid, J., Crystal Growth, Vol. 230, 2001, pp. 164-171. [6] Bennacer, R., Mohamad, A.A., Leonardi, E., The effect o heat flux distribution on thermo capillary convection in a sideheated liquid bridge, Numer. Heat transfer, Part A, vol. 41, 2002, pp. 657-671. [7] Kuhlmann, H C., Rath, H J., Hydrodynamic instabilities in Cylindrical thermocapillary liquid bridges, J Fluid Mech., Vol. 247,1993, pp. 247-274. [8] Wanshura, M., Shevtsova, V M, Kuhlmann, H C and Rath, H J., Convective instability in thermocapillary liquid bridges, Phys. Fluids, Vol. 7, 1995, pp. 912-925. [9] Kasperski, G., Batoul, A., Labrosse, G., Up to the unsteadiness of axisymmetric thermocapillary low in a laterally heated liquid bridge, Phys. Fluids, Vol. 12, 2000, pp. 103-119. [10] Lappa, M., Savino, R., Monti, R., Three dimensional numerical simulation of Marangoni instabilities in non cylindrical liquid bridges in microgravity, Int. J Heat Mass Transfer, Vol. 44, 2001, pp. 1983-2003 [11] Zeng, Z, Mizuseki, H., Simamura, K., Fukud, T. Higashino, K, Kawaazoe, Y., Three dimensional oscillatory thermocapillary convection in liquid bridgeunder microgravity, Int. J heat Mass Transf., Vol. 44, 2001, pp. 3765-3774. [12] Kamotani, Y., Wang, L, Hatta, S., Wang, A., Yoda, S., Free surface heat loss effect on Oscillatory thermocapillary flow in a liquid bridges of high Prandtl number fluids, Int. J heat Mass Transfer, Vol. 46, 2003, pp. 3211-3220.

JPRS Report, Science & Technology Europe

DTIC Science & Technology

1988-07-27

materials research under microgravity conditions, such as ELLI, AMF of MHF ( Mirror Heating Facility) the Zone Melt- ing Furnace is a resistance-heated...pendently controlled zones. This is another advantage of a resistance-heated furnace over a mirror heating facil- ity. When the experiment requires a...zone, the subdivision into several heating zones will be preferable to the single light focus of a mirror heating facility. In 1987/88, following

Control of Thermal Convection in Layered Fluids Using Magnetic fields

NASA Technical Reports Server (NTRS)

Ramachandran, N.; Leslie, F. W.

2003-01-01

Immiscible fluid layers are found in a host of applications ranging from materials processing, for example the use of encapsulants in float zone crystal growth technique and a buffer layer in industrial Czochralski growth of crystals to prevent Marangoni convection, to heat transfer phenomena in day-to-day processes like the presence of air pockets in heat exchangers. In the microgravity and space processing realm, the exploration of other planets requires the development of enabling technologies in several fronts. The reduction in the gravity level poses unique challenges for fluid handling and heat transfer applications. The present work investigates the efficacy of controlling thermal convective flow using magnetic fluids and magnetic fields. The setup is a two-layer immiscible liquids system with one of the fluids being a diluted ferrofluid (super paramagnetic nano particles dispersed in carrier fluid). Using an external magnetic field one can essentially dial in a volumetric force - gravity level, on the magnetic fluid and thereby affect the system thermo-fluid behavior. The paper will describe the experimental and numerical modeling approach to the problem and discuss results obtained to date.

Thermostructural Analysis of Unconventional Wing Structures of a Hyper-X Hypersonic Flight Research Vehicle for the Mach 7 Mission

NASA Technical Reports Server (NTRS)

Ko, William L.; Gong, Leslie

2001-01-01

Heat transfer, thermal stresses, and thermal buckling analyses were performed on the unconventional wing structures of a Hyper-X hypersonic flight research vehicle (designated as X-43) subjected to nominal Mach 7 aerodynamic heating. A wing midspan cross section was selected for the heat transfer and thermal stress analyses. Thermal buckling analysis was performed on three regions of the wing skin (lower or upper); 1) a fore wing panel, 2) an aft wing panel, and 3) a unit panel at the middle of the aft wing panel. A fourth thermal buckling analysis was performed on a midspan wing segment. The unit panel region is identified as the potential thermal buckling initiation zone. Therefore, thermal buckling analysis of the Hyper-X wing panels could be reduced to the thermal buckling analysis of that unit panel. "Buckling temperature magnification factors" were established. Structural temperature-time histories are presented. The results show that the concerns of shear failure at wing and spar welded sites, and of thermal buckling of Hyper-X wing panels, may not arise under Mach 7 conditions.

Magnetic damping of thermocapillary convection in the floating-zone growth of semiconductor crystals

NASA Astrophysics Data System (ADS)

Morthland, Timothy Edward

The floating zone is one process used to grow high purity semiconductor single crystals. In the floating-zone process, a liquid bridge of molten semiconductor, or melt, is held by surface tension between the upper, melting polycrystalline feed rod and the lower, solidifying single crystal. A perfect crystal would require a quiescent melt with pure diffusion of dopants during the entire period needed to grow the crystal. However, temperature variations along the free surface of the melt lead to gradients of the temperature-dependent surface tension, driving a strong and unsteady flow in the melt, commonly labeled thermocapillary or Marangoni convection. For small temperature differences along the free surface, unsteady thermocapillary convection occurs, disrupting the diffusion controlled solidification and creating undesirable dopant concentration variations in the semiconductor single crystal. Since molten semiconductors are good electrical conductors, an externally applied, steady magnetic field can eliminate the unsteadiness in the melt and can reduce the magnitude of the residual steady motion. Crystal growers hope that a strong enough magnetic field will lead to diffusion controlled solidification, but the magnetic field strengths needed to damp the unsteady thermocapillary convection as a function of floating-zone process parameters is unknown. This research has been conducted in the area of the magnetic damping of thermocapillary convection in floating zones. Both steady and unsteady flows have been investigated. Due to the added complexities in solving Maxwells equations in these magnetohydrodynamic problems and due to the thin boundary layers in these flows, a direct numerical simulation of the fluid and heat transfer in the floating zone is virtually impossible, and it is certainly impossible to run enough simulations to search for neutral stability as a function of magnetic field strength over the entire parameter space. To circumvent these difficulties, we have used matched asymptotic expansions, linear stability theory and numerics to characterize these flows. Some fundamental aspects of the heat transfer and fluid mechanics in these magnetohydrodynamic flows are elucidated in addition to the calculation of the magnetic field strengths required to damp unsteady thermocapillary convection as a function of process parameters.

High resolution modeling of dense water formation in the north-western Mediterranean during winter 2012-2013: Processes and budget

NASA Astrophysics Data System (ADS)

Estournel, Claude; Testor, Pierre; Damien, Pierre; D'Ortenzio, Fabrizio; Marsaleix, Patrick; Conan, Pascal; Kessouri, Faycal; Durrieu de Madron, Xavier; Coppola, Laurent; Lellouche, Jean-Michel; Belamari, Sophie; Mortier, Laurent; Ulses, Caroline; Bouin, Marie-Noelle; Prieur, Louis

2016-07-01

The evolution of the stratification of the north-western Mediterranean between summer 2012 and the end of winter 2013 was simulated and compared with different sets of observations. A summer cruise and profiler observations were used to improve the initial conditions of the simulation. This improvement was crucial to simulate winter convection. Variations of some parameters involved in air - sea exchanges (wind, coefficient of transfer used in the latent heat flux formulation, and constant additive heat flux) showed that the characteristics of water masses and the volume of dense water formed during convection cannot be simply related to the time-integrated buoyancy budget over the autumn - winter period. The volume of dense water formed in winter was estimated to be about 50,000 km3 with a density anomaly larger than 29.113 kg m-3. The effect of advection and air/sea fluxes on the heat and salt budget of the convection zone was quantified during the preconditioning phase and the mixing period. Destratification of the surface layer in autumn occurs through an interaction of surface and Ekman buoyancy fluxes associated with displacements of the North Balearic front bounding the convection zone to the south. During winter convection, advection stratifies the convection zone: from December to March, the absolute value of advection represents 58 % of the effect of surface buoyancy fluxes.

Effect of wall heat transfer on shock-tube test temperature at long times

NASA Astrophysics Data System (ADS)

Frazier, C.; Lamnaouer, M.; Divo, E.; Kassab, A.; Petersen, E.

2011-02-01

When performing chemical kinetics experiments behind reflected shock waves at conditions of lower temperature (<1,000 K), longer test times on the order of 10-20 ms may be required. The integrity of the test temperature during such experiments may be in question, because heat loss to the tube walls may play a larger role than is generally seen in shock-tube kinetics experiments that are over within a millisecond or two. A series of detailed calculations was performed to estimate the effect of longer test times on the temperature uniformity of the post-shock test gas. Assuming the main mode of heat transfer is conduction between the high-temperature gas and the colder shock-tube walls, a comprehensive set of calculations covering a range of conditions including test temperatures between 800 and 1,800 K, pressures between 1 and 50 atm, driven-tube inner diameters between 3 and 16.2 cm, and test gases of N2 and Ar was performed. Based on the results, heat loss to the tube walls does not significantly reduce the area-averaged temperature behind the reflected shock wave for test conditions that are likely to be used in shock-tube studies for test times up to 20 ms (and higher), provided the shock-tube inner diameter is sufficiently large (>8cm). Smaller diameters on the order of 3 cm or less can experience significant temperature loss near the reflected-shock region. Although the area-averaged gas temperature decreases due to the heat loss, the main core region remains spatially uniform so that the zone of temperature change is limited to only the thermal layer adjacent to the walls. Although the heat conduction model assumes the gas and wall to behave as solid bodies, resulting in a core gas temperature that remains constant at the initial temperature, a two-zone gas model that accounts for density loss from the core to the colder thermal layer indicates that the core temperature and gas pressure both decrease slightly with time. A full CFD solution of the shock-tube flow field and heat transfer at long test times was also performed for one typical condition (800 K, 1 atm, Ar), the results of which indicate that the simpler analytical conduction model is realistic but somewhat conservative in that it over predicts the mean temperature loss by a few Kelvins. This paper presents the first comprehensive study on the effects of long test times on the average test gas temperature behind the reflected shock wave for conditions representative of chemical kinetics experiments.

Zone heating for fluidized bed silane pyrolysis

NASA Technical Reports Server (NTRS)

Iya, Sridhar K. (Inventor)

1987-01-01

An improved heated fluidized bed reactor and method for the production of high purity polycrystalline silicon by silane pyrolysis wherein silicon seed particles are heated in an upper heating zone of the reactor and admixed with particles in a lower reaction zone, in which zone a silane-containing gas stream, having passed through a lower cooled gas distribution zone not conducive to silane pyrolysis, contacts the heated seed particles whereon the silane is heterogeneously reduced to silicon.

Study of Periodical Flow Heat Transfer in an Internal Combustion Engine

NASA Astrophysics Data System (ADS)

Luo, Xi

In-cylinder heat transfer is one of the most critical physical behaviors which has a direct influence on engine out emission and thermal efficiency for IC engine. In-cylinder wall temperature has to be precisely controlled to achieve high efficiency and low emission. However, this cannot be done without knowing gas-to-wall heat flux. This study reports on the development of a technique suitable for engine in-cylinder surface temperature measurement, as the traditional method is "hard to reach." A laser induced phosphorescence technique was used to study in-cylinder wall temperature effects on engine out unburned hydrocarbons during the engine transitional period (warm up). A linear correlation was found between the cylinder wall surface temperature and the unburned hydrocarbons at mediate and high charge densities. At low charge density, no clear correlation was observed because of miss-fire events. A new auto background correction infrared (IR) diagnostic was developed to measure the instantaneous in-cylinder surface temperature at 0.1 CAD resolution. A numerical mechanism was designed to suppress relatively low-frequency background noise and provide an accurate in-cylinder surface temperature measurements with an error of less than 1.4% inside the IC engine. In addition, a proposed optical coating reduced time delay errors by 50% compared to more conventional thermocouple techniques. A new cycle-averaged Res number was developed for an IC engine to capture the characteristics of engine flow. Comparison and scaling between different engine flow parameters are available by matching the averaged Res number. From experimental results, the engine flow motion was classified as intermittently turbulent, and it is different from the original fully developed turbulent assumption, which has previously been used in almost all engine simulations. The intermittent turbulence could have a great impact on engine heat transfer because of the transitional turbulence effect. Engine 3D CFD model further proves the existence of transitional turbulence flow. A new multi zone heat transfer model is proposed for IC engines only. The model includes pressure work effects and improved heat transfer prediction compared to the standard Law of the wall model.

Simulation of heat and mass transfer processes in the experimental section of the air-condensing unit of Scientific Production Company "Turbocon"

NASA Astrophysics Data System (ADS)

Artemov, V. I.; Minko, K. B.; Yan'kov, G. G.; Kiryukhin, A. V.

2016-05-01

A mathematical model was developed to be used for numerical analysis of heat and mass transfer processes in the experimental section of the air condenser (ESAC) created in the Scientific Production Company (SPC) "Turbocon" and mounted on the territory of the All-Russia Thermal Engineering Institute. The simulations were performed using the author's CFD code ANES. The verification of the models was carried out involving the experimental data obtained in the tests of ESAC. The operational capability of the proposed models to calculate the processes in steam-air mixture and cooling air and algorithms to take into account the maldistribution in the various rows of tube bundle was shown. Data on the influence of temperature and flow rate of the cooling air on the pressure in the upper header of ESAC, effective heat transfer coefficient, steam flow distribution by tube rows, and the dimensions of the ineffectively operating zones of tube bundle for two schemes of steam-air mixture flow (one-pass and two-pass ones) were presented. It was shown that the pressure behind the turbine (in the upper header) increases significantly at increase of the steam flow rate and reduction of the flow rate of cooling air and its temperature rise, and the maximum value of heat transfer coefficient is fully determined by the flow rate of cooling air. Furthermore, the steam flow rate corresponding to the maximum value of heat transfer coefficient substantially depends on the ambient temperature. The analysis of the effectiveness of the considered schemes of internal coolant flow was carried out, which showed that the two-pass scheme is more effective because it provides lower pressure in the upper header, despite the fact that its hydraulic resistance at fixed flow rate of steam-air mixture is considerably higher than at using the one-pass schema. This result is a consequence of the fact that, in the two-pass scheme, the condensation process involves the larger internal surface of tubes, results in lower values of Δ t (the temperature difference between internal and external coolant) for a given heat load.

In situ study of the effect of ground source heat pump on shallow ground-water quality in the late Pleistocene terrace area of Tokyo, Japan

NASA Astrophysics Data System (ADS)

Takemura, T.; Uemura, K.; Akiba, Y.; Ota, M.

2015-12-01

The implementation of ground source heat pump (GSHP) systems has rapidly increased around the world, since they reduce carbon dioxide emissions and save electric energy. The GSHP system transfer heat into the geosphere zone when air conditioners are used to cool rooms or buildings. However, the effects of temperature increase on the quality of underground water has yet to be fully investigated. In order to reduce the risks of ground-water pollution by the installed GSHPs, it is important to evaluate the effect of temperature change on the ground-water quality. In this study, we installed a closed loop GSHP system on a heat exchange well along with a monitoring well drilled to measure ground-water quality and temperature. The monitoring well was drilled at 0.1cm away from the heat exchange well. We observed that changes of temperature in the heat exchange well affected the water quality, especially turbidity, in gravelly layer.

Acoustically enhanced heat exchange and drying apparatus

DOEpatents

Bramlette, T.T.; Keller, J.O.

1987-07-10

A heat transfer drying apparatus includes an acoustically augmented heat transfer chamber for receiving material to be dried. The chamber includes a first heat transfer gas inlet, a second heat transfer gas inlet, a material inlet, and a gas outlet which also serves as a dried material and gas outlet. A non-pulsing first heat transfer gas source provides a first drying gas to the acoustically augmented heat transfer chamber through the first heat transfer gas inlet. A valveless, continuous second heat transfer gas source provides a second drying gas to the acoustically augmented heat transfer chamber through the second heat transfer gas inlet. The second drying gas also generates acoustic waves which bring about acoustical coupling with the gases in the acoustically augmented heat transfer chamber. The second drying gas itself oscillates at an acoustic frequency of approximately 180 Hz due to fluid mechanical motion in the gas. The oscillations of the second heat transfer gas coupled to the first heat transfer gas in the acoustically augmented heat transfer chamber enhance heat and mass transfer by convection within the chamber. 3 figs.

Evaluation of direct-exchange areas for a cylindrical enclosure

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

Sika, J.

1991-11-01

This paper reports on a method for calculating the radiative heat transfer direct-exchange areas for surface-to-surface, volume-to-surface, and volume-to-volume pairs of zones in axisymmetric cylindrical geometries. With this method the calculation of the direct-exchange areas can be transformed from the original four-, five-, and sixfold integrals in the defining relations to just single and/or double integrals. Gray gas with absorption coefficient K is assumed.

Modeling of heat transfer in a vascular tissue-like medium during an interstitial hyperthermia process.

PubMed

Hassanpour, Saeid; Saboonchi, Ahmad

2016-12-01

This paper aims to evaluate the role of small vessels in heat transfer mechanisms of a tissue-like medium during local intensive heating processes, for example, an interstitial hyperthermia treatment. To this purpose, a cylindrical tissue with two co- and counter-current vascular networks and a central heat source is introduced. Next, the energy equations of tissue, supply fluid (arterial blood), and return fluid (venous blood) are derived using porous media approach. Then, a 2D computer code is developed to predict the temperature of blood (fluid phase) and tissue (solid phase) by conventional volume averaging method and a more realistic solution method. In latter method, despite the volume averaging the blood of interconnect capillaries is separated from the arterial and venous blood phases. It is found that in addition to blood perfusion rate, the arrangement of vascular network has considerable effects on the pattern and amount of the achieved temperature. In contrast to counter-current network, the co-current network of vessels leads to considerable asymmetric pattern of temperature contours and relocation of heat affected zone along the blood flow direction. However this relocation can be prevented by changing the site of hyperthermia heat source. The results show that the cooling effect of co-current blood vessels during of interstitial heating is more efficient. Despite much anatomical dissimilarities, these findings can be useful in designing of protocols for hyperthermia cancer treatment of living tissue. Copyright © 2016 Elsevier Ltd. All rights reserved.

Investigations of ash fouling with cattle wastes as reburn fuel in a small-scale boiler burner under transient conditions.

PubMed

Oh, Hyukjin; Annamalai, Kalyan; Sweeten, John M

2008-04-01

Fouling behavior under reburn conditions was investigated with cattle wastes (termed as feedlot biomass [FB]) and coal as reburn fuels under a transient condition and short-time operation. A small-scale (30 kW or 100,000 Btu/hr) boiler burner research facility was used for the reburn experiments. The fuels considered for these experiments were natural gas (NG) for the ashless case, pure coal, pure FB, and blends of coal and FB. Two parameters that were used to characterize the ash "fouling" were (1) the overall heat-transfer coefficient (OHTC) when burning NG and solid fuels as reburn fuels, and (2) the combustible loss through ash deposited on the surfaces of heat exchanger tubes and the bottom ash in the ash port. A new methodology is presented for determining ash-fouling behavior under transient conditions. Results on the OHTCs for solid reburn fuels are compared with the OHTCs for NG. It was found that the growth of the layer of ash depositions over longer periods typically lowers OHTC, and the increased concentration of ash in gas phase promotes radiation in high-temperature zones during initial periods while decreasing the heat transfer in low-temperature zones. The ash analyses indicated that the bottom ash in the ash port contained a smaller percentage of combustibles with a higher FB percentage in the fuels, indicating better performance compared with coal because small particles in FB burn faster and the FB has higher volatile matter on a dry ash-free basis promoting more burn out.

Liquid Cooling/Warming Garment

NASA Technical Reports Server (NTRS)

Koscheyev, Victor S.; Leon, Gloria R.; Dancisak, Michael J.

2010-01-01

The NASA liquid cooling/ventilating garment (LCVG) currently in use was developed over 40 years ago. With the commencement of a greater number of extra-vehicular activity (EVA) procedures with the construction of the International Space Station, problems of astronaut comfort, as well as the reduction of the consumption of energy, became more salient. A shortened liquid cooling/warming garment (SLCWG) has been developed based on physiological principles comparing the efficacy of heat transfer of different body zones; the capability of blood to deliver heat; individual muscle and fat body composition as a basis for individual thermal profiles to customize the zonal sections of the garment; and the development of shunts to minimize or redirect the cooling/warming loop for different environmental conditions, physical activity levels, and emergency situations. The SLCWG has been designed and completed, based on extensive testing in rest, exercise, and antiorthostatic conditions. It is more energy efficient than the LCVG currently used by NASA. The total length of tubing in the SLCWG is approximately 35 percent less and the weight decreased by 20 percent compared to the LCVG. The novel features of the innovation are: 1. The efficiency of the SLCWG to maintain thermal status under extreme changes in body surface temperatures while using significantly less tubing than the LCVG. 2. The construction of the garment based on physiological principles of heat transfer. 3. The identification of the body areas that are most efficient in heat transfer. 4. The inclusion of a hood as part of the garment. 5. The lesser consumption of energy.

Characterization of microstructure, local deformation and microchemistry in Alloy 690 heat-affected zone and stress corrosion cracking in high temperature water

NASA Astrophysics Data System (ADS)

Lu, Zhanpeng; Chen, Junjie; Shoji, Tetsuo; Takeda, Yoichi; Yamazaki, Seiya

2015-10-01

With increasing the distance from the weld fusion line in an Alloy 690 heat-affected zone, micro-hardness decreases, kernel average misorientation decreases and the fraction of Σ3 boundaries increases. Chromium depletion at grain boundaries in the Alloy 690 heat-affected zone is less significant than that in an Alloy 600 heat-affected zone. Alloy 690 heat-affected zone exhibits much higher IGSCC resistance than Alloy 600 heat-affected zone in simulated pressurized water reactor primary water. Heavily cold worked Alloy 690 exhibits localized intergranular stress corrosion cracking. The effects of metallurgical and mechanical properties on stress corrosion cracking in Alloy 690 are discussed.

Material properties and laser cutting of composites

NASA Astrophysics Data System (ADS)

Chen, Chia-Chieh; Cheng, Wing

Laser (Light Amplification by Stimulated Emission of Radiation) has been used successfully for many material cutting, drilling, metal welding and heat treating applications. However, laser cutting of polymer composites were attempted with varying degrees of success. Because composites are heterogeneous, the energy applied by laser could result in severe resin degradation before fibers were cut. In this study, cutting of glass, Kevlar, and graphite composites were evaluated based on their material properties and laser cutting parameters. A transient heat transfer analysis was used to determine the relative heat affected zones of these composites. Kevlar composites can be cut very well while graphite composites are difficult to cut. Though the cutting process is much more complicated in reality, the analysis provides a semi-quantitative perspective on the characteristics and limitations of laser cutting of different composites.

Heat transfer simulation and retort program adjustment for thermal processing of wheat based Haleem in semi-rigid aluminum containers.

PubMed

Vatankhah, Hamed; Zamindar, Nafiseh; Shahedi Baghekhandan, Mohammad

2015-10-01

A mixed computational strategy was used to simulate and optimize the thermal processing of Haleem, an ancient eastern food, in semi-rigid aluminum containers. Average temperature values of the experiments showed no significant difference (α = 0.05) in contrast to the predicted temperatures at the same positions. According to the model, the slowest heating zone was located in geometrical center of the container. The container geometrical center F0 was estimated to be 23.8 min. A 19 min processing time interval decrease in holding time of the treatment was estimated to optimize the heating operation since the preferred F0 of some starch or meat based fluid foods is about 4.8-7.5 min.

Development of Weld Metal Microstructures in Pulsed Laser Welding of Duplex Stainless Steel

NASA Astrophysics Data System (ADS)

Mirakhorli, F.; Malek Ghaini, F.; Torkamany, M. J.

2012-10-01

The microstructure of the weld metal of a duplex stainless steel made with Nd:YAG pulsed laser is investigated at different travel speeds and pulse frequencies. In terms of the solidification pattern, the weld microstructure is shown to be composed of two distinct zones. The presence of two competing heat transfer channels to the relatively cooler base metal and the relatively hotter previous weld spot is proposed to develop two zones. At high overlapping factors, an array of continuous axial grains at the weld centerline is formed. At low overlapping factors, in the zone of higher cooling rate, a higher percentage of ferrite is transformed to austenite. This is shown to be because with extreme cooling rates involved in pulsed laser welding with low overlapping, the ferrite-to-austenite transformation can be limited only to the grain boundaries.

Analysis of collapse in flattening a micro-grooved heat pipe by lateral compression

NASA Astrophysics Data System (ADS)

Li, Yong; He, Ting; Zeng, Zhixin

2012-11-01

The collapse of thin-walled micro-grooved heat pipes is a common phenomenon in the tube flattening process, which seriously influences the heat transfer performance and appearance of heat pipe. At present, there is no other better method to solve this problem. A new method by heating the heat pipe is proposed to eliminate the collapse during the flattening process. The effectiveness of the proposed method is investigated through a theoretical model, a finite element(FE) analysis, and experimental method. Firstly, A theoretical model based on a deformation model of six plastic hinges and the Antoine equation of the working fluid is established to analyze the collapse of thin walls at different temperatures. Then, the FE simulation and experiments of flattening process at different temperatures are carried out and compared with theoretical model. Finally, the FE model is followed to study the loads of the plates at different temperatures and heights of flattened heat pipes. The results of the theoretical model conform to those of the FE simulation and experiments in the flattened zone. The collapse occurs at room temperature. As the temperature increases, the collapse decreases and finally disappears at approximately 130 °C for various heights of flattened heat pipes. The loads of the moving plate increase as the temperature increases. Thus, the reasonable temperature for eliminating the collapse and reducing the load is approximately 130 °C. The advantage of the proposed method is that the collapse is reduced or eliminated by means of the thermal deformation characteristic of heat pipe itself instead of by external support. As a result, the heat transfer efficiency of heat pipe is raised.

Modelling and simulation of heat pipes with TAIThermIR (Conference Presentation)

NASA Astrophysics Data System (ADS)

Winkelmann, Max E.

2016-10-01

Regarding thermal camouflage usually one has to reduce the surface temperature of an object. All vehicles and installations having a combustion engine usually produce a lot of heat with results on hot spots on the surface which are highly conspicuous. Using heat pipes to transfer this heat to another place on the surface more efficiently might be a way to reduce those hotspots and the overall conspicuity. In a first approach, a model for the Software TAIThermIR was developed to test which parameters of the heat pipes are relevant and what effects can be achieved. It will be shown, that the thermal resistivity of contact zones are quite relevant and the thermal coupling of the engine (source of heat) defines if the alteration of the thermal signature is large or not. Furthermore the impact of the use of heat pipes in relation to surface material is discussed. The influence of different weather scenarios on the change of signatures due to the use of heat pipes is of minor relevance and depends on the choice of the surface material. Finally application issues for real systems are discussed.

Heat transfer and phase transitions of water in multi-layer cryolithozone-surface systems

NASA Astrophysics Data System (ADS)

Khabibullin, I. L.; Nigametyanova, G. A.; Nazmutdinov, F. F.

2018-01-01

A mathematical model for calculating the distribution of temperature and the dynamics of the phase transfor-mations of water in multilayer systems on permafrost-zone surface is proposed. The model allows one to perform calculations in the annual cycle, taking into account the distribution of temperature on the surface in warm and cold seasons. A system involving four layers, a snow or land cover, a top layer of soil, a layer of thermal-insulation materi-al, and a mineral soil, is analyzed. The calculations by the model allow one to choose the optimal thickness and com-position of the layers which would ensure the stability of structures built on the permafrost-zone surface.

Heat flow, morphology, pore fluids and hydrothermal circulation in a typical Mid-Atlantic Ridge flank near Oceanographer Fracture Zone

NASA Astrophysics Data System (ADS)

Le Gal, V.; Lucazeau, F.; Cannat, M.; Poort, J.; Monnin, C.; Battani, A.; Fontaine, F.; Goutorbe, B.; Rolandone, F.; Poitou, C.; Blanc-Valleron, M.-M.; Piedade, A.; Hipólito, A.

2018-01-01

Hydrothermal circulation affects heat and mass transfers in the oceanic lithosphere, not only at the ridge axis but also on their flanks, where the magnitude of this process has been related to sediment blanket and seamounts density. This was documented in several areas of the Pacific Ocean by heat flow measurements and pore water analysis. However, as the morphology of Atlantic and Indian ridge flanks is generally rougher than in the Pacific, these regions of slow and ultra-slow accretion may be affected by hydrothermal processes of different regimes. We carried out a survey of two regions on the eastern and western flanks of the Mid-Atlantic Ridge between Oceanographer and Hayes fracture zones. Two hundred and eight new heat flow measurements were obtained along six seismic profiles, on 5 to 14 Ma old seafloor. Thirty sediment cores (from which porewaters have been extracted) have been collected with a Kullenberg corer equipped with thermistors thus allowing simultaneous heat flow measurement. Most heat flow values are lower than those predicted by purely conductive cooling models, with some local variations and exceptions: heat flow values on the eastern flank of the study area are more variable than on the western flank, where they tend to increase westward as the sedimentary cover in the basins becomes thicker and more continuous. Heat flow is also higher, on average, on the northern sides of both the western and eastern field regions and includes values close to conductive predictions near the Oceanographer Fracture Zone. All the sediment porewaters have a chemical composition similar to that of bottom seawater (no anomaly linked to fluid circulation has been detected). Heat flow values and pore fluid compositions are consistent with fluid circulation in volcanic rocks below the sediment. The short distances between seamounts and short fluid pathways explain that fluids flowing in the basaltic aquifer below the sediment have remained cool and unaltered. Finally, relief at small-scale is calculated using variogram of bathymetry and compared for different regions affected by hydrothermal circulation.

Comparative study on the influence of depth, number and arrangement of dimples on the flow and heat transfer characteristics at turbulent flow regimes

NASA Astrophysics Data System (ADS)

Nazari, Saeed; Zamani, Mahdi; Moshizi, Sajad A.

2018-03-01

The ensuing study is dedicated to a series of numerical investigations concerning the effects of various geometric parameters of dimpled plates on the flow structure and heat transfer performance in a rectangular duct compared to the smooth plate. These parameters are the arrangement, number and depth of dimples. Two widely used staggered and square patterns in addition to a triangular arrangement, and three dimple depths (Δ = δ/d = 0.25, 0.375 and 0.5) have been chosen for this particular study. All studies have been conducted at three different Reynolds numbers Re = 25,000, 50,000 and 100,000. In order to capture the flow structures in the vicinity of dimples and contributing phenomena related to the boundary layer interactions, fully structured grids with y+ < 1 have been generated for all the cases. The realizable k t -ɛ two-layer model was selected as a proper turbulent model. It can be observed from the obtained results that higher effective area for heat transfer and a myriad of turbulent vortices mixing the hot fluid near the surface with the passing cold fluid generated from the downwind rims of dimples are the causes for improved average Nusselt number in the dimpled surface in comparison to the smooth plate. However, more pressure loss due to the higher friction drag and recirculation zones inside dimples will exist as a drawback in this system. Moreover, for all arrangements increasing dimple ratio Δ has a negative impact on the heat transfer augmentation and also deteriorates the pressure loss, which leads to this fact that Δ = 0.25 serves as the best option for the dimple depth.

Temperature of ground water at Philadelphia, Pennsylvania, 1979- 1981

USGS Publications Warehouse

Paulachok, Gary N.

1986-01-01

Anthropogenic heat production has undoubtedly caused increased ground-water temperatures in many parts of Philadelphia, Pennsylvania, as shown by temperatures of 98 samples and logs of 40 wells measured during 1979-81. Most sample temperatures were higher than 12.6 degrees Celsius (the local mean annual air temperature), and many logs depict cooling trends with depth (anomalous gradients). Heating of surface and shallow-subsurface materials has likely caused the elevated temperatures and anomalous gradients. Solar radiation on widespread concrete and asphalt surfaces, fossil-fuel combustion, and radiant losses from buried pipelines containing steam and process chemicals are believed to be the chief sources of heat. Some heat from these and other sources is transferred to deeper zones, mainly by conduction. Temperatures in densely urbanized areas are commonly highest directly beneath the land surface and decrease progressively with depth. Temperatures in sparsely urbanized areas generally follow the natural geothermal gradient and increase downward at about that same rate.

Apparatus and method of direct water cooling several parallel circuit cards each containing several chip packages

DOEpatents

Cipolla, Thomas M [Katonah, NY; Colgan, Evan George [Chestnut Ridge, NY; Coteus, Paul W [Yorktown Heights, NY; Hall, Shawn Anthony [Pleasantville, NY; Tian, Shurong [Mount Kisco, NY

2011-12-20

A cooling apparatus, system and like method for an electronic device includes a plurality of heat producing electronic devices affixed to a wiring substrate. A plurality of heat transfer assemblies each include heat spreaders and thermally communicate with the heat producing electronic devices for transferring heat from the heat producing electronic devices to the heat transfer assemblies. The plurality of heat producing electronic devices and respective heat transfer assemblies are positioned on the wiring substrate having the regions overlapping. A heat conduit thermally communicates with the heat transfer assemblies. The heat conduit circulates thermally conductive fluid therethrough in a closed loop for transferring heat to the fluid from the heat transfer assemblies via the heat spreader. A thermally conductive support structure supports the heat conduit and thermally communicates with the heat transfer assemblies via the heat spreader transferring heat to the fluid of the heat conduit from the support structure.

Modelica buildings library

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

Wetter, Michael; Zuo, Wangda; Nouidui, Thierry S.

This paper describes the Buildings library, a free open-source library that is implemented in Modelica, an equation-based object-oriented modeling language. The library supports rapid prototyping, as well as design and operation of building energy and control systems. First, we describe the scope of the library, which covers HVAC systems, multi-zone heat transfer and multi-zone airflow and contaminant transport. Next, we describe differentiability requirements and address how we implemented them. We describe the class hierarchy that allows implementing component models by extending partial implementations of base models of heat and mass exchangers, and by instantiating basic models for conservation equations andmore » flow resistances. We also describe associated tools for pre- and post-processing, regression tests, co-simulation and real-time data exchange with building automation systems. Furthermore, the paper closes with an example of a chilled water plant, with and without water-side economizer, in which we analyzed the system-level efficiency for different control setpoints.« less

Modelica buildings library

DOE PAGES

Wetter, Michael; Zuo, Wangda; Nouidui, Thierry S.; ...

2013-03-13

This paper describes the Buildings library, a free open-source library that is implemented in Modelica, an equation-based object-oriented modeling language. The library supports rapid prototyping, as well as design and operation of building energy and control systems. First, we describe the scope of the library, which covers HVAC systems, multi-zone heat transfer and multi-zone airflow and contaminant transport. Next, we describe differentiability requirements and address how we implemented them. We describe the class hierarchy that allows implementing component models by extending partial implementations of base models of heat and mass exchangers, and by instantiating basic models for conservation equations andmore » flow resistances. We also describe associated tools for pre- and post-processing, regression tests, co-simulation and real-time data exchange with building automation systems. Furthermore, the paper closes with an example of a chilled water plant, with and without water-side economizer, in which we analyzed the system-level efficiency for different control setpoints.« less

Operation of a cascade air conditioning system with two-phase loop

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

Feng, Yinshan; Wang, Jinliang; Zhao, Futao

A method of operating a heat transfer system includes starting operation of a first heat transfer fluid vapor/compression circulation loop including a fluid pumping mechanism, a heat exchanger for rejecting thermal energy from a first heat transfer fluid, and a heat absorption side of an internal heat exchanger. A first conduit in a closed fluid circulation loop circulates the first heat transfer fluid therethrough. Operation of a second two-phase heat transfer fluid circulation loop is started after starting operation of the first heat transfer fluid circulation loop. The second heat transfer fluid circulation loop transfers heat to the first heatmore » transfer fluid circulation loop through the internal heat exchanger and includes a heat rejection side of the internal heat exchanger, a liquid pump, and a heat exchanger evaporator. A second conduit in a closed fluid circulation loop circulates a second heat transfer fluid therethrough.« less

Processes for converting lignocellulosics to reduced acid pyrolysis oil

DOEpatents

Kocal, Joseph Anthony; Brandvold, Timothy A

2015-01-06

Processes for producing reduced acid lignocellulosic-derived pyrolysis oil are provided. In a process, lignocellulosic material is fed to a heating zone. A basic solid catalyst is delivered to the heating zone. The lignocellulosic material is pyrolyzed in the presence of the basic solid catalyst in the heating zone to create pyrolysis gases. The oxygen in the pyrolysis gases is catalytically converted to separable species in the heating zone. The pyrolysis gases are removed from the heating zone and are liquefied to form the reduced acid lignocellulosic-derived pyrolysis oil.

Tape Placement Head for Applying Thermoplastic Tape to an Object

NASA Technical Reports Server (NTRS)

Cope, Ralph D. (Inventor); Funck, Steve B. (Inventor); Gruber, Mark B. (Inventor); Lamontia, Mark A. (Inventor); Johnson, Anthony D. (Inventor)

2008-01-01

A tape placement head for applying thermoplastic tape to an object includes a heated feeder which guides the tape/tow to a heated zone. The heated zone has a line compactor having a single row of at least one movable heated member. An area compactor is located in the heated zone downstream from the line compactor. The area compactor includes a plurality of rows of movable feet which are extendable toward the tape/tow different distances with respect to each other to conform to the shape of the object. A shim is located between the heated compactors and the tape/tow. A chilled compactor is in a chilled zone downstream from the heated zone. The chilled zone includes a line chilled compactor and an area chilled compactor. A chilled shim is mounted between the chilled compactor and the tape/tow.

Study of issues in difficult-to-weld thick materials by hybrid laser arc welding

NASA Astrophysics Data System (ADS)

Mazar Atabaki, Mehdi

There is a high interest for the high strength-to-weight ratio with good ductility for the welds of advanced alloys. The concern about the welding of thick materials (Advanced high strength steels (AHSS) and 5xxx and 6xxx series of aluminum alloys) has stimulated the development of manufacturing processes to overcome the associated issues. The need to weld the dissimilar materials (AHSS and aluminum alloys) is also required for some specific applications in different industries. Hence, the requirement in the development of a state-of-the-art welding procedure can be helpful to fulfill the constraints. Among the welding methods hybrid laser/arc welding (HLAW) has shown to be an effective method to join thick and difficult-to-weld materials. This process benefits from both advantages of the gas metal arc welding (GMAW) and laser welding processes. The interaction of the arc and laser can help to have enough penetration of weld in thick plates. However, as the welding of dissimilar aluminum alloys and steels is very difficult because of the formation of brittle intermetallics the present work proposed a procedure to effectively join the alloys. The reports showed that the explosively welded aluminum alloys to steels have the highest toughness, and that could be used as an "insert" (TRICLAD) for welding the thick plates of AHSS to aluminum alloys. Therefore, the HLAW of the TRICLAD-Flange side (Aluminum alloy (AA 5456)) to the Web side (Aluminum alloys (AA 6061 and AA 5456)) and the TRICLAD-Flange side (ASTM A516) to the Web side (AHSS) was studied in the present work. However, there are many issues related to HLAW of the dissimilar steels as well as dissimilar aluminum alloys that have to be resolved in order to obtain sound welds. To address the challenges, the most recent welding methods for joining aluminum alloys to steels were studied and the microstructural development, mechanical properties, and on-line monitoring of the welding processes were discussed as well. The heat and mass transfer and the issues in joining of dissimilar alloys by the hybrid laser/arc welding process (HLAW) were explicitly explained in details. A finite element model was developed to simulate the heat transfer in HLAW of the aluminum alloys. Two double-ellipsoidal heat source models were considered to describe the heat input of the gas metal arc welding and laser welding processes. An experimental procedure was also developed for joining thick advanced high strength steel plates by using the HLAW, by taking into consideration different butt joint configurations. The geometry of the weld groove was optimized according to the requirements of ballistic test, where the length of the softened heat affected zone should be less than 15.9 mm measured from the weld centerline. Since the main issue in HLAW of the AHSS was the formation of the pores, the possible mechanisms of the pores formation and their mitigation methods during the welding process were investigated. Mitigation methods were proposed to reduce the pores inside in the weld area and the influence of each method on the process stability was investigated by an on-line monitoring system of the HLAW process. The groove angle was optimized for the welding process based on the allowed amount of heat input along the TRICLADRTM interface generated by an explosive welding. The weld was fractured in the heat affected zone of the aluminum side in the tensile test. The microharness was shown that the temperature variation caused minor softening in the heat affected zone satisfying the requirement that the width of the softened heat affected zone in the steel side falls within 15.9 mm far away from the weld centerline. The microstructure analysis showed the presence of tempered martensite at the vicinity of the weld area, which it was a cause of softening in the heat affected zone.

Model of convection mass transfer in titanium alloy at low energy high current electron beam action

NASA Astrophysics Data System (ADS)

Sarychev, V. D.; Granovskii, A. Yu; Nevskii, S. A.; Konovalov, S. V.; Gromov, V. E.

2017-01-01

The convection mixing model is proposed for low-energy high-current electron beam treatment of titanium alloys, pre-processed by heterogeneous plasma flows generated via explosion of carbon tape and powder TiB2. The model is based on the assumption vortices in the molten layer are formed due to the treatment by concentrated energy flows. These vortices evolve as the result of thermocapillary convection, arising because of the temperature gradient. The calculation of temperature gradient and penetration depth required solution of the heat problem with taking into account the surface evaporation. However, instead of the direct heat source the boundary conditions in phase transitions were changed in the thermal conductivity equation, assuming the evaporated material takes part in the heat exchange. The data on the penetration depth and temperature distribution are used for the thermocapillary model. The thermocapillary model embraces Navier-Stocks and convection heat transfer equations, as well as the boundary conditions with the outflow of evaporated material included. The solution of these equations by finite elements methods pointed at formation of a multi-vortices structure when electron-beam treatment and its expansion over new zones of material. As the result, strengthening particles are found at the depth exceeding manifold their penetration depth in terms of the diffusion mechanism.

Crowdsourcing urban air temperatures through smartphone battery temperatures in São Paulo, Brazil

NASA Astrophysics Data System (ADS)

Droste, Arjan; Pape, Jan-Jaap; Overeem, Aart; Leijnse, Hidde; Steeneveld, Gert-Jan; Van Delden, Aarnout; Uijlenhoet, Remko

2017-04-01

Crowdsourcing as a method to obtain and apply vast datasets is rapidly becoming prominent in meteorology, especially for urban areas where traditional measurements are scarce. Earlier studies showed that smartphone battery temperature readings allow for estimating the daily and city-wide air temperature via a straightforward heat transfer model. This study advances these model estimations by studying spatially and temporally smaller scales. The accuracy of temperature retrievals as a function of the number of battery readings is also studied. An extensive dataset of over 10 million battery temperature readings is available for São Paulo (Brazil), for estimating hourly and daily air temperatures. The air temperature estimates are validated with air temperature measurements from a WMO station, an Urban Fluxnet site, and crowdsourced data from 7 hobby meteorologists' private weather stations. On a daily basis temperature estimates are good, and we show they improve by optimizing model parameters for neighbourhood scales as categorized in Local Climate Zones. Temperature differences between Local Climate Zones can be distinguished from smartphone battery temperatures. When validating the model for hourly temperature estimates, initial results are poor, but are vastly improved by using a diurnally varying parameter function in the heat transfer model rather than one fixed value for the entire day. The obtained results show the potential of large crowdsourced datasets in meteorological studies, and the value of smartphones as a measuring platform when routine observations are lacking.

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.

Capillary-Condenser-Pumped Heat-Transfer Loop

NASA Technical Reports Server (NTRS)

Silverstein, Calvin C.

1989-01-01

Heat being transferred supplies operating power. Capillary-condenser-pumped heat-transfer loop similar to heat pipe and to capillary-evaporator-pumped heat-transfer loop in that heat-transfer fluid pumped by evaporation and condensation of fluid at heat source and sink, respectively. Capillary condenser pump combined with capillary evaporator pump to form heat exchanger circulating heat-transfer fluids in both loops. Transport of heat more nearly isothermal. Thermal stress in loop reduced, and less external surface area needed in condenser section for rejection of heat to heat sink.

Axial flow heat exchanger devices and methods for heat transfer using axial flow devices

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

Koplow, Jeffrey P.

Systems and methods described herein are directed to rotary heat exchangers configured to transfer heat to a heat transfer medium flowing in substantially axial direction within the heat exchangers. Exemplary heat exchangers include a heat conducting structure which is configured to be in thermal contact with a thermal load or a thermal sink, and a heat transfer structure rotatably coupled to the heat conducting structure to form a gap region between the heat conducting structure and the heat transfer structure, the heat transfer structure being configured to rotate during operation of the device. In example devices heat may be transferredmore » across the gap region from a heated axial flow of the heat transfer medium to a cool stationary heat conducting structure, or from a heated stationary conducting structure to a cool axial flow of the heat transfer medium.« less

Fuel conditioning facility zone-to-zone transfer administrative controls.

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

Pope, C. L.

2000-06-21

The administrative controls associated with transferring containers from one criticality hazard control zone to another in the Argonne National Laboratory (ANL) Fuel Conditioning Facility (FCF) are described. FCF, located at the ANL-West site near Idaho Falls, Idaho, is used to remotely process spent sodium bonded metallic fuel for disposition. The process involves nearly forty widely varying material forms and types, over fifty specific use container types, and over thirty distinct zones where work activities occur. During 1999, over five thousand transfers from one zone to another were conducted. Limits are placed on mass, material form and type, and container typesmore » for each zone. Ml material and containers are tracked using the Mass Tracking System (MTG). The MTG uses an Oracle database and numerous applications to manage the database. The database stores information specific to the process, including material composition and mass, container identification number and mass, transfer history, and the operators involved in each transfer. The process is controlled using written procedures which specify the zone, containers, and material involved in a task. Transferring a container from one zone to another is called a zone-to-zone transfer (ZZT). ZZTs consist of four distinct phases, select, request, identify, and completion.« less

Heat transfer fluids containing nanoparticles

DOEpatents

Singh, Dileep; Routbort, Jules; Routbort, A.J.; Yu, Wenhua; Timofeeva, Elena; Smith, David S.; France, David M.

2016-05-17

A nanofluid of a base heat transfer fluid and a plurality of ceramic nanoparticles suspended throughout the base heat transfer fluid applicable to commercial and industrial heat transfer applications. The nanofluid is stable, non-reactive and exhibits enhanced heat transfer properties relative to the base heat transfer fluid, with only minimal increases in pumping power required relative to the base heat transfer fluid. In a particular embodiment, the plurality of ceramic nanoparticles comprise silicon carbide and the base heat transfer fluid comprises water and water and ethylene glycol mixtures.

Modeling fluid flow and heat transfer at Basin and Range faults: preliminary results for Leach hot springs, Nevada

USGS Publications Warehouse

López, Dina L.; Smith, Leslie; Storey, Michael L.; Nielson, Dennis L.

1994-01-01

The hydrothermal systems of the Basin and Range Province are often located at or near major range bounding normal faults. The flow of fluid and energy at these faults is affected by the advective transfer of heat and fluid from an to the adjacent mountain ranges and valleys, This paper addresses the effect of the exchange of fluid and energy between the country rock, the valley fill sediments, and the fault zone, on the fluid and heat flow regimes at the fault plane. For comparative purposes, the conditions simulated are patterned on Leach Hot Springs in southern Grass Valley, Nevada. Our simulations indicated that convection can exist at the fault plane even when the fault is exchanging significant heat and fluid with the surrounding country rock and valley fill sediments. The temperature at the base of the fault decreased with increasing permeability of the country rock. Higher groundwater discharge from the fault and lower temperatures at the base of the fault are favored by high country rock permabilities and fault transmissivities. Preliminary results suggest that basal temperatures and flow rates for Leach Hot Springs can not be simulated with a fault 3 km deep and an average regional heat flow of 150 mW/m2 because the basal temperature and mass discharge rates are too low. A fault permeable to greater depths or a higher regional heat flow may be indicated for these springs.

Effects of momentum transfer on sizing of current collectors for lithium-ion batteries during laser cutting

NASA Astrophysics Data System (ADS)

Lee, Dongkyoung; Mazumder, Jyotirmoy

2018-02-01

One of the challenges of the lithium-ion battery manufacturing process is the sizing of electrodes with good cut surface quality. Poor cut surface quality results in internal short circuits in the cells and significant heat generation. One of the solutions that may improve the cut quality with a high cutting speed is laser cutting due to its high energy concentration, fast processing time, high precision, small heat affected zone, flexible range of laser power and contact free process. In order to utilize the advantages of laser electrode cutting, understanding the physical phenomena for each material is crucial. Thus, this study focuses on the laser cutting of current collectors, such as pure copper and aluminum. A 3D self-consistent mathematical model for the laser cutting, including fluid flow, heat transfer, recoil pressure, multiple reflections, capillary and thermo-capillary forces, and phase changes, is presented and solved numerically. Simulation results for the laser cutting are analyzed in terms of penetration time, depth, width, and absorptivity, based on these selected laser parameters. In addition, melt pool flow, melt pool geometry and temperature distribution are investigated.

77 FR 50921 - Safety Zone: Bay Bridge Load Transfer Safety Zone, San Francisco Bay, San Francisco, CA

Federal Register 2010, 2011, 2012, 2013, 2014

2012-08-23

...-AA00 Safety Zone: Bay Bridge Load Transfer Safety Zone, San Francisco Bay, San Francisco, CA AGENCY... the Bay Bridge Load Transfer Safety Zone from August 1, 2012 through October 31, 2012. This safety... Bay Bridge from the temporary suspension arrangement to the permanent suspension arrangement, the...

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

Abboud, Alexander; Guillen, Donna Post; Pokorny, Richard

At the Hanford site in the state of Washington, more than 56 million gallons of radioactive waste is stored in underground tanks. The cleanup plan for this waste is vitrification at the Waste Treatment Plant (WTP), currently under construction. At the WTP, the waste will be blended with glass-forming materials and heated to 1423K, then poured into stainless steel canisters to cool and solidify. A fundamental understanding of the glass batch melting process is needed to optimize the process to reduce cost and decrease the life cycle of the cleanup effort. The cold cap layer that floats on the surfacemore » of the glass melt is the primary reaction zone for the feed-to-glass conversion. The conversion reactions include water release, melting of salts, evolution of batch gases, dissolution of quartz and the formation of molten glass. Obtaining efficient heat transfer to this region is crucial to achieving high rates of glass conversion. Computational fluid dynamics (CFD) modeling is being used to understand the heat transfer dynamics of the system and provide insight to optimize the process. A CFD model was developed to simulate the DM1200, a pilot-scale melter that has been extensively tested by the Vitreous State Laboratory (VSL). Electrodes are built into the melter to provide Joule heating to the molten glass. To promote heat transfer from the molten glass into the reactive cold cap layer, bubbling of the molten glass is used to stimulate forced convection within the melt pool. A three-phase volume of fluid approach is utilized to model the system, wherein the molten glass and cold cap regions are modeled as separate liquid phases, and the bubbling gas and plenum regions are modeled as one lumped gas phase. The modeling of the entire system with a volume of fluid model allows for the prescription of physical properties on a per-phase basis. The molten glass phase and the gas phase physical properties are obtained from previous experimental work. Finding representative properties for the cold cap region is more difficult, as this region is not a true liquid, but rather a multilayer region consisting of a porous and a foamy layer. Physical properties affecting heat transfer, namely the thermal conductivity and heat capacity, have been fit to closely match data and observations from laboratory experiments. Data from xray tomography and quenching of laboratory-scale cold caps provide insight into the topology of bubble distribution within the cold cap at various temperatures. Heat transfer within the melter was validated by comparison with VSL data for the pilot-scale melter.« less

Data center coolant switch

DOEpatents

Iyengar, Madhusudan K.; Parida, Pritish R.; Schultz, Mark D.

2015-10-06

A data center cooling system is operated in a first mode; it has an indoor portion wherein heat is absorbed from components in the data center, and an outdoor heat exchanger portion wherein outside air is used to cool a first heat transfer fluid (e.g., water) present in at least the outdoor heat exchanger portion of the cooling system during the first mode. The first heat transfer fluid is a relatively high performance heat transfer fluid (as compared to the second fluid), and has a first heat transfer fluid freezing point. A determination is made that an appropriate time has been reached to switch from the first mode to a second mode. Based on this determination, the outdoor heat exchanger portion of the data cooling system is switched to a second heat transfer fluid, which is a relatively low performance heat transfer fluid, as compared to the first heat transfer fluid. It has a second heat transfer fluid freezing point lower than the first heat transfer fluid freezing point, and the second heat transfer fluid freezing point is sufficiently low to operate without freezing when the outdoor air temperature drops below a first predetermined relationship with the first heat transfer fluid freezing point.

On the physics of waves in the solar atmosphere: Wave heating and wind acceleration

NASA Technical Reports Server (NTRS)

Musielak, Z. E.

1994-01-01

This paper presents work performed on the generation and physics of acoustic waves in the solar atmosphere. The investigators have incorporated spatial and temporal turbulent energy spectra in a newly corrected version of the Lighthill-Stein theory of acoustic wave generation in order to calculate the acoustic wave energy fluxes generated in the solar convective zone. The investigators have also revised and improved the treatment of the generation of magnetic flux tube waves, which can carry energy along the tubes far away from the region of their origin, and have calculated the tube wave energy fluxes for the sun. They also examine the transfer of the wave energy originated in the solar convective zone to the outer atmospheric layers through computation of wave propagation and dissipation in highly nonhomogeneous solar atmosphere. These waves may efficiently heat the solar atmosphere and the heating will be especially significant in the chromospheric network. It is also shown that the role played by Alfven waves in solar wind acceleration and coronal hole heating is dominant. The second part of the project concerned investigation of wave propagation in highly inhomogeneous stellar atmospheres using an approach based on an analytic tool developed by Musielak, Fontenla, and Moore. In addition, a new technique based on Dirac equations has been developed to investigate coupling between different MHD waves propagating in stratified stellar atmospheres.

On the physics of waves in the solar atmosphere: Wave heating and wind acceleration

NASA Technical Reports Server (NTRS)

Musielak, Z. E.

1993-01-01

This paper presents work performed on the generation and physics of acoustic waves in the solar atmosphere. The investigators have incorporated spatial and temporal turbulent energy spectra in a newly corrected version of the Lighthill-Stein theory of acoustic wave generation in order to calculate the acoustic wave energy fluxes generated in the solar convective zone. The investigators have also revised and improved the treatment of the generation of magnetic flux tube waves, which can carry energy along the tubes far away from the region of their origin, and have calculated the tube energy fluxes for the sun. They also examine the transfer of the wave energy originated in the solar convective zone to the outer atmospheric layers through computation of wave propagation and dissipation in highly nonhomogeneous solar atmosphere. These waves may efficiently heat the solar atmosphere and the heating will be especially significant in the chromospheric network. It is also shown that the role played by Alfven waves in solar wind acceleration and coronal hole heating is dominant. The second part of the project concerned investigation of wave propagation in highly inhomogeneous stellar atmospheres using an approach based on an analytic tool developed by Musielak, Fontenla, and Moore. In addition, a new technique based on Dirac equations has been developed to investigate coupling between different MHD waves propagating in stratified stellar atmospheres.

Evaluation of the energy transfer in the char zone during ablation. Part 2: In-depth response of ablative composites, volume 1. Ph.D. Thesis, 1975. Final Report

NASA Technical Reports Server (NTRS)

Pike, R. W.; Delvalle, E. G.

1974-01-01

The decomposition of ablative composites is described along with the transport phenomena of pyrolysis gases which result from the decomposition of these plastics as they flow through the porous char of char-forming ablators. The pyrolysis products are those formed by the thermal degradation of nylon-phenolic resin and silicone elastomer composites. Emphasis is placed on the nature and extent of chemical reactions of the pyrolysis products and the char, along with the energy absorbed by the combined pyrolysis and char zone. Chemical reactions with thermodynamically consistent kinetic data are determined in order to develop a realistic analysis for predicting the thermal performance of ablative heat shields.

Investigations of ash fouling with cattle wastes as reburn fuel in a small-scale boiler burner under transient conditions

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

Hyukjin Oh; Kalyan Annamalai; John M. Sweeten

2008-04-15

Fouling behavior under reburn conditions was investigated with cattle wastes (termed as feedlot biomass, FB) and coal as reburn fuels under a transient condition and short-time operation. A small-scale (30 kW or 100,000 Btu/hr) boiler burner research facility was used for the reburn experiments. The fuels considered for these experiments were natural gas (NG) for the ashless case, pure coal, pure FB, and blends of coal and FB. Two parameters that were used to characterize the ash 'fouling' were (1) the overall heat-transfer coefficient (OHTC) when burning NG and solid fuels as reburn fuels, and (2) the combustible loss throughmore » ash deposited on the surfaces of heat exchanger tubes and the bottom ash in the ash port. A new methodology is presented for determining ash fouling behavior under transient conditions. Results on the OHTCs for solid reburn fuels are compared with the OHTCs for NG. It was found that the growth of the layer of ash depositions over longer periods typically lowers OHTC, and the increased concentration of ash in gas phase promotes radiation in high-temperature zones during initial periods while decreasing the heat transfer in low-temperature zones. The ash analyses indicated that the bottom ash in the ash port contained a smaller percentage of combustibles with a higher FB percentage in the fuels, indicating better performance compared with coal because small particles in FB burn faster and the FB has higher volatile matter on a dry ash-free basis promoting more burn out. 16 refs., 12 figs., 6 tabs.« less

Design and Control of Hydronic Radiant Cooling Systems

NASA Astrophysics Data System (ADS)

Feng, Jingjuan

Improving energy efficiency in the Heating Ventilation and Air conditioning (HVAC) systems in buildings is critical to achieve the energy reduction in the building sector, which consumes 41% of all primary energy produced in the United States, and was responsible for nearly half of U.S. CO2 emissions. Based on a report by the New Building Institute (NBI), when HVAC systems are used, about half of the zero net energy (ZNE) buildings report using a radiant cooling/heating system, often in conjunction with ground source heat pumps. Radiant systems differ from air systems in the main heat transfer mechanism used to remove heat from a space, and in their control characteristics when responding to changes in control signals and room thermal conditions. This dissertation investigates three related design and control topics: cooling load calculations, cooling capacity estimation, and control for the heavyweight radiant systems. These three issues are fundamental to the development of accurate design/modeling tools, relevant performance testing methods, and ultimately the realization of the potential energy benefits of radiant systems. Cooling load calculations are a crucial step in designing any HVAC system. In the current standards, cooling load is defined and calculated independent of HVAC system type. In this dissertation, I present research evidence that sensible zone cooling loads for radiant systems are different from cooling loads for traditional air systems. Energy simulations, in EnergyPlus, and laboratory experiments were conducted to investigate the heat transfer dynamics in spaces conditioned by radiant and air systems. The results show that the magnitude of the cooling load difference between the two systems ranges from 7-85%, and radiant systems remove heat faster than air systems. For the experimental tested conditions, 75-82% of total heat gain was removed by radiant system during the period when the heater (simulating the heat gain) was on, while for air system, 61-63% were removed. From a heat transfer perspective, the differences are mainly because the chilled surfaces directly remove part of the radiant heat gains from a zone, thereby bypassing the time-delay effect caused by the interaction of radiant heat gain with non-active thermal mass in air systems. The major conclusions based on these findings are: 1) there are important limitations in the definition of cooling load for a mixing air system described in Chapter 18 of ASHRAE Handbook of Fundamentals when applied to radiant systems; 2) due to the obvious mismatch between how radiant heat transfer is handled in traditional cooling load calculation methods compared to its central role in radiant cooling systems, this dissertation provides improvements for the current cooling load calculation method based on the Heat Balance procedure. The Radiant Time Series method is not appropriate for radiant system applications. The findings also directly apply to the selection of space heat transfer modeling algorithms that are part of all energy modeling software. Cooling capacity estimation is another critical step in a design project. The above mentioned findings and a review of the existing methods indicates that current radiant system cooling capacity estimation methods fail to take into account incident shortwave radiation generated by solar and lighting in the calculation process. This causes a significant underestimation (up to 150% for some instances) of floor cooling capacity when solar load is dominant. Building performance simulations were conducted to verify this hypothesis and quantify the impacts of solar for different design scenarios. A new simplified method was proposed to improve the predictability of the method described in ISO 11855 when solar radiation is present. The dissertation also compares the energy and comfort benefits of the model-based predictive control (MPC) method with a fine-tuned heuristic control method when applied to a heavyweight embedded surface system. A first order dynamic model of a radiant slab system was developed for implementation in model predictive controllers. A calibrated EnergyPlus model of a typical office building in California was used as a testbed for the comparison. The results indicated that MPC is able to reduce the cooling tower energy consumption by 55% and pumping power consumption by 26%, while maintaining equivalent or even better thermal comfort conditions. In summary, the dissertation work has: (1) provided clear evidence that the fundamental heat transfer mechanisms differ between radiant and air systems. These findings have important implications for the development of accurate and reliable design and energy simulation tools; (2) developed practical design methods and guidance to aid practicing engineers who are designing radiant systems; and (3) outlined future research and design tools need to advance the state-of-knowledge and design and operating guidelines for radiant systems.

The impact of bed temperature on heat transfer characteristic between fluidized bed and vertical rifled tubes

NASA Astrophysics Data System (ADS)

Blaszczuk, Artur; Nowak, Wojciech

2016-10-01

In the present work, the heat transfer study focuses on assessment of the impact of bed temperature on the local heat transfer characteristic between a fluidized bed and vertical rifled tubes (38mm-O.D.) in a commercial circulating fluidized bed (CFB) boiler. Heat transfer behavior in a 1296t/h supercritical CFB furnace has been analyzed for Geldart B particle with Sauter mean diameter of 0.219 and 0.246mm. The heat transfer experiments were conducted for the active heat transfer surface in the form of membrane tube with a longitudinal fin at the tube crest under the normal operating conditions of CFB boiler. A heat transfer analysis of CFB boiler with detailed consideration of the bed-to-wall heat transfer coefficient and the contribution of heat transfer mechanisms inside furnace chamber were investigated using mechanistic heat transfer model based on cluster renewal approach. The predicted values of heat transfer coefficient are compared with empirical correlation for CFB units in large-scale.

Quantifying the Role of Atmospheric Forcing in Ice Edge Retreat and Advance Including Wind-Wave Coupling

DTIC Science & Technology

2015-09-30

Quantifying the Role of Atmospheric Forcing in Ice Edge Retreat and Advance Including Wind- Wave Coupling Peter S. Guest (NPS Technical Contact) Naval...surface fluxes and ocean waves in coupled models in the Beaufort and Chukchi Seas. 2. Understand the physics of heat and mass transfer from the ocean...to the atmosphere. 3. Improve forecasting of waves on the open ocean and in the marginal ice zone. 2 OBJECTIVES 1. Quantifying the open-ocean

Reactor for fluidized bed silane decomposition

NASA Technical Reports Server (NTRS)

Iya, Sridhar K. (Inventor)

1989-01-01

An improved heated fluidized bed reactor and method for the production of high purity polycrystalline silicon by silane pyrolysis wherein silicon seed particles are heated in an upper heating zone of the reactor and admixed with particles in a lower zone, in which zone a silane-containing gas stream, having passed through a lower cooled gas distribution zone not conducive to silane pyrolysis, contacts the heated seed particles whereon the silane is heterogeneously reduced to silicon.

Europa, tidally heated oceans, and habitable zones around giant planets

NASA Astrophysics Data System (ADS)

Reynolds, R. T.; McKay, C. P.; Kasting, J. F.

Tidal dissipation in the satellites of a giant planet may provide sufficient heating to maintain an environment favorable to life on the satellite surface or just below a thin ice layer. Europa could have a liquid ocean which may occasionally receive sunlight through cracks in the overlying ice shell. In such a case, sufficient solar energy could reach liquid water that organisms similar to those found under Antarctic ice could grow. In other solar systems, larger satellites with more significant heat flow could represent environments that are stable over an order of eons and in which life could perhaps evolve. A zone around a giant planet is defined in which such satellites could exist as a tidally-heated habitable zone. This zone can be compared to the habitable zone which results from heating due to the radiation of a central star. In this solar system, this radiatively-heated habitable zone contains the earth.

Europa, tidally heated oceans, and habitable zones around giant planets

NASA Technical Reports Server (NTRS)

Reynolds, Ray T.; Mckay, Christopher P.; Kasting, James F.

1987-01-01

Tidal dissipation in the satellites of a giant planet may provide sufficient heating to maintain an environment favorable to life on the satellite surface or just below a thin ice layer. Europa could have a liquid ocean which may occasionally receive sunlight through cracks in the overlying ice shell. In such a case, sufficient solar energy could reach liquid water that organisms similar to those found under Antarctic ice could grow. In other solar systems, larger satellites with more significant heat flow could represent environments that are stable over an order of eons and in which life could perhaps evolve. A zone around a giant planet is defined in which such satellites could exist as a tidally-heated habitable zone. This zone can be compared to the habitable zone which results from heating due to the radiation of a central star. In this solar system, this radiatively-heated habitable zone contains the earth.

Multi-zone cooling/warming garment

NASA Technical Reports Server (NTRS)

Leon, Gloria R. (Inventor); Koscheyev, Victor S. (Inventor); Dancisak, Michael J. (Inventor)

2006-01-01

A thermodynamically efficient garment for cooling and/or heating a human body. The thermodynamic efficiency is provided in part by targeting the heat exchange capabilities of the garment to specific areas and/or structures of the human body. The heat exchange garment includes heat exchange zones and one or more non-heat exchange zones, where the heat exchange zones are configured to correspond to one or more high density tissue areas of the human body when the garment is worn. A system including the garment can be used to exchange heat with the adjacent HD tissue areas under the control of a feedback control system. Sensed physiological parameters received by the feedback control system can be used to adjust the characteristics of heat exchange fluid moving within the heat exchange garment.

19 CFR 191.184 - Merchandise transferred from continuous Customs custody.

Code of Federal Regulations, 2010 CFR

2010-04-01

... SECURITY; DEPARTMENT OF THE TREASURY (CONTINUED) DRAWBACK Merchandise Transferred to a Foreign Trade Zone..., for drawback on merchandise transferred to a foreign trade zone from continuous Customs custody. (b) Drawback entry. Before the transfer of merchandise from continuous Customs custody to a foreign trade zone...

Linking Plagioclase Zoning Patterns to Active Magma Processes

NASA Astrophysics Data System (ADS)

Izbekov, P. E.; Nicolaysen, K. P.; Neill, O. K.; Shcherbakov, V.; Plechov, P.; Eichelberger, J. C.

2015-12-01

Plagioclase, one of the most common and abundant mineral phases in volcanic products, will vary in composition in response to changes in temperature, pressure, composition of the ambient silicate melt, and melt H2O concentration. Changes in these parameters may cause dissolution or growth of plagioclase crystals, forming characteristic textural and compositional variations (zoning patterns), the complete core-to-rim sequence of which describes events experienced by an individual crystal from its nucleation to the last moments of its growth. Plagioclase crystals in a typical volcanic rock may look drastically dissimilar despite their spatial proximity and the fact that they have erupted together. Although they shared last moments of their growth during magma ascent and eruption, their prior experiences could be very different, as plagioclase crystals often come from different domains of the same magma system. Distinguishing similar zoning patterns, correlating them across the entire population of plagioclase crystals, and linking these patterns to specific perturbations in the magmatic system may provide additional perspective on the variety, extent, and timing of magma processes at active volcanic systems. Examples of magma processes, which may be distinguished based on plagioclase zoning patterns, include (1) cooling due to heat loss, (2) heating and/or pressure build up due to an input of new magmatic material, (3) pressure drop in response to magma system depressurization, and (4) crystal transfer between different magma domains/bodies. This review will include contrasting examples of zoning patters from recent eruptions of Karymsky, Bezymianny, and Tolbachik Volcanoes in Kamchatka, Augustine and Cleveland Volcanoes in Alaska, as well as from the drilling into an active magma body at Krafla, Iceland.

Urban Thermal Environment Dynamics: A Case Study in Hangzhou During 2005-2015

NASA Astrophysics Data System (ADS)

Sun, W.; Li, F.; Yang, G.

2017-12-01

Hangzhou, as the Capital of Zhejiang Province in East China, has experienced the rapid urbanization process and associated urban heat island effect in the past twenty decades. In this study, we implemented Landsat satellite remote sensing images to investigate the relationship between landscape changes and thermal environment dynamics during 2005-2015 in Hangzhou City. A total of 48 Landsat TM/ETM+/OLR/TIRS images spanning four different seasons were downloaded from the USGS website and utilized in the study. Preprocessing works, i.e., radiometric correction and removing cloud- and fog -contaminated pixels, were conducted, and the land surface temperature (LST) was derived using the radiative transfer equation. Meanwhile, the land use and land cover (LULC) classification was accomplished by using the Support Vector Machine (SVM) classifier, and four main landscape indexes (i.e., Shannon Diversity Index, Landscape Division Index, Shannon Evenness Index, and Aggregation Index) were estimated from the LULC map. Our preliminary results show that: 1) the magnitude of urban thermal environment has obviously increased from 2005 to 2015, and the summer season shows more significant heat island effect than other three seasons; 2) the general landscape pattern of Hangzhou becomes more diversified and fragmentized from 2005 to 2015, and different landscape patterns bring that four different function zones (i.e., urban core zone, tourism function zone, industrial development zone and ecological reservation zone) of Hangzhou have different characteristics in urban thermal environment; 3) significant hot spots of LST point to the construction land while cold spots of LST coincides with the vegetation land.

Histological and Finite Element Analysis of Cell Death due to Irreversible Electroporation

PubMed Central

Long, G.; Bakos, G.; Shires, P. K.; Gritter, L.; Crissman, J. W.; Harris, J. L.; Clymer, J. W.

2014-01-01

Irreversible electroporation (IRE) has been shown to be an effective method of killing cells locally. In contrast to radiofrequency ablation, the mechanism by which cells are thought to die via IRE is the creation of pores in cell membranes, without substantial increase in tissue temperature. To determine the degree to which cell death is non-thermal, we evaluated IRE in porcine hepatocytes in vivo. Using pulse widths of 10μs, bursts of 3 kV square-wave pulses were applied through a custom probe to the liver of an anesthetized pig. Affected tissue was evaluated histologically via stainings of hematoxylin & eosin (H&E), nitroblue tetrazolium (NBT) to monitor cell respiration and TUNEL to gauge apoptosis. Temperature was measured during the application of electroporation, and heat transfer was modeled via finite element analysis. Cell death was calculated via Arrhenius kinetics. Four distinct zones were observed within the ring return electrode; heat-fixed tissue, coagulation, necrotic, and viable. The Arrhenius damage integral estimated complete cell death only in the first zone, where the temperature exceeded 70°C, and partial or no cell death in the other zones, where maximum temperature was approximately 45°C. Except for a limited area near the electrode tip, cell death in IRE is predominantly due to a non-thermal mechanism. PMID:24000980

A new predictive multi-zone model for HCCI engine combustion

DOE PAGES

Bissoli, Mattia; Frassoldati, Alessio; Cuoci, Alberto; ...

2016-06-30

Here, this work introduces a new predictive multi-zone model for the description of combustion in Homogeneous Charge Compression Ignition (HCCI) engines. The model exploits the existing OpenSMOKE++ computational suite to handle detailed kinetic mechanisms, providing reliable predictions of the in-cylinder auto-ignition processes. All the elements with a significant impact on the combustion performances and emissions, like turbulence, heat and mass exchanges, crevices, residual burned gases, thermal and feed stratification are taken into account. Compared to other computational approaches, this model improves the description of mixture stratification phenomena by coupling a wall heat transfer model derived from CFD application with amore » proper turbulence model. Furthermore, the calibration of this multi-zone model requires only three parameters, which can be derived from a non-reactive CFD simulation: these adaptive variables depend only on the engine geometry and remain fixed across a wide range of operating conditions, allowing the prediction of auto-ignition, pressure traces and pollutants. This computational framework enables the use of detail kinetic mechanisms, as well as Rate of Production Analysis (RoPA) and Sensitivity Analysis (SA) to investigate the complex chemistry involved in the auto-ignition and the pollutants formation processes. In the final sections of the paper, these capabilities are demonstrated through the comparison with experimental data.« less

19 CFR 146.67 - Transfer of merchandise for exportation.

Code of Federal Regulations, 2014 CFR

2014-04-01

...; DEPARTMENT OF THE TREASURY (CONTINUED) FOREIGN TRADE ZONES Transfer of Merchandise From a Zone § 146.67 Transfer of merchandise for exportation. (a) Direct exportation. Any merchandise in a zone may be exported... territory for exportation at the port where the zone is located, will be made under an entry for immediate...

19 CFR 146.67 - Transfer of merchandise for exportation.

Code of Federal Regulations, 2013 CFR

2013-04-01

...; DEPARTMENT OF THE TREASURY (CONTINUED) FOREIGN TRADE ZONES Transfer of Merchandise From a Zone § 146.67 Transfer of merchandise for exportation. (a) Direct exportation. Any merchandise in a zone may be exported... territory for exportation at the port where the zone is located, will be made under an entry for immediate...

19 CFR 146.67 - Transfer of merchandise for exportation.

Code of Federal Regulations, 2010 CFR

2010-04-01

...; DEPARTMENT OF THE TREASURY (CONTINUED) FOREIGN TRADE ZONES Transfer of Merchandise From a Zone § 146.67 Transfer of merchandise for exportation. (a) Direct exportation. Any merchandise in a zone may be exported... territory for exportation at the port where the zone is located, will be made under an entry for immediate...

19 CFR 146.67 - Transfer of merchandise for exportation.

Code of Federal Regulations, 2012 CFR

2012-04-01

...; DEPARTMENT OF THE TREASURY (CONTINUED) FOREIGN TRADE ZONES Transfer of Merchandise From a Zone § 146.67 Transfer of merchandise for exportation. (a) Direct exportation. Any merchandise in a zone may be exported... territory for exportation at the port where the zone is located, will be made under an entry for immediate...

19 CFR 146.67 - Transfer of merchandise for exportation.

Code of Federal Regulations, 2011 CFR

2011-04-01

...; DEPARTMENT OF THE TREASURY (CONTINUED) FOREIGN TRADE ZONES Transfer of Merchandise From a Zone § 146.67 Transfer of merchandise for exportation. (a) Direct exportation. Any merchandise in a zone may be exported... territory for exportation at the port where the zone is located, will be made under an entry for immediate...

Modeling macro-and microstructures of Gas-Metal-Arc Welded HSLA-100 steel

NASA Astrophysics Data System (ADS)

Yang, Z.; Debroy, T.

1999-06-01

Fluid flow and heat transfer during gas-metal-arc welding (GMAW) of HSLA-100 steel were studied using a transient, three-dimensional, turbulent heat transfer and fluid flow model. The temperature and velocity fields, cooling rates, and shape and size of the fusion and heat-affected zones (HAZs) were calculated. A continuous-cooling-transformation (CCT) diagram was computed to aid in the understanding of the observed weld metal microstructure. The computed results demonstrate that the dissipation of heat and momentum in the weld pool is significantly aided by turbulence, thus suggesting that previous modeling results based on laminar flow need to be re-examined. A comparison of the calculated fusion and HAZ geometries with their corresponding measured values showed good agreement. Furthermore, “finger” penetration, a unique geometric characteristic of gas-metal-arc weld pools, could be satisfactorily predicted from the model. The ability to predict these geometric variables and the agreement between the calculated and the measured cooling rates indicate the appropriateness of using a turbulence model for accurate calculations. The microstructure of the weld metal consisted mainly of acicular ferrite with small amounts of bainite. At high heat inputs, small amounts of allotriomorphic and Widmanstätten ferrite were also observed. The observed microstructures are consistent with those expected from the computed CCT diagram and the cooling rates. The results presented here demonstrate significant promise for understanding both macro-and microstructures of steel welds from the combination of the fundamental principles from both transport phenomena and phase transformation theory.

Modeling of surface roughness effects on glaze ice accretion

NASA Technical Reports Server (NTRS)

Hansman, R. John, Jr.; Yamaguchi, Keiko; Berkowitz, Brian M.; Potapczuk, Mark

1990-01-01

A series of experimental investigations focused on studying the cause and effect of roughness on accreting glaze ice surfaces were conducted. Detailed microvideo observations were made of glaze ice accretions on 1 to 4 inch diameter cylinders in three icing wind tunnels (the Data Products of New England six inch test facility, the NASA Lewis Icing Research Tunnel, and the B. F. Goodrich Ice Protection Research Facility). Infrared thermal video recordings were made of accreting ice surfaces in the Goodrich facility. Distinct zones of surface water behavior were observed; a smooth wet zone in the stagnation region with a uniform water film; a rough zone where surface tension effects caused coalescence of surface water into stationary beads; a horn zone where roughness elements grow into horn shapes; a runback zone where surface water ran back as rivulets; and a dry zone where rime feathers formed. The location of the transition from the smooth to the rough zone was found to migrate with time towards the stagnation point. The behavior of the transition appeared to be controlled by boundary layer transition and bead formation mechanisms at the interface between the smooth and rough zones. Regions of wet ice growth and enhanced heat transfer were clearly visible in the infrared video recordings of glaze ice surfaces. A simple multi-zone modification to the current glaze ice accretion model was proposed to include spatial variability in surface roughness.

Thrust Slip Rates as a Control on the Presence and Spatial Distribution of High Metamorphic Heating Rates in Collisional Systems: The "Hot Iron" Model Revisited

NASA Astrophysics Data System (ADS)

Thigpen, R.; Ashley, K. T.; Law, R. D.; Mako, C. A.

2017-12-01

In natural systems, two key observations indicate that major strain discontinuities such as faults and shear zones should play a fundamental role in orogenic thermal evolution: (1) Large faults and shear zones often separate components of the composite orogen that have experienced broadly different thermal and deformational histories, and (2) quantitative metamorphic and diffusional studies indicate that heating rates are much faster and the duration of peak conditions much shorter in natural collisional systems than those predicted by numerical continuum deformation models. Because heat transfer processes such as conduction usually operate at much slower time scales than rates of other tectonic processes, thermal evolution is often transient and thus can be strongly influenced by tectonic disturbances that occur at rates much faster than thermal relaxation. Here, we use coupled thermal-mechanical finite element models of thrust faults to explore how fault slip rate may fundamentally influence the thermal evolution of individual footwall and hanging wall thrust slices. The model geometry involves a single crustal-scale thrust with a dip of 25° that is translated up the ramp at average velocities of 20, 35, and 50 km Myr-1, interpreted to represent average to relatively high slip rates observed in many collisional systems. Boundary conditions include crustal radioactive heat production, basal mantle heat flow, and surface erosion rates that are a function of thrust rate and subsequent topography generation. In the models, translation of the hanging wall along the crustal-scale detachment results in erosion, exhumation, and retrograde metamorphism of the emerging hanging wall topography and coeval burial, `hot iron' heating, and prograde metamorphism of the thrust footwall. Thrust slip rates of 20, 35, and 50 km Myr-1 yield maximum footwall heating rates ranging from 55-90° C Myr-1 and maximum hanging wall cooling rates of 138-303° C Myr-1. These relatively rapid heating rates explain, in part, the presence of chemical diffusion profiles in metamorphic minerals that are indicative of high heating rates. Additionally, the relatively high cooling rates explain preservation of chemical zoning, as rapid cooling prevents diffusive profiles from being substantially modified during exhumation.

Late stages of accumulation and early evolution of the planets

NASA Technical Reports Server (NTRS)

Vityazev, Andrey V.; Perchernikova, G. V.

1991-01-01

Recently developed solutions of problems are discussed that were traditionally considered fundamental in classical solar system cosmogony: determination of planetary orbit distribution patterns, values for mean eccentricity and orbital inclinations of the planets, and rotation periods and rotation axis inclinations of the planets. Two important cosmochemical aspects of accumulation are examined: the time scale for gas loss from the terrestrial planet zone, and the composition of the planets in terms of isotope data. It was concluded that the early beginning of planet differentiation is a function of the heating of protoplanets during collisions with large (thousands of kilometers) bodies. Energetics, heat mass transfer processes, and characteristic time scales of these processes at the early stages of planet evolution are considered.

Numerical optimization of a multi-jet cooling system for the blown film extrusion

NASA Astrophysics Data System (ADS)

Janas, M.; Wortberg, J.

2015-05-01

The limiting factor for every extrusion process is the cooling. For the blown film process, this task is usually done by means of a single or dual lip air ring. Prior work has shown that two major effects are responsible for a bad heat transfer. The first one is the interaction between the jet and the ambient air. It reduces the velocity of the jet and enlarges the straight flow. The other one is the formation of a laminar boundary layer on the film surface due to the fast flowing cooling air. In this case, the boundary layer isolates the film and prevents an efficient heat transfer. To improve the heat exchange, a novel cooling approach is developed, called Multi-Jet. The new cooling system uses several slit nozzles over the whole tube formation zone for cooling the film. In contrast to a conventional system, the cooling air is guided vertically on the film surface in different heights to penetrate the boundary sublayer. Simultaneously, a housing of the tube formation zone is practically obtained to reduce the interaction with the ambient air. For the numerical optimization of the Multi-Jet system, a new procedure is developed. First, a prediction model identifies a worth considering cooling configuration. Therefore, the prediction model computes a film curve using the formulation from Zatloukal-Vlcek and the energy balance for the film temperature. Thereafter, the optimized cooling geometry is investigated in detail using a process model for the blown film extrusion that is able to compute a realistic bubble behavior depending on the cooling situation. In this paper, the Multi-Jet cooling system is numerically optimized for several different process states, like mass throughputs and blow-up ratios using one slit nozzle setting. For each process condition, the best cooling result has to be achieved. Therefore, the height of any nozzle over the tube formation zone is adjustable. The other geometrical parameters of the cooling system like the nozzle diameter or the nozzle width are fix.

Shallow Chamber & Conduit Behavior of Silicic Magma: A Thermo- and Fluid- Dynamic Parameterization Model of Physical Deformation as Constrained by Geodetic Observations: Case Study; Soufriere Hills Volcano, Montserrat

NASA Astrophysics Data System (ADS)

Gunn de Rosas, C. L.

2013-12-01

The Soufrière Hills Volcano, Montserrat (SHV) is an active, mainly andesitic and well-studied stratovolcano situated at the northern end of the Lesser Antilles Arc subduction zone in the Caribbean Sea. The goal of our research is to create a high resolution 3D subsurface model of the shallow and deeper aspects of the magma storage and plumbing system at SHV. Our model will integrate inversions using continuous and campaign geodetic observations at SHV from 1995 to the present as well as local seismic records taken at various unrest intervals to construct a best-fit geometry, pressure point source and inflation rate and magnitude. We will also incorporate a heterogeneous media in the crust and use the most contemporary understanding of deep crustal- or even mantle-depth 'hot-zone' genesis and chemical evolution of silicic and intermediate magmas to inform the character of the deep edifice influx. Our heat transfer model will be constructed with a modified 'thin shell' enveloping the magma chamber to simulate the insulating or conducting influence of heat-altered chamber boundary conditions. The final forward model should elucidate observational data preceding and proceeding unrest events, the behavioral suite of magma transport in the subsurface environment and the feedback mechanisms that may contribute to eruption triggering. Preliminary hypotheses suggest wet, low-viscosity residual melts derived from 'hot zones' will ascend rapidly to shallower stall-points and that their products (eventually erupted lavas as well as stalled plutonic masses) will experience and display two discrete periods of shallow evolution; a rapid depressurization crystallization event followed by a slower conduction-controlled heat transfer and cooling crystallization. These events have particular implications for shallow magma behaviors, notably inflation, compressibility and pressure values. Visualization of the model with its inversion constraints will be affected with ComSol. Conclusions about the subsurface behavioral suite at SHV will have high applicability to other silicic and intermediate volcanic edifices and may aid in the hazard mitigation associated with volcanic unrest.

The effect of optical system design for laser micro-hole drilling process

NASA Astrophysics Data System (ADS)

Ding, Chien-Fang; Lan, Yin-Te; Chien, Yu-Lun; Young, Hong-Tsu

2017-08-01

Lasers are a promising high accuracy tool to make small holes in composite or hard material. They offer advantages over the conventional machining process, which is time consuming and has scaling limitations. However, the major downfall in laser material processing is the relatively large heat affect zone or number of molten burrs it generates, even when using nanosecond lasers over high-cost ultrafast lasers. In this paper, we constructed a nanosecond laser processing system with a 532 nm wavelength laser source. In order to enhance precision and minimize the effect of heat generation with the laser drilling process, we investigated the geometric shape of optical elements and analyzed the images using the modulation transfer function (MTF) and encircled energy (EE) by using optical software Zemax. We discuss commercial spherical lenses, including plano-convex lenses, bi-convex lenses, plano-concave lenses, bi-concave lenses, best-form lenses, and meniscus lenses. Furthermore, we determined the best lens configuration by image evaluation, and then verified the results experimentally by carrying out the laser drilling process on multilayer flexible copper clad laminate (FCCL). The paper presents the drilling results obtained with different lens configurations and found the best configuration had a small heat affect zone and a clean edge along laser-drilled holes.

Thermochemical hydrogen production based on magnetic fusion

NASA Astrophysics Data System (ADS)

Krikorian, O. H.; Brown, L. C.

Preliminary results of a DoE study to define the configuration and production costs for a Tandem Mirror Reactor (TMR) heat source H2 fuel production plant are presented. The TMR uses the D-T reaction to produce thermal energy and dc electrical current, with an Li blanket employed to breed more H-3 for fuel. Various blanket designs are being considered, and the coupling of two of them, a heat pipe blanket to a Joule-boosted decomposer, and a two-temperature zone blanket to a fluidized bed decomposer, are discussed. The thermal energy would be used in an H2SO4 thermochemical cycler to produce the H2. The Joule-boosted decomposer, involving the use of electrically heated commercial SiC furnace elements to transfer process heat to the thermochemical H2 cycle, is found to yield H2 fuel at a cost of $12-14/GJ, which is the projected cost of fossil fuels in 30-40 yr, when the TMR H2 production facility would be operable.

An experimental and numerical study of endwall heat transfer in a turbine blade cascade including tangential heat conduction analysis

NASA Astrophysics Data System (ADS)

Ratto, Luca; Satta, Francesca; Tanda, Giovanni

2018-06-01

This paper presents an experimental and numerical investigation of heat transfer in the endwall region of a large scale turbine cascade. The steady-state liquid crystal technique has been used to obtain the map of the heat transfer coefficient for a constant heat flux boundary condition. In the presence of two- and three-dimensional flows with significant spatial variations of the heat transfer coefficient, tangential heat conduction could lead to error in the heat transfer coefficient determination, since local heat fluxes at the wall-to-fluid interface tend to differ from point to point and surface temperatures to be smoothed out, thus making the uniform-heat-flux boundary condition difficult to be perfectly achieved. For this reason, numerical simulations of flow and heat transfer in the cascade including the effect of tangential heat conduction inside the endwall have been performed. The major objective of numerical simulations was to investigate the influence of wall heat conduction on the convective heat transfer coefficient determined during a nominal iso-flux heat transfer experiment and to interpret possible differences between numerical and experimental heat transfer results. Results were presented and discussed in terms of local Nusselt number and a convenient wall heat flux function for two values of the Reynolds number (270,000 and 960,000).

Effect of Anode Change on Heat Transfer and Magneto-hydrodynamic Flow in Aluminum Reduction Cell

NASA Astrophysics Data System (ADS)

Wang, Qiang; Li, Baokuan; Fafard, Mario

2016-02-01

In order to explore the impact of anode replacement on heat transfer and magneto-hydrodynamic flow in aluminum smelting cells, a transient three-dimensional coupled mathematical model has been developed. With a steady state magnetic field, an electrical potential approach was used to obtain electromagnetic fields. Joule heating and Lorentz force, which were the source terms in the energy and momentum equations, were updated at each iteration. The phase change of molten electrolyte (bath) was modeled by an enthalpy-based technique in which the mushy zone was treated as a porous medium with porosity equal to the liquid fraction. A reasonable agreement between the test data and simulated results was achieved. Under normal conditions, the bath at the middle of the cell is hotter, while becoming colder at the four corners. Due to the heat extracted from the bath, the temperature of the new cold anode increases over time. The temperature of the bath under the new cold anode therefore quickly drops, resulting in a decrease of the electrical conductivity. More Joule effect is created. In addition, the bath under the new cold anode gradually freezes and flows more slowly. The temperature of the new anode located at the middle of the cell rises faster because of the warmer bath. It is easier to eliminate the effect of anode change when it occurs in the middle of the cell.

Numerical simulation of transient temperature profiles for canned apple puree in semi-rigid aluminum based packaging during pasteurization.

PubMed

Shafiekhani, Soraya; Zamindar, Nafiseh; Hojatoleslami, Mohammad; Toghraie, Davood

2016-06-01

Pasteurization of canned apple puree was simulated for a 3-D geometry in a semi-rigid aluminum based container which was heated from all sides at 378 K. The computational fluid dynamics code Ansys Fluent 14.0 was used and the governing equations for energy, momentum, and continuity were computed using a finite volume method. The food model was assumed to have temperature-dependent properties. To validate the simulation, the apple puree was pasteurized in a water cascading retort. The effect of the mesh structures was studied for the temperature profiles during thermal processing. The experimental temperature in the slowest heating zone in the container was compared with the temperature predicted by the model and the difference was not significant. The study also investigated the impact of head space (water-vapor) on heat transfer.

Evaluating the SCC resistance of underwater welds in sodium tetrathionate

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

White, R.A.; Angeliu, T.M.

1997-12-01

The susceptibility of welds to stress corrosion cracking (SCC) is enhanced by the surface residual tensile stresses generated by the typical welding process. However, underwater plasma transferred arc (PTA) welding has been shown to produce compressive surface residual stresses, an encouraging result if repairs of cracked boiling water reactor (BWR) components are to be made without further endangering them to SCC. This program was designed to verify that underwater PTA welds are resistant to SCC and to determine if underwater PTA welding could mitigate SCC in potentially susceptible welds. This was achieved by exposing various welds on solution annealed (SA)more » and SA + thermally sensitized 304 stainless steel at 25 C in a solution of 1.5 gm/liter of sodium sulfide added to 0.05M sodium tetrathionate, titrated to a pH of 1.25 with H{sub 2}SO{sub 4}. The autogeneous welds were produced using gas tungsten arc (GTA) and plasma transferred arc (PTA) welding under atmospheric conditions, and PTA welding underwater. After 1 hour of sodium tetrathionate exposure, GTA and air PTA welds exhibited SCC while the underwater PTA weld heat affected zones were more resistant. Underwater PTA welds bisecting a GTA weld eliminated the cracking in the GTA weld heat affected zone under certain conditions. The lack of IG cracking in the region influenced by the underwater PTA weld is consistent with the measurement of compressive surface residual stresses inherent to the underwater welding process.« less

Heat transfer and pressure drop characteristics of a plate heat exchanger using water based Al2O3 nanofluid for 30° and 60° chevron angles

NASA Astrophysics Data System (ADS)

Elias, M. M.; Saidur, R.; Ben-Mansour, R.; Hepbasli, A.; Rahim, N. A.; Jesbains, K.

2018-04-01

Nanofluid is a new class of engineering fluid that has good heat transfer characteristics which is essential to increase the heat transfer performance in various engineering applications such as heat exchangers and cooling of electronics. In this study, experiments were conducted to compare the heat transfer performance and pressure drop characteristics in a plate heat exchanger (PHE) for 30° and 60° chevron angles using water based Al2O3 nanofluid at the concentrations from 0 to 0.5 vol.% for different Reynolds numbers. The thermo-physical properties has been determined and presented in this paper. At 0.5 vol% concentration, the maximum heat transfer coefficient, the overall heat transfer coefficient and the heat transfer rate for 60° chevron angle have attained a higher percentage of 15.14%, 7.8% and 15.4%, respectively in comparison with the base fluid. Consequently, when the volume concentration or Reynolds number increases, the heat transfer coefficient and the overall heat transfer coefficient as well as the heat transfer rate of the PHE (Plate Heat Exchangers) increases respectively. Similarly, the pressure drop increases with the volume concentration. 60° chevron angle showed better performance in comparison with 30° chevron angle.

Europa, tidally heated oceans, and habitable zones around giant planets.

PubMed

Reynolds, R T; McKay, C P; Kasting, J F

1987-01-01

Tidal dissipation in the satellites of a giant planet may provide sufficient heating to maintain an environment favorable to life on the satellite surface or just below a thin ice layer. In our own solar system, Europa, one of the Galilean satellites of Jupiter, could have a liquid ocean which may occasionally receive sunlight through cracks in the overlying ice shell. In such case, sufficient solar energy could reach liquid water that organisms similar to those found under Antarctic ice could grow. In other solar systems, larger satellites with more significant heat flow could represent environments that are stable over an order of Aeons and in which life could perhaps evolve. We define a zone around a giant planet in which such satellites could exist as a tidally-heated habitable zone. This zone can be compared to the habitable zone which results from heating due to the radiation of a central star. In our solar system, this radiatively-heated habitable zone contains the Earth.

The dynamics of Al/Pt reactive multilayer ignition via pulsed-laser irradiation

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

Murphy, Ryan D.; Reeves, Robert V.; Yarrington, Cole D.

2015-12-07

Reactive multilayers consisting of alternating layers of Al and Pt were irradiated by single laser pulses ranging from 100 μs to 100 ms in duration, resulting in the initiation of rapid, self-propagating reactions. The threshold intensities for ignition vary with the focused laser beam diameter, bilayer thickness, and pulse length and are affected by solid state reactions and conduction of heat away from the irradiated regions. High-speed photography was used to observe ignition dynamics during irradiation and elucidate the effects of heat transfer into a multilayer foil. For an increasing laser pulse length, the ignition process transitioned from a more uniform tomore » a less uniform temperature profile within the laser-heated zone. A more uniform temperature profile is attributed to rapid heating rates and heat localization for shorter laser pulses, and a less uniform temperature profile is due to slower heating of reactants and conduction during irradiation by longer laser pulses. Finite element simulations of laser heating using measured threshold intensities indicate that micron-scale ignition of Al/Pt occurs at low temperatures, below the melting point of both reactants.« less

The dynamics of Al/Pt reactive multilayer ignition via pulsed-laser irradiation

DOE PAGES

Murphy, Ryan D.; Reeves, Robert V.; Yarrington, Cole D.; ...

2015-12-07

Reactive multilayers consisting of alternating layers of Al and Pt were irradiated by single laser pulses ranging from 100 μs to 100 ms in duration, resulting in the initiation of rapid, self-propagating reactions. The threshold intensities for ignition vary with the focused laser beam diameter, bilayer thickness, and pulse length and are affected by solid state reactions and conduction of heat away from the irradiated regions. We used high-speed photography to observe ignition dynamics during irradiation and elucidate the effects of heat transfer into a multilayer foil. For an increasing laser pulse length, the ignition process transitioned from a moremore » uniform to a less uniform temperature profile within the laser-heated zone. A more uniform temperature profile is attributed to rapid heating rates and heat localization for shorter laser pulses, and a less uniform temperature profile is due to slower heating of reactants and conduction during irradiation by longer laser pulses. Lastly, finite element simulations of laser heating using measured threshold intensities indicate that micron-scale ignition of Al/Pt occurs at low temperatures, below the melting point of both reactants.« less

Fluid dynamics and convective heat transfer in impinging jets through implementation of a high resolution liquid crystal technique

NASA Technical Reports Server (NTRS)

Kim, K.; Wiedner, B.; Camci, C.

1993-01-01

A combined convective heat transfer and fluid dynamics investigation in a turbulent round jet impinging on a flat surface is presented. The experimental study uses a high resolution liquid crystal technique for the determination of the convective heat transfer coefficients on the impingement plate. The heat transfer experiments are performed using a transient heat transfer method. The mean flow and the character of turbulent flow in the free jet is presented through five hole probe and hot wire measurements, respectively. The flow field character of the region near the impingement plate plays an important role in the amount of convective heat transfer. Detailed surveys obtained from five hole probe and hot wire measurements are provided. An extensive validation of the liquid crystal based heat transfer method against a conventional technique is also presented. After a complete documentation of the mean and turbulent flow field, the convective heat transfer coefficient distributions on the impingement plate are presented. The near wall of the impingement plate and the free jet region is treated separately. The current heat transfer distributions are compared to other studies available from the literature. The present paper contains complete sets of information on the three dimensional mean flow, turbulent velocity fluctuations, and convective heat transfer to the plate. The experiments also prove that the present nonintrusive heat transfer method is highly effective in obtaining high resolution heat transfer maps with a heat transfer coefficient uncertainty of 5.7 percent.

Validation Results for Core-Scale Oil Shale Pyrolysis

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

Staten, Josh; Tiwari, Pankaj

2015-03-01

This report summarizes a study of oil shale pyrolysis at various scales and the subsequent development a model for in situ production of oil from oil shale. Oil shale from the Mahogany zone of the Green River formation was used in all experiments. Pyrolysis experiments were conducted at four scales, powdered samples (100 mesh) and core samples of 0.75”, 1” and 2.5” diameters. The batch, semibatch and continuous flow pyrolysis experiments were designed to study the effect of temperature (300°C to 500°C), heating rate (1°C/min to 10°C/min), pressure (ambient and 500 psig) and size of the sample on product formation.more » Comprehensive analyses were performed on reactants and products - liquid, gas and spent shale. These experimental studies were designed to understand the relevant coupled phenomena (reaction kinetics, heat transfer, mass transfer, thermodynamics) at multiple scales. A model for oil shale pyrolysis was developed in the COMSOL multiphysics platform. A general kinetic model was integrated with important physical and chemical phenomena that occur during pyrolysis. The secondary reactions of coking and cracking in the product phase were addressed. The multiscale experimental data generated and the models developed provide an understanding of the simultaneous effects of chemical kinetics, and heat and mass transfer on oil quality and yield. The comprehensive data collected in this study will help advance the move to large-scale in situ oil production from the pyrolysis of oil shale.« less

Fluid-cooled heat sink with improved fin areas and efficiencies for use in cooling various devices

DOEpatents

Bharathan, Desikan; Bennion, Kevin; Kelly, Kenneth; Narumanchi, Sreekant

2015-04-21

The disclosure provides a fluid-cooled heat sink having a heat transfer base and a plurality of heat transfer fins in thermal communication with the heat transfer base, where the heat transfer base and the heat transfer fins form a central fluid channel through which a forced or free cooling fluid may flow. The heat transfer pins are arranged around the central fluid channel with a flow space provided between adjacent pins, allowing for some portion of the central fluid channel flow to divert through the flow space. The arrangement reduces the pressure drop of the flow through the fins, optimizes average heat transfer coefficients, reduces contact and fin-pin resistances, and reduces the physical footprint of the heat sink in an operating environment.

Analysis of Free-Flight Laminar, Transitional, and Turbulent Heat-Transfer Results at Free-Stream Mach Numbers Near 20 (Reentry F)

NASA Technical Reports Server (NTRS)

Zoby, Ernest V.; Rumsey, Charles B.

1971-01-01

Laminar, transitional, and turbulent heat-transfer data were measured during a reentry flight at a Mach number of 20 on a 5 deg half-angle cone 3.962 m (13 ft) long with an initial nose tip radius of 0.254 cm (0.1 in.). The free-stream Reynolds number increased during the prime data period from 7.0 x 10(exp 6) to 51.5 x 10(exp 6) per meter (2.1 x 10(exp 6) to 15.7 x 10(exp 6) per foot) and the ratio of wall to total temperature varied from 0.053 to 0.12. The angle of attack was less than 1deg for the prime data period. The experimental laminar and turbulent heating rates are compared with results from existing flat-plate prediction methods. At conditions of minimal tip blunting and angle of attack (above 26.8 km (88 000 ft)), values from a flat-plate laminar method agreed within 20 percent with the laminar data. The Schultz-Grunow skin-friction equation with reference enthalpy; conditions, with the Reynolds number based on distance from the transition location, and with the Colburn Reynolds analogy agreed within 10 percent with the experimental turbuleiit heating data. The Van Driest n skin-friction equation with Reynolds number greater than 10(exp 7) based on distance from the peak heating point and the Colburn Reynolds analogy was also within approximately 10 percent of the experimental turbulent heating data. A data correlation jbf the extent of transition and a simple empirical transition-zone heating correlation were also presented.

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.

Solar Flux Deposition And Heating Rates In Jupiter's Atmosphere

NASA Astrophysics Data System (ADS)

Perez-Hoyos, Santiago; Sánchez-Lavega, A.

2009-09-01

We discuss here the solar downward net flux in the 0.25 - 2.5 µm range in the atmosphere of Jupiter and the associated heating rates under a number of vertical cloud structure scenarios focusing in the effect of clouds and hazes. Our numerical model is based in the doubling-adding technique to solve the radiative transfer equation and it includes gas absorption by CH4, NH3 and H2, in addition to Rayleigh scattering by a mixture of H2 plus He. Four paradigmatic Jovian regions have been considered (hot-spots, belts, zones and Polar Regions). The hot-spots are the most transparent regions with downward net fluxes of 2.5±0.5 Wm-2 at the 6 bar level. The maximum solar heating is 0.04±0.01 K/day and occurs above 1 bar. Belts and zones characterization result in a maximum net downward flux of 0.5 Wm-2 at 2 bar and 0.015 Wm-2 at 6 bar. Heating is concentrated in the stratospheric and tropospheric hazes. Finally, Polar Regions are also explored and the results point to a considerable stratospheric heating of 0.04±0.02 K/day. In all, these calculations suggest that the role of the direct solar forcing in the Jovian atmospheric dynamics is limited to the upper 1 - 2 bar of the atmosphere except in the hot-spot areas. Acknowledgments: This work has been funded by Spanish MEC AYA2006-07735 with FEDER support and Grupos Gobierno Vasco IT-464-07.

Heat transfer system

DOEpatents

Not Available

1980-03-07

A heat transfer system for a nuclear reactor is described. Heat transfer is accomplished within a sealed vapor chamber which is substantially evacuated prior to use. A heat transfer medium, which is liquid at the design operating temperatures, transfers heat from tubes interposed in the reactor primary loop to spaced tubes connected to a steam line for power generation purposes. Heat transfer is accomplished by a two-phase liquid-vapor-liquid process as used in heat pipes. Condensible gases are removed from the vapor chamber through a vertical extension in open communication with the chamber interior.

Heat transfer system

DOEpatents

McGuire, Joseph C.

1982-01-01

A heat transfer system for a nuclear reactor. Heat transfer is accomplished within a sealed vapor chamber which is substantially evacuated prior to use. A heat transfer medium, which is liquid at the design operating temperatures, transfers heat from tubes interposed in the reactor primary loop to spaced tubes connected to a steam line for power generation purposes. Heat transfer is accomplished by a two-phase liquid-vapor-liquid process as used in heat pipes. Condensible gases are removed from the vapor chamber through a vertical extension in open communication with the chamber interior.

Vertical feed stick wood fuel burning furnace system

DOEpatents

Hill, Richard C.

1982-01-01

A stove or furnace for efficient combustion of wood fuel includes a vertical feed combustion chamber (15) for receiving and supporting wood fuel in a vertical attitude or stack. A major upper portion of the combustion chamber column comprises a water jacket (14) for coupling to a source of water or heat transfer fluid for convection circulation of the fluid. The locus (31) of wood fuel combustion is thereby confined to the refractory base of the combustion chamber. A flue gas propagation delay channel (34) extending laterally from the base of the chamber affords delayed travel time in a high temperature refractory environment sufficient to assure substantially complete combustion of the gaseous products of wood burning with forced air prior to extraction of heat in heat exchanger (16). Induced draft draws the fuel gas and air mixture laterally through the combustion chamber and refractory high temperature zone to the heat exchanger and flue. Also included are active sources of forced air and induced draft, multiple circuit couplings for the recovered heat, and construction features in the refractory material substructure and metal component superstructure.

46 CFR 153.436 - Heat transfer fluids: compatibility with cargo.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 5 2012-10-01 2012-10-01 false Heat transfer fluids: compatibility with cargo. 153.436... Equipment Cargo Temperature Control Systems § 153.436 Heat transfer fluids: compatibility with cargo. A heat transfer fluid separated from the cargo by only one wall (for example, the heat transfer fluid in a coil...

46 CFR 153.436 - Heat transfer fluids: compatibility with cargo.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 5 2014-10-01 2014-10-01 false Heat transfer fluids: compatibility with cargo. 153.436... Equipment Cargo Temperature Control Systems § 153.436 Heat transfer fluids: compatibility with cargo. A heat transfer fluid separated from the cargo by only one wall (for example, the heat transfer fluid in a coil...

46 CFR 153.436 - Heat transfer fluids: compatibility with cargo.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 5 2013-10-01 2013-10-01 false Heat transfer fluids: compatibility with cargo. 153.436... Equipment Cargo Temperature Control Systems § 153.436 Heat transfer fluids: compatibility with cargo. A heat transfer fluid separated from the cargo by only one wall (for example, the heat transfer fluid in a coil...

46 CFR 153.436 - Heat transfer fluids: compatibility with cargo.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 5 2011-10-01 2011-10-01 false Heat transfer fluids: compatibility with cargo. 153.436... Equipment Cargo Temperature Control Systems § 153.436 Heat transfer fluids: compatibility with cargo. A heat transfer fluid separated from the cargo by only one wall (for example, the heat transfer fluid in a coil...

46 CFR 153.436 - Heat transfer fluids: compatibility with cargo.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 5 2010-10-01 2010-10-01 false Heat transfer fluids: compatibility with cargo. 153.436... Equipment Cargo Temperature Control Systems § 153.436 Heat transfer fluids: compatibility with cargo. A heat transfer fluid separated from the cargo by only one wall (for example, the heat transfer fluid in a coil...

Review of thermo-physical properties, wetting and heat transfer characteristics of nanofluids and their applicability in industrial quench heat treatment

PubMed Central

2011-01-01

The success of quenching process during industrial heat treatment mainly depends on the heat transfer characteristics of the quenching medium. In the case of quenching, the scope for redesigning the system or operational parameters for enhancing the heat transfer is very much limited and the emphasis should be on designing quench media with enhanced heat transfer characteristics. Recent studies on nanofluids have shown that these fluids offer improved wetting and heat transfer characteristics. Further water-based nanofluids are environment friendly as compared to mineral oil quench media. These potential advantages have led to the development of nanofluid-based quench media for heat treatment practices. In this article, thermo-physical properties, wetting and boiling heat transfer characteristics of nanofluids are reviewed and discussed. The unique thermal and heat transfer characteristics of nanofluids would be extremely useful for exploiting them as quench media for industrial heat treatment. PMID:21711877

Review of thermo-physical properties, wetting and heat transfer characteristics of nanofluids and their applicability in industrial quench heat treatment.

PubMed

Ramesh, Gopalan; Prabhu, Narayan Kotekar

2011-04-14

The success of quenching process during industrial heat treatment mainly depends on the heat transfer characteristics of the quenching medium. In the case of quenching, the scope for redesigning the system or operational parameters for enhancing the heat transfer is very much limited and the emphasis should be on designing quench media with enhanced heat transfer characteristics. Recent studies on nanofluids have shown that these fluids offer improved wetting and heat transfer characteristics. Further water-based nanofluids are environment friendly as compared to mineral oil quench media. These potential advantages have led to the development of nanofluid-based quench media for heat treatment practices. In this article, thermo-physical properties, wetting and boiling heat transfer characteristics of nanofluids are reviewed and discussed. The unique thermal and heat transfer characteristics of nanofluids would be extremely useful for exploiting them as quench media for industrial heat treatment.

The deep structure of a sea-floor hydrothermal deposit

USGS Publications Warehouse

Zierenberg, R.A.; Fouquet, Y.; Miller, D.J.; Bahr, J.M.; Baker, P.A.; Bjerkgard, T.; Brunner, C.A.; Duckworth, R.C.; Gable, R.; Gieskes, J.; Goodfellow, W.D.; Groschel-Becker, H. M.; Guerin, G.; Ishibashi, J.; Iturrino, G.; James, R.H.; Lackschewitz, K.S.; Marquez, L.L.; Nehlig, P.; Peter, J.M.; Rigsby, C.A.; Schultheiss, P.; Shanks, Wayne C.; Simoneit, B.R.T.; Summit, M.; Teagle, D.A.H.; Urbat, M.; Zuffa, G.G.

1998-01-01

Hydrothermal circulation at the crests of mid-ocean ridges plays an important role in transferring heat from the interior of the Earth. A consequence of this hydrothermal circulation is the formation of metallic ore bodies known as volcanic-associated massive sulphide deposits. Such deposits, preserved on land, were important sources of copper for ancient civilizations and continue to provide a significant source of base metals (for example, copper and zinc). Here we present results from Ocean Drilling Program Leg 169, which drilled through a massive sulphide deposit on the northern Juan de Fuca spreading centre and penetrated the hydrothermal feeder zone through which the metal-rich fluids reached the sea floor. We found that the style of feeder-zone mineralization changes with depth in response to changes in the pore pressure of the hydrothermal fluids and discovered a stratified zone of high-grade copper-rich replacement mineralization below the massive sulphide deposit. This copper-rich zone represents a type of mineralization not previously observed below sea-floor deposits, and may provide new targets for land-based mineral exploration.

FAST TRACK COMMUNICATION Heat transfer between graphene and amorphous SiO2

NASA Astrophysics Data System (ADS)

Persson, B. N. J.; Ueba, H.

2010-11-01

We study the heat transfer between graphene and amorphous SiO2. We include both the heat transfer from the area of real contact, and between the surfaces in the non-contact region. We consider the radiative heat transfer associated with the evanescent electromagnetic waves which exist outside of all bodies, and the heat transfer by the gas in the non-contact region. We find that the dominant contribution to the heat transfer results from the area of real contact, and the calculated value of the heat transfer coefficient is in good agreement with the value deduced from experimental data.

Fluid-cooled heat sink for use in cooling various devices

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

Bharathan, Desikan; Bennion, Kevin; Kelly, Kenneth

The disclosure provides a fluid-cooled heat sink having a heat transfer base, a shroud, and a plurality of heat transfer fins in thermal communication with the heat transfer base and the shroud, where the heat transfer base, heat transfer fins, and the shroud form a central fluid channel through which a forced or free cooling fluid may flow. The heat transfer pins are arranged around the central fluid channel with a flow space provided between adjacent pins, allowing for some portion of the central fluid channel flow to divert through the flow space. The arrangement reduces the pressure drop ofmore » the flow through the fins, optimizes average heat transfer coefficients, reduces contact and fin-pin resistances, and reduces the physical footprint of the heat sink in an operating environment.« less

Calibrated heat flow model for the determination of different heat-affected zones in single-pass laser-cut CFRP using a cw CO2 laser

NASA Astrophysics Data System (ADS)

Mucha, P.; Berger, P.; Weber, R.; Speker, N.; Sommer, B.; Graf, T.

2015-03-01

Laser machining has great potential for automated manufacturing of parts made of carbon-fiber-reinforced plastic (CFRP) due to the nearly force and tool-wear free processing. The high vaporization temperatures and the large heat conductivity of the carbon fibers, however, lead to unintentional heat conduction into the material causing damage in zones close to the process. In this paper, the matrix damage zone (MDZ) is subdivided into a matrix sublimation zone (MSZ) where the matrix material was sublimated and a zone where the temperature temporarily exceeded a value causing structural damage in the matrix. In order to investigate the extent of these zones, a one-dimensional heat flow model was applied, which was calibrated by cutting experiments using temperature sensors embedded in the CFRP samples. The investigations showed that the extents of the MSZ and MDZ are dominated by a total interaction time, which includes the passage of the laser beam and the continued interaction of the cloud of hot ablation products with the carbon fibers at the kerf wall and that from a practical point of view, the experimentally determined effective heat conductivity is suitable for simple estimations of the heat-affected zones in CFRP.

Beyond the classic thermoneutral zone

PubMed Central

Kingma, Boris RM; Frijns, Arjan JH; Schellen, Lisje; van Marken Lichtenbelt, Wouter D

2014-01-01

The thermoneutral zone is defined as the range of ambient temperatures where the body can maintain its core temperature solely through regulating dry heat loss, i.e., skin blood flow. A living body can only maintain its core temperature when heat production and heat loss are balanced. That means that heat transport from body core to skin must equal heat transport from skin to the environment. This study focuses on what combinations of core and skin temperature satisfy the biophysical requirements of being in the thermoneutral zone for humans. Moreover, consequences are considered of changes in insulation and adding restrictions such as thermal comfort (i.e. driver for thermal behavior). A biophysical model was developed that calculates heat transport within a body, taking into account metabolic heat production, tissue insulation, and heat distribution by blood flow and equates that to heat loss to the environment, considering skin temperature, ambient temperature and other physical parameters. The biophysical analysis shows that the steady-state ambient temperature range associated with the thermoneutral zone does not guarantee that the body is in thermal balance at basal metabolic rate per se. Instead, depending on the combination of core temperature, mean skin temperature and ambient temperature, the body may require significant increases in heat production or heat loss to maintain stable core temperature. Therefore, the definition of the thermoneutral zone might need to be reformulated. Furthermore, after adding restrictions on skin temperature for thermal comfort, the ambient temperature range associated with thermal comfort is smaller than the thermoneutral zone. This, assuming animals seek thermal comfort, suggests that thermal behavior may be initiated already before the boundaries of the thermoneutral zone are reached. PMID:27583296

Beyond the classic thermoneutral zone: Including thermal comfort.

PubMed

Kingma, Boris Rm; Frijns, Arjan Jh; Schellen, Lisje; van Marken Lichtenbelt, Wouter D

2014-01-01

The thermoneutral zone is defined as the range of ambient temperatures where the body can maintain its core temperature solely through regulating dry heat loss, i.e., skin blood flow. A living body can only maintain its core temperature when heat production and heat loss are balanced. That means that heat transport from body core to skin must equal heat transport from skin to the environment. This study focuses on what combinations of core and skin temperature satisfy the biophysical requirements of being in the thermoneutral zone for humans. Moreover, consequences are considered of changes in insulation and adding restrictions such as thermal comfort (i.e. driver for thermal behavior). A biophysical model was developed that calculates heat transport within a body, taking into account metabolic heat production, tissue insulation, and heat distribution by blood flow and equates that to heat loss to the environment, considering skin temperature, ambient temperature and other physical parameters. The biophysical analysis shows that the steady-state ambient temperature range associated with the thermoneutral zone does not guarantee that the body is in thermal balance at basal metabolic rate per se. Instead, depending on the combination of core temperature, mean skin temperature and ambient temperature, the body may require significant increases in heat production or heat loss to maintain stable core temperature. Therefore, the definition of the thermoneutral zone might need to be reformulated. Furthermore, after adding restrictions on skin temperature for thermal comfort, the ambient temperature range associated with thermal comfort is smaller than the thermoneutral zone. This, assuming animals seek thermal comfort, suggests that thermal behavior may be initiated already before the boundaries of the thermoneutral zone are reached.

Experimental investigation of forced convective heat transfer performance in nanofluids of Al2O3/water and CuO/water in a serpentine shaped micro channel heat sink

NASA Astrophysics Data System (ADS)

Sivakumar, A.; Alagumurthi, N.; Senthilvelan, T.

2016-07-01

The microchannels are device used to remove high heat fluxes from smaller area. In this experimental research work the heat transfer performance of nanofluids of Al2O3/water and CuO/water were compared. The important character of such fluids is the enhanced thermal conductivity, in comparison with base fluid without considerable alteration in physical and chemical properties. The effect of forced convective heat transfer coefficient was calculated using serpentine shaped microchannel heat exchanger. Furthermore we calculated the forced convective heat transfer coefficient of the nanofluids using theoretical correlations in order to compare the results with the experimental data. The heat transfer coefficient for different particle concentration and temperature were analysed using forced convection heat transfer using nanofluids. The findings indicate considerable enhancement in convective heat transfer coefficient of the nanofluids as compared to the basefluid. The results also shows that CuO/water nanofluid has increased heat transfer coefficient compared with Al2O3/water and base fluids. Moreover the experimental results indicate there is increased forced convective heat transfer coefficient with the increase in nano particle concentration.

Secondary Heat Exchanger Design and Comparison for Advanced High Temperature Reactor

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

Piyush Sabharwall; Ali Siahpush; Michael McKellar

2012-06-01

The goals of next generation nuclear reactors, such as the high temperature gas-cooled reactor and advance high temperature reactor (AHTR), are to increase energy efficiency in the production of electricity and provide high temperature heat for industrial processes. The efficient transfer of energy for industrial applications depends on the ability to incorporate effective heat exchangers between the nuclear heat transport system and the industrial process heat transport system. The need for efficiency, compactness, and safety challenge the boundaries of existing heat exchanger technology, giving rise to the following study. Various studies have been performed in attempts to update the secondarymore » heat exchanger that is downstream of the primary heat exchanger, mostly because its performance is strongly tied to the ability to employ more efficient conversion cycles, such as the Rankine super critical and subcritical cycles. This study considers two different types of heat exchangers—helical coiled heat exchanger and printed circuit heat exchanger—as possible options for the AHTR secondary heat exchangers with the following three different options: (1) A single heat exchanger transfers all the heat (3,400 MW(t)) from the intermediate heat transfer loop to the power conversion system or process plants; (2) Two heat exchangers share heat to transfer total heat of 3,400 MW(t) from the intermediate heat transfer loop to the power conversion system or process plants, each exchanger transfers 1,700 MW(t) with a parallel configuration; and (3) Three heat exchangers share heat to transfer total heat of 3,400 MW(t) from the intermediate heat transfer loop to the power conversion system or process plants. Each heat exchanger transfers 1,130 MW(t) with a parallel configuration. A preliminary cost comparison will be provided for all different cases along with challenges and recommendations.« less

Transport Phenomena in Thin Rotating Liquid Films Including: Nucleate Boiling

NASA Technical Reports Server (NTRS)

Faghri, Amir

2005-01-01

In this grant, experimental, numerical and analytical studies of heat transfer in a thin liquid film flowing over a rotating disk have been conducted. Heat transfer coefficients were measured experimentally in a rotating disk heat transfer apparatus where the disk was heated from below with electrical resistance heaters. The heat transfer measurements were supplemented by experimental characterization of the liquid film thickness using a novel laser based technique. The heat transfer measurements show that the disk rotation plays an important role on enhancement of heat transfer primarily through the thinning of the liquid film. Experiments covered both momentum and rotation dominated regimes of the flow and heat transfer in this apparatus. Heat transfer measurements have been extended to include evaporation and nucleate boiling and these experiments are continuing in our laboratory. Empirical correlations have also been developed to provide useful information for design of compact high efficiency heat transfer devices. The experimental work has been supplemented by numerical and analytical analyses of the same problem. Both numerical and analytical results have been found to agree reasonably well with the experimental results on liquid film thickness and heat transfer Coefficients/Nusselt numbers. The numerical simulations include the free surface liquid film flow and heat transfer under disk rotation including the conjugate effects. The analytical analysis utilizes an integral boundary layer approach from which

Influence of Mode of Metal Transfer on Microstructure and Mechanical Properties of Gas Metal Arc-Welded Modified Ferritic Stainless Steel

NASA Astrophysics Data System (ADS)

Mukherjee, Manidipto; Pal, Tapan Kumar

2012-06-01

This article describes in detail the effect of the modes of metal transfer on the microstructure and mechanical properties of gas metal arc-welded modified ferritic stainless steel (SSP 409M) sheets (as received) of 4 mm thickness. The welded joints were prepared under three modes of metal transfer, i.e., short-circuit (SC), spray (S), transfer, and mix (M) mode transfer using two different austenitic filler wires (308L and 316L) and shielding gas composition of Ar + 5 pct CO2. The welded joints were evaluated by means of microstructural, hardness, notched tensile strength, Charpy impact toughness, and high cycle fatigue. The dependence of weld metal microstructure on modes of metal transfer and filler wires has been determined by dilution calculation, WRC-1992 diagram, Creq/Nieq ratio, stacking fault energy (SFE), optical microscopy (OM), and transmission electron microscopy (TEM). It was observed that the microstructure as well as the tensile, Charpy impact, and high cycle fatigue of weld metal is significantly affected by the mode of metal transfer and filler wire used. However, the heat-affected zone (HAZ) is affected only by the modes of metal transfer. The results have been correlated with the microstructures of weld and HAZ developed under different modes of metal transfer.

Modeling of Heating During Food Processing

NASA Astrophysics Data System (ADS)

Zheleva, Ivanka; Kamburova, Veselka

Heat transfer processes are important for almost all aspects of food preparation and play a key role in determining food safety. Whether it is cooking, baking, boiling, frying, grilling, blanching, drying, sterilizing, or freezing, heat transfer is part of the processing of almost every food. Heat transfer is a dynamic process in which thermal energy is transferred from one body with higher temperature to another body with lower temperature. Temperature difference between the source of heat and the receiver of heat is the driving force in heat transfer.

Post-Dryout Heat Transfer to a Refrigerant Flowing in Horizontal Evaporator Tubes

NASA Astrophysics Data System (ADS)

Mori, Hideo; Yoshida, Suguru; Kakimoto, Yasushi; Ohishi, Katsumi; Fukuda, Kenichi

Studies of the post-dryout heat transfer were made based on the experimental data for HFC-134a flowing in horizontal smooth and spiral1y grooved (micro-fin) tubes and the characteristics of the post-dryout heat transfer were c1arified. The heat transfer coefficient at medium and high mass flow rates in the smooth tube was lower than the single-phase heat transfer coefficient of the superheated vapor flow, of which mass flow rate was given on the assumption that the flow was in a thermodynamic equilibrium. A prediction method of post-dryout heat transfer coefficient was developed to reproduce the measurement satisfactorily for the smooth tube. The post dryout heat transfer in the micro-fin tube can be regarded approximately as a superheated vapor single-phase heat transfer.

Computational study of heat transfer in gas fluidization

NASA Astrophysics Data System (ADS)

Hou, Q. F.; Zhou, Z. Y.; Yu, A. B.

2013-06-01

Heat transfer in gas fluidization is investigated at a particle scale by means of a combined discrete element method and computational fluid dynamicsapproach. To develop understanding of heat transfer at various conditions, the effects of a few important material properties such as particle size, the Hamaker constant and particle thermal conductivity are examined through controlled numerical experiments. It is found that the convective heat transfer is dominant, and radiative heat transfer becomes important when the temperature is high. Conductive heat transfer also plays a role depending on the flow regimes and material properties. The heat transfer between a fluidized bed and an immersed surface is enhanced by the increase of particle thermal conductivity while it is little affected by Young's modulus. The findings should be useful for better understanding and predicting the heat transfer in gas fluidization.

Forced-convection Heat-transfer Characteristics of Molten Sodium Hydroxide

NASA Technical Reports Server (NTRS)

Grele, Milton D; Gedeon, Louis

1953-01-01

The forced-convection heat-transfer characteristics of sodium hydroxide were experimentally investigated. The heat-transfer data for heating fall slightly above the McAdams correlation line, and the heat-transfer data for cooling are fairly well represented by the McAdams correlation line.

24 CFR 3280.510 - Heat loss certificate.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 24 Housing and Urban Development 5 2012-04-01 2012-04-01 false Heat loss certificate. 3280.510... URBAN DEVELOPMENT MANUFACTURED HOME CONSTRUCTION AND SAFETY STANDARDS Thermal Protection § 3280.510 Heat... specify the following: (a) Heating zone certification. The design zone at which the manufactured home heat...

24 CFR 3280.510 - Heat loss certificate.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 24 Housing and Urban Development 5 2010-04-01 2010-04-01 false Heat loss certificate. 3280.510... URBAN DEVELOPMENT MANUFACTURED HOME CONSTRUCTION AND SAFETY STANDARDS Thermal Protection § 3280.510 Heat... specify the following: (a) Heating zone certification. The design zone at which the manufactured home heat...

24 CFR 3280.510 - Heat loss certificate.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 24 Housing and Urban Development 5 2013-04-01 2013-04-01 false Heat loss certificate. 3280.510... URBAN DEVELOPMENT MANUFACTURED HOME CONSTRUCTION AND SAFETY STANDARDS Thermal Protection § 3280.510 Heat... specify the following: (a) Heating zone certification. The design zone at which the manufactured home heat...

24 CFR 3280.510 - Heat loss certificate.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 24 Housing and Urban Development 5 2014-04-01 2014-04-01 false Heat loss certificate. 3280.510... URBAN DEVELOPMENT MANUFACTURED HOME CONSTRUCTION AND SAFETY STANDARDS Thermal Protection § 3280.510 Heat... specify the following: (a) Heating zone certification. The design zone at which the manufactured home heat...

24 CFR 3280.510 - Heat loss certificate.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 24 Housing and Urban Development 5 2011-04-01 2011-04-01 false Heat loss certificate. 3280.510... URBAN DEVELOPMENT MANUFACTURED HOME CONSTRUCTION AND SAFETY STANDARDS Thermal Protection § 3280.510 Heat... specify the following: (a) Heating zone certification. The design zone at which the manufactured home heat...

Linking Plagioclase Zoning Patterns to Active Magma Processes

NASA Astrophysics Data System (ADS)

Izbekov, P. E.; Nicolaysen, K. P.; Neill, O. K.; Shcherbakov, V.; Eichelberger, J. C.; Plechov, P.

2016-12-01

Plagioclase, one of the most common and abundant mineral phases in volcanic products, will vary in composition in response to changes in temperature, pressure, composition of the ambient silicate melt, and melt H2O concentration. Changes in these parameters may cause dissolution or growth of plagioclase crystals, forming characteristic textural and compositional variations (zoning patterns), the complete core-to-rim sequence of which describes events experienced by an individual crystal from its nucleation to the last moments of its growth. Plagioclase crystals in a typical volcanic rock may look drastically dissimilar despite their spatial proximity and the fact that they have erupted together. Although they shared last moments of their growth during magma ascent and eruption, their prior experiences could be very different, as plagioclase crystals often come from different domains of the same magma system. Distinguishing similar zoning patterns, correlating them across the entire population of plagioclase crystals, and linking these patterns to specific perturbations in the magmatic system may provide additional perspective on the variety, extent, and timing of magma processes at active volcanic systems. Examples of magma processes, which may be distinguished based on plagioclase zoning patterns, include (1) cooling due to heat loss, (2) heating and/or pressure build up due to an input of new magmatic material, (3) pressure drop in response to magma system depressurization, and (4) crystal transfer between different magma domains/bodies. This review will include contrasting examples of zoning patters from recent eruptions of Augustine and Cleveland Volcanoes in Alaska, Sakurajima Volcano in Japan, Karymsky, Bezymianny, and Tolbachik Volcanoes in Kamchatka, as well as from the drilling into an active magma body at Krafla, Iceland.

19 CFR 146.24 - Transfer of merchandise from a zone.

Code of Federal Regulations, 2010 CFR

2010-04-01

...; DEPARTMENT OF THE TREASURY (CONTINUED) FOREIGN TRADE ZONES Inventory Control and Recordkeeping System § 146... transferred from a zone will be accurately recorded within the inventory control and recordkeeping system. (2) The inventory control and recordkeeping system for merchandise transfers must have the capability to...

Microstructure and Microhardness of 17-4PH Deposited with Co-based Alloy Hardfacing Coating

NASA Astrophysics Data System (ADS)

Deng, D. W.; Zhang, C. P.; Chen, R.; Xia, H. F.

Hardfacing is widely used to improve the performance of components exposed to severe service conditions. In this paper, the surface modification was evaluated for precipitation hardening martensitic stainless steel 17-4PH deposited with Co-based alloy stellite12 by the plasma-transferred arc welding (PTAW). The microstructure and microhardness of coating and heat affected zone(HAZ) of base metal were characterized by optical microscope (OM), scanning electron scanning microscope (SEM), X-ray diffractometer and hardness tester. The results show that the interface between weld metal and base metal is favorable without pore and crack, at the same time elements diffusion is observed in the fusion area. However, as the distance from the interface increases, HAZ comprises three different microstructural zones, namely, zones of coarse overheated structures, quenching martensite and martensite, ferrite. The microhardness decreases gradually from the HAZ near interface to the base metal, except the zone of coarse overheated structures. The microhardness of the coating improves a lot and fluctuates in a definitive range, and microstructural gradient is observed including the fusion area (the planar region and the bulky dendrite in a direction perpendicular to the weld interface), the transition zone (the dendrite in a multi-direction way) and the fine grain zone near the surface in the coating (fine equiaxial structure).

Extension of Weighted Sum of Gray Gas Data to Mathematical Simulation of Radiative Heat Transfer in a Boiler with Gas-Soot Media

PubMed Central

Nouri-Borujerdi, Ali; Kazi, Salim Newaz

2014-01-01

In this study an expression for soot absorption coefficient is introduced to extend the weighted-sum-of-gray gases data to the furnace medium containing gas-soot mixture in a utility boiler 150 MWe. Heat transfer and temperature distribution of walls and within the furnace space are predicted by zone method technique. Analyses have been done considering both cases of presence and absence of soot particles at 100% load. To validate the proposed soot absorption coefficient, the expression is coupled with the Taylor and Foster's data as well as Truelove's data for CO2-H2O mixture and the total emissivities are calculated and compared with the Truelove's parameters for 3-term and 4-term gray gases plus two soot absorption coefficients. In addition, some experiments were conducted at 100% and 75% loads to measure furnace exit gas temperature as well as the rate of steam production. The predicted results show good agreement with the measured data at the power plant site. PMID:25143981

Extension of weighted sum of gray gas data to mathematical simulation of radiative heat transfer in a boiler with gas-soot media.

PubMed

Gharehkhani, Samira; Nouri-Borujerdi, Ali; Kazi, Salim Newaz; Yarmand, Hooman

2014-01-01

In this study an expression for soot absorption coefficient is introduced to extend the weighted-sum-of-gray gases data to the furnace medium containing gas-soot mixture in a utility boiler 150 MWe. Heat transfer and temperature distribution of walls and within the furnace space are predicted by zone method technique. Analyses have been done considering both cases of presence and absence of soot particles at 100% load. To validate the proposed soot absorption coefficient, the expression is coupled with the Taylor and Foster's data as well as Truelove's data for CO2-H2O mixture and the total emissivities are calculated and compared with the Truelove's parameters for 3-term and 4-term gray gases plus two soot absorption coefficients. In addition, some experiments were conducted at 100% and 75% loads to measure furnace exit gas temperature as well as the rate of steam production. The predicted results show good agreement with the measured data at the power plant site.

Development of Modified Incompressible Ideal Gas Model for Natural Draft Cooling Tower Flow Simulation

NASA Astrophysics Data System (ADS)

Hyhlík, Tomáš

2018-06-01

The article deals with the development of incompressible ideal gas like model, which can be used as a part of mathematical model describing natural draft wet-cooling tower flow, heat and mass transfer. It is shown, based on the results of a complex mathematical model of natural draft wet-cooling tower flow, that behaviour of pressure, temperature and density is very similar to the case of hydrostatics of moist air, where heat and mass transfer in the fill zone must be taken into account. The behaviour inside the cooling tower is documented using density, pressure and temperature distributions. The proposed equation for the density is based on the same idea like the incompressible ideal gas model, which is only dependent on temperature, specific humidity and in this case on elevation. It is shown that normalized density difference of the density based on proposed model and density based on the nonsimplified model is in the order of 10-4. The classical incompressible ideal gas model, Boussinesq model and generalised Boussinesq model are also tested. These models show deviation in percentages.

Fault-Tolerant Heat Exchanger

NASA Technical Reports Server (NTRS)

Izenson, Michael G.; Crowley, Christopher J.

2005-01-01

A compact, lightweight heat exchanger has been designed to be fault-tolerant in the sense that a single-point leak would not cause mixing of heat-transfer fluids. This particular heat exchanger is intended to be part of the temperature-regulation system for habitable modules of the International Space Station and to function with water and ammonia as the heat-transfer fluids. The basic fault-tolerant design is adaptable to other heat-transfer fluids and heat exchangers for applications in which mixing of heat-transfer fluids would pose toxic, explosive, or other hazards: Examples could include fuel/air heat exchangers for thermal management on aircraft, process heat exchangers in the cryogenic industry, and heat exchangers used in chemical processing. The reason this heat exchanger can tolerate a single-point leak is that the heat-transfer fluids are everywhere separated by a vented volume and at least two seals. The combination of fault tolerance, compactness, and light weight is implemented in a unique heat-exchanger core configuration: Each fluid passage is entirely surrounded by a vented region bridged by solid structures through which heat is conducted between the fluids. Precise, proprietary fabrication techniques make it possible to manufacture the vented regions and heat-conducting structures with very small dimensions to obtain a very large coefficient of heat transfer between the two fluids. A large heat-transfer coefficient favors compact design by making it possible to use a relatively small core for a given heat-transfer rate. Calculations and experiments have shown that in most respects, the fault-tolerant heat exchanger can be expected to equal or exceed the performance of the non-fault-tolerant heat exchanger that it is intended to supplant (see table). The only significant disadvantages are a slight weight penalty and a small decrease in the mass-specific heat transfer.

The historical trend in float zone crystal diameters and power requirements for float zoned silicon crystals

NASA Technical Reports Server (NTRS)

Kramer, H. G.

1981-01-01

The power needed to zone silicon crystals by radio frequency heating was analyzed. The heat loss mechanisms are examined. Curves are presented for power as a function of crystal diameter for commercial silicon zoning.

Heat transfer in gas turbine engines and three-dimensional flows; Proceedings of the Symposium, ASME Winter Annual Meeting, Chicago, IL, Nov. 27-Dec. 2, 1988

NASA Technical Reports Server (NTRS)

Elovic, E. (Editor); O'Brien, J. E. (Editor); Pepper, D. W. (Editor)

1988-01-01

The present conference on heat transfer characteristics of gas turbines and three-dimensional flows discusses velocity-temperature fluctuation correlations at the flow stagnation flow of a circular cylinder in turbulent flow, heat transfer across turbulent boundary layers with pressure gradients, the effect of jet grid turbulence on boundary layer heat transfer, and heat transfer characteristics predictions for discrete-hole film cooling. Also discussed are local heat transfer in internally cooled turbine airfoil leading edges, secondary flows in vane cascades and curved ducts, three-dimensional numerical modeling in gas turbine coal combustor design, numerical and experimental results for tube-fin heat exchanger airflow and heating characteristics, and the computation of external hypersonic three-dimensional flow field and heat transfer characteristics.

Heat transfer in gas turbine engines and three-dimensional flows; Proceedings of the Symposium, ASME Winter Annual Meeting, Chicago, IL, Nov. 27-Dec. 2, 1988

NASA Astrophysics Data System (ADS)

Elovic, E.; O'Brien, J. E.; Pepper, D. W.

The present conference on heat transfer characteristics of gas turbines and three-dimensional flows discusses velocity-temperature fluctuation correlations at the flow stagnation flow of a circular cylinder in turbulent flow, heat transfer across turbulent boundary layers with pressure gradients, the effect of jet grid turbulence on boundary layer heat transfer, and heat transfer characteristics predictions for discrete-hole film cooling. Also discussed are local heat transfer in internally cooled turbine airfoil leading edges, secondary flows in vane cascades and curved ducts, three-dimensional numerical modeling in gas turbine coal combustor design, numerical and experimental results for tube-fin heat exchanger airflow and heating characteristics, and the computation of external hypersonic three-dimensional flow field and heat transfer characteristics.

Numerical investigation of supercritical LNG convective heat transfer in a horizontal serpentine tube

NASA Astrophysics Data System (ADS)

Han, Chang-Liang; Ren, Jing-Jie; Dong, Wen-Ping; Bi, Ming-Shu

2016-09-01

The submerged combustion vaporizer (SCV) is indispensable general equipment for liquefied natural gas (LNG) receiving terminals. In this paper, numerical simulation was conducted to get insight into the flow and heat transfer characteristics of supercritical LNG on the tube-side of SCV. The SST model with enhanced wall treatment method was utilized to handle the coupled wall-to-LNG heat transfer. The thermal-physical properties of LNG under supercritical pressure were used for this study. After the validation of model and method, the effects of mass flux, outer wall temperature and inlet pressure on the heat transfer behaviors were discussed in detail. Then the non-uniformity heat transfer mechanism of supercritical LNG and effect of natural convection due to buoyancy change in the tube was discussed based on the numerical results. Moreover, different flow and heat transfer characteristics inside the bend tube sections were also analyzed. The obtained numerical results showed that the local surface heat transfer coefficient attained its peak value when the bulk LNG temperature approached the so-called pseudo-critical temperature. Higher mass flux could eliminate the heat transfer deteriorations due to the increase of turbulent diffusion. An increase of outer wall temperature had a significant influence on diminishing heat transfer ability of LNG. The maximum surface heat transfer coefficient strongly depended on inlet pressure. Bend tube sections could enhance the heat transfer due to secondary flow phenomenon. Furthermore, based on the current simulation results, a new dimensionless, semi-theoretical empirical correlation was developed for supercritical LNG convective heat transfer in a horizontal serpentine tube. The paper provided the mechanism of heat transfer for the design of high-efficiency SCV.

Heat transfer in aeropropulsion systems

NASA Astrophysics Data System (ADS)

Simoneau, R. J.

1985-07-01

Aeropropulsion heat transfer is reviewed. A research methodology based on a growing synergism between computations and experiments is examined. The aeropropulsion heat transfer arena is identified as high Reynolds number forced convection in a highly disturbed environment subject to strong gradients, body forces, abrupt geometry changes and high three dimensionality - all in an unsteady flow field. Numerous examples based on heat transfer to the aircraft gas turbine blade are presented to illustrate the types of heat transfer problems which are generic to aeropropulsion systems. The research focus of the near future in aeropropulsion heat transfer is projected.

Heat transfer in aeropropulsion systems

NASA Technical Reports Server (NTRS)

Simoneau, R. J.

1985-01-01

Aeropropulsion heat transfer is reviewed. A research methodology based on a growing synergism between computations and experiments is examined. The aeropropulsion heat transfer arena is identified as high Reynolds number forced convection in a highly disturbed environment subject to strong gradients, body forces, abrupt geometry changes and high three dimensionality - all in an unsteady flow field. Numerous examples based on heat transfer to the aircraft gas turbine blade are presented to illustrate the types of heat transfer problems which are generic to aeropropulsion systems. The research focus of the near future in aeropropulsion heat transfer is projected.

Thermal-field propagation in an exocontact zone of a magmatic body and its impact on radiogenic isotope concentrations in minerals.

PubMed

Brandt, I S; Rasskazov, S V; Brandt, S B; Ivanov, A V

2002-03-01

In application of radioactive isotope systems (K-Ar, Rb-Sr etc.) during the last decades, experience was gained not only on their geochronometrical uses, but also on estimations of some important parameters of geological processes, especially temperatures and durations of superimposed thermal events. In this paper, the formation of an exocontact thermal field of a magmatic intrusion is considered as a spreading of a thermal source delta-function. Appropriate solutions of the heat-transfer equation are deduced and correlated with diffusion parameters of the radiogenic argon, coupling radioactive, thermal and kinetic parameters in an exocontant zone of a magmatic body. These solutions were used for quantitative reinterpretations of data taken from Hart's classical paper [The petrology and isotopic mineral age relations of a contact zone in the Front Range, Colorado. J. Geol., 1964, v. 72, pp. 493-525]. Theoretic and measured radiogenic argon and strontium concentrations within exocontact aureoles are found to be in good concordance.

Aerodynamic heating effects on wall-modeled large-eddy simulations of high-speed flows

NASA Astrophysics Data System (ADS)

Yang, Xiang; Urzay, Javier; Moin, Parviz

2017-11-01

Aerospace vehicles flying at high speeds are subject to increased wall-heating rates because of strong aerodynamic heating in the near-wall region. In wall-modeled large-eddy simulations (WMLES), this near-wall region is typically not resolved by the computational grid. As a result, the effects of aerodynamic heating need to be modeled using an LES wall model. In this investigation, WMLES of transitional and fully turbulent high-speed flows are conducted to address this issue. In particular, an equilibrium wall model is employed in high-speed turbulent Couette flows subject to different combinations of thermal boundary conditions and grid sizes, and in transitional hypersonic boundary layers interacting with incident shock waves. Specifically, the WMLES of the Couette-flow configuration demonstrate that the shear-stress and heat-flux predictions made by the wall model show only a small sensitivity to the grid resolution even in the most adverse case where aerodynamic heating prevails near the wall and generates a sharp temperature peak there. In the WMLES of shock-induced transition in boundary layers, the wall model is tested against DNS and experiments, and it is shown to capture the post-transition aerodynamic heating and the overall heat transfer rate around the shock-impingement zone. This work is supported by AFOSR.

Analysis of the heat transfer in double and triple concentric tube heat exchangers

NASA Astrophysics Data System (ADS)

Rădulescu, S.; Negoiţă, L. I.; Onuţu, I.

2016-08-01

The tubular heat exchangers (shell and tube heat exchangers and concentric tube heat exchangers) represent an important category of equipment in the petroleum refineries and are used for heating, pre-heating, cooling, condensation and evaporation purposes. The paper presents results of analysis of the heat transfer to cool a petroleum product in two types of concentric tube heat exchangers: double and triple concentric tube heat exchangers. The cooling agent is water. The triple concentric tube heat exchanger is a modified constructive version of double concentric tube heat exchanger by adding an intermediate tube. This intermediate tube improves the heat transfer by increasing the heat area per unit length. The analysis of the heat transfer is made using experimental data obtained during the tests in a double and triple concentric tube heat exchanger. The flow rates of fluids, inlet and outlet temperatures of water and petroleum product are used in determining the performance of both heat exchangers. Principally, for both apparatus are calculated the overall heat transfer coefficients and the heat exchange surfaces. The presented results shows that triple concentric tube heat exchangers provide better heat transfer efficiencies compared to the double concentric tube heat exchangers.

An investigation on near wall transport characteristics in an adiabatic upward gas-liquid two-phase slug flow

NASA Astrophysics Data System (ADS)

Zheng, Donghong; Che, Defu

2007-08-01

The near-wall transport characteristics, inclusive of mass transfer coefficient and wall shear stress, which have a great effect on gas-liquid two-phase flow induced internal corrosion of low alloy pipelines in vertical upward oil and gas mixing transport, have been both mechanistically and experimentally investigated in this paper. Based on the analyses on the hydrodynamic characteristics of an upward slug unit, the mass transfer in the near wall can be divided into four zones, Taylor bubble nose zone, falling liquid film zone, Taylor bubble wake zone and the remaining liquid slug zone; the wall shear stress can be divided into two zones, the positive wall shear stress zone associated with the falling liquid film and the negative wall shear stress zone associated with the liquid slug. Based on the conventional mass transfer and wall shear stress characteristics formulas of single phase liquid full-pipe turbulent flow, corrected normalized mass transfer coefficient formula and wall shear stress formula are proposed. The calculated results are in good agreement with the experimental data. The shear stress and the mass transfer coefficient in the near wall zone are increased with the increase of superficial gas velocity and decreased with the increase of superficial liquid velocity. The mass transfer coefficients in the falling liquid film zone and the wake zone of leading Taylor bubble are lager than those in the Taylor bubble nose zone and the remaining liquid slug zone, and the wall shear stress associated falling liquid film is larger than that associated the liquid slug. The mass transfer coefficient is within 10-3 m/s, and the wall shear stress below 103 Pa. It can be concluded that the alternate wall shear stress due to upward gas-liquid slug flow is considered to be the major cause of the corrosion production film fatigue cracking.

Relative role of transfer zones in controlling sequence stacking patterns and facies distribution: insights from the Fushan Depression, South China Sea

NASA Astrophysics Data System (ADS)

Liu, Entao; Wang, Hua; Li, Yuan; Huang, Chuanyan

2015-04-01

In sedimentary basins, a transfer zone can be defined as a coordinated system of deformational features which has good prospects for hydrocarbon exploration. Although the term 'transfer zone' has been widely applied to the study of extensional basins, little attention has been paid to its controlling effect on sequence tracking pattern and depositional facies distribution. Fushan Depression is a half-graben rift sub-basin, located in the southeast of the Beibuwan Basin, South China Sea. In this study, comparative analysis of seismic reflection, palaeogeomorphology, fault activity and depositional facies distribution in the southern slope indicates that three different types of sequence stacking patterns (i.e. multi-level step-fault belt in the western area, flexure slope belt in the central area, gentle slope belt in the eastern area) were developed along the southern slope, together with a large-scale transfer zone in the central area, at the intersection of the western and eastern fault systems. Further analysis shows that the transfer zone played an important role in the diversity of sequence stacking patterns in the southern slope by dividing the Fushan Depression into two non-interfering tectonic systems forming different sequence patterns, and leading to the formation of the flexure slope belt in the central area. The transfer zone had an important controlling effect on not only the diversity of sequence tracking patterns, but also the facies distribution on the relay ramp. During the high-stand stage, under the controlling effect of the transfer zone, the sediments contain a significant proportion of coarser material accumulated and distributed along the ramp axis. By contrast, during the low-stand stage, the transfer zone did not seem to contribute significantly to the low-stand fan distribution which was mainly controlled by the slope gradient (palaeogeomorphology). Therefore, analysis of the transfer zone can provide a new perspective for basin analysis. In addition, the transfer zone area demonstrated unique hydrocarbon accumulation models different from the western and eastern areas. It was not only a structural high combined with sufficient coarse-grained reservoir quality sands, but was also associated with large-scale sublacustrine fan deposits with high quality reservoirs, indicating that the recognition of transfer zones can improve the prediction of hydrocarbon occurrences in similar settings.

Two part condenser for varying the rate of condensing and related method

DOEpatents

Dobos, James G.

2007-12-11

A heat transfer apparatus, such as a condenser, is provided. The apparatus includes a first component with a first heat transfer element that has first component inlet and outlet ports through which a first fluid may pass. A second component is also included and likewise has a second heat transfer element with second component inlet and outlet ports to pass a second fluid. The first component has a body that can receive a third fluid for heat transfer with the first heat transfer element. The first and second components are releasably attachable with one another so that when attached both the first and second heat transfer elements effect heat transfer with the third fluid. Attachment and removal of the first and second components allows for the heat transfer rate of the apparatus to be varied. An associated method is also provided.

Pyrolysis reactor and fluidized bed combustion chamber

DOEpatents

Green, Norman W.

1981-01-06

A solid carbonaceous material is pyrolyzed in a descending flow pyrolysis reactor in the presence of a particulate source of heat to yield a particulate carbon containing solid residue. The particulate source of heat is obtained by educting with a gaseous source of oxygen the particulate carbon containing solid residue from a fluidized bed into a first combustion zone coupled to a second combustion zone. A source of oxygen is introduced into the second combustion zone to oxidize carbon monoxide formed in the first combustion zone to heat the solid residue to the temperature of the particulate source of heat.

Calculation of critical heat transfer in horizontal evaporator pipes in cooling systems of high-rise buildings

NASA Astrophysics Data System (ADS)

Aksenov, Andrey; Malysheva, Anna

2018-03-01

An exact calculation of the heat exchange of evaporative surfaces is possible only if the physical processes of hydrodynamics of two-phase flows are considered in detail. Especially this task is relevant for the design of refrigeration supply systems for high-rise buildings, where powerful refrigeration equipment and branched networks of refrigerants are used. On the basis of experimental studies and developed mathematical model of asymmetric dispersed-annular flow of steam-water flow in horizontal steam-generating pipes, a calculation formula has been obtained for determining the boundaries of the zone of improved heat transfer and the critical value of the heat flux density. A new theoretical approach to the solution of the problem of the flow structure of a two-phase flow is proposed. The applied method of dissipative characteristics of a two-phase flow in pipes and the principle of a minimum rate of entropy increase in stabilized flows made it possible to obtain formulas that directly reflect the influence of the viscous characteristics of the gas and liquid media on their distribution in the flow. The study showed a significant effect of gravitational forces on the nature of the phase distribution in the cross section of the evaporative tubes. At a mass velocity of a two-phase flow less than 700 kg / m2s, the volume content of the liquid phase near the upper outer generating lines of the tube is almost an order of magnitude lower than the lower one. The calculation of the heat transfer crisis in horizontal evaporative tubes is obtained. The calculated dependence is in good agreement with the experimental data of the author and a number of foreign researchers. The formula generalizes the experimental data for pipes with the diameter of 6-40 mm in the pressure of 2-7 MPa.

A basic study on Thermosyphon-type thermal storage unit (TSU) using Nanofluid as the heat transfer medium

NASA Astrophysics Data System (ADS)

Li, Shuang-Fei; Wang, Ping-Yang; Liu, Zhen-hua

2018-05-01

This study proposed a novel thermosyphon-type thermal storage unit using water-based CuO nanofluid as the phase-change heat transfer medium. Seven tubular canisters containing solid-liquid phase-change material (PCM) with peak melting temperature of 100 °C were placed vertically into the center of the TSU which is a vertical cylindrical vessel made of stainless steel. Coat formed by depositing nanoparticles during the phase-change process was adopted to increase the wettability of the heat transfer surfaces of the canisters. We investigated the phase-change heat transfer, as well as the heat-storage and heat-release properties, of the TSU through experimental and computational analysis. Our results demonstrate that this thermal storage unit construction can propose good heat transfer and heat-storage/heat-release performance. The coating of nanoparticles onto the heat transfer surfaces increases the surface wettability and improves both the evaporation and condensation heat transfer. The main thermal resistance in the TSU results from the conductive heat transfer inside of the PCM. All phase-change thermal resistance of liquid film in charging and discharging processes can be ignored in this TSU.

Combined Heat Transfer in High-Porosity High-Temperature Fibrous Insulations: Theory and Experimental Validation

NASA Technical Reports Server (NTRS)

Daryabeigi, Kamran; Cunnington, George R.; Miller, Steve D.; Knutson, Jeffry R.

2010-01-01

Combined radiation and conduction heat transfer through various high-temperature, high-porosity, unbonded (loose) fibrous insulations was modeled based on first principles. The diffusion approximation was used for modeling the radiation component of heat transfer in the optically thick insulations. The relevant parameters needed for the heat transfer model were derived from experimental data. Semi-empirical formulations were used to model the solid conduction contribution of heat transfer in fibrous insulations with the relevant parameters inferred from thermal conductivity measurements at cryogenic temperatures in a vacuum. The specific extinction coefficient for radiation heat transfer was obtained from high-temperature steady-state thermal measurements with large temperature gradients maintained across the sample thickness in a vacuum. Standard gas conduction modeling was used in the heat transfer formulation. This heat transfer modeling methodology was applied to silica, two types of alumina, and a zirconia-based fibrous insulation, and to a variation of opacified fibrous insulation (OFI). OFI is a class of insulations manufactured by embedding efficient ceramic opacifiers in various unbonded fibrous insulations to significantly attenuate the radiation component of heat transfer. The heat transfer modeling methodology was validated by comparison with more rigorous analytical solutions and with standard thermal conductivity measurements. The validated heat transfer model is applicable to various densities of these high-porosity insulations as long as the fiber properties are the same (index of refraction, size distribution, orientation, and length). Furthermore, the heat transfer data for these insulations can be obtained at any static pressure in any working gas environment without the need to perform tests in various gases at various pressures.

Properties and heat transfer coefficients of four molten-salt high temperature heat transfer fluid candidates for concentrating solar power plants

NASA Astrophysics Data System (ADS)

Liu, T. L.; Liu, W. R.; Xu, X. H.

2017-11-01

Heat transfer fluid is one critical component for transferring and storing heat energy in concentrating solar power systems. Molten-salt mixtures can be used as high temperature heat transfer fluids because of their thermophysical properties. This paper studied the thermophysical properties of Li2CO3-Na2CO3-K2CO3 eutectic salt and three eutectic chloride salts NaCl-KCl-ZnCl2 with different compositions in the range of 450-600°C and 250-800°C, respectively. Properties including specific heat capacity, thermal conductivity, density and viscosity were determined based on imperial correlations and compared at different operating temperatures. The heat transfer coefficients of using different eutectic salts as heat transfer fluids were also calculated and compared in their operating temperature range. It is concluded that all the four eutectic salts can satisfy the requirements of a high-temperature heat transfer fluid.

Modelling of the MEA float zone using accelerometer data

NASA Technical Reports Server (NTRS)

Alexander, J. Iwan D.

1993-01-01

During a floating zone experiment involving the growth of indium on a recent orbiter mission, (STS 32) oscillation of the zone shapes were observed to occur in response to the background acceleration. An understanding of the nature of the response of the zone shape to forced (g-jitter) oscillations and predictions of its impact on future experiments is of great interest not only to the PI's but to other commercial and academic investigators who plan to fly similar experiments in the orbiter and on space station. Motivated by this, a 15 month study was undertaken to analyze the nature of the g-sensitivity of the STS 32 floating zone crystal growth experiment. Numerical models were used to describe the time-dependent free surface motion of the zone as it responds to the spacecraft residual acceleration. Relevant experimental data concerning the acceleration environment was obtained from the Honeywell in Space Accelerometer (HISA) investigators through MSFC's ACAP program and processed and analyzed. For the indium floating zone experiment, a series of calculations were made using time-dependent axial accelerations g(t). The form of g(t) included simple sinusoidal disturbances as well as actual data (subject to appropriate filtering) measured on the STS 32 mission. Focus was on the calculation of the response of the free surface of the zone as well as the internal flows and internal heat transfer. The influence of solidification on the response of the zone shape was also examined but found to be negligible.

Flammability of Heterogeneously Combusting Metals

NASA Technical Reports Server (NTRS)

Jones, Peter D.

1998-01-01

Most engineering materials, including some metals, most notably aluminum, burn in homogeneous combustion. 'Homogeneous' refers to both the fuel and the oxidizer being in the same phase, which is usually gaseous. The fuel and oxidizer are well mixed in the combustion reaction zone, and heat is released according to some relation like q(sub c) = delta H(sub c)c[((rho/rho(sub 0))]exp a)(exp -E(sub c)/RT), Eq. (1) where the pressure exponent a is usually close to unity. As long as there is enough heat released, combustion is sustained. It is useful to conceive of a threshold pressure beyond which there is sufficient heat to keep the temperature high enough to sustain combustion, and beneath which the heat is so low that temperature drains away and the combustion is extinguished. Some materials burn in heterogeneous combustion, in which the fuel and oxidizer are in different phases. These include iron and nickel based alloys, which burn in the liquid phase with gaseous oxygen. Heterogeneous combustion takes place on the surface of the material (fuel). Products of combustion may appear as a solid slag (oxide) which progressively covers the fuel. Propagation of the combustion melts and exposes fresh fuel. Heterogeneous combustion heat release also follows the general form of Eq.(1), except that the pressure exponent a tends to be much less than 1. Therefore, the increase in heat release with increasing pressure is not as dramatic as it is in homogeneous combustion. Although the concept of a threshold pressure still holds in heterogeneous combustion, the threshold is more difficult to identify experimentally, and pressure itself becomes less important relative to the heat transfer paths extant in any specific application. However, the constants C, a, and E(sub c) may still be identified by suitable data reduction from heterogeneous combustion experiments, and may be applied in a heat transfer model to judge the flammability of a material in any particular actual-use situation. In order to support the above assertions, two investigations are undertaken: 1) PCT data are examined in detail to discover the pressure dependence of heterogeneous combustion experiment results; and 2) heterogeneous combustion in a PCT situation is described by a heat transfer model, which is solved first in simplified form for a simple actual-use situation, and then extended to apply to PCT data reduction (combustion constant identification).

Thermocapillary flow contribution to dropwise condensation heat transfer

NASA Astrophysics Data System (ADS)

Phadnis, Akshay; Rykaczewski, Konrad

2017-11-01

With recent developments of durable hydrophobic materials potentially enabling industrial applications of dropwise condensation, accurate modeling of heat transfer during this phase change process is becoming increasingly important. Classical steady state models of dropwise condensation are based on the integration of heat transfer through individual droplets over the entire drop size distribution. These models consider only the conduction heat transfer inside the droplets. However, simple scaling arguments suggest that thermocapillary flows might exist in such droplets. In this work, we used Finite Element heat transfer model to quantify the effect of Marangoni flow on dropwise condensation heat transfer of liquids with a wide range of surface tensions ranging from water to pentane. We confirmed that the Marangoni flow is present for a wide range of droplet sizes, but only has quantifiable effects on heat transfer in drops larger than 10 µm. By integrating the single drop heat transfer simulation results with drop size distribution for the cases considered, we demonstrated that Marangoni flow contributes a 10-30% increase in the overall heat transfer coefficient over conduction only model.

Ballistic Range Measurements of Stagnation-Point Heat Transfer in Air and in Carbon Dioxide at Velocities up to 18,000 Feet Per Second

NASA Technical Reports Server (NTRS)

Yee, Layton; Bailey, Harry E.; Woodward, Henry T.

1961-01-01

A new technique for measuring heat-transfer rates on free-flight models in a ballistic range is described in this report. The accuracy of the heat-transfer rates measured in this way is shown to be comparable with the accuracy obtained in shock-tube measurements. The specific results of the present experiments consist of measurements of the stagnation-point heat-transfer rates experienced by a spherical-nosed model during flight through air and through carbon dioxide at velocities up to 18,000 feet per second. For flight through air these measured heat-transfer rates agree well with both the theoretically predicted rates and the rates measured in shock tubes. the heat-transfer rates agree well with the rates measured in a shock tube. Two methods of estimating the stagnation-point heat-transfer rates in carbon dioxide are compared with the experimental measurements. At each velocity the measured stagnation-point heat-transfer rate in carbon dioxide is about the same as the measured heat-transfer rate in air.

Heat transfer in freeboard region of fluidized beds

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

Biyikli, S.; Tuzla, K.; Chen, J.C.

1983-10-01

This research involved the study of heat transfer and fluid mechanic characteristics around a horizontal tube in the freeboard region of fluidized beds. Heat transfer coefficients were experimetnally measured for different bed temperatures, particle sizes, gas flow rates, and tube elevations in the freeboard region of air fluidized beds at atmospheric pressure. Local heat transfer coefficients were found to vary significantly with angular position around the tube. Average heat transfer coefficients were found to decrease with increasing freeboard tube elevation and approach the values for gas convection plus radiation for any given gas velocity. For a fixed tube elevation, heatmore » transfer coefficients generally increased with increasing gas velocity and with high particle entrainment they can approach the magnitudes found for immersed tubes. Heat transfer coefficients were also found to increase with increasing bed temperature. It was concluded that this increase is partly due to increase of radiative heat transfer and partly due to change of thermal properties of the fluidizing gas and particles. To investigate the fluid mechanic behavior of gas and particles around a freeboard tube, transient particle tube contacts were measured with a special capacitance probe in room temperature experiments. The results indicated that the tube surface experiences alternating dense and lean phase contacts. Quantitative information for local characteristics was obtained from the capacitance signals and used to develop a phenomenological model for prediction of the heat transfer coefficients around freeboard tubes. The packet renewal theory was modified to account for the dense phase heat transfer and a new model was suggested for the lean phase heat transfer. Finally, an empirical freeboard heat transfer correlation was developed from functional analysis of the freeboard heat transfer data using nondimensional groups representing gas velocity and tube elevation.« less

Modeling macro-and microstructures of gas-metal-arc welded HSLA-100 steel

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

Yang, Z.; Debroy, T.

1999-06-01

Fluid flow and heat transfer during gas-metal-arc welding (GMAW) of HSLA-100 steel were studied using a transient, three-dimensional, turbulent heat transfer and fluid flow model. The temperature and velocity fields, cooling rates, and shape and size of the fusion and heat-affected zones (HAZs) were calculated. A continuous-cooling-transformation (CCT) diagram was computed to aid in the understanding of the observed weld metal microstructure. The computed results demonstrate that the dissipation of heat and momentum in the weld pool is significantly aided by turbulence,m thus suggesting that previous modeling results based on laminar flow need to be re-examined. A comparison of themore » calculated fusion and HAZ geometries with their corresponding measured values showed good agreement. Furthermore, finger penetration, a unique geometric characteristic of gas-metal-arc weld pools, could be satisfactorily predicted from the model. The ability to predict these geometric variables and the agreement between the calculated and the measured cooling rates indicate the appropriateness of using a turbulence model for accurate calculations. The microstructure of the weld metal consisted mainly of acicular ferrite with small amounts of bainite. At high heat inputs, small amounts of allotriomorphic and Widmanstaetten ferrite were also observed. The observed microstructures are consistent with those expected from the computed CCT diagram and the cooling rates. The results presented here demonstrate significant promise for understanding both macro-and microstructures of steel welds from the combination of the fundamental principles from both transport phenomena and phase transformation theory.« less

Degradation of ground ice in a changing climate: the potential impact of groundwater flow

NASA Astrophysics Data System (ADS)

de Grandpré, I.; Fortier, D.; Stephani, E.

2011-12-01

Climate changes affecting the North West portion of Canada alter the thermal state of the permafrost and promote ground ice degradation. Melting of ground ice leads to greater water flow into the ground and to significant hydraulic changes (i.e. drainage of peatland and lakes, triggering of thermokarst and new groundwater flow patterns). Road infrastructures built on permafrost are particularly sensitive to permafrost degradation. Road construction and maintenance induce heat flux into the ground by the increase of solar radiation absorption (comparing to natural ground), the increase of snow cover on side slopes, the infiltration of water in embankment material and the migration of surface water in the active layer. The permafrost under the roads is therefore submitted to a warmer environment than in natural ground and his behavior reflects how the permafrost will act in the future with the global warming trend. The permafrost degradation dynamic under a road was studied at the Beaver Creek (Yukon) experimental site located on the Alaska Highway. Permafrost was characterized as near-zero Celcius and highly susceptible to differential thaw-settlement due to the ground ice spatial distribution. Ice-rich cryostructures typical of syngenetic permafrost (e.g. microlenticular) were abundant in the upper and lower cryostratigraphic units of fine-grained soils (Units 1, 2A, and 2C). The middle ice-poor silt layer (Unit 2B) characterized by porous cryostructure comprised the top of a buried ice-wedge network extending several meters in the underlying layers and susceptible to degradation by thermo-erosion. These particular features of the permafrost at the study site facilitated the formation of taliks (unfrozen zones) under the road which leaded to a greater water flow. We believe that water flow is promoting an acceleration of permafrost degradation by advective heat transfer. This process remains poorly studied and quantified in permafrost environment. Field data on topography, soil geotechnical properties, water table and preferential flow paths characterization, ground and water temperature and active layer and permafrost depth were collected to built seepage, heat transfer and coupled advecto-conductive models. Results indicated that advective heat transfer processes associated with groundwater flow can have a substantial impact on permafrost degradation. After one year, the active layer was 4 m deeper in the advecto-conductive heat transfer model than in the conductive heat transfer model and this was corroborated with measured field data. Groundwater flow processes should therefore be taken into account in permafrost evolution models and climate warming scenarios.

Eastern Mediterranean geothermal resources and subduction dynamics

NASA Astrophysics Data System (ADS)

Roche, Vincent; Sternai, Pietro; Guillou-Frottier, Laurent; Jolivet, Laurent; Gerya, Taras

2017-04-01

The Aegean-Anatolian retreating subduction and collision zones have been investigated through 3D numerical geodynamic models involving slab rollback/tearing/breakoff constrained by, for instance, seismic tomography or anisotropy and geochemical proxies. Here, we integrate these investigations by using the well documented geothermal anomalies geothermal anomalies. First, we use 3D high-resolution thermo-mechanical numerical models to quantify the potential contribution of the past Aegean-Anatolian subduction dynamics to such present-day measured thermal anomalies. Results suggest an efficient control of subduction-related asthenospheric return flow on the regional distribution of thermal anomalies. Our quantification shows that the slab-induced shear heating at the base of the crust could partly explain the high heat flow values above the slab tear (i.e. in the Menderes Massif, Western Turkey). Second, the associated thermal signature at the base of the continental crust is used as basal thermal boundary condition for 2D crustal-scale models dedicated to the understanding of heat transfer from the abnormally hot mantle to the shallow geothermal reservoir. These models couple heat transfer and fluid flow equations with appropriate fluid and rock physical properties. Results suggest that permeable low-angle normal faults (detachments) in the back-arc region can control the bulk of the heat transport and fluid circulation patterns. We suggest that detachments can drain crustal and/or mantellic fluids up to several kilometers depths. At the basin-scale, we show that the permeability of detachments may control the reservoirs location. Temperatures at the base of detachments may be subject to protracted increase (due to anomalously high basal heat flow) through time, thereby generating dome-shaped thermal structures. These structures, usually with 20km characteristic wavelength, may reach the Moho involving lateral rheological contrasts and possibly crustal-scale boudinage, thereby driving the formation of new crustal detachments.

Inductively heated particulate matter filter regeneration control system

DOEpatents

Gonze, Eugene V; Paratore Jr., Michael J; Kirby, Kevin W; Phelps, Amanda; Gregoire, Daniel J

2012-10-23

A system includes a particulate matter (PM) filter with an upstream end for receiving exhaust gas, a downstream end and zones. The system also includes a heating element. A control module selectively activates the heating element to inductively heat one of the zones.

Local convective heat transfer coefficient and friction factor of CuO/water nanofluid in a microchannel heat sink

NASA Astrophysics Data System (ADS)

Chabi, A. R.; Zarrinabadi, S.; Peyghambarzadeh, S. M.; Hashemabadi, S. H.; Salimi, M.

2017-02-01

Forced convective heat transfer in a microchannel heat sink (MCHS) using CuO/water nanofluids with 0.1 and 0.2 vol% as coolant was investigated. The experiments were focused on the heat transfer enhancement in the channel entrance region at Re < 1800. Hydraulic performance of the MCHS was also estimated by measuring friction factor and pressure drop. Results showed that higher convective heat transfer coefficient was obtained at the microchannel entrance. Maximum enhancement of the average heat transfer coefficient compared with deionized water was about 40 % for 0.2 vol% nanofluid at Re = 1150. Enhancement of the convective heat transfer coefficient of nanofluid decreased with further increasing of Reynolds number.

The effects of climate change on heating energy consumption of office buildings in different climate zones in China

NASA Astrophysics Data System (ADS)

Meng, Fanchao; Li, Mingcai; Cao, Jingfu; Li, Ji; Xiong, Mingming; Feng, Xiaomei; Ren, Guoyu

2017-06-01

Climate plays an important role in heating energy consumption owing to the direct relationship between space heating and changes in meteorological conditions. To quantify the impact, the Transient System Simulation Program software was used to simulate the heating loads of office buildings in Harbin, Tianjin, and Shanghai, representing three major climate zones (i.e., severe cold, cold, and hot summer and cold winter climate zones) in China during 1961-2010. Stepwise multiple linear regression was performed to determine the key climatic parameters influencing heating energy consumption. The results showed that dry bulb temperature (DBT) is the dominant climatic parameter affecting building heating loads in all three climate zones across China during the heating period at daily, monthly, and yearly scales (R 2 ≥ 0.86). With the continuous warming climate in winter over the past 50 years, heating loads decreased by 14.2, 7.2, and 7.1 W/m2 in Harbin, Tianjin, and Shanghai, respectively, indicating that the decreasing rate is more apparent in severe cold climate zone. When the DBT increases by 1 °C, the heating loads decrease by 253.1 W/m2 in Harbin, 177.2 W/m2 in Tianjin, and 126.4 W/m2 in Shanghai. These results suggest that the heating energy consumption can be well predicted by the regression models at different temporal scales in different climate conditions owing to the high determination coefficients. In addition, a greater decrease in heating energy consumption in northern severe cold and cold climate zones may efficiently promote the energy saving in these areas with high energy consumption for heating. Particularly, the likely future increase in temperatures should be considered in improving building energy efficiency.

Cooperative heat transfer and ground coupled storage system

DOEpatents

Metz, Philip D.

1982-01-01

A cooperative heat transfer and ground coupled storage system wherein collected solar heat energy is ground stored and permitted to radiate into the adjacent ground for storage therein over an extended period of time when such heat energy is seasonally maximally available. Thereafter, when said heat energy is seasonally minimally available and has propagated through the adjacent ground a substantial distance, the stored heat energy may be retrieved by a circumferentially arranged heat transfer means having a high rate of heat transfer.

Cooperative heat transfer and ground coupled storage system

DOEpatents

Metz, P.D.

A cooperative heat transfer and ground coupled storage system wherein collected solar heat energy is ground stored and permitted to radiate into the adjacent ground for storage therein over an extended period of time when such heat energy is seasonally maximally available. Thereafter, when said heat energy is seasonally minimally available and has propagated through the adjacent ground a substantial distance, the stored heat energy may be retrieved by a circumferentially arranged heat transfer means having a high rate of heat transfer.

27 CFR 28.141 - General.

Code of Federal Regulations, 2012 CFR

2012-04-01

... Exportation, Use as Supplies on Vessels and Aircraft, or Transfer to a Foreign-Trade Zone § 28.141 General. (a...) Transfer to and deposit in a foreign-trade zone for exportation or for storage pending exportation. (b... foreign country; or (2) Transfer to and deposit in a foreign-trade zone for exportation or for storage...

27 CFR 28.141 - General.

Code of Federal Regulations, 2011 CFR

2011-04-01

... Exportation, Use as Supplies on Vessels and Aircraft, or Transfer to a Foreign-Trade Zone § 28.141 General. (a...) Transfer to and deposit in a foreign-trade zone for exportation or for storage pending exportation. (b... foreign country; or (2) Transfer to and deposit in a foreign-trade zone for exportation or for storage...

Heat exchanger with transpired, highly porous fins

DOEpatents

Kutscher, Charles F.; Gawlik, Keith

2002-01-01

The heat exchanger includes a fin and tube assembly with increased heat transfer surface area positioned within a hollow chamber of a housing to provide effective heat transfer between a gas flowing within the hollow chamber and a fluid flowing in the fin and tube assembly. A fan is included to force a gas, such as air, to flow through the hollow chamber and through the fin and tube assembly. The fin and tube assembly comprises fluid conduits to direct the fluid through the heat exchanger, to prevent mixing with the gas, and to provide a heat transfer surface or pathway between the fluid and the gas. A heat transfer element is provided in the fin and tube assembly to provide extended heat transfer surfaces for the fluid conduits. The heat transfer element is corrugated to form fins between alternating ridges and grooves that define flow channels for directing the gas flow. The fins are fabricated from a thin, heat conductive material containing numerous orifices or pores for transpiring the gas out of the flow channel. The grooves are closed or only partially open so that all or substantially all of the gas is transpired through the fins so that heat is exchanged on the front and back surfaces of the fins and also within the interior of the orifices, thereby significantly increasing the available the heat transfer surface of the heat exchanger. The transpired fins also increase heat transfer effectiveness of the heat exchanger by increasing the heat transfer coefficient by disrupting boundary layer development on the fins and by establishing other beneficial gas flow patterns, all at desirable pressure drops.

The augmentation of heat transfer in a pipe flow using a swirling perforated twisted (SPT) tape insert

NASA Astrophysics Data System (ADS)

Ahmad, Shahrokh; Oishe, Sadia Noon; Rahman, Md. Lutfor

2017-12-01

The purpose of this research work is to increase the heat transfer coefficient by operating the heat exchangers at smaller revolution per minute. This signifies an achievement of reduction of pressure drop corresponding to less operating cost. This study has used two types of SPT tape insert to observe the various heat transfer coefficient, heat transfer rate and heat transfer augmentation efficiency. One tape was fully twisted and another tape was partially twisted. The shape of the SPT tape creates turbulence effect. The turbulence flow (swirl flow) generated by SPT tape promotes greater mixing and high heat transfer coefficients. An arrangement scheme has been developed for the experimental investigation. For remarking the rate of change of heat transfer, temperature has been measured numerically through the temperature sensors with various flow rates and RPM. The volume flow rate was varied from 10.3448276 LPM to 21.045574 LPM and the rotation of the perforated twisted tape was varied from 50 RPM to 400 RPM. Finally the research study demonstrates the effectiveness of the results of the proposed approaches. It is observed that the suggested method of heat transfer augmentations is much more effective than existing methods, since it results in an increase in heat transfer area and also an increase in the heat transfer coefficient and reduction of cost in the industrial sectors.

Thermal-hydraulic analysis of low activity fusion blanket designs

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

Fillo, J A; Powell, J; Yu, W S

1977-01-01

The heat transfer aspects of fusion blankets are considered where: (a) conduction and (b) boiling and condensation are the dominant heat transfer mechanisms. In some cases, unique heat transfer problems arise and additional heat transfer data and analyses may be required.

Film-Cooling Heat-Transfer Measurements Using Liquid Crystals

NASA Technical Reports Server (NTRS)

Hippensteele, Steven A.

1997-01-01

The following topics are discussed: (1) The Transient Liquid-Crystal Heat-Transfer Technique; (2) 2-D Film-Cooling Heat-Transfer on an AlliedSignal Vane; and (3) Effects of Tab Vortex Generators on Surface Heat Transfer. Downstream of a Jet in Crossflow.

Investigation of two-phase heat transfer coefficients of argon-freon cryogenic mixed refrigerants

NASA Astrophysics Data System (ADS)

Baek, Seungwhan; Lee, Cheonkyu; Jeong, Sangkwon

2014-11-01

Mixed refrigerant Joule Thomson refrigerators are widely used in various kinds of cryogenic systems these days. Although heat transfer coefficient estimation for a multi-phase and multi-component fluid in the cryogenic temperature range is necessarily required in the heat exchanger design of mixed refrigerant Joule Thomson refrigerators, it has been rarely discussed so far. In this paper, condensation and evaporation heat transfer coefficients of argon-freon mixed refrigerant are measured in a microchannel heat exchanger. A Printed Circuit Heat Exchanger (PCHE) with 340 μm hydraulic diameter has been developed as a compact microchannel heat exchanger and utilized in the experiment. Several two-phase heat transfer coefficient correlations are examined to discuss the experimental measurement results. The result of this paper shows that cryogenic two-phase mixed refrigerant heat transfer coefficients can be estimated by conventional two-phase heat transfer coefficient correlations.

Effect of various refining processes for Kenaf Bast non-wood pulp fibers suspensions on heat transfer coefficient in circular pipe heat exchanger

NASA Astrophysics Data System (ADS)

Ahmed, Syed Muzamil; Kazi, S. N.; Khan, Ghulamullah; Sadri, Rad; Dahari, Mahidzal; Zubir, M. N. M.; Sayuti, M.; Ahmad, Pervaiz; Ibrahim, Rushdan

2018-03-01

Heat transfer coefficients were obtained for a range of non-wood kenaf bast pulp fiber suspensions flowing through a circular pipe heat exchanger test loop. The data were produced over a selected temperature and range of flow rates from the flow loop. It was found that the magnitude of the heat transfer coefficient of a fiber suspension is dependent on characteristics, concentration and pulping method of fiber. It was observed that at low concentration and high flow rates, the heat transfer coefficient values of suspensions were observed higher than that of the heat transfer coefficient values of water, on the other hand the heat transfer coefficient values of suspensions decreases at low flow rates and with the increase of their concentration. The heat transfer were affected by varying fiber characteristics, such as fiber length, fiber flexibility, fiber chemical and mechanical treatment as well as different pulping methods used to liberate the fibers. Heat transfer coefficient was decreased with the increase of fiber flexibility which was also observed by previous researchers. In the present work, the characteristics of fibers are correlated with the heat transfer coefficient of suspensions of the fibers. Deviations in fiber properties can be monitored from the flowing fiber suspensions by measuring heat transfer coefficient to adjust the degree of fiber refining treatment so that papers made from those fibers will be more uniform, consistent, within the product specification and retard the paper production loss.

Numerical Investigation on the Impact of Anode Change on Heat Transfer and Fluid Flow in Aluminum Smelting Cells

NASA Astrophysics Data System (ADS)

Wang, Qiang; Gosselin, Louis; Fafard, Mario; Peng, Jianping; Li, Baokuan

2016-04-01

In order to understand the impact of anode change on heat transfer and magnetohydrodynamic flow in aluminum smelting cells, a transient three-dimensional (3D) coupled mathematical model has been developed. The solutions of the mass, momentum, and energy conservation equations were simultaneously implemented by the finite volume method with full coupling of the Joule heating and Lorentz force through solving the electrical potential equation. The volume of fluid approach was employed to describe the two-phase flow. The phase change of molten electrolyte (bath) as well as molten aluminum (metal) was modeled by an enthalpy-based technique, where the mushy zone is treated as a porous medium with a porosity equal to the liquid fraction. The effect of the new anode temperature on recovery time was also analyzed. A reasonable agreement between the test data and simulated results is obtained. The results indicate that the temperature of the bath under cold anodes first decreases reaching the minimal value and rises under the effect of increasing Joule heating, and finally returns to steady state. The colder bath decays the velocity, and the around ledge becomes thicker. The lowest temperature of the bath below new anodes increases from 1118 K to 1143 K (845 °C to 870 °C) with the new anode temperature ranging from 298 K to 498 K (25°C to 225°C), and the recovery time reduces from 22.5 to 20 hours.

Ideal heat transfer conditions for tubular solar receivers with different design constraints

NASA Astrophysics Data System (ADS)

Kim, Jin-Soo; Potter, Daniel; Gardner, Wilson; Too, Yen Chean Soo; Padilla, Ricardo Vasquez

2017-06-01

The optimum heat transfer condition for a tubular type solar receiver was investigated for various receiver pipe size, heat transfer fluid, and design requirement and constraint(s). Heat transfer of a single plain receiver pipe exposed to concentrated solar energy was modelled along the flow path of the heat transfer fluid. Three different working fluids, molten salt, sodium, and supercritical carbon dioxide (sCO2) were considered in the case studies with different design conditions. The optimized ideal heat transfer condition was identified through fast iterative heat transfer calculations solving for all relevant radiation, conduction and convection heat transfers throughout the entire discretized tubular receiver. The ideal condition giving the best performance was obtained by finding the highest acceptable solar energy flux optimally distributed to meet different constraint(s), such as maximum allowable material temperature of receiver, maximum allowable film temperature of heat transfer fluid, and maximum allowable stress of receiver pipe material. The level of fluid side turbulence (represented by pressure drop in this study) was also optimized to give the highest net power production. As the outcome of the study gives information on the most ideal heat transfer condition, it can be used as a useful guideline for optimal design of a real receiver and solar field in a combined manner. The ideal heat transfer condition is especially important for high temperature tubular receivers (e.g. for supplying heat to high efficiency Brayton cycle turbines) where the system design and performance is tightly constrained by the receiver pipe material strength.

The contact heat transfer between the heating plate and granular materials in rotary heat exchanger under overloaded condition

NASA Astrophysics Data System (ADS)

Duan, Luanfang; Qi, Chonggang; Ling, Xiang; Peng, Hao

2018-03-01

In the present work, the contact heat transfer between the granular materials and heating plates inside plate rotary heat exchanger (PRHE) was investigated. The heat transfer coefficient is dominated by the contact heat transfer coefficient at hot wall surface of the heating plates and the heat penetration inside the solid bed. A plot scale PRHE with a diameter of Do = 273 mm and a length of L = 1000 mm has been established. Quartz sand with dp = 2 mm was employed as the experimental material. The operational parameters were in the range of ω = 1 - 8 rpm, and F = 15, 20, 25, 30%, and the effect of these parameters on the time-average contact heat transfer coefficient was analyzed. The time-average contact heat transfer coefficient increases with the increase of rotary speed, but decreases with the increase of the filling degree. The measured data of time-average heat transfer coefficients were compared with theoretical calculations from Schlünder's model, a good agreement between the measurements and the model could be achieved, especially at a lower rotary speed and filling degree level. The maximum deviation between the calculated data and the experimental data is approximate 10%.

Emergency heat removal system for a nuclear reactor

DOEpatents

Dunckel, Thomas L.

1976-01-01

A heat removal system for nuclear reactors serving as a supplement to an Emergency Core Cooling System (ECCS) during a Loss of Coolant Accident (LOCA) comprises a plurality of heat pipes having one end in heat transfer relationship with either the reactor pressure vessel, the core support grid structure or other in-core components and the opposite end located in heat transfer relationship with a heat exchanger having heat transfer fluid therein. The heat exchanger is located external to the pressure vessel whereby excessive core heat is transferred from the above reactor components and dissipated within the heat exchanger fluid.

Gravel bar thermal variability and its potential consequences for CO2 evasion from Alpine coldwater streams

NASA Astrophysics Data System (ADS)

Boodoo, Kyle; Battin, Tom; Schelker, Jakob

2017-04-01

Gravel bars (GB) are ubiquitous in-stream structures with relatively large exposed surfaces, capable of absorbing heat and possibly acting as a heat source to the underlying hyporheic zone (HZ). The distinctive mixing of groundwater and surface water within their HZ largely determines its characteristic physical and biogeochemical properties, including temperature distribution. To study thermal variability within GBs and its possible consequences for CO2 evasion fluxes we analysed high frequency spatio-temporal data for a range of stream and atmospheric physical parameters including the vertical GB temperature, in an Alpine cold water stream (Oberer Seebach, Austria) over the course of a year. We found the vertical temperature profiles within the GB to vary seasonally and with discharge. We extended our study to 13 other gravel bars of varying physical characteristics within the surrounding Ybbs and Erlauf catchments, conducting diurnal spot samplings in summer 2016. Temperatures within the observed permanently wetted hyporheic zone (-56 to -100cm depth below GB surface) of the OSB, were warmer than both end members, surface water and groundwater >18% of the year, particularly during summer. There was a general increase in exceedance within the periodically wetted gravel bar sediment toward the gravel bar surface, further evidencing downward heat transfer to the wetted HZ. Average CO2 flux from the GB was significantly higher than that of streamwater during summer and winter, with significantly higher temperatures and CO2 outgassing rates occurring at the GB tail as compared to streamwater and the head and mid of the GB throughout the year. Higher cumulative (over 6 h) GB seasonal temperatures were associated with increased CO2 evasion fluxes within the OSB, particularly during summer. This enhanced CO2 flux may result from the input of warmer CO2-rich groundwater into the HZ in autumn, while downward heat transfer in summer may enhance GB metabolism and therefore CO2 evasion. Furthermore, catchment CO2 outgassing fluxes significantly exceeded that of the stream, with higher diurnal CO2 outgassing fluxes observed for all 13 GBs within the Ybbs and Erlauf catchments as compared to their respective streams. We found DOC concentration did not significantly correlate to CO2 outgassing. But, vertical temperature gradient as a measure of heat flux to the hyporheic zone explained 55% and 69% of the variability in observed CO2 efflux from the OSB gravel bar (seasonal samplings during summer 2015 - winter 2016) and 11 catchment gravel bars (2 GBs excluded due to equipment malfunction) respectively. These results highlight the effect of temperature on physical and biochemical stream processes, particularly in cold-water streams, due to the occurrence of more frequent and intense warm temperature events, as well as altered flow regimes, likely consequences of climatic change.

Hydrogen isotope geochemistry and heat balance of a fumarolic system: Kudriavy volcano, Kuriles

NASA Astrophysics Data System (ADS)

Botcharnikov, Roman E.; Shmulovich, Kirill I.; Tkachenko, Sergey I.; Korzhinsky, Mikhail A.; Rybin, Alexander V.

2003-05-01

The temperature and hydrogen isotope composition of the fumarolic gases have been studied at Kudriavy volcano, Kurile Islands, which is unique for investigating the processes of magma degassing because of the occurrence of numerous easily accessible fumaroles with a temperature range of 100-940°C. There are several local fumarolic fields with a total surface area of about 2600 m 2 within the flattened crater of 200×600 m. Each fumarolic field is characterized by the occurrence of high- and low-temperature fumaroles with high gas discharges and steaming areas with lower temperatures. We have studied the thermal budget of the Kudriavy fumarolic system on the basis of the quantitative dependences of the hydrogen isotope ratio (D/H) and tritium concentration on the temperature of fumarolic gases and compared them with the calculated heat balance of mixing between hot magmatic gas and cold meteoric water. Hydrogen isotope composition (δD and 3H) shows a well expressed correlation with the gas temperature. Since D/H ratio and 3H are good indicators of water sources in volcanic areas, it suggests that the thermal budget of the fumarolic system is mostly controlled by the admixing of meteoric waters to magmatic gases. The convective mechanism of heat transfer in the hydrothermal system governs the maximum temperatures of local fumaroles and fumarolic fields. Low-temperature fumaroles at Kudriavy are thermally buffered by the boiling processes of meteoric waters in the mixing zone at pressures of 3-12 bar. These values may correspond to the hydrostatic pressure of water columns about 30-120 m in height in the volcanic edifice and hence to the depth of a mixing/boiling zone. Conductive heat transfer is governed by conductive heat exchange between gases and country rocks and appears to be responsible for the temperature distribution around a local fumarolic vent. The temperature and pressure of shallow degassing magma are estimated to be 1050°C and 2-3 bar, respectively. The length of the 'main' fumarolic gas conduit is estimated to be about 80 m from the linear correlation between maximal temperatures of fumarolic fields and distances to the highest-temperature 'F-940' fumarole. This value may correspond to the depth of an apical part of the magmatic chamber. The geometry of the crater zone at the Kudriavy summit and the model of convective gas cooling suggest different hydrostatic pressures in the hydrothermal system at the base of high- and low-temperature gas conduits. The depths of gas sources for low-temperature fumaroles are evaluated to be about 200 m at the periphery of the magma chamber.

Flow and heat transfer in a curved channel

NASA Technical Reports Server (NTRS)

Brinich, P. F.; Graham, R. W.

1977-01-01

Flow and heat transfer in a curved channel of aspect ratio 6 and inner- to outer-wall radius ratio 0.96 were studied. Secondary currents and large longitudinal vortices were found. The heat-transfer rates of the outer and inner walls were independently controlled to maintain a constant wall temperature. Heating the inner wall increased the pressure drop along the channel length, whereas heating the outer wall had little effect. Outer-wall heat transfer was as much as 40 percent greater than the straight-channel correlation, and inner-wall heat transfer was 22 percent greater than the straight-channel correlation.

Emergency cooling system and method

DOEpatents

Oosterkamp, W.J.; Cheung, Y.K.

1994-01-04

An improved emergency cooling system and method are disclosed that may be adapted for incorporation into or use with a nuclear BWR wherein a reactor pressure vessel (RPV) containing a nuclear core and a heat transfer fluid for circulation in a heat transfer relationship with the core is housed within an annular sealed drywell and is fluid communicable therewith for passage thereto in an emergency situation the heat transfer fluid in a gaseous phase and any noncondensibles present in the RPV, an annular sealed wetwell houses the drywell, and a pressure suppression pool of liquid is disposed in the wetwell and is connected to the drywell by submerged vents. The improved emergency cooling system and method has a containment condenser for receiving condensible heat transfer fluid in a gaseous phase and noncondensibles for condensing at least a portion of the heat transfer fluid. The containment condenser has an inlet in fluid communication with the drywell for receiving heat transfer fluid and noncondensibles, a first outlet in fluid communication with the RPV for the return to the RPV of the condensed portion of the heat transfer fluid and a second outlet in fluid communication with the drywell for passage of the noncondensed balance of the heat transfer fluid and the noncondensibles. The noncondensed balance of the heat transfer fluid and the noncondensibles passed to the drywell from the containment condenser are mixed with the heat transfer fluid and the noncondensibles from the RPV for passage into the containment condenser. A water pool is provided in heat transfer relationship with the containment condenser and is thermally communicable in an emergency situation with an environment outside of the drywell and the wetwell for conducting heat transferred from the containment condenser away from the wetwell and the drywell. 5 figs.

A new leakage measurement method for damaged seal material

NASA Astrophysics Data System (ADS)

Wang, Shen; Yao, Xue Feng; Yang, Heng; Yuan, Li; Dong, Yi Feng

2018-07-01

In this paper, a new leakage measurement method based on the temperature field and temperature gradient field is proposed for detecting the leakage location and measuring the leakage rate in damaged seal material. First, a heat transfer leakage model is established, which can calculate the leakage rate based on the temperature gradient field near the damaged zone. Second, a finite element model of an infinite plate with a damaged zone is built to calculate the leakage rate, which fits the simulated leakage rate well. Finally, specimens in a tubular rubber seal with different damage shapes are used to conduct the leakage experiment, validating the correctness of this new measurement principle for the leakage rate and the leakage position. The results indicate the feasibility of the leakage measurement method for damaged seal material based on the temperature gradient field from infrared thermography.

46 CFR 153.434 - Heat transfer coils within a tank.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 5 2014-10-01 2014-10-01 false Heat transfer coils within a tank. 153.434 Section 153... Cargo Temperature Control Systems § 153.434 Heat transfer coils within a tank. When a cargo tank... the heat transfer fluid at a pressure greater than the pressure exerted on the heating or cooling...

46 CFR 153.434 - Heat transfer coils within a tank.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 5 2013-10-01 2013-10-01 false Heat transfer coils within a tank. 153.434 Section 153... Cargo Temperature Control Systems § 153.434 Heat transfer coils within a tank. When a cargo tank... the heat transfer fluid at a pressure greater than the pressure exerted on the heating or cooling...

46 CFR 153.434 - Heat transfer coils within a tank.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 5 2010-10-01 2010-10-01 false Heat transfer coils within a tank. 153.434 Section 153... Cargo Temperature Control Systems § 153.434 Heat transfer coils within a tank. When a cargo tank... the heat transfer fluid at a pressure greater than the pressure exerted on the heating or cooling...

46 CFR 153.434 - Heat transfer coils within a tank.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 5 2011-10-01 2011-10-01 false Heat transfer coils within a tank. 153.434 Section 153... Cargo Temperature Control Systems § 153.434 Heat transfer coils within a tank. When a cargo tank... the heat transfer fluid at a pressure greater than the pressure exerted on the heating or cooling...

Experimental investigation of heat transfer of R134a in pool boiling on stainless steel and aluminum tubes

NASA Astrophysics Data System (ADS)

Wengler, C.; Addy, J.; Luke, A.

2018-03-01

Due to high energy demand required for chemical processes, refrigeration and process industries the increase of efficiency and performance of thermal systems especially evaporators is indispensable. One of the possibilities to meet this purpose are investigations in enhancement of the heat transfer in nucleate boiling where high heat fluxes at low superheat are transferred. In the present work, the heat transfer in pool boiling is investigated with pure R134a over wide ranges of reduced pressures and heat fluxes. The heating materials of the test tubes are aluminum and stainless steel. The influence of the thermal conductivity on the heat transfer coefficients is analysed by the surface roughness of sandblasted surfaces. The heat transfer coefficient increases with increasing thermal conductivity, surface roughness and reduced pressures. The experimental results show a small degradation of the heat transfer coefficients between the two heating materials aluminum and stainless steel. In correlation with the VDI Heat Atlas, the experimental results are matching well with the predictions but do not accurately consider the stainless steel material reference properties.

Disk brake design for cooling improvement using Computational Fluid Dynamics (CFD)

NASA Astrophysics Data System (ADS)

Munisamy, Kannan M.; Shafik, Ramel

2013-06-01

The car disk brake design is improved with two different blade designs compared to the baseline blade design. The two designs were simulated in Computational fluid dynamics (CFD) to obtain heat transfer properties such as Nusselt number and Heat transfer coefficient. The heat transfer property is compared against the baseline design. The improved shape has the highest heat transfer performance. The curved design is inferior to baseline design in heat transfer performance.

Experimental study on heat transfer performance of fin-tube exchanger and PSHE for waste heat recovery

NASA Astrophysics Data System (ADS)

Chen, Ting; Bae, Kyung Jin; Kwon, Oh Kyung

2018-02-01

In this paper, heat transfer characteristics of fin-tube heat exchanger and primary surface heat exchanger (PSHE) used in waste heat recovery were investigated experimentally. The flow in the fin-tube heat exchanger is cross flow and in PSHE counter flow. The variations of friction factor and Colburn j factor with air mass flow rate, and Nu number with Re number are presented. Various comparison methods are used to evaluate heat transfer performance, and the results show that the heat transfer rate of the PSHE is on average 17.3% larger than that of fin-tube heat exchanger when air mass flow rate is ranging from 1.24 to 3.45 kg/min. However, the PSHE causes higher pressure drop, and the fin-tube heat exchanger has a wider application range which leads to a 31.7% higher value of maximum heat transfer rate compared to that of the PSHE. Besides, under the same fan power per unit frontal surface, a higher heat transfer rate value is given in the fin-tube heat exchanger.

Automated GMA welding of austenitic stainless steel pipe

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

Tahash, G.J.

1996-12-31

The study focused on reducing weld cycle times of rotatable subassemblies (spools) using automated welding equipment. A unique automatic Gas Metal Arc Welding (GMAW) system was used to produce a series of pipe to pipe welds on 141 mm (5 in.) schedule 80 seamless stainless steel pipe. After manual tack welding, the adaptive control system welded the root pass of the argon gas backed open vee groove circumferential butt joints in the IG rotated position with short circuiting transfer GMAW. The fill and cover passes were welded automatically with spray transfer GMAW. Automatic welding cycle times were found to bemore » 50--80 percent shorter than the current techniques of roll welding with Shielded Metal Arc Welding and manual Gas Tungsten Arc Welding. Weld costs ({Brit_pounds}/m), including amortization, for the various systems were compared. The cost of automated GMA welds was virtually equivalent to the most competitive methods while depositing 75% more filler metal per year. Also investigated were metallurgical effects generated by weld thermal cycling, and the associated effects on mechanical properties of the weld joint. Mechanical properties of the welds met or exceeded those of the base metal. Sensitization of the pipe did not occur in the heat affected zone (HAZ), based on the absence of evidence of intergranular attack in modified Strauss corrosion tests and despite the fact of interpass temperatures well above recommended maximums. Cooling rates of 3--5 C/s in the heat affected zone of the four pass welds were measured by thermocouple technique and found to be within the non-sensitizing range for this alloy.« less

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

Solid oxide fuel cell systems with hot zones having improved reactant distribution

DOEpatents

Poshusta, Joseph C.; Booten, Charles W.; Martin, Jerry L.

2012-11-06

A Solid Oxide Fuel Cell (SOFC) system having a hot zone with a center cathode air feed tube for improved reactant distribution, a CPOX reactor attached at the anode feed end of the hot zone with a tail gas combustor at the opposing end for more uniform heat distribution, and a counter-flow heat exchanger for efficient heat retention.

Solid oxide fuel cell systems with hot zones having improved reactant distribution

DOEpatents

Poshusta, Joseph C; Booten, Charles W; Martin, Jerry L

2013-12-24

A Solid Oxide Fuel Cell (SOFC) system having a hot zone with a center cathode air feed tube for improved reactant distribution, a CPOX reactor attached at the anode feed end of the hot zone with a tail gas combustor at the opposing end for more uniform heat distribution, and a counter-flow heat exchanger for efficient heat retention.

Solid oxide fuel cell systems with hot zones having improved reactant distribution

DOEpatents

Poshusta, Joseph C.; Booten, Charles W.; Martin, Jerry L.

2016-05-17

A Solid Oxide Fuel Cell (SOFC) system having a hot zone with a center cathode air feed tube for improved reactant distribution, a CPOX reactor attached at the anode feed end of the hot zone with a tail gas combustor at the opposing end for more uniform heat distribution, and a counter-flow heat exchanger for efficient heat retention.

Enhanced MicroChannel Heat Transfer in Macro-Geometry using Conventional Fabrication Approach

NASA Astrophysics Data System (ADS)

Ooi, KT; Goh, AL

2016-09-01

This paper presents studies on passive, single-phase, enhanced microchannel heat transfer in conventionally sized geometry. The intention is to allow economical, simple and readily available conventional fabrication techniques to be used for fabricating macro-scale heat exchangers with microchannel heat transfer capability. A concentric annular gap between a 20 mm diameter channel and an 19.4 mm diameter insert forms a microchannel where heat transfer occurs. Results show that the heat transfer coefficient of more than 50 kW/m·K can be obtained for Re≈4,000, at hydraulic diameter of 0.6 mm. The pressure drop values of the system are kept below 3.3 bars. The present study re-confirms the feasibility of fabricating macro-heat exchangers with microchannel heat transfer capability.

Principles and working mechanisms of water-filtered infrared-A (wIRA) in relation to wound healing

PubMed Central

Hoffmann, Gerd

2007-01-01

The experience of the pleasant heat of the sun in moderate climatic zones arises from the filtering of the heat radiation of the sun by water vapor in the atmosphere of the earth. The filter effect of water decreases those parts of infrared radiation (most parts of infrared-B and -C and the absorption bands of water within infrared-A), which would cause – by reacting with water molecules in the skin – only an undesired thermal load to the surface of the skin. Technically water-filtered infrared-A (wIRA) is produced in special radiators, whose full spectrum of radiation of a halogen bulb is passed through a cuvette, containing water, which absorbs or decreases the described undesired wavelengths of the infrared radiation. Within infrared the remaining wIRA (within 780-1400 nm) mainly consists of radiation with good penetration properties into tissue and therefore allows – compared to unfiltered heat radiation – a multiple energy transfer into tissue without irritating the skin, similar to the sun’s heat radiation in moderate climatic zones. Typical wIRA radiators emit no ultraviolet (UV) radiation and nearly no infrared-B and -C radiation and the amount of infrared-A radiation in relation to the amount of visible light (380-780 nm) is emphasized. Water-filtered infrared-A as a special form of heat radiation with a high tissue penetration and with a low thermal load to the skin surface acts both by thermal (related to heat energy transfer) and thermic (temperature depending, with a relevant change of temperature) as well as by non-thermal (without a relevant transfer of heat energy) and non-thermic (not depending on temperature, without a relevant change of temperature) effects. wIRA produces a therapeutically usable field of heat in the tissue and increases tissue temperature, tissue oxygen partial pressure, and tissue perfusion. These three factors are vital for a sufficient tissue supply with energy and oxygen. As wound healing and infection defense (e.g. granulocyte function including their antibacterial oxygen radical formation) depend decisively on a sufficient supply with energy and oxygen, one explanation for the good clinical effect of wIRA on wounds and wound infections can be the improvement of both the energy supply per time (increase of metabolic rate) and the oxygen supply. In addition wIRA has non-thermal and non-thermic effects, which are based on putting direct stimuli on cells and cellular structures. wIRA can considerably alleviate the pain (with remarkably less need for analgesics) and diminish an elevated wound exudation and inflammation and can show positive immunomodulatory effects. wIRA can advance wound healing or improve an impaired wound healing both in acute and in chronic wounds including infected wounds. Even the normal wound healing process can be improved. wIRA is contact-free, easily applied, without discomfort to the patient, with absent consumption of material and with a good effect in the depth. The irradiation of the typically uncovered wound is carried out with a wIRA radiator. PMID:20204085

Corrosion-Resistant Container for Molten-Material Processing

NASA Technical Reports Server (NTRS)

Stern, Theodore G.; McNaul, Eric

2010-01-01

In a carbothermal process, gaseous methane is passed over molten regolith, which is heated past its melting point to a temperature in excess of 1,625 C. At this temperature, materials in contact with the molten regolith (or regolith simulant) corrode and lose their structural properties. As a result, fabricating a crucible to hold the molten material and providing a method of contact heating have been problematic. Alternative containment approaches use a large crucible and limit the heat zone of the material being processed, which is inefficient because of volume and mass constraints. Alternative heating approaches use non-contact heating, such as by laser or concentrated solar energy, which can be inefficient in transferring heat and thus require higher power heat sources to accomplish processing. The innovation is a combination of materials, with a substrate material having high structural strength and stiffness and high-temperature capability, and a coating material with a high corrosion resistance and high-temperature capability. The material developed is a molybdenum substrate with an iridium coating. Creating the containment crucible or heater jacket using this material combination requires only that the molybdenum, which is easily processed by conventional methods such as milling, electric discharge machining, or forming and brazing, be fabricated into an appropriate shape, and that the iridium coating be applied to any surfaces that may come in contact with the corrosive molten material. In one engineering application, the molybdenum was fashioned into a container for a heat pipe. Since only the end of the heat pipe is used to heat the regolith, the container has a narrowing end with a nipple in which the heat pipe is snugly fit, and the external area of this nipple, which contacts the regolith to transfer heat into it, is coated with iridium. At the time of this reporting, no single material has been found that can perform the functions of this combination of materials, and other combinations of materials have not proven to be survivable to the corrosiveness of this environment. High-temperature processing of materials with similar constituencies as lunar regolith is fairly common. The carbo-thermal process is commonly used to make metallurgical-grade silicon for the semiconductor and solar-cell industries.

Experimental and Computational Investigations of Phase Change Thermal Energy Storage Canisters

NASA Technical Reports Server (NTRS)

Ibrahim, Mounir; Kerslake, Thomas; Sokolov, Pavel; Tolbert, Carol

1996-01-01

Two sets of experimental data are examined in this paper, ground and space experiments, for cylindrical canisters with thermal energy storage applications. A 2-D computational model was developed for unsteady heat transfer (conduction and radiation) with phase-change. The radiation heat transfer employed a finite volume method. The following was found in this study: (1) Ground Experiments: the convection heat transfer is equally important to that of the radiation heat transfer; radiation heat transfer in the liquid is found to be more significant than that in the void; including the radiation heat transfer in the liquid resulted in lower temperatures (about 15 K) and increased the melting time (about 10 min.); generally, most of the heat flow takes place in the radial direction. (2) Space Experiments: radiation heat transfer in the void is found to be more significant than that in the liquid (exactly the opposite to the Ground Experiments); accordingly, the location and size of the void affects the performance considerably; including the radiation heat transfer in the void resulted in lower temperatures (about 40 K).

Heat transfer unit and method for prefabricated vessel

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

Tamburello, David A.; Kesterson, Matthew R; Hardy, Bruce J.

Vessel assemblies, heat transfer units for prefabricated vessels, and methods for heat transfer prefabricated vessel are provided. A heat transfer unit includes a central rod, and a plurality of peripheral rods surrounding the central rod and connected to the central rod. The plurality of peripheral rods are movable between a first collapsed position and a second bowed position, wherein in the second bowed position a midpoint of each of the plurality of peripheral rods is spaced from the central rod relative to in the first position. The heat transfer unit further includes a heat transfer element connected to one ofmore » the plurality of peripheral rods.« less

Model wall and recovery temperature effects on experimental heat transfer data analysis

NASA Technical Reports Server (NTRS)

Throckmorton, D. A.; Stone, D. R.

1974-01-01

Basic analytical procedures are used to illustrate, both qualitatively and quantitatively, the relative impact upon heat transfer data analysis of certain factors which may affect the accuracy of experimental heat transfer data. Inaccurate knowledge of adiabatic wall conditions results in a corresponding inaccuracy in the measured heat transfer coefficient. The magnitude of the resulting error is extreme for data obtained at wall temperatures approaching the adiabatic condition. High model wall temperatures and wall temperature gradients affect the level and distribution of heat transfer to an experimental model. The significance of each of these factors is examined and its impact upon heat transfer data analysis is assessed.

Experimental estimation of convective heat transfer coefficient from pulsating semi-confined impingement air slot jet by using inverse method

NASA Astrophysics Data System (ADS)

Farahani, Somayeh Davoodabadi; Kowsary, Farshad

2017-09-01

An experimental study on pulsating impingement semi-confined slot jet has been performed. The effect of pulsations frequency was examined for various Reynolds numbers and Nozzle to plate distances. Convective heat transfer coefficient is estimated using the measured temperatures in the target plate and conjugate gradient method with adjoint equation. Heat transfer coefficient in Re < 3000 tended to increase with increasing frequency. The pulsations enhance mixing, which results in an enhancement of mean flow velocity. In case of turbulent jet (Re > 3000), heat transfer coefficient is affected by the pulsation from particular frequency. In this study, the threshold Strouhal number (St) is 0.11. No significant heat transfer enhancement was obtained for St < 0.11. The thermal resistance is smaller each time due to the newly forming thermal boundary layers. Heat transfer coefficient increases due to decrease thermal resistance. This study shows that maximum enhancement in heat transfer due to pulsations occurs in St = 0.169. Results show the configuration geometry has an important effect on the heat transfer performances in pulsed impinging jet. Heat transfer enhancement can be described to reflect flow by the confinement plate.

On the competing affects of shear heating and grainsize reduction in lithospheric shear zone formation

NASA Astrophysics Data System (ADS)

Foley, B. J.

2017-12-01

Grain-size reduction is thought to play an important role in shear localization within the lithosphere, as mylonites are commonly seen in regions that have undergone intense deformation. However, flow in lithospheric shear zones can also cause heating due to the energy dissipated by deformation. As grain growth is strongly enhanced by warmer temperatures, shear heating may impede grainsize reduction and the formation of mylonite zones. I use models of simple shear, with length-scales representative of lithospheric shear zones and plate boundaries, including shear heating and grainsize evolution. Grain-damage theory is used to represent the evolution of grainsize. The models are used to determine conditions where grainsize reduction dominates versus those where shear heating dominates; if grainsize reduction dominates, then heating is held in check by the drop in viscosity brought about by small grains. On the other hand, if heating dominates then grain-reduction is prevented by fast grain-growth rates. From the numerical models, simple scaling laws are developed that give the stready-state grainsize and temperature rise as a function of strain-rate, background temperature, and parameters for grain-growth and grain-reduction. I find that for parameter ranges constrained by field observations of shear zones and rock deformation experiments, grainsize reduction dominated over shear heating. Very high strain-rates or driving stresses, above what is typically expected in natural shear zones, are needed for shear heating to dominate over grainsize reduction. Also explored is the timescale to reach steady-state grainsize and temperature conditions in a shear zone. For realistic driving stress or strain-rate, timescales to reach steady-state are often very long, on the order of hundreds of millions of years or longer. This might indicate that natural shear zones do not reach steady-state, or that additional processes are important in initiating lithospheric shear localization.

Fuel Reforming Technologies (BRIEFING SLIDES)

DTIC Science & Technology

2009-09-01

Heat and Mass Transfer , Catalysis...Gallons Of Fuel/Day/1100men Deployment  To Reduce Noise/Thermal Signature And 4 Environmental Emissions Advanced Heat and Mass Transfer 5 Advanced... Heat and Mass & Transfer Technologies Objective Identify And Develop New Technologies To Enhance Heat And Mass Transfer In Deployed Energy

Analysis for Heat Transfer in a High Current-Passing Carbon Nanosphere Using Nontraditional Thermal Transport Model.

PubMed

Hol C Y; Chen, B C; Tsai, Y H; Ma, C; Wen, M Y

2015-11-01

This paper investigates the thermal transport in hollow microscale and nanoscale spheres subject to electrical heat source using nontraditional thermal transport model. Working as supercapacitor electrodes, carbon hollow micrometer- and nanometer-sized spheres needs excellent heat transfer characteristics to maintain high specific capacitance, long cycle life, and high power density. In the nanoscale regime, the prediction of heat transfer from the traditional heat conduction equation based on Fourier's law deviates from the measured data. Consequently, the electrical heat source-induced heat transfer characteristics in hollow micrometer- and nanometer-sized spheres are studied using nontraditional thermal transport model. The effects of parameters on heat transfer in the hollow micrometer- and nanometer-sized spheres are discussed in this study. The results reveal that the heat transferred into the spherical interior, temperature and heat flux in the hollow sphere decrease with the increasing Knudsen number when the radius of sphere is comparable to the mean free path of heat carriers.

Suppression of the sonic heat transfer limit in high-temperature heat pipes

NASA Astrophysics Data System (ADS)

Dobran, Flavio

1989-08-01

The design of high-performance heat pipes requires optimization of heat transfer surfaces and liquid and vapor flow channels to suppress the heat transfer operating limits. In the paper an analytical model of the vapor flow in high-temperature heat pipes is presented, showing that the axial heat transport capacity limited by the sonic heat transfer limit depends on the working fluid, vapor flow area, manner of liquid evaporation into the vapor core of the evaporator, and lengths of the evaporator and adiabatic regions. Limited comparisons of the model predictions with data of the sonic heat transfer limits are shown to be very reasonable, giving credibility to the proposed analytical approach to determine the effect of various parameters on the axial heat transport capacity. Large axial heat transfer rates can be achieved with large vapor flow cross-sectional areas, small lengths of evaporator and adiabatic regions or a vapor flow area increase in these regions, and liquid evaporation in the evaporator normal to the main flow.

Effects of rotation on coolant passage heat transfer. Volume 1: Coolant passages with smooth walls

NASA Technical Reports Server (NTRS)

Hajek, T. J.; Wagner, J. H.; Johnson, B. V.; Higgins, A. W.; Steuber, G. D.

1991-01-01

An experimental program was conducted to investigate heat transfer and pressure loss characteristics of rotating multipass passages, for configurations and dimensions typical of modern turbine blades. The immediate objective was the generation of a data base of heat transfer and pressure loss data required to develop heat transfer correlations and to assess computational fluid dynamic techniques for rotating coolant passages. Experiments were conducted in a smooth wall large scale heat transfer model.

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

Study of a high performance evaporative heat transfer surface

NASA Technical Reports Server (NTRS)

Saaski, E. W.; Hamasaki, R. H.

1977-01-01

An evaporative surface is described for heat pipes and other two-phase heat transfer applications that consists of a hybrid composition of V-grooves and capillary wicking. Characteristics of the surface include both a high heat transfer coefficient and high heat flux capability relative to conventional open-faced screw thread surfaces. With a groove density of 12.6 cm/1 and ammonia working fluid, heat transfer coefficients in the range of 1 to 2 W/sq cm have been measured along with maximum heat flux densities in excess of 20 W/sq cm. A peak heat transfer coefficient in excess of 2.3 W/sq cm was measured with a 37.8 cm/1 hybrid surface.

Method and apparatus for obtaining enhanced production rate of thermal chemical reactions

DOEpatents

Tonkovich, Anna Lee Y [Pasco, WA; Wang, Yong [Richland, WA; Wegeng, Robert S [Richland, WA; Gao, Yufei [Kennewick, WA

2003-04-01

The present invention is a method and apparatus (vessel) for providing a heat transfer rate from a reaction chamber through a wall to a heat transfer chamber substantially matching a local heat transfer rate of a catalytic thermal chemical reaction. The key to the invention is a thermal distance defined on a cross sectional plane through the vessel inclusive of a heat transfer chamber, reaction chamber and a wall between the chambers. The cross sectional plane is perpendicular to a bulk flow direction of the reactant stream, and the thermal distance is a distance between a coolest position and a hottest position on the cross sectional plane. The thermal distance is of a length wherein the heat transfer rate from the reaction chamber to the heat transfer chamber substantially matches the local heat transfer rate.

Improving the growth of CZT crystals for radiation detectors: a modeling perspective

NASA Astrophysics Data System (ADS)

Derby, Jeffrey J.; Zhang, Nan; Yeckel, Andrew

2012-10-01

The availability of large, single crystals of cadmium zinc telluride (CZT) with uniform properties is key to improving the performance of gamma radiation detectors fabricated from them. Towards this goal, we discuss results obtained by computational models that provide a deeper understanding of crystal growth processes and how the growth of CZT can be improved. In particular, we discuss methods that may be implemented to lessen the deleterious interactions between the ampoule wall and the growing crystal via engineering a convex solidification interface. For vertical Bridgman growth, a novel, bell-curve furnace temperature profile is predicted to achieve macroscopically convex solid-liquid interface shapes during melt growth of CZT in a multiple-zone furnace. This approach represents a significant advance over traditional gradient-freeze profiles, which always yield concave interface shapes, and static heat transfer designs, such as pedestal design, that achieve convex interfaces over only a small portion of the growth run. Importantly, this strategy may be applied to any Bridgman configuration that utilizes multiple, controllable heating zones. Realizing a convex solidification interface via this adaptive bell-curve furnace profile is postulated to result in better crystallinity and higher yields than conventional CZT growth techniques.

Modeling of Blast Furnace with Layered Cohesive Zone

NASA Astrophysics Data System (ADS)

Dong, X. F.; Yu, A. B.; Chew, S. J.; Zulli, P.

2010-04-01

An ironmaking blast furnace (BF) is a moving bed reactor involving counter-, co-, and cross-current flows of gas, powder, liquids, and solids, coupled with heat exchange and chemical reactions. The behavior of multiple phases directly affects the stability and productivity of the furnace. In the present study, a mathematical model is proposed to describe the behavior of fluid flow, heat and mass transfer, as well as chemical reactions in a BF, in which gas, solid, and liquid phases affect each other through interaction forces, and their flows are competing for the space available. Process variables that characterize the internal furnace state, such as reduction degree, reducing gas and burden concentrations, as well as gas and condensed phase temperatures, have been described quantitatively. In particular, different treatments of the cohesive zone (CZ), i.e., layered, isotropic, and anisotropic nonlayered, are discussed, and their influence on simulation results is compared. The results show that predicted fluid flow and thermochemical phenomena within and around the CZ and in the lower part of the BF are different for different treatments. The layered CZ treatment corresponds to the layered charging of burden and naturally can predict the CZ as a gas distributor and liquid generator.

Radiative heat transfer in strongly forward scattering media of circulating fluidized bed combustors

NASA Astrophysics Data System (ADS)

Ates, Cihan; Ozen, Guzide; Selçuk, Nevin; Kulah, Gorkem

2016-10-01

Investigation of the effect of particle scattering on radiative incident heat fluxes and source terms is carried out in the dilute zone of the lignite-fired 150 kWt Middle East Technical University Circulating Fluidized Bed Combustor (METU CFBC) test rig. The dilute zone is treated as an axisymmetric cylindrical enclosure containing grey/non-grey, absorbing, emitting gas with absorbing, emitting non/isotropically/anisotropically scattering particles surrounded by grey diffuse walls. A two-dimensional axisymmetric radiation model based on Method of Lines (MOL) solution of Discrete Ordinates Method (DOM) coupled with Grey Gas (GG)/Spectral Line-Based Weighted Sum of Grey Gases Model (SLW) and Mie theory/geometric optics approximation (GOA) is extended for incorporation of anisotropic scattering by using normalized Henyey-Greenstein (HG)/transport approximation for the phase function. Input data for the radiation model is obtained from predictions of a comprehensive model previously developed and benchmarked against measurements on the same CFBC burning low calorific value indigenous lignite with high volatile matter/fixed carbon (VM/FC) ratio in its own ash. Predictive accuracy and computational efficiency of nonscattering, isotropic scattering and forward scattering with transport approximation are tested by comparing their predictions with those of forward scattering with HG. GG and GOA based on reflectivity with angular dependency are found to be accurate and CPU efficient. Comparisons reveal that isotropic assumption leads to under-prediction of both incident heat fluxes and source terms for which discrepancy is much larger. On the other hand, predictions obtained by neglecting scattering were found to be in favorable agreement with those of forward scattering at significantly less CPU time. Transport approximation is as accurate and CPU efficient as HG. These findings indicate that negligence of scattering is a more practical choice in solution of the radiative transfer equation (RTE) in conjunction with conservation equations for the system under consideration.

Heat extraction from salinity-gradient solar ponds using heat pipe heat exchangers

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

Tundee, Sura; Terdtoon, Pradit; Sakulchangsatjatai, Phrut

This paper presents the results of experimental and theoretical analysis on the heat extraction process from solar pond by using the heat pipe heat exchanger. In order to conduct research work, a small scale experimental solar pond with an area of 7.0 m{sup 2} and a depth of 1.5 m was built at Khon Kaen in North-Eastern Thailand (16 27'N102 E). Heat was successfully extracted from the lower convective zone (LCZ) of the solar pond by using a heat pipe heat exchanger made from 60 copper tubes with 21 mm inside diameter and 22 mm outside diameter. The length ofmore » the evaporator and condenser section was 800 mm and 200 mm respectively. R134a was used as the heat transfer fluid in the experiment. The theoretical model was formulated for the solar pond heat extraction on the basis of the energy conservation equations and by using the solar radiation data for the above location. Numerical methods were used to solve the modeling equations. In the analysis, the performance of heat exchanger is investigated by varying the velocity of inlet air used to extract heat from the condenser end of the heat pipe heat exchanger (HPHE). Air velocity was found to have a significant influence on the effectiveness of heat pipe heat exchanger. In the present investigation, there was an increase in effectiveness by 43% as the air velocity was decreased from 5 m/s to 1 m/s. The results obtained from the theoretical model showed good agreement with the experimental data. (author)« less

Modeling of the heat transfer performance of plate-type dispersion nuclear fuel elements

NASA Astrophysics Data System (ADS)

Ding, Shurong; Huo, Yongzhong; Yan, XiaoQing

2009-08-01

Considering the mutual actions between fuel particles and the metal matrix, the three-dimensional finite element models are developed to simulate the heat transfer behaviors of dispersion nuclear fuel plates. The research results indicate that the temperatures of the fuel plate might rise more distinctly with considering the particle swelling and the degraded surface heat transfer coefficients with increasing burnup; the local heating phenomenon within the particles appears when their thermal conductivities are too low. With rise of the surface heat transfer coefficients, the temperatures within the fuel plate decrease; the temperatures of the fuel plate are sensitive to the variations of the heat transfer coefficients whose values are lower, but their effects are weakened and slight when the heat transfer coefficients increase and reach a certain extent. Increasing the heat generation rate leads to elevating the internal temperatures. The temperatures and the maximum temperature differences within the plate increase along with the particle volume fractions. The surface thermal flux goes up along with particle volume fractions and heat generation rates, but the effects of surface heat transfer coefficients are not evident.

Experimental investigation of heat transfer and effectiveness in corrugated plate heat exchangers having different chevron angles

NASA Astrophysics Data System (ADS)

Kılıç, Bayram; İpek, Osman

2017-02-01

In this study, heat transfer rate and effectiveness of corrugated plate heat exchangers having different chevron angles were investigated experimentally. Chevron angles of plate heat exchangers are β = 30° and β = 60°. For this purpose, experimentally heating system used plate heat exchanger was designed and constructed. Thermodynamic analysis of corrugated plate heat exchangers having different chevron angles were carried out. The heat transfer rate and effectiveness values are calculated. The experimental results are shown that heat transfer rate and effectiveness values for β = 60° is higher than that of the other. Obtained experimental results were graphically presented.

7 CFR 2902.54 - Heat transfer fluids.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 7 Agriculture 15 2011-01-01 2011-01-01 false Heat transfer fluids. 2902.54 Section 2902.54... Items § 2902.54 Heat transfer fluids. (a) Definition. Products with high thermal capacities used to facilitate the transfer of heat from one location to another, including coolants or refrigerants for use in...

Heat Transfer in Glass, Aluminum, and Plastic Beverage Bottles

ERIC Educational Resources Information Center

Clark, William M.; Shevlin, Ryan C.; Soffen, Tanya S.

2010-01-01

This paper addresses a controversy regarding the effect of bottle material on the thermal performance of beverage bottles. Experiments and calculations that verify or refute advertising claims and represent an interesting way to teach heat transfer fundamentals are described. Heat transfer coefficients and the resistance to heat transfer offered…

Film Boiling Heat Transfer Properties of Liquid Hydrogen in Natural Convection

NASA Astrophysics Data System (ADS)

Horie, Y.; Shirai, Y.; Shiotsu, M.; Matsuzawa, T.; Yoneda, K.; Shigeta, H.; Tatsumoto, H.; Hata, K.; Naruo, Y.; Kobayashi, H.; Inatani, Y.

Film boiling heat transfer properties of LH2 for various pressures and subcooling conditions were measured by applying electric current to give an exponential heat input to a PtCo wire with a diameter of 1.2 mm submerged in LH2. The heated wire was set to be horizontal to the ground. The heat transfer coefficient in the film boiling region was higher for higher pressure and higher subcooling. The experimental results are compared with the equation of pool film boiling heat transfer. It is confirmed that the pool film boiling heat transfer coefficients in LH2 can be expressed by this equation.

Thermal impact of magmatism in subduction zones

NASA Astrophysics Data System (ADS)

Rees Jones, David W.; Katz, Richard F.; Tian, Meng; Rudge, John F.

2018-01-01

Magmatism in subduction zones builds continental crust and causes most of Earth's subaerial volcanism. The production rate and composition of magmas are controlled by the thermal structure of subduction zones. A range of geochemical and heat flow evidence has recently converged to indicate that subduction zones are hotter at lithospheric depths beneath the arc than predicted by canonical thermomechanical models, which neglect magmatism. We show that this discrepancy can be resolved by consideration of the heat transported by magma. In our one- and two-dimensional numerical models and scaling analysis, magmatic transport of sensible and latent heat locally alters the thermal structure of canonical models by ∼300 K, increasing predicted surface heat flow and mid-lithospheric temperatures to observed values. We find the advection of sensible heat to be larger than the deposition of latent heat. Based on these results we conclude that thermal transport by magma migration affects the chemistry and the location of arc volcanoes.

Effect of Welding Heat Input on Microstructure and Texture of Inconel 625 Weld Overlay Studied Using the Electron Backscatter Diffraction Method

NASA Astrophysics Data System (ADS)

Kim, Joon-Suk; Lee, Hae-Woo

2016-12-01

The grain size and the texture of three specimens prepared at different heat inputs were determined using optical microscopy and the electron backscatter diffraction method of scanning electron microscopy. Each specimen was equally divided into fusion line zone (FLZ), columnar dendrite zone (CDZ), and surface zone (SZ), according to the location of the weld. Fine dendrites were observed in the FLZ, coarse dendrites in the CDZ, and dendrites grew perpendicular to the FLZ and CDZ. As the heat input increased, the melted zone in the vicinity of the FLZ widened due to the higher Fe content. A lower image quality value was observed for the FLZ compared to the other zones. The results of grain size measurement in each zone showed that the grain size of the SZ became larger as the heat input increased. From the inverse pole figure (IPF) map in the normal direction (ND) and the rolling direction (RD), as the heat input increased, a specific orientation was formed. However, a dominant [001] direction was observed in the RD IPF map.

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.

Geophysical characteristics of the hydrothermal systems of Kilauea volcano, Hawaii

USGS Publications Warehouse

Kauahikaua, J.

1993-01-01

Clues to the overall structure of Kilauea volcano can be obtained from spatial studies of gravity, magnetic, and seismic velocity variations. The rift zones and summit are underlain by dense, magnetic, high P-wave-velocity rocks at depths of about 2 km less. The gravity and seismic velocity studies indicate that the rift structures are broad, extending farther to the north than to the south of the surface features. The magnetic data give more definition to the rift structures by allowing separation into a narrow, highly-magnetized, shallow zone and broad, flanking, magnetic lows. The patterns of gravity, magnetic variations, and seismicity document the southward migration of the upper cast rift zone. Regional, hydrologic features of Kilauea can be determined from resistivity and self-potential studies. High-level groundwater exists beneath Kilauea summit to elevations of +800 m within a triangular area bounded by the west edge of the upper southwest rift zone, the east edge of the upper east rift zone, and the Koa'c fault system. High-level groundwater is present within the east rift zone beyond the triangular summit area. Self-potential mapping shows that areas of local heat produce local fluid circulation in the unconfined aquifer (water table). The dynamics of Kilauea eruptions are responsible for both the source of heat and the fracture permeability of the hydrothermal system. Shallow seismicity and surface deformation indicate that magma is intruding and that fractures are forming beneath the rift zones and summit area. Magma supply estimates are used to calculate the rate of heat input to Kilauea's hydrothermal systems. Heat flows of 370-820 mW/m2 are calculated from deep wells within the lower east rift zone. The estimated heat input rate for Kilauea of 9 gigawatts (GW) is at least 25 times higher than the conductive heat loss as estimated from the heat flow in wells extrapolated over the area of the summit caldera and rift zones. Heat must be dissipated by another mechanism, or the heat input rate estimates are much too high. ?? 1993.

Solar heated fluidized bed gasification system

NASA Technical Reports Server (NTRS)

Qader, S. A. (Inventor)

1981-01-01

A solar-powered fluidized bed gasification system for gasifying carbonaceous material is presented. The system includes a solar gasifier which is heated by fluidizing gas and steam. Energy to heat the gas and steam is supplied by a high heat capacity refractory honeycomb which surrounds the fluid bed reactor zone. The high heat capacity refractory honeycomb is heated by solar energy focused on the honeycomb by solar concentrator through solar window. The fluid bed reaction zone is also heated directly and uniformly by thermal contact of the high heat capacity ceramic honeycomb with the walls of the fluidized bed reactor. Provisions are also made for recovering and recycling catalysts used in the gasification process. Back-up furnace is provided for start-up procedures and for supplying heat to the fluid bed reaction zone when adequate supplies of solar energy are not available.

Response mechanisms of attached premixed flames subjected to harmonic forcing

NASA Astrophysics Data System (ADS)

Shreekrishna

The persistent thrust for a cleaner, greener environment has prompted air pollution regulations to be enforced with increased stringency by environmental protection bodies all over the world. This has prompted gas turbine manufacturers to move from nonpremixed combustion to lean, premixed combustion. These lean premixed combustors operate quite fuel-lean compared to the stochiometric, in order to minimize CO and NOx productions, and are very susceptible to oscillations in any of the upstream flow variables. These oscillations cause the heat release rate of the flame to oscillate, which can engage one or more acoustic modes of the combustor or gas turbine components, and under certain conditions, lead to limit cycle oscillations. This phenomenon, called thermoacoustic instabilities, is characterized by very high pressure oscillations and increased heat fluxes at system walls, and can cause significant problems in the routine operability of these combustors, not to mention the occasional hardware damages that could occur, all of which cumulatively cost several millions of dollars. In a bid towards understanding this flow-flame interaction, this research works studies the heat release response of premixed flames to oscillations in reactant equivalence ratio, reactant velocity and pressure, under conditions where the flame preheat zone is convectively compact to these disturbances, using the G-equation. The heat release response is quantified by means of the flame transfer function and together with combustor acoustics, forms a critical component of the analytical models that can predict combustor dynamics. To this end, low excitation amplitude (linear) and high excitation amplitude (nonlinear) responses of the flame are studied in this work. The linear heat release response of lean, premixed flames are seen to be dominated by responses to velocity and equivalence ratio fluctuations at low frequencies, and to pressure fluctuations at high frequencies which are in the vicinity of typical screech frequencies in gas turbine combustors. The nonlinear response problem is exclusively studied in the case of equivalence ratio coupling. Various nonlinearity mechanisms are identified, amongst which the crossover mechanisms, viz., stoichiometric and flammability crossovers, are seen to be responsible in causing saturation in the overall heat release magnitude of the flame. The response physics remain the same across various preheat temperatures and reactant pressures. Finally, comparisons between the chemiluminescence transfer function obtained experimentally and the heat release transfer functions obtained from the reduced order model (ROM) are performed for lean, CH4/Air swirl-stabilized, axisymmetric V-flames. While the comparison between the phases of the experimental and theoretical transfer functions are encouraging, their magnitudes show disagreement at lower Strouhal number gains show disagreement.

Heat transfer in a microvascular network: the effect of heart rate on heating and cooling in reptiles (Pogona barbata and Varanus varius).

PubMed

Seebacher, F

2000-03-21

Thermally-induced changes in heart rate and blood flow in reptiles are believed to be of selective advantage by allowing animal to exert some control over rates of heating and cooling. This notion has become one of the principal paradigms in reptilian thermal physiology. However, the functional significance of changes in heart rate is unclear, because the effect of heart rate and blood flow on total animal heat transfer is not known. I used heat transfer theory to determine the importance of heat transfer by blood flow relative to conduction. I validated theoretical predictions by comparing them with field data from two species of lizard, bearded dragons (Pogona barbata) and lace monitors (Varanus varius). Heart rates measured in free-ranging lizards in the field were significantly higher during heating than during cooling, and heart rates decreased with body mass. Convective heat transfer by blood flow increased with heart rate. Rates of heat transfer by both blood flow and conduction decreased with mass, but the mass scaling exponents were different. Hence, rate of conductive heat transfer decreased more rapidly with increasing mass than did heat transfer by blood flow, so that the relative importance of blood flow in total animal heat transfer increased with mass. The functional significance of changes in heart rate and, hence, rates of heat transfer, in response to heating and cooling in lizards was quantified. For example, by increasing heart rate when entering a heating environment in the morning, and decreasing heart rate when the environment cools in the evening a Pogona can spend up to 44 min longer per day with body temperature within its preferred range. It was concluded that changes in heart rate in response to heating and cooling confer a selective advantage at least on reptiles of mass similar to that of the study animals (0. 21-5.6 kg). Copyright 2000 Academic Press.

Performance analyses of helical coil heat exchangers. The effect of external coil surface modification on heat exchanger effectiveness

NASA Astrophysics Data System (ADS)

Andrzejczyk, Rafał; Muszyński, Tomasz

2016-12-01

The shell and coil heat exchangers are commonly used in heating, ventilation, nuclear industry, process plant, heat recovery and air conditioning systems. This type of recuperators benefits from simple construction, the low value of pressure drops and high heat transfer. In helical coil, centrifugal force is acting on the moving fluid due to the curvature of the tube results in the development. It has been long recognized that the heat transfer in the helical tube is much better than in the straight ones because of the occurrence of secondary flow in planes normal to the main flow inside the helical structure. Helical tubes show good performance in heat transfer enhancement, while the uniform curvature of spiral structure is inconvenient in pipe installation in heat exchangers. Authors have presented their own construction of shell and tube heat exchanger with intensified heat transfer. The purpose of this article is to assess the influence of the surface modification over the performance coefficient and effectiveness. The experiments have been performed for the steady-state heat transfer. Experimental data points were gathered for both laminar and turbulent flow, both for co current- and countercurrent flow arrangement. To find optimal heat transfer intensification on the shell-side authors applied the number of transfer units analysis.

Heat exchanger device and method for heat removal or transfer

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

Koplow, Jeffrey P

2015-03-24

Systems and methods for a forced-convection heat exchanger are provided. In one embodiment, heat is transferred to or from a thermal load in thermal contact with a heat conducting structure, across a narrow air gap, to a rotating heat transfer structure immersed in a surrounding medium such as air.

Heat exchanger device and method for heat removal or transfer

DOEpatents

Koplow, Jeffrey P [San Ramon, CA

2012-07-24

Systems and methods for a forced-convection heat exchanger are provided. In one embodiment, heat is transferred to or from a thermal load in thermal contact with a heat conducting structure, across a narrow air gap, to a rotating heat transfer structure immersed in a surrounding medium such as air.

Heat exchanger device and method for heat removal or transfer

DOEpatents

Koplow, Jeffrey P

2013-12-10

Systems and methods for a forced-convection heat exchanger are provided. In one embodiment, heat is transferred to or from a thermal load in thermal contact with a heat conducting structure, across a narrow air gap, to a rotating heat transfer structure immersed in a surrounding medium such as air.

Heat exchanger device and method for heat removal or transfer

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

Koplow, Jeffrey P.

2015-12-08

Systems and methods for a forced-convection heat exchanger are provided. In one embodiment, heat is transferred to or from a thermal load in thermal contact with a heat conducting structure, across a narrow air gap, to a rotating heat transfer structure immersed in a surrounding medium such as air.

Strain heating in process zones; implications for metamorphism and partial melting in the lithosphere

NASA Astrophysics Data System (ADS)

Devès, Maud H.; Tait, Stephen R.; King, Geoffrey C. P.; Grandin, Raphaël

2014-05-01

Since the late 1970s, most earth scientists have discounted the plausibility of melting by shear-strain heating because temperature-dependent creep rheology leads to negative feedback and self-regulation. This paper presents a new model of distributed shear-strain heating that can account for the genesis of large volumes of magmas in both the crust and the mantle of the lithosphere. The kinematic (geometry and rates) frustration associated with incompatible fault junctions (e.g. triple-junction) prevents localisation of all strain on the major faults. Instead, deformation distributes off the main faults forming a large process zone that deforms still at high rates under both brittle and ductile conditions. The increased size of the shear-heated region minimises conductive heat loss, compared with that commonly associated with narrow shear zones, thus promoting strong heating and melting under reasonable rheological assumptions. Given the large volume of the heated zone, large volumes of melt can be generated even at small melt fractions.

Tunable heat transfer with smart nanofluids.

PubMed

Bernardin, Michele; Comitani, Federico; Vailati, Alberto

2012-06-01

Strongly thermophilic nanofluids are able to transfer either small or large quantities of heat when subjected to a stable temperature difference. We investigate the bistability diagram of the heat transferred by this class of nanofluids. We show that bistability can be exploited to obtain a controlled switching between a conductive and a convective regime of heat transfer, so as to achieve a controlled modulation of the heat flux.

A New Concept for Geothermal Energy Extraction: The Radiator - Enhanced Geothermal System

NASA Astrophysics Data System (ADS)

Hilpert, M.; Geiser, P.; Marsh, B. D.; Malin, P. E.; Moore, S.

2014-12-01

Enhanced Geothermal Systems (EGS) in hot dry rock frequently underperform or fail due to insufficient reservoir characterization and poorly controlled permeability stimulation. Our new EGS design is based on the concept of a cooling radiator of an internal combustion engine, which we call the Radiator EGS (RAD-EGS). Within a hot sedimentary aquifer, we propose to construct vertically extensive heat exchanger vanes, which consist of rubblized zones of high permeability and which emulate a hydrothermal system. A "crows-foot" lateral drilling pattern at multiple levels is used to form a vertical array that includes S1 and Shmax. To create the radiator, we propose to use propellant fracing. System cool-down is delayed by regional background flow and induced upward flow of the coolant which initially heats the rock. Tomographic Fracture Imaging is used to image and control the permeability field changes. Preliminary heat transfer calculations suggest that the RAD-EGS will allow for commercial electricity production for at least several tens of years.

Direct-contact closed-loop heat exchanger

DOEpatents

Berry, Gregory F.; Minkov, Vladimir; Petrick, Michael

1984-01-01

A high temperature heat exchanger with a closed loop and a heat transfer liquid within the loop, the closed loop having a first horizontal channel with inlet and outlet means for providing direct contact of a first fluid at a first temperature with the heat transfer liquid, a second horizontal channel with inlet and outlet means for providing direct contact of a second fluid at a second temperature with the heat transfer liquid, and means for circulating the heat transfer liquid.

Development of a laser-induced heat flux technique for measurement of convective heat transfer coefficients in a supersonic flowfield

NASA Technical Reports Server (NTRS)

Porro, A. Robert; Keith, Theo G., Jr.; Hingst, Warren R.; Chriss, Randall M.; Seablom, Kirk D.

1991-01-01

A technique is developed to measure the local convective heat transfer coefficient on a model surface in a supersonic flow field. The technique uses a laser to apply a discrete local heat flux at the model test surface, and an infrared camera system determines the local temperature distribution due to heating. From this temperature distribution and an analysis of the heating process, a local convective heat transfer coefficient is determined. The technique was used to measure the load surface convective heat transfer coefficient distribution on a flat plate at nominal Mach numbers of 2.5, 3.0, 3.5, and 4.0. The flat plate boundary layer initially was laminar and became transitional in the measurement region. The experimental results agreed reasonably well with theoretical predictions of convective heat transfer of flat plate laminar boundary layers. The results indicate that this non-intrusive optical measurement technique has the potential to obtain high quality surface convective heat transfer measurements in high speed flowfields.

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

N.D. Francis

The objective of this calculation is to develop a time dependent in-drift effective thermal conductivity parameter that will approximate heat conduction, thermal radiation, and natural convection heat transfer using a single mode of heat transfer (heat conduction). In order to reduce the physical and numerical complexity of the heat transfer processes that occur (and must be modeled) as a result of the emplacement of heat generating wastes, a single parameter will be developed that approximates all forms of heat transfer from the waste package surface to the drift wall (or from one surface exchanging heat with another). Subsequently, with thismore » single parameter, one heat transfer mechanism (e.g., conduction heat transfer) can be used in the models. The resulting parameter is to be used as input in the drift-scale process-level models applied in total system performance assessments for the site recommendation (TSPA-SR). The format of this parameter will be a time-dependent table for direct input into the thermal-hydrologic (TH) and the thermal-hydrologic-chemical (THC) models.« less

A laser-induced heat flux technique for convective heat transfer measurements in high speed flows

NASA Technical Reports Server (NTRS)

Porro, A. R.; Keith, T. G., Jr.; Hingst, W. R.

1991-01-01

A technique is developed to measure the local convective heat transfer coefficient on a model surface in a supersonic flow field. The technique uses a laser to apply a discrete local heat flux at the model test surface, and an infrared camera system determines the local temperature distribution due to the heating. From this temperature distribution and an analysis of the heating process, a local convective heat transfer coefficient is determined. The technique was used to measure the local surface convective heat transfer coefficient distribution on a flat plate at nominal Mach numbers of 2.5, 3.0, 3.5, and 4.0. The flat plate boundary layer initially was laminar and became transitional in the measurement region. The experimentally determined convective heat transfer coefficients were generally higher than the theoretical predictions for flat plate laminar boundary layers. However, the results indicate that this nonintrusive optical measurement technique has the potential to measure surface convective heat transfer coefficients in high speed flow fields.

A laser-induced heat flux technique for convective heat transfer measurements in high speed flows

NASA Technical Reports Server (NTRS)

Porro, A. R.; Keith, T. G., Jr.; Hingst, W. R.

1991-01-01

A technique is developed to measure the local convective heat transfer coefficient on a model surface in a supersonic flow field. The technique uses a laser to apply a discrete local heat flux at the model test surface, and an infrared camera system determines the local temperature distribution due to the heating. From this temperature distribution and an analysis of the heating process, a local convective heat transfer coefficient is determined. The technique was used to measure the local surface convective heat transfer coefficient distribution on a flat plate at nominal Mach numbers of 2.5, 3.0, 3.5, and 4.0. The flat plate boundary layer initially was laminar and became transitional in the measurement region. The experimentally determined convective heat transfer coefficients were generally higher than the theoretical predictions for flat plate laminar boundary layers. However, the results indicate that this nonintrusive optical measurement technique has the potential to measure surface convective heat transfer coefficients in high-speed flowfields.

Characteristics of turbulence transport for momentum and heat in particle-laden turbulent vertical channel flows

NASA Astrophysics Data System (ADS)

Liu, Caixi; Tang, Shuai; Shen, Lian; Dong, Yuhong

2017-10-01

The dynamic and thermal performance of particle-laden turbulent flow is investigated via direction numerical simulation combined with the Lagrangian point-particle tracking under the condition of two-way coupling, with a focus on the contributions of particle feedback effect to momentum and heat transfer of turbulence. We take into account the effects of particles on flow drag and Nusselt number and explore the possibility of drag reduction in conjunction with heat transfer enhancement in particle-laden turbulent flows. The effects of particles on momentum and heat transfer are analyzed, and the possibility of drag reduction in conjunction with heat transfer enhancement for the prototypical case of particle-laden turbulent channel flows is addressed. We present results of turbulence modification and heat transfer in turbulent particle-laden channel flow, which shows the heat transfer reduction when large inertial particles with low specific heat capacity are added to the flow. However, we also found an enhancement of the heat transfer and a small reduction of the flow drag when particles with high specific heat capacity are involved. The present results show that particles, which are active agents, interact not only with the velocity field, but also the temperature field and can cause a dissimilarity in momentum and heat transport. This demonstrates that the possibility to increase heat transfer and suppress friction drag can be achieved with addition of particles with different thermal properties.

Heat Transfer and Fluid Mechanics Institute, 24th, Oregon State University, Corvallis, Ore., June 12-14, 1974, Proceedings

NASA Technical Reports Server (NTRS)

Davis, L. R. (Editor); Wilson, R. E.

1974-01-01

Recent theoretical and experimental studies in heat transfer and fluid mechanics, including some environmental protection investigations, are presented in a number of papers. Some of the topics covered include condensation heat transfer, a model of turbulent momentum and heat transfer at points of separation and reattachment, an explicit scheme for calculations of confined turbulent flows with heat transfer, heat transfer effects on a delta wing in subsonic flow, fluid mechanics of ocean outfalls, thermal plumes from industrial cooling water, a photochemical air pollution model for the Los Angeles air basin, and a turbulence model of diurnal variations in the planetary boundary layer. Individual items are announced in this issue.

Generator-absorber-heat exchange heat transfer apparatus and method and use thereof in a heat pump

DOEpatents

Phillips, Benjamin A.; Zawacki, Thomas S.

1996-12-03

Numerous embodiments and related methods for generator-absorber heat exchange (GAX) are disclosed, particularly for absorption heat pump systems. Such embodiments and related methods use the working solution of the absorption system for the heat transfer medium. A combination of weak and rich liquor working solution is used as the heat transfer medium.

Heat transfer assembly for a fluorescent lamp and fixture

DOEpatents

Siminovitch, Michael J.; Rubenstein, Francis M.; Whitman, Richard E.

1992-01-01

In a lighting fixture including a lamp and a housing, a heat transfer structure is disclosed for reducing the minimum lamp wall temperature of a fluorescent light bulb. The heat transfer structure, constructed of thermally conductive material, extends from inside the housing to outside the housing, transferring heat energy generated from a fluorescent light bulb to outside the housing where the heat energy is dissipated to the ambient air outside the housing. Also disclosed is a method for reducing minimum lamp wall temperatures. Further disclosed is an improved lighting fixture including a lamp, a housing and the aforementioned heat transfer structure.

Influence of the Stefan Flow on Heat Transfer in the System "Gas-Solid Particle" in Thermochemical Conversion of a Solid Fuel

NASA Astrophysics Data System (ADS)

Pechenegov, Yu. Ya.; Mrakin, A. N.

2017-09-01

Recommendations are presented on calculating interphase heat transfer in gas-disperse systems of plants for thermochemical conversion of ground solid fuel. An analysis is made of the influence of the gas release of fuel particles on the heat transfer during their heating. It is shown that in the processes of thermal treatment of oil shales, the presence of gas release reduces substantially the intensity of interphase heat transfer compared to the heat transfer in the absence of thermochemical decomposition of the solid phase.

Fluidized bed heating process and apparatus

NASA Technical Reports Server (NTRS)

McHale, Edward J. (Inventor)

1981-01-01

Capacitive electrical heating of a fluidized bed enables the individual solid particles within the bed to constitute the hottest portion thereof. This effect is achieved by applying an A. C. voltage potential between dielectric coated electrodes, one of which is advantageously the wall of the fluidized bed rejection zone, sufficient to create electrical currents in said particles so as to dissipate heat therein. In the decomposition of silane or halosilanes in a fluidized bed reaction zone, such heating enhances the desired deposition of silicon product on the surface of the seed particles within the fluidized bed and minimizes undesired coating of silicon on the wall of the reaction zone and the homogeneous formation of fine silicon powder within said zone.

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

Effect of Reynolds number, turbulence level and periodic wake flow on heat transfer on low pressure turbine blades.

PubMed

Suslov, D; Schulz, A; Wittig, S

2001-05-01

The development of effective cooling methods is of major importance for the design of new gas turbines blades. The conception of optimal cooling schemes requires a detailed knowledge of the heat transfer processes on the blade's surfaces. The thermal load of turbine blades is predominantly determined by convective heat transfer which is described by the local heat transfer coefficient. Heat transfer is closely related to the boundary layer development along the blade surface and hence depends on various flow conditions and geometrical parameters. Particularly Reynolds number, pressures gradient and turbulence level have great impact on the boundary layer development and the according heat transfer. Therefore, in the present study, the influence of Reynolds number, turbulence intensity, and periodic unsteady inflow on the local heat transfer of a typical low pressure turbine airfoil is experimentally examined in a plane cascade.

[Effect of heat transfer in the packages on the stability of thiamine nitrate under uncontrolled temperature conditions].

PubMed

Nakamura, Toru; Yamaji, Takayuki; Takayama, Kozo

2013-01-01

To accurately predict the stability of thiamine nitrate as a model drug in pharmaceutical products under uncontrolled temperature conditions, the average reaction rate constant was determined, taking into account the heat transfer from the atmosphere to the product. The stability tests of thiamine nitrate in the three packages with different heat transfers were performed under non-isothermal conditions. The stability data observed were compared with the predictions based on a newly developed method, showing that the stability was well predicted by the method involving the heat transfer. By contrast, there were some deviations observed from the predicted data, without considering heat transfer in the packages with low heat transfer. The above-mentioned result clearly shows that heat transfer should be considered to ensure accurate prediction of the stability of commercial pharmaceutical products under non-isothermal atmospheres.

Experimental study of heat transfer enhancement due to the surface vibrations in a flexible double pipe heat exchanger

NASA Astrophysics Data System (ADS)

Hosseinian, A.; Meghdadi Isfahani, A. H.

2018-04-01

In this study, the heat transfer enhancement due to the surface vibration for a double pipe heat exchanger, made of PVDF, is investigated. In order to create forced vibrations (3-9 m/s2, 100 Hz) on the outer surface of the heat exchanger electro-dynamic vibrators are used. Experiments were performed at inner Reynolds numbers ranging from 2533 to 9960. The effects of volume flow rate and temperature on heat transfer performance are evaluated. Results demonstrated that heat transfer coefficient increases by increasing vibration level and mass flow rate. The most increase in heat transfer coefficient is 97% which is obtained for the highest vibration level (9 m/s2) in the experiment range.

Transient Interaction Between Reduction and Slagging Reactions of Wustite in Simulated Cohesive Zone of Blast Furnace

NASA Astrophysics Data System (ADS)

Ma, Kaihui; Xu, Jian; Deng, Junyi; Wang, Dongdong; Xu, Yang; Liao, Zhehan; Sun, Chengfeng; Zhang, Shengfu; Wen, Liangying

2018-06-01

The blast furnace cohesive zone plays an important role in the gas flow distribution and heat-transfer efficiency. Previous work mainly employed temperature-based indices to evaluate and predict the shape and thickness of the cohesive zone, whereas the internal reactions and related effects on the softening and melting properties of a complex burden are ignored. In this study, an innovative index, namely, shrinkage rate (SR), is first proposed to directly estimate the shrinkage behavior of wustite (FeO)-packed bed inside a simulated cohesive zone. The index is applied as the temperature increases to elucidate the transient interaction between reduction and slagging reactions. Results show that the thermally induced slagging reaction causes the packed bed to shrink at lower temperature, and the SR doubles when compounds with low melting temperature are generated by adding a reasonable concentration of CaO or SiO2. The reduction reaction becomes the driving force during the shrinkage of the packed bed between 1173 K and 1273 K when CO is introduced in the mixture gas. Then, the dominating factors for further shrinkage include slagging, reduction, or both factors. These factors vary with respect to the added compounds or temperature.

Stagnation Region Heat Transfer: The Influence of Turbulence Parameters, Reynolds Number and Body Shape

NASA Technical Reports Server (NTRS)

Vanfossen, G. James; Simoneau, Robert J.

1994-01-01

The effect of velocity gradient on stagnation region heat transfer augmentation by free stream turbulence was investigated. Heat transfer was measured in the stagnation region of four models with elliptical leading edges with ratios of major to minor axes of 1:1, 1.5:1, 2.25:1, and 3:1. Four geometrically similar, square bar, square mesh, biplane grids were used to generate free stream turbulence with different intensities and length. Heat transfer measurements were made for the following ranges of parameters: Reynolds number, based on leading edge diameter, 37,000 to 228,000; dimensionless leading edge velocity gradient, 1.20 to 1.80; turbulence intensity, 1.1 to 15.9%; and length scale to leading edge diameter ratio, 0.05 to 0.30. Stagnation point heat transfer augmentation by free stream turbulence can be predicted using a modified version of a previously developed correlation for a circular leading edge. Heat transfer augmentation was independent of body shape at the stagnation point. The heat transfer distribution down-stream from the stagnation point can be predicted using the normalized laminar heat transfer distribution.

Thermal Modeling of Bridgman Crystal Growth

NASA Technical Reports Server (NTRS)

Cothran, E.

1983-01-01

Heat Flow modeled for moving or stationary rod shaped sample inside directional-solidification furnace. Program effectively models one-dimensional heat flow in translating or motionless rod-shaped sample inside of directionalsolidification furnace in which adiabatic zone separates hot zone and cold zone. Applicable to systems for which Biot numbers in hot and cold zones are less than unity.

Numerical simulation of heat transfer in metal foams

NASA Astrophysics Data System (ADS)

Gangapatnam, Priyatham; Kurian, Renju; Venkateshan, S. P.

2018-02-01

This paper reports a numerical study of forced convection heat transfer in high porosity aluminum foams. Numerical modeling is done considering both local thermal equilibrium and non local thermal equilibrium conditions in ANSYS-Fluent. The results of the numerical model were validated with experimental results, where air was forced through aluminum foams in a vertical duct at different heat fluxes and velocities. It is observed that while the LTE model highly under predicts the heat transfer in these foams, LTNE model predicts the Nusselt number accurately. The novelty of this study is that once hydrodynamic experiments are conducted the permeability and porosity values obtained experimentally can be used to numerically simulate heat transfer in metal foams. The simulation of heat transfer in foams is further extended to find the effect of foam thickness on heat transfer in metal foams. The numerical results indicate that though larger foam thicknesses resulted in higher heat transfer coefficient, this effect weakens with thickness and is negligible in thick foams.

Numerical investigation of Al2O3/water nanofluid laminar convective heat transfer through triangular ducts

NASA Astrophysics Data System (ADS)

Zeinali Heris, Saeed; Noie, Seyyed Hossein; Talaii, Elham; Sargolzaei, Javad

2011-12-01

In this article, laminar flow-forced convective heat transfer of Al2O3/water nanofluid in a triangular duct under constant wall temperature condition is investigated numerically. In this investigation, the effects of parameters, such as nanoparticles diameter, concentration, and Reynolds number on the enhancement of nanofluids heat transfer is studied. Besides, the comparison between nanofluid and pure fluid heat transfer is achieved in this article. Sometimes, because of pressure drop limitations, the need for non-circular ducts arises in many heat transfer applications. The low heat transfer rate of non-circular ducts is one the limitations of these systems, and utilization of nanofluid instead of pure fluid because of its potential to increase heat transfer of system can compensate this problem. In this article, for considering the presence of nanoparticl: es, the dispersion model is used. Numerical results represent an enhancement of heat transfer of fluid associated with changing to the suspension of nanometer-sized particles in the triangular duct. The results of the present model indicate that the nanofluid Nusselt number increases with increasing concentration of nanoparticles and decreasing diameter. Also, the enhancement of the fluid heat transfer becomes better at high Re in laminar flow with the addition of nanoparticles.

Boiling Heat Transfer Mechanisms in Earth and Low Gravity: Boundary Condition and Heater Aspect Ratio Effects

NASA Technical Reports Server (NTRS)

Kim, Jungho

2004-01-01

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. Recently, time and space resolved heat transfer data were obtained in both earth and low gravity environments using an array of microheaters varying in size between 100 microns to 700 microns. These heaters were operated in both constant temperature as well as constant heat flux mode. Heat transfer under nucleating bubbles in earth gravity were directly measured using a microheater array with 100 m resolution operated in constant temperature mode with low and high subcooled bulk liquid along with images from below and from the side. The individual bubble departure diameter and energy transfer were larger with low subcooling but the departure frequency increased at high subcooling, resulting in higher overall heat transfer. The bubble growth for both subcoolings was primarily due to energy transfer from the superheated liquid layer relatively little was due to wall heat transfer during the bubble growth process. Oscillating bubbles and sliding bubbles were also observed in highly subcooled boiling. Transient conduction and/or microconvection was the dominant heat transfer mechanism in the above cases. A transient conduction model was developed and compared with the experimental data with good agreement. Data was also obtained with the heater array operated in a constant heat flux mode and measuring the temperature distribution across the array during boiling. The instantaneous heat transfer into the substrate was numerically determined and subtracted from the supplied heat to obtain the wall to liquid heat flux.

Second principle approach to the analysis of unsteady flow and heat transfer in a tube with arc-shaped corrugation

NASA Astrophysics Data System (ADS)

Pagliarini, G.; Vocale, P.; Mocerino, A.; Rainieri, S.

2017-01-01

Passive convective heat transfer enhancement techniques are well known and widespread tool for increasing the efficiency of heat transfer equipment. In spite of the ability of the first principle approach to forecast the macroscopic effects of the passive techniques for heat transfer enhancement, namely the increase of both the overall heat exchanged and the head losses, a first principle analysis based on energy, momentum and mass local conservation equations is hardly able to give a comprehensive explanation of how local modifications in the boundary layers contribute to the overall effect. A deeper insight on the heat transfer enhancement mechanisms can be instead obtained within a second principle approach, through the analysis of the local exergy dissipation phenomena which are related to heat transfer and fluid flow. To this aim, the analysis based on the second principle approach implemented through a careful consideration of the local entropy generation rate seems the most suitable, since it allows to identify more precisely the cause of the loss of efficiency in the heat transfer process, thus providing a useful guide in the choice of the most suitable heat transfer enhancement techniques.

Anomalous heat transfer modes of nanofluids: a review based on statistical analysis

NASA Astrophysics Data System (ADS)

Sergis, Antonis; Hardalupas, Yannis

2011-05-01

This paper contains the results of a concise statistical review analysis of a large amount of publications regarding the anomalous heat transfer modes of nanofluids. The application of nanofluids as coolants is a novel practise with no established physical foundations explaining the observed anomalous heat transfer. As a consequence, traditional methods of performing a literature review may not be adequate in presenting objectively the results representing the bulk of the available literature. The current literature review analysis aims to resolve the problems faced by researchers in the past by employing an unbiased statistical analysis to present and reveal the current trends and general belief of the scientific community regarding the anomalous heat transfer modes of nanofluids. The thermal performance analysis indicated that statistically there exists a variable enhancement for conduction, convection/mixed heat transfer, pool boiling heat transfer and critical heat flux modes. The most popular proposed mechanisms in the literature to explain heat transfer in nanofluids are revealed, as well as possible trends between nanofluid properties and thermal performance. The review also suggests future experimentation to provide more conclusive answers to the control mechanisms and influential parameters of heat transfer in nanofluids.

Anomalous heat transfer modes of nanofluids: a review based on statistical analysis.

PubMed

Sergis, Antonis; Hardalupas, Yannis

2011-05-19

This paper contains the results of a concise statistical review analysis of a large amount of publications regarding the anomalous heat transfer modes of nanofluids. The application of nanofluids as coolants is a novel practise with no established physical foundations explaining the observed anomalous heat transfer. As a consequence, traditional methods of performing a literature review may not be adequate in presenting objectively the results representing the bulk of the available literature. The current literature review analysis aims to resolve the problems faced by researchers in the past by employing an unbiased statistical analysis to present and reveal the current trends and general belief of the scientific community regarding the anomalous heat transfer modes of nanofluids. The thermal performance analysis indicated that statistically there exists a variable enhancement for conduction, convection/mixed heat transfer, pool boiling heat transfer and critical heat flux modes. The most popular proposed mechanisms in the literature to explain heat transfer in nanofluids are revealed, as well as possible trends between nanofluid properties and thermal performance. The review also suggests future experimentation to provide more conclusive answers to the control mechanisms and influential parameters of heat transfer in nanofluids.

Computational investigation of fluid flow and heat transfer of an economizer by porous medium approach

NASA Astrophysics Data System (ADS)

Babu, C. Rajesh; Kumar, P.; Rajamohan, G.

2017-07-01

Computation of fluid flow and heat transfer in an economizer is simulated by a porous medium approach, with plain tubes having a horizontal in-line arrangement and cross flow arrangement in a coal-fired thermal power plant. The economizer is a thermal mechanical device that captures waste heat from the thermal exhaust flue gasses through heat transfer surfaces to preheat boiler feed water. In order to evaluate the fluid flow and heat transfer on tubes, a numerical analysis on heat transfer performance is carried out on an 110 t/h MCR (Maximum continuous rating) boiler unit. In this study, thermal performance is investigated using the computational fluid dynamics (CFD) simulation using ANSYS FLUENT. The fouling factor ε and the overall heat transfer coefficient ψ are employed to evaluate the fluid flow and heat transfer. The model demands significant computational details for geometric modeling, grid generation, and numerical calculations to evaluate the thermal performance of an economizer. The simulation results show that the overall heat transfer coefficient 37.76 W/(m2K) and economizer coil side pressure drop of 0.2 (kg/cm2) are found to be conformity within the tolerable limits when compared with existing industrial economizer data.

Undergraduate Laboratory on a Turbulent Impinging Jet

NASA Astrophysics Data System (ADS)

Ivanosky, Arnaud; Brezzard, Etienne; van Poppel, Bret; Benson, Michael

2017-11-01

An undergraduate thermal sciences laboratory exercise that includes both experimental fluid mechanics and heat transfer measurements of an impinging jet is presented. The flow field is measured using magnetic resonance velocimetry (MRV) of a water flow, while IR thermography is used in the heat transfer testing. Flow Reynolds numbers for both the heat transfer and fluid mechanics tests range from 20,000-50,000 based on the jet diameter for a fully turbulent flow condition, with target surface temperatures in the heat transfer test reaching a maximum of approximately 50 Kelvin. The heat transfer target surface is subject to a measured uniform Joule heat flux, a well-defined boundary condition that allows comparison to existing correlations. The MRV generates a 3-component 3-dimensional data set, while the IR thermography provides a 2-dimensional heat transfer coefficient (or Nusselt number) map. These data sets can be post-processed and compared to existing correlations to verify data quality, and the sets can be juxtaposed to understand how flow features drive heat transfer. The laboratory setup, data acquisition, and analysis procedures are described for the laboratory experience, which can be incorporated as fluid mechanics, experimental methods, and heat transfer courses

Anomalous heat transfer modes of nanofluids: a review based on statistical analysis

PubMed Central

2011-01-01

This paper contains the results of a concise statistical review analysis of a large amount of publications regarding the anomalous heat transfer modes of nanofluids. The application of nanofluids as coolants is a novel practise with no established physical foundations explaining the observed anomalous heat transfer. As a consequence, traditional methods of performing a literature review may not be adequate in presenting objectively the results representing the bulk of the available literature. The current literature review analysis aims to resolve the problems faced by researchers in the past by employing an unbiased statistical analysis to present and reveal the current trends and general belief of the scientific community regarding the anomalous heat transfer modes of nanofluids. The thermal performance analysis indicated that statistically there exists a variable enhancement for conduction, convection/mixed heat transfer, pool boiling heat transfer and critical heat flux modes. The most popular proposed mechanisms in the literature to explain heat transfer in nanofluids are revealed, as well as possible trends between nanofluid properties and thermal performance. The review also suggests future experimentation to provide more conclusive answers to the control mechanisms and influential parameters of heat transfer in nanofluids. PMID:21711932

Liquid-Infused Smooth Surface for Improved Condensation Heat Transfer.

PubMed

Tsuchiya, Hirotaka; Tenjimbayashi, Mizuki; Moriya, Takeo; Yoshikawa, Ryohei; Sasaki, Kaichi; Togasawa, Ryo; Yamazaki, Taku; Manabe, Kengo; Shiratori, Seimei

2017-09-12

Control of vapor condensation properties is a promising approach to manage a crucial part of energy infrastructure conditions. Heat transfer by vapor condensation on superhydrophobic coatings has garnered attention, because dropwise condensation on superhydrophobic surfaces with rough structures leads to favorable heat-transfer performance. However, pinned condensed water droplets within the rough structure and a high thermodynamic energy barrier for nucleation of superhydrophobic surfaces limit their heat-transfer increase. Recently, slippery liquid-infused surfaces (SLIPS) have been investigated, because of their high water sliding ability and surface smoothness originating from the liquid layer. However, even on SLIPS, condensed water droplets are eventually pinned to degrade their heat-transfer properties after extended use, because the rough base layer is exposed as infused liquid is lost. Herein, we report a liquid-infused smooth surface named "SPLASH" (surface with π electron interaction liquid adsorption, smoothness, and hydrophobicity) to overcome the problems derived from the rough structures in previous approaches to obtain stable, high heat-transfer performance. The SPLASH displayed a maximum condensation heat-transfer coefficient that was 175% higher than that of an uncoated substrate. The SPLASH also showed higher heat-transfer performance and more stable dropwise condensation than superhydrophobic surfaces and SLIPS from the viewpoints of condensed water droplet mobility and the thermodynamic energy barrier for nucleation. The effects of liquid-infused surface roughness and liquid viscosity on condensation heat transfer were investigated to compare heat-transfer performance. This research will aid industrial applications using vapor condensation.

Heat transfer enhancement with mixing vane spacers using the field synergy principle

NASA Astrophysics Data System (ADS)

Yang, Lixin; Zhou, Mengjun; Tian, Zihao

2017-01-01

The single-phase heat transfer characteristics in a PWR fuel assembly are important. Many investigations attempt to obtain the heat transfer characteristics by studying the flow features in a 5 × 5 rod bundle with a spacer grid. The field synergy principle is used to discuss the mechanism of heat transfer enhancement using mixing vanes according to computational fluid dynamics results, including a spacer grid without mixing vanes, one with a split mixing vane, and one with a separate mixing vane. The results show that the field synergy principle is feasible to explain the mechanism of heat transfer enhancement in a fuel assembly. The enhancement in subchannels is more effective than on the rod's surface. If the pressure loss is ignored, the performance of the split mixing vane is superior to the separate mixing vane based on the enhanced heat transfer. Increasing the blending angle of the split mixing vane improves heat transfer enhancement, the maximum of which is 7.1%. Increasing the blending angle of the separate mixing vane did not significantly enhance heat transfer in the rod bundle, and even prevented heat transfer at a blending angle of 50°. This finding testifies to the feasibility of predicting heat transfer in a rod bundle with a spacer grid by field synergy, and upon comparison with analyzed flow features only, the field synergy method may provide more accurate guidance for optimizing the use of mixing vanes.

Duration of mineralization and fluid-flow history of the Upper Mississippi Valley zinc-lead district

USGS Publications Warehouse

Rowan, E.L.; Goldhaber, M.B.

1995-01-01

Studies of fluid inclusions in sphalerite and biomarkers from the Upper Mississippi Valley zinc district show homogenization temperatures to be primarily between 90 and 150??C, yet show relatively low levels of thermal maturity. Numerical calculations are used to simulate fluid and heat flow through fracture-controlled ore zones and heat transfer to the adjacent rocks. Combining a best-fit path through fluid-inclusion data with measured thermal alteration of biomarkers, the time interval during which mineralizing fluids circulated through the Upper Mississippi Valley district was calculated to be on the order of 200 ka. Cambrian and Ordovician aquifers underlying the district, principally the St. Peter and Mt. Simon Sandstones, were the source of the mineralizing fluid. The duration of mineralization thus reflects the fluid-flow history of these regional aquifers. -from Authors

Forced Convective Heat Transfer of Aqueous Al₂O₃ Nanofluid Through Shell and Tube Heat Exchanger.

PubMed

Haque, A K M Mahmudul; Kim, Sedong; Kim, Junhyo; Noh, Jungpil; Huh, Sunchul; Choi, Byeongkeun; Chung, Hanshik; Jeong, Hyomin

2018-03-01

This study presents the forced convective heat transfer of a nanofluid consisting of distilled water and different weight concentrations (1 wt% and 2 wt%) of Al2O3 nanoparticles flowing in a vertical shell and tube heat exchanger under counter flow and laminar flow regime with certain constant heat flaxes (at 20 °C, 30 °C, 40 °C and 50 °C). The Al2O3 nanoparticles of about 50 nm diameter are used in the present study. Stability of aqueous Al2O3 nanofluids, TEM, thermal conductivity, temperature differences, heat transfer rate, T-Q diagrams, LMTD and convective heat transfer coefficient are investigated experimentally. Experimental results emphasize the substantial enhancement of heat transfer due to the Al2O3 nanoparticles presence in the nanofluid. Heat transfer rate for distilled water and aqueous nanofluids are calculated after getting an efficient setup which shows 19.25% and 35.82% enhancement of heat transfer rate of 1 wt% and 2 wt% aqueous Al2O3 nanofluids as compared to that of distilled water. Finally, the analysis shows that though there are 27.33% and 59.08% enhancement of 1 wt% Al2O3 and 2 wt% Al2O3 respectively as compared to that of distilled water at 30 °C, convective heat transfer coefficient decreases with increasing heat flux of heated fluid in this experimental setup.

Periodic Viscous Shear Heating Instability in Fine-Grained Shear Zones: Mechanism for Intermediate Depth Earthquakes

NASA Astrophysics Data System (ADS)

Coon, E.; Kelemen, P.; Hirth, G.; Spiegelman, M.

2005-12-01

Kelemen and Hirth (Fall 2004 AGU) presented a model for periodic, viscous shear heating instabilities along pre-existing, fine grained shear zones. This provides an attractive alternative to dehydration embrittlement for explaining intermediate-depth earthquakes, especially those in a narrow thermal window within the mantle section of subducting oceanic plates (Hacker et al JGR03). Ductile shear zones with widths of cm to m are common in shallow mantle massifs and peridotite along oceanic fracture zones. Pseudotachylites in a mantle shear zone show that shear heating temperatures exceeded the mantle solidus (Obata & Karato Tectonophys95). Olivine grain growth in shear zones is pinned by closely spaced pyroxenes; thus, once formed, these features do not `heal' on geological time scales in the absence of melt or fluid (Warren & Hirth EPSL05). Grain-size sensitive creep will be localized within these shear zones, in preference to host rocks with olivine grain size from 1 to 10 mm. Inspired by the work of Whitehead & Gans (GJRAS74), we proposed that such pre-existing shear zones might undergo repeated shear heating instabilities. This is not a new concept; what is new is that viscous deformation is limited to a narrow shear zone, because grain boundary sliding, sensitive to both stress and grain size, may accommodate creep even at high stress and high temperature. These new ideas yield a new result: simple models for a periodic shear heating instability. Last year, we presented a 1D numerical model using olivine flow laws, assuming that viscous deformation remains localized in shear zones, surrounded by host rocks undergoing elastic deformation. Stress evolves due to elastic strain and drives viscous deformation in a shear zone of specified width. Shear heating and thermal diffusion control T. A maximum of 1400 C (substantial melting of peridotite ) was imposed. Grain size evolves due to recrystallization and diffusion. For strain rates of E-13 to E-14 per sec and initial T of 600 to 850 C, this produced periodic viscous shear heating events with periods of 100's to 1000's of years. Strain rates during these events approach 1 per second as temperatures reach 1400. Cooling between events returns the shear zone almost to its initial temperature, though ultimately shear zone temperature between events exceeds 850 C resulting in stable viscous creep. Analysis shows that our system of equations jumps from one steady state to another, depending on a non-dimensional number relating the rate of shear heating to the rate of diffusive cooling. This year, Kelemen and Hirth show that the rate of stress drop during shear heating events is greater than the rate of elastic stress relaxation, so that shear heating events are a runaway instability. Rather than capping the temperature at 1400 C, we parameterize melt fraction as a function of T, and shear viscosity as a function of melt fraction. A problem with our 1D model is that predicted displacements are too large (1 to 20 m) during shear heating events, essentially because there is no resistance at shear zone ends. To address this, Coon and Spiegelman have embarked on a 3D model, incorporating a pre-existing fine-grained, tabular shear zone of finite extent, with a visco-elastic rheology for both shear zone and wall rocks. Preliminary 1D models using this approach show that the more complicated rheology yields the same result as the simpler model. We will present preliminary results, and determine the Maxwell time for this problem, since low strain rates could produce viscous relaxation in both shear zone and wall rocks with negligible shear heating.

Fractional watt Vuillemier cryogenic refrigerator program engineering notebook. Volume 1: Thermal analysis

NASA Technical Reports Server (NTRS)

Miller, W. S.

1974-01-01

The cryogenic refrigerator thermal design calculations establish design approach and basic sizing of the machine's elements. After the basic design is defined, effort concentrates on matching the thermodynamic design with that of the heat transfer devices (heat exchangers and regenerators). Typically, the heat transfer device configurations and volumes are adjusted to improve their heat transfer and pressure drop characteristics. These adjustments imply that changes be made to the active displaced volumes, compensating for the influence of the heat transfer devices on the thermodynamic processes of the working fluid. Then, once the active volumes are changed, the heat transfer devices require adjustment to account for the variations in flows, pressure levels, and heat loads. This iterative process is continued until the thermodynamic cycle parameters match the design of the heat transfer devices. By examing several matched designs, a near-optimum refrigerator is selected.

Natural convection of Al2O3-water nanofluid in a wavy enclosure

NASA Astrophysics Data System (ADS)

Leonard, Mitchell; Mozumder, Aloke K.; Mahmud, Shohel; Das, Prodip K.

2017-06-01

Natural convection heat transfer and fluid flow inside enclosures filled with fluids, such as air, water or oil, have been extensively analysed for thermal enhancement and optimisation due to their applications in many engineering problems, including solar collectors, electronic cooling, lubrication technologies, food processing and nuclear reactors. In comparison, little effort has been given to the problem of natural convection inside enclosures filled with nanofluids, while the addition of nanoparticles into a fluid base to alter thermal properties can be a feasible solution for many heat transfer problems. In this study, the problem of natural convection heat transfer and fluid flow inside a wavy enclosure filled with Al2O3-water nanofluid is investigated numerically using ANSYS-FLUENT. The effects of surface waviness and aspect ratio of the wavy enclosure on the heat transfer and fluid flow are analysed for various concentrations of Al2O3 nanoparticles in water. Flow fields and temperature fields are investigated and heat transfer rate is examined for different values of Rayleigh number. Results show that heat transfer within the enclosure can be enhanced by increasing surface waviness, aspect ratio or nanoparticles volume fraction. Changes in surface waviness have little effect on the heat transfer rate at low Rayleigh numbers, but when Ra ≥ 105 heat transfer increases with the increase of surface waviness from zero to higher values. Increasing the aspect ratio causes an increase in heat transfer rate, as the Rayleigh number increases the effect of changing aspect ratio is more apparent with the greatest heat transfer enhancement seen at higher Rayleigh numbers. Nanoparticles volume fraction has a little effect on the average Nusselt number at lower Rayleigh numbers when Ra ≥ 105 average Nusselt number increases with the increase of volume fraction. These findings provide insight into the heat transfer effects of using Al2O3-water nanofluid as a heat transfer medium and the effects of changing geometrical parameters, which will help in developing novel geometries with enhanced and controlled heat-transfer for solar collectors, electronic cooling, and food processing industries.

Simulation Approach for Microscale Noncontinuum Gas-Phase Heat Transfer

NASA Astrophysics Data System (ADS)

Torczynski, J. R.; Gallis, M. A.

2008-11-01

In microscale thermal actuators, gas-phase heat transfer from the heated beams to the adjacent unheated substrate is often the main energy-loss mechanism. Since the beam-substrate gap is comparable to the molecular mean free path, noncontinuum gas effects are important. A simulation approach is presented in which gas-phase heat transfer is described by Fourier's law in the bulk gas and by a wall boundary condition that equates the normal heat flux to the product of the gas-solid temperature difference and a heat transfer coefficient. The dimensionless parameters in this heat transfer coefficient are determined by comparison to Direct Simulation Monte Carlo (DSMC) results for heat transfer from beams of rectangular cross section to the substrate at free-molecular to near-continuum gas pressures. This simulation approach produces reasonably accurate gas-phase heat-transfer results for wide ranges of beam geometries and gas pressures. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

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

Convective Heat Transfer Enhancement Using Alternating Magnetic Fields and Particle Laden Fluid Applied to the Microscale

DTIC Science & Technology

2010-05-11

convective heat transfer , researchers have been drawn to the high heat flux potentials of microfluidic devices. Microchannel flows, with hydraulic...novel heat transfer enhancement technique proven on the conventional scale to the mini and microchannel scales. 1.3 Background: Conventional...S.G., 2004, “Single-Phase Heat Transfer Enhancement Techniques in Microchannel and Minichannel Flows,” International Conference on Microchannels

Direct-contact closed-loop heat exchanger

DOEpatents

Berry, G.F.; Minkov, V.; Petrick, M.

1981-11-02

A high temperature heat exchanger is disclosed which has a closed loop and a heat transfer liquid within the loop, the closed loop having a first horizontal channel with inlet and outlet means for providing direct contact of a first fluid at a first temperature with the heat transfer liquid, a second horizontal channel with inlet and outlet means for providing direct contact of a second fluid at a second temperature with the heat transfer liquid, and means for circulating the heat transfer liquid.

Preliminary Heat-Transfer Measurements on a Hypersonic Glide Configuration Having 79.5 degree Sweepback and 45 degree Dihedral at a Mach Number of 4.95

NASA Technical Reports Server (NTRS)

Stainback, Calvin

1960-01-01

An experimental investigation was conducted to evaluate the heat-transfer characteristics of a hypersonic glide configuration having 79.5 deg of sweepback (measured in the plane of the leading edges) and 45 of dihedral. The tests were conducted at a nominal Mach number of 4.95 and a stagnation temperature of 400 F. The test-section unit Reynolds number was varied from 1.95 x 10(exp 6) to 12.24 x 10(exp 6) per foot. The results indicated that the laminar-flow heat-transfer rate to the lower surface of the model decreased as the distance from the ridge line increased except for thermocouples located near the semispan at an angle of attack of 00 with respect to the plane of the leading edges. The heat-transfer distribution (local heating rate relative to the ridge-line heating rate) was similar to the theoretical heat-transfer distribution for a two-dimensional blunt body, if the ridge line was assumed to be the stagnation line, and could be predicted by this theory provided a modified Newtonian pressure distribution was used. Except in the vicinity of the apex, the ridge-line heat-transfer rate could also be predicted from two-dimensional blunt-body heat-transfer theory provided it was assumed that the stagnation-line heat-transfer rate varied as the cosine of the effective sweep (sine of the angle of attack of the ridge line). The heat-transfer level on the lower surface and the nondimensional heat-transfer distribution around the body on the lower surface were in qualitative agreement with the results of a geometric study of highly swept delta wings with large positive dihedrals made in reference 1.

19 CFR 146.61 - Constructive transfer to Customs territory.

Code of Federal Regulations, 2012 CFR

2012-04-01

... constructively transferred to Customs territory at that time, even though the merchandise remains physically in... time to be constructively transferred back into the zone in its previous zone status. ... 19 Customs Duties 2 2012-04-01 2012-04-01 false Constructive transfer to Customs territory. 146.61...

19 CFR 146.61 - Constructive transfer to Customs territory.

Code of Federal Regulations, 2014 CFR

2014-04-01

... constructively transferred to Customs territory at that time, even though the merchandise remains physically in... time to be constructively transferred back into the zone in its previous zone status. ... 19 Customs Duties 2 2014-04-01 2014-04-01 false Constructive transfer to Customs territory. 146.61...

19 CFR 146.61 - Constructive transfer to Customs territory.

Code of Federal Regulations, 2013 CFR

2013-04-01

... constructively transferred to Customs territory at that time, even though the merchandise remains physically in... time to be constructively transferred back into the zone in its previous zone status. ... 19 Customs Duties 2 2013-04-01 2013-04-01 false Constructive transfer to Customs territory. 146.61...

19 CFR 146.61 - Constructive transfer to Customs territory.

Code of Federal Regulations, 2011 CFR

2011-04-01

... constructively transferred to Customs territory at that time, even though the merchandise remains physically in... time to be constructively transferred back into the zone in its previous zone status. ... 19 Customs Duties 2 2011-04-01 2011-04-01 false Constructive transfer to Customs territory. 146.61...

19 CFR 146.61 - Constructive transfer to Customs territory.

Code of Federal Regulations, 2010 CFR

2010-04-01

... constructively transferred to Customs territory at that time, even though the merchandise remains physically in... time to be constructively transferred back into the zone in its previous zone status. ... 19 Customs Duties 2 2010-04-01 2010-04-01 false Constructive transfer to Customs territory. 146.61...

Heat Transfer in a Thermoacoustic Process

ERIC Educational Resources Information Center

Beke, Tamas

2012-01-01

Thermoacoustic instability is defined as the excitation of acoustic modes in chambers with heat sources due to the coupling between acoustic perturbations and unsteady heat addition. The major objective of this paper is to achieve accurate theoretical results in a thermoacoustic heat transfer process. We carry out a detailed heat transfer analysis…

Flow and heat transfer enhancement in tube heat exchangers

NASA Astrophysics Data System (ADS)

Sayed Ahmed, Sayed Ahmed E.; Mesalhy, Osama M.; Abdelatief, Mohamed A.

2015-11-01

The performance of heat exchangers can be improved to perform a certain heat-transfer duty by heat transfer enhancement techniques. Enhancement techniques can be divided into two categories: passive and active. Active methods require external power, such as electric or acoustic field, mechanical devices, or surface vibration, whereas passive methods do not require external power but make use of a special surface geometry or fluid additive which cause heat transfer enhancement. The majority of commercially interesting enhancement techniques are passive ones. This paper presents a review of published works on the characteristics of heat transfer and flow in finned tube heat exchangers of the existing patterns. The review considers plain, louvered, slit, wavy, annular, longitudinal, and serrated fins. This review can be indicated by the status of the research in this area which is important. The comparison of finned tubes heat exchangers shows that those with slit, plain, and wavy finned tubes have the highest values of area goodness factor while the heat exchanger with annular fin shows the lowest. A better heat transfer coefficient ha is found for a heat exchanger with louvered finned and thus should be regarded as the most efficient one, at fixed pumping power per heat transfer area. This study points out that although numerous studies have been conducted on the characteristics of flow and heat transfer in round, elliptical, and flat tubes, studies on some types of streamlined-tubes shapes are limited, especially on wing-shaped tubes (Sayed Ahmed et al. in Heat Mass Transf 50: 1091-1102, 2014; in Heat Mass Transf 51: 1001-1016, 2015). It is recommended that further detailed studies via numerical simulations and/or experimental investigations should be carried out, in the future, to put further insight to these fin designs.

Regional trends in radiogenic heat generation in the Precambrian basement of the Western Canadian Basin

NASA Astrophysics Data System (ADS)

Jones, F. W.; Majorowicz, J. A.

Radiogenic heat generation values for 381 basement samples from 229 sites in the western Canadian basin exhibit a lognormal frequency distribution. The mean value = 2.06 (S.D. = 1.22) µWm-3 is larger than the radiogenic heat generation values reported for the shield in the Superior (ca. 1.2 µWm-3, Jessop and Lewis, 1978) and Churchill (ca. 0.7 µWm-3, Drury, 1985) provinces. When equal Log A contour intervals are used to map the basement heat generation, three large zones of relatively high heat generation are found. One coincides with the Peace River Arch basement structure and one with the Athabasca axis (Darnley, 1981). There is no apparent indication of increased heat flow through the Paleozoic formations associated with these two zones. The third zone, in southwestern Saskatchewan, coincides with a high heat flow zone in the Swift Current area. The lack of correlation between heat flow and heat generation in Alberta may be due to the disturbance to the heat flow in the Paleozoic formations by water motion, or may indicate that the heat is from uranium, thorium and potassium isotope enrichment near the basement surface rather than enrichment throughout the entire upper crust.

Heterogonous Nanofluids for Nuclear Power Plants

NASA Astrophysics Data System (ADS)

Alammar, Khalid

2014-09-01

Nuclear reactions can be associated with high heat energy release. Extracting such energy efficiently requires the use of high-rate heat exchangers. Conventional heat transfer fluids, such as water and oils are limited in their thermal conductivity, and hence nanofluids have been introduced lately to overcome such limitation. By suspending metal nanoparticles with high thermal conductivity in conventional heat transfer fluids, thermal conductivity of the resulting homogeneous nanofluid is increased. Heterogeneous nanofluids offer yet more potential for heat transfer enhancement. By stratifying nanoparticles within the boundary layer, thermal conductivity is increased where temperature gradients are highest, thereby increasing overall heat transfer of a flowing fluid. In order to test the merit of this novel technique, a numerical study of a laminar pipe flow of a heterogeneous nanofluid was conducted. Effect of Iron-Oxide distribution on flow and heat transfer characteristics was investigated. With Iron-Oxide volume concentration of 0.009 in water, up to 50% local heat transfer enhancement was predicted for the heterogeneous compared to homogeneous nanofluids. Increasing the Reynolds number is shown to increase enhancement while having negligible effect on pressure drop. Using permanent magnets attached externally to the pipe, an experimental investigation conducted at MIT nuclear reactor laboratory for similar flow characteristics of a heterogeneous nanofluid have shown upto 160% enhancement in heat transfer. Such results show that heterogeneous nanofluids are promising for augmenting heat transfer rates in nuclear power heat exchanger systems.

Air/molten salt direct-contact heat-transfer experiment and economic analysis

NASA Astrophysics Data System (ADS)

Bohn, M. S.

1983-11-01

Direct-contact heat-transfer coefficients have been measured in a pilot-scale packed column heat exchanger for molten salt/air duty. Two types of commercial tower packings were tested: metal Raschig rings and initial Pall rings. Volumetric heat-transfer coefficients were measured and appeared to depend upon air flow but not on salt flow rate. An economic analysis was used to compare the cost-effectiveness of direct-contact heat exchange with finned-tube heat exchanger in this application. Incorporating the measured volumetric heat-transfer coefficients, a direct-contact system appeared to be from two to five times as cost-effective as a finned-tube heat exchanger, depending upon operating temperature. The large cost advantage occurs for higher operating temperatures (2700(0)C), where high rates of heat transfer and flexibility in materials choice give the cost advantage to the direct-contact heat exchanger.

Moisture effects in heat transfer through clothing systems for wildland firefighters.

PubMed

Lawson, Lelia K; Crown, Elizabeth M; Ackerman, Mark Y; Dale, J Douglas

2004-01-01

Wildland firefighters work in unfavourable environments involving both heat and moisture. Moisture in clothing systems worn by wildland firefighters may increase or decrease heat transfer, depending on its source and location in the clothing system, location on the body, timing of application and degree of sorption. In this experiment, 4 outerwear/underwear combinations were exposed to 1 of 5 different conditions varying on amount and location of moisture. The fabric systems were then exposed to either a high-heat-flux flame exposure (83 kW/m(2)) or a low-heat-flux radiant exposure (10 kW/m(2)). Under high-heat-flux flame exposures, external moisture tended to decrease heat transfer through the fabric systems, while internal moisture tended to increase heat transfer. Under low-heat-flux radiant exposures, internal moisture decreased heat transfer through the fabric systems. The nature and extent of such differences was fabric dependent. Implications for test protocol development are discussed.

Hypersolidus geothermal energy from the moving freeze-fracture-flow boundary

NASA Astrophysics Data System (ADS)

Carrigan, Charles; Eichelberger, John; Sigmundsson, Freysteinn; Papale, Paolo; Sun, Yunwei

2014-05-01

Rhyolitic magmas at low pressure undergo much of their crystallization over a small temperature interval just above the solidus. This hypersolidus material has a high energy density and effective heat capacity because of stored heat of crystallization, yet may sustain fractures and therefore admit heat exchange with fluids because of its interlocking crystal framework. Rhyolitic magmas emplaced near the liquidus should at first cool rapidly, owing to internal convection, modest crystallization with declining temperature, and extreme temperature gradients at their boundaries. However, once the solidus is approached the rapid rise in effective heat capacity should result in low temperature gradients and rates of heat flow within the bodies. They are suspended for a time in the hypersolidus state. Prodigious quantities of heat can be released from these thermal masses by hydrothermal systems, natural or perhaps stimulated, fracturing their way inward from the margins. The fracture front drives the solidus isotherm ahead of it. Heat of crystallization in front of the advancing solidus is transferred across the thin, moving boundary zone to the external fluid, which advects it away. Once the material is below (outboard of) the solidus, it behaves as normal rock and cools rapidly, having a heat capacity only about 20% that of water. Variations on this theme were published by Lister (1974) for mid-ocean ridges, Hardee (1980) for lava lakes, and Bjornsson et al (1982) for Grimsvotn and Heimaey, who cited possible geothermal energy exploitiation. This scenario is consistent with a number of observations: 1. The geophysical rarity of imaging mostly liquid magma in the shallow crust, despite common petrologic evidence that silicic magma has undergone shallow storage. 2. More common imaging of "partial melt" volumes, whose inferred properties suggest some, but not dominant proportion of melt. 3. Evidence that pure-melt rhyolitic eruptions may have drained relatively shallow hypersolidus plutons. 4. Downward propagating thin conductive boundary zone observed in repeated coring of Kilauea Iki lava lake, Hawaii 5. Record enthalpy flow and temperature during flow-testing of Iceland Deep Drilling Project (IDDP)-1 in Krafla Caldera by Landsvirkjun Co. Production came from a 2.1-km-deep 500oC "magma" contact zone, from the vicinity of which fresh rhyolite glass-bearing felsite and crystal-poor rhyolite glass fragments were recovered. The hypothesis of a moving freeze-fracture-flow boundary raises the possibility of ultra-high-temperature, natural or engineered geothermal systems in volcanic areas. We believe that this prospect, as well as the benefit to understanding volcanic hazards at restless calderas, gives merit to further exploration of the hypersolidus regime beneath Krafla Caldera.

Development of a High-Performance Fin-and-Tube Heat Exchanger with Vortex Generators for a Vending Machine

NASA Astrophysics Data System (ADS)

Iwasaki, Masamichi; Saito, Hiroshi; Mochizuki, Sadanari; Murata, Akira

The effect of delta-wing-vortex generators (combination of a delta wing and a delta winglet pair) on the heat transfer performance of fin-and-tube heat exchangers for vending machines has been investegated. Flow visualizations, numerical simulations and heat transfer experiments were conducted to find an optimum geometrical shape and arrangement of the vortex generators. Maximum heat transfer enhancement was achieved by the combination of (a) the delta wing with the apex angle of 86 degrees and (b) the delta winglet pair with the inline angle of 45 degrees. In relatively low Reynolds number range, about 40 % increase in heat transfer coefficient was attained with the above mentioned combination of the vortex generators compared to the ordinary heat exchangers with plain fins. It was revealed that the heat transfer enhancement was attributed to (1) the longitudinal vortexes generated by the delta wing and (2) the reduction of wake area behind the tube. It was also found that an increase in the apex angle of the delta wing brought about heat transfer enhancement, and the scale as well as the streggth of the induced longitudinal vortices played an important role in the heat transfer performance.

Investigation of Heat Transfer in Straight and Curved Rectangular Ducts for Laminar and Transition Flows.

DTIC Science & Technology

1981-06-01

in order that the complete theoretical solution of the effects of the Taylor- Gortler vortices on heat transfer be explained. In 1977, - R. Kahawita ...Kelleher, M.D., "Taylor- Gortler Vortices and Their Effect on Heat Transfer" Journal of Heat Transfer, V.92, pp. 101-112, February 1970. 20. Kahawita , R

Evaluation of generalized heat-transfer coefficients in pilot AFBC units

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

Grewal, N.S.

Experimental data for heat transfer rates as obtained in a 0.209m/sup 2/ AFBC unit at the GFETC is examined in the light of the existing four correlations for heat transfer coefficient between an immersed staggered array of horizontal tubes and a gas-solid fluidized bed. The predicted values of heat transfer coefficient from the correlations proposed by Grewal and Bansal are found to be in good agreement with the experimental values of heat transfer coefficient when the contribution due to radiation is also included.

Evaluation of generalized heat transfer coefficients in pilot AFBC units

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

Grewal, N.S.

Experimental data for heat transfer rates as obtained in a 0.209m/sup 2/ AFBC unit at the GFETC is examined in the light of the existing four correlations for heat transfer coefficient between an immersed staggered array of horizontal tubes and a gas-solid fluidized bed. The predicted values of heat transfer coefficient from the correlations proposed by Grewal and Bansal are found to be in good agreement with the experimental values of heat transfer coefficient when the contribution due to radiation is also included.

Turbine Vane External Heat Transfer. Volume 1: Analytical and Experimental Evaluation of Surface Heat Transfer Distributions with Leading Edge Showerhead Film Cooling

NASA Technical Reports Server (NTRS)

Turner, E. R.; Wilson, M. D.; Hylton, L. D.; Kaufman, R. M.

1985-01-01

Progress in predictive design capabilities for external heat transfer to turbine vanes was summarized. A two dimensional linear cascade (previously used to obtain vane surface heat transfer distributions on nonfilm cooled airfoils) was used to examine the effect of leading edge shower head film cooling on downstream heat transfer. The data were used to develop and evaluate analytical models. Modifications to the two dimensional boundary layer model are described. The results were used to formulate and test an effective viscosity model capable of predicting heat transfer phenomena downstream of the leading edge film cooling array on both the suction and pressure surfaces, with and without mass injection.

Two-dimensional numerical modeling and solution of convection heat transfer in turbulent He II

NASA Technical Reports Server (NTRS)

Zhang, Burt X.; Karr, Gerald R.

1991-01-01

Numerical schemes are employed to investigate heat transfer in the turbulent flow of He II. FEM is used to solve a set of equations governing the heat transfer and hydrodynamics of He II in the turbulent regime. Numerical results are compared with available experimental data and interpreted in terms of conventional heat transfer parameters such as the Prandtl number, the Peclet number, and the Nusselt number. Within the prescribed Reynolds number domain, the Gorter-Mellink thermal counterflow mechanism becomes less significant, and He II acts like an ordinary fluid. The convection heat transfer characteristics of He II in the highly turbulent regime can be successfully described by using the conventional turbulence and heat transfer theories.

Analysis of buoyancy effect on fully developed laminar heat transfer in a rotating tube

NASA Technical Reports Server (NTRS)

Siegel, R.

1985-01-01

Laminar heat transfer is analyzed in a tube rotating about an axis perpendicular to the tube axis. The solution applies for flow that is either radially outward from the axis of rotation, or radially inward toward the axis of rotation. The conditions are fully developed, and there is uniform heat addition at the tube wall. The analysis is performed by expanding velocities and temperature in power series using the Taylor number as a perturbation parameter. Coriolis and buoyancy forces caused by tube rotation are included, and the solution is calculated through second-order terms. The secondary flow induced by the Coriolis terms always tends to increase the heat transfer coefficient; this effect can dominate for small wall heating. For radial inflow, buoyancy also tends to improve heat transfer. For radial outflow, however, buoyancy tends to reduce heat transfer; for large wall heating this effect can dominate, and there is a net reduction in heat transfer coefficient.

Experimental study of laminar forced convective heat transfer of deionized water based copper (I) oxide nanofluids in a tube with constant wall heat flux

NASA Astrophysics Data System (ADS)

Umer, Asim; Naveed, Shahid; Ramzan, Naveed

2016-10-01

Nanofluids, having 1-100 nm size particles in any base fluid are promising fluid for heat transfer intensification due to their enhanced thermal conductivity as compared with the base fluid. The forced convection of nanofluids is the major practical application in heat transfer equipments. In this study, heat transfer enhancements at constant wall heat flux under laminar flow conditions were investigated. Nanofluids of different volume fractions (1, 2 and 4 %) of copper (I) oxide nanoparticles in deionized water were prepared using two step technique under mechanical mixing and ultrasonication. The results were investigated by increasing the Reynolds number of the nanofluids at constant heat flux. The trends of Nusselt number variation with dimensionless length (X/D) and Reynolds numbers were studied. It was observed that heat transfer coefficient increases with increases particles volume concentration and Reynolds number. The maximum enhancement in heat transfer coefficient of 61 % was observed with 4 % particle volume concentration at Reynolds number (Re ~ 605).

Acoustically enhanced heat exchange and drying apparatus

DOEpatents

Bramlette, T. Tazwell; Keller, Jay O.

1989-01-01

A heat transfer apparatus includes a first chamber having a first heat transfer gas inlet, a second heat transfer gas inlet, and an outlet. A first heat transfer gas source provides a first gas flow to the first chamber through the first heat transfer gas inlet. A second gas flow through a second chamber connected to the side of the first chamber, generates acoustic waves which bring about acoustical coupling of the first and second gases in the acoustically augmented first chamber. The first chamber may also include a material inlet for receiving material to be dried, in which case the gas outlet serves as a dried material and gas outlet.

Heat transfer assembly for a fluorescent lamp and fixture

DOEpatents

Siminovitch, M.J.; Rubenstein, F.M.; Whitman, R.E.

1992-12-29

In a lighting fixture including a lamp and a housing, a heat transfer structure is disclosed for reducing the minimum lamp wall temperature of a fluorescent light bulb. The heat transfer structure, constructed of thermally conductive material, extends from inside the housing to outside the housing, transferring heat energy generated from a fluorescent light bulb to outside the housing where the heat energy is dissipated to the ambient air outside the housing. Also disclosed is a method for reducing minimum lamp wall temperatures. Further disclosed is an improved lighting fixture including a lamp, a housing and the aforementioned heat transfer structure. 11 figs.

Heat transfer and friction characteristics of the microfluidic heat sink with variously-shaped ribs for chip cooling.

PubMed

Wang, Gui-Lian; Yang, Da-Wei; Wang, Yan; Niu, Di; Zhao, Xiao-Lin; Ding, Gui-Fu

2015-04-22

This paper experimentally and numerically investigated the heat transfer and friction characteristics of microfluidic heat sinks with variously-shaped micro-ribs, i.e., rectangular, triangular and semicircular ribs. The micro-ribs were fabricated on the sidewalls of microfluidic channels by a surface-micromachining micro-electro-mechanical system (MEMS) process and used as turbulators to improve the heat transfer rate of the microfluidic heat sink. The results indicate that the utilizing of micro-ribs provides a better heat transfer rate, but also increases the pressure drop penalty for microchannels. Furthermore, the heat transfer and friction characteristics of the microchannels are strongly affected by the rib shape. In comparison, the triangular ribbed microchannel possesses the highest Nusselt number and friction factor among the three rib types.

Fast reactor power plant design having heat pipe heat exchanger

DOEpatents

Huebotter, P.R.; McLennan, G.A.

1984-08-30

The invention relates to a pool-type fission reactor power plant design having a reactor vessel containing a primary coolant (such as liquid sodium), and a steam expansion device powered by a pressurized water/steam coolant system. Heat pipe means are disposed between the primary and water coolants to complete the heat transfer therebetween. The heat pipes are vertically oriented, penetrating the reactor deck and being directly submerged in the primary coolant. A U-tube or line passes through each heat pipe, extended over most of the length of the heat pipe and having its walls spaced from but closely proximate to and generally facing the surrounding walls of the heat pipe. The water/steam coolant loop includes each U-tube and the steam expansion device. A heat transfer medium (such as mercury) fills each of the heat pipes. The thermal energy from the primary coolant is transferred to the water coolant by isothermal evaporation-condensation of the heat transfer medium between the heat pipe and U-tube walls, the heat transfer medium moving within the heat pipe primarily transversely between these walls.

Fast reactor power plant design having heat pipe heat exchanger

DOEpatents

Huebotter, Paul R.; McLennan, George A.

1985-01-01

The invention relates to a pool-type fission reactor power plant design having a reactor vessel containing a primary coolant (such as liquid sodium), and a steam expansion device powered by a pressurized water/steam coolant system. Heat pipe means are disposed between the primary and water coolants to complete the heat transfer therebetween. The heat pipes are vertically oriented, penetrating the reactor deck and being directly submerged in the primary coolant. A U-tube or line passes through each heat pipe, extended over most of the length of the heat pipe and having its walls spaced from but closely proximate to and generally facing the surrounding walls of the heat pipe. The water/steam coolant loop includes each U-tube and the steam expansion device. A heat transfer medium (such as mercury) fills each of the heat pipes. The thermal energy from the primary coolant is transferred to the water coolant by isothermal evaporation-condensation of the heat transfer medium between the heat pipe and U-tube walls, the heat transfer medium moving within the heat pipe primarily transversely between these walls.

A one-dimensional heat transfer model for parallel-plate thermoacoustic heat exchangers.

PubMed

de Jong, J A; Wijnant, Y H; de Boer, A

2014-03-01

A one-dimensional (1D) laminar oscillating flow heat transfer model is derived and applied to parallel-plate thermoacoustic heat exchangers. The model can be used to estimate the heat transfer from the solid wall to the acoustic medium, which is required for the heat input/output of thermoacoustic systems. The model is implementable in existing (quasi-)1D thermoacoustic codes, such as DeltaEC. Examples of generated results show good agreement with literature results. The model allows for arbitrary wave phasing; however, it is shown that the wave phasing does not significantly influence the heat transfer.

A turbulent plane jet impinging nearby and far from a flat plate

NASA Astrophysics Data System (ADS)

Maurel, S.; Solliec, C.

Plane air jets presenting an impact find applications in many industrial devices. They can be found in installations of heating, cooling or drying, cleaning, pulverization, or containment of polluted environments. Other applications can be found in the ventilation of buildings. The correct design of these kinds of installations requires thorough knowledge of the structure of the jet from the cinematic point of view. With this intention a test bench with variable geometry was developed. Then, using laser Doppler velocimetry (LDV) and particle image velocimetry (PIV), it is possible to analyze the development of the jet for various geometrical and cinematic configurations. It appears that the development of the jet is independent of the Reynolds number, and the velocity decrease in the developed and impinging zones can be characterized by using very simple laws. Furthermore, by PIV visualization of the impinging zone, it has been possible to highlight the causes of mass transfer through the jet.

Two-phase flows within systems with ambient pressure

NASA Technical Reports Server (NTRS)

Hendricks, R. C.; Braun, M. J.; Wheeler, R. L., III; Mullen, R. L.

1985-01-01

In systems where the design inlet and outlet pressures are maintained above the thermodynamic critical pressure, it is often assumed that two phase flows within the system cannot occur. Designers rely on this simple rule of thumb to circumvent problems associated with a highly compressible two phase flow occurring within the supercritical pressure system along with the uncertainties in rotordynamics, load capacity, heat transfer, fluid mechanics, and thermophysical property variations. The simple rule of thumb is adequate in many low power designs but is inadequate for high performance turbomachines and linear systems, where two phase regions can exist even though outlet pressure is greater than critical pressure. Rotordynamic-fluid-mechanic restoring forces depend on momentum differences, and those for a two phase zone can differ significantly from those for a single-phase zone. Using the Reynolds equation the angular velocity, eccentricity, geometry, and ambient conditions are varied to determine the point of two phase flow incipience.

On ionizing shock waves

NASA Astrophysics Data System (ADS)

Kaniel, A.; Igra, O.; Ben-Dor, G.; Mond, M.

The flow field in the ionizing relaxation zone developed behind a normal shock wave in an electrically neutral, homogeneous, two temperature mixture of thermally ideal gases (molecules, atoms, ions, electrons) was numerically solved. The heat transfer between the electron gas and the other components was taken into account while all the other transport phenomena (molecular, turbulent and radiative) were neglected in the relaxation zone, since it is dominated by inelastic collisions. The threshold cross sections measured by Specht (1981), for excitation of argon by electron collisions, were used. The calculated results show good agreement with the results of the shock tube experiments presented by Glass and Liu (1978), especially in the electron avalanche region. A critical examination was made of the common assumptions regarding the average energy with which electrons are produced by atom-atom collisions and the relative effectiveness of atom-atom collisions (versus electron-atom collisions) in ionizing excited argon.

Microstructure and Mechanical Properties of Laser Welded Titanium 6Al-4V

NASA Astrophysics Data System (ADS)

Mazumder, J.; Steen, W. M.

1982-05-01

Laser butt welds were fabricated in a titanium alloy (Ti-6A1-4V, AMS 4911-Tal0 BSS, annealed) using a Control Laser 2 kW CW CO2 laser. The relationships between the weld microstructure and mechanical properties are described and compared to the theoretical thermal history of the weld zone as calculated from a three-dimensional heat transfer model of the process. The structure of the weld zone was examined by radiography to detect any gross porosity as well as by both optical and electron microscopy in order to identify the microstructure. The oxygen pick-up during gas shielded laser welding was analyzed to correlate further with the observed mechanical properties. It was found that optimally fabricated laser welds have a very good combination of weld microstructure and mechanical properties, ranking this process as one which can produce high quality welds.

Energy efficient engine combustor test hardware detailed design report

NASA Technical Reports Server (NTRS)

Zeisser, M. H.; Greene, W.; Dubiel, D. J.

1982-01-01

The combustor for the Energy Efficient Engine is an annular, two-zone component. As designed, it either meets or exceeds all program goals for performance, safety, durability, and emissions, with the exception of oxides of nitrogen. When compared to the configuration investigated under the NASA-sponsored Experimental Clean Combustor Program, which was used as a basis for design, the Energy Efficient Engine combustor component has several technology advancements. The prediffuser section is designed with short, strutless, curved-walls to provide a uniform inlet airflow profile. Emissions control is achieved by a two-zone combustor that utilizes two types of fuel injectors to improve fuel atomization for more complete combustion. The combustor liners are a segmented configuration to meet the durability requirements at the high combustor operating pressures and temperatures. Liner cooling is accomplished with a counter-parallel FINWALL technique, which provides more effective heat transfer with less coolant.

46 CFR 153.430 - Heat transfer systems; general.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 5 2013-10-01 2013-10-01 false Heat transfer systems; general. 153.430 Section 153.430... Temperature Control Systems § 153.430 Heat transfer systems; general. Each cargo cooling system required by... separated from all other cooling and heating systems; and (c) Allow manual regulation of the system's heat...

46 CFR 153.430 - Heat transfer systems; general.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 5 2012-10-01 2012-10-01 false Heat transfer systems; general. 153.430 Section 153.430... Temperature Control Systems § 153.430 Heat transfer systems; general. Each cargo cooling system required by... separated from all other cooling and heating systems; and (c) Allow manual regulation of the system's heat...

46 CFR 153.430 - Heat transfer systems; general.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 5 2014-10-01 2014-10-01 false Heat transfer systems; general. 153.430 Section 153.430... Temperature Control Systems § 153.430 Heat transfer systems; general. Each cargo cooling system required by... separated from all other cooling and heating systems; and (c) Allow manual regulation of the system's heat...

46 CFR 153.430 - Heat transfer systems; general.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 5 2011-10-01 2011-10-01 false Heat transfer systems; general. 153.430 Section 153.430... Temperature Control Systems § 153.430 Heat transfer systems; general. Each cargo cooling system required by... separated from all other cooling and heating systems; and (c) Allow manual regulation of the system's heat...

46 CFR 153.430 - Heat transfer systems; general.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 5 2010-10-01 2010-10-01 false Heat transfer systems; general. 153.430 Section 153.430... Temperature Control Systems § 153.430 Heat transfer systems; general. Each cargo cooling system required by... separated from all other cooling and heating systems; and (c) Allow manual regulation of the system's heat...

The calculating study of the moisture transfer influence at the temperature field in a porous wet medium with internal heat sources

NASA Astrophysics Data System (ADS)

Kuzevanov, V. S.; Garyaev, A. B.; Zakozhurnikova, G. S.; Zakozhurnikov, S. S.

2017-11-01

A porous wet medium with solid and gaseous components, with distributed or localized heat sources was considered. The regimes of temperature changes at the heating at various initial material moisture were studied. Mathematical model was developed applied to the investigated wet porous multicomponent medium with internal heat sources, taking into account the transfer of the heat by heat conductivity with variable thermal parameters and porosity, heat transfer by radiation, chemical reactions, drying and moistening of solids, heat and mass transfer of volatile products of chemical reactions by flows filtration, transfer of moisture. The algorithm of numerical calculation and the computer program that implements the proposed mathematical model, allowing to study the dynamics of warming up at a local or distributed heat release, in particular the impact of the transfer of moisture in the medium on the temperature field were created. Graphs of temperature change were obtained at different points of the graphics with different initial moisture. Conclusions about the possible control of the regimes of heating a solid porous body by the initial moisture distribution were made.

Heat Transfer of Nanofluid in a Double Pipe Heat Exchanger.

PubMed

Aghayari, Reza; Maddah, Heydar; Zarei, Malihe; Dehghani, Mehdi; Kaskari Mahalle, Sahar Ghanbari

2014-01-01

This paper investigates the enhancement of heat transfer coefficient and Nusselt number of a nanofluid containing nanoparticles (γ-AL2O3) with a particle size of 20 nm and volume fraction of 0.1%-0.3% (V/V). Effects of temperature and concentration of nanoparticles on Nusselt number changes and heat transfer coefficient in a double pipe heat exchanger with counter turbulent flow are investigated. Comparison of experimental results with valid theoretical data based on semiempirical equations shows an acceptable agreement. Experimental results show a considerable increase in heat transfer coefficient and Nusselt number up to 19%-24%, respectively. Also, it has been observed that the heat transfer coefficient increases with the operating temperature and concentration of nanoparticles.

Quantification of the heat exchange of chicken eggs.

PubMed

Van Brecht, A; Hens, H; Lemaire, J L; Aerts, J M; Degraeve, P; Berckmans, D

2005-03-01

In the incubation process of domestic avian eggs, the development of the embryo is mainly influenced by the physical microenvironment around the egg. Only small spatiotemporal deviations in the optimal incubator air temperature are allowed to optimize hatchability and hatchling quality. The temperature of the embryo depends on 3 factors: (1) the air temperature, (2) the exchange of heat between the egg and its microenvironment and (3) the time-variable heat production of the embryo. Theoretical estimates on the heat exchange between an egg and its physical microenvironment are approximated using equations that assume an approximate spherical shape for eggs. The objective of this research was to determine the heat transfer between the eggshell and its microenvironment and then compare this value to various theoretical estimates. By using experimental data, the overall and the convective heat transfer coefficients were determined as a function of heat production, air humidity, air speed, and air temperature. Heat transfer was not affected by air humidity but solely by air temperature, embryonic heat generation, and air speed and flow around eggs. Also, heat transfer in forced-air incubators occurs mainly by convective heat loss, which is dependent on the speed of airflow. A vertical airflow is more efficient than a horizontal airflow in transferring heat from the egg. We showed that describing an egg as a sphere underestimated convective heat transfer by 33% and was, therefore, too simplistic to accurately assess actual heat transfer from real eggs.

Nano-inspired smart interfaces: fluidic interactivity and its impact on heat transfer

NASA Astrophysics Data System (ADS)

Kim, Beom Seok; Lee, Byoung In; Lee, Namkyu; Choi, Geehong; Gemming, Thomas; Cho, Hyung Hee

2017-03-01

Interface-inspired convection is a key heat transfer scheme for hot spot cooling and thermal energy transfer. An unavoidable trade-off of the convective heat transfer is pressure loss caused by fluidic resistance on an interface. To overcome this limitation, we uncover that nano-inspired interfaces can trigger a peculiar fluidic interactivity, which can pursue all the two sides of the coin: heat transfer and fluidic friction. We demonstrate the validity of a quasi-fin effect of Si-based nanostructures based on conductive capability of heat dissipation valid under the interactivity with fluidic viscous sublayer. The exclusive fluid-interface friction is achieved when the height of the nanostructures is much less than the thickness of the viscous sublayers in the turbulent regime. The strategic nanostructures show an enhancement of heat transfer coefficients in the wall jet region by more than 21% without any significant macroscale pressure loss under single-phase impinging jet. Nanostructures guaranteeing fluid access via an equivalent vacancy larger than the diffusive path length of viscid flow lead to local heat transfer enhancement of more than 13% at a stagnation point. Functional nanostructures will give shape to possible breakthroughs in heat transfer and its optimization can be pursued for engineered systems.

Evaporation heat transfer of carbon dioxide at low temperature inside a horizontal smooth tube

NASA Astrophysics Data System (ADS)

Yoon, Jung-In; Son, Chang-Hyo; Jung, Suk-Ho; Jeon, Min-Ju; Yang, Dong-Il

2017-05-01

In this paper, the evaporation heat transfer coefficient of carbon dioxide at low temperature of -30 to -20 °C in a horizontal smooth tube was investigated experimentally. The test devices consist of mass flowmeter, pre-heater, magnetic gear pump, test section (evaporator), condenser and liquid receiver. Test section is made of cooper tube. Inner and outer diameter of the test section is 8 and 9.52 mm, respectively. The experiment is conducted at mass fluxes from 100 to 300 kg/m2 s, saturation temperature from -30 to -20 °C. The main results are summarized as follows: In case that the mass flux of carbon dioxide is 100 kg/m2 s, the evaporation heat transfer coefficient is almost constant regardless of vapor quality. In case of 200 and 300 kg/m2 s, the evaporation heat transfer coefficient increases steadily with increasing vapor quality. For the same mass flux, the evaporation heat transfer coefficient increases as the evaporation temperature of the refrigerant decreases. In comparison of heat transfer correlations with the experimental result, the evaporation heat transfer correlations do not predict them exactly. Therefore, more accurate heat transfer correlation than the previous one is required.

Computational Fluid Dynamics Based Extraction of Heat Transfer Coefficient in Cryogenic Propellant Tanks

NASA Technical Reports Server (NTRS)

Yang, H. Q.; West, Jeff

2015-01-01

Current reduced-order thermal model for cryogenic propellant tanks is based on correlations built for flat plates collected in the 1950's. The use of these correlations suffers from: inaccurate geometry representation; inaccurate gravity orientation; ambiguous length scale; and lack of detailed validation. The work presented under this task uses the first-principles based Computational Fluid Dynamics (CFD) technique to compute heat transfer from tank wall to the cryogenic fluids, and extracts and correlates the equivalent heat transfer coefficient to support reduced-order thermal model. The CFD tool was first validated against available experimental data and commonly used correlations for natural convection along a vertically heated wall. Good agreements between the present prediction and experimental data have been found for flows in laminar as well turbulent regimes. The convective heat transfer between tank wall and cryogenic propellant, and that between tank wall and ullage gas were then simulated. The results showed that commonly used heat transfer correlations for either vertical or horizontal plate over predict heat transfer rate for the cryogenic tank, in some cases by as much as one order of magnitude. A characteristic length scale has been defined that can correlate all heat transfer coefficients for different fill levels into a single curve. This curve can be used for the reduced-order heat transfer model analysis.

CFD Extraction of Heat Transfer Coefficient in Cryogenic Propellant Tanks

NASA Technical Reports Server (NTRS)

Yang, H. Q.; West, Jeff

2015-01-01

Current reduced-order thermal model for cryogenic propellant tanks is based on correlations built for flat plates collected in the 1950's. The use of these correlations suffers from inaccurate geometry representation; inaccurate gravity orientation; ambiguous length scale; and lack of detailed validation. This study uses first-principles based CFD methodology to compute heat transfer from the tank wall to the cryogenic fluids and extracts and correlates the equivalent heat transfer coefficient to support reduced-order thermal model. The CFD tool was first validated against available experimental data and commonly used correlations for natural convection along a vertically heated wall. Good agreements between the present prediction and experimental data have been found for flows in laminar as well turbulent regimes. The convective heat transfer between the tank wall and cryogenic propellant, and that between the tank wall and ullage gas were then simulated. The results showed that the commonly used heat transfer correlations for either vertical or horizontal plate over-predict heat transfer rate for the cryogenic tank, in some cases by as much as one order of magnitude. A characteristic length scale has been defined that can correlate all heat transfer coefficients for different fill levels into a single curve. This curve can be used for the reduced-order heat transfer model analysis.

A Study of Heat Transfer and Flow Characteristics of Rising Taylor Bubbles

NASA Technical Reports Server (NTRS)

Scammell, Alexander David

2016-01-01

Practical application of flow boiling to ground- and space-based thermal management systems hinges on the ability to predict the systems heat removal capabilities under expected operating conditions. Research in this field has shown that the heat transfer coefficient within two-phase heat exchangers can be largely dependent on the experienced flow regime. This finding has inspired an effort to develop mechanistic heat transfer models for each flow pattern which are likely to outperform traditional empirical correlations. As a contribution to the effort, this work aimed to identify the heat transfer mechanisms for the slug flow regime through analysis of individual Taylor bubbles.An experimental apparatus was developed to inject single vapor Taylor bubbles into co-currently flowing liquid HFE 7100. The heat transfer was measured as the bubble rose through a 6 mm inner diameter heated tube using an infrared thermography technique. High-speed flow visualization was obtained and the bubble film thickness measured in an adiabatic section. Experiments were conducted at various liquid mass fluxes (43-200 kgm2s) and gravity levels (0.01g-1.8g) to characterize the effect of bubble drift velocityon the heat transfer mechanisms. Variable gravity testing was conducted during a NASA parabolic flight campaign.Results from the experiments showed that the drift velocity strongly affects the hydrodynamics and heat transfer of single elongated bubbles. At low gravity levels, bubbles exhibited shapes characteristic of capillary flows and the heat transfer enhancement due to the bubble was dominated by conduction through the thin film. At moderate to high gravity, traditional Taylor bubbles provided small values of enhancement within the film, but large peaks in the wake heat transfer occurred due to turbulent vortices induced by the film plunging into the trailing liquid slug. Characteristics of the wake heat transfer profiles were analyzed and related to the predicted velocity field. Results were compared and shown to agree with numerical simulations of colleagues from EPFL, Switzerland.In addition, a preliminary study was completed on the effect of a Taylor bubble passing through nucleate flow boiling, showing that the thinning thermal boundary layer within the film suppressed nucleation, thereby decreasing the heat transfer coefficient.

Thermal Enhancement of Silicon Carbide (SiC) Power Electronics and Laser Bars: Statistical Design Optimization of a Liquid-Cooled Power Electronic Heat Sink

DTIC Science & Technology

2015-08-01

Forced Convective Heat Transfer Across a Pin Fin Micro Heat Sink”, International Journal of Heat and Mass Transfer 48 (2005) 3615-3627. 3. Cao...from Pin Fins Situated in an Oncoming Longitudinal Flow Which Turns to Crossflow”, International Journal of Heat and Mass Transfer, Vol. 25 No. 5...Flow Forced Convection”, International Journal of Heat and Mass Transfer, Vol. 39, No. 2, pp. 311-317, 1996. 11. Khan, W., Culham, J., and Yovanovich

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.

Heating systems for heating subsurface formations

DOEpatents

Nguyen, Scott Vinh [Houston, TX; Vinegar, Harold J [Bellaire, TX

2011-04-26

Methods and systems for heating a subsurface formation are described herein. A heating system for a subsurface formation includes a sealed conduit positioned in an opening in the formation and a heat source. The sealed conduit includes a heat transfer fluid. The heat source provides heat to a portion of the sealed conduit to change phase of the heat transfer fluid from a liquid to a vapor. The vapor in the sealed conduit rises in the sealed conduit, condenses to transfer heat to the formation and returns to the conduit portion as a liquid.

Heat transfer coefficients for staggered arrays of short pin fins

NASA Technical Reports Server (NTRS)

Vanfossen, G. J.

1981-01-01

Short pin fins are often used to increase that heat transfer to the coolant in the trailing edge of a turbine blade. Due primarily to limits of casting technology, it is not possible to manufacture pins of optimum length for heat transfer purposes in the trailing edge region. In many cases the pins are so short that they actually decrease the total heat transfer surface area compared to a plain wall. A heat transfer data base for these short pins is not available in the literature. Heat transfer coefficients on pin and endwall surfaces were measured for several staggered arrays of short pin fins. The measured Nusselt numbers when plotted versus Reynolds numbers were found to fall on a single curve for all surfaces tested. The heat transfer coefficients for the short pin fins (length to diameter ratios of 1/2 and 2) were found to be about a factor of two lower than data from the literature for longer pin arrays (length to diameter ratios of about 8).

Flow drag and heat transfer characteristics of drag-reducing nanofluids with CuO nanoparticles

NASA Astrophysics Data System (ADS)

Wang, Ping-Yang; Wang, Xue-Jiao; Liu, Zhen-Hua

2017-02-01

A new kind of aqueous CuO nanofluid with drag-reducing performance was developed. The new working fluid was an aqueous CTAC (cetyltrimethyl ammonium chloride) solution with CuO nanoparticles added and has both special effects of drag-reducing and heat transfer enhancement. An experiment was carried out to investigate the forced convective flow and heat transfer characteristics of conventional drag reducing fluid (aqueous CTAC solution) and the new drag-reducing nanofluid in a test tube with an inner diameter of 25.6 mm. Results indicated that there were no obvious differences of the drag-reducing characteristics between conventional drag reducing fluid and new drag-reducing nanofluid. However, their heat transfer characteristics were obvious different. The heat transfer characteristics of the new drag-reducing nanofluid significantly depend on the liquid temperature, the nanoparticle concentration and the CTAC concentration. The heat transfer enhancement technology of nanofluid could be applied to solve the problem of heat transfer deterioration for conventional drag-reducing fluids.

Sphere Drag and Heat Transfer

NASA Astrophysics Data System (ADS)

Duan, Zhipeng; He, Boshu; Duan, Yuanyuan

2015-07-01

Modelling fluid flows past a body is a general problem in science and engineering. Historical sphere drag and heat transfer data are critically examined. The appropriate drag coefficient is proposed to replace the inertia type definition proposed by Newton. It is found that the appropriate drag coefficient is a desirable dimensionless parameter to describe fluid flow physical behavior so that fluid flow problems can be solved in the simple and intuitive manner. The appropriate drag coefficient is presented graphically, and appears more general and reasonable to reflect the fluid flow physical behavior than the traditional century old drag coefficient diagram. Here we present drag and heat transfer experimental results which indicate that there exists a relationship in nature between the sphere drag and heat transfer. The role played by the heat flux has similar nature as the drag. The appropriate drag coefficient can be related to the Nusselt number. This finding opens new possibilities in predicting heat transfer characteristics by drag data. As heat transfer for flow over a body is inherently complex, the proposed simple means may provide an insight into the mechanism of heat transfer for flow past a body.

Sphere Drag and Heat Transfer.

PubMed

Duan, Zhipeng; He, Boshu; Duan, Yuanyuan

2015-07-20

Modelling fluid flows past a body is a general problem in science and engineering. Historical sphere drag and heat transfer data are critically examined. The appropriate drag coefficient is proposed to replace the inertia type definition proposed by Newton. It is found that the appropriate drag coefficient is a desirable dimensionless parameter to describe fluid flow physical behavior so that fluid flow problems can be solved in the simple and intuitive manner. The appropriate drag coefficient is presented graphically, and appears more general and reasonable to reflect the fluid flow physical behavior than the traditional century old drag coefficient diagram. Here we present drag and heat transfer experimental results which indicate that there exists a relationship in nature between the sphere drag and heat transfer. The role played by the heat flux has similar nature as the drag. The appropriate drag coefficient can be related to the Nusselt number. This finding opens new possibilities in predicting heat transfer characteristics by drag data. As heat transfer for flow over a body is inherently complex, the proposed simple means may provide an insight into the mechanism of heat transfer for flow past a body.