Science.gov

Sample records for plant pressure drop

  1. Pressure Drop

    NASA Technical Reports Server (NTRS)

    Lawson, Mike

    2010-01-01

    Mike Lawson briefly discussed pressure drop for aerospace applications and presented short stories about adventures experienced while working at NASA and General Dynamics, including exposure to technologies like the Crew and Equipment Translation Aid (CETA) cart and the SWME.

  2. Raschig ring HDS catalysts reduce pressure drop

    SciTech Connect

    Moyse, B.

    1984-12-31

    Many hydroprocessing units have a limit on their run length imposed by bed plugging. As opposed to catalyst deactivation, bed plugging can cause pressure drop over the reactor or first reactor in the train to develop rapidly. For this reason many reactor designs call for the use of scale baskets together with grading of topping material and/or catalyst in the top bed of the lead reactor. Nevertheless, many plants have a history of unfavorable pressure drop development. Some refiners must regularly practice catalyst skimming operations. In such pressure drop limiting cases the use of Raschig ring catalysts as part of the reactor fill can markedly improve the pressure drop situation.

  3. Gas Pressure-Drop Experiment

    ERIC Educational Resources Information Center

    Luyben, William L.; Tuzla, Kemal

    2010-01-01

    Most chemical engineering undergraduate laboratories have fluid mechanics experiments in which pressure drops through pipes are measured over a range of Reynolds numbers. The standard fluid is liquid water, which is essentially incompressible. Since density is constant, pressure drop does not depend on the pressure in the pipe. In addition, flow…

  4. Gas Pressure-Drop Experiment

    ERIC Educational Resources Information Center

    Luyben, William L.; Tuzla, Kemal

    2010-01-01

    Most chemical engineering undergraduate laboratories have fluid mechanics experiments in which pressure drops through pipes are measured over a range of Reynolds numbers. The standard fluid is liquid water, which is essentially incompressible. Since density is constant, pressure drop does not depend on the pressure in the pipe. In addition, flow…

  5. PS foams at high pressure drop rates

    NASA Astrophysics Data System (ADS)

    Tammaro, Daniele; De Maio, Attilio; Carbone, Maria Giovanna Pastore; Di Maio, Ernesto; Iannace, Salvatore

    2014-05-01

    In this paper, we report data on PS foamed at 100 °C after CO2 saturation at 10 MPa in a new physical foaming batch that achieves pressure drop rates up to 120 MPa/s. Results show how average cell size of the foam nicely fit a linear behavior with the pressure drop rate in a double logarithmic plot. Furthermore, foam density initially decreases with the pressure drop rate, attaining a constant value at pressure drop rates higher than 40 MPa/s. Interestingly, furthermore, we observed that the shape of the pressure release curve has a large effect on the final foam morphology, as observed in tests in which the maximum pressure release rate was kept constant but the shape of the curve changed. These results allow for a fine tuning of the foam density and morphology for specific applications.

  6. Pressure drop in two-phase flow

    NASA Astrophysics Data System (ADS)

    Akashah, S. A.

    1980-12-01

    A computer program was developed containing some of the methods for predicting pressure drop in two-phase flow. The program contains accurate methods for predicting phase behavior and physical properties and can be used to calculate pressure drops for horizontal, inclined and vertical phases. The program was used to solve test cases for many types of flow, varying the diameter, roughness, composition, overall heat transfer coefficient, angle of inclination, and length. The Lockhart-Martinelli correlation predicts the highest pressure drop while the Beggs and Brill method predicts the lowest. The American Gas Association-American Petroleum Institute method is consistent and proved to be reliable in vertical, horizontal and inclined flow. The roughness of the pipe diameter had great effect on pressure drop in two-phase flow, while the overall heat transfer coefficient had little effect.

  7. Program calculates two-phase pressure drop

    SciTech Connect

    Blackwell, W.W.

    1980-11-24

    Analysts have developed a program for determining the two-phase pressure drop in piping. Written for the TI-59 programmable calculator used with a PC-100C printer, the program incorporates several unique features: it calculates single-phase as well as two-phase pressure drops, has a 10-20 s execution time, permits the operating data to be changed easily, and includes an option for calculating the estimated surface tension of paraffinic hydrocarbon liquids.

  8. Pressure Drop in Radiator Air Tubes

    NASA Technical Reports Server (NTRS)

    Parsons, S R

    1921-01-01

    This report describes a method for measuring the drop in static pressure of air flowing through a radiator and shows (1) a reason for the discrepancy noted by various observers between head resistance and drop in pressure; (2) a difference in degree of contraction of the jet in entering a circular cell and a square cell; (3) the ratio of internal frictional resistance to total head resistance for two representative types; (4) the effect of smoothness of surface on pressure gradient; and (5) the effects of supplying heat to the radiator on pressure gradient. The fact that the pressure gradients are found to be approximately proportional to the square of the rate of flow of air appears to indicate turbulent flow, even in the short tubes of the radiator. It was found that the drop in the static pressure in the air stream through a cellular radiator and the pressure gradient in the air tubes are practically proportional to the square of the air flow in a given air density; that the difference between the head resistance per unit area and the fall of static pressure through the air tubes in radiators is apparent rather than real; and that radiators of different types differ widely in the amount of contraction of the jet at entrance. The frictional resistance was found to vary considerably, and in one case to be two-thirds of the head resistance in the type using circular cells and one-half of the head resistance of the radiator type using square cells of approximately the same dimensions.

  9. Pressure Drops Due to Silica Scaling

    SciTech Connect

    Brown, K.L.; Freeston, D.H.; Dimas, Z.O.; Slatter, A.

    1995-01-01

    Experience with reinjection returns in many geothermal fields has prompted a move towards injecting waste fluids at some distance from the production field. This means that often, reinjection pipelines cover very long distances. If the waste water in the pipelines is supersaturated with respect to amorphous silica, then the deposition of silica in these pipelines is almost certain. Although the deposit may be of negligible thickness, the inner surface characteristics of the pipe will be different to those of clean mild steel. During a silica scaling experiment. geothermal brine was passed through a series of pipes of different sizes and over a period of three weeks, silica scale formed on the inner surface. The pressure drop along a distance of approximately 5m was measured by a water manometer in all test pipe sections. Significant pressure drop was observed during this time and can be correlated with the increase in the friction factor of the pipe walls due to silica scaling.

  10. Predicting Pressure Drop In Porous Materials

    NASA Technical Reports Server (NTRS)

    Lawing, Pierce L.

    1990-01-01

    Theory developed to predict drop in pressure based on drag of individual fibers. Simple correlation method for data also developed. Helps in predicting flow characteristics of many strain-isolation pad (SIP) glow geometries in Shuttle Orbiter tile system. Also helps in predicting venting characteristics of tile assemblies during ascent and leakage of hot gas under tiles during descent. Useful in study of mechanics of flows through fibrous and porous media, and procedures applicable to purged fiberglass insulation, dialysis filters, and other fibrous and porous media.

  11. Predicting Pressure Drop In Porous Materials

    NASA Technical Reports Server (NTRS)

    Lawing, Pierce L.

    1990-01-01

    Theory developed to predict drop in pressure based on drag of individual fibers. Simple correlation method for data also developed. Helps in predicting flow characteristics of many strain-isolation pad (SIP) glow geometries in Shuttle Orbiter tile system. Also helps in predicting venting characteristics of tile assemblies during ascent and leakage of hot gas under tiles during descent. Useful in study of mechanics of flows through fibrous and porous media, and procedures applicable to purged fiberglass insulation, dialysis filters, and other fibrous and porous media.

  12. Routines for Computing Pressure Drops in Venturis

    NASA Technical Reports Server (NTRS)

    de Quay, Laurence

    2004-01-01

    A set of computer-program routines has been developed for calculating pressure drops and recoveries of flows through standard venturis, nozzle venturis, and orifices. Relative to prior methods used for such calculations, the method implemented by these routines offers greater accuracy because it involves fewer simplifying assumptions and is more generally applicable to wide ranges of flow conditions. These routines are based on conservation of momentum and energy equations for real nonideal fluids, the properties of which are calculated by curve-fitting subroutines based on empirical properties data. These routines are capable of representing cavitating, choked, non-cavitating, and unchoked flow conditions for liquids, gases, and supercritical fluids. For a computation of flow through a given venturi, nozzle venturi, or orifice, the routines determine which flow condition occurs: First, they calculate a throat pressure under the assumption that the flow is unchoked or non-cavitating, then they calculate the throat pressure under the assumption that the flow is choked or cavitating. The assumption that yields the higher throat pressure is selected as the correct one.

  13. Method for reducing pressure drop through filters, and filter exhibiting reduced pressure drop

    DOEpatents

    Sappok, Alexander; Wong, Victor

    2014-11-18

    Methods for generating and applying coatings to filters with porous material in order to reduce large pressure drop increases as material accumulates in a filter, as well as the filter exhibiting reduced and/or more uniform pressure drop. The filter can be a diesel particulate trap for removing particulate matter such as soot from the exhaust of a diesel engine. Porous material such as ash is loaded on the surface of the substrate or filter walls, such as by coating, depositing, distributing or layering the porous material along the channel walls of the filter in an amount effective for minimizing or preventing depth filtration during use of the filter. Efficient filtration at acceptable flow rates is achieved.

  14. Pressure Drop Across Finned Cylinders Enclosed in a Jacket

    NASA Technical Reports Server (NTRS)

    Rollin, Vern G; Ellerbrock, Herman H

    1937-01-01

    The pressure drop across finned cylinders in a jacket for a range of air speeds from approximately 13 to 230 miles per hour has been investigated. Tests were made to determine the effect on the pressure drop of changes in fin space, fin width, jacket entrance and exit areas, skirt-approach radius, and the use of fillets and a separator plate at the rear of the cylinder. The pressure drop across the cylinder increased as the fin space decreased, the increase being very rapid at fin spaces smaller than approximately 0.20 inch. Fin width had little effect on the pressure drop for the range of widths tested. The pressure drop across the cylinder was nearly halved by increasing the skirt-approach radius from 3/4 inch to 1-1/4 inches, but fillets and a separator plate at the rear of the cylinder had little effect on the pressure drop. The pressure drop across a cylinder with tapered fins was greater than that for a cylinder having rectangular fins with the same effective fin spacing.

  15. Effect of humidity on the filter pressure drop

    SciTech Connect

    Vendel, J.; Letourneau, P.

    1995-02-01

    The effects of humidity on the filter pressure drop have been reported in some previous studies in which it is difficult to draw definite conclusions. These studies show contradictory effects of humidity on the pressure drop probably due to differences in the hygroscopicity of the test aerosols. The objective of this paper is to present experimental results on the evolution of the filter pressure drop versus mass loading, for different test aerosols and relative humidities. Present results are compared to those found in various publication. An experimental device has been designed to measure filter pressure drop as the function of the areal density for relative humidity varying in the range of 9 % to 85 %. Experiments have been conducted with hygroscopic: (CsOH) and nonhygroscopic aerosols (TiO{sub 2}). Cesium hydroxyde (CsOH) of size of 2 {mu} M AMMD has been generated by an ultrasonic generator and the 0.7 {mu}m AMMD titanium oxyde has been dispersed by a {open_quotes}turn-table{close_quotes} generator. As it is noted in the BISWAS`publication [3], present results show, in the case of nonhygroscopic aerosols, a linear relationship of pressure drop to mass loading. For hygroscopic aerosols two cases must be considered: for relative humidity below the deliquescent point of the aerosol, the relationship of pressure drop to mass loading remains linear; above the deliquescent point, the results show a sudden increase in the pressure drop and the mass capacity of the filter is drastically reduced.

  16. Two-Phase Flow Pressure Drop of High Quality Steam

    SciTech Connect

    Curtis, J. M.; Coffield, R. D.

    2001-10-01

    Two-phase pressure drop across a straight test pipe was experimentally determined for high Reynolds (Re) number steam flow for a flow quality range of 0.995 to 1.0. The testing described has been performed in order to reduce uncertainties associated with the effects of two-phase flow on pressure drop. Two-phase flow develops in steam piping because a small fraction of the steam flow condenses due to heat loss to the surroundings. There has been very limited two-phase pressure drop data in open literature for the tested flow quality range. The two-phase pressure drop data obtained in this test has enabled development of a correlation between friction factor, Reynolds number, and flow quality.

  17. Filter aids influence on pressure drop across a filtration system

    NASA Astrophysics Data System (ADS)

    Hajar, S.; Rashid, M.; Nurnadia, A.; Ammar, M. R.; Hasfalina, C. M.

    2017-06-01

    Filter aids is commonly used to reduce pressure drop across air filtration system as it helps to increase the efficiency of filtration of accumulated filter cake. Filtration velocity is one of the main parameters that affect the performance of filter aids material. In this study, a formulated filter aids consisting of PreKot™ and activated carbon mixture (designated as PrekotAC) was tested on PTFE filter media under various filtration velocities of 5, 6, and 8 m/min at a constant material loading of 0.2 mg/mm2. Results showed that pressure drop is highly influenced by filtration velocity where higher filtration velocity leads to a higher pressure drop across the filter cake. It was found that PrekotAC performed better in terms of reducing the pressure drop across the filter cake even at the highest filtration velocity. The diversity in different particle size distribution of non-uniform particle size in the formulated PrekotAC mixture presents a higher permeability causes a lower pressure drop across the accumulated filter cake. The finding suggests that PrekotAC is a promising filter aids material that helps reducing the pressure drop across fabric filtration system.

  18. Time-resolved pulsed spray drop sizing at elevated pressures

    NASA Astrophysics Data System (ADS)

    Drallmeier, J. A.; Peters, J. E.

    1986-04-01

    An experimental program was conducted to measure drop sizes in pulsed sprays for diesel and fuel-injected spark ignition engine applications. A forward-scattering unit was designed with a high-speed data acquisition system to permit the measurement of drop sizes in sprays at 0.4-ms intervals. Data were taken at elevated pressures from 0.345 to 3.45 MPa with a 0-deg pintle nozzle. The Sauter Mean Diameter (SMD) and size distribution were calculated using a computational method that is independent of a predetermined distribution function. Results taken at the spray centerline indicate that for most elevated pressures, the SMD in the secondary injection region tended to increase as the pressure in the fuel line decreased and tended to increase with increasing environmental pressure, both suggesting an inverse relationship between drop size and the pressure drop across the nozzle. Also as the environmental pressure was raised, the distribution width decreased at a slower rate than the SMD increased, indicating a spreading of the drop sizes with injection time at elevated pressures. Significant cycle-to-cycle variation in both the SMD and distribution width indicate that cycle-to-cycle variations must be considered in pulsed sprays. In addition, more variation was seen between random rather than consecutive cycles.

  19. System for Manipulating Drops and Bubbles Using Acoustic Radiation Pressure

    NASA Technical Reports Server (NTRS)

    Oeftering, Richard C. (Inventor)

    1999-01-01

    The manipulation and control of drops of liquid and gas bubbles is achieved using high intensity acoustics in the form of and/or acoustic radiation pressure and acoustic streaming. generated by a controlled wave emission from a transducer. Acoustic radiation pressure is used to deploy or dispense drops into a liquid or a gas or bubbles into a liquid at zero or near zero velocity from the discharge end of a needle such as a syringe needle. Acoustic streaming is useful in manipulating the drop or bubble during or after deployment. Deployment and discharge is achieved by focusing the acoustic radiation pressure on the discharge end of the needle, and passing the acoustic waves through the fluid in the needle. through the needle will itself, or coaxially through the fluid medium surrounding the needle. Alternatively, the acoustic waves can be counter-deployed by focusing on the discharge end of the needle from a transducer axially aligned with the needle, but at a position opposite the needle, to prevent premature deployment of the drop or bubble. The acoustic radiation pressure can also be used for detecting the presence or absence of a drop or a bubble at the tip of a needle or for sensing various physical characteristics of the drop or bubble such as size or density.

  20. Reducing cyclone pressure drop with evasés

    USDA-ARS?s Scientific Manuscript database

    Cyclones are widely used to separate particles from gas flows and as air emissions control devices. Their cost of operation is proportional to the fan energy required to overcome their pressure drop. Evasés or exit diffusers potentially could reduce exit pressure losses without affecting collection...

  1. Microseismicity Induced by Fluid Pressure Drop (Laboratory Study)

    NASA Astrophysics Data System (ADS)

    Turuntaev, Sergey; Zenchenko, Evgeny; Melchaeva, Olga

    2013-04-01

    Pore pressure change in saturated porous rocks may result in its fracturing (Maury et Fourmaintraux, 1993) and corresponding microseismic event occurrences. Microseismicity due to fluid injection is considered in numerous papers (Maxwell, 2010, Shapiro et al., 2005). Another type of the porous medium fracturing is related with rapid pore pressure drop at some boundary. The mechanism of such fracturing was considered by (Khristianovich, 1985) as a model of sudden coal blowing and by (Alidibirov, Panov, 1998) as a model of volcano eruptions. If the porous saturated medium has a boundary where it directly contacted with fluid under the high pressure (in a hydraulic fracture or in a borehole), and the pressure at that boundary is dropped, the conditions for tensile cracks can be achieved at some distance from the boundary. In the paper, the results of experimental study of saturated porous sample fracturing due to pore pressure rapid drop are discussed. The samples (82 mm high, ∅60 mm) were made of quartz sand, which was cemented by "liquid glass" glue with mass fraction 1%. The sample (porosity 35%, uniaxial unconfined compression strength 2.5 MPa) was placed in a mould and saturated by oil. The upper end of the sample contacted with the mould upper lid, the lower end contacted with fluid. The fluid pressure was increased to 10 MPa and then discharged through the bottom nipple. The pressure increases/drops were repeated 30-50 times. Pore pressure and acoustic emission (AE) were registered by transducers mounted into upper and bottom lids of the mould. It was found, that AE sources (corresponded to microfracturing) were spreading from the open end to the closed end of the sample, and that maximal number of AE events was registered at some distance from the opened end. The number of AE pulses increased with every next pressure drop, meanwhile the number of pulses with high amplitudes diminished. It was found that AE maximal rate corresponded to the fluid pressure

  2. He II heat transfer through random packed spheres: Pressure drop

    NASA Astrophysics Data System (ADS)

    Vanderlaan, M. H.; Van Sciver, S. W.

    2014-09-01

    Heat flow induced pressure drop through superfluid helium (He II) contained in porous media is examined. In this experiment, heat was applied to one side of a He II column containing a random pack of uniform size polyethylene spheres. Measured results include steady state pressure drops across the random packs of spheres (nominally 35 μm, 49 μm, and 98 μm diameter) for different heat inputs. Laminar, turbulent, and transition fluid flow regimes are examined. The laminar permeability and equivalent channel shape factor are compared to our past studies of the temperature drop through He II in the same porous media of packed spheres. Results from the pressure drop experiments are more accurate than temperature drop experiments due to reduced measurement errors achieved with the pressure transducer. Turbulent results are fitted to models with empirically derived friction factors. A turbulent model considering only dynamic pressure losses in the normal fluid yields the most consistent friction factors. The addition of the laminar and turbulent heat flow equations into a unifying prediction fits all regimes to within 10%.

  3. Controlling Vapor Pressure In Hanging-Drop Crystallization

    NASA Technical Reports Server (NTRS)

    Carter, Daniel C.; Smith, Robbie

    1988-01-01

    Rate of evaporation adjusted to produce larger crystals. Device helps to control vapor pressure of water and other solvents in vicinity of hanging drop of solution containing dissolved enzyme protein. Well of porous frit (sintered glass) holds solution in proximity to drop of solution containing protein or enzyme. Vapor from solution in frit controls evaporation of solvent from drop to control precipitation of protein or enzyme. With device, rate of nucleation limited to decrease number and increase size (and perhaps quality) of crystals - large crystals of higher quality needed for x-ray diffraction studies of macromolecules.

  4. MHD pressure drop in ducts with imperfectly insulating coatings

    SciTech Connect

    Malang, S.; Buehler, L.

    1994-08-01

    Liquid metal cooled blankets in fusion tokamak`s are feasible only with electrically insulating coatings at the coolant channel walls. The requirements of such coatings are investigated and a simple analytical model is developed to determine the influence of imperfections in the coatings on the magneto-hydrodynamic pressure drop. This model is compared with the results of a 3D-MHD code based on the core flow approach. Both methods are in good agreement as long as the imperfections do not increase the pressure drop by more than 20%. The analytical model over-estimates the pressure drop for values larger than 20%. The importance of self-healing of coatings in case of cracking or flaking is quantified and an equation for the equilibrium conditions between the generation of imperfection and the healing of such spots is provided.

  5. Experimental Investigation of Oscillatory Flow Pressure and Pressure Drop Through Complex Geometries

    NASA Technical Reports Server (NTRS)

    Ibrahim, Mounir B.; Wang, Meng; Gedeon, David

    2005-01-01

    A series of experiments have been performed to investigate the oscillatory flow pressure and pressure drop through complex geometries. These experiments were conducted at the CSU-SLRE facility which is a horizontally opposed, two-piston, single-acting engine with a split crankshaft driving mechanism. Flow through a rectangular duct, with no insert (obstruction), was studied first. Then four different inserts were examined: Abrupt, Manifold, Diverging Short and Diverging Long. The inserts were mounted in the center of the rectangular duct to represent different type of geometries that could be encountered in Stirling machines. The pressure and pressure drop of the oscillating flow was studied for: 1) different inserts, 2) different phase angle between the two pistons of the engine (zero, 90 lead, 180, and 90 lag), and 3) for different piston frequencies (5, 10, 15, and 20 Hz). It was found that the pressure drop of the oscillatory flow increases with increasing Reynolds number. The pressure drop was shown to be mainly due to the gas inertia for the case of oscillatory flow through a rectangular duct with no insert. On the other hand, for the cases with different inserts into the rectangular duct, the pressure drop has three sources: inertia, friction, and local losses. The friction pressure drop is only a small fraction of the total pressure drop. It was also shown that the dimensionless pressure drop decreases with increasing kinetic Reynolds number.

  6. Development and verification of two-phase pressure drop correlations for RBMK-type reactors

    NASA Astrophysics Data System (ADS)

    Zvinys, Evaldas

    The available two-phase frictional pressure drop correlations are reviewed and compared, extending their applicability range to include the thermal-hydraulic conditions prevailing in RBMK reactor fuel channels. It is shown that the Heat Transfer and Fluid Flow Service (HTFS) pressure drop correlation used in RELAP5 MOD 3.2.1.2 code has shortcomings. From the list of alternative correlations the Osmachkin and Friedel correlations are selected. The behavior of the above two correlations is explained and the shortcomings of the Osmachkin correlation are noted. In order to improve the Osmachkin correlation, a new concept of the free flow fraction is introduced. It is shown that using the free flow fraction one can predict the quality at which the homogeneous equilibrium model case pressure drop is approached. A computational algorithm for two-phase pressure drop multiplier is developed using the transition criteria based on the free flow fraction and also on the Friedel and Osmachkin two-phase pressure drop relations. This algorithm is implemented into the RELAP5 code. The performance of the updated code version is verified using the Ignalina Nuclear Power Plant data base of operation parameters. The comparison reveals that the "updated" code version shows a better agreement with data. The performance of the updated and standard code versions is also investigated by modeling a group distribution header guillotine rupture in the Ignalina Nuclear Power Plant. Although the calculated results show differences, the deviation between the two code versions is within the engineering uncertainty range.

  7. Determination of pressure drop across activated carbon fiber respirator cartridges.

    PubMed

    Balanay, Jo Anne G; Lungu, Claudiu T

    2016-01-01

    Activated carbon fiber (ACF) is considered as an alternative adsorbent to granular activated carbon (GAC) for the development of thinner, lighter, and efficient respirators because of their larger surface area and adsorption capacities, thinner critical bed depth, lighter weight, and fabric form. This study aims to measure the pressure drop across different types of commercially available ACFs in respirator cartridges to determine the ACF composition and density that will result in acceptably breathable respirators. Seven ACF types in cloth (ACFC) and felt (ACFF) forms were tested. ACFs in cartridges were challenged with pre-conditioned constant air flow (43 LPM, 23°C, 50% RH) at different compositions (single- or combination-ACF type) in a test chamber. Pressure drop across ACF cartridges were obtained using a micromanometer, and compared among different cartridge configurations, to those of the GAC cartridge, and to the NIOSH breathing resistance requirements for respirator cartridges. Single-ACF type cartridges filled with any ACFF had pressure drop measurements (23.71-39.93 mmH2O) within the NIOSH inhalation resistance requirement of 40 mmH2O, while those of the ACFC cartridges (85.47±3.67 mmH2O) exceeded twice the limit due possibly to the denser weaving of ACFC fibers. All single ACFF-type cartridges had higher pressure drop compared to the GAC cartridge (23.13±1.14 mmH2O). Certain ACF combinations (2 ACFF or ACFC/ACFF types) resulted to pressure drop (26.39-32.81 mmH2O) below the NIOSH limit. All single-ACFF type and all combination-ACF type cartridges with acceptable pressure drop had much lower adsorbent weights than GAC (≤15.2% of GAC weight), showing potential for light-weight respirator cartridges. 100% ACFC in cartridges may result to respirators with high breathing resistance and, thus, is not recommended. The more dense ACFF and ACFC types may still be possibly used in respirators by combining them with less dense ACFF materials and/or by

  8. Frictional pressure drop in horizontal pneumatic conveying of coal and limestone

    SciTech Connect

    Daw, C.S.; Thomas, J.F.

    1983-08-01

    Pneumatic conveying experiments were conducted at Oak Ridge National Laboratory (ORNL) with crushed coal, limestone, and coal-limestone mixtures on a conveying system designed to represent the branch feed lines in the TVA 20-MW(e) atmospheric fluidized bed combustor. Test conditions were chosen to cover the anticipated operating ranges of the pilot plant. Details of the experimental apparatus and a summary of the results are presented in ORNL/TM-7724. This report is a further analysis of the horizontal pressure-drop data produced by the ORNL experiments. The results are compared with previous data and correlations in the literature, and the combined data provide strong evidence that there at least two possible pressure-drop modes in horizontal, dilute-phase conveying. The ORNL results follow a high-pressure-drop mode, while a major portion of data in the literature follow a low-pressure-drop mode. The results of Mehta (1955) and Peskin (1963) confirm the existence of the high-pressure-drop mode. It is proposed that the two pressure-drop modes result from inertia-dominated and viscous-dominated flow. With an inertial model, it is possible to derive an expression for the horizontal pressure drop that agrees remarkably well with the ORNL data, the larger-particle data of Mehta (1955), and the data of Peskin (1963). The small particle data of Mehta and the bulk of the data in the literature appear to follow the viscous flow model developed by Julian and Dukler (1965). It also appears that some data in the literature may represent combinations of the two flow regimes or transitions between them. 29 references, 15 figures, 2 tables.

  9. Heat Transfer and Pressure Drop in Concentric Annular Flows of Binary Inert Gas Mixtures

    NASA Technical Reports Server (NTRS)

    Reid, R. S.; Martin, J. J.; Yocum, D. J.; Stewart, E. T.

    2007-01-01

    Studies of heat transfer and pressure drop of binary inert gas mixtures flowing through smooth concentric circular annuli, tubes with fully developed velocity profiles, and constant heating rate are described. There is a general lack of agreement among the constant property heat transfer correlations for such mixtures. No inert gas mixture data exist for annular channels. The intent of this study was to develop highly accurate and benchmarked pressure drop and heat transfer correlations that can be used to size heat exchangers and cores for direct gas Brayton nuclear power plants. The inside surface of the annular channel is heated while the outer surface of the channel is insulated. Annulus ratios range 0.5 < r* < 0.83. These smooth tube data may serve as a reference to the heat transfer and pressure drop performance in annuli, tubes, and channels having helixes or spacer ribs, or other surfaces.

  10. Prediction of Pressure Drop in the ITER Divertor Cooling Channels

    SciTech Connect

    Yin, S.T.; Chen, J.L.

    2005-04-15

    This study investigated the pressure drop in the divertor cooling channels of the International Thermonuclear Experimental Reactor (ITER). The water in the cooling channels will encounter the following flow and boiling regimes: 1) single-phase convection, 2) highly-subcooled boiling, 3) onset of nucleate boiling (ONB), and 4) fully-developed subcooled boiling. The upper operating boundary is limited by the departure from nucleate boiling (DNB) or burnout conditions. Twisted-tape insert will be used to enhance local heat transfer. Analytical models, validated with relevant databases, were proposed for the above-identified flow regimes. A user-friendly computer code was developed to calculate the overall pressure drop and the exit pressure of a specific local segment throughout the entire flow circuit. Although the operating parameters were based on the CDA phase input the results are found in general agreement when compared with the ITER EDA results.

  11. Experimental study on pressure drop of bends in dense phase pneumatic conveying under high pressure

    NASA Astrophysics Data System (ADS)

    Yuan, Gaoyang; Liang, Cai; Chen, Xiaoping; Xu, Pan; Xu, Guiling; Shen, Liu

    2014-04-01

    The transport test using nitrogen as conveying gas are carried out at high operating pressure up to 4MPa in the experimental equipment for dense phase pneumatic conveying. The transport powders in the experiment are anthracite coal and petroleum coke. The pressure drop characteristics in bends are acquired with the different transport powder. The experimental results show that under the similar mass flow, the pressure drop of vertical upward bend is greater than the horizontal bend and the horizontal bend is greater than the vertical downward bend at the same superficial gas velocity, while there is a best superficial gas velocity minimizes the pressure drop of the bend. Under the similar mass flow rate and the similar particle size, the pressure drop of the bend with the petroleum coke is greater than the pressure drop with the anthracite coal as the same superficial gas velocity. According to Barth's additional pressure drop method, the pressure drop fitting formulas of the vertical upward bend, the horizontal bend and the vertical downward bend are obtained, and the predicted results are in accordance with that of the experiments.

  12. Description of an oscillating flow pressure drop test rig

    NASA Technical Reports Server (NTRS)

    Wood, J. Gary; Miller, Eric L.; Gedeon, David R.; Koester, Gary E.

    1988-01-01

    A test rig designed to generate heat exchanger pressure drop information under oscillating flow conditions is described. This oscillating flow rig is based on a variable stroke and variable frequency linear drive motor. A frequency capability of 120 hertz and a mean test pressure up to 15 mPA (2200 psi) allows for testing at flow conditions found in modern high specific power Stirling engines. An important design feature of this rig is that it utilizes a single close coupled dynamic pressure transducer to measure the pressure drop across the test sample. This eliminates instrumentation difficulties associated with the pressure sensing lines common to differential pressure transducers. Another feature of the rig is that it utilizes a single displacement piston. This allows for testing of different sample lengths and configurations without hardware modifications. All data acquisition and reduction for the rig is performed with a dedicated personal computer. Thus the overall system design efficiently integrates the testing and data reduction procedures. The design methodology and details of the test rig is described.

  13. Pressure drop and He II flow through fine mesh screens

    NASA Technical Reports Server (NTRS)

    Maddocks, J. R.; Van Sciver, S. W.

    1989-01-01

    Fluid acquisition systems for He II transfer devices will utilize gallery arms to ensure that the fluid encounters the pump inlet. In near term experiments such as Superfluid Helium on Orbit Transfer (SHOOT), the preferred configuration consists of several rectangular channels which have one side made from a Dutch weave stainless steel screen having 325 x 2300 wires per inch. The effective pore diameter for this screen is about 5 microns. The present paper reports on measurements of pressure drop across a screen when it is subjected to a flow of liquid helium. The experiment measures the time rate of change of the level in two different helium reservoirs connected by a screen-blocked channel. Results with normal helium are compared with predictions based on the Armour-Cannon (1968) equations. The He II data show considerable deviation from the classical result. A discussion of the He II pressure drop results in terms of two fluid hydrodynamics is included.

  14. Pressure drop and He II flow through fine mesh screens

    NASA Technical Reports Server (NTRS)

    Maddocks, J. R.; Van Sciver, S. W.

    1989-01-01

    Fluid acquisition systems for He II transfer devices will utilize gallery arms to ensure that the fluid encounters the pump inlet. In near term experiments such as Superfluid Helium on Orbit Transfer (SHOOT), the preferred configuration consists of several rectangular channels which have one side made from a Dutch weave stainless steel screen having 325 x 2300 wires per inch. The effective pore diameter for this screen is about 5 microns. The present paper reports on measurements of pressure drop across a screen when it is subjected to a flow of liquid helium. The experiment measures the time rate of change of the level in two different helium reservoirs connected by a screen-blocked channel. Results with normal helium are compared with predictions based on the Armour-Cannon (1968) equations. The He II data show considerable deviation from the classical result. A discussion of the He II pressure drop results in terms of two fluid hydrodynamics is included.

  15. Validation of an All-Pressure Fluid Drop Model: Heptane Fluid Drops in Nitrogen

    NASA Technical Reports Server (NTRS)

    Harstad, K.; Bellan, J.; Bulzan, Daniel L. (Technical Monitor)

    2000-01-01

    Despite the fact that supercritical fluids occur both in nature and in industrial situations, the fundamentals of their behavior is poorly understood because supercritical fluids combine the characteristics of both liquids and gases, and therefore their behavior is not intuitive. There are several specific reasons for the lack of understanding: First, data from (mostly optical) measurements can be very misleading because regions of high density thus observed are frequently identified with liquids. A common misconception is that if in an experiment one can optically identify "drops" and "ligaments", the observed fluid must be in a liquid state. This inference is incorrect because in fact optical measurements detect any large change (i.e. gradients) in density. Thus, the density ratio may be well below Omicron(10(exp 3)) that characterizes its liquid/gas value, but the measurement will still identify a change in the index of refraction providing that the change is sudden (steep gradients). As shown by simulations of supercritical fluids, under certain conditions the density gradients may remain large during the supercritical binary fluids mixing, thus making them optically identifiable. Therefore, there is no inconsistency between the optical observation of high density regions and the fluids being in a supercritical state. A second misconception is that because a fluid has a liquid-like density, it is appropriate to model it as a liquid. However, such fluids may have liquid-like densities while their transport properties differ from those of a liquid. Considering that the critical pressure of most fuel hydrocarbons used in Diesel and gas turbine engines is in the range of 1.5 - 3 MPa, and the fact that the maximum pressure attained in these engines is about 6 Mps, it is clear that the fuel in the combustion chamber will experience both subcritical and supercritical conditions. Studies of drop behavior over a wide range of pressures were performed in the past

  16. The pressure drop in a porous material layer during combustion

    SciTech Connect

    Kondrikov, B.N.

    1995-07-01

    During the combustion of a porous material layer, a manometer, which is attached to the cold end of the charge, records at the bottom of the layer a pressure reduction, which was discovered more than 20 years ago but which remains essentially unexplained up to the present. It is experimentally shown that this effect is similar to the pressure change in the cavities when a light gas (helium, hydrogen) diffuses from (or to) them under isothermal conditions and that it increases during the combustion mainly due to the accompanying Stefan type flow, and probably also as a result of the thermal diffusion. A pressure drop in the cavities is evidently made possible also by the pressure reduction in the flame which follows from the Hugoniot adiabatic theory.

  17. Limiting the Accidental Pressure Drop in NIF Beam Tubes

    SciTech Connect

    Garcia, M

    2000-11-06

    This report summarizes the use of a one-dimensional model of a time-dependent compressible flow condition to validate the results from a more sophisticated three-dimensional model. The flow conditions consist of the sudden decompression of a pressurized tube joined to an evacuated sphere, where the tube also has a leak to external atmosphere that is triggered open at a given pressure difference below sea-level pressure. This flow model is used to calculate conditions in a NIF beam tube if an internal vacuum barrier fails, and to calculate how the size and timing of an opening to external atmosphere changes tube pressure. Decompression of a NIF beam tube is a potential safety hazard since the tube could collapse if the tube pressure is reduced below the buckling limit. To prevent this from occurring, each pressurized section includes a rupture panel which is designed to open to external atmosphere at a given pressure difference. The inrush of external atmosphere through the rupture panel fills both the tube and the vacuum drawing on it, and in this way the pressure drop in the tube is quickly limited and reversed. In summary, the results from the 1D model indicate that the 3-D calculations are accurate and reasonable.

  18. Pressure drop in a borehole intersecting an active fault

    NASA Astrophysics Data System (ADS)

    Doan, M.; Cornet, F. H.

    2004-12-01

    The Corinth Rift, in western Greece, is one of the most active continental Rift in the world, with an opening rate of 1.5cm/yr. Its deformation process is being monitored with a broad range of sensors dispatched across the rift, near the city of Aigio, some 40km east of Patras. In particular, a set of pressure transducers has been set in a 1000m-deep borehole that intersects the active 10km long Aigio fault at a depth of 760m. Below its upper 700m deep cased section, the well has been left open and intersects two artesian aquifers. The upper aquifer is fully hydraulically decoupled from surface aquifers and is developed in tectonized platy limestone, with a 0.5MPa original pressure. Below the fault, the limestone is heavily karstified and the artesian overpressure reaches about 0.85MPa. Hence the fault supports a 0.35MPa differential pressure through the 5m thick radiolarite clay layer that has been smeared along the 150m fault offset. In September 2003, the borehole was let produce water and then was plugged with a packer set at the top of the casing resulting in a direct connection between both aquifers. The pressure is monitored by sensors set just below the packer. Tidal waves are recorded with a resolution better than 1/100. In addition a variety of pressure anomalies have been observed. A 60Pa drop in pore pressure has been recorded at the onset of the S waves generated by the Mw=7.8 Rat Island Earthquake of November, 17th 2003. It is followed by a slow recovery which lasted about 30 minutes. This anomaly, compatible with a minor movement along the fault with a seismic moment of 109Nm, is one of the farthest local effects induced by teleseismic waves ever recorded. A 80Pa pressure drop has been detected 15 minutes before a ML=4.2 earthquake that occured about 15km west of the well. It is much sharper than the coseismic drop. This precursory event exhibits a 2-step recovery that lasted 10 minutes. As seismic sensors located near the well detected no major

  19. Metamorphic record of catastrophic pressure drops in subduction zones

    NASA Astrophysics Data System (ADS)

    Yamato, P.; Brun, J. P.

    2017-01-01

    When deeply buried in subduction zones, rocks undergo mineral transformations that record the increase of pressure and temperature. The fact that high-pressure metamorphic parageneses are found at the Earth’s surface proves that rock burial is followed by exhumation. Here we use analysis of available data sets from high-pressure metamorphic rocks worldwide to show that the peak pressure is proportional to the subsequent decompression occurring during the initial stage of retrogression. We propose, using a simple mechanical analysis, that this linear relationship can be explained by the transition from burial-related compression to extension at the onset of exhumation. This major switch in orientation and magnitude of principal tectonic stresses leads to a catastrophic pressure drop prior to actual rock ascent. Therefore, peak pressures are not necessarily, as commonly believed, directly dependent on the maximum burial depth, but can also reflect a change of tectonic regime. Our results, which are in agreement with natural data, have significant implications for rock rheology, subduction zone seismicity, and the magnitudes of tectonic pressures sustained by rocks. Current views of subduction dynamics could be reconsidered in that perspective.

  20. Intercooler cooling-air weight flow and pressure drop for minimum drag loss

    NASA Technical Reports Server (NTRS)

    Reuter, J George; Valerino, Michael F

    1944-01-01

    An analysis has been made of the drag losses in airplane flight of cross-flow plate and tubular intercoolers to determine the cooling-air weight flow and pressure drop that give a minimum drag loss for any given cooling effectiveness and, thus, a maximum power-plant net gain due to charge-air cooling. The drag losses considered in this analysis are those due to (1) the extra drag imposed on the airplane by the weight of the intercooler, its duct, and its supports and (2) the drag sustained by the cooling air in flowing through the intercooler and its duct. The investigation covers a range of conditions of altitude, airspeed, lift-drag ratio, supercharger-pressure ratio, and supercharger adiabatic efficiency. The optimum values of cooling air pressure drop and weight flow ratio are tabulated. Curves are presented to illustrate the results of the analysis.

  1. Air Flow and Pressure Drop Measurements Across Porous Oxides

    NASA Technical Reports Server (NTRS)

    Fox, Dennis S.; Cuy, Michael D.; Werner, Roger A.

    2008-01-01

    This report summarizes the results of air flow tests across eight porous, open cell ceramic oxide samples. During ceramic specimen processing, the porosity was formed using the sacrificial template technique, with two different sizes of polystyrene beads used for the template. The samples were initially supplied with thicknesses ranging from 0.14 to 0.20 in. (0.35 to 0.50 cm) and nonuniform backside morphology (some areas dense, some porous). Samples were therefore ground to a thickness of 0.12 to 0.14 in. (0.30 to 0.35 cm) using dry 120 grit SiC paper. Pressure drop versus air flow is reported. Comparisons of samples with thickness variations are made, as are pressure drop estimates. As the density of the ceramic material increases the maximum corrected flow decreases rapidly. Future sample sets should be supplied with samples of similar thickness and having uniform surface morphology. This would allow a more consistent determination of air flow versus processing parameters and the resulting porosity size and distribution.

  2. Numerical Analysis including Pressure Drop in Oscillating Water Column Device

    NASA Astrophysics Data System (ADS)

    das Neves Gomes, Mateus; Domingues dos Santos, Elizaldo; Isoldi, Liércio André; Rocha, Luiz Alberto Oliveira

    2015-06-01

    The wave energy conversion into electricity has been increasingly studied in the last years. There are several proposed converters. Among them, the oscillatingwater column (OWC) device has been widespread evaluated in literature. In this context, the main goal of this work was to perform a comparison between two kinds of physical constraints in the chimney of the OWC device, aiming to represent numerically the pressure drop imposed by the turbine on the air flow inside the OWC. To do so, the conservation equations of mass,momentumand one equation for the transport of volumetric fraction were solved with the finite volume method (FVM). To tackle thewater-air interaction, the multiphase model volume of fluid (VOF)was used. Initially, an asymmetric constraint inserted in chimney duct was reproduced and investigated. Subsequently, a second strategywas proposed,where a symmetric physical constraint with an elliptical shapewas analyzed. Itwas thus possible to establish a strategy to reproduce the pressure drop in OWC devices caused by the presence of the turbine, as well as to generate its characteristic curve.

  3. Axisymmetric drop shape analysis-constrained sessile drop (ADSA-CSD): a film balance technique for high collapse pressures.

    PubMed

    Saad, Sameh M I; Policova, Zdenka; Acosta, Edgar J; Neumann, A Wilhelm

    2008-10-07

    Collapse pressure of insoluble monolayers is a property determined from surface pressure/area isotherms. Such isotherms are commonly measured by a Langmuir film balance or a drop shape technique using a pendant drop constellation (ADSA-PD). Here, a different embodiment of a drop shape analysis, called axisymmetric drop shape analysis-constrained sessile drop (ADSA-CSD) is used as a film balance. It is shown that ADSA-CSD has certain advantages over conventional methods. The ability to measure very low surface tension values (e.g., <2 mJ/m2), an easier deposition procedure than in a pendant drop setup, and leak-proof design make the constrained sessile drop constellation a better choice than the pendant drop constellation in many situations. Results of compression isotherms are obtained on three different monolayers: octadecanol, dipalmitoyl-phosphatidyl-choline (DPPC), and dipalmitoyl-phosphatidyl-glycerol (DPPG). The collapse pressures are found to be reproducible and in agreement with previous methods. For example, the collapse pressure of DPPC is found to be 70.2 mJ/m2. Such values are not achievable with a pendant drop. The collapse pressure of octadecanol is found to be 61.3 mJ/m2, while that of DPPG is 59.0 mJ/m2. The physical reasons for these differences are discussed. The results also show a distinctive difference between the onset of collapse and the ultimate collapse pressure (ultimate strength) of these films. ADSA-CSD allows detailed study of this collapse region.

  4. Pressure drop of He II flow through a porous media

    NASA Technical Reports Server (NTRS)

    Maddocks, J. R.; Van Sciver, S. W.

    1990-01-01

    The paper reports on measurements of He II pressure drop across two porous SiO2 ceramic filter materials. These materials vary only in porosity, having values of 0.94 and 0.96. The average fiber diameter in both cases is approximately 5 microns. The experiment consists of a glass tube containing a piece of this sponge in one end. The tube is rapidly displaced downward in a bath of helium and the liquid levels are allowed to equilibrate over time producing variable velocities up to 10 cm/sec. The results are compared with those previously obtained using fine mesh screens. Good qualitative agreement is observed for turbulent flow; however, the behavior in the laminar flow regime is not fully understood.

  5. Pressure drop of He II flow through a porous media

    NASA Technical Reports Server (NTRS)

    Maddocks, J. R.; Van Sciver, S. W.

    1990-01-01

    The paper reports on measurements of He II pressure drop across two porous SiO2 ceramic filter materials. These materials vary only in porosity, having values of 0.94 and 0.96. The average fiber diameter in both cases is approximately 5 microns. The experiment consists of a glass tube containing a piece of this sponge in one end. The tube is rapidly displaced downward in a bath of helium and the liquid levels are allowed to equilibrate over time producing variable velocities up to 10 cm/sec. The results are compared with those previously obtained using fine mesh screens. Good qualitative agreement is observed for turbulent flow; however, the behavior in the laminar flow regime is not fully understood.

  6. Method - Pressure drop tests for fuel system components

    NASA Astrophysics Data System (ADS)

    1990-12-01

    Techniques are presented for testing components and improving the accuracy of such tests to meet the requirements of MIL-F-8615 or equivalent specifications. Pressure-drop tests for individual components are described generally including the single and double piezometer-tube methods, and many of the suggested improvements apply to these techniques. The test setup is presented graphically, and the procedural conditions are described. The suggestions for improving the test results include notes regarding air bubbles, pumping-source pulsations, attachment fittings, overshooting the flow rate, and the importance of precise calibration. Diagrams are given for the double piezometer-tube, the mercury-manometer, and the fuel-manometer tests, and the arithmetic computation is described for the data-reduction equation.

  7. A pressurized drop-tube furnace for coal reactivity studies

    NASA Astrophysics Data System (ADS)

    Ouyang, Shan; Yeasmin, Hasina; Mathews, Joseph

    1998-08-01

    The design and characterization of a pressurized drop-tube furnace for investigation of coal devolatilization, gasification, and combustion are presented. The furnace is designed for high-temperature, isothermal operation in a developing laminar flow regime. It can be operated at pressures up to 1600 kPa, and temperatures up to 1673 K, with variable reaction time, particle feeding rate, and with inert and various oxidizing atmospheres. Particle residence times can be varied between ˜0.02 and ˜10 s depending upon operating conditions and positions of injection and sampling probes. Observations ports are available for sample collections and for optical investigation of the reactions or temperature measurements. Characterization of gas temperature in the furnace shows that, although the gas temperature profile in the furnace is affected by the water-cooled injection probe, the furnace is able to achieve isothermal operation in a developing laminar flow regime. Results from a series of brown coal devolatilization tests demonstrated the suitability of the furnace for experiments in coal research.

  8. Two-phase pressure drop of ammonia in small diameter horizontal tubes

    NASA Technical Reports Server (NTRS)

    Ungar, Eugene K.; Cornwell, John D.

    1992-01-01

    Data for pressure drop in adiabatic two-phase ammonia flows in small diameter horizontal tubes are presented. The data has direct application to the sizing of the flow-through radiator tubes in the Space Station Freedom heat rejection system. The data are compared to existing correlations for pressure drop and are found to be significantly lower than the most commonly used correlations. However, several of the less commonly used correlations predict the data accurately. Alternate pressure drop prediction methods are explored and a recommendation is made for a method to accurately predict the pressure drop in two-phase ammonia flows in small horizontal tubes.

  9. Pressure drop and thrust predictions for transonic micronozzle flows

    NASA Astrophysics Data System (ADS)

    Gomez, J.; Groll, R.

    2016-02-01

    In this paper, the expansion of xenon, argon, krypton, and neon gases through a Laval nozzle is studied experimentally and numerically. The pressurized gases are accelerated through the nozzle into a vacuum chamber in an attempt to simulate the operating conditions of a cold-gas thruster for attitude control of a micro-satellite. The gases are evaluated at several mass flow rates ranging between 0.178 mg/s and 3.568 mg/s. The Re numbers are low (8-256) and the estimated values of Kn number lie between 0.33 and 0.02 (transition and slip-flow regime). Direct Simulation Monte Carlo (DSMC) and continuum-based simulations with a no-slip boundary condition are performed. The DSMC and the experimental results show good agreement in the range Kn > 0.1, while the Navier-Stokes results describe the experimental data more accurately for Kn < 0.05. Comparison between the experimental and Navier-Stokes results shows high deviations at the lower mass flow rates and higher Kn numbers. A relation describing the deviation of the pressure drop through the nozzle as a function of Kn is obtained. For gases with small collision cross sections, the experimental pressure results deviate more strongly from the no-slip assumption. From the analysis of the developed function, it is possible to correct the pressure results for the studied gases, both in the slip-flow and transition regimes, with four gas-independent accommodation coefficients. The thrust delivered by the cold-gas thruster and the specific impulse is determined based on the numerical results. Furthermore, an increase of the thickness of the viscous boundary layer through the diffuser of the micronozzle is observed. This results in a shock-less decrease of the Mach number and the flow velocity, which penalizes thrust efficiency. The negative effect of the viscous boundary layer on thrust efficiency can be lowered through higher values of Re and a reduction of the diffuser length.

  10. Resonances, radiation pressure and optical scattering phenomena of drops and bubbles

    NASA Technical Reports Server (NTRS)

    Marston, P. L.; Goosby, S. G.; Langley, D. S.; Loporto-Arione, S. E.

    1982-01-01

    Acoustic levitation and the response of fluid spheres to spherical harmonic projections of the radiation pressure are described. Simplified discussions of the projections are given. A relationship between the tangential radiation stress and the Konstantinov effect is introduced and fundamental streaming patterns for drops are predicted. Experiments on the forced shape oscillation of drops are described and photographs of drop fission are displayed. Photographs of critical angle and glory scattering by bubbles and rainbow scattering by drops are displayed.

  11. The effect of pressure on annular flow pressure drop in a small pipe

    SciTech Connect

    de Bertodano, M.A.L.; Beus, S.G.; Shi, Jian-Feng

    1996-09-01

    New experimental data was obtained for pressure drop and entrainment for annular up-flow in a vertical pipe. The 9.5 mm. pipe has an L/D ratio of 440 to insure fully developed annular flow. The pressure ranged from 140 kPa to 660 kPa. Therefore the density ratio was varied by a factor of four approximately. This allows the investigation of the effect of pressure on the interfacial shear models. Gas superficial velocities between 25 and 126 m/s were tested. This extends the range of previous data to higher gas velocities. The data were compared with well known models for interfacial shear that represent the state of the art. Good results were obtained when the model by Asali, Hanratty and Andreussi was modified for the effect of pressure. Furthermore an equivalent model was obtained based on the mixing length theory for rough pipes. It correlates the equivalent roughness to the film thickness.

  12. Oscillatory pressure drops through a woven-screen packed column subjected to a cyclic flow

    NASA Astrophysics Data System (ADS)

    Zhao, T. S.; Cheng, P.

    An experiment has been performed to investigate oscillatory pressure drop characteristics in packed columns (composed of three different sizes of woven screen) subjected to a periodically reversing flow of air. It was found that the oscillatory pressure drop factor increases with the kinetic Reynolds number (Re ω) Dh and with the dimensionless fluid displacement ( Ao) Dh. Based on 92 experimental runs, correlation equations for the maximum and the cycle-averaged pressure drop factors in terms of these two similarity parameters are obtained. It is found that the value of the cycle-averaged pressure drop of the oscillatory flow in a packed column is four to six times higher than that of a steady flow at the same Reynolds number based on the cross-sectional mean velocity. At small Reynolds numbers, this pressure drop ratio depends only on the geometry of the woven screens and is independent of the Reynolds number (Re gw) Dh and the dimensionless fluid displacement ( Ao) DDh.

  13. Low pressure drop airborne molecular contaminant filtration using open-channel networks

    NASA Astrophysics Data System (ADS)

    Dallas, Andrew J.; Ding, Lefei; Joriman, Jon; Zastera, Dustin; Seguin, Kevin; Empson, James

    2006-03-01

    Airborne molecular contamination (AMC) continues to play a very decisive role in the performance of many microelectronic devices and manufacturing processes. Currently, the state of the filtration industry is such that optimum filter life and removal efficiency for AMC is offered by granular filter beds. However, the attributes that make packed beds of adsorbents extremely efficient also impart issues related to elevated filter weight and pressure drop. Most of the low pressure drop AMC filters currently offered tend to be quiet costly and contaminant nonspecific. Many of these low pressure drop filters are simply pleated combinations of various adsorptive and reactive media. On the other hand, low pressure drop filters, such as those designed as open-channel networks (OCNs), can still offer good filter life and removal efficiency, with the additional benefits of significant reductions in overall filter weight and pressure drop. Equally important for many applications, the OCN filters can reconstruct the airflow so as to enhance the operation of a tool or process. For tool mount assemblies and full fan unit filters this can result in reduced fan and blower speeds, which subsequently can provide reduced vibration and energy costs. Additionally, these low pressure drop designs can provide a cost effective way of effectively removing AMC in full fab (or HVAC) filtration applications without significantly affecting air-handling requirements. Herein, we will present a new generation of low pressure drop OCN filters designed for AMC removal in a wide range of applications.

  14. Effect of External Pressure Drop on Loop Heat Pipe Operating Temperature

    NASA Technical Reports Server (NTRS)

    Jentung, Ku; Ottenstein, Laura; Rogers, Paul; Cheung, Kwok; Obenschain, Arthur F. (Technical Monitor)

    2002-01-01

    This paper discusses the effect of the pressure drop on the operating temperature in a loop heat pipe (LHP). Because the evaporator and the compensation chamber (CC) both contain two-phase fluid, a thermodynamic constraint exists between the temperature difference and the pressure drop for these two components. As the pressure drop increases, so will the temperature difference. The temperature difference in turn causes an increase of the heat leak from the evaporator to the CC, resulting in a higher CC temperature. Furthermore, the heat leak strongly depends on the vapor void fraction inside the evaporator core. Tests were conducted by installing a valve on the vapor line so as to vary the pressure drop, and by charging the LHP with various amounts of fluid. Test results verify that the LHP operating temperature increases with an increasing differential pressure, and the temperature increase is a strong function of the fluid inventory in the loop.

  15. Compressibility Effects on Heat Transfer and Pressure Drop in Smooth Cylindrical Tubes

    NASA Technical Reports Server (NTRS)

    Nielsen, Jack N

    1944-01-01

    An analysis is made to simplify pressure-drop calculations for nonadiabatic and adiabatic friction flow of air in smooth cylindrical tubes when the density changes due to heat transfer and pressure drop are appreciable. Solutions of the equation of motion are obtained by the use of Reynolds' analogy between heat transfer and skin friction. Charts of the solutions are presented for making pressure-drop calculations. A technique of using the charts to determine the position of a normal shock in a tube is described.

  16. Laboratory manual for static pressure drop experiments in LMFBR wire wrapped rod bundles

    SciTech Connect

    Burns, K.J.; Todreas, N.E.

    1980-07-01

    Purpose of this experiment is to determine both interior and edge subchannel axial pressure drops for a range of Reynolds numbers. The subchannel static pressure drop is used to calculate subchannel and bundle average friction factors, which can be used to verify existing friction factor correlations. The correlations for subchannel friction factors are used as input to computer codes which solve the coupled energy, continuity, and momentum equations, and are also used to develop flow split correlations which are needed as input to codes which solve only the energy equation. The bundle average friction factor is used to calculate the overall bundle pressure drop, which determines the required pumping power.

  17. LHe Flow Regime/Pressure Drop for D0 Solenoid at Steady State Conditions

    SciTech Connect

    Rucinski, R.; /Fermilab

    1993-03-03

    This paper describes in a note taking format what was learned from several sources on two phase liquid helium flow regimes and pressure drops as applied to the D-Zero solenoid upgrade project. Calculations to estimate the steady state conditions for the D-Zero solenoid at 5, 10 and 15 g/s are also presented. For the lower flow rates a stratified type regime can be expected with a pressure drop less than 0.5 psi. For the higher flow rate a more homogeneous flow regime can be expected with a pressure drop between 0.4 to 1.5 psi.

  18. Stretching and squeezing of sessile dielectric drops by the optical radiation pressure.

    PubMed

    Chraïbi, Hamza; Lasseux, Didier; Arquis, Eric; Wunenburger, Régis; Delville, Jean-Pierre

    2008-06-01

    We study numerically the deformation of sessile dielectric drops immersed in a second fluid when submitted to the optical radiation pressure of a continuous Gaussian laser wave. Both drop stretching and drop squeezing are investigated at steady state where capillary effects balance the optical radiation pressure. A boundary integral method is implemented to solve the axisymmetric Stokes flow in the two fluids. In the stretching case, we find that the drop shape goes from prolate to near-conical for increasing optical radiation pressure whatever the drop to beam radius ratio and the refractive index contrast between the two fluids. The semiangle of the cone at equilibrium decreases with the drop to beam radius ratio and is weakly influenced by the index contrast. Above a threshold value of the radiation pressure, these "optical cones" become unstable and a disruption is observed. Conversely, when optically squeezed, the drop shifts from an oblate to a concave shape leading to the formation of a stable "optical torus." These findings extend the electrohydrodynamics approach of drop deformation to the much less investigated "optical domain" and reveal the openings offered by laser waves to actively manipulate droplets at the micrometer scale.

  19. Beyond Bernoulli: Improving the Accuracy and Precision of Noninvasive Estimation of Peak Pressure Drops.

    PubMed

    Donati, Fabrizio; Myerson, Saul; Bissell, Malenka M; Smith, Nicolas P; Neubauer, Stefan; Monaghan, Mark J; Nordsletten, David A; Lamata, Pablo

    2017-01-01

    Transvalvular peak pressure drops are routinely assessed noninvasively by echocardiography using the Bernoulli principle. However, the Bernoulli principle relies on several approximations that may not be appropriate, including that the majority of the pressure drop is because of the spatial acceleration of the blood flow, and the ejection jet is a single streamline (single peak velocity value). We assessed the accuracy of the Bernoulli principle to estimate the peak pressure drop at the aortic valve using 3-dimensional cardiovascular magnetic resonance flow data in 32 subjects. Reference pressure drops were computed from the flow field, accounting for the principles of physics (ie, the Navier-Stokes equations). Analysis of the pressure components confirmed that the spatial acceleration of the blood jet through the valve is most significant (accounting for 99% of the total drop in stenotic subjects). However, the Bernoulli formulation demonstrated a consistent overestimation of the transvalvular pressure (average of 54%, range 5%-136%) resulting from the use of a single peak velocity value, which neglects the velocity distribution across the aortic valve plane. This assumption was a source of uncontrolled variability. The application of the Bernoulli formulation results in a clinically significant overestimation of peak pressure drops because of approximation of blood flow as a single streamline. A corrected formulation that accounts for the cross-sectional profile of the blood flow is proposed and adapted to both cardiovascular magnetic resonance and echocardiographic data. © 2017 The Authors.

  20. Effects of pressure drop and superficial velocity on the bubbling fluidized bed incinerator.

    PubMed

    Wang, Feng-Jehng; Chen, Suming; Lei, Perng-Kwei; Wu, Chung-Hsing

    2007-12-01

    Since performance and operational conditions, such as superficial velocity, pressure drop, particles viodage, and terminal velocity, are difficult to measure on an incinerator, this study used computational fluid dynamics (CFD) to determine numerical solutions. The effects of pressure drop and superficial velocity on a bubbling fluidized bed incinerator (BFBI) were evaluated. Analytical results indicated that simulation models were able to effectively predict the relationship between superficial velocity and pressure drop over bed height in the BFBI. Second, the models in BFBI were simplified to simulate scale-up beds without excessive computation time. Moreover, simulation and experimental results showed that minimum fluidization velocity of the BFBI must be controlled in at 0.188-3.684 m/s and pressure drop was mainly caused by bed particles.

  1. Heat transfer and pressure drop for air flow through enhanced passages. Final report

    SciTech Connect

    Obot, N.T.; Esen, E.B.

    1992-06-01

    An extensive experimental investigation was carried out to determine the pressure drop and heat transfer characteristics for laminar, transitional and turbulent flow of air through a smooth passage and twenty-three enhanced passages. The internal surfaces of all enhanced passages had spirally shaped geometries; these included fluted, finned/ribbed and indented surfaces. The Reynolds number (Re) was varied between 400 and 50000. The effect of heat transfer (wall cooling or fluid heating) on pressure drop is most significant within the transition region; the recorded pressure drop with heat transfer is much higher than that without heat transfer. The magnitude of this effect depends markedly on the average surface temperature and, to a lesser extent, on the geometric characteristics of the enhanced surfaces. When the pressure drop data are reduced as values of the Fanning friction factor(f), the results are about the same with and without heat transfer for turbulent flow, with moderate differences in the laminar and transition regions.

  2. Heat transfer and pressure drop for air flow through enhanced passages

    SciTech Connect

    Obot, N.T.; Esen, E.B.

    1992-06-01

    An extensive experimental investigation was carried out to determine the pressure drop and heat transfer characteristics for laminar, transitional and turbulent flow of air through a smooth passage and twenty-three enhanced passages. The internal surfaces of all enhanced passages had spirally shaped geometries; these included fluted, finned/ribbed and indented surfaces. The Reynolds number (Re) was varied between 400 and 50000. The effect of heat transfer (wall cooling or fluid heating) on pressure drop is most significant within the transition region; the recorded pressure drop with heat transfer is much higher than that without heat transfer. The magnitude of this effect depends markedly on the average surface temperature and, to a lesser extent, on the geometric characteristics of the enhanced surfaces. When the pressure drop data are reduced as values of the Fanning friction factor(f), the results are about the same with and without heat transfer for turbulent flow, with moderate differences in the laminar and transition regions.

  3. Study made of heat transfer and pressure drop through tubes with internal interrupted fins

    NASA Technical Reports Server (NTRS)

    Namkoong, D., Jr.

    1967-01-01

    Argon gas flow through an internal interrupted finned tube was investigated to obtain heat transfer and frictional pressure drop data. The results were plotted against the same data for corresponding louvered plate-finned surfaces.

  4. Comparative studies of hemoperfusion devices. II. Pressure drop and flow uniformity tests.

    PubMed

    Cooney, D O; Infantolino, W; Kane, R

    1979-01-01

    One resin-based hemoperfusion device and three charcoal-based hemoperfusion devices were tested to determine their pressure drop and flow uniformity characteristics. Measurements were made on pressure drop versus flow rate using distilled water and on pressure drop versus time using bovine blood. Effluent concentration curves obtained after the step-change introduction of a high molecular weight dye solution to each unit were used to determine the priming volumes of the devices and were interpreted to yield information regarding the uniformities of flow in each device. The pressure drop and priming volume values for the resin-based device were significantly higher than the corresponding values for the charcoal-based units.

  5. The pressure hold/drop integrity test; its correlation to diffusive flow.

    PubMed

    Trotter, A M; Meltzer, T H

    1998-01-01

    The pressure-drop/hold procedure enables the diffusive flow integrity testing of filters to be performed without breaching the system downstream of the filter. It is not necessary to measure volumetrically the diffused gas on the downstream side of the filter. By means of pressure transducers the pressure loss is determined upstream; thus eliminating the threat of sepsis due to down-stream invasions. The pressure decay exercise can be used to characterize the various filter types. A constancy of filter manufacture is required for a given filter type. Unless the pressure drop exceeds the value established as the maximum allowable decay, the filter is judged to be integral. It qualifies as a sterilizing grade filter. Excessive pressure decays will also eventuate from leaks, as from improperly sealed housings. Performed prior to the filtration, the procedure serves to eliminate the wasteful use of an imperfect system, whether caused by faulty sealing, incorrect filter type or flawed filters. Where leaks are detected, the filter can be reexamined for its integrity. To enable the pressure-drop procedure to serve as an integrity test, the measured pressure decays require being correlated with organism retention data. This is made possible by the arithmetic conversion of the pressure decay curve into the conventional diffusive airflow curve established to have such a correlation. The transformation of the pressure-drop curve into the differential airflow plot is automatically performed by certain of the automated integrity test machines. These devices, utilizing pressure transducers, are capable of measuring small pressure drops with requisite sensitivity; gauges commonly are not. Moreover, as previously stated, the measurements are advantageously made on the upside of the filter. The use of automated test machines is, therefore, recommended for the performance of the pressure hold/drop integrity test in furtherance of the practice of filter integrity testing.

  6. Effect of flow rate and temperature on transmembrane blood pressure drop in an extracorporeal artificial lung.

    PubMed

    Park, M; Costa, E L V; Maciel, A T; Barbosa, E V S; Hirota, A S; Schettino, G de P; Azevedo, L C P

    2014-11-01

    Transmembrane pressure drop reflects the resistance of an artificial lung system to blood transit. Decreased resistance (low transmembrane pressure drop) enhances blood flow through the oxygenator, thereby, enhancing gas exchange efficiency. This study is part of a previous one where we observed the behaviour and the modulation of blood pressure drop during the passage of blood through artificial lung membranes. Before and after the induction of multi-organ dysfunction, the animals were instrumented and analysed for venous-venous extracorporeal membrane oxygenation, using a pre-defined sequence of blood flows. Blood flow and revolutions per minute (RPM) of the centrifugal pump varied in a linear fashion. At a blood flow of 5.5 L/min, pre- and post-pump blood pressures reached -120 and 450 mmHg, respectively. Transmembrane pressures showed a significant spread, particularly at blood flows above 2 L/min; over the entire range of blood flow rates, there was a positive association of pressure drop with blood flow (0.005 mmHg/mL/minute of blood flow) and a negative association of pressure drop with temperature (-4.828 mmHg/(°Celsius). These associations were similar when blood flows of below and above 2000 mL/minute were examined. During its passage through the extracorporeal system, blood is exposed to pressure variations from -120 to 450 mmHg. At high blood flows (above 2 L/min), the drop in transmembrane pressure becomes unpredictable and highly variable. Over the entire range of blood flows investigated (0-5500 mL/min), the drop in transmembrane pressure was positively associated with blood flow and negatively associated with body temperature. © The Author(s) 2014.

  7. Pressure drop measurements of prototype NET and CEA cable-in-conduit conductors (CICCs)

    SciTech Connect

    Maekawa, R.; Smith, M.R.; Van Sciver, S.W.

    1996-12-31

    The pressure drop of two prototype cable-in-conduit conductors (CICCs) were measured. The NET conductor is a conventional type CICC, while the CEA conductor has a central flow channel to reduce hydraulic impedance. The pressure drop measurements were conducted with helium at temperatures ranging from 2K to 4.7K, and pressure from the saturated vapor pressure to in excess of 3 bar. Computer image analysis was used to estimate the flow cross sectional area and wetted perimeter of the conductors. The data are expressed in terms of a classical friction factor, and compared with precious experimental results.

  8. Effect of bed pressure drop on performance of a CFB boiler

    SciTech Connect

    Hairui Yang; Hai Zhang; Shi Yang; Guangxi Yue; Jun Su; Zhiping Fu

    2009-05-15

    The effect of bed pressure drop and bed inventory on the performances of a circulating fluidized bed (CFB) boiler was studied. By using the state specification design theory, the fluidization state of the gas-solids flow in the furnace of conventional CFB boilers was reconstructed to operate at a much lower bed pressure drop by reducing bed inventory and control bed quality. Through theoretical analysis, it was suggested that there would exist a theoretical optimal value of bed pressure drop, around which the boiler operation can achieve the maximal combustion efficiency and with significant reduction of the wear of the heating surface and fan energy consumption. The analysis was validated by field tests carried out in a 75 t/h CFB boiler. At full boiler load, when bed pressure drop was reduced from 7.3 to 3.2 kPa, the height of the dense zone in the lower furnace decreased, but the solid suspension density profile in the upper furnace and solid flow rate were barely influenced. Consequently, the average heat transfer coefficient in the furnace was kept nearly the same and the furnace temperature increment was less than 17{sup o}C. It was also found that the carbon content in the fly ash decreased first with decreasing bed pressure drop and then increased with further increasing bed pressure drop. The turning point with minimal carbon content was referred to as the point with optimal bed pressure drop. For this boiler, at the optimum point the bed pressure was around 5.7 kPa with the overall excess air ratio of 1.06. When the boiler was operated around this optimal point, not only the combustion efficiency was improved, but also fan energy consumption and wear of heating surface were reduced. 23 refs., 6 figs., 4 tabs.

  9. Pressure drop of slug flow in microchannels with increasing void fraction: experiment and modeling.

    PubMed

    Molla, Shahnawaz; Eskin, Dmitry; Mostowfi, Farshid

    2011-06-07

    Pressure drop in a gas-liquid slug flow through a long microchannel of rectangular cross-section was investigated. Pressure measurements in a lengthy (∼0.8 m) microchannel determined the pressure gradient to be constant in a flow where gas bubbles progressively expanded and the flow velocity increased due to a significant pressure drop. Most of the earlier studies of slug flow in microchannels considered systems where the expansion of the gas bubbles was negligible in the channel. In contrast, we investigated systems where the volume of the gas phase increased significantly due to a large pressure drop (up to 1811 kPa) along the channel. This expansion of the gas phase led to a significant increase in the void fraction, causing considerable flow acceleration. The pressure drop in the microchannel was studied for three gas-liquid systems; water-nitrogen, dodecane-nitrogen, and pentadecane-nitrogen. Inside the microchannel, local pressure was measured using a series of embedded membranes acting as pressure sensors. Our investigation of the pressure drop showed a linear trend over a wide range of void fractions and flow conditions in the two-phase flow. The lengths and the velocities of the liquid slugs and the gas bubbles were also studied along the microchannel by employing a video imaging technique. Furthermore, a model describing the gas-liquid slug flow in a long microchannel was developed to calculate the pressure drop under conditions similar to the experiments. An excellent agreement between the developed model and the experimental data was obtained.

  10. Experimental microbubble generation by sudden pressure drop and fluidics

    NASA Astrophysics Data System (ADS)

    Franco Gutierrez, Fernando; Figueroa Espinoza, Bernardo; Aguilar Corona, Alicia; Vargas Correa, Jesus; Solorio Diaz, Gildardo

    2014-11-01

    Mass and heat transfer, as well as chemical species in bubbly flow are of importance in environmental and industrial applications. Microbubbles are well suited to these applications due to the large interface contact area and residence time. The objective of this investigation is to build devices to produce microbubbles using two methods: pressure differences and fluidics. Some characteristics, advantages and drawbacks of both methods are briefly discussed, as well as the characterization of the bubbly suspensions in terms of parameters such as the pressure jump and bubble equivalent diameter distribution. The authors acknowledge the support of Consejo Nacional de Ciencia y Tecnología.

  11. Investigation of pressure drop in capillary tube for mixed refrigerant Joule-Thomson cryocooler

    SciTech Connect

    Ardhapurkar, P. M.; Sridharan, Arunkumar; Atrey, M. D.

    2014-01-29

    A capillary tube is commonly used in small capacity refrigeration and air-conditioning systems. It is also a preferred expansion device in mixed refrigerant Joule-Thomson (MR J-T) cryocoolers, since it is inexpensive and simple in configuration. However, the flow inside a capillary tube is complex, since flashing process that occurs in case of refrigeration and air-conditioning systems is metastable. A mixture of refrigerants such as nitrogen, methane, ethane, propane and iso-butane expands below its inversion temperature in the capillary tube of MR J-T cryocooler and reaches cryogenic temperature. The mass flow rate of refrigerant mixture circulating through capillary tube depends on the pressure difference across it. There are many empirical correlations which predict pressure drop across the capillary tube. However, they have not been tested for refrigerant mixtures and for operating conditions of the cryocooler. The present paper assesses the existing empirical correlations for predicting overall pressure drop across the capillary tube for the MR J-T cryocooler. The empirical correlations refer to homogeneous as well as separated flow models. Experiments are carried out to measure the overall pressure drop across the capillary tube for the cooler. Three different compositions of refrigerant mixture are used to study the pressure drop variations. The predicted overall pressure drop across the capillary tube is compared with the experimentally obtained value. The predictions obtained using homogeneous model show better match with the experimental results compared to separated flow models.

  12. Investigation of pressure drop in capillary tube for mixed refrigerant Joule-Thomson cryocooler

    NASA Astrophysics Data System (ADS)

    Ardhapurkar, P. M.; Sridharan, Arunkumar; Atrey, M. D.

    2014-01-01

    A capillary tube is commonly used in small capacity refrigeration and air-conditioning systems. It is also a preferred expansion device in mixed refrigerant Joule-Thomson (MR J-T) cryocoolers, since it is inexpensive and simple in configuration. However, the flow inside a capillary tube is complex, since flashing process that occurs in case of refrigeration and air-conditioning systems is metastable. A mixture of refrigerants such as nitrogen, methane, ethane, propane and iso-butane expands below its inversion temperature in the capillary tube of MR J-T cryocooler and reaches cryogenic temperature. The mass flow rate of refrigerant mixture circulating through capillary tube depends on the pressure difference across it. There are many empirical correlations which predict pressure drop across the capillary tube. However, they have not been tested for refrigerant mixtures and for operating conditions of the cryocooler. The present paper assesses the existing empirical correlations for predicting overall pressure drop across the capillary tube for the MR J-T cryocooler. The empirical correlations refer to homogeneous as well as separated flow models. Experiments are carried out to measure the overall pressure drop across the capillary tube for the cooler. Three different compositions of refrigerant mixture are used to study the pressure drop variations. The predicted overall pressure drop across the capillary tube is compared with the experimentally obtained value. The predictions obtained using homogeneous model show better match with the experimental results compared to separated flow models.

  13. Pressure drop characteristics of cryogenic mixed refrigerant at macro and micro channel heat exchangers

    NASA Astrophysics Data System (ADS)

    Baek, Seungwhan; Jeong, Sangkwon; Hwang, Gyuwan

    2012-12-01

    Mixed Refrigerant-Joule Thomson (MR-JT) refrigerators are widely used in various kinds of cryogenic systems these days. The temperature glide effect is one of the major features of using mixed refrigerants since a recuperative heat exchanger in a MR-JT refrigerator is utilized for mostly two-phase flow. Although a pressure drop estimation for a multi-phase and multi-component fluid in the cryogenic temperature range is necessarily required in MR-JT refrigerator heat exchanger designs, it has been rarely discussed so far. In this paper, macro heat exchangers and micro heat exchangers are compared in order to investigate the pressure drop characteristics in the experimental MR-JT refrigerator operation. The tube in tube heat exchanger (TTHE) is a well-known macro-channel heat exchanger in MR-JT refrigeration. Printed Circuit Heat Exchangers (PCHEs) have been developed as a compact heat exchanger with micro size channels. Several two-phase pressure drop correlations are examined to discuss the experimental pressure measurement results. The result of this paper shows that cryogenic mixed refrigerant pressure drop can be estimated with conventional two-phase pressure drop correlations if an appropriate flow pattern is identified.

  14. Analysis of pressure drop and heat transfer data from the reversing flow test facility

    SciTech Connect

    Roach, P D; Bell, K J

    1989-05-01

    The Reversing Flow Test Facility is part of the heat engine R and D capabilities at Argonne National Laboratory. The facility permits the study of heat transfer and pressure drop under conditions of rapidly reversing flow. This report summarizes the results that have been obtained to date from more than 100 data sets that cover a wide range of temperatures, pressures, and frequencies. Pressure drop data are presented as normalized pressure drop vs. the Reynolds number calculated from the amplitude of the oscillatory flow. Heat transfer data for the regenerators are presented as regenerator effectiveness vs. Reynolds number. Three significant conclusions are derived from our analysis of the data: (1) no frequency dependence is observed in either the pressure drop or the heat transfer data, (2) the measured pressure drops for the heater and coolers are distinctly higher than those calculated from steady-flow correlations, and (3) the heat transfer coefficient in the heater is about 80 percent of that predicted by steady-flow correlations. The correlations presented here provide the basis for improving existing models. 4 refs., 20 figs., 3 tabs.

  15. Novel cyclone empirical pressure drop and emissions with heterogeneous particulate

    USDA-ARS?s Scientific Manuscript database

    New cyclone designs equally effective at controlling emissions that have smaller pressure losses would reduce both the financial and the environmental cost of procuring electricity. Tests were conducted with novel and industry standard 30.5 cm diameter cyclones at inlet velocities from 8 to 18 m s-...

  16. Detection of bubble nucleation event in superheated drop detector by the pressure sensor

    NASA Astrophysics Data System (ADS)

    Das, Mala; Biswas, Nilanjan

    2017-01-01

    Superheated drop detector consisting of drops of superheated liquid suspended in polymer or gel matrix is of great demand, mainly because of its insensitivity to ß-particles and ?-rays and also because of the low cost. The bubble nucleation event is detected by measuring the acoustic shock wave released during the nucleation process. The present work demonstrates the detection of bubble nucleation events by using the pressure sensor. The associated circuits for the measurement are described in this article. The detection of events is verified by measuring the events with the acoustic sensor. The measurement was done using drops of various sizes to study the effect of the size of the drop on the pressure recovery time. Probability of detection of events has increased for larger size of the superheated drops and lesser volume of air in contact with the gel matrix. The exponential decay fitting to the pressure sensor signals shows the dead time for pressure recovery of such a drop detector to be a few microseconds.

  17. Large scale steam flow test: Pressure drop data and calculated pressure loss coefficients

    SciTech Connect

    Meadows, J.B.; Spears, J.R.; Feder, A.R.; Moore, B.P.; Young, C.E.

    1993-12-01

    This report presents the result of large scale steam flow testing, 3 million to 7 million lbs/hr., conducted at approximate steam qualities of 25, 45, 70 and 100 percent (dry, saturated). It is concluded from the test data that reasonable estimates of piping component pressure loss coefficients for single phase flow in complex piping geometries can be calculated using available engineering literature. This includes the effects of nearby upstream and downstream components, compressibility, and internal obstructions, such as splitters, and ladder rungs on individual piping components. Despite expected uncertainties in the data resulting from the complexity of the piping geometry and two-phase flow, the test data support the conclusion that the predicted dry steam K-factors are accurate and provide useful insight into the effect of entrained liquid on the flow resistance. The K-factors calculated from the wet steam test data were compared to two-phase K-factors based on the Martinelli-Nelson pressure drop correlations. This comparison supports the concept of a two-phase multiplier for estimating the resistance of piping with liquid entrained into the flow. The test data in general appears to be reasonably consistent with the shape of a curve based on the Martinelli-Nelson correlation over the tested range of steam quality.

  18. Pressure Drop and Heat Transfer Characteristics of Boiling Nitrogen in Square Pipe flow

    NASA Astrophysics Data System (ADS)

    Ohira, Katsuhide; Nakayama, Tadashi; Takahashi, Koichi; Kobayashi, Hiroaki; Taguchi, Hideyuki; Aoki, Itsuo

    Pressure drop and forced convection heat transfer were studied in the boiling nitrogen flow in a horizontal square pipe with a side of 12 mm at inlet pressure between 0.1 and0.15 MPa with a mass flux between 70 and 2000 kg/m2-s and with a heat flux of 5, 10 and 20 kW/m2. Accordingly, the flow and heat transfer mechanisms specific to square pipe were elucidated, and the applicability to cryogenic fluids of pressure drop and heat transfer models originally proposed for room temperature fluids was clarified.

  19. Negative pressures and spallation in water drops subjected to nanosecond shock waves

    SciTech Connect

    Stan, Claudiu A.; Willmott, Philip R.; Stone, Howard A.; Koglin, Jason E.; Liang, Mengning; Aquila, Andrew L.; Robinson, Joseph S.; Gumerlock, Karl L.; Blaj, Gabriel; Sierra, Raymond G.; Boutet, Sebastien; Guillet, Serge A. H.; Curtis, Robin H.; Vetter, Sharon L.; Loos, Henrik; Turner, James L.; Decker, Franz -Josef

    2016-05-16

    Most experimental studies of cavitation in liquid water at negative pressures reported cavitation at tensions significantly smaller than those expected for homogeneous nucleation, suggesting that achievable tensions are limited by heterogeneous cavitation. We generated tension pulses with nanosecond rise times in water by reflecting cylindrical shock waves, produced by X-ray laser pulses, at the internal surface of drops of water. Depending on the X-ray pulse energy, a range of cavitation phenomena occurred, including the rupture and detachment, or spallation, of thin liquid layers at the surface of the drop. When spallation occurred, we evaluated that negative pressures below –100 MPa were reached in the drops. As a result, we model the negative pressures from shock reflection experiments using a nucleation-and-growth model that explains how rapid decompression could outrun heterogeneous cavitation in water, and enable the study of stretched water close to homogeneous cavitation pressures.

  20. Negative pressures and spallation in water drops subjected to nanosecond shock waves

    DOE PAGES

    Stan, Claudiu A.; Willmott, Philip R.; Stone, Howard A.; ...

    2016-05-16

    Most experimental studies of cavitation in liquid water at negative pressures reported cavitation at tensions significantly smaller than those expected for homogeneous nucleation, suggesting that achievable tensions are limited by heterogeneous cavitation. We generated tension pulses with nanosecond rise times in water by reflecting cylindrical shock waves, produced by X-ray laser pulses, at the internal surface of drops of water. Depending on the X-ray pulse energy, a range of cavitation phenomena occurred, including the rupture and detachment, or spallation, of thin liquid layers at the surface of the drop. When spallation occurred, we evaluated that negative pressures below –100 MPamore » were reached in the drops. As a result, we model the negative pressures from shock reflection experiments using a nucleation-and-growth model that explains how rapid decompression could outrun heterogeneous cavitation in water, and enable the study of stretched water close to homogeneous cavitation pressures.« less

  1. Negative Pressures and Spallation in Water Drops Subjected to Nanosecond Shock Waves.

    PubMed

    Stan, Claudiu A; Willmott, Philip R; Stone, Howard A; Koglin, Jason E; Liang, Mengning; Aquila, Andrew L; Robinson, Joseph S; Gumerlock, Karl L; Blaj, Gabriel; Sierra, Raymond G; Boutet, Sébastien; Guillet, Serge A H; Curtis, Robin H; Vetter, Sharon L; Loos, Henrik; Turner, James L; Decker, Franz-Josef

    2016-06-02

    Most experimental studies of cavitation in liquid water at negative pressures reported cavitation at tensions significantly smaller than those expected for homogeneous nucleation, suggesting that achievable tensions are limited by heterogeneous cavitation. We generated tension pulses with nanosecond rise times in water by reflecting cylindrical shock waves, produced by X-ray laser pulses, at the internal surface of drops of water. Depending on the X-ray pulse energy, a range of cavitation phenomena occurred, including the rupture and detachment, or spallation, of thin liquid layers at the surface of the drop. When spallation occurred, we evaluated that negative pressures below -100 MPa were reached in the drops. We model the negative pressures from shock reflection experiments using a nucleation-and-growth model that explains how rapid decompression could outrun heterogeneous cavitation in water, and enable the study of stretched water close to homogeneous cavitation pressures.

  2. Negative pressures and spallation in water drops subjected to nanosecond shock waves

    SciTech Connect

    Stan, Claudiu A.; Willmott, Philip R.; Stone, Howard A.; Koglin, Jason E.; Liang, Mengning; Aquila, Andrew L.; Robinson, Joseph S.; Gumerlock, Karl L.; Blaj, Gabriel; Sierra, Raymond G.; Boutet, Sebastien; Guillet, Serge A. H.; Curtis, Robin H.; Vetter, Sharon L.; Loos, Henrik; Turner, James L.; Decker, Franz -Josef

    2016-05-16

    Most experimental studies of cavitation in liquid water at negative pressures reported cavitation at tensions significantly smaller than those expected for homogeneous nucleation, suggesting that achievable tensions are limited by heterogeneous cavitation. We generated tension pulses with nanosecond rise times in water by reflecting cylindrical shock waves, produced by X-ray laser pulses, at the internal surface of drops of water. Depending on the X-ray pulse energy, a range of cavitation phenomena occurred, including the rupture and detachment, or spallation, of thin liquid layers at the surface of the drop. When spallation occurred, we evaluated that negative pressures below –100 MPa were reached in the drops. As a result, we model the negative pressures from shock reflection experiments using a nucleation-and-growth model that explains how rapid decompression could outrun heterogeneous cavitation in water, and enable the study of stretched water close to homogeneous cavitation pressures.

  3. Effect of flameholder pressure drop on emissions and performance of premixed-prevaporized combustors

    NASA Technical Reports Server (NTRS)

    Duerr, R. A.; Lyons, V. J.

    1983-01-01

    Parametric tests were conducted to determine the effects of flameholder pressure drop on the emissions and performance of lean premixed-prevaporized combustors. A conical flameholder mounted in a diverging duct was tested with two values of flameholder blockage. Emissions of nitrogen oxides, carbon monoxide, carbon dioxide, and unburned hydrocarbons were measured for combustor entrance conditions of 600 to 800 K air temperature, 0.3 MPa to 0.5 MPa pressure, and 20 m/sec to 35 m/sec reference velocity. Jet A fuel was injected at flow rates corresponding to an equivalence ratio range from 0.8 down to the lean stability limit. Emission results for the high-blockage flameholder were a substantial improvement over the low-blockage emission results. A correlation of combustion efficiency with flameholder pressure drop was developed for pressure drops less than 9 percent.

  4. Variability among electronic cigarettes in the pressure drop, airflow rate, and aerosol production.

    PubMed

    Williams, Monique; Talbot, Prue

    2011-12-01

    This study investigated the performance of electronic cigarettes (e-cigarettes), compared different models within a brand, compared identical copies of the same model within a brand, and examined performance using different protocols. Airflow rate required to generate aerosol, pressure drop across e-cigarettes, and aerosol density were examined using three different protocols. First 10 puff protocol: The airflow rate required to produce aerosol and aerosol density varied among brands, while pressure drop varied among brands and between the same model within a brand. Total air hole area correlated with pressure drop for some brands. Smoke-out protocol: E-cigarettes within a brand generally performed similarly when puffed to exhaustion; however, there was considerable variation between brands in pressure drop, airflow rate required to produce aerosol, and the total number of puffs produced. With this protocol, aerosol density varied significantly between puffs and gradually declined. CONSECUTIVE TRIAL PROTOCOL: Two copies of one model were subjected to 11 puffs in three consecutive trials with breaks between trials. One copy performed similarly in each trial, while the second copy of the same model produced little aerosol during the third trial. The different performance properties of the two units were attributed to the atomizers. There was significant variability between and within brands in the airflow rate required to produce aerosol, pressure drop, length of time cartridges lasted, and production of aerosol. Variation in performance properties within brands suggests a need for better quality control during e-cigarette manufacture.

  5. Fast and accurate pressure-drop prediction in straightened atherosclerotic coronary arteries.

    PubMed

    Schrauwen, Jelle T C; Koeze, Dion J; Wentzel, Jolanda J; van de Vosse, Frans N; van der Steen, Anton F W; Gijsen, Frank J H

    2015-01-01

    Atherosclerotic disease progression in coronary arteries is influenced by wall shear stress. To compute patient-specific wall shear stress, computational fluid dynamics (CFD) is required. In this study we propose a method for computing the pressure-drop in regions proximal and distal to a plaque, which can serve as a boundary condition in CFD. As a first step towards exploring the proposed method we investigated ten straightened coronary arteries. First, the flow fields were calculated with CFD and velocity profiles were fitted on the results. Second, the Navier-Stokes equation was simplified and solved with the found velocity profiles to obtain a pressure-drop estimate (Δp (1)). Next, Δp (1) was compared to the pressure-drop from CFD (Δp CFD) as a validation step. Finally, the velocity profiles, and thus the pressure-drop were predicted based on geometry and flow, resulting in Δp geom. We found that Δp (1) adequately estimated Δp CFD with velocity profiles that have one free parameter β. This β was successfully related to geometry and flow, resulting in an excellent agreement between Δp CFD and Δp geom: 3.9 ± 4.9% difference at Re = 150. We showed that this method can quickly and accurately predict pressure-drop on the basis of geometry and flow in straightened coronary arteries that are mildly diseased.

  6. Experimental investigation of ice slurry flow pressure drop in horizontal tubes

    SciTech Connect

    Grozdek, Marino; Khodabandeh, Rahmatollah; Lundqvist, Per

    2009-01-15

    Pressure drop behaviour of ice slurry based on ethanol-water mixture in circular horizontal tubes has been experimentally investigated. The secondary fluid was prepared by mixing ethyl alcohol and water to obtain initial alcohol concentration of 10.3% (initial freezing temperature -4.4 C). The pressure drop tests were conducted to cover laminar and slightly turbulent flow with ice mass fraction varying from 0% to 30% depending on test conditions. Results from flow tests reveal much higher pressure drop for higher ice concentrations and higher velocities in comparison to the single phase flow. However for ice concentrations of 15% and higher, certain velocity exists at which ice slurry pressure drop is same or even lower than for single phase flow. It seems that higher ice concentration delay flow pattern transition moment (from laminar to turbulent) toward higher velocities. In addition experimental results for pressure drop were compared to the analytical results, based on Poiseulle and Buckingham-Reiner models for laminar flow, Blasius, Darby and Melson, Dodge and Metzner, Steffe and Tomita for turbulent region and general correlation of Kitanovski which is valid for both flow regimes. For laminar flow and low buoyancy numbers Buckingham-Reiner method gives good agreement with experimental results while for turbulent flow best fit is provided with Dodge-Metzner and Tomita methods. Furthermore, for transport purposes it has been shown that ice mass fraction of 20% offers best ratio of ice slurry transport capability and required pumping power. (author)

  7. Flow rate-pressure drop relation for deformable shallow microfluidic channels

    NASA Astrophysics Data System (ADS)

    Christov, Ivan C.; Cognet, Vincent; Stone, Howard A.

    2013-11-01

    Laminar flow in devices fabricated from PDMS causes deformation of the passage geometry, which affects the flow rate-pressure drop relation. Having an accurate flow rate-pressure drop relation for deformable microchannels is of importance given that the flow rate for a given pressure drop can be as much as 500% of the flow rate predicted by Poiseuille's law for a rigid channel. proposed a successful model of the latter phenomenon by heuristically coupling linear elasticity with the lubrication approximation for Stokes flow. However, their model contains a fitting parameter that must be found for each channel shape by performing an experiment. We present a perturbative derivation of the flow rate-pressure drop relation in a shallow deformable microchannel using Kirchoff-Love theory of isotropic quasi-static plate bending and Stokes' equations under a ``double lubrication'' approximation (i.e., the ratio of the channel's height to its width and of the channel's width to its length are both assumed small). Our result contains no free parameters and confirms Gervais et al.'s observation that the flow rate is a quartic polynomial of the pressure drop. ICC was supported by NSF Grant DMS-1104047 and the U.S. DOE through the LANL/LDRD Program; HAS was supported by NSF Grant CBET-1132835.

  8. A Validated All-Pressure Fluid Drop Model and Lewis Number Effects for a Binary Mixture

    NASA Technical Reports Server (NTRS)

    Harstad, K.; Bellan, J.

    1999-01-01

    The differences between subcritical liquid drop and supercritical fluid drop behavior are discussed. Under subcritical, evaporative high emission rate conditions, a film layer is present in the inner part of the drop surface which contributes to the unique determination of the boundary conditions; it is this film layer which contributes to the solution's convective-diffusive character. In contrast, under supercritical condition as the boundary conditions contain a degree of arbitrariness due to the absence of a surface, and the solution has then a purely diffusive character. Results from simulations of a free fluid drop under no-gravity conditions are compared to microgravity experimental data from suspended, large drop experiments at high, low and intermediary temperatures and in a range of pressures encompassing the sub-and supercritical regime. Despite the difference between the conditions of the simulations and experiments (suspension vs. free floating), the time rate of variation of the drop diameter square is remarkably well predicted in the linear curve regime. The drop diameter is determined in the simulations from the location of the maximum density gradient, and agrees well with the data. It is also shown that the classical calculation of the Lewis number gives qualitatively erroneous results at supercritical conditions, but that an effective Lewis number previously defined gives qualitatively correct estimates of the length scales for heat and mass transfer at all pressures.

  9. Nucleate boiling pressure drop in an annulus: Book 5

    SciTech Connect

    Not Available

    1992-11-01

    The application of the work described in this report is the production reactors at the Savannah River Site, and the context is nuclear reactor safety. The Loss of Coolant Accident (LOCA) scenario considered involves a double-ended break of a primary coolant pipe in the reactor. During a LOCA, the flow through portions of the reactor may reverse direction or be greatly reduced, depending upon the location of the break. The reduced flow rate of coolant (D{sub 2}O) through the fuel assembly channels of the reactor -- downflow in this situation -- can lead to boiling and to the potential for flow instabilities which may cause some of the fuel assembly channels to overheat and melt. That situation is to be avoided. The experimental approach is to provide a test annulus which simulates geometry, materials, and flow conditions in a Mark-22 fuel assembly (Coolant Channel 3) to the extent possible. The key analysis approaches are: To compare the minima in the measured demand curves with analytical criteria, in particular the Saha-Zuber (1974) model; and to compare the pressure and temperature as a function of length in the annulus with an integral model for flow boiling in a heated channel. Nineteen test series and a total of 178 tests were performed. Testing addressed the effects of: Heat flux; pressure; helium gas; power tilt; ribs; asymmetric heat flux. This document consists solely of the plato file index from 11/87 to 11/90.

  10. Mineral matter transformations in a pressurized drop-tube furnace

    SciTech Connect

    Swanson, M.L.; Tibbetts, J.E.

    1992-01-01

    To meet the objectives of the program, a pressurized combustion vessel was built to allow the operating parameters of a direct-fired gas turbine combustor to be simulated. One goal in building this equipment was to design the gas turbine simulator as small as possible to reduce the quantity of test fuel needed, while not undersizing the combustor such that wall effects had a significant effect on the measured combustion performance. Based on computer modeling, a rich-lean, two-stage, nonslagging combustor was constructed to simulate a direct-fired gas turbine. This design was selected to maximize the information that could be obtained on the impact of low-rank coal's unique properties on the gas turbine combustor, its turbomachinery, and the required hot-gas cleanup devices (such as high-temperature/high-pressure (HTHP) cyclones). Seventeen successful combustion tests using coal-water fuels were completed. These tests included seven tests with a commercially available Otisca Industries-produced, Taggart seam bituminous fuel and five tests each with physically and chemically cleaned Beulah-Zap lignite and a chemically cleaned Kemmerer subbituminous fuel. LRC-fueled heat engine testing conducted at the Energy and Environmental Research Center (EERC) has indicated that LRC fuels perform very well in short residence time heat engine combustion systems. Analyses of the emission and fly ash samples highlighted the superior burnout experienced by the LRC fuels as compared to the bituminous fuel even under a longer residence time profile for the bituminous fuel.

  11. Mineral matter transformations in a pressurized drop-tube furnace

    SciTech Connect

    Swanson, M.L.; Tibbetts, J.E.

    1992-12-31

    To meet the objectives of the program, a pressurized combustion vessel was built to allow the operating parameters of a direct-fired gas turbine combustor to be simulated. One goal in building this equipment was to design the gas turbine simulator as small as possible to reduce the quantity of test fuel needed, while not undersizing the combustor such that wall effects had a significant effect on the measured combustion performance. Based on computer modeling, a rich-lean, two-stage, nonslagging combustor was constructed to simulate a direct-fired gas turbine. This design was selected to maximize the information that could be obtained on the impact of low-rank coal`s unique properties on the gas turbine combustor, its turbomachinery, and the required hot-gas cleanup devices (such as high-temperature/high-pressure (HTHP) cyclones). Seventeen successful combustion tests using coal-water fuels were completed. These tests included seven tests with a commercially available Otisca Industries-produced, Taggart seam bituminous fuel and five tests each with physically and chemically cleaned Beulah-Zap lignite and a chemically cleaned Kemmerer subbituminous fuel. LRC-fueled heat engine testing conducted at the Energy and Environmental Research Center (EERC) has indicated that LRC fuels perform very well in short residence time heat engine combustion systems. Analyses of the emission and fly ash samples highlighted the superior burnout experienced by the LRC fuels as compared to the bituminous fuel even under a longer residence time profile for the bituminous fuel.

  12. Nucleate boiling pressure drop in an annulus: Book 2

    SciTech Connect

    Block, J.A.; Crowley, C.; Dolan, F.X.; Sam, R.G.; Stoedefalke, B.H.

    1992-11-01

    The application of the work described in this report is the production reactors at the Savannah River Site, and the context is nuclear reactor safety. The Loss of Coolant Accident (LOCA) scenario considered involves a double-ended break of a primary coolant pipe in the reactor. During a LOCA, the flow through portions of the reactor may reverse direction or be greatly reduced, depending upon the location of the break. The reduced flow rate of coolant (D{sub 2}O) through the fuel assembly channels of the reactor -- downflow in this situation -- can lead to boiling and to the potential for flow instabilities which may cause some of the fuel assembly channels to overheat and melt. That situation is to be avoided. The experimental approach is to provide a test annulus which simulates geometry, materials, and flow conditions in a Mark-22 fuel assembly (Coolant Channel 3) to the extent possible. The annulus has a full-scale geometry, and in fat uses SRL dummy hardware for the inner annulus wall in the ribbed geometry. The materials aluminum. The annulus is uniformly heated in the axial direction, but the circumferential heat flux can be varied to provide ``power tilt`` or asymmetric heating of the inner and outer annulus walls. The test facility uses H{sub 2}O rather than D{sub 2}O, but it includes the effects of dissolved helium gas present in the reactor. The key analysis approaches are: To compare the minima in the measured demand curves with analytical criteria, in particular the Saha-Zuber (1974) model; and to compare the pressure and temperature as a function of length in the annulus with an integral model for flow boiling in a heated channel. Nineteen test series and a total of 178 tests were performed. Testing addressed the effects of: Heat flux; pressure; helium gas; power tilt; ribs; asymmetric heat flux.

  13. Modeling of Leaching Filter Pressure Drop and Fouling Behavior

    SciTech Connect

    Rector, David R.; Stewart, Mark L.

    2010-04-01

    A new simulation capability has been developed for modeling the flow and thermal performance of chemical processes that involve multiphase, chemically-complex flows. This capability is applied to the ultrafiltration process which will be used in conjunction with caustic and/or oxidative leaching to concentrate high level waste in the Waste Treatment and Immobilization Plant (WTP) at the US DOE Hanford site. The separation of supernatant from undissolved solids is an important aspect of these processes. The design and likely operational performance of the proposed ultrafiltration system for the WTP facility have been called into question by external reviewers. Lattice methods are used to model both the pore scale filtration mechanisms in the filter material and the filter device scale performance. Simulation results are compared with data from experiments.

  14. Investigation of lean combustion stability and pressure drop in porous media burners

    NASA Astrophysics Data System (ADS)

    Sobhani, Sadaf; Haley, Bret; Bartz, David; Dunnmon, Jared; Sullivan, John; Ihme, Matthias

    2016-11-01

    The stability and thermal durability of combustion in porous media burners (PMBs) is examined experimentally and computationally. For this, two burner concepts are considered, which consist of different pore topologies, porous materials, and matrix arrangements. Long-term material durability tests at constant and cycled on-off conditions are performed, along with a characterization of combustion stability, pressure drop and pollutant emissions for a range of equivalence ratios and mass flow rates. Experimental thermocouple temperature measurements and pressure drop data are presented and compared to results obtained from one-dimensional volume-averaged simulations. Experimental and model results show reasonable agreement for temperature profiles and pressure drop evaluated using Ergun's equations. Enhanced flame stability is illustrated for burners with Yttria-stabilized Zirconia Alumina upstream and Silicon Carbide in the downstream combustion zone. Results reinforce concepts in PMB design and optimization, and demonstrate the potential of PMBs to overcome technological barriers associated with conventional free-flame combustion technologies.

  15. Pressure drop measurements on supercritical helium cooled cable in conduit conductors

    SciTech Connect

    Daugherty, M.A.; Huang, Y.; Van Sciver, S.W. . Applied Superconductivity Center)

    1989-03-01

    Forced flow cable-in-conduit conductors with large cooled surface areas provide excellent stability margins at the price of high frictional losses and large pumping power requirements. For extensive projects such as the International Thermonuclear Experimental Reactor design cooperation it is essential to know the pressure drops to be expected from different conductor geometries and operating conditions. To measure these pressure drops a flow loop was constructed to circulate supercritical helium through different conductors. The loop is surrounded by a 5 K radiation shield to allow for stable operation at the required temperatures. A coil heat exchanger immersed in a helium bath is used to remove the heat generated by the pump. Pressure drops are measured across 1 meter lengths of the conductors for various mass flow rates. Friction factor versus Reynolds number plots are used to correlate the data.

  16. Pressure drop measurements on supercritical helium cooled cable in conduit conductors

    SciTech Connect

    Daugherty, M.A.; Huang, Y.; Van Sciver, S.W.

    1988-01-01

    Forced flow cable-in-conduit conductors with large cooled surface areas provide excellent stability margins at the price of high frictional losses and large pumping power requirements. For extensive projects such as the International Thermonuclear Experimental Reactor design cooperation it is essential to know the pressure drops to be expected from different conductor geometries and operating conditions. To measure these pressure drops a flow loop was constructed to circulate supercritical helium through different conductors. The loop is surrounded by a 5 K radiation shield to allow for stable operation at the required temperatures. A coil heat exchanger immersed in a helium bath is used to remove the heat generated by the pump. Pressure drops are measured across 1 meter lengths of the conductors for various mass flow rates. Friction factor versus Reynolds number plots are used to correlate the data. 12 refs., 4 figs. 1 tab.

  17. Pressure drops during low void volume combustion retorting of oil shale

    SciTech Connect

    McLendon, T.R.

    1986-01-01

    Stacks of cut oil shale bricks were combustion retorted in a batch, pilot scale sized retort at low void volumes (overall voids ranged from 8.4% to 18.4%). Retort pressure drops increased during retorting at least one order of magnitude. The Ergun equation and Darcy's law have been used by several researchers and organizations as diagnostic tools on oil shale retorts. These equations were tested on the uniformly packed retort reported in this paper to evaluate how well the equations represented the experimental conditions. Use of the Ergun equation to estimate the average particle size from retort pressure drops gave answers that were only approximately correct. Calculation of retort pressure drops from Darcy's law during retorting at low void volumes will probably give answers that are several times too small. Thermal expansion of the shale during retorting decreases retort permeability greatly and calculation of the decreased permeability is not possible at the present level of technology.

  18. An improved correlation of the pressure drop in stenotic vessels using Lorentz's reciprocal theorem

    NASA Astrophysics Data System (ADS)

    Ji, Chang-Jin; Sugiyama, Kazuyasu; Noda, Shigeho; He, Ying; Himeno, Ryutaro

    2015-02-01

    A mathematical model of the human cardiovascular system in conjunction with an accurate lumped model for a stenosis can provide better insights into the pressure wave propagation at pathological conditions. In this study, a theoretical relation between pressure drop and flow rate based on Lorentz's reciprocal theorem is derived, which offers an identity to describe the relevance of the geometry and the convective momentum transport to the drag force. A voxel-based simulator V-FLOW VOF3D, where the vessel geometry is expressed by using volume of fluid (VOF) functions, is employed to find the flow distribution in an idealized stenosis vessel and the identity was validated numerically. It is revealed from the correlation that the pressure drop of NS flow in a stenosis vessel can be decomposed into a linear term caused by Stokes flow with the same boundary conditions, and two nonlinear terms. Furthermore, the linear term for the pressure drop of Stokes flow can be summarized as a correlation by using a modified equation of lubrication theory, which gives favorable results compared to the numerical ones. The contribution of the nonlinear terms to the pressure drop was analyzed numerically, and it is found that geometric shape and momentum transport are the primary factors for the enhancement of drag force. This work paves a way to simulate the blood flow and pressure propagation under different stenosis conditions by using 1D mathematical model.

  19. Low pressure drop filtration of airborne molecular organic contaminants using open-channel networks

    NASA Astrophysics Data System (ADS)

    Dallas, Andrew J.; Joriman, Jon; Ding, Lefei; Weineck, Gerald; Seguin, Kevin

    2007-03-01

    Airborne molecular contamination (AMC) continues to play a very decisive role in the performance of many microelectronic devices and manufacturing processes. Besides airborne acids and bases, airborne organic contaminants such as 1-methyl-2-pyrrolidinone (NMP), hexamethyldisiloxane (HMDSO), trimethylsilanol (TMS), perfluoroalkylamines and condensables are of primary concern in these applications. Currently, the state of the filtration industry is such that optimum filter life and removal efficiency for organics is offered by granular carbon filter beds. However, the attributes that make packed beds of activated carbon extremely efficient also impart issues related to elevated filter weight and pressure drop. Most of the lower pressure drop AMC filters currently offered are quite expensive and are simply pleated combinations of various adsorptive and reactive media. On the other hand, low pressure drop filters, such as those designed as open-channel networks (OCN's), offer good filter life and removal efficiency with the additional benefits of significant reductions in overall filter weight and pressure drop. Equally important for many applications, the OCN filters can reconstruct the airflow so as to enhance the operation of a tool or process. For tool mount assemblies and fan filter units (FFUs) this can result in reduced fan and blower speeds, which subsequently can provide reduced vibration and energy costs. Additionally, these low pressure drop designs can provide a cost effective way of effectively removing AMC in full fab (or HVAC) filtration applications without significantly affecting air-handling requirements. Herein, we will present a new generation of low pressure drop OCN filters designed for the removal of airborne organics in a wide range of applications.

  20. Use of the isopycnic plots in designing operations of supercritical fluid chromatography: IV. Pressure and density drops along columns.

    PubMed

    Tarafder, Abhijit; Kaczmarski, Krzysztof; Ranger, Megan; Poe, Donald P; Guiochon, Georges

    2012-05-18

    The pressure- and the density-drops along a chromatographic column eluted with supercritical fluid carbon dioxide were mapped as a function of the outlet column pressure and the temperature on the P-T diagram of neat CO(2). At low densities, the viscosity of CO(2) is low, which is expected to result into a low pressure drop along the column. However, at these low densities, the volumetric flow rates of the mobile phase at constant mass flow rates are high, which might result into a high pressure drop along the column. These conflicting effects of an adjustment in the mobile phase density on the pressure drop of the mobile phase along the column makes it nearly impossible to develop a simple intuitive understanding of the relationships between the net pressure drops and the operating temperatures and pressures. The development of a similar understanding of their relationships with the density drop along the column is even more complex, because this density drop depends also on the compressibility of the mobile phase, itself a function of the operating pressures and temperatures. Numerical calculations of the pressure and density drops along columns packed with particles of different sizes, under different operating conditions (temperature, outlet pressure, and flow rate), provide important insights regarding the extent of the pressure and density drops under these operating conditions. Copyright © 2012 Elsevier B.V. All rights reserved.

  1. Fundamental study of transpiration cooling. [pressure drop and heat transfer data from porous metals

    NASA Technical Reports Server (NTRS)

    Koh, J. C. Y.; Dutton, J. L.; Benson, B. A.

    1973-01-01

    Isothermal and non-isothermal pressure drop data and heat transfer data generated on porous 304L stainless steel wire forms, sintered spherical stainless steel powder, and sintered spherical OFHC copper powder are reported and correlated. Pressure drop data was collected over a temperature range from 500 R to 2000 R and heat transfer data collected over a heat flux range from 5 to 15 BTU/in2/sec. It was found that flow data could be correlated independently of transpirant temperature and type (i.e., H2, N2). It was also found that no simple relation between heat transfer coefficient and specimen porosity was obtainable.

  2. Prediction of pressure drops accompanying the evaporation of refrigerants inside horizontal tubes. Technical memo

    SciTech Connect

    Stoneham, H.G.; Saluja, S.N.; Dunn, A.

    1980-01-01

    Four of the more widely used correlations for the prediction of pressure drops were compared with published experimental data using statistical techniques. None of the correlations examined were found to be suitably accurate over the range of conditions normally encountered in direct expansion evaporators. A new correlation was developed and is presented here, that can be used with an acceptable degree of accuracy by the design engineer. The correlation is presented in a form that can be easily written into a program for solution on a programmable calculator leading to quick and accurate evaluation of the pressure drop that accompanies a refrigerant evaporatoring inside a horontal tube evaporator.

  3. Nucleate boiling pressure drop in an annulus: Book 4

    SciTech Connect

    Block, J.A.; Crowley, C.; Dolan, F.X.; Sam, R.G.; Stoedefalke, B.H.

    1992-11-01

    The application of the work described in this report is the production reactors at the Savannah River Site, and the context is nuclear reactor safety. The Loss of Coolant Accident (LOCA) scenario considered involves a double-ended break of a primary coolant pipe in the reactor. During a LOCA, the flow through portions of the reactor may reverse direction or be greatly reduced, depending upon the location of the break. The reduced flow rate of coolant (D{sub 2}O) through the fuel assembly channels of the reactor -- downflow in this situation -- can lead to boiling and to the potential for flow instabilities which may cause some of the fuel assembly channels to overheat and melt. That situation is to be avoided. The experimental approach is to provide a test annulus which simulates geometry, materials, and flow conditions in a Mark-22 fuel assembly (Coolant Channel 3) to the extent possible. The annulus has a full-scale geometry, and in fat uses SRL dummy hardware for the inner annulus wall in the ribbed geometry. The materials aluminum. The annulus is uniformly heated in the axial direction, but the circumferential heat flux can be varied to provide ``power tilt`` or asymmetric heating of the inner and outer annulus walls. The test facility uses H{sub 2}O rather than D{sub 2}O, but it includes the effects of dissolved helium gas present in the reactor. The key analysis approaches are: To compare the minima in the measured demand curves with analytical criteria, in particular the Saha-Zuber (1974) model; and to compare the pressure and temperature as a function of length in the annulus with an integral model for flow boiling in a heated channel. This document consists of data plots and summary files of temperature measurements.

  4. Nucleate boiling pressure drop in an annulus: Book 8

    SciTech Connect

    Not Available

    1992-11-01

    The application of the work described in this report is the production reactors at the Savannah River Site, and the context is nuclear reactor safety. The Loss of Coolant Accident (LOCA) scenario considered involves a double-ended break of a primary coolant pipe in the reactor. During a LOCA, the flow through portions of the reactor may reverse direction or be greatly reduced, depending upon the location of the break. The reduced flow rate of coolant (D{sub 2}O) through the fuel assembly channels of the reactor -- downflow in this situation -- can lead to boiling and to the potential for flow instabilities which may cause some of the fuel assembly channels to overheat and melt. That situation is to be avoided. The experimental approach is to provide a test annulus which simulates geometry, materials, and flow conditions in a Mark-22 fuel assembly (Coolant Channel 3) to the extent possible. The annulus has a full-scale geometry, and in fat uses SRL dummy hardware for the inner annulus wall in the ribbed geometry. The materials aluminum. The annulus is uniformly heated in the axial direction, but the circumferential heat flux can be varied to provide ``power tilt`` or asymmetric heating of the inner and outer annulus walls. The test facility uses H{sub 2}O rather than D{sub 2}O, but it includes the effects of dissolved helium gas present in the reactor. The key analysis approaches are: To compare the minima in the measured demand curves with analytical criteria, in particular the Saha-Zuber (1974) model; and to compare the pressure and temperature as a function of length in the annulus with an integral model for flow boiling in a heated channel. This document consists of tables of temperature measurements.

  5. Nucleate boiling pressure drop in an annulus: Book 3

    SciTech Connect

    Block, J.A.; Crowley, C.; Dolan, F.X.; Sam, R.G.; Stoedefalke, B.H.

    1992-11-01

    The application of the work described in this report is the production reactors at the Savannah River Site, and the context is nuclear reactor safety. The Loss of Coolant Accident (LOCA) scenario considered involves a double-ended break of a primary coolant pipe in the reactor. During a LOCA, the flow through portions of the reactor may reverse direction or be greatly reduced, depending upon the location of the break. The reduced flow rate of coolant (D{sub 2}O) through the fuel assembly channels of the reactor -- downflow in this situation -- can lead to boiling and to the potential for flow instabilities which may cause some of the fuel assembly channels to overheat and melt. That situation is to be avoided. The experimental approach is to provide a test annulus which simulates geometry, materials, and flow conditions in a Mark-22 fuel assembly (Coolant Channel 3) to the extent possible. The annulus has a full-scale geometry, and in fat uses SRL dummy hardware for the inner annulus wall in the ribbed geometry. The materials aluminum. The annulus is uniformly heated in the axial direction, but the circumferential heat flux can be varied to provide ``power tilt`` or asymmetric heating of the inner and outer annulus walls. The test facility uses H{sub 2}O rather than D{sub 2}O, but it includes the effects of dissolved helium gas present in the reactor. The key analysis approaches are: To compare the minima in the measured demand curves with analytical criteria, in particular the Saha-Zuber (1974) model; and to compare the pressure and temperature as a function of length in the annulus with an integral model for flow boiling in a heated channel. This document consists of data plots and summary files of temperature measurements.

  6. An experimental investigation of pressure drop in forced-convection condensation and evaporation of oil-refrigerant mixtures

    SciTech Connect

    Tichy, J.A.; Duque-Rivera, J.; Macken, N.A.; Duval, W.M.B.

    1986-01-01

    Experimental measurements of pressure drop have been made for forced-convection evaporation and condensation of oil-refrigerant (R-12) mixtures inside a horizontal tube. Data were compared to a wide range of frictional pressure drop and void fraction relationships. The best representations for the oil-free data were then modified to better correlate both oil-free and oil-refrigerant results. For condensation, a modification of the prediction given by the Lockhart-Martinelli relation for frictional pressure drop and the homogeneous void fraction model is presented. For evaporation, the prediction given by the Dukler II frictional pressure-drop correlation and the homogeneous void fraction is modified. These relationships predict the pressure drop for 85% of the data to within +- 35%. The added oil increased the pressure drop 2% to 6% for condensation and 63% to 86% for evaporation.

  7. Comparison of Pressure Drop between Calculation and Experiment for a Two-phase Carbon Dioxide Loop

    NASA Astrophysics Data System (ADS)

    Mo, D.-C.; Xiao, W.-J.; Huang, Z.-C.; Sun, X.-H.; Chen, Y.; Lu, S.-S.; Li, T.-X.; Qi, X.-M.; Wang, Z.-X.; Pauw, A.; Bsibsi, M.; Gargiulo, C.; van Es, J.; He, Z.-H.

    2008-09-01

    Tracker thermal control system (TTCS) is an active-pumped two-phase carbon dioxide cooling loop, which is developed for the Alpha Magnetic Spectrometer tracker front-end electronics. The maintenance-free centrifugal pump is a critical component in the design mainly due to the limited pressure head with small mass flows. Therefore a correct pressure drop is required to predict the pressure drop for dynamic modeling. As the normal operational temperature of the carbon dioxide in the TTCS is from - 15°C to +15°C, which is very close to its critical point, 33°C, and many two-phase pressure drop correlations may not fit well here. In this paper, we attempt to correlate the pressure drops between the calculations and the experiment of the two-phase CO2 loop. The comparison will focus on one evaporator. Here, the Lockhart/Martinelli correlation is recorrelated with different definition C value for CO2 according to the test results. Comparison shows that, the new correlation can fit the test results well.

  8. A steady state pressure drop model for screen channel liquid acquisition devices

    NASA Astrophysics Data System (ADS)

    Hartwig, J. W.; Darr, S. R.; McQuillen, J. B.; Rame, E.; Chato, D. J.

    2014-11-01

    This paper presents the derivation of a simplified one dimensional (1D) steady state pressure drop model for flow through a porous liquid acquisition device (LAD) inside a cryogenic propellant tank. Experimental data is also presented from cryogenic LAD tests in liquid hydrogen (LH2) and liquid oxygen (LOX) to compare against the simplified model and to validate the model at cryogenic temperatures. The purpose of the experiments was to identify the various pressure drop contributions in the analytical model which govern LAD channel behavior during dynamic, steady state outflow. LH2 pipe flow of LAD screen samples measured the second order flow-through-screen (FTS) pressure drop, horizontal LOX LAD outflow tests determined the relative magnitude of the third order frictional and dynamic losses within the channel, while LH2 inverted vertical outflow tests determined the magnitude of the first order hydrostatic pressure loss and validity of the full 1D model. When compared to room temperature predictions, the FTS pressure drop is shown to be temperature dependent, with a significant increase in flow resistance at LH2 temperatures. Model predictions of frictional and dynamic losses down the channel compare qualitatively with LOX LADs data. Meanwhile, the 1D model predicted breakdown points track the trends in the LH2 inverted outflow experimental results, with discrepancies being due to a non-uniform injection velocity across the LAD screen not accounted for in the model.

  9. Pressure drop and arterial compliance - Two arterial parameters in one measurement.

    PubMed

    Rotman, Oren M; Zaretsky, Uri; Shitzer, Avraham; Einav, Shmuel

    2017-01-04

    Coronary artery pressure-drop and distensibility (compliance) are two major, seemingly unrelated, parameters in the cardiovascular clinical setting, which are indicative of coronary arteries patency and atherosclerosis severity. While pressure drop is related to flow, and therefore serves as a functional indicator of a stenosis severity, the arterial distensibility is indicative of the arterial stiffness, and hence the arterial wall composition. In the present study, we hypothesized that local pressure drops are dependent on the arterial distensibility, and hence can provide information on both indices. The clinical significance is that a single measurement of pressure drop could potentially provide both functional and bio-mechanical metrics of lesions, and thus assist in real-time decision making prior to stenting. The goal of the current study was to set the basis for understanding this relationship, and define the accuracy and sensitivity required from the pressure measurement system. The investigation was performed using numerical fluid-structure interaction (FSI) simulations, validated experimentally using our high accuracy differential pressure measurement system. Simplified silicone mock coronary arteries with zero to intermediate size stenoses were used, and various combinations of arterial distensibility, diameter, and flow rate were simulated. Results of hyperemic flow cases were also compared to fractional flow reserve (FFR). The results indicate the potential clinical superiority of a high accuracy pressure drop-based parameter over FFR, by: (i) being more lesion-specific, (ii) the possibility to circumvent the FFR dependency on pharmacologically-induced hyperemia, and, (iii) by providing both functional and biomechanical lesion-specific information.

  10. Intraocular pressure in cats is lowered by drops of hornet venom.

    PubMed

    Kam, J; Waron, M; Barishak, Y R; Schachner, E; Ishay, J S

    1989-01-01

    1. Nine cats were given an intravenous injection of the Oriental hornet (Vespa orientalis, Vespinae; Hymenoptera) venom sac extract (VSE) and seven cats had the same VSE administered as eye drops. 2. When injected intravenously, the hornet VSE decreased the intraocular pressure in both eyes sharply during the first 20 min and with a slower rate later on until the end of the 3 hr experiment. The intraocular pressure dropped to zero in some cases. 3. VSE eye drops decreased the intraocular pressure only in the treated eye, while in the second eye (left as a control) the intraocular pressure remained the same throughout the experiment. 4. The decrease in the intraocular pressure was sharp during the first 20 min and slowed down afterwards until the end of the experiment. 5. The intraocular pressure did not reduce to zero. 6. This study shows that the active components of the hornet venom which caused a decrease in the intraocular pressure can cross the cornea and exert a hypotensive effect in the eye.

  11. Testing of a 4 K to 2 K heat exchanger with an intermediate pressure drop

    SciTech Connect

    Knudsen, Peter N.; Ganni, Venkatarao

    2015-12-01

    Most large sub-atmospheric helium refrigeration systems incorporate a heat exchanger at the load, or in the distribution system, to counter-flow the sub-atmospheric return with the super-critical or liquid supply. A significant process improvement is theoretically obtainable by handling the exergy loss across the Joule-Thompson throttling valve supplying the flow to the load in a simple but different manner. As briefly outlined in previous publications, the exergy loss can be minimized by allowing the supply flow pressure to decrease to a sub-atmospheric pressure concurrent with heat exchange flow from the load. One practical implementation is to sub-divide the supply flow pressure drop between two heat exchanger sections, incorporating an intermediate pressure drop. Such a test is being performed at Jefferson Lab's Cryogenic Test Facility (CTF). This paper will briefly discuss the theory, practical implementation and test results and analysis obtained to date.

  12. Evaluation of membrane oxygenators and reservoirs in terms of capturing gaseous microemboli and pressure drops.

    PubMed

    Guan, Yulong; Palanzo, David; Kunselman, Allen; Undar, Akif

    2009-11-01

    An increasing amount of evidence points to cerebral embolization during cardiopulmonary bypass (CPB) as the principal etiologic factor of neurologic complications. In this study, the capability of capturing and classification of gaseous emboli and pressure drop of three different membrane oxygenators (Sorin Apex, Terumo Capiox SX25, Maquet QUADROX) were measured in a simulated adult model of CPB using a novel ultrasound detection and classification quantifier system. The circuit was primed with 1000 mL heparinized human packed red blood cells and 1000 mL lactated Ringer's solution (total volume 2000 mL, corrected hematocrit 26-28%). After the injection of 5 mL air into the venous line, an Emboli Detection and Classification Quantifier was used to simultaneously record microemboli counts at post-pump, post-oxygenator, and post-arterial filter sites. Trials were conducted at normothermic (35 degrees C) and hypothermic (25 degrees C) conditions. Pre-oxygenator and post-oxygenator pressure were recorded in real time and pressure drop was calculated. Maquet QUADROX membrane oxygenator has the lowest pressure drops compared to the other two oxygenators (P < 0.001). The comparison among the three oxygenators indicated better capability of capturing gaseous emboli with the Maquet QUADROX and Terumo Capiox SX25 membrane oxygenator and more emboli may pass through the Sorin Apex membrane oxygenator. Microemboli counts uniformly increased with hypothermic perfusion (25 degrees C). Different types of oxygenators and reservoirs have different capability of capturing gaseous emboli and transmembrane pressure drop. Based on this investigation, Maquet QUADROX membrane oxygenator has the lowest pressure drop and better capability for capturing gaseous microemboli.

  13. Instant controlled pressure drop extraction of lavandin essential oils: fundamentals and experimental studies.

    PubMed

    Besombes, Colette; Berka-Zougali, Baya; Allaf, Karim

    2010-10-29

    Détente Instantanée contrôlée (DIC), French for Instant Controlled Pressure Drop, was performed on laboratory apparatus as well as on a pilot plant for proving its feasibility, and identifying the optimized processing conditions and recognizing the energy consumption and the quantity of water used for such an operation. GC-MS and SPME analysis of the extracts and residue material were carried out to assess the extracts and solid residues. The lavandin essential oils obtained by using the new DIC extraction process was studied, modeled and quantitatively and qualitatively compared to the conventional hydrodistillation method. The most important differences between the two essential oils were reflected in the yields, with 4.25 as against 2.3 g EO/100 g of raw matter, and in the extraction time, with 480 s as against some hours for respectively the DIC and the hydrodistillation operations. These differences have been previewed through the fundamental analysis. They can normally explain the great decreasing of energy consumption to be 662 kWh/t of raw material. The amount of water to be added was about 42 kg water/t of raw material. Copyright © 2010 Elsevier B.V. All rights reserved.

  14. Pressure drop measurements on cable-in-conduit conductors of various geometries

    SciTech Connect

    Daugherty, M.A.; Van Sciver, S.W. . Applied Superconductivity Center)

    1991-03-01

    This paper measures the pressure drop on various cable-in-conduit conductors with different void fractions, number of strands and flow areas. To carry out these measurements, supercritical helium is circulated through a loop containing several conductor sections instrumented with cold pressure transducers. A cold centrifugal pump is used to force the helium through the loop at flow rates of up to several grams per second. The modular design of the flow loop allows for relatively easy insertion of different test sections.

  15. Determining Seed Cotton Mass Flow Rate by Pressure Drop Across a Blowbox: Gin Testing

    USDA-ARS?s Scientific Manuscript database

    Accurate measurement of the mass flow rate of seed cotton is needed for control and monitoring purposes in gins. A system was developed that accurately predicted mass flow rate based on the static pressure drop measured across the blowbox and the air velocity and temperature entering the blowbox. Ho...

  16. New Results in Two-Phase Pressure Drop Calculations at Reduced Gravity Conditions

    NASA Astrophysics Data System (ADS)

    Braisted, Jon; Kurwitz, Cable; Best, Frederick

    2004-02-01

    The mass, power, and volume energy savings of two-phase systems for future spacecraft creates many advantages over current single-phase systems. Current models of two-phase phenomena such as pressure drop, void fraction, and flow regime prediction are still not well defined for space applications. Commercially available two-phase modeling software has been developed for a large range of acceleration fields including reduced-gravity conditions. Recently, a two-phase experiment has been flown to expand the two-phase database. A model of the experiment was created in the software to determine how well the software could predict the pressure drop observed in the experiment. Of the simulations conducted, the computer model shows good agreement of the pressure drop in the experiment to within 30%. However, the software does begin to over-predict pressure drop in certain regions of a flow regime map indicating that some models used in the software package for reduced-gravity modeling need improvement.

  17. An experimental study of heat transfer and pressure drop characteristics of divergent wavy minichannels using nanofluids

    NASA Astrophysics Data System (ADS)

    Dominic, A.; Sarangan, J.; Suresh, S.; Devahdhanush, V. S.

    2017-03-01

    An experimental investigation was conducted to study the heat transfer and pressure drop characteristics of an array of wavy divergent minichannels and the results were compared with wavy minichannels with constant cross-section. The experiment was conducted in hydro dynamically developed and thermally developing laminar and transient regimes. The minichannel heat sink array consisted of 15 rectangular channels machined on a 30 × 30 mm2 and 11 mm thick Aluminium substrate. Each minichannel was of 0.9 mm width, 1.8 mm pitch and the depth was varied from 1.3 mm at entrance to 3.3 mm at exit for the divergent channels. DI water and 0.5 and 0.8 % concentrations of Al2O3/water nanofluid were used as working fluids. The Reynolds number was varied from 700 to 3300 and the heat flux was maintained at 45 kW/m2. The heat transfer and pressure drop of these minichannels were analyzed based on the experimental results obtained. It was observed that the heat transfer performance of divergent wavy minichannels was 9 % higher and the pressure drop was 30-38 % lesser than that of the wavy minichannels with constant cross-section, in the laminar regime. Hence, divergent channel flows can be considered one of the better ways to reduce pressure drop. The performance factor of divergent wavy minichannels was 115-126 % for water and 110-113 % for nanofluids.

  18. Determining Seed Cotton Mass Flow Rate by Pressure Drop Across the Blowbox: Gin Testing

    USDA-ARS?s Scientific Manuscript database

    Accurate measurement of the mass flow rate of seed cotton is needed for control and monitoring purposes in gins. A system was developed that accurately predicted mass flow rate based on the static pressure drop measured across the blowbox and the air velocity and temperature entering the blowbox usi...

  19. Pressure drop and gas distribution in compost based biofilters: medium mixing and composition effects.

    PubMed

    Morgan-Sagastume, J M; Revah, S; Noyola, A

    2003-07-01

    The pressure drop and gas distribution in four different filter media for compost biofilters were studied as a function of three superficial loading rates of moist air and by carrying out the filter medium homogenization by mixing. The filter media used were compost, compost with cane bagasse, lava rock and aerobic sludge previously dried to 60% of water content. The pressure drop increased when lava rock and cane bagasse were used as bulking agents. The same trend was observed when water was added to the filter medium. Pressure drop tended to decrease with time as flow channels were formed inthe filter media. Tracer studies were carried out to quantify the gas distribution and the effect of channel formation. For the biofilters submitted to an airflow of 10, 40 and 70 l min(-1), an average normalized time of 0.96, 0.89 and 0.82, respectively were obtained. The results showed that channel formation was increased as the superficial loading rate was also increased. An operational practice that this work proposes and evaluates to improve gas distribution and medium moisture control is to carry out intermittent medium mixing. The medium moisture and void volume achieved under mixing condition were around 50% and 0.40, respectively with an average constant pressure drop of 11, 45 and 78 cm of water m(-1) for air velocities of 75, 300 and 525 m h(-1).

  20. A computer code for calculating subcooled boiling pressure drop in forced convective tube flows

    NASA Astrophysics Data System (ADS)

    Wong, Christopher F.

    1988-12-01

    A calculation procedure, embodied in a computer code, was developed to calculate the convective subcooled boiling (SCB) pressure drop of water flowing in small diameter vertical or horizontal tubes under the condition of high heat fluxes. The present investigation is an extension of previous work performed by C. T. Kline in 1985. The computer code, presented then and now, numerically integrates the single-phase and separated-flow-model pressure drop equations from the inlet to the outlet of a heated tube. Efforts in this study were concentrated on identifying weaknesses in Kline's best code version and investigating his recommendations for future work. The calculation procedures for each flow regime in the tube were modified to give better overall results. New work focused primarily on the partially-developed boiling (PDB) and fully-developed boiling (FDB) regimes. The pressure drop predictions from each code version were compared to the experimental pressure drop results from the experimental investigations of Dormer/Bergles, Owens/Schrock, and Reynolds.

  1. Pressure Drop and Heat Transfer of Water Flowing Shell-Side of Multitube Heat Exchangers

    NASA Astrophysics Data System (ADS)

    Ohashi, Yukio; Hashizume, Kenichi

    Experimental studies on heat transfer augmentation in water-flowing shell sides of counter flow multitube exchangers are presented. Various kinds of augmented tube bundles have been examined to obtain the characteristics of pressure drop and heat transfer. Data for a smooth tube bundle were a little different from those for the tube side. The pressure drop in the shell side depended on Re-0.4 and deviated from the tube side pressure drop to within +30%, while the shell side heat transfer coefficient depended on Re0.8 but about 35%. larger than that of the tube side. Furthermore the augmented tube bundles have been evaluated and compared using 21 evaluation criteria. Enhanced tube bundles, low-finned tube bundles and those with twisted tapes inserted had especially good performances. The ratios of increase in heat transfer were larger than those in pressure drop. In case of low-finned tube bundles, there seem to exist an optimum fin-pitch and an optimum relation between the fin-pitch and the pitch of twisted tapes inserted.

  2. Impact of flow regime on pressure drop increase and biomass accumulation and morphology in membrane systems.

    PubMed

    Vrouwenvelder, J S; Buiter, J; Riviere, M; van der Meer, W G J; van Loosdrecht, M C M; Kruithof, J C

    2010-02-01

    Biomass accumulation and pressure drop development have been studied in membrane fouling simulators at different flow regimes. At linear flow velocities as applied in practice in spiral wound nanofiltration (NF) and reverse osmosis (RO) membranes, voluminous and filamentous biofilm structures developed in the feed spacer channel, causing a significant increase in feed channel pressure drop. Elevated shear by both single phase flow (water) and two phase flow (water with air sparging: bubble flow) caused biofilm filaments and a pressure drop increase. The amount of accumulated biomass was independent of the applied shear, depending on the substrate loading rate (product of substrate concentration and linear flow velocity) only. The biofilm streamers oscillated in the passing water. Bubble flow resulted in a more compact and less filamentous biofilm structure than single phase flow, causing a much lower pressure drop increase. The biofilm grown under low shear conditions was more easy to remove during water flushing compared to a biofilm grown under high shear. To control biofouling, biofilm structure may be adjusted using biofilm morphology engineering combined with biomass removal from membrane elements by periodic reverse flushing using modified feed spacers. Potential long and short term consequences of flow regimes on biofilm development are discussed. Flow regimes manipulate biofilm morphology affecting membrane performance, enabling new approaches to control biofouling. (c) 2009 Elsevier Ltd. All rights reserved.

  3. Pressure drop of slush nitrogen flow in converging-diverging pipes and corrugated pipes

    NASA Astrophysics Data System (ADS)

    Ohira, Katsuhide; Okuyama, Jun; Nakagomi, Kei; Takahashi, Koichi

    2012-12-01

    Cryogenic slush fluids such as slush hydrogen and slush nitrogen are solid-liquid, two-phase fluids. As a functional thermal fluid, there are high expectations for use of slush fluids in various applications such as fuels for spacecraft engines, clean-energy fuels to improve the efficiency of transportation and storage, and as refrigerants for high-temperature superconducting equipment. Experimental flow tests were performed using slush nitrogen to elucidate pressure-drop characteristics of converging-diverging (C-D) pipes and corrugated pipes. In experimental results regarding pressure drop in two different types of C-D Pipes, i.e., a long-throated pipe and a short-throated pipe, each having an inner diameter of 15 mm, pressure drop for slush nitrogen in the long-throated pipe at a flow velocity of over 1.3 m/s increased by a maximum of 50-60% as compared to that for liquid nitrogen, while the increase was about 4 times as compared to slush nitrogen in the short-throated pipe. At a flow velocity of over 1.5 m/s in the short-throated pipe, pressure drop reduction became apparent, and it was confirmed that the decrease in pressure drop compared to liquid nitrogen was a maximum of 40-50%. In the case of two different types of corrugated pipes with an inner diameter of either 12 mm or 15 mm, a pressure-drop reduction was confirmed at a flow velocity of over 2 m/s, and reached a maximum value of 37% at 30 wt.% compared to liquid nitrogen. The greater the solid fractions, the smaller the pipe friction factor became, and the pipe friction factor at the same solid fraction showed a constant value regardless of the Reynolds number. From the observation of the solid particles' behavior using a high-speed video camera and the PIV method, the pressure-drop reduction mechanisms for both C-D and corrugated pipes were demonstrated.

  4. In vivo validation of the in silico predicted pressure drop across an arteriovenous fistula.

    PubMed

    Browne, Leonard D; Griffin, Philip; Bashar, Khalid; Walsh, Stewart R; Kavanagh, Eamon G; Walsh, Michael T

    2015-06-01

    The creation of an arteriovenous fistula offers a unique example of vascular remodelling and adaption. Yet, the specific factors which elicit remodelling events which determine successful maturation or failure have not been unambiguously determined. Computational fluid dynamic (CFD) simulations are increasingly been employed to investigate the interaction between local hemodynamics and remodelling and can potentially be used to assist in clinical risk assessment of maturation or failure. However, these simulations are inextricably linked to their prescribed boundary conditions and are reliant on in vivo measurements of flow and pressure to ensure their validity. The study compares in vivo measurements of the pressure distribution across arteriovenous fistulae against a representative numerical model. The results of the study indicate relative agreement (error ≈ 8-10%) between the in vivo and CFD prediction of the mean pressure drop across the AVFs. The large pressure drop across the AVFs coincided with a palpable thrill (perivascular vibration) in vivo and fluctuations were observed in the numerical pressure drop signal due to flow instabilities arising at the anastomosis. This study provides a benchmark of the pressure distribution within an AVF and validates that CFD solutions are capable of replicating the abnormal physiological flow conditions induced by fistula creation.

  5. Pressure drop reduction and heat transfer deterioration of slush nitrogen in triangular and circular pipe flows

    NASA Astrophysics Data System (ADS)

    Ohira, Katsuhide; Kurose, Kizuku; Okuyama, Jun; Saito, Yutaro; Takahashi, Koichi

    2017-01-01

    Slush fluids such as slush hydrogen and slush nitrogen are characterized by superior properties as functional thermal fluids due to their density and heat of fusion. In addition to allowing efficient hydrogen transport and storage, slush hydrogen can serve as a refrigerant for high-temperature superconducting (HTS) equipment using MgB2, with the potential for synergistic effects. In this study, pressure drop reduction and heat transfer deterioration experiments were performed on slush nitrogen flowing in a horizontal triangular pipe with sides of 20 mm under the conditions of three different cross-sectional orientations. Experimental conditions consisted of flow velocity (0.3-4.2 m/s), solid fraction (0-25 wt.%), and heat flux (0, 10, and 20 kW/m2). Pressure drop reduction became apparent at flow velocities exceeding about 1.3-1.8 m/s, representing a maximum amount of reduction of 16-19% in comparison with liquid nitrogen, regardless of heating. Heat transfer deterioration was seen at flow velocities of over 1.2-1.8 m/s, for a maximum amount of deterioration of 13-16%. The authors of the current study compared the results for pressure drop reduction and heat transfer deterioration in triangular pipe with those obtained previously for circular and square pipes, clarifying differences in flow and heat transfer properties. Also, a correlation equation was obtained between the slush Reynolds number and the pipe friction factor, which is important in the estimation of pressure drop in unheated triangular pipe. Furthermore, a second correlation equation was derived between the modified slush Reynolds number and the pipe friction factor, enabling the integrated prediction of pressure drop in both unheated triangular and circular pipes.

  6. Calculation of pressure drop in the developmental stages of the medaka fish heart and microvasculature

    NASA Astrophysics Data System (ADS)

    Chakraborty, Sreyashi; Vlachos, Pavlos

    2016-11-01

    Peristaltic contraction of the developing medaka fish heart produces temporally and spatially varying pressure drop across the atrioventricular (AV) canal. Blood flowing through the tail vessels experience a slug flow across the developmental stages. We have performed a series of live imaging experiments over 14 days post fertilization (dpf) of the medaka fish egg and cross-correlated the red blood cell (RBC) pattern intensities to obtain the two-dimensional velocity fields. Subsequently we have calculated the pressure field by integrating the pressure gradient in the momentum equation. Our calculations show that the pressure drop across the AV canal increases from 0.8mm Hg during 3dpf to 2.8 mm Hg during 14dpf. We have calculated the time-varying wall shear stress for the blood vessels by assuming a spatially constant velocity magnitude in each vessel. The calculated wall shear stress matches the wall shear stress sensed by human endothelial cells (10-12 dyne/sq. cm). The pressure drop per unit length of the vessel is obtained by doing a control volume analysis of flow in the caudal arteries and veins. The current results can be extended to investigate the effect of the fluid dynamic parameters on the vascular and cardiac morphogenesis.

  7. Blood Pressure Drop Prediction by using HRV Measurements in Orthostatic Hypotension.

    PubMed

    Sannino, Giovanna; Melillo, Paolo; Stranges, Saverio; De Pietro, Giuseppe; Pecchia, Leandro

    2015-11-01

    Orthostatic Hypotension is defined as a reduction of systolic and diastolic blood pressure within 3 minutes of standing, and may cause dizziness and loss of balance. Orthostatic Hypotension has been considered an important risk factor for falls since 1960. This paper presents a model to predict the systolic blood pressure drop due to orthostatic hypotension, relying on heart rate variability measurements extracted from 5 minute ECGs recorded before standing. This model was developed and validated with the leave-one-out cross-validation technique involving 10 healthy subjects, and finally tested with an additional 5 healthy subjects, whose data were not used during the training and cross-validation process. The results show that the model predicts correctly the systolic blood pressure drop in 80 % of all experiments, with an error rate below the measurement error of a sphygmomanometer digital device.

  8. Pressure drop and temperature rise in He II flow in round tubes, Venturi flowmeters and valves

    NASA Technical Reports Server (NTRS)

    Walstrom, P. L.; Maddocks, J. R.

    1988-01-01

    Pressure drops in highly turbulent He II flow were measured in round tubes, valves, and Venturi flowmeters. Results are in good agreement with single-phase flow correlations for classical fluids. The temperature rise in flow in a round tube was measured, and found to agree well with predictions for isenthalpic expansion. Cavitation was observed in the venturis under conditions of low back pressure and high flow rate. Metastable superheating of the helium at the venturi throat was observed before the helium made a transition to saturation pressure.

  9. Effects of phosphoric acid sprayed into an incinerator furnace on the flue gas pressure drop at fabric filters.

    PubMed

    Takahashi, Shigetoshi; Hwang, In-Hee; Matsuto, Toshihiko

    2016-06-01

    Fabric filters are widely used to remove dust from flue gas generated by waste incineration. However, a pressure drop occurs at the filters, caused by growth of a dust layer on the filter fabric despite regular cleaning by pulsed-jet air. The pressure drop at the fabric filters leads to energy consumption at induced draft fan to keep the incinerator on negative pressure, so that its proper control is important to operate incineration facility efficiently. The pressure drop at fabric filters decreased whenever phosphoric acid wastewater (PAW) was sprayed into an incinerator for treating industrial waste. Operational data obtained from the incineration facility were analyzed to determine the short- and long-term effects of PAW spraying on the pressure drop. For the short-term effect, it was confirmed that the pressure drop at the fabric filters always decreased to 0.3-1.2kPa within about 5h after spraying PAW. This effect was expected to be obtained by about one third of present PAW spraying amount. However, from the long-term perspective, the pressure drop showed an increase in the periods of PAW spraying compared with periods for which PAW spraying was not performed. The pressure drop increase was particularly noticeable after the initial PAW spraying, regardless of the age and type of fabric filters used. These results suggest that present PAW spraying causes a temporary pressure drop reduction, leading to short-term energy consumption savings; however, it also causes an increase of the pressure drop over the long-term, degrading the overall operating conditions. Thus, appropriate PAW spraying conditions are needed to make effective use of PAW to reduce the pressure drop at fabric filters from a short- and long-term point of view. Copyright © 2016 Elsevier Ltd. All rights reserved.

  10. Experimental characterization of pressure drops and channel instabilities in helical coil SG tubes

    SciTech Connect

    Colombo, M.; Cammi, A.; De Amicis, J.; Ricotti, M. E.

    2012-07-01

    Helical tube heat exchangers provide better heat transfer characteristics, an improved capability to accommodate stresses due to thermal expansions and a more compact design with respect to straight tube heat exchangers. For these advantages they are considered as an option for the Steam Generator (SG) of many new reactor projects of Generation III+ and Generation IV. In particular, their compactness fits well with the requirements of Small-medium Modular Reactors (SMRs) of integral design, where all the primary system components are located inside the reactor vessel. In this framework, thermal hydraulics of helical pipes has been studied in recent years by Politecnico di Milano in different experimental campaigns. Experiments have been carried out in a full-scale open loop test facility installed at SIET labs in Piacenza (Italy)), to simulate the SG of a typical SMR. The facility includes two helical pipes (1 m coil diameter, 32 m length, 8 m height), connected via lower and upper headers. Following recently completed experimental campaigns dedicated to pressure drops and density wave instabilities, this paper deals with a new experimental campaign focused on both pressure drops (single-phase flow and two-phase flow, laminar and turbulent regimes) and flow instabilities. The availability of a large number of experimental data, in particular on two-phase flow, is of fundamental interest for correlation development, model validation and code assessment. Two-phase pressure drops have been measured in adiabatic conditions, ranging from 200 to 600 kg/m{sup 2}s for the mass flux, from 30 to 60 bar for the pressure and from 0.1 to 1.0 for the flow quality. The channel characteristics mass flow rate - pressure drop has been determined experimentally in the range 10-40 bar, varying the mass flow rate at a fixed value of the thermal flux. In addition, single-phase pressure drops have been measured in both laminar and turbulent conditions. Density wave instabilities have

  11. An experimental investigation of pressure drop of aqueous foam in laminar tube flow

    SciTech Connect

    Blackwell, B.F.; Sobolik, K.B.

    1987-04-01

    This report is the first of two detailing pressure-drop and heat-transfer measurements made at the Foam Flow Heat Transfer Loop. The work was motivated by a desire to extend the application of aqueous foam from petroleum drilling to geothermal drilling. Pressure-drop measurements are detailed in this report; a forthcoming report (SAND85-1922) will describe the heat-transfer measurements. The pressure change across a 2.4-m (8-ft) length of the 2.588-cm (1.019-in.) ID test section was measured for liquid volume fractions between 0.05 and 0.35 and average velocities between 0.12 and 0.80 m/s (0.4 and 2.6 ft/s). The resulting pressure-drop/flow-rate data were correlated to a theoretical model for a Bingham plastic. Simple expressions for the dynamic viscosity and the yield stress as a function of liquid volume fraction were estimated.

  12. Effects of vascular structures on the pressure drop in stenotic coronary arteries

    NASA Astrophysics Data System (ADS)

    Kim, Jaerim; Choi, Haecheon; Kweon, Jihoon; Kim, Young-Hak; Yang, Dong Hyun; Kim, Namkug

    2016-11-01

    A stenosis, which is a narrowing of a blood vessel, of the coronary arteries restricts the flow to the heart and it may lead to sudden cardiac death. Therefore, the accurate determination of the severity of a stenosis is a critical issue. Due to the convenience of visual assessments, geometric parameters such as the diameter stenosis and area stenosis have been used, but the decision based on them sometimes under- or overestimates the functional severity of a stenosis, i.e., pressure drop. In this study, patient-specific models that have similar area stenosis but different pressure drops are considered, and their geometries are reconstructed from the coronary computed tomography angiography (CCTA). Both steady and pulsatile inflows are considered for the simulations. Comparison between two models that have a bifurcation right after a stenosis shows that the parent to daughter vessel angle results in different secondary flow patterns and wall shear stress distributions which affect the pressure downstream. Thus, the structural features of the lower and upper parts of a stenosis significantly affect the pressure drop. Supported by 20152020105600.

  13. MHD pressure drop of NaK flow in stainless steel pipe

    SciTech Connect

    Miyazaki, K.; Kotake, S.

    1983-09-01

    An experiment on electric potential and pressure drop for NaK flow in uniform transverse magnetic fields was conducted. A test channel was constructed using 45.3 mm (or 28 mm) I.D. and 1.65 mm thick 304-SS circular pipe in the NaK-Blowdown MHD Experimental Facility of Osaka University. The experimental range covered had a driving gas pressure <8 bar, an applied magnetic flux density: B/sub 0/=0.3 about1.75 T, a mean flow velocity of NaK: U/sub 0/=2 about 15 m/sec, a Reynolds number Re = 8 X 10/sup 4/ about6.2 X 10/sup 5/ and a Hartmann number: Ha = 740 about4150. A theoretical analysis is given on the basis of a uniform-velocity thick-wall model. Good agreement between the theory and the experiment were obtained both for the potential and for the pressure drop, except a small deviation of the experimental pressure drop towards values lying above the theoretical ones in a weak B/sub 0/ and high U/sub 0/ region (Ha/sup 2//Re <15).

  14. [Nasal endoscope negative pressure cleaning and sinupret drops to treat radiation nasosinusitis].

    PubMed

    Lin, Wenbiao; Quan, Chaokun; Zhang, Longcheng

    2015-12-01

    To observe the effect of nasal endoscope negative pressure cleaning and sinupret drops to treat radiation nasosinusitis (RNS). One hundred and fifty-three patients with nasopharyngeal carcinoma were randomly divided into treatment group A, B, C . Group A using nasal endoscope negative pressure cleaning and sinupret drops, group B using nasal endoscope negative pressure cleaning and normal saline spray washing, group C using saline nasal irrigation through nasal catheter. All patients with sinusitis condition were evaluated at the end of radiotherapy, three months and six months after radiotherapy. Comparison between groups, three periods of RNS incidence, moderate to severe RNS incidence are A < B < C. Six months after radiotherapy, group A compared with group C, there are significant difference (P < 0.01), group A and group C compared with group B respectively, the difference was statistically significant (P < 0.05). Nasal endoscope negative pressure cleaning and sinupret drops can significantly reduce the long-term incidence of RNS, especially obviously reduce the incidence of moderate to severe RNS,which is a practical and effective method to treat RNS.

  15. Gas-liquid pressure drop in vertical internally wavy 90 bend

    SciTech Connect

    Benbella, Shannak; Al-Shannag, Mohammad; Al-Anber, Zaid A.

    2009-01-15

    Experiments of air water two-phase flow pressure drop in vertical internally wavy 90 bend have been carried out. The tested bends are flexible and made of stainless steel with inner diameter of 50 mm and various curvature radiuses of 200, 300, 400 and 500 mm. The experiments were performed under the following conditions of two-phase parameters; mass flux from 350 to 750 kg/m{sup 2} s. Gas quality from 1% to 50% and system pressure from 4 to 7.5 bar. The results demonstrate that the effect of the above-mentioned parameters is very significant at high ranges of mass flow quality. Due to the increasing of two-phase flow resistance, energy dissipations, friction losses and interaction of the two-phases in the vertical internally wavy 90 bend the total pressure drops are perceptible about 2-5 times grater than that in smooth bends. Based on the mass and energy balance as well as the presented experimental results, new empirical correlation has been developed to calculate the two-phase pressure drop and hence the two-phase friction factor of the tested bends. The correlation includes the relevant primary parameter, fit the data well, and is sufficiency accurate for engineering purposes. (author)

  16. Microfluidic analysis of pressure drop and flow behavior in hypertensive micro vessels.

    PubMed

    Hu, Ruiqing; Li, Fen; Lv, Jiaqi; He, Ying; Lu, Detang; Yamada, Takashi; Ono, Naoki

    2015-01-01

    The retinal arterial network is the only source of the highly nutrient-consumptive retina, thus any insult on the arteries can impair the retinal oxygen and nutrient supply and affect its normal function. The aim of this work is to study the influences of vascular structure variation on the flow and pressure characteristics via microfluidic devices. Two sets of micro-channel were designed to mimic the stenosed microvessels and dichotomous branching structure in the retinal arteries. Three working fluids including red blood cell (RBC) suspension were employed to investigate the pressure drop in the stenosed channel. The flow behaviors of RBC suspensions inside the micro channels were observed using high speed camera system. Pressure drop of different working fluids and RBC velocity profiles in the stenosed channel were obtained. Moreover, hematocrit levels of RBC suspensions inside the bifurcated channels were analyzed from the sequential images of RBC flow. The results of the flow in the stenosed channel show that RBCs drift from the center of the channels, and RBC velocity is influenced not only by the inlet flow rate but also the interaction between RBCs. The measured pressure drops in the stenosed channel increase notably with the increase of fluid viscosity. Furthermore, the dimensionless pressure drop due to the stenosis decreases with Reynolds number. On the other hand, the results of flow through the bifurcated channels show that as the ratio of the daughter-branch width to the mother-channel width increases, the ratio of hematocrit in two connected branches (Ht/Hd) decreases, which is in favorable agreement with the available analysis results.

  17. Pressure-Drop Considerations in the Characterization of Dew-Point Transfer Standards at High Temperatures

    NASA Astrophysics Data System (ADS)

    Mitter, H.; Böse, N.; Benyon, R.; Vicente, T.

    2012-09-01

    During calibration of precision optical dew-point hygrometers (DPHs), it is usually necessary to take into account the pressure drop induced by the gas flow between the "point of reference" and the "point of use" (mirror or measuring head of the DPH) either as a correction of the reference dew-point temperature or as part of the uncertainty estimation. At dew-point temperatures in the range of ambient temperature and below, it is sufficient to determine the pressure drop for the required gas flow, and to keep the volumetric flow constant during the measurements. In this case, it is feasible to keep the dry-gas flow into the dew-point generator constant or to measure the flow downstream the DPH at ambient temperature. In normal operation, at least one DPH in addition to the monitoring DPH are used, and this operation has to be applied to each instrument. The situation is different at high dew-point temperatures up to 95 °C, the currently achievable upper limit reported in this paper. With increasing dew-point temperatures, the reference gas contains increasing amounts of water vapour and a constant dry-gas flow will lead to a significant enhanced volume flow at the conditions at the point of use, and therefore, to a significantly varying pressure drop depending on the applied dew-point temperature. At dew-point temperatures above ambient temperature, it is also necessary to heat the reference gas and the mirror head of the DPH sufficiently to avoid condensation which will additionally increase the volume flow and the pressure drop. In this paper, a method is provided to calculate the dry-gas flow rate needed to maintain a known wet-gas flow rate through a chilled mirror for a range of temperature and pressures.

  18. Ppi results from the balloon drop experiment of the hasi pressure profile instrument

    NASA Astrophysics Data System (ADS)

    Mäkinen, T.; Lehto, A.; Salminen, P.; Leppelmeier, G.; Harri, A. M.

    1998-10-01

    At December 1995 a balloon drop experiment was conducted at León, Spain, for the HASI (Huygens Atmospheric Structure Instrument) instrument of the Huygens probe. A part of HASI is the Pressure Profile Instrument (PPI) which will measure the atmospheric pressure profile of Titan during the descent at November 2004. The experiment platform was carried by a balloon to an altitude of 30 km and it made a subsequent parachute-assisted descent. The pressure instrument functioned basically as expected. The vertical flight trajectory and pressure profile was reconstructed by using the collected data of the pressure instrument and the simultaneous temperature measurements. The calculated flight trajectory was in agreement with independent measurements with Omega and GPS. Some turbulence was detected near the surface and other dynamic behaviour in the upper part of the trajectory. The experiment demonstrated the nominal performance of the PPI instrument and serves as a real-like test flight for the actual mission.

  19. Pressure drop in the SHOOT superfluid helium acquisition system. [Superfluid Helium On-Orbit Transfer system

    NASA Technical Reports Server (NTRS)

    Nissen, J. A.; Maytal, B.; Van Sciver, S. W.

    1990-01-01

    Central to the upcoming Superfield Helium On-Orbit Transfer (SHOOT) demonstration is the fluid acquisition system. The main component of the system is a rectangular cross-section gallery area with one side fabricated from a fine mesh screen. He II enters through the screen and is delivered to a fountain effect pump. A model is proposed to predict the pressure drop as fluid flows through the screen and an expression is derived for the required gallery arm length as a function of flow rate demand. The model is compared with measurement of pressure drop in a full scale SHOOT gallery arm operated with flow rates of up to 850 cu dm/hr. The tests were conducted in the University of Wisconsin horizontal liquid helium flow facility to minimize gravitational effects.

  20. Numerical vs experimental pressure drops for Boger fluids in sharp-corner contraction flow

    NASA Astrophysics Data System (ADS)

    López-Aguilar, J. E.; Tamaddon-Jahromi, H. R.; Webster, M. F.; Walters, K.

    2016-10-01

    This paper addresses the problem of matching experimental findings with numerical prediction for the extreme experimental levels of pressure-drops observed in the 4:1 sharp-corner contraction flows, as reported by Nigen and Walters ["Viscoelastic contraction flows: Comparison of axisymmetric and planar configurations," J. Non- Newtonian Fluid Mech. 102, 343-359 (2002)]. In this connection, we report on significant success in achieving quantitative agreement between predictions and experiments. This has been made possible by using a new swanINNFM model, employing an additional dissipative function. Notably, one can observe that extremely large pressure-drops may be attained with a suitable selection of the extensional viscous time scale. In addition, and on vortex structure, the early and immediate vortex enhancement for Boger fluids in axisymmetric contractions has also been reproduced, which is shown to be absent in planar counterparts.

  1. Pressure-drop Reduction and Heat-transfer Deterioration of Slush Nitrogen in Square Pipe flow

    NASA Astrophysics Data System (ADS)

    Ohira, Katsuhide; Nakagomi, Kei; Takahashi, Koichi; Aoki, Itsuo

    Pressure drop and heat transfer tests were carried out using slush nitrogen flowing in a horizontal square pipe at flow velocity between 1.0 and 4.9 m/s, with a mass solid fraction between 6 and 26 wt.%, and with heat fluxes of 0, 10 and 20 kW/m2. Pressure drop reduction became apparent at flow velocity of 2.5 m/s and over, with the maximum amount of reduction being 12% in comparison with liquid nitrogen, regardless of heating, while heat transfer deterioration became apparent at flow velocity of 1.0 m/s and over, with the maximum amount of deterioration being 16 and 21% at 10 and 20 kW/m2, respectively.

  2. Numerical simulation of Flow Pressure Drop and Friction Factor of Water in 2D channel

    NASA Astrophysics Data System (ADS)

    Aya Baquero, H.; Camargo Casallas, L. H.

    2017-01-01

    The paper presents the results obtained from the numerical study of the dynamic properties of a straight channel 50 mm long and 780 μm wide on a 2D model. Numerical simulations were performed by using Navier-Stokes equation. The results showed a good agreement with experiments and other models. Pressure drop and friction factor of water in the channel in the studied ranges of Reynolds number are due to viscosity effects.

  3. Prediction of in-tube pressure drop of low GWP refrigerants during condensation and evaporation

    NASA Astrophysics Data System (ADS)

    Khan, Md. Masud Rana; Hossain, Md. Anowar; Afroz, Hasan M. M.; Miyara, Akio

    2017-06-01

    In the present work, a new in-tube two phase pressure drop correlation of low GWP refrigerants during condensation and evaporation has been proposed in this paper. This correlation for the prediction of condensation and evaporation pressure drop inside smooth horizontal tube by incorporating the effect of mass velocity, tube geometry and surface tension. By comparing with other existing well-known correlations and the newly proposed correlation of two-phase pressure drop have been used to predict the condensation and evaporation pressure drop of R1234ze(E), R32, R410A, dimethyl ether (DME), CO2/DME mixtures (10/90, 25/75 and 45/55 weight %) and R1234ze(E)/R32 mixtures (30/70 and 45/55 weight %) inside a horizontal smooth tube. The predicted results have been compared with the available experimental data which is done inside a water heated double tube heat exchanger. The test section is a horizontally installed smooth tube with effective length of 3.6m and inner diameter of 4.35mm. The experiment had been carried out under the conditions of mass flux varying from 147 to 403 kgm-2s-1 and the saturation temperatures ranging between 30 and 45°C for condensation and 5-10°C for evaporation, over the vapor quality range 0.00 to 1.00. From the analysis and results of comparison, proposed correlation shows better performance. Proposed correlation can predict all the experimental condensation and evaporation data within ±13.91%.

  4. Isolation of Indonesian cananga oil using multi-cycle pressure drop process.

    PubMed

    Kristiawan, Magdalena; Sobolik, Vaclav; Allaf, Karim

    2008-05-30

    New process, instantaneous controlled pressure drop (DIC) was applied on Cananga odorata dry flowers with the aim to isolate essential oil. DIC is based on high temperature, short time heating followed by an abrupt pressure drop into a vacuum. A part of volatile compounds is carried away from flowers in the form of vapor (DIC direct oil) that evolves adiabatically during the pressure drop (proper isolation process) and the other part remains in the DIC-treated flowers (DIC residual oil). In the present paper, the effect of DIC cycle number (1-9) and heating time (4.3-15.7 min) on the availability of oil compounds was investigated at three levels of steam pressure (0.28, 0.4 and 0.6 MPa). The availability was defined as the amount of a compound in direct or residual oil divided by the amount of this compound in the reference oil extracted from non-treated flowers by chloroform during 2h. The total availability and yield of volatiles in the direct oil increased with pressure and cycle number. At a higher pressure, the effect of heating time was insignificant. The amount of oxygenated monoterpenes and other light oxygenated compounds (i.e. predominantly exogenous compounds) in the residual flowers was lower than in the direct oil and this amount decreased with cycle number. On the other hand, the availability of oxygenated sesquiterpenes and other heavy oxygenated compounds (i.e. predominantly endogenous compounds) in residual flowers exhibited a maximum for about five cycles and their quantity at this point was three times as much as in the direct oil. The total availability of each compound at 0.6 MPa was higher than one. The rapid DIC process (0.6 MPa, 8 cycles, 6 min) gave better results than steam distillation (16 h) concerning direct oil yield (2.8%dm versus 2.5%dm) and content of oxygenated compounds (72.5% versus 61.7%).

  5. Pressure drop in fully developed, duct flow of dispersed liquid-vapor mixture at zero gravity

    NASA Technical Reports Server (NTRS)

    Sridhar, K. R.; Chao, B. T.; Soo, S. L.

    1990-01-01

    The dynamics of steady, fully developed dispersed liquid-vapor flow in a straight duct at 0-g is simulated by flowing water containing n-butyl benzoate droplets. Water and benzoate are immiscible and have identical density at room temperature. The theoretical basis of the simulation is given. Experiments showed that, for a fixed combined flow rate of water and benzoate, the frictional pressure drop is unaffected by large changes in the volume fraction of benzoate drops and their size distribution. Measured power spectra of the static wall pressure fluctuations induced by the turbulent water-benzoate flow also revealed that their dynamics is essentially unaltered by the presence of the droplets. These experimental findings, together with the theoretical analysis, led to the conclusion that the pressure drop in fully developed, dispersed liquid-vapor flow in straight ducts of constant cross section at 0-g is identical to that due to liquid flowing alone at the same total volumetric flow rate of the liquid-vapor mixture and, therefore, can be readily determined.

  6. Heat transfer and pressure drop in rectangular channels with crossing fins (a Review)

    NASA Astrophysics Data System (ADS)

    Sokolov, N. P.; Polishchuk, V. G.; Andreev, K. D.; Rassokhin, V. A.; Zabelin, N. A.

    2015-06-01

    Channels with crossing finning find wide use in the cooling paths of high-temperature gas turbine blade systems. At different times, different institutions carried out experimental investigations of heat transfer and pressure drop in channels with coplanar finning of opposite walls for obtaining semiempirical dependences of Nusselt criteria (dimensionless heat-transfer coefficients) and pressure drop coefficients on the operating Reynolds number and relative geometrical parameters (or their complexes). The shape of experimental channels, the conditions of experiments, and the used variables were selected so that they would be most suited for solving particular practical tasks. Therefore, the results obtained in processing the experimental data have large scatter and limited use. This article considers the results from experimental investigations of different authors. In comparing the results, additional calculations were carried out for bringing the mathematical correlations to the form of dependences from the same variables. Generalization of the results is carried out. In the final analysis, universal correlations are obtained for determining the pressure drop coefficients and Nusselt number values for the flow of working medium in channels with coplanar finning.

  7. Heat transfer and pressure drop in pin-fin trapezoidal ducts

    SciTech Connect

    Hwang, J.J.; Lai, D.Y.; Tsia, Y.P.

    1999-04-01

    Experiments are conducted to determine the log-mean averaged Nusselt number and overall pressure-drop coefficient in a pin-fin trapezoidal duct that models the cooling passages in modern gas turbine blades. The effects of pin arrangement (in-line and staggered), flow Reynolds number (6,000 {le} Re {le}40,000) and ratio of lateral-to-total flow rate (0 {le} {var_epsilon} {le} 1.0) are examined. The results of smooth trapezoidal ducts without pin arrays are also obtained for comparison. It is found that, for the single-outlet-flow duct, the log-mean averaged Nusselt number in the pin-fin trapezoidal duct with lateral outlet is insensitive to the pin arrangement, which is higher than that in straight-outlet-flow duct with the corresponding pin array. As for the trapezoidal ducts having both outlets, the log-mean averaged Nusselt number has a local minimum value at about {var_epsilon} = 0.3. After about {var_epsilon} {ge} 0.8, the log-mean averaged Nusselt number is nearly independent of the pin configuration. Moreover, the staggered pin array pays more pressure-drop penalty as compared with the in-line pin array in the straight-outlet-flow duct; however, in the lateral-outlet-flow duct, the in-line and staggered pin arrays yield almost the same overall pressure drop.

  8. Theoretical investigation of pressure drop in combined cyclone and fabric filter systems

    NASA Astrophysics Data System (ADS)

    Dirgo, John A.; Cooper, Douglas W.

    Computer simulations were conducted to investigate potential pressure drop reductions obtainable by combining cyclones, as pre-collectors, with fabric filters. The Leith-Licht model was used to characterize cyclone emissions and the specific resistance ( K2) of the fabric filter dust cake was calculated from an empirical correlation. Several important dimensionless groups were identified and evaluated. One group, the product of the ratio of the dust cake specific resistances expected with and without the cyclone and the mass penetration of the cyclone, ( K2/ K2) Pn, indicates whether a pressure drop reduction is possible. A correlation was developed for this group as a function of the size properties of the inlet dust (particle mass median diameter and geometric standard deviation) and the cyclone particle cut diameter. Expressions were derived for the break-even time, the duration of filtration with the cyclone needed to show a pressure drop reduction in comparison with filtration without the cyclone. It is shown that in previously reported experiments and simulations indicating an advantage for the combined cyclone-fabric filter system, filtration cycles were typically longer than the break-even time; those showing no improvement typically had filtration times shorter than the break-even time.

  9. Pressure drop in fully developed, duct flow of dispersed liquid-vapor mixture at zero gravity

    NASA Technical Reports Server (NTRS)

    Sridhar, K. R.; Chao, B. T.; Soo, S. L.

    1990-01-01

    The dynamics of steady, fully developed dispersed liquid-vapor flow in a straight duct at 0-g is simulated by flowing water containing n-butyl benzoate droplets. Water and benzoate are immiscible and have identical density at room temperature. The theoretical basis of the simulation is given. Experiments showed that, for a fixed combined flow rate of water and benzoate, the frictional pressure drop is unaffected by large changes in the volume fraction of benzoate drops and their size distribution. Measured power spectra of the static wall pressure fluctuations induced by the turbulent water-benzoate flow also revealed that their dynamics is essentially unaltered by the presence of the droplets. These experimental findings, together with the theoretical analysis, led to the conclusion that the pressure drop in fully developed, dispersed liquid-vapor flow in straight ducts of constant cross section at 0-g is identical to that due to liquid flowing alone at the same total volumetric flow rate of the liquid-vapor mixture and, therefore, can be readily determined.

  10. An experimental and theoretical study of density wave and pressure drop oscillations

    SciTech Connect

    Yuncu, H. )

    1990-01-01

    A study of the stability of an electrically heated, forced-convection, single horizontal channel system with a gas-loaded surge tank placed upstream of the heated channel was conducted. Freon 11 was used as the test fluid. The major modes of oscillations, namely, density wave-type (high-frequency) and pressure drop-type (low-frequency)oscillations, have been observed. Steady-state pressure drops, stable and unstable boundaries are experimentally determined for given ranges of heat flux, mass flow rate, and compressible volume in the surge tank. An analytical model has been developed to predict stable and unstable boundaries for the pressure drop and density wave oscillations of the boiling two-phase flow system. The model is based on homogenous flow assumption and thermodynamic equilibrium between the liquid and vapor phases. The governing equations are solved first to establish the steady-state behavior of the system. This solution is then used to obtain the unsteady solution by perturbation technique.

  11. Experimental and numerical studies of coal gasification with pressurized drop tube furnace

    SciTech Connect

    Ahn, D.H.; Park, H.Y.; Kim, C.Y.

    1997-12-31

    This paper describes coal gasification studies in a PDTF reactor for IGCC. The effects of changes in reaction temperature and oxygen/coal ratio on the coal gasification process have been investigated by utilizing a pressurized drop tube furnace. The objective of this study is to determine the reaction mechanisms and kinetics for gasification of imported coals under the simulated operating conditions of commercial entrained flow gasifier. The PDTF reactor is designed to operate up to a temperature of about 1,600 C, a pressure of up to 25 bar with a wide range of inert, reducing and oxidizing atmospheres. The effects of changes in reaction temperature and oxygen/coal ratio on the coal gasification process of Datong Chinese coal have been investigated by utilizing a pressurized drop tube furnace. Pulverized coal of under 200 mesh with a feed rate of 2g/min is fed into the reaction tube by transport nitrogen gas of 2 SLPM. Instead of using oxygen, air is used as a secondary stream of oxidant for the gasification reaction with feed rate of 4.1 to 9.5 SLPM according to the oxygen/coal ratio of 0.6 to 1.4, which is preheated up to the reaction temperature. The reaction temperature is changed to 1,000 C, 1,200 C and 1,400 C respectively. However, the effects of pressure and steam/coal ratio on gasification were not considered in this experiment. In order to provide the proper engineering analyses for design and operation of a commercial coal gasifier for IGCC, it is necessary to characterize the basic behavior of gasification of coals at the same operating condition as the gasifier. A Pressurized Drop Tube Furnace reactor is considered as an useful facility for the such kinetic studies.

  12. Effects of sudden expansion and contraction flow on pressure drops in the Stirling engine regenerator

    SciTech Connect

    Hamaguchi, K.; Yamashita, I.; Hirata, K.

    1998-07-01

    The flow losses in the regenerators greatly influence the performance of the Stirling engine. The losses mainly depend on fluid friction through the regenerator matrix, but are also generated in sudden expansion and contraction flow at the regenerator ends. The latter losses can't be neglected in the case of small area ratio (entrance area/cross-sectional area in regenerator). The pressure drops in regenerators are usually estimated assuming a uniform velocity distribution of working gas in the matrices. The estimation results, however, are generally smaller than practical data. The cross-sectional flow areas of the heater and cooler of typical Stirling engines are smaller than the cross- sectional area of the regenerator. The effects of the small flow passage on the velocity distribution of working fluid in the matrix, that is, a flow transition from tubes or channels to a regenerator matrix, can be often confirmed by the discolored matrix. Especially, the lack of a uniform distribution of velocity in the matrix causes increased flow loss and decreased thermal performance. So, it is necessary to understand the quantitative effects of the sudden change in flow area at the regenerator ends on the velocity distribution and pressure drop. In this paper, using matrices made of stacks of wire screens, the effects of the entrance and exit areas and the length of the regenerator on pressure drops are examined by an unidirectional steady flow apparatus. The experimental data are arranged in an empirical equation. The lack of a uniformity of velocity distribution is visualized using smoke-wire methods. The empirical equation presented is applied to the estimation of pressure loss in an actual engine regenerator. The applicability of the equation is examined by comparison of estimated value with engine data in pressure loss.

  13. Estimating the irreversible pressure drop across a stenosis by quantifying turbulence production using 4D Flow MRI

    NASA Astrophysics Data System (ADS)

    Ha, Hojin; Lantz, Jonas; Ziegler, Magnus; Casas, Belen; Karlsson, Matts; Dyverfeldt, Petter; Ebbers, Tino

    2017-04-01

    The pressure drop across a stenotic vessel is an important parameter in medicine, providing a commonly used and intuitive metric for evaluating the severity of the stenosis. However, non-invasive estimation of the pressure drop under pathological conditions has remained difficult. This study demonstrates a novel method to quantify the irreversible pressure drop across a stenosis using 4D Flow MRI by calculating the total turbulence production of the flow. Simulation MRI acquisitions showed that the energy lost to turbulence production can be accurately quantified with 4D Flow MRI within a range of practical spatial resolutions (1-3 mm regression slope = 0.91, R2 = 0.96). The quantification of the turbulence production was not substantially influenced by the signal-to-noise ratio (SNR), resulting in less than 2% mean bias at SNR > 10. Pressure drop estimation based on turbulence production robustly predicted the irreversible pressure drop, regardless of the stenosis severity and post-stenosis dilatation (regression slope = 0.956, R2 = 0.96). In vitro validation of the technique in a 75% stenosis channel confirmed that pressure drop prediction based on the turbulence production agreed with the measured pressure drop (regression slope = 1.15, R2 = 0.999, Bland-Altman agreement = 0.75 ± 3.93 mmHg).

  14. Estimating the irreversible pressure drop across a stenosis by quantifying turbulence production using 4D Flow MRI

    PubMed Central

    Ha, Hojin; Lantz, Jonas; Ziegler, Magnus; Casas, Belen; Karlsson, Matts; Dyverfeldt, Petter; Ebbers, Tino

    2017-01-01

    The pressure drop across a stenotic vessel is an important parameter in medicine, providing a commonly used and intuitive metric for evaluating the severity of the stenosis. However, non-invasive estimation of the pressure drop under pathological conditions has remained difficult. This study demonstrates a novel method to quantify the irreversible pressure drop across a stenosis using 4D Flow MRI by calculating the total turbulence production of the flow. Simulation MRI acquisitions showed that the energy lost to turbulence production can be accurately quantified with 4D Flow MRI within a range of practical spatial resolutions (1–3 mm; regression slope = 0.91, R2 = 0.96). The quantification of the turbulence production was not substantially influenced by the signal-to-noise ratio (SNR), resulting in less than 2% mean bias at SNR > 10. Pressure drop estimation based on turbulence production robustly predicted the irreversible pressure drop, regardless of the stenosis severity and post-stenosis dilatation (regression slope = 0.956, R2 = 0.96). In vitro validation of the technique in a 75% stenosis channel confirmed that pressure drop prediction based on the turbulence production agreed with the measured pressure drop (regression slope = 1.15, R2 = 0.999, Bland-Altman agreement = 0.75 ± 3.93 mmHg). PMID:28425452

  15. Hereditary neuropathy with liability to pressure palsy: a recurrent and bilateral foot drop case report.

    PubMed

    Flor-de-Lima, Filipa; Macedo, Liliana; Taipa, Ricardo; Melo-Pires, Manuel; Rodrigues, Maria Lurdes

    2013-01-01

    Hereditary neuropathy with liability to pressure palsy is characterized by acute, painless, recurrent mononeuropathies secondary to minor trauma or compression. A 16-year-old boy had the first episode of right foot drop after minor motorcycle accident. Electromyography revealed conduction block and slowing velocity conduction of the right deep peroneal nerve at the fibular head. After motor rehabilitation, he fully recovered. Six months later he had the second episode of foot drop in the opposite site after prolonged squatting position. Electromyography revealed sensorimotor polyneuropathy of left peroneal, sural, posterior tibial, and deep peroneal nerves and also of ulnar, radial, and median nerves of both upper limbs. Histological examination revealed sensory nerve demyelination and focal thickenings of myelin fibers. The diagnosis of hereditary neuropathy with liability to pressure palsy was confirmed by PMP22 deletion of chromosome 17p11.2. He started motor rehabilitation and avoidance of stressing factors with progressive recovery. After one-year followup, he was completely asymptomatic. Recurrent bilateral foot drop history, "sausage-like" swellings of myelin in histological examination, and the results of electromyography led the authors to consider the diagnosis despite negative family history. The authors highlight this rare disease in pediatric population and the importance of high index of clinical suspicion for its diagnosis.

  16. Extraction of essential oils from Algerian myrtle leaves using instant controlled pressure drop technology.

    PubMed

    Berka-Zougali, Baya; Hassani, Aicha; Besombes, Colette; Allaf, Karim

    2010-10-01

    In the present work, the new extraction process of Détente Instantanée Contrôlée DIC (French, for instant controlled pressure drop) was studied, developed, quantitatively and qualitatively compared to the conventional hydrodistillation method for the extraction of essential oils from Algerian myrtle leaves. DIC was used as a thermomechanical treatment, DIC subjecting the product to a high-pressure saturated steam. The DIC cycle ends with an abrupt pressure drop towards vacuum, and this instantly leads to an autovaporization of myrtle volatile compounds. An immediate condensation in the vacuum tank produced a micro-emulsion of water and essential oils. Thus, an ultra-rapid cooling of residual leaves occurred, precluding any thermal degradation. An experimental protocol was designed with 3 independent variables: saturated steam pressure between 0.1 and 0.6 MPa, resulting in a temperature between 100 and 160°C, a total thermal processing time between 19 and 221 s, and between 2 and 6 DIC cycles. The essential oils yield was defined as the main dependent variable. This direct extraction gave high yields and high quality essential oil, as revealed by composition and antioxidant activity (results not shown). After this treatment, the myrtle leaves were recovered and hydrodistilled in order to quantify the essential oil content in residual DIC-treated samples. Scanning electron microscope (SEM) showed some modification of the structure with a slight destruction of cell walls after DIC treatment.

  17. Statistical correlation between transient pressure drop and cavitation at closure of a mechanical heart valve.

    PubMed

    Wu, Changfu; Liu, Jia-Shing; Hwang, Ned H C; Lin, Yu-Kweng M

    2005-01-01

    Cavitation on a mechanical heart valve (MHV) is attributable to transient regional pressure drop at the instant of valve closure. As a cavitation bubble collapses, it emits shock waves, which have the characteristics of high frequency oscillations (HFO) on a pressure time trace. The potential for such HFO bursts to cause material damage on an MHV can be measured by the cavitation impulse I, which is defined as the area under the trace of the HFO bursts. In the present study, experiments were conducted on a bileaflet MHV in a durability tester, operated at pulse rates from 300-1,000 bpm. In each case, the transient pressure near an occluder was monitored for 60,000 beats via a transducer. The peak pressure drop Pm and the corresponding cavitation impulse I obtained for the 60,000 beat sequence are found to resemble sample records of two stationary stochastic processes, each of which follows a log normal distribution. Their first order probability density functions are estimated from the records. The correlation is investigated between I and Pm associated with each beat, which is found to be of statistical significance.

  18. Development of a new pressure dependent threshold superheated drop detector for neutrons

    NASA Astrophysics Data System (ADS)

    Rezaeian, Peiman; Raisali, Gholamreza; Akhavan, Azam; Ghods, Hossein; Hajizadeh, Bardia

    2015-03-01

    In this paper, a set of superheated drop detectors operated at different pressures is developed and fabricated by adding an appropriate amount of Freon-12 liquid on the free surface of the detector. The fabricated detectors have been used for determination of the threshold pressure for 2.89 MeV neutrons of a neutron generator in order to estimate the thermodynamic efficiency. Finally, knowing the thermodynamic efficiency of the detector and in a similar manner, the threshold pressure for 241Am-Be neutrons is determined and accordingly, the maximum neutron energy of the source spectrum is estimated. The maximum neutron energy of the 241Am-Be is estimated as 10.97±2.11 MeV. The agreement between this measured maximum energy and the reported value of the 241Am-Be neutron source shows that the method developed to apply pressure on the superheated drop detectors can be used to control the energy threshold of these detectors.

  19. 75 FR 31288 - Plant-Verified Drop Shipment (PVDS)-Nonpostal Documentation

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-03

    ... Service, Domestic Mail Manual (DMM ) 705.15. 2.14 to clarify that PS Form 8125, Plant-Verified Drop... following changes to the Mailing Standards for the United States Postal Service, Domestic Mail Manual (DMM... Subjects in 39 CFR Part 111 Administrative practice and procedure, Postal Service. 0 Accordingly, 39 CFR...

  20. The influence of the equivalent hydraulic diameter on the pressure drop prediction of annular test section

    NASA Astrophysics Data System (ADS)

    Al-Kayiem, A. H. H.; Ibrahim, M. A.

    2015-12-01

    The flow behaviour and the pressure drop throughout an annular flow test section was investigated in order to evaluate and justify the reliability of experimental flow loop for wax deposition studies. The specific objective of the present paper is to assess and highlight the influence of the equivalent diameter method on the analysis of the hydrodynamic behaviour of the flow and the pressure drop throughout the annular test section. The test section has annular shape of 3 m length with three flow passages, namely; outer thermal control jacket, oil annular flow and inner pipe flow of a coolant. The oil annular flow has internal and external diameters of 0.0422 m and 0.0801 m, respectively. Oil was re-circulated in the annular passage while a cold water-glycol mixture was re-circulated in the inner pipe counter currently to the oil flow. The experiments were carried out at oil Reynolds number range of 2000 to 17000, covering laminar, transition and turbulent flow regimes. Four different methods of equivalent diameter of the annulus have been considered in this hydraulic analysis. The correction factor model for frictional pressure drop was also considered in the investigations. All methods addressed the high deviation of the prediction from the experimental data, which justified the need of a suitable pressure prediction correlation for the annular test section. The conventional hydraulic diameter method is a convenient substitute for characterizing physical dimension of a non-circular duct, and it leads to fairly good correlation between turbulent fluid flow and heat transfer characteristic of annular ducts.

  1. Numerical investigation of cavitation flow inside spool valve with large pressure drop

    NASA Astrophysics Data System (ADS)

    Deng, Jian; Pan, Dingyi; Xie, Fangfang; Shao, Xueming

    2015-12-01

    Spool valves play an important role in fluid power system. Cavitation phenomena happen frequently inside the spool valves, which cause structure damages, noise and lower down hydrodynamic performance. A numerical tools incorporating the cavitation model, are developed to predict the flow structure and cavitation pattern in the spool valve. Two major flow states in the spool valve chamber, i.e. flow-in and flow-out, are studies. The pressure distributions along the spool wall are first investigated, and the results agree well with the experimental data. For the flow-in cases, the local pressure at the throttling area drops much deeper than the pressure in flow-out cases. Meanwhile, the bubbles are more stable in flow-in cases than those in flow-out cases, which are ruptured and shed into the downstream.

  2. The impact of mass flow and masking on the pressure drop of air filter in heavy-duty diesel engine

    NASA Astrophysics Data System (ADS)

    Hoseeinzadeh, Sepideh; Gorji-Bandpy, Mofid

    2012-04-01

    This paper presents a computational fluid dynamics (CFD) calculation approach to predict and evaluate the impact of the mass-flow inlet on the pressure drop of turbocharger`s air filtfer in heavy-duty diesel engine. The numerical computations were carried out using a commercial CFD program whereas the inlet area of the air filter consisted of several holes connected to a channel. After entering through the channel, the air passes among the holes and enters the air filter. The effect of masking holes and hydraulic diameter is studied and investigated on pressure drop. The results indicate that pressure drop increase with decreasing of hydraulic diameter and masking of the holes has considerable affect on the pressure drop.

  3. Effect of nepafenac eye drops on intraocular pressure: a randomized prospective study.

    PubMed

    Dave, Paaraj; Shah, Kuntal; Ramchandani, Bharat; Jain, Rupa

    2014-03-01

    To report the effect of nepafenac (0.1%) eye drops on intraocular pressure in eyes with cataract. Prospective randomized clinical trial. Three hundred and twenty-seven patients with bilateral cataracts in an institutional setting were included. All patients had a baseline intraocular pressure (IOP) ≤ 21 mm Hg without a history of intraocular surgery in the past 3 months. One eye of each individual was randomized to the treatment group, with the other eye acting as a control. Nepafenac (0.1%) eye drops were instilled 3 times a day in the eye that received treatment. Intraocular pressure (IOP) with Goldmann applanation tonometer (GAT) was measured at baseline and at 4 and 8 weeks. Proportion of eyes with an IOP elevation of >4 mm Hg was the main outcome measure. The mean age of the participants was 45.7 ± 4.4 years. Participants included 192 female and 135 male patients. The mean IOP at baseline in the treated and control eyes was, respectively, 13.8 ± 2.5 mm Hg and 13.4 ± 3.0 mm Hg, which reduced to 12.0 ± 2.0 mm Hg and 12.1 ± 1.5 mm Hg, respectively, at the end of 8 weeks. This reduction in IOP in both groups was significant (P < .01). The difference between the IOP in the treated and control eyes at 8 weeks was not statistically significant (P = .34). One eye in the treated group and 2 eyes in the control group had an IOP elevation of >4 mm Hg. Nepafenac eye drops do not increase the IOP. They can possibly be used as an alternative to steroid medications where steroid responsiveness is a concern. Copyright © 2014 Elsevier Inc. All rights reserved.

  4. Geometry-based pressure drop prediction in mildly diseased human coronary arteries.

    PubMed

    Schrauwen, J T C; Wentzel, J J; van der Steen, A F W; Gijsen, F J H

    2014-06-03

    Pressure drop (△p) estimations in human coronary arteries have several important applications, including determination of appropriate boundary conditions for CFD and estimation of fractional flow reserve (FFR). In this study a △p prediction was made based on geometrical features derived from patient-specific imaging data. Twenty-two mildly diseased human coronary arteries were imaged with computed tomography and intravascular ultrasound. Each artery was modelled in three consecutive steps: from straight to tapered, to stenosed, to curved model. CFD was performed to compute the additional △p in each model under steady flow for a wide range of Reynolds numbers. The correlations between the added geometrical complexity and additional △p were used to compute a predicted △p. This predicted △p based on geometry was compared to CFD results. The mean △p calculated with CFD was 855±666Pa. Tapering and curvature added significantly to the total △p, accounting for 31.4±19.0% and 18.0±10.9% respectively at Re=250. Using tapering angle, maximum area stenosis and angularity of the centerline, we were able to generate a good estimate for the predicted △p with a low mean but high standard deviation: average error of 41.1±287.8Pa at Re=250. Furthermore, the predicted △p was used to accurately estimate FFR (r=0.93). The effect of the geometric features was determined and the pressure drop in mildly diseased human coronary arteries was predicted quickly based solely on geometry. This pressure drop estimation could serve as a boundary condition in CFD to model the impact of distal epicardial vessels.

  5. Dysfunctional vestibular system causes a blood pressure drop in astronauts returning from space.

    PubMed

    Hallgren, Emma; Migeotte, Pierre-François; Kornilova, Ludmila; Delière, Quentin; Fransen, Erik; Glukhikh, Dmitrii; Moore, Steven T; Clément, Gilles; Diedrich, André; MacDougall, Hamish; Wuyts, Floris L

    2015-12-16

    It is a challenge for the human body to maintain stable blood pressure while standing. The body's failure to do so can lead to dizziness or even fainting. For decades it has been postulated that the vestibular organ can prevent a drop in pressure during a position change--supposedly mediated by reflexes to the cardiovascular system. We show--for the first time--a significant correlation between decreased functionality of the vestibular otolith system and a decrease in the mean arterial pressure when a person stands up. Until now, no experiments on Earth could selectively suppress both otolith systems; astronauts returning from space are a unique group of subjects in this regard. Their otolith systems are being temporarily disturbed and at the same time they often suffer from blood pressure instability. In our study, we observed the functioning of both the otolith and the cardiovascular system of the astronauts before and after spaceflight. Our finding indicates that an intact otolith system plays an important role in preventing blood pressure instability during orthostatic challenges. Our finding not only has important implications for human space exploration; they may also improve the treatment of unstable blood pressure here on Earth.

  6. Dysfunctional vestibular system causes a blood pressure drop in astronauts returning from space

    PubMed Central

    Hallgren, Emma; Migeotte, Pierre-François; Kornilova, Ludmila; Delière, Quentin; Fransen, Erik; Glukhikh, Dmitrii; Moore, Steven T.; Clément, Gilles; Diedrich, André; MacDougall, Hamish; Wuyts, Floris L.

    2015-01-01

    It is a challenge for the human body to maintain stable blood pressure while standing. The body’s failure to do so can lead to dizziness or even fainting. For decades it has been postulated that the vestibular organ can prevent a drop in pressure during a position change – supposedly mediated by reflexes to the cardiovascular system. We show – for the first time – a significant correlation between decreased functionality of the vestibular otolith system and a decrease in the mean arterial pressure when a person stands up. Until now, no experiments on Earth could selectively suppress both otolith systems; astronauts returning from space are a unique group of subjects in this regard. Their otolith systems are being temporarily disturbed and at the same time they often suffer from blood pressure instability. In our study, we observed the functioning of both the otolith and the cardiovascular system of the astronauts before and after spaceflight. Our finding indicates that an intact otolith system plays an important role in preventing blood pressure instability during orthostatic challenges. Our finding not only has important implications for human space exploration; they may also improve the treatment of unstable blood pressure here on Earth. PMID:26671177

  7. Pressure drop and mass transfer in two-pass ribbed channels

    NASA Technical Reports Server (NTRS)

    Chandra, P. R.; Han, J. C.

    1989-01-01

    The combined effects of the sharp 180-deg turn and of the rib configuration on the pressure drop and mass transfer characteristics in a two-pass square channel with a pair of opposite rib-roughened walls (to simulate turbine airfoil cooling passages) were determined for a Reynolds number range of 10,000-60,000. Heat transfer enhancements were compared for the first pass and for the two-pass channel with the sharp 180-deg turn. Correlations for the fully-developed friction factors and loss coefficients were obtained.

  8. A New Population Dataset on Dust Devil Pressure Drops : Setting the Stage for Mars Science Laboratory

    NASA Astrophysics Data System (ADS)

    Lorenz, R. D.

    2012-09-01

    A quarter of a century ago in the first in-situ study of dust devils on Mars, Ryan and Lucich (1983) rue that 'Unfortunately, we have been unable to find a terrestrial data set that permits a one-to-one comparison with our Mars data'. Remarkably, this state of affairs has largely persisted. Here I present a set of fixed station terrestrial field data, enabled by recent technological developments, which enables a direct comparison with dust devils (as indicated by vortex pressure drops) from Mars Pathfinder, Phoenix, and hopefully MSL Curiosity.

  9. The Interdependence of Plate Coupling Processes, Subduction Rate, and Asthenospheric Pressure Drop across Subducting Slabs

    NASA Astrophysics Data System (ADS)

    Royden, L.; Holt, A.; Becker, T. W.

    2015-12-01

    One advantage of analytical models, in which analytic expressions are used for the various components of the subduction system, is the efficient exploration of parameter space and identification of the physical mechanisms controlling a wide breadth of slab kinematics. We show that, despite subtle differences in how plate interfaces and boundary conditions are implemented, results for single subduction from a 3-D semi-analytical model for subduction FAST (Royden & Husson, 2006; Jagoutz et al., 2015) and from the numerical finite-element model CitcomCU (Moresi & Gurnis, 1996, Zhong et al., 2006) are in excellent agreement when plate coupling (via shear stress on the plate interface) takes place in the FAST without the development of topographic relief at the plate boundary. Results from the two models are consistent across a variety of geometries, with fixed upper plate, fixed lower plate, and stress-free plate ends. When the analytical model is modified to include the development of topography above the subduction boundary, subduction rates are greatly increased, indicating a strong sensitivity of subduction to the mode of plate coupling. Rates of subduction also correlate strongly with the asthenospheric pressure drop across the subducting slab, which drives toroidal flow of the asthenosphere around the slab. When the lower plate is fixed, subduction is relatively slow and the pressure drop from below to above the slab is large, inhibiting subduction and slab roll-back. When the upper plate is fixed and when the plate ends are stress-free, subduction rates are approximately 50% faster and the corresponding asthenospheric pressure drop from below to above the slab is small, facilitating rapid subduction. This qualitative correlation between plate coupling processes, asthenospheric pressure drop, and rates of subduction can be extended to systems with more than one subduction zone (Holt et al., 2015 AGU Fall Abstract). Jagoutz, O., Royden, L., Holt, A. & Becker, T. W

  10. Minimum rate of spouting and peak pressure-drop in a spouted bed

    SciTech Connect

    Ogino, Fumiaru; Zhang, Laiying; Maehashi, Yasuo . Dept. of Chemical Engineering)

    1993-04-01

    Spouted beds are a type of fluidized bed, but one which has certain advantages, viz., (1) the capability of handling coarse particles; (2) the capability of handling particles with complicated shapes; (3) the absence of the need to have a high flow-rate; and (4) a small pressure drop. The first and second of these advantages, in particular, are responsible for spouted beds having found use in industry in the drying of powdered materials, in granulation apparatus, in the roasting of mineral ores, and in waste incinerators, while their application in coal gasification and shale pyrolysis is, also, examined.

  11. Influence of arterial wall compliance on the pressure drop across coronary artery stenoses under hyperemic flow condition.

    PubMed

    Konala, Bhaskar Chandra; Das, Ashish; Banerjee, Rupak K

    2011-03-01

    Hemodynamic endpoints such as flow and pressure drop are often measured during angioplasty procedures to determine the functional severity of a coronary artery stenosis. There is a lack of knowledge regarding the influence of compliance of the arterial wall-stenosis on the pressure drop under hyperemic flows across coronary lesions. This study evaluates the influence in flow and pressure drop caused by variation in arterial-stenosis compliance for a wide range of stenosis severities. The flow and pressure drop were evaluated for three different severities of stenosis and tested for limiting scenarios of compliant models. The Mooney-Rivlin model defined the non-linear material properties of the arterial wall and the plaque regions. The non-Newtonian Carreau model was used to model the blood flow viscosity. The fluid (blood)-structure (arterial wall) interaction equations were solved numerically using the finite element method. Irrespective of the stenosis severity, the compliant models produced a lower pressure drop than the rigid artery due to compliance of the plaque region. A wide variation in the pressure drop was observed between different compliant models for significant (90% area occlusion) stenosis with 41.0, 32.1, and 29.8 mmHg for the rigid artery, compliant artery with calcified plaque, and compliant artery with smooth muscle cell proliferation, respectively. When compared with the rigid artery for significant stenosis the pressure drop decreased by 27.7% and 37.6% for the calcified plaque and for the smooth muscle cell proliferation case, respectively. These significant variations in pressure drop for the higher stenosis may lead to misinterpretation and misdiagnosis of the stenosis severity.

  12. The pressure drop across the endotracheal tube in mechanically ventilated pediatric patients.

    PubMed

    Spaeth, Johannes; Steinmann, Daniel; Kaltofen, Heike; Guttmann, Josef; Schumann, Stefan

    2015-04-01

    During mechanical ventilation, the airway pressure (Paw) is usually monitored. However, Paw comprises the endotracheal tube (ETT)-related pressure drop (∆PETT ) and thus does not reflect the pressure in the patients' lungs. Therefore, monitoring of mechanical ventilation should be based on the tracheal pressure (Ptrach ). We systematically investigated potential factors influencing ∆PETT in pediatric ETTs. In this study, the flow-dependent pressure drop across pediatric ETTs from four manufacturers [2.0-4.5 mm inner diameter (ID)] was estimated in a physical model of the upper airways. Additionally, ∆PETT was examined with the ETTs shortened to 75% of their original length and at different curvatures. In nine healthy mechanically ventilated children (aged between 9 days and 29 months), Ptrach was compared to Paw . ∆PETT was nonlinearly flow dependent. Low IDs corresponded to high ∆PETT . Differences between ETTs from different manufacturers were identified. Shortening of the ETTs' length by 25% reduced ∆PETT on average by 14% of the value at original length. Ventilation frequency and tube curvature did not influence ∆PETT to a relevant extent. In the pediatric patients, the root mean square deviation between Paw and Ptrach was 2.3 cm H2O. Paw and Ptrach differ considerably (by ∆PETT ) during mechanical ventilation of pediatric patients. The ETTs' ID, tube length, and manufacturer type are significant factors for ∆PETT and should be taken into account when Paw is valuated. For this purpose, Ptrach can be continuously calculated with good precision by means of the Rohrer approximation. © 2014 John Wiley & Sons Ltd.

  13. Direct measurement of the differential pressure during drop formation in a co-flow microfluidic device.

    PubMed

    Xu, Ke; Tostado, Chris P; Xu, Jian-Hong; Lu, Yang-Cheng; Luo, Guang-Sheng

    2014-04-07

    In this study, we developed a new method for the direct measurement of differential pressures in a co-flow junction microfluidic device using a Capillary Laplace Gauge (CLG). The CLG - used inside the microchannel device--was designed using a tapered glass-capillary set up in co-flow junction architecture with a three-phase liquid-liquid-gas system with two flowing liquid phases and an entrained gas phase. By taking advantage of the Laplace equation, basic geometric relations and an integrated image analysis program, the movement of the entrained gas phase with the flow of the liquid-phases is tracked and monitored, allowing the gauge to function as an ultra-sensitive, integrated, differential pressure sensor measuring fluctuations in the liquid-dispersed phase channel pressure as small as tens of Pascals caused by droplet formation. The gauge was used to monitor the drop formation and breakup process in a co-flow junction microfluidic device under different flow conditions across a large range (1 × 10(-3) to 2.0 × 10(-1)) of capillary numbers. In addition to being able to monitor short and long term dispersed phase pressure fluctuation trends for both single drop and large droplet populations, the gauge was also used to clearly identify a transition between the dripping and jetting flow regimes. Overall, the combination of a unique, integrated image analysis program with this new type of sensor serves as a powerful tool with great potential for a variety of different research and industrial applications requiring sensitive microchannel pressure measurements.

  14. Pressure Drop in Tortuosity/Kinking of the Internal Carotid Artery: Simulation and Clinical Investigation

    PubMed Central

    Wang, Lijun; Zhao, Feng; Wang, Daming; Hu, Shen; Liu, Jiachun; Zhou, Zhilun; Lu, Jun; Qi, Peng; Song, Shiying

    2016-01-01

    Background. Whether carotid tortuosity/kinking of the internal carotid artery leads to cerebral ischemia remains unclear. There is very little research about the hemodynamic variation induced by carotid tortuosity/kinking in the literature. The objective of this study was to research the blood pressure changes induced by carotid tortuosity/kinking. Methods. We first created a geometric model of carotid tortuosity/kinking. Based on hemodynamic boundary conditions, the hemodynamics of carotid tortuosity and kinking were studied via a finite element simulation. Then, an in vitro system was built to validate the numerical simulation results. The mean arterial pressure changes before and after carotid kinking were measured using pressure sensors in 12 patients with carotid kinking. Results. Numerical simulation revealed that the pressure drops increased with increases in the kinking angles. Clinical tests and in vitro experiments confirmed the numerical simulation results. Conclusions. Carotid kinking leads to blood pressure reduction. In certain conditions, kinking may affect the cerebral blood supply and be associated with cerebral ischemia. PMID:27195283

  15. Pressure drop in fully developed, turbulent, liquid-vapor annular flows in zero gravity

    NASA Technical Reports Server (NTRS)

    Sridhar, K. R.; Chao, B. T.; Soo, S. L.

    1992-01-01

    The prediction of frictional pressure drop in fully developed, turbulent, annular liquid-vapor flows in zero gravity using simulation experiments conducted on earth is described. The scheme extends the authors' earlier work on dispersed flows. The simulation experiments used two immiscible liquids of identical density, namely, water and n-butyl benzoate. Because of the lack of rigorous analytical models for turbulent, annular flows, the proposed scheme resorts to existing semiempirical correlations. Results based on two different correlations are presented and compared. Others may be used. It was shown that, for both dispersed and annular flow regimes, the predicted frictional pressure gradients in 0-g are lower than those in 1-g under otherwise identical conditions. The physical basis for this finding is given.

  16. Pressure drop in fully developed, turbulent, liquid-vapor annular flows in zero gravity

    NASA Technical Reports Server (NTRS)

    Sridhar, K. R.; Chao, B. T.; Soo, S. L.

    1992-01-01

    The prediction of frictional pressure drop in fully developed, turbulent, annular liquid-vapor flows in zero gravity using simulation experiments conducted on earth is described. The scheme extends the authors' earlier work on dispersed flows. The simulation experiments used two immiscible liquids of identical density, namely, water and n-butyl benzoate. Because of the lack of rigorous analytical models for turbulent, annular flows, the proposed scheme resorts to existing semiempirical correlations. Results based on two different correlations are presented and compared. Others may be used. It was shown that, for both dispersed and annular flow regimes, the predicted frictional pressure gradients in 0-g are lower than those in 1-g under otherwise identical conditions. The physical basis for this finding is given.

  17. Two-phase pressure drop with twisted-tape swirl generators

    SciTech Connect

    Jensen, M.K.; Bensler, H.P.; Pourdoshti, M.

    1985-03-01

    An experimental study has been conducted to determine the effect of twisted-tape swirl generators on adiabatic and diabatic two-phase flow pressure drops in vertical straight tubes. Tape-twist ratios (length for 180/sup 0/ twist/inside tube diameter) of 3.94, 8.94, and 13.92 were tested with R-113 over a range of pressures, mass velocities, qualities, and heat fluxes. Empty tube reference data were successfully predicted with a correlation from the literature. The twisted tape data wer successfully correlated by using the hydraulic diameter and a single-phase swirl flow friction factor in the empty tube correlation. Data from the literature also were predicted well with this correlation.

  18. Fibrous filter efficiency and pressure drop in the viscous-inertial transition flow regime.

    SciTech Connect

    Sanchez, Andres L.; Brockmann, John E.; Dellinger, Jennifer Gwynne; Lucero, Daniel A.; Hubbard, Joshua A.; Servantes, Brandon Lee

    2011-10-01

    Fibrous filter pressure drop and aerosol collection efficiency were measured at low air pressures (0.2 to 0.8 atm) and high face velocities (5 to 20 meters per second) to give fiber Reynolds numbers in the viscous-inertial transition flow regime (1 to 16). In this regime, contemporary filtration theory based on Kuwabara's viscous flow through an ensemble of fibers under-predicts single fiber impaction by several orders of magnitude. Streamline curvature increases substantially as inertial forces become dominant. Dimensionless pressure drop measurements followed the viscous-inertial theory of Robinson and Franklin rather than Darcy's linear pressure-velocity relationship (1972). Sodium chloride and iron nano-agglomerate test aerosols were used to evaluate the effects of particle density and shape factor. Total filter efficiency collapsed when plotted against the particle Stokes and fiber Reynolds numbers. Efficiencies were then fitted with an impactor type equation where the cutpoint Stokes number and a steepness parameter described data well in the sharply increasing portion of the curve (20% to 80% efficiency). The cutpoint Stokes number was a linearly decreasing function of fiber Reynolds number. Single fiber efficiencies were calculated from total filter efficiencies and compared to contemporary viscous flow impaction theory (Stechkina et al. 1969), and numerical simulations from the literature. Existing theories under-predicted measured single fiber efficiencies although the assumption of uniform flow conditions for each successive layer of fibers is questionable; the common exponential relationship between single fiber efficiency and total filter efficiency may not be appropriate in this regime.

  19. Two-phase flow and pressure drop in flow passages of compact heat exchangers

    SciTech Connect

    Wambsganss, M.W.; Jendrzejczyk, J.A.; France, D.M.

    1992-01-01

    Two-phase flow experiments were performed with air/water mixtures in a small rectangular channel measuring 9.52 {times} 1.59 mm (aspects ratio equal to 6), for applications to compact heat exchangers. Pressure drop and flow pattern definition data were obtained over a large range of mass qualities (0.0002 to 1), and in the case of flow pattern data, a large range of mass fluxes (50 to 2,000 kg/m{sup 2}s). A flow pattern map, based on visual observations and photographs of the flow patterns, is presented and compared with a map developed for a rectangular channel of the same aspect ratio but with dimensions twice those of the test channel, and with a map developed for a circular tube with the same hydraulic diameter of 3 mm. Pressure drop data are presented as a function of both mass quality and Martinelli parameter and are compared with state-of-the-art correlations and a modified Chisholm correlation. 13 refs.

  20. Two-phase flow and pressure drop in flow passages of compact heat exchangers

    SciTech Connect

    Wambsganss, M.W.; Jendrzejczyk, J.A.; France, D.M.

    1992-02-01

    Two-phase flow experiments were performed with air/water mixtures in a small rectangular channel measuring 9.52 {times} 1.59 mm (aspects ratio equal to 6), for applications to compact heat exchangers. Pressure drop and flow pattern definition data were obtained over a large range of mass qualities (0.0002 to 1), and in the case of flow pattern data, a large range of mass fluxes (50 to 2,000 kg/m{sup 2}s). A flow pattern map, based on visual observations and photographs of the flow patterns, is presented and compared with a map developed for a rectangular channel of the same aspect ratio but with dimensions twice those of the test channel, and with a map developed for a circular tube with the same hydraulic diameter of 3 mm. Pressure drop data are presented as a function of both mass quality and Martinelli parameter and are compared with state-of-the-art correlations and a modified Chisholm correlation. 13 refs.

  1. Heat transfer and pressure drop in tube with broken twisted tape insert

    SciTech Connect

    Chang, Shyy Woei; Yang, Tsun Lirng; Liou, Jin Shuen

    2007-11-15

    An experimental study measuring the axial heat transfer distributions and the pressure drop coefficients of the tube fitted with a broken twisted tape of twist ratio 1, 1.5, 2, 2.5 or {infinity} is performed in the Re range of 1000-40,000. This type of broken twisted tape is newly invented without previous investigations available. Local Nusselt numbers and mean Fanning friction factors in the tube fitted with the broken twisted tape increase as the twist ratio decreases. Heat transfer coefficients, mean Fanning friction factors and thermal performance factors in the tube fitted with the broken twisted tape are, respectively, augmented to 1.28-2.4, 2-4.7 and 0.99-1.8 times of those in the tube fitted with the smooth twisted tape. Empirical heat transfer and pressure drop correlations which evaluate the local Nusselt number and the mean Fanning friction factor for the tube with the broken twisted tape insert are generated to assist the industrial applications. (author)

  2. Heat transfer and pressure drop in hexagonal ducts with surface dimples

    SciTech Connect

    Chang, S.W.; Chiang, K.F.; Chou, T.C.

    2010-11-15

    Measurements of detailed Nusselt number (Nu) distributions and pressure drop coefficients (f) for four hexagonal ducts with smooth and dimpled walls are performed to comparatively examine the thermal performances of three sets of dimpled walls with concave-concave, convex-convex and concave-convex configurations at Reynolds numbers (Re) in the range of 900-30,000. A set of selected experimental data illustrates the influences of dimple configuration and Re on the detailed Nu distributions, the area-averaged Nu over developed flow region (Nu-bar) and the pressure drop coefficients. Relative enhancements of Nu and f from the smooth-walled references (Nu{sub {infinity}} and f{sub {infinity}}) along with the thermal performance factor ({eta}) defined as (Nu-bar/Nu{sub {infinity}})/(f/f{sub {infinity}}){sup 1/3} are examined. Nu-bar and f correlations are individually obtained for each tested hexagonal duct using Re as the controlling parameter. (author)

  3. Prediction of pressure drop of two-phase coal slurries in pipelines

    NASA Astrophysics Data System (ADS)

    Sanghvi, S. M.; Tolan, J. S.

    1982-11-01

    Pressure drop and flow rate measurements through pipeline viscometers were analyzed using the power law, Bingham-plastic and Bowen non-Newtonian heological models in a computer program. Wall slip was corrected with Hanks' modification of the Rabinowitsch-Mooney equation. The possibility of solids settling was analyzed with the Oroskar-Turian correlation. The program relates shear stress to shear rate for Fort Lewis coal-slurry data to within 5% for flow without solids settling. Wilsonville coal-slurry data with solids settling were fit to within 17% by the Bowen model, but the Bowen parameters are very sensitive to operating conditions. Pressure drop is predicted in the program as a function of flow rate and pipe diameter, using the analysis of best-fit rheological parameters and literature correlations for friction factors. The effect of wall slip on shear stress decreased with increasing pipe diameter. A modification to the graphical criterion for turbulence was proposed that utilizes the numerical value of the slopes of the branched flow curves.

  4. The effect of longitudinal spacer ribs on the minimum pressure drop in a heated annulus

    SciTech Connect

    Johnston, B.S.; Neff, J.M.

    1990-01-01

    When evaluating a heated flow passage for vulnerability to static flow excursions, special note should be taken of flow restrictions which might allow premature vapor generation. In this study, measurements of steady state pressure drop were made for the downward flow of water in a vertical annulus. The outer wall was uniformly heated to allow subcooled boiling. Minima in the pressure drop characteristics were compared for test sections with and without longitudinal spacer ribs. For a given power and inlet temperature, the minimum occurred at a higher flow rate in the ribbed test section. This is attributed to vapor generation at the ribs. The work cited in this document show how a restriction in a heated channel can produce vapor which would not be observed in the absence of the restriction. In the present study, the effect of a flow restriction on the tendency to flow excursion is explored by finding demand curves for a heated annulus in subcooled boiling flow. The annulus is heated from the outside, and alternately equipped with and without longitudinal spacer ribs. These ribs separate the heated and unheated walls; in pressing against the heated wall they provide a means for premature vapor production.

  5. Investigation of the different base fluid effects on the nanofluids heat transfer and pressure drop

    NASA Astrophysics Data System (ADS)

    Bayat, Javad; Nikseresht, Amir Hossein

    2011-09-01

    A numerical study of laminar forced convective flows of three different nanofluids through a horizontal circular tube with a constant heat flux condition has been performed. The effect of Al2O3 volume concentration 0 ≤ φ ≤ 0.09 in the pure water, water-ethylene glycol mixture and pure ethylene glycol as base fluids, and Reynolds number of 100 ≤ Re ≤ 2,000 for different power inputs in the range of 10 ≤ Q( W) ≤ 400 have been investigated. In this study, all of the nanofluid properties are temperature and nanoparticle volume concentration dependent. The governing equations have been solved using finite volume approach with the SIMPLER algorithm. The results indicate an increase in the averaged heat transfer coefficient with increasing the mass of ethylene glycol in the water base fluid, solid concentration and Reynolds number. From the investigations it can be inferred that, the pressure drop and pumping power in the nanofluids at low solid volumetric concentration (φ < 3%) is approximately the same as in the pure base fluid in the various Reynolds numbers, but the higher solid nanoparticle volume concentration causes a penalty drop in the pressure. Moreover, this study shows it is possible to achieve a higher heat transfer rate with lower wall shear stress with the use of proper nanofluids.

  6. Nuclear Power Plant Containment Pressure Boundary Research

    SciTech Connect

    Cherry, J.L.; Chokshi, N.C.; Costello, J.F.; Ellingwood, B.R.; Naus, D.J.

    1999-09-15

    Research to address aging of the containment pressure boundary in light-water reactor plants is summarized. This research is aimed at understanding the significant factors relating occurrence of corrosion, efficacy of inspection, and structural capacity reduction of steel containment and liners of concrete containment. This understanding will lead to improvements in risk-informed regulatory decision making. Containment pressure boundary components are described and potential aging factors identified. Quantitative tools for condition assessments of aging structures to maintain an acceptable level of reliability over the service life of the plant are discussed. Finally, the impact of aging (i.e., loss of shell thickness due to corrosion) on steel containment fragility for a pressurized water reactor ice-condenser plant is presented.

  7. Heat transfer and pressure drop measurement in wavy channels with flow disturbers

    SciTech Connect

    Dini, S.; Veronesi, R.; Hryniewicz, E.V.

    1999-07-01

    In the current work, the transient method was employed to obtain the local heat transfer coefficient for a 6 in. x 3/8 in. x 12 in. (15.24cm x .9525cm x 30.48cm) Plexiglas {reg_sign} wavy channel with and without flow disturbers. A short duration transient test was performed to measure the heat transfer coefficient by introducing heated air over test specimen that had been sprayed with calibrated thermochromic liquid crystals. This technique allowed the experimenter to observe the temperature changes using a video camera. because a Plexiglas surface has a low thermal diffusivity, a one-dimensional assumption is a reasonable approximation because the surface temperature response is limited to a thin layer near the surface and lateral conduction is small. The heat transfer coefficient using the transient technique is then determined from the response of the surface temperature to a step change in the local temperature. Using this method, the axial variation in the heat transfer coefficient for Reynolds numbers in the laminar (1100) and turbulent region (2900) were obtained. These Reynolds numbers were based on the hydraulic diameter at the inlet of the wavy channel. Also, in this investigation, the region of greatest heat transfer and the pressure drop were both experimentally and analytically determined and the friction factor across an in-phase corrugated wall channel (wavy channel) at Reynolds numbers of 1100 and 2900 were obtained. A manometer and a pressure transducer were employed to measure pressure drop across the channel. The effect of flow disturbers mounted on each peak, alternate peaks and the first six peaks of a twelve-peak channel were also investigated. For all cases, the pressure drop and friction factor were shown to moderately increase with rib placement in the test section when compared to the results obtained from a similar smooth wavy channel without ribs. Additionally, for all cases, the friction factor also decreased with an increase in the

  8. An improved method for simultaneous determination of frictional pressure drop and vapor volume fraction in vertical flow boiling

    NASA Technical Reports Server (NTRS)

    Klausner, J. F.; Chao, B. T.; Soo, S. L.

    1990-01-01

    The two-phase frictional pressure drop and vapor volume fraction in the vertical boiling and adiabatic flow of the refrigerant, R11, have been simultaneously measured by a liquid balancing column and differential magnetic reluctance pressure transducers. An account is given of the experimental apparatus and procedure, data acquisition and analysis, and error estimation employed. All values of two-phase multipliers evaluated on the basis of the measured frictional pressure drop data in vertical upflow fall in the range bounded by the predictions of the Chisholm correlation and the homogeneous model.

  9. Pressure, temperature and density drops along supercritical fluid chromatography columns. I. Experimental results for neat carbon dioxide and columns packed with 3- and 5-micron particles.

    PubMed

    Poe, Donald P; Veit, Devon; Ranger, Megan; Kaczmarski, Krzysztof; Tarafder, Abhijit; Guiochon, Georges

    2012-08-10

    The pressure drop and temperature drop on columns packed with 3- and 5-micron particles were measured using neat CO(2) at a flow rate of 5 mL/min, at temperatures from 20°C to 100°C, and outlet pressures from 80 to 300 bar. The density drop was calculated based on the temperature and pressure at the column inlet and outlet. The columns were suspended in a circulating air bath either bare or covered with foam insulation. The results show that the pressure drop depends on the outlet pressure, the operating temperature, and the thermal environment. A temperature drop was observed for all conditions studied. The temperature drop was relatively small (less than 3°C) for combinations of low temperature and high pressure. Larger temperature drops and density drops occurred at higher temperatures and low to moderate pressures. Covering the column with thermal insulation resulted in larger temperature drops and corresponding smaller density drops. At 20°C the temperature drop was never more than a few degrees. The largest temperature drops occurred for both columns when insulated at 80°C and 80 bar, reaching a maximum value of 21°C for the 5-micron column, and 26°C for the 3-micron column. For an adiabatic column, the temperature drop depends on the pressure drop, the thermal expansion coefficient, and the density and the heat capacity of the mobile phase fluid, and can be described by a simple mathematical relationship. For a fixed operating temperature and outlet pressure, the temperature drop increases monotonically with the pressure drop.

  10. Modeling pressure drop using generalized scaffold characteristics in an axial-flow bioreactor for soft tissue regeneration.

    PubMed

    Podichetty, Jagdeep T; Bhaskar, Prasana R; Khalf, Abdurizzagh; Madihally, Sundararajan V

    2014-06-01

    The goal of this study was to better understand how analytical permeability models based on scaffold architecture can facilitate a non-invasive technique to real time monitoring of pressure drop in bioreactors. In particular, we evaluated the permeability equations for electrospun and freeze dried scaffolds via pressure drop comparison in an axial-flow bioreactor using computational fluid dynamic (CFD) and experimentation. The polycaprolactone-cellulose acetate fibers obtained by co-axial electrospinning technique and Chitosan-Gelatin scaffolds prepared using freeze-drying techniques were utilized. Initially, the structural properties (fiber size, pore size and porosity) and mechanical properties (elastic modulus and Poisson's ratio) of scaffolds in phosphate buffered saline at 37 °C were evaluated. The CFD simulations were performed by coupling fluid flow, described by Brinkman equation, with structural mechanics using a moving mesh. The experimentally obtained pressure drop values for both 1 mm thick and 2 mm thick scaffolds agreed with simulation results. To evaluate the effect of permeability and elastic modulus on pressure drop, CFD predictions were extended to a broad range of permeabilities spanning synthetic scaffolds and tissues, elastic moduli, and Poisson's ratio. Results indicated an increase in pressure drop with increase in permeability. Scaffolds with higher elastic modulus performed better and the effect of Poisson's ratio was insignificant. Flow induced deformation was negligible in axial-flow bioreactor. In summary, scaffold permeabilities can be calculated using scaffold microarchitecture and can be used in non-invasive monitoring of tissue regeneration.

  11. Effect of nonionic surfactant on wetting behavior of an evaporating drop under a reduced pressure environment.

    PubMed

    Sefiane, Khellil

    2004-04-15

    The evaporation of sessile drops at reduced pressure is investigated. The evaporation of water droplets on aluminum and PTFE surfaces at reduced pressure was compared. It was found that water droplets on an aluminum surface exhibit a 'depinning jump' at subatmospheric pressures. This is when a pinned droplet suddenly depins, with an increase in contact angle and a simultaneous decrease in the base width. The evaporation of sessile water droplets with a nonionic surfactant (Triton X-100) added to an aluminum surface was then studied. The initial contact angle exhibited a minimum at 0.001 wt% Triton X-100. A maximum in the evaporation rate was also observed at the same concentration. Droplets with low surfactant concentrations are found to exhibit the 'depinning jump.' It is thought that the local concentration of the surfactant causes a gradient of surface tension. The balance at the contact angle is dictated by complex phenomena, including surfactant diffusion and adsorption processes at interfaces. Due to the strong evaporation near the triple line, an accumulation of the surfactant will lead to a surface tension gradient along the interface. The gradient of surface tension will influence the wetting behavior (Marangoni effect). At low surfactant concentrations the contact line depins under the strong effect of surface tension gradient that develops spontaneously over the droplet interface due to surfactant accumulation near the triple line. The maximum evaporation rate corresponds to a minimum contact angle for a pinned droplet.

  12. Heat exchange effectiveness and pressure drop for air flow through perforated plates with and without crosswind

    NASA Astrophysics Data System (ADS)

    Kutscher, C. F.

    1994-05-01

    Low-porosity perforated plates are being used as absorbers for heating ambient air in a new type of unglazed solar collector. This paper investigates the convective heat transfer effectiveness for low-speed air flow through thin, isothermal perforated plates with and without a crosswind on the upstream face. The objective of this work is to provide information that will allow designers to optimize hole size and spacing. In order to obtain performance data, a wind tunnel and small lamp array were designed and built. Experimental data were taken for a range of plate porosities from 0.1 to 5 percent, hole Reynolds numbers from 100 to 2000, and wind speeds from 0 to 4 m/s. Correlations were developed for heat exchange effectiveness and also for pressure drop. Infrared thermography was used to visualize the heat transfer taking place at the surface.

  13. Two-phase pressure drop across a hydrofoil-based micro pin device using R-123

    SciTech Connect

    Kosar, Ali

    2008-05-15

    The two-phase pressure drop in a hydrofoil-based micro pin fin heat sink has been investigated using R-123 as the working fluid. Two-phase frictional multipliers have been obtained over mass fluxes from 976 to 2349 kg/m{sup 2} s and liquid and gas superficial velocities from 0.38 to 1.89 m/s and from 0.19 to 24 m/s, respectively. It has been found that the two-phase frictional multiplier is strongly dependent on flow pattern. The theoretical prediction using Martinelli parameter based on the laminar fluid and laminar gas flow represented the experimental data fairly well for the spray-annular flow. For the bubbly and wavy-intermittent flow, however, large deviations from the experimental data were recorded. The Martinelli parameter was successfully used to determine the flow patterns, which were bubbly, wavy-intermittent, and spray-annular flow in the current study. (author)

  14. Pressure Drop in Cold Water Flow in Beds Packed with Several Kinds of Crushed Ice.

    NASA Astrophysics Data System (ADS)

    Yanadori, Michio; Ohira, Akiyoshi

    This paper deals with the pressure drop in cold water flow in the beds packed with crushed ice. 1n each case, ice-packed beds were filled with sevral kinds of crushed ice, and friction-loss coefficients were examined. The following results were obtained. (1) The friction factor of rectangular-type ice-packed beds is smaller than that of ideal sphere beds by about 1/4 to 1/2. (2) The friction factor of small-stone-type ice-packed beds is about twice as large as that of ideal sphere beds. (3) It is difficult to compare the flow model of water in restricted channel of particle-type ice-packed beds with that of ideal packed beds.

  15. Preliminary investigation of labyrinth packing pressure drops at onset of swirl-induced rotor instability

    NASA Technical Reports Server (NTRS)

    Miller, E. H.; Vohr, J. H.

    1984-01-01

    Backward and forward subsynchronous instability was observed in a flexible model test rotor under the influence of swirl flow in a straight-through labyrinth packing. The packing pressure drop at the onset of instability was then measured for a range of operating speeds, clearances and inlet swirl conditions. The trend in these measurements for forward swirl and forward instability is generally consistent with the short packing rotor force formulations of Benchert and Wachter. Diverging clearances were also destabilizing and had a forward orbit with forward swirl and a backward orbit with reverse swirl. A larger, stiff rotor model system is now being assembled which will permit testing steam turbine-type straight-through and hi-lo labyrinth packings. With calibrated and adjustable bearings in this new apparatus, direct measure of the net destabilizing force generated by the packings can be made.

  16. Nonisothermal motion of an elastoviscoplastic medium through a pipe under a changing pressure drop

    NASA Astrophysics Data System (ADS)

    Burenin, A. A.; Kovtanyuk, L. V.; Panchenko, G. L.

    2015-09-01

    The solution of a sequence of coupled problems of thermoelastic plasticity on the nucleation and development of medium flow in a cylindrical pipe in conditions of varying pressure drop and material heating due to friction on the pipe wall and subsequent stagnation of flow under slow load removal and cooling of the layer material is derived based on the theory of large elastoplastic deformations generalized for the nonisothermal case. The thermal and deformation processes are interrelated with the temperature dependence of the yield point. The conditions of nucleation of the viscoplastic flow and regularities of motion of the elastoplastic boundaries over the layer are noted, and the flow rates and large strains, both irreversible and reversible, are calculated.

  17. Flow pattern and pressure drop of vertical upward gas-liquid flow in sinusoidal wavy channels

    SciTech Connect

    Nilpueng, Kitti; Wongwises, Somchai

    2006-06-15

    Flow patterns and pressure drop of upward liquid single-phase flow and air-water two-phase flow in sinusoidal wavy channels are experimentally studied. The test section is formed by a sinusoidal wavy wall of 1.00 m length with a wave length of 67.20mm, an amplitude of 5.76mm. Different phase shifts between the side walls of the wavy channel of 0{sup o}, 90{sup o} and 180{sup o} are investigated. The flow phenomena, which are bubbly flow, slug flow, churn flow, and dispersed bubbly flow are observed and recorded by high-speed camera. When the phase shifts are increased, the onset of the transition from the bubbly flow to the churn flow shifts to a higher value of superficial air velocity, and the regions of the slug flow and the churn flow are smaller. In other words, the regions of the bubbly flow and the dispersed bubbly flow are larger as the phase shift increases. The slug flow pattern is only found in the test sections with phase shifts of 0{sup o} and 90{sup o}. Recirculating gas bubbles are always found in the troughs of the corrugations. The recirculating is higher when the phase shifts are larger. The relationship between the two-phase multipliers calculated from the measured pressure drops, and the Martinelli parameter is compared with the Lockhart-Martinelli correlation. The correlation in the case of turbulent-turbulent condition is shown to fit the data very well for the phase shift of 0{sup o} but shows greater deviation when the phase shifts are higher. (author)

  18. Coupled degassing and crystallization: experimental study at continuous pressure drop, with application to volcanic bombs

    NASA Astrophysics Data System (ADS)

    Simakin, Alexander G.; Armienti, Pietro; Epel'baum, M. B.

    Experiments on degassing of water-saturated granite melts with a pressure drop from 100 and 450MPa to 40 and 120MPa, respectively, at temperatures close to feldspar liquidus (750-700 °C), were carried out to determine the modality of water exsolution and vesicle formation at the liquidus temperature. Pressure-drop rates as small as approximately 100bar/day were used. Uniform space distributions of bubbles of exsolved water were obtained with starting glass containing a small fraction ( 0.5vol.%) of trapped air bubbles. Volume crystallization of feldspar was observed in degassed melts supplied with seeds. Bubble size distributions (BSD) measured in granite glasses after degassing are presented. Data on vesicle characteristics (number, radius, area, elongation) were acquired on images digitized with standard software, while the reconstruction of size distributions was performed with the Schwartz-Saltikov "unfolding" procedure. Bubble size distributions of size classes in the range 5-1000μm were acquired with proper magnification and satisfactory statistical reliability of determined number densities. The BSDs of the experimental samples are compared with the results of measurements of rapidly degassed products of Mt. Etna and Vulcano Island. Many particular features of the bubble nucleation and growth can be distinguished in an individual BSD. However, the general BSD of the whole data set, including natural ones, can be relatively well described with linear regression in bilogarithmic coordinates. The slope of this regression is approximately 2.8+/-0.1. This dependence is in striking contrast with distributions theoretically predicted with classical nucleation models based on homogeneous nucleation of vesicles. The theoretical distribution requires the occurrence of strong maxima that are not observed in our experimental and natural samples, thus arguing for heterogeneous nucleation mechanisms.

  19. A Fast Air-dry Dropping Chromosome Preparation Method Suitable for FISH in Plants.

    PubMed

    Aliyeva-Schnorr, Lala; Ma, Lu; Houben, Andreas

    2015-12-16

    Preparation of chromosome spreads is a prerequisite for the successful performance of fluorescence in situ hybridization (FISH). Preparation of high quality plant chromosome spreads is challenging due to the rigid cell wall. One of the approved methods for the preparation of plant chromosomes is a so-called drop preparation, also known as drop-spreading or air-drying technique. Here, we present a protocol for the fast preparation of mitotic chromosome spreads suitable for the FISH detection of single and high copy DNA probes. This method is an improved variant of the air-dry drop method performed under a relative humidity of 50%-55%. This protocol comprises a reduced number of washing steps making its application easy, efficient and reproducible. Obvious benefits of this approach are well-spread, undamaged and numerous metaphase chromosomes serving as a perfect prerequisite for successful FISH analysis. Using this protocol we obtained high-quality chromosome spreads and reproducible FISH results for Hordeum vulgare, H. bulbosum, H. marinum, H. murinum, H. pubiflorum and Secale cereale.

  20. Cloud modification by man-made pollutants: Effects of a coal-fired power plant on cloud drop spectra

    NASA Astrophysics Data System (ADS)

    Pueschel, R. F.; Barrett, E. W.; Wellman, D. L.; McGuire, J. A.

    1981-03-01

    Pollutants from coal-fired power plants increase the drop modal radii and broaden the drop spectra of stratocumulus clouds. Additional water from the coal combustion leads to a measurable increase of the liquid water content of polluted clouds. Implied consequences are an increase of the coalescence efficiency, and an increase in acidity, of affected clouds.

  1. Boiling Heat Transfer and Pressure Drop of a Refrigerant Flowing Vertically Downward in a Small Diameter Tube

    NASA Astrophysics Data System (ADS)

    Miyata, Kazushi; Mori, Hideo; Ohishi, Katsumi; Tanaka, Hirokazu

    Experiments were performed on boiling heat transfer and pressure drop of a refrigerant R410A flowing vertically downward in a copper smooth tube of 1.0 mm inside diameter for the development of a high-performance heat exchanger using small diameter tubes for air conditioning systems. Local heat transfer coefficients were measured in a range of mass fluxes from 30 to 200 kg/(m2•s), heat fluxes from 1 to 16 kW/m2 and quality from 0.1 to over 1 at evaporation temperature of 10°C. Pressure drops were measured and flow patterns were observed at mass fluxes from 30 to 200 kg/(m2•s) and quality from 0.1 to 0.9. The characteristics of frictional pressure drop, heat transfer coefficient and dryout qualities were clarified by comparing the measurements with the data for the vertically upward flow previously obtained.

  2. Experimental study on the flow patterns and the two-phase pressure drops in a horizontal impacting T-Junction

    NASA Astrophysics Data System (ADS)

    Bertani, C.; Malandrone, M.; Panella, B.

    2014-04-01

    The present paper analyzes the experimental results concerning the flow patterns and pressure drops in two-phase flow through a horizontal impacting T-junction, whose outlet pipes are aligned and perpendicular to the inlet pipe. The test section consists of plexiglass pipes with inner diameter of 10 mm. A mixture of water and air at ambient temperature and pressures up to 2.4 bar flows through the T-junction, with different splitting of flow rates in the two outlet branches; superficial velocities of air and water in the inlet pipe have been varied up to a maximum of 35 m/s and 3.5 m/s respectively. The flow patterns occurring in the inlet and branch pipes are compared with the predictions of the Baker and Taitel - Dukler maps. The pressure drops along the branches have been measured relatively to different splitting of the flow rate through the two branches and the pressure loss coefficients in the junction have been evaluated. Friction pressure drops have allowed us to evaluate two-phase friction multipliers, which have then been compared to the predictions of Lockhart-Martinelli, and Friedel correlations. Local pressure drops have been extrapolated at the junction centre and analyzed; the two-phase multiplier has been evaluated and compared with the predictions of Chisholm correlation; the value of the empirical coefficient that minimizes the discrepancy has also been evaluated.

  3. High-Pressure Transport Properties Of Fluids: Theory And Data From Levitated Drops At Combustion-Relevant Temperatures

    NASA Technical Reports Server (NTRS)

    Bellan, Josette; Harstad, Kenneth; Ohsaka, Kenichi

    2003-01-01

    Although the high pressure multicomponent fluid conservation equations have already been derived and approximately validated for binary mixtures by this PI, the validation of the multicomponent theory is hampered by the lack of existing mixing rules for property calculations. Classical gas dynamics theory can provide property mixing-rules at low pressures exclusively. While thermal conductivity and viscosity high-pressure mixing rules have been documented in the literature, there is no such equivalent for the diffusion coefficients and the thermal diffusion factors. The primary goal of this investigation is to extend the low pressure mixing rule theory to high pressures and validate the new theory with experimental data from levitated single drops. The two properties that will be addressed are the diffusion coefficients and the thermal diffusion factors. To validate/determine the property calculations, ground-based experiments from levitated drops are being conducted.

  4. Comparison of pressure drop and filtration efficiency of particulate respirators using welding fumes and sodium chloride.

    PubMed

    Cho, Hyun-Woo; Yoon, Chung-Sik; Lee, Jin-Ho; Lee, Seung-Joo; Viner, Andrew; Johnson, Erik W

    2011-07-01

    Respirators are used to help reduce exposure to a variety of contaminants in workplaces. Test aerosols used for certification of particulate respirators (PRs) include sodium chloride (NaCl), dioctyl phthalate, and paraffin oil. These aerosols are generally assumed to be worst case surrogates for aerosols found in the workplace. No data have been published to date on the performance of PRs with welding fumes, a hazardous aerosol that exists in real workplace settings. The aim of this study was to compare the performance of respirators and filters against a NaCl aerosol and a welding fume aerosol and determine whether or not a correlation between the two could be made. Fifteen commercial PRs and filters (seven filtering facepiece, two replaceable single-type filters, and six replaceable dual-type filters) were chosen for investigation. Four of the filtering facepiece respirators, one of the single-type filters, and all of the dual-type filters contained carbon to help reduce exposure to ozone and other vapors generated during the welding process. For the NaCl test, a modified National Institute for Occupational Safety and Health protocol was adopted for use with the TSI Model 8130 automated filter tester. For the welding fume test, welding fumes from mild steel flux-cored arcs were generated and measured with a SIBATA filter tester (AP-634A, Japan) and a manometer in the upstream and downstream sections of the test chamber. Size distributions of the two aerosols were measured using a scanning mobility particle sizer. Penetration and pressure drop were measured over a period of aerosol loading onto the respirator or filter. Photos and scanning electron microscope images of clean and exposed respirators were taken. The count median diameter (CMD) and mass median diameter (MMD) for the NaCl aerosol were smaller than the welding fumes (CMD: 74 versus 216 nm; MMD: 198 versus 528 nm, respectively). Initial penetration and peak penetration were higher with the NaCl aerosol

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

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

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

  6. Characterization of interfacial waves and pressure drop in horizontal oil-water core-annular flows

    NASA Astrophysics Data System (ADS)

    Tripathi, Sumit; Tabor, Rico F.; Singh, Ramesh; Bhattacharya, Amitabh

    2017-08-01

    We study the transportation of highly viscous furnace-oil in a horizontal pipe as core-annular flow (CAF) using experiments. Pressure drop and high-speed images of the fully developed CAF are recorded for a wide range of flow rate combinations. The height profiles (with respect to the centerline of the pipe) of the upper and lower interfaces of the core are obtained using a high-speed camera and image analysis. Time series of the interface height are used to calculate the average holdup of the oil phase, speed of the interface, and the power spectra of the interface profile. We find that the ratio of the effective velocity of the annular fluid to the core velocity, α , shows a large scatter. Using the average value of this ratio (α =0.74 ) yields a good estimate of the measured holdup for the whole range of flow rate ratios, mainly due to the low sensitivity of the holdup ratio to the velocity ratio. Dimensional analysis implies that, if the thickness of the annular fluid is much smaller than the pipe radius, then, for the given range of parameters in our experiments, the non-dimensional interface shape, as well as the non-dimensional wall shear stress, can depend only on the shear Reynolds number and the velocity ratio. Our experimental data show that, for both lower and upper interfaces, the normalized power spectrum of the interface height has a strong dependence on the shear Reynolds number. Specifically, for low shear Reynolds numbers, interfacial modes with large wavelengths dominate, while, for large shear Reynolds numbers, interfacial modes with small wavelengths dominate. Normalized variance of the interface height is higher at lower shear Reynolds numbers and tends to a constant with increasing shear Reynolds number. Surprisingly, our experimental data also show that the effective wall shear stress is, to a large extent, proportional to the square of the core velocity. Using the implied scalings for the holdup ratio and wall shear stress, we can derive

  7. The transmission of gas pressure to xylem fluid pressure when plants are inside a pressure bomb.

    PubMed

    Wei, C; Tyree, M T; Bennink, J P

    2000-02-01

    In earlier work tobacco leaves were placed in a Scholander-Hammel pressure bomb and the end of the petiole sealed with a pressure transducer in order to measure pressure transmission from the compressed gas (Pg) in the bomb to the xylem fluid (Px). Pressure bomb theory would predict a 1:1 relationship for Pg:Px when tobacco leaves start at a balance pressure of zero. Failure to observe the expected 1:1 relationship has cast doubt on the pressure-bomb technique in the measurement of the xylem pressure of plants. The experimental and theoretical relationship between Px and Pg was investigated in Tsuga canadensis (L) branches and Nicotiana rustica (L) leaves in this paper. It is concluded that the non 1:1 outcome was due to the compression of air bubbles in embolized xylem vessels, evaporation of water from the tissue, and the expansion of the sealed stem segment (or petiole) protruding beyond the seal of the pressure bomb. The expected 1:1 relationship could be obtained when xylem embolism was eliminated and stem expansion prevented. It is argued that the non 1:1 relationship in the positive pressure range does not invalidate the Scholander pressure bomb method of measuring xylem pressure in plants because Px never reaches positive values during the determination of the balance pressure.

  8. Two-phase heat transfer and pressure drop of LNG during saturated flow boiling in a horizontal tube

    NASA Astrophysics Data System (ADS)

    Chen, Dongsheng; Shi, Yumei

    2013-12-01

    Two-phase heat transfer and pressure drop of LNG (liquefied natural gas) have been measured in a horizontal smooth tube with an inner diameter of 8 mm. The experiments were conducted at inlet pressures from 0.3 to 0.7 MPa with a heat flux of 8-36 kW m-2, and mass flux of 49.2-201.8 kg m-2 s-1. The effect of vapor quality, inlet pressure, heat flux and mass flux on the heat transfer characteristic are discussed. The comparisons of the experimental data with the predicted value by existing correlations are analyzed. Zou et al. (2010) correlation shows the best accuracy with 24.1% RMS deviation among them. Moreover four frictional pressure drop methods are also chosen to compare with the experimental database.

  9. Boiling Heat Transfer and Pressure Drop of a Refrigerant Flowing Vertically Upward in a Small Diameter Tube

    NASA Astrophysics Data System (ADS)

    Miyata, Kazushi; Mori, Hideo; Ohishi, Katsumi; Tanaka, Hirokazu

    In the present study, experiments were performed to examine characteristics of flow boiling heat transfer and pressure drop of a refrigerant R410A flowing vertically upward in a copper smooth tube with 1.0 mm inside diameter for the development of a high-performance heat exchanger using small diameter tubes for air conditioning systems. Local heat transfer coefficients were measured in a range of mass fluxes from 30 to 200 kg/(m2•s), heat fluxes from 1 to 16 kW/m2 and qualities from 0.1 to over 1 at evaporation temperature of 10°C, and pressure drops were also measured at mass fluxes of 100 and 200 kg/(m2•s) and qualities from 0.1 to 0.9. Three types of flow pattern were observed in the tube: A slug, a slug-annular and an annular flow. Based on the measurements, the characteristics of frictional pressure drop, heat transfer coefficient and dryout qualities were clarified. The measured pressure drop and heat transfer coefficient were compared with correlations.

  10. Influence of Peer Pressure on Secondary School Students Drop out in Rongo Sub-County, Migori County, Kenya

    ERIC Educational Resources Information Center

    Omollo, Atieno Evaline; Yambo, Onyango J. M.

    2017-01-01

    The purpose of this study was to establish the influence of peer pressure on secondary school students' drop out in Rongo Sub-County, Migori County, Kenya. The statement of the problem showed that the sub-county had a dropout rate of 43 percent as compared to the neighboring sub counties like Uriri, Awendo, Nyatike, Kuria and Migori which had 25,…

  11. Two-Phase Pressure Drop in a Twisted Tape Boiler for a Microgravity Rankine Cycle Power System

    NASA Astrophysics Data System (ADS)

    Oinuma, Ryoji; Bean, David; Neill, Charles; Supak, Kevin; Best, Frederick

    2006-01-01

    A once-through type boiler with twisted tape inserts has been proposed for a Rankine cycle power system in space since the 1960s. However, information regarding fluid dynamics such as pressure drop in the boiler is not established well. As a fundamental study of the system characteristics, adiabatic two-phase pressure drop is measured over the range of 0 to 175.4 kg/m2s for water and 0 to 25.4 kg/m2s for air and is compared using the Homogeneous model and correlations of two-phase multipliers. The Homogeneous model and the Lockhart-Martinelli correlations predict by 30 % of the experimental results. The Friedel correlation predicts much higher values and the Jensen correlation predicts much lower values. Flow regimes for each test point are observed by a high speed camera. To evaluate the diabatic pressure drop, a heat exchanger with a twisted tape insert is designed. R-11 is used as a working fluid and boiler is heated with hot water. For the diabatic pressure drop, the values predicted by the Homogeneous model are approximately 30% lower than the experimental results.

  12. In Situ Measurement, Characterization, and Modeling of Two-Phase Pressure Drop Incorporating Local Water Saturation in PEMFC Gas Channels

    NASA Astrophysics Data System (ADS)

    See, Evan J.

    Proton Exchange Membrane Fuel Cells (PEMFCs) have been an area of focus as an alternative for internal combustion engines in the transportation sector. Water and thermal management techniques remain as one of the key roadblocks in PEMFC development. The ability to model two-phase flow and pressure drop in PEMFCs is of significant importance to the performance and optimization of PEMFCs. This work provides a perspective on the numerous factors that affect the two-phase flow in the gas channels and presents a comprehensive pressure drop model through an extensive in situ fuel cell investigation. The study focused on low current density and low temperature operation of the cell, as these conditions present the most challenging scenario for water transport in the PEMFC reactant channels. Tests were conducted using two PEMFCs that were representative of the actual full scale commercial automotive geometry. The design of the flow fields allowed visual access to both cathode and anode sides for correlating the visual observations to the two-phase flow patterns and pressure drop. A total of 198 tests were conducted varying gas diffusion layer (GDL), inlet humidity, current density, and stoichiometry; this generated over 1500 average pressure drop measurements to develop and validate two-phase models. A two-phase 1+1 D modeling scheme is proposed that incorporates an elemental approach and control volume analysis to provide a comprehensive methodology and correlation for predicting two-phase pressure drop in PEMFC conditions. Key considerations, such as condensation within the channel, consumption of reactant gases, water transport across the membrane, and thermal gradients within the fuel cell, are reviewed and their relative importance illustrated. The modeling scheme is shown to predict channel pressure drop with a mean error of 10% over the full range of conditions and with a mean error of 5% for the primary conditions of interest. The model provides a unique and

  13. Heat transfer and pressure drop characteristics of nanofluids in a plate heat exchanger.

    PubMed

    Kwon, Y H; Kim, D; Li, C G; Lee, J K; Hong, D S; Lee, J G; Lee, S H; Cho, Y H; Kim, S H

    2011-07-01

    In this paper, the heat transfer characteristics and pressure drop of the ZnO and Al2O3 nanofluids in a plate heat exchanger were studied. The experimental conditions were 100-500 Reynolds number and the respective volumetric flow rates. The working temperature of the heat exchanger was within 20-40 degrees C. The measured thermophysical properties, such as thermal conductivity and kinematic viscosity, were applied to the calculation of the convective heat transfer coefficient of the plate heat exchanger employing the ZnO and Al2O3 nanofluids made through a two-step method. According to the Reynolds number, the overall heat transfer coefficient for 6 vol% Al2O3 increased to 30% because at the given viscosity and density of the nanofluids, they did not have the same flow rates. At a given volumetric flow rate, however, the performance did not improve. After the nanofluids were placed in the plate heat exchanger, the experimental results pertaining to nanofluid efficiency seemed inauspicious.

  14. Heat transfer and pressure drop in blade cooling channels with turbulence promoters

    NASA Technical Reports Server (NTRS)

    Han, J. C.; Park, J. S.; Lei, C. K.

    1984-01-01

    Repeated rib roughness elements have been used in advanced turbine cooling designs to enhance the internal heat transfer. Often the ribs are perpendicular to the main flow direction so that they have an angle-of-attack of 90 deg. The objective of the project was to investigate the effect of rib angle-of-attack on the pressure drop and the average heat transfer coefficients in a square duct with two opposite rib-roughned walls for Reynolds number varied from 8000 to 80,000. The rib height-to-equivalent diameter ratio (e/D) was kept at a constant value of 0.063, the rib pitch-to-height ratio (P/e) was varied from 10 to 20, and the rib angle-of-attack (alpha) was varied from 90 deg to 60 deg to 45 deg to 30 deg respectively. Two types of entrance conditions were examined, namely, long duct and sudden contraction. The heat transfer coefficient distribution on the smooth side wall and the rough side wall at the entrance and the fully developed regions were measured. Thermal performance comparison indicated that the pumping power requirement for the rib with an oblique angle to the flow (alpha = 45 deg to 30 deg) was about 20 to 50 percent lower than the rib with a 90 deg angle to the flow for a given heat transfer duty.

  15. Measurement of heat transfer and pressure drop in rectangular channels with turbulence promoters

    NASA Technical Reports Server (NTRS)

    Han, J. C.; Park, J. S.; Ibrahim, M. Y.

    1986-01-01

    Periodic rib turbulators were used in advanced turbine cooling designs to enhance the internal heat transfer. The objective of the present project was to investigate the combined effects of the rib angle of attack and the channel aspect ratio on the local heat transfer and pressure drop in rectangular channels with two opposite ribbed walls for Reynolds number varied from 10,000 to 60,000. The channel aspect ratio (W/H) was varied from 1 to 2 to 4. The rib angle of attack (alpha) was varied from 90 to 60 to 45 to 30 degree. The highly detailed heat transfer coefficient distribution on both the smooth side and the ribbed side walls from the channel sharp entrance to the downstream region were measured. The results showed that, in the square channel, the heat transfer for the slant ribs (alpha = 30 -45 deg) was about 30% higher that of the transverse ribs (alpha = 90 deg) for a constant pumping power. However, in the rectangular channels (W/H = 2 and 4, ribs on W side), the heat transfer at alpha = 30 -45 deg was only about 5% higher than 90 deg. The average heat transfer and friction correlations were developed to account for rib spacing, rib angle, and channel aspect ratio over the range of roughness Reynolds number.

  16. Antimicrobial nanoparticle-coated electrostatic air filter with high filtration efficiency and low pressure drop.

    PubMed

    Sim, Kyoung Mi; Park, Hyun-Seol; Bae, Gwi-Nam; Jung, Jae Hee

    2015-11-15

    In this study, we demonstrated an antimicrobial nanoparticle-coated electrostatic (ES) air filter. Antimicrobial natural-product Sophora flavescens nanoparticles were produced using an aerosol process, and were continuously deposited onto the surface of air filter media. For the electrostatic activation of the filter medium, a corona discharge electrification system was used before and after antimicrobial treatment of the filter. In the antimicrobial treatment process, the deposition efficiency of S. flavescens nanoparticles on the ES filter was ~12% higher than that on the pristine (Non-ES) filter. In the evaluation of filtration performance using test particles (a nanosized KCl aerosol and submicron-sized Staphylococcus epidermidis bioaerosol), the ES filter showed better filtration efficiency than the Non-ES filter. However, antimicrobial treatment with S. flavescens nanoparticles affected the filtration efficiency of the filter differently depending on the size of the test particles. While the filtration efficiency of the KCl nanoparticles was reduced on the ES filter after the antimicrobial treatment, the filtration efficiency was improved after the recharging process. In summary, we prepared an antimicrobial ES air filter with >99% antimicrobial activity, ~92.5% filtration efficiency (for a 300-nm KCl aerosol), and a ~0.8 mmAq pressure drop (at 13 cm/s). This study provides valuable information for the development of a hybrid air purification system that can serve various functions and be used in an indoor environment.

  17. Relationships between biomass, pressure drop, and performance in a polyurethane biofilter.

    PubMed

    Ryu, Hee Wook; Cho, Kyung-Suk; Chung, Dong Jin

    2010-03-01

    In biofilters for controlling volatile organic compounds (VOCs), clogging in the filter bed due to overgrowth of biomass causes the deterioration of biofilter performance. In this study, the relationships between biofilter performance, biomass concentration (X), and pressure drop (DeltaP) was qualitatively and quantitatively evaluated in a polyurethane (PU) biofilter. Benzene was used as a model VOC. The relationship between DeltaP and X at a moisture content of 80-90% was expressed as log DeltaP (mm H(2)Om(-1))=0.315+3.87 log X (g-dry cell weight (DCW) g-PU(-1)), 0.8

  18. Characterization of activated carbon fiber filters for pressure drop, submicrometer particulate collection, and mercury capture.

    PubMed

    Hayashi, T; Lee, T G; Hazelwood, M; Hedrick, E; Biswas, P

    2000-06-01

    The use of activated carbon fiber (ACF) filters for the capture of particulate matter and elemental Hg is demonstrated. The pressure drop and particle collection efficiency characteristics of the ACF filters were established at two different face velocities and for two different aerosols: spherical NaCl and combustion-generated silica particles. The clean ACF filter specific resistance was 153 kg m-2 sec-1. The experimental specific resistance for cake filtration was 1.6 x 10(6) sec-1 and 2.4 x 10(5) sec-1 for 0.5- and 1.5-micron mass median diameter particles, respectively. The resistance factor R was approximately 2, similar to that for the high-efficiency particulate air filters. There was a discrepancy in the measured particle collection efficiencies and those predicted by theory. The use of the ACF filter for elemental Hg capture was illustrated, and the breakthrough characteristic was established. The capacity of the ACF filter for Hg capture was similar to other powdered activated carbons.

  19. The numerical investigation of heat transfer and pressure drop of turbulent flow in a triangular microchannel

    NASA Astrophysics Data System (ADS)

    Rezaei, Omid; Akbari, Omid Ali; Marzban, Ali; Toghraie, Davood; Pourfattah, Farzad; Mashayekhi, Ramin

    2017-09-01

    In this presentation, the flow and heat transfer inside a microchannel with a triangular section, have been numerically simulated. In this three-dimensional simulation, the flow has been considered turbulent. In order to increase the heat transfer of the channel walls, the semi-truncated and semi-attached ribs have been placed inside the channel and the effect of forms and numbers of ribs has been studied. In this research, the base fluid is Water and the effect of volume fraction of Al2O3 nanoparticles on the amount of heat transfer and physics of flow have been investigated. The presented results are including of the distribution of Nusselt number in the channel, friction coefficient and Performance Evaluation Criterion of each different arrangement. The results indicate that, the ribs affect the physics of flow and their influence is absolutely related to Reynolds number of flow. Also, the investigation of the used semi-truncated and semi-attached ribs in Reynolds number indicates that, although heat transfer increases, but more pressure drop arises. Therefore, in this method, in order to improve the heat transfer from the walls of microchannel on the constant heat flux, using the pump is demanded.

  20. Comparative study of heat transfer and pressure drop during flow boiling and flow condensation in minichannels

    NASA Astrophysics Data System (ADS)

    Mikielewicz, Dariusz; Andrzejczyk, Rafał; Jakubowska, Blanka; Mikielewicz, Jarosław

    2014-09-01

    In the paper a method developed earlier by authors is applied to calculations of pressure drop and heat transfer coefficient for flow boiling and also flow condensation for some recent data collected from literature for such fluids as R404a, R600a, R290, R32,R134a, R1234yf and other. The modification of interface shear stresses between flow boiling and flow condensation in annular flow structure are considered through incorporation of the so called blowing parameter. The shear stress between vapor phase and liquid phase is generally a function of nonisothermal effects. The mechanism of modification of shear stresses at the vapor-liquid interface has been presented in detail. In case of annular flow it contributes to thickening and thinning of the liquid film, which corresponds to condensation and boiling respectively. There is also a different influence of heat flux on the modification of shear stress in the bubbly flow structure, where it affects bubble nucleation. In that case the effect of applied heat flux is considered. As a result a modified form of the two-phase flow multiplier is obtained, in which the nonadiabatic effect is clearly pronounced.

  1. Summary report for ITER Task-T19: MHD pressure drop and heat transfer study for liquid metal systems

    SciTech Connect

    Reed, C.B.; Hua, T.Q.; Natesan, K.; Kirillov, I.R.; Vitkovski, I.V.; Anisimov, A.M.

    1995-03-01

    A key feasibility issue for the ITER Vanadium/Lithium breeding blanket is the question of insulator coatings. Design calculations show that an electrically insulating layer is necessary to maintain an acceptably low MHD pressure drop. To begin experimental investigations of the MHD performance of candidate insulator materials and the technology for putting them in place, a new test section was prepared. Aluminum oxide was chosen as the first candidate insulating material because it may be used in combination with NaK in the ITER vacuum vessel and/or the divertor. Details on the methods used to produce the aluminum oxide layer as well as the microstructures of the coating and the aluminide sublayer are presented and discussed. The overall MHD pressure drop, local MHD pressure gradient, local transverse MHD pressure difference, and surface voltage distributions in both the circumferential and the axial directions are reported and discussed. The positive results obtained here for high-temperature NaK have two beneficial implications for ITER. First, since NaK may be used in the vacuum vessel and/or the divertor, these results support the design approach of using electrically insulating coatings to substantially reduce MHD pressure drop. Secondly, while Al{sub 2}O{sub 3}/SS is not the same coating/base material combination which would be used in the advanced blanket, this work nonetheless shows that it is possible to produce a viable insulating coating which is stable in contact with a high temperature alkali metal coolant.

  2. Estimation of turgor pressure through comparison between single plant cell and pressurized shell mechanics

    NASA Astrophysics Data System (ADS)

    Durand-Smet, P.; Gauquelin, E.; Chastrette, N.; Boudaoud, A.; Asnacios, A.

    2017-10-01

    While plant growth is well known to rely on turgor pressure, it is challenging to quantify the contribution of turgor pressure to plant cell rheology. Here we used a custom-made micro-rheometer to quantify the viscoelastic behavior of isolated plant cells while varying their internal turgor pressure. To get insight into how plant cells adapt their internal pressure to the osmolarity of their medium, we compared the mechanical behavior of single plant cells to that of a simple, passive, pressurized shell: a soccer ball. While both systems exhibited the same qualitative behavior, a simple mechanical model allowed us to quantify turgor pressure regulation at the single cell scale.

  3. Evaluation of the models available for the prediction of pressure drop in venturi scrubbers.

    PubMed

    Gonçalves, J A; Alonso, D F; Costa, M A; Azzopardi, B J; Coury, J R

    2001-01-29

    The major running cost derived from the operation of venturi scrubbers is pressure drop. In the present study, the predictions of different models are compared to experimental data from venturi scrubbers of different sizes (throat diameter from 1.9 to 16cm), geometries, operating variables and liquid injection arrangements. As a result, it is concluded that most of the models must be used with caution. Much attention must be paid to the validity of the assumptions employed in the mathematical models. The equations proposed by Calvert [Scrubbing, Air Pollution, 3rd Edition, Vol. IV, Academic Press, New York, 1982], Yung et al. [JAPCA 27 (1977) 348] or Hesketh [Atomization and cloud behaviour in wet scrubbers, in: Proceedings of the US-USSR Symposium Control Fine Particulate Emissions 1974, San Francisco, 15-18 January 1974] produce good results only in very specific situations. The model proposed by Boll [Ind. Eng. Chem. Fundam. 12 (1973) 40] is simple, easy to compute and agrees reasonably well with the experimental data. Unfortunately, it cannot predict the effect of different liquid injection arrangements. The model by Azzopardi and coworkers [Filtr. Sep. 21 (1984) 196; Trans. IchemE. 69B (1991) 237; Chem Eng. J. 67 (1997) 9] was the only one to give good predictions for all the range of variables studied. On the other hand, this model is not simple and requires from the engineer an additional effort in terms of computation. In order to apply this model to the rectangular geometry, the concept of hydraulic equivalent diameter was used.

  4. Experimental sizing and assessment of two-phase pressure drop correlations for a capillary tube with transcritical and subcritical carbon dioxide flow

    NASA Astrophysics Data System (ADS)

    Trinchieri, R.; Boccardi, G.; Calabrese, N.; Celata, G. P.; Zummo, G.

    2014-04-01

    In the last years, CO2 was proposed as an alternative refrigerant for different refrigeration applications (automotive air conditioning, heat pumps, refrigerant plants, etc.) In the case of low power refrigeration applications, as a household refrigerator, the use of too expensive components is not economically sustainable; therefore, even if the use of CO2 as the refrigerant is desired, it is preferable to use conventional components as much as possible. For these reasons, the capillary tube is frequently proposed as expansion system. Then, it is necessary to characterize the capillary in terms of knowledge of the evolving mass flow rate and the associate pressure drop under all possible operative conditions. For this aim, an experimental campaign has been carried out on the ENEA test loop "CADORE" to measure the performance of three capillary tubes having same inner diameter (0.55 mm) but different lengths (4, 6 and 8 meters). The test range of inlet pressure is between about 60 and 110 bar, whereas external temperatures are between about 20 to 42 °C. The two-phase pressure drop through the capillary tube is detected and experimental values are compared with the predictions obtained with the more widely used correlations available in the literature. Correlations have been tested over a wide range of variation of inlet flow conditions, as a function of different inlet parameters.

  5. Use of the isopycnic plots in designing operations of supercritical fluid chromatography. V. Pressure and density drops using mixtures of carbon dioxide and methanol as the mobile phase.

    PubMed

    Tarafder, Abhijit; Kaczmarski, Krzysztof; Poe, Donald P; Guiochon, Georges

    2012-10-05

    The drops of pressure and density along chromatographic columns of different characteristics, eluted with different mixtures of carbon dioxide and methanol was mapped as functions of the column outlet pressure and the operating temperature. This paper extends an earlier report reporting the extent of the pressure and density drops along chromatographic columns eluted with neat CO(2)[1]. It illustrates the similarities and differences in the pressure and density profiles along columns operated with mixed mobile phases and with neat CO(2). Numerical calculations of the pressure and density drops along columns packed with particles of different sizes, under different operating conditions (temperature, outlet pressure, and flow rate), provide important insights regarding the extent of the pressure and density drops under these operating conditions. Copyright © 2012 Elsevier B.V. All rights reserved.

  6. A study of pressure drop in a Capillary tube-viscometer for a two-phase flow

    SciTech Connect

    Ohene, F.; Livingston, C.; Matthews, C.; Rhone, Y.

    1995-09-01

    The analysis of pipeline transportation of highly concentrated suspensions such as coal-water slurries, can exhibit several flow characteristics depending on the concentration and the physical parameters of the dispersed phase. Experiments were conducted for coal-water slurries flows in a series of horizontal capillary tubes of diameters 0.8, 1.5 and 3.0 mm and 100 mm in length, in order to investigate the effect of concentration, pressure drop, and the transitional Reynolds number from laminar to turbulent flow in a homogeneous slurry. The solid concentration was varied from 15% to 63% in 0.1% xanthum gum solution. Pressure drop and the volume flow measurement were made using HVA-6 Capillary viscometer. The Reynolds numbers obtained were found to be dependent on the slurry concentration and the viscosity of the slurry mixture, but independent of the capillary diameter.

  7. Two Phase Flow Modeling: Summary of Flow Regimes and Pressure Drop Correlations in Reduced and Partial Gravity

    NASA Technical Reports Server (NTRS)

    Balasubramaniam, R.; Rame, E.; Kizito, J.; Kassemi, M.

    2006-01-01

    The purpose of this report is to provide a summary of state-of-the-art predictions for two-phase flows relevant to Advanced Life Support. We strive to pick out the most used and accepted models for pressure drop and flow regime predictions. The main focus is to identify gaps in predictive capabilities in partial gravity for Lunar and Martian applications. Following a summary of flow regimes and pressure drop correlations for terrestrial and zero gravity, we analyze the fully developed annular gas-liquid flow in a straight cylindrical tube. This flow is amenable to analytical closed form solutions for the flow field and heat transfer. These solutions, valid for partial gravity as well, may be used as baselines and guides to compare experimental measurements. The flow regimes likely to be encountered in the water recovery equipment currently under consideration for space applications are provided in an appendix.

  8. Effect of electrode intrusion on pressure drop and electrochemical performance of an all-vanadium redox flow battery

    NASA Astrophysics Data System (ADS)

    Kumar, S.; Jayanti, S.

    2017-08-01

    In this paper, we present a study of the effect of electrode intrusion into the flow channel in an all-vanadium redox flow battery. Permeability, pressure drop and electrochemical performance have been measured in a cell with active area 100 cm2and 414 cm2 fitted with a carbon felt electrode of thickness of 3, 6 or 9 mm compressed to 1.5, 2.5 or 4 mm, respectively, during assembly. Results show that the pressure drop is significantly higher than what can be expected in the thick electrode case while its electrochemical performance is lower. Detailed flow analysis using computational fluid dynamics simulations in two different flow fields shows that both these results can be attributed to electrode intrusion into the flow channel leading to increased resistance to electrolyte flow through the electrode. A correlation is proposed to evaluate electrode intrusion depth as a function of compression.

  9. Steady state boiling crisis in a helium vertically heated natural circulation loop - Part 2: Friction pressure drop lessening

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

    Experiments were conducted on a 2-m high two-phase helium natural circulation loop operating at 4.2 K and 1 atm. Two heated sections with different internal diameter (10 and 6 mm) were tested. The power applied on the heated section wall was controlled in increasing and decreasing sequences, and temperature along the section, mass flow rate and pressure drop evolutions were registered. The post-CHF regime was studied watching simultaneously the evolution of boiling crisis onset along the test section and the evolution of pressure drop and mass flow rate. A significant lessening of friction was observed simultaneous to the development of the post-CHF regime, accompanied by a mass flow rate increase, which lets suppose that the vapor film in the film boiling regime acts as a lubricant. A model was created based on this idea and on heat transfer considerations. The predictions by this model are satisfactory for the low quality post-CHF regime.

  10. Experimental studies on pressure drop characteristics of cryogenic cross-counter flow coiled finned tube heat exchangers

    NASA Astrophysics Data System (ADS)

    Gupta, Prabhat Kumar; Kush, P. K.; Tiwari, Ashesh

    2010-04-01

    Cross-counter flow coiled finned tube heat exchangers used in medium capacity helium liquefiers/refrigerators were developed in our lab. These heat exchangers were developed using integrated low finned tubes. Experimental studies have been performed to know the pressure drop characteristics of tube side and shell side flow of these heat exchangers. All experiments were performed at room temperature in the Reynolds number range of 3000-30,000 for tube side and 25-155 for shell side. The results of present experiments indicate that available correlations for tube side can not be used for prediction of tube side pressure drop data due to complex surface formation at inner side of tube during formation of fins over the outer surface. Results also indicate that surface roughness effect becomes more pronounced as the value of di/ D m increases. New correlations based on present experimental data are proposed for predicting the friction factors for tube side and shell side.

  11. Experimental study of the effect of drag reducing agent on pressure drop and thermal efficiency of an air cooler

    NASA Astrophysics Data System (ADS)

    Peyghambarzadeh, S. M.; Hashemabadi, S. H.; Saffarian, H.; Shekari, F.

    2016-01-01

    Effect of polymeric drag reduction agents (DRAs) on pressure drop and heat transfer was studied. Aqueous solutions of carboxy methyl cellulose were used inside an air-finned heat exchanger. Despite the previous studies which indicated the importance of drag reduction just in turbulent flow, results of this study in laminar flow indicated that the addition of DRA increases drag reduction, and decreases the overall heat transfer coefficient.

  12. Smooth- and enhanced-tube heat transfer and pressure drop : Part II. The role of transition to turbulent flow.

    SciTech Connect

    Obot, N. T.; Das, L.; Rabas, T. J.

    2000-11-14

    The objectives of this presentation are two-fold: first, to demonstrate the connection between the attainable coefficients and transition to turbulent flow by using the transition-based corresponding states method to generalize results obtained with smooth tubes and enhanced tubes, and second, to provide guidelines on the calculation of heat transfer coefficients from pressure-drop data and vice versa by using the transition concept or the functional law of corresponding states.

  13. Pressure drop of two-phase dry-plug flow in round mini-channels: Effect of moving contact line

    SciTech Connect

    Lee, Chi Young; Lee, Sang Yong

    2010-01-15

    In the present experimental study, the pressure drop of the two-phase dry-plug flow (dry wall condition at the gas portions) in round mini-channels was investigated. The air-water mixtures were flowed through the round mini-channels made of polyurethane and Teflon, respectively, with their inner diameters ranging from 1.62 to 2.16 mm. In the dry-plug flow regime, the pressure drop measured became larger either by increasing the liquid superficial velocity or by decreasing the gas superficial velocity due to the increase of the number of the moving contact lines in the test section. In such a case, the role of the moving contact lines turned out to be significant. Therefore, a pressure drop model of dry-plug flow was proposed through modification of the dynamic contact angle analysis taking account of the energy dissipation by the moving contact lines, which represents the experimental data within the mean deviation of 4%. (author)

  14. Heat transfer and pressure drop measurements in an air/molten salt direct-contact heat exchanger

    SciTech Connect

    Bohn, M.S.

    1988-11-01

    This paper presents a comparison of experimental data with a recently published model of heat exchange in irrigated packed beds. Heat transfer and pressure drop were measured in a 150 mm (ID) column with a 610-mm bed of metal Pall rings. Molten nitrate salt and preheated air were the working fluids with a salt inlet temperature of approximately 440{degree}C and air inlet temperatures of approximately 230{degree}C. A comparison between the experimental data and the heat transfer model is made on the basis of heat transfer from the salt. For the range of air and salt flow rates tested, 0.3 to 1.2 kg/m{sup 2} s air flow and 6 to 18 kg/m{sup 2} s salt flow, the data agree with the model within 22% standard deviation. In addition, a model for the column pressure drop was validated, agreeing with the experimental data within 18% standard deviation over the range of column pressure drop from 40 to 1250 Pa/m. 25 refs., 7 figs., 2 tabs.

  15. Pressure drop of two-phase plug flow in round mini-channels: Influence of surface wettability

    SciTech Connect

    Lee, Chi Young; Lee, Sang Yong

    2008-09-15

    In the present experimental study, the pressure drop of two-phase plug flows in round mini-channels was investigated for three different tube materials, i.e., glass, polyurethane and Teflon, respectively, with their inner diameters ranging from 1.62 to 2.16 mm. Air and water were used as the test fluids. In the wet-plug flow regime (wet wall condition at the gas portions), the pressure drop was reasonably predicted by the homogeneous flow model or by the correlations of Mishima and Hibiki [K. Mishima, T. Hibiki, Some characteristics of air-water two-phase flow in small diameter vertical tubes, Int. J. Multiphase Flow 22 (1996) 703-712] and Chisholm [D. Chisholm, A theoretical basis for the Lockhart-Martinelli correlation for two-phase flow, Int. J. Heat Mass Transfer 10 (1967) 1767-1778]. On the other hand, in the dry-plug flow regime (dry wall condition at the gas portions), the role of the moving contact lines turned out to be significant. To take into account the effect of the moving contact lines, a modified Lockhart-Martinelli type correlation was proposed, which fitted the measured pressure-drop data within the mean deviation of 6%. (author)

  16. The role of water in the performance of biofilters: parameterization of pressure drop and sorption capacities for common packing materials.

    PubMed

    Dorado, Antonio D; Lafuente, Javier; Gabriel, David; Gamisans, Xavier

    2010-08-15

    The presence of water in a biofilter is critical in keeping microorganisms active and abating pollutants. In addition, the amount of water retained in a biofilter may drastically affect the physical properties of packing materials and packed beds. In this study, the influence of water on the pressure drop and sorption capacities of 10 different packing materials were experimentally studied and compared. Pressure drop was characterized as a function of dynamic hold-up, porosity and gas flow rate. Experimental data were fitted to a mathematical expression based on a modified Ergun correlation. Sorption capacities for toluene were determined for both wet and dry materials to obtain information about the nature of interactions between the contaminant, the packing materials and the aqueous phase. The experimental sorption capacities of materials were fitted to different isotherm models for gas adsorption in porous materials. The corresponding confidence interval was determined by the Fisher information matrix. The results quantified the dynamic hold-up effect resulting from the significant increase in the pressure drop throughout the bed, i.e. the financial cost of driving air, and the negative effect of this air on the total amount of hydrophobic pollutant that can be adsorbed by the supports. Furthermore, the results provided equations for ascertaining water presence and sorption capacities that could be widely used in the mathematical modeling of biofilters.

  17. Characterization of surface roughness effects on pressure drop in single-phase flow in minichannels

    NASA Astrophysics Data System (ADS)

    Kandlikar, Satish G.; Schmitt, Derek; Carrano, Andres L.; Taylor, James B.

    2005-10-01

    Roughness features on the walls of a channel wall affect the pressure drop of a fluid flowing through that channel. This roughness effect can be described by (i) flow area constriction and (ii) increase in the wall shear stress. Replotting the Moody's friction factor chart with the constricted flow diameter results in a simplified plot and yields a single asymptotic value of friction factor for relative roughness values of ɛ /D>0.03 in the fully developed turbulent region. After reviewing the literature, three new roughness parameters are proposed (maximum profile peak height Rp, mean spacing of profile irregularities RSm, and floor distance to mean line Fp). Three additional parameters are presented to consider the localized hydraulic diameter variation (maximum, minimum, and average) in future work. The roughness ɛ is then defined as Rp+Fp. This definition yields the same value of roughness as obtained from the sand-grain roughness [H. Darcy, Recherches Experimentales Relatives au Mouvement de L'Eau dans les Tuyaux (Mallet-Bachelier, Paris, France, 1857); J. T. Fanning, A Practical Treatise on Hydraulic and Water Supply Engineering (Van Nostrand, New York, 1877, revised ed. 1886); J. Nikuradse, "Laws of flow in rough pipes" ["Stromungsgesetze in Rauen Rohren," VDI-Forschungsheft 361 (1933)]; Beilage zu "Forschung auf dem Gebiete des Ingenieurwesens," Ausgabe B Band 4, English translation NACA Tech. Mem. 1292 (1937)]. Specific experiments are conducted using parallel sawtooth ridge elements, placed normal to the flow direction, in aligned and offset configurations in a 10.03mm wide rectangular channel with variable gap (resulting hydraulic diameters of 325μm-1819μm with Reynolds numbers ranging from 200 to 7200 for air and 200 to 5700 for water). The use of constricted flow diameter extends the applicability of the laminar friction factor equations to relative roughness values (sawtooth height) up to 14%. In the turbulent region, the aligned and offset

  18. On axial temperature gradients due to large pressure drops in dense fluid chromatography.

    PubMed

    Colgate, Sam O; Berger, Terry A

    2015-03-13

    The effect of energy degradation (Degradation is the creation of net entropy resulting from irreversibility.) accompanying pressure drops across chromatographic columns is examined with regard to explaining axial temperature gradients in both high performance liquid chromatography (HPLC) and supercritical fluid chromatography (SFC). The observed effects of warming and cooling can be explained equally well in the language of thermodynamics or fluid dynamics. The necessary equivalence of these treatments is reviewed here to show the legitimacy of using whichever one supports the simpler determination of features of interest. The determination of temperature profiles in columns by direct application of the laws of thermodynamics is somewhat simpler than applying them indirectly by solving the Navier-Stokes (NS) equations. Both disciplines show that the preferred strategy for minimizing the reduction in peak quality caused by temperature gradients is to operate columns as nearly adiabatically as possible (i.e. as Joule-Thomson expansions). This useful fact, however, is not widely familiar or appreciated in the chromatography community due to some misunderstanding of the meaning of certain terms and expressions used in these disciplines. In fluid dynamics, the terms "resistive heating" or "frictional heating" have been widely used as synonyms for the dissipation function, Φ, in the NS energy equation. These terms have been widely used by chromatographers as well, but often misinterpreted as due to friction between the mobile phase and the column packing, when in fact Φ describes the increase in entropy of the system (dissipation, ∫TdSuniv>0) due to the irreversible decompression of the mobile phase. Two distinctly different contributions to the irreversibility are identified; (1) ΔSext, viscous dissipation of work done by the external surroundings driving the flow (the pump) contributing to its warming, and (2) ΔSint, entropy change accompanying decompression of

  19. Workplace field testing of the pressure drop of particulate respirators using welding fumes.

    PubMed

    Cho, Hyun-Woo; Yoon, Chung-Sik

    2012-10-01

    In a previous study, we concluded that respirator testing with a sodium chloride aerosol gave a conservative estimate of filter penetration for welding fume aerosols. A rapid increase in the pressure drop (PD) of some respirators was observed as fumes accumulated on the filters. The present study evaluated particulate respirator PD based on workplace field tests. A field PD tester was designed and validated using the TSI 8130 Automatic Filter Tester, designed in compliance with National Institute for Occupational and Safety and Health regulation 42 CFR part 84. Three models (two replaceable dual-type filters and one replaceable single-type filter) were evaluated against CO(2) gas arc welding on mild steel in confined booths in the workplace. Field tests were performed under four airborne concentrations (27.5, 15.4, 7.9, and 2.1 mg m(-3)). The mass concentration was measured by the gravimetric method, and number concentration was monitored using P-Trak (Model 8525, TSI, USA). Additionally, photos and scanning electron microscopy-energy dispersive X-ray spectroscopy were used to visualize and analyze the composition of welding fumes trapped in the filters. The field PD tester showed no significant difference compared with the TSI tester. There was no significant difference in the initial PD between laboratory and field results. The PD increased as a function of fume load on the respirator filters for all tested models. The increasing PD trend differed by models, and PD increased rapidly at high concentrations because greater amount of fumes accumulated on the filters in a given time. The increase in PD as a function of fume load on the filters showed a similar pattern as fume load varied for a particular model, but different patterns were observed for different models. Images and elemental analyses of fumes trapped on the respirator filters showed that most welding fumes were trapped within the first layer, outer web cover, and second layer, in order, while no fumes

  20. Effect of airstream velocity on mean drop diameters of water sprays produced by pressure and air atomizing nozzles

    NASA Technical Reports Server (NTRS)

    Ingebo, R. D.

    1977-01-01

    A scanning radiometer was used to determine the effect of airstream velocity on the mean drop diameter of water sprays produced by pressure atomizing and air atomizing fuel nozzles used in previous combustion studies. Increasing airstream velocity from 23 to 53.4 meters per second reduced the Sauter mean diameter by approximately 50 percent with both types of fuel nozzles. The use of a sonic cup attached to the tip of an air assist nozzle reduced the Sauter mean diameter by approximately 40 percent. Test conditions included airstream velocities of 23 to 53.4 meters per second at 293 K and atmospheric pressure.

  1. Pressure drop increase by biofilm accumulation in spiral wound RO and NF membrane systems: role of substrate concentration, flow velocity, substrate load and flow direction.

    PubMed

    Vrouwenvelder, J S; Hinrichs, C; Van der Meer, W G J; Van Loosdrecht, M C M; Kruithof, J C

    2009-01-01

    In an earlier study, it was shown that biofouling predominantly is a feed spacer channel problem. In this article, pressure drop development and biofilm accumulation in membrane fouling simulators have been studied without permeate production as a function of the process parameters substrate concentration, linear flow velocity, substrate load and flow direction. At the applied substrate concentration range, 100-400 microg l(-1) as acetate carbon, a higher concentration caused a faster and greater pressure drop increase and a greater accumulation of biomass. Within the range of linear flow velocities as applied in practice, a higher linear flow velocity resulted in a higher initial pressure drop in addition to a more rapid and greater pressure drop increase and biomass accumulation. Reduction of the linear flow velocity resulted in an instantaneous reduction of the pressure drop caused by the accumulated biomass, without changing the biofilm concentration. A higher substrate load (product of substrate concentration and flow velocity) was related to biomass accumulation. The effect of the same amount of accumulated biomass on the pressure drop increase was related to the linear flow velocity. A decrease of substrate load caused a gradual decline in time of both biomass concentration and pressure drop increase. It was concluded that the pressure drop increase over spiral wound reverse osmosis (RO) and nanofiltration (NF) membrane systems can be reduced by lowering both substrate load and linear flow velocity. There is a need for RO and NF systems with a low pressure drop increase irrespective of the biomass formation. Current efforts to control biofouling of spiral wound membranes focus in addition to pretreatment on membrane improvement. According to these authors, adaptation of the hydrodynamics, spacers and pressure vessel configuration offer promising alternatives. Additional approaches may be replacing heavily biofouled elements and flow direction reversal.

  2. Biological Control of Lettuce Drop and Host Plant Colonization by Rhizospheric and Endophytic Streptomycetes

    PubMed Central

    Chen, Xiaoyulong; Pizzatti, Cristina; Bonaldi, Maria; Saracchi, Marco; Erlacher, Armin; Kunova, Andrea; Berg, Gabriele; Cortesi, Paolo

    2016-01-01

    Lettuce drop, caused by the soil borne pathogen Sclerotinia sclerotiorum, is one of the most common and serious diseases of lettuce worldwide. Increased concerns about the side effects of chemical pesticides have resulted in greater interest in developing biocontrol strategies against S. sclerotiorum. However, relatively little is known about the mechanisms of Streptomyces spp. as biological control agents against S. sclerotiorum on lettuce. Two Streptomyces isolates, S. exfoliatus FT05W and S. cyaneus ZEA17I, inhibit mycelial growth of Sclerotinia sclerotiorum by more than 75% in vitro. We evaluated their biocontrol activity against S. sclerotiorum in vivo, and compared them to Streptomyces lydicus WYEC 108, isolated from Actinovate®. When Streptomyces spp. (106 CFU/mL) were applied to S. sclerotiorum inoculated substrate in a growth chamber 1 week prior lettuce sowing, they significantly reduced the risk of lettuce drop disease, compared to the inoculated control. Interestingly, under field conditions, S. exfoliatus FT05W and S. cyaneus ZEA17I protected lettuce from drop by 40 and 10% respectively, whereas S. lydicus WYEC 108 did not show any protection. We further labeled S. exfoliatus FT05W and S. cyaneus ZEA17I with the enhanced GFP (EGFP) marker to investigate their rhizosphere competence and ability to colonize lettuce roots using confocal laser scanning microscopy (CLSM). The abundant colonization of young lettuce seedlings by both strains demonstrated Streptomyces' capability to interact with the host from early stages of seed germination and root development. Moreover, the two strains were detected also on 2-week-old roots, indicating their potential of long-term interactions with lettuce. Additionally, scanning electron microscopy (SEM) observations showed EGFP-S. exfoliatus FT05W endophytic colonization of lettuce root cortex tissues. Finally, we determined its viability and persistence in the rhizosphere and endorhiza up to 3 weeks by quantifying its

  3. Biological Control of Lettuce Drop and Host Plant Colonization by Rhizospheric and Endophytic Streptomycetes.

    PubMed

    Chen, Xiaoyulong; Pizzatti, Cristina; Bonaldi, Maria; Saracchi, Marco; Erlacher, Armin; Kunova, Andrea; Berg, Gabriele; Cortesi, Paolo

    2016-01-01

    Lettuce drop, caused by the soil borne pathogen Sclerotinia sclerotiorum, is one of the most common and serious diseases of lettuce worldwide. Increased concerns about the side effects of chemical pesticides have resulted in greater interest in developing biocontrol strategies against S. sclerotiorum. However, relatively little is known about the mechanisms of Streptomyces spp. as biological control agents against S. sclerotiorum on lettuce. Two Streptomyces isolates, S. exfoliatus FT05W and S. cyaneus ZEA17I, inhibit mycelial growth of Sclerotinia sclerotiorum by more than 75% in vitro. We evaluated their biocontrol activity against S. sclerotiorum in vivo, and compared them to Streptomyces lydicus WYEC 108, isolated from Actinovate®. When Streptomyces spp. (10(6) CFU/mL) were applied to S. sclerotiorum inoculated substrate in a growth chamber 1 week prior lettuce sowing, they significantly reduced the risk of lettuce drop disease, compared to the inoculated control. Interestingly, under field conditions, S. exfoliatus FT05W and S. cyaneus ZEA17I protected lettuce from drop by 40 and 10% respectively, whereas S. lydicus WYEC 108 did not show any protection. We further labeled S. exfoliatus FT05W and S. cyaneus ZEA17I with the enhanced GFP (EGFP) marker to investigate their rhizosphere competence and ability to colonize lettuce roots using confocal laser scanning microscopy (CLSM). The abundant colonization of young lettuce seedlings by both strains demonstrated Streptomyces' capability to interact with the host from early stages of seed germination and root development. Moreover, the two strains were detected also on 2-week-old roots, indicating their potential of long-term interactions with lettuce. Additionally, scanning electron microscopy (SEM) observations showed EGFP-S. exfoliatus FT05W endophytic colonization of lettuce root cortex tissues. Finally, we determined its viability and persistence in the rhizosphere and endorhiza up to 3 weeks by quantifying

  4. Quadratic formula for determining the drop size in pressure-atomized sprays with and without swirl

    SciTech Connect

    Lee, T.-W An, Keju

    2016-06-15

    We use a theoretical framework based on the integral form of the conservation equations, along with a heuristic model of the viscous dissipation, to find a closed-form solution to the liquid atomization problem. The energy balance for the spray renders to a quadratic formula for the drop size as a function, primarily of the liquid velocity. The Sauter mean diameter found using the quadratic formula shows good agreements and physical trends, when compared with experimental observations. This approach is shown to be applicable toward specifying initial drop size in computational fluid dynamics of spray flows.

  5. Quadratic formula for determining the drop size in pressure-atomized sprays with and without swirl

    NASA Astrophysics Data System (ADS)

    Lee, T.-W.; An, Keju

    2016-06-01

    We use a theoretical framework based on the integral form of the conservation equations, along with a heuristic model of the viscous dissipation, to find a closed-form solution to the liquid atomization problem. The energy balance for the spray renders to a quadratic formula for the drop size as a function, primarily of the liquid velocity. The Sauter mean diameter found using the quadratic formula shows good agreements and physical trends, when compared with experimental observations. This approach is shown to be applicable toward specifying initial drop size in computational fluid dynamics of spray flows.

  6. Pressure, temperature and density drops along supercritical fluid chromatography columns in different thermal environments. III. Mixtures of carbon dioxide and methanol as the mobile phase.

    PubMed

    Poe, Donald P; Veit, Devon; Ranger, Megan; Kaczmarski, Krzysztof; Tarafder, Abhijit; Guiochon, Georges

    2014-01-03

    The pressure, temperature and density drops along SFC columns eluted with a CO2/methanol mobile phase were measured and compared with theoretical values. For columns packed with 3- and 5-μm particles the pressure and temperature drops were measured using a mobile phase of 95% CO2 and 5% methanol at a flow rate of 5mL/min, at temperatures from 20 to 100°C, and outlet pressures from 80 to 300bar. The density drop was calculated based on the temperature and pressure at the column inlet and outlet. The columns were suspended in a circulating air bath, either bare or covered with foam insulation. The experimental measurements were compared to theoretical results obtained by numerical simulation. For the convective air condition at outlet pressures above 100bar the average difference between the experimental and calculated temperature drops and pressure drops were 0.1°C and 0.7% for the bare 3-μm column, respectively, and were 0.6°C and 4.1% for the insulated column. The observed temperature drops for the insulated columns are consistent with those predicted by the Joule-Thomson coefficients for isenthalpic expansion. The dependence of the temperature and the pressure drops on the Joule-Thomson coefficient and kinematic viscosity are described for carbon dioxide mobile phases containing up to 20% methanol.

  7. Sensitivity Analysis and Accuracy of a CFD-TFM Approach to Bubbling Bed Using Pressure Drop Fluctuations.

    PubMed

    Tricomi, Leonardo; Melchiori, Tommaso; Chiaramonti, David; Boulet, Micaël; Lavoie, Jean Michel

    2017-01-01

    Based upon the two fluid model (TFM) theory, a CFD model was implemented to investigate a cold multiphase-fluidized bubbling bed reactor. The key variable used to characterize the fluid dynamic of the experimental system, and compare it to model predictions, was the time-pressure drop induced by the bubble motion across the bed. This time signal was then processed to obtain the power spectral density (PSD) distribution of pressure fluctuations. As an important aspect of this work, the effect of the sampling time scale on the empirical power spectral density (PSD) was investigated. A time scale of 40 s was found to be a good compromise ensuring both simulation performance and numerical validation consistency. The CFD model was first numerically verified by mesh refinement process, after what it was used to investigate the sensitivity with regards to minimum fluidization velocity (as a calibration point for drag law), restitution coefficient, and solid pressure term while assessing his accuracy in matching the empirical PSD. The 2D model provided a fair match with the empirical time-averaged pressure drop, the relating fluctuations amplitude, and the signal's energy computed as integral of the PSD. A 3D version of the TFM was also used and it improved the match with the empirical PSD in the very first part of the frequency spectrum.

  8. Sensitivity Analysis and Accuracy of a CFD-TFM Approach to Bubbling Bed Using Pressure Drop Fluctuations

    PubMed Central

    Tricomi, Leonardo; Melchiori, Tommaso; Chiaramonti, David; Boulet, Micaël; Lavoie, Jean Michel

    2017-01-01

    Based upon the two fluid model (TFM) theory, a CFD model was implemented to investigate a cold multiphase-fluidized bubbling bed reactor. The key variable used to characterize the fluid dynamic of the experimental system, and compare it to model predictions, was the time-pressure drop induced by the bubble motion across the bed. This time signal was then processed to obtain the power spectral density (PSD) distribution of pressure fluctuations. As an important aspect of this work, the effect of the sampling time scale on the empirical power spectral density (PSD) was investigated. A time scale of 40 s was found to be a good compromise ensuring both simulation performance and numerical validation consistency. The CFD model was first numerically verified by mesh refinement process, after what it was used to investigate the sensitivity with regards to minimum fluidization velocity (as a calibration point for drag law), restitution coefficient, and solid pressure term while assessing his accuracy in matching the empirical PSD. The 2D model provided a fair match with the empirical time-averaged pressure drop, the relating fluctuations amplitude, and the signal’s energy computed as integral of the PSD. A 3D version of the TFM was also used and it improved the match with the empirical PSD in the very first part of the frequency spectrum. PMID:28695119

  9. Plant adaptation to low atmospheric pressures: potential molecular responses

    NASA Technical Reports Server (NTRS)

    Ferl, Robert J.; Schuerger, Andrew C.; Paul, Anna-Lisa; Gurley, William B.; Corey, Kenneth; Bucklin, Ray

    2002-01-01

    There is an increasing realization that it may be impossible to attain Earth normal atmospheric pressures in orbital, lunar, or Martian greenhouses, simply because the construction materials do not exist to meet the extraordinary constraints imposed by balancing high engineering requirements against high lift costs. This equation essentially dictates that NASA have in place the capability to grow plants at reduced atmospheric pressure. Yet current understanding of plant growth at low pressures is limited to just a few experiments and relatively rudimentary assessments of plant vigor and growth. The tools now exist, however, to make rapid progress toward understanding the fundamental nature of plant responses and adaptations to low pressures, and to develop strategies for mitigating detrimental effects by engineering the growth conditions or by engineering the plants themselves. The genomes of rice and the model plant Arabidopsis thaliana have recently been sequenced in their entirety, and public sector and commercial DNA chips are becoming available such that thousands of genes can be assayed at once. A fundamental understanding of plant responses and adaptation to low pressures can now be approached and translated into procedures and engineering considerations to enhance plant growth at low atmospheric pressures. In anticipation of such studies, we present here the background arguments supporting these contentions, as well as informed speculation about the kinds of molecular physiological responses that might be expected of plants in low-pressure environments.

  10. Plant adaptation to low atmospheric pressures: potential molecular responses.

    PubMed

    Ferl, Robert J; Schuerger, Andrew C; Paul, Anna-Lisa; Gurley, William B; Corey, Kenneth; Bucklin, Ray

    2002-01-01

    There is an increasing realization that it may be impossible to attain Earth normal atmospheric pressures in orbital, lunar, or Martian greenhouses, simply because the construction materials do not exist to meet the extraordinary constraints imposed by balancing high engineering requirements against high lift costs. This equation essentially dictates that NASA have in place the capability to grow plants at reduced atmospheric pressure. Yet current understanding of plant growth at low pressures is limited to just a few experiments and relatively rudimentary assessments of plant vigor and growth. The tools now exist, however, to make rapid progress toward understanding the fundamental nature of plant responses and adaptations to low pressures, and to develop strategies for mitigating detrimental effects by engineering the growth conditions or by engineering the plants themselves. The genomes of rice and the model plant Arabidopsis thaliana have recently been sequenced in their entirety, and public sector and commercial DNA chips are becoming available such that thousands of genes can be assayed at once. A fundamental understanding of plant responses and adaptation to low pressures can now be approached and translated into procedures and engineering considerations to enhance plant growth at low atmospheric pressures. In anticipation of such studies, we present here the background arguments supporting these contentions, as well as informed speculation about the kinds of molecular physiological responses that might be expected of plants in low-pressure environments.

  11. Analysis of pressure drop characteristics and methods for calculating gas and gas-solid flow in horizontal pipes for dilute coal conveying system

    SciTech Connect

    Weiguo Pan; Zuohe Chi; Yongjing Liao

    1997-07-01

    This article reported pressure drop characteristics and methods for calculating friction factors {lambda} 0 and {lambda}{sub {mu}} for gas and gas-solids flows, respectively, in straight horizontal pipes are summarized advantages seed. The and disadvantages of calculating friction factor {lambda}{sub {mu}} through dimensional analysis in comparison with model simulation are analyzed. It is pointed out that model simulation is more suitable to engineering use than dimensional analysis. According to experimental results of dilute gas-coal powder flow in straight horizontal pipes of the coal pulverization system in a power plant; an empirical formula and a theoretical formula for calculating friction factor {lambda}{sub {mu}} in straight horizontal pipes transporting dilute coal powder are obtained.

  12. Special topics reports for the reference tandem mirror fusion breeder: liquid metal MHD pressure drop effects in the packed bed blanket. Vol. 1

    SciTech Connect

    McCarville, T.J.; Berwald, D.H.; Wong, C.P.C.

    1984-09-01

    Magnetohydrodynamic (MHD) effects which result from the use of liquid metal coolants in magnetic fusion reactors include the modification of flow profiles (including the suppression of turbulence) and increases in the primary loop pressure drop and the hydrostatic pressure at the first wall of the blanket. In the reference fission-suppressed tandem mirror fusion breeder design concept, flow profile modification is a relatively minor concern, but the MHD pressure drop in flowing the liquid lithium coolant through an annular packed bed of beryllium/thorium pebbles is directly related to the required first wall structure thickness. As such, it is a major concern which directly impacts fissile breeding efficiency. Consequently, an improved model for the packed bed pressure drop has been developed. By considering spacial averages of electric fields, currents, and fluid flow velocities the general equations have been reduced to simple expressions for the pressure drop. The averaging approach results in expressions for the pressure drop involving a constant which reflects details of the flow around the pebbles. Such details are difficult to assess analytically, and the constant may eventually have to be evaluated by experiment. However, an energy approach has been used in this study to bound the possible values of the constant, and thus the pressure drop. In anticipation that an experimental facility might be established to evaluate the undetermined constant as well as to address other uncertainties, a survey of existing facilities is presented.

  13. High-fin staggered tube banks: Heat transfer and pressure drop for turbulent single phase gas flow

    NASA Astrophysics Data System (ADS)

    1986-10-01

    This Data Item ESDU 86022 is an addition to the Heat Transfer Sub-series. New correlations are presented for external heat transfer coefficient and static pressure loss for single phase flow over plain circular fins of either retangular or tapered cross section on round tubes. The correlations were derived by a regression analysis of experimental results extracted from the literature for a wide range of tube bundle configurations. Fin densities of 4 to 11 per inch (equivalent to fin pitches of 6.4 to 2.3 mm) tube outside diameters of 3/8 to 2 inch (10 to 51 mm), fin heights of 1/4 to 5/8 inch (6 to 16 mm), and ratios of fin tip to fin root diameter of 1.2 to 2.4 were covered. For heat transfer the range of Reynolds number based on tube outer diameter was from 2,000 to 40,000 and for pressure drop from 5,000 to 50,000. Comparison of the prediction with experiment shows that for heat transfer 85% of the data points were within 10% of estimated and for pressure drop 72% were within 10%. A comprehensive worked example showing the use of the method for an air cooled heat exchanger bundle is included. The applicability of this method to nonintegral fins is considered and factors influencing the thermal resistance of the interface are discussed. Effects of fouling are also briefly covered.

  14. International Space Station (ISS) Bacterial Filter Elements (BFEs): Filter Efficiency and Pressure Drop Testing of Returned Units

    NASA Technical Reports Server (NTRS)

    Green, Robert D.; Agui, Juan H.; Vijayakumar, R.; Berger, Gordon M.; Perry, Jay L.

    2017-01-01

    The air quality control equipment aboard the International Space Station (ISS) and future deep space exploration vehicles provide the vital function of maintaining a clean cabin environment for the crew and the hardware. This becomes a serious challenge in pressurized space compartments since no outside air ventilation is possible, and a larger particulate load is imposed on the filtration system due to lack of sedimentation. The ISS Environmental Control and Life Support (ECLS) system architecture in the U.S. Segment uses a distributed particulate filtration approach consisting of traditional High-Efficiency Particulate Air (HEPA) filters deployed at multiple locations in each U.S. Seg-ment module; these filters are referred to as Bacterial Filter Elements, or BFEs. In our previous work, we presented results of efficiency and pressure drop measurements for a sample set of two returned BFEs with a service life of 2.5 years. In this follow-on work, we present similar efficiency, pressure drop, and leak tests results for a larger sample set of six returned BFEs. The results of this work can aid the ISS Program in managing BFE logistics inventory through the stations planned lifetime as well as provide insight for managing filter element logistics for future exploration missions. These results also can provide meaningful guidance for particulate filter designs under consideration for future deep space exploration missions.

  15. Impact of organic nutrient load on biomass accumulation, feed channel pressure drop increase and permeate flux decline in membrane systems.

    PubMed

    Bucs, Sz S; Valladares Linares, R; van Loosdrecht, M C M; Kruithof, J C; Vrouwenvelder, J S

    2014-12-15

    The influence of organic nutrient load on biomass accumulation (biofouling) and pressure drop development in membrane filtration systems was investigated. Nutrient load is the product of nutrient concentration and linear flow velocity. Biofouling - excessive growth of microbial biomass in membrane systems - hampers membrane performance. The influence of biodegradable organic nutrient load on biofouling was investigated at varying (i) crossflow velocity, (ii) nutrient concentration, (iii) shear, and (iv) feed spacer thickness. Experimental studies were performed with membrane fouling simulators (MFSs) containing a reverse osmosis (RO) membrane and a 31 mil thick feed spacer, commonly applied in practice in RO and nanofiltration (NF) spiral-wound membrane modules. Numerical modeling studies were done with identical feed spacer geometry differing in thickness (28, 31 and 34 mil). Additionally, experiments were done applying a forward osmosis (FO) membrane with varying spacer thickness (28, 31 and 34 mil), addressing the permeate flux decline and biofilm development. Assessed were the development of feed channel pressure drop (MFS studies), permeate flux (FO studies) and accumulated biomass amount measured by adenosine triphosphate (ATP) and total organic carbon (TOC). Our studies showed that the organic nutrient load determined the accumulated amount of biomass. The same amount of accumulated biomass was found at constant nutrient load irrespective of linear flow velocity, shear, and/or feed spacer thickness. The impact of the same amount of accumulated biomass on feed channel pressure drop and permeate flux was influenced by membrane process design and operational conditions. Reducing the nutrient load by pretreatment slowed-down the biofilm formation. The impact of accumulated biomass on membrane performance was reduced by applying a lower crossflow velocity and/or a thicker and/or a modified geometry feed spacer. The results indicate that cleanings can be delayed

  16. Transient integral boundary layer method to calculate the translesional pressure drop and the fractional flow reserve in myocardial bridges

    PubMed Central

    Bernhard, Stefan; Möhlenkamp, Stefan; Tilgner, Andreas

    2006-01-01

    Background The pressure drop – flow relations in myocardial bridges and the assessment of vascular heart disease via fractional flow reserve (FFR) have motivated many researchers the last decades. The aim of this study is to simulate several clinical conditions present in myocardial bridges to determine the flow reserve and consequently the clinical relevance of the disease. From a fluid mechanical point of view the pathophysiological situation in myocardial bridges involves fluid flow in a time dependent flow geometry, caused by contracting cardiac muscles overlying an intramural segment of the coronary artery. These flows mostly involve flow separation and secondary motions, which are difficult to calculate and analyse. Methods Because a three dimensional simulation of the haemodynamic conditions in myocardial bridges in a network of coronary arteries is time-consuming, we present a boundary layer model for the calculation of the pressure drop and flow separation. The approach is based on the assumption that the flow can be sufficiently well described by the interaction of an inviscid core and a viscous boundary layer. Under the assumption that the idealised flow through a constriction is given by near-equilibrium velocity profiles of the Falkner-Skan-Cooke (FSC) family, the evolution of the boundary layer is obtained by the simultaneous solution of the Falkner-Skan equation and the transient von-Kármán integral momentum equation. Results The model was used to investigate the relative importance of several physical parameters present in myocardial bridges. Results have been obtained for steady and unsteady flow through vessels with 0 – 85% diameter stenosis. We compare two clinical relevant cases of a myocardial bridge in the middle segment of the left anterior descending coronary artery (LAD). The pressure derived FFR of fixed and dynamic lesions has shown that the flow is less affected in the dynamic case, because the distal pressure partially recovers

  17. Transient integral boundary layer method to calculate the translesional pressure drop and the fractional flow reserve in myocardial bridges.

    PubMed

    Bernhard, Stefan; Möhlenkamp, Stefan; Tilgner, Andreas

    2006-06-21

    The pressure drop-flow relations in myocardial bridges and the assessment of vascular heart disease via fractional flow reserve (FFR) have motivated many researchers the last decades. The aim of this study is to simulate several clinical conditions present in myocardial bridges to determine the flow reserve and consequently the clinical relevance of the disease. From a fluid mechanical point of view the pathophysiological situation in myocardial bridges involves fluid flow in a time dependent flow geometry, caused by contracting cardiac muscles overlying an intramural segment of the coronary artery. These flows mostly involve flow separation and secondary motions, which are difficult to calculate and analyse. Because a three dimensional simulation of the haemodynamic conditions in myocardial bridges in a network of coronary arteries is time-consuming, we present a boundary layer model for the calculation of the pressure drop and flow separation. The approach is based on the assumption that the flow can be sufficiently well described by the interaction of an inviscid core and a viscous boundary layer. Under the assumption that the idealised flow through a constriction is given by near-equilibrium velocity profiles of the Falkner-Skan-Cooke (FSC) family, the evolution of the boundary layer is obtained by the simultaneous solution of the Falkner-Skan equation and the transient von-Kármán integral momentum equation. The model was used to investigate the relative importance of several physical parameters present in myocardial bridges. Results have been obtained for steady and unsteady flow through vessels with 0 - 85% diameter stenosis. We compare two clinical relevant cases of a myocardial bridge in the middle segment of the left anterior descending coronary artery (LAD). The pressure derived FFR of fixed and dynamic lesions has shown that the flow is less affected in the dynamic case, because the distal pressure partially recovers during re-opening of the vessel in

  18. Gas convection caused by electron pressure drop in the afterglow of a pulsed inductively coupled plasma discharge

    SciTech Connect

    Cunge, G.; Vempaire, D.; Sadeghi, N.

    2010-03-29

    Neutral depletion is an important phenomenon in high-density plasmas. We show that in pulsed discharges, the neutral depletion caused by the electron pressure P{sub e} plays an important role on radical transport. In the afterglow, P{sub e} drops rapidly by electron cooling. So, a neutral pressure gradient built up between the plasma bulk and the reactor walls, which forces the cold surrounding gas to move rapidly toward the reactor center. Measured drift velocity of Al atoms in the early afterglow of Cl{sub 2}/Ar discharge by time-resolved laser induced fluorescence is as high as 250 ms{sup -1}. This is accompanied by a rapid gas cooling.

  19. Heat transfer and pressure drop of supercritical carbon dioxide flowing in several printed circuit heat exchanger channel patterns

    SciTech Connect

    Carlson, M.; Kruizenga, A.; Anderson, M.; Corradini, M.

    2012-07-01

    Closed-loop Brayton cycles using supercritical carbon dioxide (SCO{sub 2}) show potential for use in high-temperature power generation applications including High Temperature Gas Reactors (HTGR) and Sodium-Cooled Fast Reactors (SFR). Compared to Rankine cycles SCO{sub 2} Brayton cycles offer similar or improved efficiency and the potential for decreased capital costs due to a reduction in equipment size and complexity. Compact printed-circuit heat exchangers (PCHE) are being considered as part of several SCO{sub 2} Brayton designs to further reduce equipment size with increased energy density. Several designs plan to use a gas cooler operating near the pseudo-critical point of carbon dioxide to benefit from large variations in thermophysical properties, but further work is needed to validate correlations for heat transfer and pressure-drop characteristics of SCO{sub 2} flows in candidate PCHE channel designs for a variety of operating conditions. This paper presents work on experimental measurements of the heat transfer and pressure drop behavior of miniature channels using carbon dioxide at supercritical pressure. Results from several plate geometries tested in horizontal cooling-mode flow are presented, including a straight semi-circular channel, zigzag channel with a bend angle of 80 degrees, and a channel with a staggered array of extruded airfoil pillars modeled after a NACA 0020 airfoil with an 8.1 mm chord length facing into the flow. Heat transfer coefficients and bulk temperatures are calculated from measured local wall temperatures and local heat fluxes. The experimental results are compared to several methods for estimating the friction factor and Nusselt number of cooling-mode flows at supercritical pressures in millimeter-scale channels. (authors)

  20. Effects of pressure drop, particle size and thermal conditions on retention and efficiency in supercritical fluid chromatography.

    PubMed

    Poe, Donald P; Schroden, Jonathan J

    2009-11-06

    The effects of particle size and thermal insulation on retention and efficiency in packed-column supercritical fluid chromatography with large pressure drops are described for the separation of a series of model n-alkane solutes. The columns were 2.0mm i.d.x150mm long and were packed with 3, 5, or 10-mum porous octylsilica particles. Separations were performed with pure carbon dioxide at 50 degrees C at average mobile phase densities of 0.47g/mL (107bar) and 0.70g/mL (151bar). The three principal causes of band broadening were the normal dispersion processes described by the van Deemter equation, changes in the retention factor due to the axial density gradient, and radial temperature gradients associated with expansion of the mobile phase. At the lower density the use of thermal insulation resulted in significant improvements in efficiency and decreased retention times at large pressure drops. The effects are attributed to the elimination of radial temperature gradients and the concurrent enhancement of the axial temperature gradient. Thermal insulation had no significant effect on chromatographic performance at the higher density. A simple expression to predict the onset of excess efficiency loss due to the radial temperature gradient is proposed.

  1. Condensation heat transfer and pressure drop of R-410A in flat aluminum multi-port tubes

    NASA Astrophysics Data System (ADS)

    Kim, Nae-Hyun

    2017-09-01

    Brazed heat exchangers with aluminum flat multi-port tubes are being used as condensers of residential air-conditioners. In this study, R-410A condensation tests were conducted in four multi-port tubes having a range of hydraulic diameter (0.78 ≤ Dh ≤ 0.95 mm). The test range covered the mass flux from 100 to 400 kg/m2 s and the heat flux at 3 kW/m2, which are typical operating conditions of residential air conditioners. Results showed that both the heat transfer coefficient and the pressure drop increased as the hydraulic diameter decreased. The effect of hydraulic diameter on condensation heat transfer was much larger than the predictions of existing correlations for the range of investigation. Comparison of the data with the correlations showed that some macro-channel tube correlations and mini-channel tube correlations reasonably predicted the heat transfer coefficient. However, macro-channel correlations highly overpredicted the pressure drop data.

  2. Experimental and numerical investigation of pressure drop and heat transfer coefficient in converging-diverging microchannel heat sink

    NASA Astrophysics Data System (ADS)

    Chakravarthii, M. K. Dheepan; Mutharasu, D.; Shanmugan, S.

    2017-07-01

    The major challenge in microelectronic chips is to eliminate the generated heat for stable and reliable operation of the devices. Microchannel heat sinks are efficient method to dissipate high heat flux. The pressure drop and heat transfer coefficient are the important parameters which determine the thermal-hydraulic performance of the microchannel heat sink. In this study, a converging-diverging (CD) microchannel heat sink was experimentally investigated for the variation of pressure drop and heat transfer coefficient. De-ionized water was considered as the working fluid. Experiments were conducted for single phase fluid flow with mass flow rate and heat flux ranging from 0.001232 to 0.01848 kg/s and 10-50 W/cm2 respectively. The fluid and solid temperature were measured to calculate the heat transfer coefficients. Numerical results were computed using the CFD software and validated against the experimental results. The CD microchannel possesses high heat transfer coefficient than the straight microchannels. Theoretical correlations were proposed for comparing the experimental Nusselt number of CD microchannel. Evaluation of thermal-hydraulic performance of CD microchannel is important to quantify its applications in electronics cooling.

  3. A simple expression for pressure drops of water and other low molecular liquids in the flow through micro-orifices

    NASA Astrophysics Data System (ADS)

    Hasegawa, Tomiichi; Ushida, Akiomi; Narumi, Takatsune

    2015-12-01

    Flows are generally divided into two types: shear flows and shear-free elongational (extensional) flows. Both are necessary for a thorough understanding of the flow properties of a fluid. Shear flows are easy to achieve in practice, for example, through Poiseuille or Couette flows. Shear-free elongational flows are experimentally hard to achieve, resulting in an incomplete understanding of the flow properties of fluids in micro-devices. Nevertheless, flows through micro-orifices are useful for probing the properties of elongational flows at high elongational rates; although these flows exhibit shear and elongation, the elongation is dominant and the shear is negligible in the central region of the flows. We previously reported an anomalous reduction in pressure drops in the flows of water, a 50/50 mixture of glycerol and water, and silicone oils through micro-orifices. In the present paper, we rearrange the data presented in the previous paper and reveal a simple relationship where the pressure drop is proportional to the velocity through the micro-orifices, independent of the orifice diameter and the viscosity of the liquids tested. We explain our observations by introducing a "fluid element" model, in which fluid elements are formed on entering the orifice. The model is based on the idea that low molecular liquids, including water, generate strong elongational stress, similar to a polymer solution, in the flow through micro-orifices.

  4. Evaluation of static pressure drops and PM10 and TSP emissions for modified 1D-3D cyclones

    SciTech Connect

    Holt, G.A.; Baker, R.V.; Hughs, S.E.

    1999-12-01

    Five modifications of a standard 1D3D cyclone were tested and compared against the standard 1D3D design in the areas of particulate emissions and static pressure drop across the cyclone. The modifications to the 1D3D design included a 2D2D inlet, a 2D2D air outlet, a D/3 trash exit, an expansion chamber with a D/3 trash exit, and a tapered air outlet duct. The 1D3D modifications that exhibited a significant improvement in reducing both PM10 and total suspended particulate (TSP) emissions were the designs with the 2D2D inlet and air exhaust combined with either the conical D/3 tail cone or the expansion chamber. In reference to the standard 1D3D cyclone, the average reduction in PM10 emissions was 24 to 29% with a 29 to 35% reduction observed in TSP emissions. The modifications with the tapered air outlets did not show any significant improvements in controlling PM10 emissions. However, the modification with the tapered air outlet/expansion chamber combination exhibited statistical significance in reducing TSP emissions by 18% compared to the 1D3D cyclone. All modifications tested exhibited lower static pressure drops than the standard 1D3D.

  5. Pressure drop and heat transfer of Al2O3-H2O nanofluids through silicon microchannels

    NASA Astrophysics Data System (ADS)

    Wu, Xinyu; Wu, Huiying; Cheng, Ping

    2009-10-01

    Experimental investigations were performed on the single-phase flow and heat transfer characteristics through the silicon-based trapezoidal microchannels with a hydraulic diameter of 194.5 µm using Al2O3-H2O nanofluids with particle volume fractions of 0, 0.15% and 0.26% as the working fluids. The effects of the Reynolds number, Prandtl number and nanoparticle concentration on the pressure drop and convective heat transfer were investigated. Experimental results show that the pressure drop and flow friction of the nanofluids increased slightly when compared with that of the pure water, while the Nusselt number increased considerably. At the same pumping power, using nanofluids instead of pure water caused a reduction in the thermal resistance. It was also found that the Nusselt number increased with the increase in the particle concentration, Reynolds number and Prandtl number. Based on the experimental data, the dimensionless correlations for the flow friction and heat transfer of Al2O3-H2O nanofluids through silicon microchannels were proposed for the first time. The agglomeration and deposition of nanoparticles in the silicon microchannels were also examined in this paper. It was found that the Al2O3 nanoparticles deposited on the inner wall of microchannels more easily with increasing wall temperature, and once boiling commenced, there is a severe deposition and adhesion of nanoparticles to the inner wall, which makes the boiling heat transfer of nanofluids in silicon microchannels questionable.

  6. In vitro comparison of Günther Tulip and Celect filters: testing filtering efficiency and pressure drop.

    PubMed

    Nicolas, M; Malvé, M; Peña, E; Martínez, M A; Leask, R

    2015-02-05

    In this study, the trapping ability of the Günther Tulip and Celect inferior vena cava filters was evaluated. Thrombus capture rates of the filters were tested in vitro in horizontal position with thrombus diameters of 3 and 6mm and tube diameter of 19mm. The filters were tested in centered and tilted positions. Sets of 30 clots were injected into the model and the same process was repeated 20 times for each different condition simulated. Pressure drop experienced along the system was also measured and the percentage of clots captured was recorded. The Günther Tulip filter showed superiority in all cases, trapping almost 100% of 6mm clots both in an eccentric and tilted position and trapping 81.7% of the 3mm clots in a centered position and 69.3% in a maximum tilted position. The efficiency of all filters tested decreased as the size of the embolus decreased and as the filter was tilted. The injection of 6 clots raised the pressure drop to 4.1mmHg, which is a reasonable value that does not cause the obstruction of blood flow through the system. Copyright © 2014 Elsevier Ltd. All rights reserved.

  7. Al-Coated Conductive Fibrous Filter with Low Pressure Drop for Efficient Electrostatic Capture of Ultrafine Particulate Pollutants.

    PubMed

    Choi, Dong Yun; Jung, Soo-Ho; Song, Dong Keun; An, Eun Jeong; Park, Duckshin; Kim, Tae-Oh; Jung, Jae Hee; Lee, Hye Moon

    2017-05-17

    Here, we demonstrate a new strategy of air filtration based on an Al-coated conductive fibrous filter for high efficient nanoparticulate removals. The conductive fibrous filter was fabricated by a direct decomposition of Al precursor ink, AlH3{O(C4H9)2}, onto surfaces of a polyester air filter via a cost-effective and scalable solution-dipping process. The prepared conductive filters showed a low sheet resistance (<1.0 Ω sq(-1)), robust mechanical durability and high oxidative stability. By electrostatic force between the charged fibers and particles, the ultrafine particles of 30-400 nm in size were captured with a removal efficiency of ∼99.99%. Moreover, the conductive filters exhibited excellent performances in terms of the pressure drop (∼4.9 Pa at 10 cm s(-1)), quality factor (∼2.2 Pa(-1) at 10 cm s(-1)), and dust holding capacity (12.5 μg mm(-2)). After being cleaned by water, the filtration efficiency and pressure drop of the conductive filter was perfectly recovered, which indicates its good recyclability. It is expected that these promising features make the conductive fibrous filter have a great potential for use in low-cost and energy-efficient air cleaning devices as well as other relevant research areas.

  8. Experimental and numerical investigation of pressure drop and heat transfer coefficient in converging-diverging microchannel heat sink

    NASA Astrophysics Data System (ADS)

    Chakravarthii, M. K. Dheepan; Mutharasu, D.; Shanmugan, S.

    2017-01-01

    The major challenge in microelectronic chips is to eliminate the generated heat for stable and reliable operation of the devices. Microchannel heat sinks are efficient method to dissipate high heat flux. The pressure drop and heat transfer coefficient are the important parameters which determine the thermal-hydraulic performance of the microchannel heat sink. In this study, a converging-diverging (CD) microchannel heat sink was experimentally investigated for the variation of pressure drop and heat transfer coefficient. De-ionized water was considered as the working fluid. Experiments were conducted for single phase fluid flow with mass flow rate and heat flux ranging from 0.001232 to 0.01848 kg/s and 10-50 W/cm2 respectively. The fluid and solid temperature were measured to calculate the heat transfer coefficients. Numerical results were computed using the CFD software and validated against the experimental results. The CD microchannel possesses high heat transfer coefficient than the straight microchannels. Theoretical correlations were proposed for comparing the experimental Nusselt number of CD microchannel. Evaluation of thermal-hydraulic performance of CD microchannel is important to quantify its applications in electronics cooling.

  9. Bed mixing and leachate recycling strategies to overcome pressure drop buildup in the biofiltration of hydrogen sulfide.

    PubMed

    Roshani, Babak; Torkian, Ayoob; Aslani, Hasan; Dehghanzadeh, Reza

    2012-04-01

    The effects of leachate recycling and bed mixing on the removal rate of H(2)S from waste gas stream were investigated. The experimental setup consisted of an epoxy-coated three-section biofilter with an ID of 8 cm and effective bed height of 120 cm. Bed material consisted of municipal solid waste compost and PVC bits with an overall porosity of 54% and dry bulk density of 0.456 g cm(-3). Leachate recycling had a positive effect of increasing elimination capacity (EC) up to 21 g S m(-3) bed h(-1) at recycling rates of 75 ml d(-1), but in the bed mixing period EC declined to 8 g S m(-3) bed h(-1). Pressure drop had a range of zero to 18 mm H(2)O m(-1) in the course of leachate recycling. Accumulation of sulfur reduced removal efficiency and increased pressure drop up to 110 mm H(2)O m(-1) filter during the bed mixing stage. Copyright © 2012 Elsevier Ltd. All rights reserved.

  10. The effect of flexible tube vibration on pressure drop and heat transfer in heat exchangers considering viscous dissipation effects

    NASA Astrophysics Data System (ADS)

    Shokouhmand, H.; Sangtarash, F.

    2008-04-01

    The pressure drop and heat transfer coefficient in tube bundle of shell and tube heat exchangers are investigated considering viscous dissipation effects. The governing equations are solved numerically. Because of temperature-dependent viscosity the equations should be solved simultaneously. The flexible tubes vibration is modeled in a quasi-static method by taking the first tube of the row to be in 20 asymmetric positions with respect to the rest of the tubes which are assumed to be fixed and time averaging the steady state solutions corresponding to each one of these positions .The results show that the eccentricity of the first tube increases pressure drop and heat transfer coefficients significantly comparing to the case of rigid tube bundles, symmetrically placed. In addition, these vibrations not only compensate the effect of viscous dissipations on heat transfer coefficient but also increase heat transfer coefficient. The constant viscosity results obtained from our numerical method have a good agreement with the available experimental data of constant viscosity for flexible tube heat exchangers.

  11. [Probability of altitude decompression sickness following a drop in pressure from 840 to 308 mm Hg].

    PubMed

    Barer, A S; Vakar, M I; Vorob'ev, G F; Iseev, L R; Filipenkov, S N

    1982-01-01

    The decompression from the hyperbaric air atmosphere with the pressure 840+/-5 mm Hg and subsequent 40 min exposure to the hypobaric atmosphere 308+/-1 mm Hg containing 40 to 95% O2 cause a decompression disease in 5-40% cases. The probability of the disease depends on the duration of nitrogen saturation at an increased pressure, physical fitness and individual susceptibility to decompression sickness.

  12. Condensation heat transfer and pressure drop of R-134a saturated vapour inside a brazed compact plate fin heat exchanger with serrated fin

    NASA Astrophysics Data System (ADS)

    Ramana Murthy, K. V.; Ranganayakulu, C.; Ashok Babu, T. P.

    2017-01-01

    This paper presents the experimental heat transfer coefficient and pressure drop measured during R-134a saturated vapour condensation inside a small brazed compact plate fin heat exchanger with serrated fin surface. The effects of saturation temperature (pressure), refrigerant mass flux, refrigerant heat flux, effect of fin surface characteristics and fluid properties are investigated. The average condensation heat transfer coefficients and frictional pressure drops were determined experimentally for refrigerant R-134a at five different saturated temperatures (34, 38, 40, 42 and 44 °C). A transition point between gravity controlled and forced convection condensation has been found for a refrigerant mass flux around 22 kg/m2s. In the forced convection condensation region, the heat transfer coefficients show a three times increase and 1.5 times increase in frictional pressure drop for a doubling of the refrigerant mass flux. The heat transfer coefficients show weak sensitivity to saturation temperature (Pressure) and great sensitivity to refrigerant mass flux and fluid properties. The frictional pressure drop shows a linear dependence on the kinetic energy per unit volume of the refrigerant flow. Correlations are provided for the measured heat transfer coefficients and frictional pressure drops.

  13. Pressure drop, flow pattern and local water volume fraction measurements of oil-water flow in pipes

    NASA Astrophysics Data System (ADS)

    Kumara, W. A. S.; Halvorsen, B. M.; Melaaen, M. C.

    2009-11-01

    Oil-water flow in horizontal and slightly inclined pipes was investigated. The experimental activities were performed using the multiphase flow loop at Telemark University College, Porsgrunn, Norway. The experiments were conducted in a 15 m long, 56 mm diameter, inclinable steel pipe using Exxsol D60 oil (density of 790 kg m-3 and viscosity of 1.64 mPa s) and water (density of 996 kg m-3 and viscosity of 1.00 mPa s) as test fluids. The test pipe inclination was changed in the range from 5° upward to 5° downward. Mixture velocity and inlet water cut vary up to 1.50 m s-1 and 0.975, respectively. The time-averaged cross-sectional distributions of oil and water were measured with a single-beam gamma densitometer. The pressure drop along the test section of the pipe was also measured. The characterization of flow patterns and identification of their boundaries are achieved via visual observations and by analysis of local water volume fraction measurements. The observed flow patterns were presented in terms of flow pattern maps for different pipe inclinations. In inclined flows, dispersions appear at lower mixture velocities compared to the horizontal flows. Smoothly stratified flows observed in the horizontal pipe disappeared in upwardly inclined pipes and new flow patterns, plug flow and stratified wavy flow were observed. The water-in-oil dispersed flow regime slightly shrinks as the pipe inclination increases. In inclined flows, the dispersed oil-in-water flow regime extended to lower mixture velocities and lower inlet water cuts. The present experimental data were compared with the results of a flow-pattern-dependent prediction model, which uses the area-averaged steady-state two-fluid model for stratified flow and the homogeneous model for dispersed flow. The two-fluid model was able to predict the pressure drop and water hold-up for stratified flow. The homogeneous model was not able to predict the pressure profile of dispersed oil-water flow at higher water

  14. Pressure drop testing of corrugated stainless steel pliable gas tubing (PLT)

    NASA Astrophysics Data System (ADS)

    Srinivasan, Bharadwaj

    An experimental program was initiated to determine the Darcy friction factor in straight corrugated stainless steel pliable gas tubing (PLT). Pressure loss tests were conducted on PLT per I.S. EN 15266:2007. A power law least-squares curve fit was used to relate pressure loss per unit length as a function of volume flow rate. The calculated coefficient of determination values for the straight PLT exceeded 0.90 indicating suitable correlation. Darcy friction factors were calculated from test data for each case and plotted on a Moody diagram as a function of Reynolds number based on the minimum PLT cross section. For Reynolds numbers less than 2300 the pressure loss data for PLT yielded an inverse relationship between the Darcy friction factor and the Reynolds number, with a proportionality coefficient of 49. The measurement uncertainty estimates for straight sections was performed with a 95% confidence level. Straight PLT flow rates for air and representative fuel gases that would yield a pressure loss Deltap = 1 mbar were calculated as a function of PLT length and diameter. Fitting pressure loss tests were performed for elbows, tees, and bullhead tees. The loss coefficients were evaluated and tabulated. The calculated coefficient of determination values for the fittings was found to be low. The measurement uncertainty was calculated using the root sum square error method and was found to be very high because of the low flow rates considered in this experiment.

  15. Fluctuation emergence of bubbles under a rapid drop of pressure in a liquid

    NASA Astrophysics Data System (ADS)

    Pavlov, P. A.; Vinogradov, V. E.

    2015-07-01

    Explosive cavitation at the front of a negative-pressure pulse has been studied. Conditions for the emergence of bubbles by the mechanism of homogeneous fluctuation nucleation were identified. Those conditions feature a high rate of the phase transformation, with the vapor formation process being concentrated in time at the instant of attainment of a certain pressure. Under such conditions, the liquid cavitation strength is maximal, and its value can be predicted by the homogeneous nucleation theory. For implementing the regime with high nucleation frequency, a method based on passing a negative-pressure pulse across a region with locally heated liquid was employed. The cavitation kinetics was examined by monitoring the perturbation of the heat flow from a miniature heater. The experimental data were generalized using the theory of explosive vapor formation in shock boiling mode. A method for calculating the cavitation in the regime of the fluctuation emergence of bubbles was approbated.

  16. Earthquake dynamics. Mapping pressurized volcanic fluids from induced crustal seismic velocity drops.

    PubMed

    Brenguier, F; Campillo, M; Takeda, T; Aoki, Y; Shapiro, N M; Briand, X; Emoto, K; Miyake, H

    2014-07-04

    Volcanic eruptions are caused by the release of pressure that has accumulated due to hot volcanic fluids at depth. Here, we show that the extent of the regions affected by pressurized fluids can be imaged through the measurement of their response to transient stress perturbations. We used records of seismic noise from the Japanese Hi-net seismic network to measure the crustal seismic velocity changes below volcanic regions caused by the 2011 moment magnitude (M(w)) 9.0 Tohoku-Oki earthquake. We interpret coseismic crustal seismic velocity reductions as related to the mechanical weakening of the pressurized crust by the dynamic stress associated with the seismic waves. We suggest, therefore, that mapping seismic velocity susceptibility to dynamic stress perturbations can be used for the imaging and characterization of volcanic systems.

  17. Two-phase flow heat transfer and pressure drop characteristics of R-22 and R-32/125

    SciTech Connect

    Wijaya, H.; Spatz, M.W.

    1995-08-01

    The two-phase heat transfer coefficient and pressure drop characteristics of refrigerants R-22 and R-32/125 (ASI 1990) (a mixture of 50 wt% R-32 and 50 wt% R-125 that exhibits azeotropic behavior) have been measured. The experiments were conducted without oil in the refrigerant loop. The condenser/evaporator test sections consist of smooth, horizontal copper tubes of 3/8-in. (9.53-mm) outer diameter (OD) and 0.305-in. (7.75-mm) inner diameter (ID). A lengths of the condenser and evaporator test sections are 10 ft (3.05 m) and 12 ft (3.66 m), respectively. The condenser is a counterflow heat exchanger with refrigerant flowing in the inner tube and a water-glycol mixture flowing in the annulus. The evaporator is a smooth copper tube sandwiched with aluminum blocks. Heating tapes are wrapped around the outer surface of these aluminum blocks. The average saturated condensing temperatures were 115 F (46.1 C) and 125 F (51.7 C), while the saturated evaporating temperature was 40 F (4.4 C). The average inlet and exit qualities for the condensation tests were 87% and 25%, respectively and for the evaporation tests they were 20% and 90%, respectively. The mass flux was varied from 118 klb/ft{sup 2}{minus}{center_dot}h (160 kg/s{center_dot}m{sup 2}) to 414 klb/ft{sup 2}{center_dot}h (561 kg/s{center_dot}m{sup 2}). A differential pressure transducer was used to measure the pressure drop across the test section. The results showed that at similar mass fluxes the condensation heat transfer coefficients for R-32/125 were slightly higher (about 2% to 6%) than those of R-22.

  18. Experimental studies on the enhanced flow boiling heat transfer and pressure drop of organic fluid with high saturation temperature in vertical porous coated tube

    NASA Astrophysics Data System (ADS)

    Yang, Dong; Shen, Zhi; Chen, Tingkuan; Zhou, Chenn Q.

    2013-07-01

    The characteristics of flow boiling heat transfer and pressure drop of organic fluid with high saturation temperature in a vertical porous coated tube are experimentally studied in this paper. The experiments are performed at evaporation pressure of 0.16-0.31MPa, mass flux of 390-790kg/m2s, and vapor quality of 0.06-0.58. The variations of heat transfer coefficient and pressure drop with vapor quality are measured and compared to the results of smooth tube. Boiling curves are generated at mass flux of 482 and 675kg/m2s. The experimental results indicate that the heat transfer coefficients of the porous tube are 1.8-3.5 times those of smooth tube, and that the frictional pressure drops of the porous tube are 1.1-2.9 times those of smooth tube. The correlations for heat transfer coefficient and frictional pressure drop are derived, in which the effect of fluid molecular weight is included. The experiments show that significant heat transfer enhancement is accompanied by a little pressure drop penalty, the application of the porous coated tube is promising in the process industries.

  19. Computational and experimental investigation of the drag reduction and the components of pressure drop in horizontal slug flow using liquids of different viscosities

    SciTech Connect

    Daas, Mutaz; Bleyle, Derek

    2006-03-01

    Computational and experimental investigation in 10-cm ID horizontal pipes have been carried out utilizing carbon dioxide as the gas phase and two types of oil with different viscosities; namely 0.0025Pas and 0.05Pas, as the liquid phase. The influence of oil viscosity on the magnitude of total pressure drop and each of its components as well as the effectiveness of a drag reducing additive (DRA, CDR WS 500M flow improver) in decreasing the pressure loss was investigated in two-phase oil-gas slug flow. The effects of changing oil viscosity on the contribution of frictional and accelerational components to total pressure drop in slug flow were also examined and analyzed. Computations of accelerational and frictional components of pressure drop were performed. The accelerational component of pressure drop was dominant in the 0.0025Pas oil while the frictional component had significant contributions in the 0.05Pas oil. Despite the fact that the magnitude of drag reduction was higher in the 0.05Pas oil, the DRA was more effective in reducing the total pressure drop and its components in the 0.0025Pas oil. (author)

  20. Two-phase flow boiling frictional pressure drop of liquid nitrogen in horizontal circular mini-tubes: Experimental investigation and comparison with correlations

    NASA Astrophysics Data System (ADS)

    Chen, Xingya; Chen, Shuangtao; Chen, Jun; Li, Jiapeng; Liu, Xiufang; Chen, Liang; Hou, Yu

    2017-04-01

    The two-phase flow boiling characteristics of liquid nitrogen (LN2) in horizontal circular mini-tubes were experimentally studied. Experiments were performed in a wide range of flow conditions, e.g. inlet pressure from 0.17 to 0.35 MPa, mass flux from 140 to 330 kg/m2 s, heat flux from 0.5 to 69.4 kW/m2 and tube diameters of 2.92 mm and 3.96 mm. The influences of mass flux, heat flux, and inlet pressure on the pressure drop were discussed. The results indicated that the pressure drop increases with the increasing mass flux and heat flux but decreases with the increasing inlet pressure. But the influence of heat flux on the frictional pressure drop of LN2 was weaker than mass flux and inlet pressure. The frictional pressure drop of two-phase flow of LN2 was compared with homogeneous model and several semi-empirical correlations. An improved correlation based on the Lockhart-Martinelli model, which used coefficient C as a function of Reynolds number and Weber number was proposed.

  1. Pressure Drop Across Woven Screens Under Uniform and Nonuniform Flow Conditions. [flow characteristics of water through Dutch twill and square weave fabrics

    NASA Technical Reports Server (NTRS)

    Ludewig, M.; Omori, S.; Rao, G. L.

    1974-01-01

    Tests were conducted to determine the experimental pressure drop and velocity data for water flowing through woven screens. The types of materials used are dutch twill and square weave fabrics. Pressure drop measures were made at four locations in a rectangular channel. The data are presented as change in pressure compared with the average entry velocity and the numerical relationship is determined by dividing the volumetric flow rate by the screen area open to flow. The equations of continuity and momentum are presented. A computer program listing an extension of a theoretical model and data from that computer program are included.

  2. Evaluation of the anti-Acanthamoeba activity of two commercial eye drops commonly used to lower eye pressure.

    PubMed

    Sifaoui, Ines; Reyes-Batlle, María; López-Arencibia, Atteneri; Wagner, Carolina; Chiboub, Olfa; De Agustino Rodríguez, Jacqueline; Rocha-Cabrera, Pedro; Valladares, Basilio; Piñero, José E; Lorenzo-Morales, Jacob

    2017-08-01

    Efficient treatments against Acanthamoeba Keratitis (AK), remains until the moment, as an issue to be solved due to the existence of a cyst stage which is highly resistant to most chemical and physical agents. In this study, two antiglaucoma eye drops were tested for their activity against Acanthamoeba. Moreover, this study was based on previous data which gave us evidence of a possible link between the absences of Acanthamoeba at the ocular surface in patients treated with beta blockers for high eye pressure both containing timolol as active principle. The amoebicidal activity of the tested eye drops was evaluated against four strains of Acanthamoeba using Alamar blue method. For the most active drug the cysticidal activity against A. castellanii Neff cysts and further experiments studying changes in chromatin condensation levels, in the permeability of the plasmatic membrane, the mitochondrial membrane potential and the ATP levels in the treated amoebic strains were done. Even though both eye drops were active against the different tested strains of Acanthamoeba, statistical analysis revealed that one of them (Timolol Sandoz) was the most effective one against all the tested strains presenting IC50s ranging from 0.529% ± 0.206 for the CLC 16 strain to 3.962% ± 0.150 for the type strain Acanthamoeba castellanii Neff. Timolol Sandoz 0.50% seems to induce amoebic cell death by damaging the amoebae at the mitochondrial level. Considering its effect, Timolol Sandoz 0.50% could be used in the case of contact lens wearers and patients with glaucoma. Copyright © 2017. Published by Elsevier Inc.

  3. Numerical simulation of blood flow and pressure drop in the pulmonary arterial and venous circulation.

    PubMed

    Qureshi, M Umar; Vaughan, Gareth D A; Sainsbury, Christopher; Johnson, Martin; Peskin, Charles S; Olufsen, Mette S; Hill, N A

    2014-10-01

    A novel multiscale mathematical and computational model of the pulmonary circulation is presented and used to analyse both arterial and venous pressure and flow. This work is a major advance over previous studies by Olufsen et al. (Ann Biomed Eng 28:1281-1299, 2012) which only considered the arterial circulation. For the first three generations of vessels within the pulmonary circulation, geometry is specified from patient-specific measurements obtained using magnetic resonance imaging (MRI). Blood flow and pressure in the larger arteries and veins are predicted using a nonlinear, cross-sectional-area-averaged system of equations for a Newtonian fluid in an elastic tube. Inflow into the main pulmonary artery is obtained from MRI measurements, while pressure entering the left atrium from the main pulmonary vein is kept constant at the normal mean value of 2 mmHg. Each terminal vessel in the network of 'large' arteries is connected to its corresponding terminal vein via a network of vessels representing the vascular bed of smaller arteries and veins. We develop and implement an algorithm to calculate the admittance of each vascular bed, using bifurcating structured trees and recursion. The structured-tree models take into account the geometry and material properties of the 'smaller' arteries and veins of radii ≥ 50 μm. We study the effects on flow and pressure associated with three classes of pulmonary hypertension expressed via stiffening of larger and smaller vessels, and vascular rarefaction. The results of simulating these pathological conditions are in agreement with clinical observations, showing that the model has potential for assisting with diagnosis and treatment for circulatory diseases within the lung.

  4. Numerical simulation of blood flow and pressure drop in the pulmonary arterial and venous circulation

    PubMed Central

    Qureshi, M. Umar; Vaughan, Gareth D.A.; Sainsbury, Christopher; Johnson, Martin; Peskin, Charles S.; Olufsen, Mette S.; Hill, N.A.

    2014-01-01

    A novel multiscale mathematical and computational model of the pulmonary circulation is presented and used to analyse both arterial and venous pressure and flow. This work is a major advance over previous studies by Olufsen and coworkers (Ottesen et al., 2003; Olufsen et al., 2012) which only considered the arterial circulation. For the first three generations of vessels within the pulmonary circulation, geometry is specified from patient-specific measurements obtained using magnetic resonance imaging (MRI). Blood flow and pressure in the larger arteries and veins are predicted using a nonlinear, cross-sectional-area-averaged system of equations for a Newtonian fluid in an elastic tube. Inflow into the main pulmonary artery is obtained from MRI measurements, while pressure entering the left atrium from the main pulmonary vein is kept constant at the normal mean value of 2 mmHg. Each terminal vessel in the network of ‘large’ arteries is connected to its corresponding terminal vein via a network of vessels representing the vascular bed of smaller arteries and veins. We develop and implement an algorithm to calculate the admittance of each vascular bed, using bifurcating structured trees and recursion. The structured-tree models take into account the geometry and material properties of the ‘smaller’ arteries and veins of radii ≥ 50µm. We study the effects on flow and pressure associated with three classes of pulmonary hypertension expressed via stiffening of larger and smaller vessels, and vascular rarefaction. The results of simulating these pathological conditions are in agreement with clinical observations, showing that the model has potential for assisting with diagnosis and treatment of circulatory diseases within the lung. PMID:24610385

  5. Short term Heart Rate Variability to predict blood pressure drops due to standing: a pilot study.

    PubMed

    Sannino, G; Melillo, P; Stranges, S; De Pietro, G; Pecchia, L

    2015-01-01

    Standing from a bed or chair may cause a significant lowering of blood pressure (ΔBP), which may have severe consequences such as, for example, falls in older subjects. The goal of this study was to develop a mathematical model to predict the ΔBP due to standing in healthy subjects, based on their Heart Rate Variability, recorded in the 5 minutes before standing. Heart Rate Variability was extracted from an electrocardiogram, recorded from 10 healthy subjects during the 5 minutes before standing. The blood pressure value was measured before and after rising. A mathematical model aiming to predict ΔBP based on Heart Rate Variability measurements was developed using a robust multi-linear regression and was validated with the leave-one-subject-out cross-validation technique. The model predicted correctly the ΔBP in 80% of experiments, with an error below the measurement error of sphygmomanometer digital devices (± 4.5 mmHg), a false negative rate of 7.5% and a false positive rate of 10%. The magnitude of the ΔBP was associated with a depressed and less chaotic Heart Rate Variability pattern. The present study showes that blood pressure lowering due to standing can be predicted by monitoring the Heart Rate Variability in the 5 minutes before standing.

  6. Short term Heart Rate Variability to predict blood pressure drops due to standing: a pilot study

    PubMed Central

    2015-01-01

    Background Standing from a bed or chair may cause a significant lowering of blood pressure (ΔBP), which may have severe consequences such as, for example, falls in older subjects. The goal of this study was to develop a mathematical model to predict the ΔBP due to standing in healthy subjects, based on their Heart Rate Variability, recorded in the 5 minutes before standing. Methods Heart Rate Variability was extracted from an electrocardiogram, recorded from 10 healthy subjects during the 5 minutes before standing. The blood pressure value was measured before and after rising. A mathematical model aiming to predict ΔBP based on Heart Rate Variability measurements was developed using a robust multi-linear regression and was validated with the leave-one-subject-out cross-validation technique. Results The model predicted correctly the ΔBP in 80% of experiments, with an error below the measurement error of sphygmomanometer digital devices (±4.5 mmHg), a false negative rate of 7.5% and a false positive rate of 10%. The magnitude of the ΔBP was associated with a depressed and less chaotic Heart Rate Variability pattern. Conclusions The present study showes that blood pressure lowering due to standing can be predicted by monitoring the Heart Rate Variability in the 5 minutes before standing. PMID:26391336

  7. Computational investigation of heat transfer and pressure drop in a typical louver fin-and-tube heat exchanger for various louver angles and fin pitches

    NASA Astrophysics Data System (ADS)

    Okbaz, Abdulkerim; Olcay, Ali Bahadır; Cellek, Mehmet Salih; Pınarbaşı, Ali

    In this study 3-D numerical simulations on heat transfer and pressure drop characteristics for a typical louver fin-and- double-row tube heat exchanger were carried out. The heat transfer improvement and the corresponding pressure drop amounts were investigated depending on louver angles, fin pitch and Reynolds number, and reported in terms of Colburn j-factor and Fanning friction factor f. The heat transfer improvement and the corresponding pressure drop amounts were investigated depending on louver angles between 20° ≤Ө≤ 30°, louver pitch of Lp=3.8 mm and frontal velocities of U between 1.22 m/s - 3 m/s. In addition, flow visualization of detailed flow features results, such as velocity vectors, streamlines and temperature counters have been shown to understand heat transfer enhancement mechanism. The present results indicated that louver angle and fin pitch noticeably affected the thermal and hydraulic performance of heat exchanger. It has been seen that increasing louver angle, increases thermal performance while decreasing hydraulic performance associated to pressure drop for fin pitches of 3.2 mm and 2.5 mm. Fin pitch determines the flow behaviour that for fin pitch of 2 mm, increasing louver angle decreased heat transfer and pressure drop. Velocity vectors and streamlines give considerable information about the flow whether it is duct directed or louver directed. For all conditions the flow is louver directed.

  8. Pressure-drop viscosity measurements for gamma-Al2O nanoparticles in water and PG-water mixtures (nanofluids).

    PubMed

    Lai, W Y; Phelan, P E; Prasher, R S

    2010-12-01

    Nanofluids have attracted wide attention because of their promising thermal applications. Compared with the base fluid, numerous experiments have generally indicated increases in effective thermal conductivity and convective heat transfer coefficient for suspensions having only a small amount of nanoparticles. It is also known that with the presence of nanoparticles, the viscosity of a nanofluid is greater than its base fluid and deviates from Einstein's classical prediction. However, only a few groups have reported nanofluid viscosity results to date. Therefore, relative viscosity data for gamma-Al2O3 nanoparticles in DI-water and propylene glycol/H2O mixtures are presented here based on pressure drop measurements of flowing nanofluids. Results indicate that with constant wall heat flux, the relative viscosities of nanofluid decrease with increasing volume flow rate. The results also show, based on Brenner's model, that the nanofluid viscosity can be explained in part by the aspect ratio of the aggregates.

  9. Glaucoma drops control intraocular pressure and protect optic nerves in a rat model of glaucoma.

    PubMed

    Morrison, J C; Nylander, K B; Lauer, A K; Cepurna, W O; Johnson, E

    1998-03-01

    To determine whether chronic topical glaucoma therapy can control intraocular pressure (IOP) and protect nerve fibers in a rat model of pressure-induced optic nerve damage. Sixteen adult Brown Norway rats were-administered unilateral episcleral vein injections of hypertonic saline to produce scarring of the aqueous humor outflow pathways. Twice daily applications of either artificial tears (n = 6), 0.5% betaxolol (n = 5), or 0.5% apraclonidine (n = 5) were delivered to both eyes, and awake pressures were monitored with a TonoPen XL tonometer for 17 days before the rats were killed. For animals administered artificial tears, the mean IOP of the experimental eyes was 39 +/- 2 mm Hg compared with 29 +/- 1 mm Hg for the control eyes. This difference was statistically significant (P < 0.001). Mean IOPs in the experimental eyes of animals administered betaxolol and apraclonidine were 29 +/- 7 and 29 +/- 4 mm Hg, respectively, whereas the mean IOP in the control eyes was 28 +/- 1 mm Hg for both groups. There was no statistically significant difference among these values. The mean IOP for the experimental eyes in the betaxolol and apraclonidine groups was lower than that in animals administered artificial tears (P = 0.003). Quantitative histologic analysis of optic nerve damage in experimental eyes showed that four of the six animals administered artificial tears had damage involving 100% of the neural area. This degree of damage appeared in only 3 of 10 animals administered glaucoma therapy. Optic nerve protection was closely correlated with IOP history because damage was limited to less than 10% of the cross-sectional area in all animals in which the maximal IOP was less than or equal to 39 mm Hg, more than 2 SD below the mean value for eyes administered artificial tears. Topical glaucoma therapy in this model can prevent IOP elevation and protect optic nerve fibers.

  10. Heat Transfer and Pressure Drop Data for Circular Cylinders in Ducts and Various Arrangements

    DTIC Science & Technology

    1951-09-01

    cities - and Constant Spacing iii Scinch, Duct - ~-^ - - -r =• -~ - -- - - - - 37;, Single, Cylinder’ and Three- Cylinders in line" with Yard...heating coils surrounded by .a 3/Scinch thicis shell of ^anslte, .an asbest -cs-cemens material; oo’CiSlstljig of 35 per cent Portland cement .and lä per...gradients did, not permit very accurate de-* teraiinationä--&t low flois veio- cities because of ihseösitivity af She fee generalization of the, pressure

  11. Dynamics of diffusivity and pressure drop in flow-through and parallel-flow bioreactors during tissue regeneration.

    PubMed

    Podichetty, Jagdeep T; Dhane, Dhananjay V; Madihally, Sundararajan V

    2012-07-01

    In this study, transport characteristics in flow-through and parallel-flow bioreactors used in tissue engineering were simulated using computational fluid dynamics. To study nutrient distribution and consumption by smooth muscle cells colonizing the 100 mm diameter and 2-mm thick scaffold, effective diffusivity of glucose was experimentally determined using a two-chambered setup. Three different concentrations of chitosan-gelatin scaffolds were prepared by freezing at -80°C followed by lyophilization. Experiments were performed in both bioreactors to measure pressure drop at different flow rates. At low flow rates, experimental results were in agreement with the simulation results for both bioreactors. However, increase in flow rate beyond 5 mL/min in flow-through bioreactor showed channeling at the circumference resulting in lower pressure drop relative to simulation results. The Peclet number inside the scaffold indicated nutrient distribution within the flow-through bioreactor to be convection-dependent, whereas the parallel-flow bioreactor was diffusion-dependent. Three alternative design modifications to the parallel-flow were made by (i) introducing an additional inlet and an outlet, (ii) changing channel position, and (iii) changing the hold-up volume. Simulation studies were performed to assess the effect of scaffold thickness, cell densities, and permeability. These new designs improved nutrient distribution for 2 mm scaffolds; however, parallel-flow configuration was found to be unsuitable for scaffolds more than 4-mm thick, especially at low porosities as tissues regenerate. Furthermore, operable flow rate in flow-through bioreactors is constrained by the mechanical strength of the scaffold. In summary, this study showed limitations and differences between flow-through and parallel-flow bioreactors used in tissue engineering.

  12. A position-sensitive neutron spectrometer/dosimeter based on pressurized superheated drop (bubble) detectors

    NASA Astrophysics Data System (ADS)

    d'Errico, F.; Nath, R.; Holland, S. K.; Lamba, M.; Patz, S.; Rivard, M. J.

    2002-01-01

    A position-sensitive, superheated emulsion chamber (SEC) is introduced for three-dimensional (3D) spectrometry and dosimetry of fast neutrons. The detector is based on a fine suspension of octafluorocyclobutane droplets emulsified in a tissue-equivalent gel. This gel is highly viscous and immobilizes the bubbles at the location of their formation. At an operating temperature of 35°C, the droplets are moderately superheated and their evaporation is nucleated by the densely ionizing products of fast neutron interactions, with no response to sparsely ionizing radiations. Thus, when a neutron emitter such as a 252Cf brachytherapy source is inserted in the SEC, a bubble distribution forms around the source and makes the neutron field visible. The SEC is operated at different externally applied pressures that correspond to different response thresholds. These responses form a virtually orthogonal matrix which is suitable for spectrometry and allows the use of effective few channel unfolding procedures, yielding the spatial dependence of absorbed dose and neutron energy spectra in-tissue. Bubble spatial distributions in the chamber can be determined through optical tomography or magnetic resonance imaging (MRI). A 3D, steady-state MRI method has proven particularly effective for this purpose. After the imaging, the SEC can be pressurized above the halocarbon vapor tension in order to recondense the bubbles to the liquid phase. Within a few minutes, the device is annealed and ready to be used again for repeated measurements improving the bubble counting statistics.

  13. Condensation inside tubes: Computer program for pressure drop in straight tubes (horizontal and vertical with downflow)

    NASA Astrophysics Data System (ADS)

    1993-12-01

    ESDU 93014 introduces a Fortran program that implements the calculation procedures of ESDU 90024 and 91023 respectively for vertical and horizontal cases. Those documents should be consulted for details of the empirical correlation used. Since vapor density is an important variable in the calculation and is usually available as a function of saturation temperature, the relationship between pressure and saturation temperature is required at points along the tube, although a constant value of vapor density may be used if the user wishes. The program provides options to use an Antoine or Wagner equation, or to provide a set of values of saturation pressure and temperature; for the vapor density the options are to use the ideal gas law, to provide a set of values of saturation temperature and density or to use a specific correlation equation (log density as a fraction of critical as a five term polynomial function of reciprocal reduced temperature minus one). For a wide range of pure compounds the ESDU Physical Data, Chemical Engineering Sub-series provides values of the constants in the correlation equations for saturation temperature and vapor density. The program (ESDUpac A9314) is provided on disc (uncompiled) in the software volume, and also compiled within ESDUview, a user-friendly shell running under MS DOS that prompts on screen for the input data. A worked example illustrates the use of the program and the formats of the input data and the output.

  14. Heat transfer and pressure drop of new and eroded regenerative air preheater elements

    SciTech Connect

    Gruen, K.; Jawurek, H.H.; Sheer, T.J.; Lander, M.

    1999-07-01

    Conventional fossil fuels will still play an important role in meeting the world's energy demands in the 21st century. In order to have a reliable and sufficient source of energy, it is necessary to conserve resources, which means: conserve resources in terms of investments and life span, and conserve resources in terms of higher efficiencies (thermal and hydraulic). In the power generation industry, research must strive to reduce heat losses, reduce maintenance costs, increase the life expectancy of plant equipment and ensure compliance with current environmental regulations. In coal fired power stations, the regenerative air preheater plays an important role in the performance of the plant. Thermal performance characteristics, erosion, corrosion and blockage can be responsible for poor performance. In the present study the thermal and hydraulic performance of different heating plates as used in regenerative air preheaters is investigated. In both the uneroded and the eroded state, two different commonly used profile designs are tested. After presenting the results for new packs, results for packs which are eroded to different stages of mass loss, are presented.

  15. Heat transfer and pressure drop performance of a finned-tube heat exchanger proposed for use in the NASA Lewis Altitude Wind Tunnel

    NASA Technical Reports Server (NTRS)

    Vanfossen, G. J.

    1985-01-01

    A segment of the heat exchanger proposed for use in the NASA Lewis Altitude Wind Tunnel (AWT) facility has been tested under dry and icing conditions. The heat exchanger has the largest pressure drop of any component in the AWT loop. It is therefore critical that its performance be known at all conditions before the final design of the AWT is complete. The heat exchanger segment is tested in the NASA Lewis Icing Research Tunnel (IRT) in order to provide an icing cloud environment similar to what will be encountered in the AWT. Dry heat transfer and pressure drop data are obtained and compared to correlations available in the literature. The effects of icing sprays on heat transfer and pressure drop are also investigated.

  16. Steam-explosion pretreatment of wood: effect of chip size, acid, moisture content and pressure drop

    SciTech Connect

    Brownell, H.H.; Yu, E.K.C.; Saddler, J.N.

    1986-06-01

    Material balances for pentosan, lignin, and hexosan, during steam-explosion pretreatment of aspenwood, showed almost quantitative recovery of cellulose in the water-insoluble fraction. Dilute acid impregnation resulted in more selective hydrolysis of pentosan relative to undesirable pyrolysis, and gave a more accessible substrate for enzymatic hydrolysis. Thermocouple probes, located inside simulated aspenwood chips heated in 240 degrees C-saturated steam, showed rapid heating of air-dry wood, whereas green or impregnated wood heated slowly. Small chips, 3.2 mm in the fiber direction, whether green or air dry gave approximately equal rates of pentosan destruction and solubilization, and similar yields of glucose and of total reducing sugars on enzmatic hydrolysis with Trichoderma harzianum. Partial pyrolysis, destroying one-third of the pentosan of aspenwood at atmospheric pressure by dry steam at 276 degrees C, gave little increase in yield of reducing sugars on enzymatic hydrolysis. Treatment with saturated steam at 240 degrees C gave essentially the same yields of butanediol and ethanol on fermentation with Klebsiella pneumoniae, whether or not 80% of the steam was bled off before explosion and even if the chips remained intact, showing that explosion was unnecessary. 17 references.

  17. Effect of instant controlled pressure drop treatments on the oligosaccharides extractability and microstructure of Tephrosia purpurea seeds.

    PubMed

    Amor, Bouthaina Ben; Lamy, Cécile; Andre, Patrice; Allaf, Karim

    2008-12-12

    The study of the oligosaccharides extracted from Tephrosia purpurea seeds was undertaken using the instant controlled pressure drop (DIC) as a pre-treatment prior to conventional solvent extraction. This DIC procedure provided structural modification in terms of expansion, higher porosity and improvement of specific surface area; diffusion of solvent inside such seeds and availability of oligosaccharides increase notably. In this paper, we investigated and quantified the impact of the different DIC operative parameters on the yields of ciceritol and stachyose extracted from T. purpurea seeds. The treatment could be optimized with a steam pressure (P) (P=0.2 MPa), initial water content (W) (W=30% dry basis (DB)) and thermal treatment time (t) (t=30s). By applying DIC treatment in these conditions, the classic process of extraction was intensified in both aspects of yields (145% of ciceritol and 185% of stachyose), and kinetics (1h of extraction time instead of 4h for conventional process). The scanning electron microscopy micrographs provided evident modifications of structure of seeds due to the DIC treatment.

  18. Effect of filtration velocity and filtration pressure drop on the bag-cleaning performance of a pulse-jet baghouse

    SciTech Connect

    Tsai, C.J.; Tsai, M.L.; Lu, H.C.

    2000-01-01

    In this study the filtration velocity and filtration pressure drop at the beginning of bag cleaning were used as experimental parameters to evaluate the bag-cleaning performance of a pulse-jet baghouse. The effective residual pressure loss was used to indicate the cleaning performance after bag cleaning. Two different test dusts, fly ash and limestone, were used. The critical cleaning indices under different operation conditions for bag cleaning were also investigated. A critical average pulse overpressure was found to exist beyond which bag-cleaning performance did not improve much. It was found the filter's final filtration resistance is an important parameter to decide whether a Venturi is necessary for a good bag-cleaning performance or not. Use of a Venturi was found to increase the average pulse overpressure for a system with a filter's final resistance coefficient greater than about 500 Pa{center{underscore}dot}s/cm. However, no Venturi is recommended when the filter's final resistance coefficient is smaller than 500 Pa{center{underscore}dot}s/cm.

  19. Surface tension and its temperature coefficient of molten tin determined with the sessile drop method at different oxygen partial pressures.

    PubMed

    Yuan, Zhang Fu; Mukai, Kusuhiro; Takagi, Katsuhiko; Ohtaka, Masahiko; Huang, Wen Lai; Liu, Qiu Sheng

    2002-10-15

    The surface tension of molten tin has been determined by the sessile drop method at temperatures ranging from 523 to 1033 K and in the oxygen partial pressure (P(O(2))) range from 2.85 x 10(-19) to 8.56 x 10(-6) MPa, and its dependence on temperature and oxygen partial pressure has been analyzed. At P(O(2))=2.85 x 10(-19) and 1.06 x 10(-15) MPa, the surface tension decreases linearly with the increase of temperature and its temperature coefficients are -0.151 and -0.094 mN m(-1) K(-1), respectively. However, at high P(O(2)) (3.17 x 10(-10), 8.56 x 10(-6) MPa), the surface tension increases with the temperature near the melting point (505 K) and decreases above 723 K. The surface tension decrease with increasing P(O(2)) is much larger near the melting point than at temperatures above 823 K. The contact angle between the molten tin and the alumina substrate is 158-173 degrees, and the wettability is poor.

  20. Mixed convective low flow pressure drop in vertical rod assemblies: I---Predictive model and design correlation

    SciTech Connect

    Suh, K.Y.; Todreas, N.E.; Rohsenow, W.M. )

    1989-11-01

    A predicative theory has been developed for rod bundle frictional pressure drop characteristics under laminar and transitional mixed convection conditions on the basis of the intraassembly and intrasubchannel flow redistributions due to buoyancy for a wide spectrum of radial power profiles and for the geometric arrangements of practical design interest. Both the individual subchannel correlations and overall bundle design correlations have been formulated as multipliers applied to the isothermal friction factors at the same Reynolds numbers. Standard and modified subchannel friction factors have been obtained to be used with spatial-average and bulk-mean densities, respectively. A correlating procedure has been proposed to assess the effects of interacting subchannel flows, developing mixed convective flow, wire wrapping, power skew, rod number, and transition from laminar flow. In contrast to forced convection behavior, a strong rod number effect is present under mixed convection conditions in bundle geometries. The results of this study are of design importance in natural circulation conditions becasue the mixed convection frictional pressure losses exceed the corresponding isothermal values at the same Reynolds numbers.

  1. Boiling heat transfer and pressure drop of R-600a flowing in the mini-channels with fillisters

    NASA Astrophysics Data System (ADS)

    Wen, Mao-Yu; Jang, Kuang-Jang; Ho, Ching-Yen

    2015-01-01

    This study investigated the boiling heat transfer and pressure drop of hydrocarbon refrigerant (R-600a) flowing in six minichannels with fillisters made by electrical-discharge machining. The tests were run at a inlet pressure of 259-293 kPa and under saturated conditions, with the Reynolds number of 4,400-11,000 (i.e. mass flux of 195-487 kg/m2 s), heat flux of 1,790-8,950 W/m2 and outlet vapor quality of 0.041-0.25. Effects of the geometries of the fillisters, Reynolds number, heat flux and refrigerant quality on the heat transfer coefficient, friction factor and enhancement performance ratio were examined. The results of the minichannels with fillisters (Tests 1-4) compared to the minichannels without any fillister (Test 5) showed that the heat transfer coefficients increase about 1.05-1.34, 1.11-1.25, 1.23-1.59 and 1.07-1.21-fold, respectively. In addition, the friction factors for Tests 1, 2, 3 and 4 were about 3.3-9.4, 11.2-15.6, 14.7-21.9 and 5.0-6.3 % larger compared to that of the minichannels without any fillisters for Test 5. It was also found that Test 3 had the best enhancement of the performance. In summary, this study strongly suggests the use of fillisters constructed in minichannels.

  2. Orbiter thermal pressure drop characteristics for shuttle orbiter thermal protection system components: High density tile, low density tile, densified low density tile, and strain isolation pad

    NASA Technical Reports Server (NTRS)

    Lawing, P. L.; Nystrom, D. M.

    1980-01-01

    Pressure drop tests were conducted on available samples of low and high density tile, densified low density tile, and strain isolation pads. The results are presented in terms of pressure drop, material thickness and volume flow rate. Although the test apparatus was only capable of a small part of the range of conditions to be encountered in a Shuttle Orbiter flight, the data serve to determine the type of flow characteristics to be expected for each material type tested; the measured quantities also should serve as input for initial venting and flow through analysis.

  3. PRESSURE DROP OF FILTERING FACEPIECE RESPIRATORS: HOW LOW SHOULD WE GO?

    PubMed Central

    Kim, Jung-Hyun; Roberge, Raymond J.; Powell, Jeffrey B.; Shaffer, Ronald E.; Ylitalo, Caroline M.; Sebastian, John M.

    2015-01-01

    Objectives This study was undertaken to determine the mean peak filter resistance to airflow (Rfilter) encountered by subjects while wearing prototype filtering facepiece respirators (PRs) with low Rfilter during nasal and oral breathing at sedentary and low-moderate work rates. Material and Methods In-line pressure transducer measurements of mean Rfilter across PRs with nominal Rfilter of 29.4 Pa, 58.8 Pa and 88.2 Pa (measured at 85 l/min constant airflow) were obtained during nasal and oral breathing at sedentary and low-moderate work rates for 10 subjects. Results The mean Rfilter for the 29.4 PR was significantly lower than the other 2 PRs (p < 0.000), but there were no significant differences in mean Rfilter between the PRs with 58.8 and 88.2 Pa filter resistance (p > 0.05). The mean Rfilter was greater for oral versus nasal breathing and for exercise compared to sedentary activity (p < 0.001). Conclusions Mean oral and nasal Rfilter for all 3 PRs was at, or below, the minimal threshold level for detection of inspiratory resistance (the 58.8–74.5 Pa/1×s−1), which may account for the previously-reported lack of significant subjective or physiological differences when wearing PRs with these low Rfilter. Lowering filtering facepiece respirator Rfilter below 88.2 Pa (measured at 85 l/min constant airflow) may not result in additional subjective or physiological benefit to the wearer. PMID:26159949

  4. Optimal phenology of annual plants under grazing pressure.

    PubMed

    Yamamura, Norio; Fujita, Noboru; Hayashi, Motoyuki; Nakamura, Yusuke; Yamauchi, Atsushi

    2007-06-07

    Plants show phenological responses to herbivory. Some enclosure experiments have demonstrated that the onset of the peak flowering season is dependent on grazing pressure. We constructed a mathematical model using Pontryargin's maximum principle to investigate changes in flowering time by examining shifts in resource allocation from vegetative to reproductive plant components. We represented a primary production of a plant individual by two types of function of vegetative part size, a linear function and a convex non-linear function. The results of a linear production model indicate that optimal phenology follows a schedule that switches from the production of vegetative parts to that of reproductive parts at a given time ('bang-bang' control). However, in a non-linear model, a singular control, wherein the plant invests in both productive and reproductive parts, may be included between obligate production and reproduction periods. We assumed that the peak of the flowering season occurs immediately following the exclusive investment in reproduction. In a linear production model, differential herbivory rates on the vegetative and reproductive parts of a plant resulted in shifts in the peak flowering time. A higher herbivory rate on the vegetative components advanced the peak, whereas it was delayed when grazing pressure focused on reproductive components of the plant. In the non-linear production model, increased grazing pressure tended to postpone the flowering peak. These results corresponded well with results of enclosure experiments, thus suggesting adaptive control of flowering time in plants.

  5. Relationship between Arterial Stiffness and Blood Pressure Drop During the Sit-to-stand Test in Patients with Diabetes Mellitus

    PubMed Central

    Kobayashi, Yusuke; Kobayashi, Hideo; Sumida, Koichiro; Suzuki, Shota; Kagimoto, Minako; Okuyama, Yuki; Ehara, Yosuke; Katsumata, Mari; Fujita, Megumi; Fujiwara, Akira; Saka, Sanae; Yatsu, Keisuke; Hashimoto, Tatsuo; Kuji, Tadashi; Hirawa, Nobuhito; Toya, Yoshiyuki; Yasuda, Gen; Umemura, Satoshi

    2017-01-01

    Aim: Patients with orthostatic hypotension (OH) have high arterial stiffness. Patients with diabetes mellitus (DM) often have cardiac autonomic neuropathy that leads to OH; however, whether OH is an indicator of arterial stiffness progression is unclear. We aimed to investigate whether the cardioankle vascular index (CAVI) varies between DM patients with and without OH using the sit-to-stand test (STST). Methods: One hundred and fifty-nine patients with DM underwent CAVI assessment and blood pressure (BP) and heart rate change evaluation during the STST. OH was defined as a decline in systolic BP (SBP) and/or diastolic BP of at least 20 mmHg or 10 mmHg, respectively, in the initial and late upright positions compared with that in the sitting position. Results: OH was diagnosed in 42 patients (26.4%). DM patients with OH had significantly higher CAVI (9.36 ± 1.15 versus 8.89 ± 1.18, p = 0.026) than those without OH. CAVI was significantly inversely correlated with systolic and diastolic BP changes (R = −0.347, p <0.001 and R = −0.314, p <0.001, respectively) in the initial upright position. Multivariate regression analysis revealed that age, SBP changes, and low frequency component in the initial upright position were independent determinants of CAVI. Conclusion: Patients with DM having large BP drops occurring when moving from sitting to standing have high arterial stiffness. A significant BP drop during the STST necessitates careful evaluation of advanced arterial stiffness in patient with DM. PMID:27453255

  6. Headspace single drop microextraction coupled with microwave extraction of essential oil from plant materials.

    PubMed

    Zhai, Yujuan; Sun, Shuo; Wang, Ziming; Zhang, Yupu; Liu, He; Sun, Ye; Zhang, Hanqi; Yu, Aimin

    2011-05-01

    Headspace single drop microextraction (HS-SDME) coupled with microwave extraction (ME) was developed and applied to the extraction of the essential oil from dried Syzygium aromaticum (L.) Merr. et Perry and Cuminum cyminum L. The operational parameters, such as microdrop volume, microwave absorption medium (MAM), extraction time, and microwave power were optimized. Ten microliters of decane was used as the microextraction solvent. Ionic liquid and carbonyl iron powder were used as MAM. The extraction time was less than 7 min at the microwave power of 440 W. The proposed method was compared with hydrodistillation (HD). There were no obvious differences in the constituents of essential oils obtained by the two methods.

  7. Effect of explosion pressure on pipe collapse in chemical plants

    SciTech Connect

    Kurashiki, Tetsusei; Zako, Masaru

    1995-12-31

    Once a big earthquake attacks the chemical plant and tanks are broken, the disaster will extend due to the dangerous materials in tanks. In addition, the destructive explosion pressure leads to the collapse of pipes, structures and missiles from these broken pieces. Therefore, simulating the disasters in chemical plants is very important for the safety and the reliability evaluation. In this study, a computer program to analyze the behavior of pipe and chemical equipment under explosion pressure on a personal computer has been developed. The outline of the algorithm is as follows: (1) Three-dimensional pressure applied on pipes at the explosion is calculated. (2) The effect of interception of explosion pressure by oil dike is quantified. (3) Mechanical behavior of pipe is analyzed by FEM using beam element, and pipe collapse is evaluated from the result of FEM. (4) Cumulative damage caused by sequential explosion of tanks is calculated. As an example, the developed system was applied to practical plant model, and the damaged zone in the plant and the dangerous location of pipes after the explosion of a tank have been analyzed. As a result, it is revealed that the proposed computer program is very useful not only for safety and reliability evaluation but for the installation of pipes in chemical plants as well.

  8. Define and Quantify the Physics of Air Flow, Pressure Drop and Aerosol Collection in Nuclear Grade HEPA Filters

    SciTech Connect

    Moore, Murray E.

    2015-02-23

    Objective: Develop a set of peer-review and verified analytical methods to adjust HEPA filter performance to different flow rates, temperatures and altitudes. Experimental testing will measure HEPA filter flow rate, pressure drop and efficiency to verify the analytical approach. Nuclear facilities utilize HEPA (High Efficiency Particulate Air) filters to purify air flow for workspace ventilation. However, the ASME AG-1 technical standard (Code on Nuclear Air and Gas Treatment) does not adequately describe air flow measurement units for HEPA filter systems. Specifically, the AG-1 standard does not differentiate between volumetric air flow in ACFM (actual cubic feet per minute)compared to mass flow measured in SCFM (standard cubic feet per minute). More importantly, the AG-1 standard has an overall deficiency for using HEPA filter devices at different air flow rates, temperatures, and altitudes. Technical Approach: The collection efficiency and pressure drops of 18 different HEPA filters will be measured over a range of flow rates, temperatures and altitudes. The experimental results will be compared to analytical scoping calculations. Three manufacturers have allocated six HEPA filters each for this effort. The 18 filters will be tested at two different flow rates, two different temperatures and two different altitudes. The 36 total tests will be conducted at two different facilities: the ATI Test facilities (Baltimore MD) and the Los Alamos National Laboratory (Los Alamos NM). The Radiation Protection RP-SVS group at Los Alamos has an aerosol wind tunnel that was originally designed to evaluate small air samplers. In 2010, modifications were started to convert the wind tunnel for HEPA filter testing. (Extensive changes were necessary for the required aerosol generators, HEPA test fixtures, temperature control devices and measurement capabilities.) To this date, none of these modification activities have been funded through a specific DOE or NNSA program. This is

  9. Analysis of operational methane emissions from pressure relief valves from biogas storages of biogas plants.

    PubMed

    Reinelt, Torsten; Liebetrau, Jan; Nelles, Michael

    2016-10-01

    The study presents the development of a method for the long term monitoring of methane emissions from pressure relief valves (PRV(1)) of biogas storages, which has been verified during test series at two PRVs of two agricultural biogas plants located in Germany. The determined methane emission factors are 0.12gCH4kWhel(-1) (0.06% CH4-loss, within 106days, 161 triggering events, winter season) from biogas plant A and 6.80/7.44gCH4kWhel(-1) (3.60/3.88% CH4-loss, within 66days, 452 triggering events, summer season) from biogas plant B. Besides the operational state of the biogas plant (e.g. malfunction of the combined heat and power unit), the mode of operation of the biogas flare, which can be manually or automatically operated as well as the atmospheric conditions (e.g. drop of the atmospheric pressure) can also affect the biogas emission from PRVs. Copyright © 2016 Elsevier Ltd. All rights reserved.

  10. Strain response and re-equilibration of CH4-rich synthetic aqueous fluid inclusions in calcite during pressure drops

    NASA Astrophysics Data System (ADS)

    Bourdet, Julien; Pironon, Jacques

    2008-06-01

    Aqueous fluids in sedimentary basins often contain dissolved methane, particularly in petroleum environments. PVTX (Pressure-Volume-Temperature-Composition) reconstructions performed using fluid inclusion data are largely based on the assumption that inclusions do not change from the time of trapping until the present. Many authors, however, consider that fluid inclusions can re-equilibrate, particularly in fragile minerals like calcite. In order to understand this re-equilibration phenomenon in the metamorphic domain, previous experiments have been performed under high PT conditions, but few have been performed at low to medium PT conditions such as those associated with sedimentary burial diagenesis, and no previous studies have examined CH4-bearing aqueous inclusions in calcite. An experimental study of the preservation/modification of CH4-rich synthetic fluid inclusions in calcite during isothermal decompression was conducted. An autoclave was used for accurate PTX control allowing equilibrium between liquid and vapour in the CH4-H2O system. PTX conditions were maintained at four stages of decreasing pressure, with each stage held for 7 days to simulate an isothermal pressure drop. In order of decreasing pressure, the pressure-temperature conditions monitored were 276 ± 10 bar at 180 ± 7 °C, 176 ± 10 bar at 180 ± 7 °C, 76 ± 10 bar at 180 ± 7 °C and 10 ± 3 bar at 180 ± 15 °C. At the end of the experiment, the calcite was recovered and analyzed by microthermometry and Raman microspectroscopy for PTX reconstruction. A careful procedure was adopted to limit re-equilibration of inclusions during analytical procedures. Four types of inclusion shapes and four types of strain patterns were differentiated. Classification of the petrographic strain patterns was carried out. These strain patterns were associated with inclusion stretching and/or leakage regarding CH4, Th and Ph compared to experimental conditions. Factors controlling the preservation or

  11. The respective effect of under-rib convection and pressure drop of flow fields on the performance of PEM fuel cells

    NASA Astrophysics Data System (ADS)

    Wang, Chao; Zhang, Qinglei; Shen, Shuiyun; Yan, Xiaohui; Zhu, Fengjuan; Cheng, Xiaojing; Zhang, Junliang

    2017-03-01

    The flow field configuration plays an important role on the performance of proton exchange membrane fuel cells (PEMFCs). For instance, channel/rib width and total channel cross-sectional area determine the under-rib convection and pressure drop respectively, both of which directly influence the water removal, in turn affecting the oxygen supply and cathodic oxygen reduction reaction. In this study, effects of under-rib convection and pressure drop on cell performance are investigated experimentally and numerically by adjusting the channel/rib width and channel cross-sectional area of flow fields. The results show that the performance differences with various flow field configurations mainly derive from the oxygen transport resistance which is determined by the water accumulation degree, and the cell performance would benefit from the narrower channels and smaller cross sections. It reveals that at low current densities when water starts to accumulate in GDL at under-rib regions, the under-rib convection plays a more important role in water removal than pressure drop does; in contrast, at high current densities when water starts to accumulate in channels, the pressure drop dominates the water removal to facilitate the oxygen transport to the catalyst layer.

  12. The respective effect of under-rib convection and pressure drop of flow fields on the performance of PEM fuel cells.

    PubMed

    Wang, Chao; Zhang, Qinglei; Shen, Shuiyun; Yan, Xiaohui; Zhu, Fengjuan; Cheng, Xiaojing; Zhang, Junliang

    2017-03-02

    The flow field configuration plays an important role on the performance of proton exchange membrane fuel cells (PEMFCs). For instance, channel/rib width and total channel cross-sectional area determine the under-rib convection and pressure drop respectively, both of which directly influence the water removal, in turn affecting the oxygen supply and cathodic oxygen reduction reaction. In this study, effects of under-rib convection and pressure drop on cell performance are investigated experimentally and numerically by adjusting the channel/rib width and channel cross-sectional area of flow fields. The results show that the performance differences with various flow field configurations mainly derive from the oxygen transport resistance which is determined by the water accumulation degree, and the cell performance would benefit from the narrower channels and smaller cross sections. It reveals that at low current densities when water starts to accumulate in GDL at under-rib regions, the under-rib convection plays a more important role in water removal than pressure drop does; in contrast, at high current densities when water starts to accumulate in channels, the pressure drop dominates the water removal to facilitate the oxygen transport to the catalyst layer.

  13. The respective effect of under-rib convection and pressure drop of flow fields on the performance of PEM fuel cells

    PubMed Central

    Wang, Chao; Zhang, Qinglei; Shen, Shuiyun; Yan, Xiaohui; Zhu, Fengjuan; Cheng, Xiaojing; Zhang, Junliang

    2017-01-01

    The flow field configuration plays an important role on the performance of proton exchange membrane fuel cells (PEMFCs). For instance, channel/rib width and total channel cross-sectional area determine the under-rib convection and pressure drop respectively, both of which directly influence the water removal, in turn affecting the oxygen supply and cathodic oxygen reduction reaction. In this study, effects of under-rib convection and pressure drop on cell performance are investigated experimentally and numerically by adjusting the channel/rib width and channel cross-sectional area of flow fields. The results show that the performance differences with various flow field configurations mainly derive from the oxygen transport resistance which is determined by the water accumulation degree, and the cell performance would benefit from the narrower channels and smaller cross sections. It reveals that at low current densities when water starts to accumulate in GDL at under-rib regions, the under-rib convection plays a more important role in water removal than pressure drop does; in contrast, at high current densities when water starts to accumulate in channels, the pressure drop dominates the water removal to facilitate the oxygen transport to the catalyst layer. PMID:28251983

  14. Bidirectional Glenn shunt as an adjunct to surgical repair of congenital heart disease associated with pulmonary outflow obstruction: relevance of the fluid pressure drop-flow relationship.

    PubMed

    Ascuitto, Robert; Ross-Ascuitto, Nancy; Wiesman, Joshua; Deleon, Serafin

    2008-09-01

    A bidirectional Glenn shunt (BGS) was successfully incorporated into a two-ventricle repair for 10 patients (age, 3-17 years) who had congenital heart disease associated with severe pulmonary outflow obstruction. The BGS was used to volume-unload the pulmonary ventricle faced with residual outflow obstruction, thereby avoiding the need for insertion of a ventricle-to-pulmonary artery conduit. Transthoracic Doppler flow velocity analysis was used to determine transpulmonary peak systolic pressure drops as a measure of obstruction. Preoperative values ranged from 70 to 100 mmHg, and postoperative values ranged from less than 10 to 16 mmHg. At this writing, all patients are doing well 15 to 52 months after surgery. To gain further insight into the reduced pressure drop that may be achieved by decreasing flow rate across obstruction, a computer-based description of fluid flow was used to simulate blood traversing circumferentially narrowed passages. Overall pressure drops and associated flow energy losses were determined from numeric solutions (using finite-element analysis) to the Navier-Stokes equations for the proposed fluid reactions. Pressure drops and flow energy losses were found to decrease dramatically as flow rate was progressively reduced. For selected patients, a BGS can be an effective adjunct to the surgical treatment of pulmonary outflow obstruction. This approach avoids the use of a ventricle-to-pulmonary artery conduit, and thus the inevitable need in most patients for reoperations because of somatic growth, conduit failure, or both.

  15. Turbulent heat transfer and pressure drop characteristics of dilute water based Al2O3-Cu hybrid nanofluids.

    PubMed

    Suresh, S; Venkitaraj, K P; Hameed, M Shahul; Sarangan, J

    2014-03-01

    A study on fully developed turbulent convective heat transfer and pressure drop characteristics of Al2O3-Cu/water hybrid nanofluid flowing through a uniformly heated circular tube is presented in this paper. For this, Al2O3-Cu nanocomposite powder was synthesized in a thermo chemical route using hydrogen reduction technique and dispersed the hybrid nano powder in deionised water to form a stable hybrid nanofluid of 0.1% volume concentration. The prepared powder was characterized by X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM) to confirm the chemical composition, determine the particle size and study the surface morphology. Stability of the nanofluid was ensured by pH and zeta potential measurements. The average heat transfer enhancement for Al2O3-Cu/water hybrid nanofluid is 8.02% when compared to pure water. The experimental results also showed that 0.1% Al2O3-Cu/water hybrid nanofluids have slightly higher friction factor compared to 0.1% Al2O3/water nanofluid. The empirical correlations proposed for Nusselt number and friction factor were well agreed with the experimental data.

  16. An empirical investigation on thermal characteristics and pressure drop of Ag-oil nanofluid in concentric annular tube

    NASA Astrophysics Data System (ADS)

    Abbasian Arani, A. A.; Aberoumand, H.; Aberoumand, S.; Jafari Moghaddam, A.; Dastanian, M.

    2016-08-01

    In this work an experimental study on Silver-oil nanofluid was carried out in order to present the laminar convective heat transfer coefficient and friction factor in a concentric annulus with constant heat flux boundary condition. Silver-oil nanofluid prepared by Electrical Explosion of Wire technique with no nanoparticles agglomeration during nanofluid preparation process and experiments. The average sizes of particles were 20 nm. Nanofluids with various particle Volume fractions of 0.011, 0.044 and 0.171 vol% were employed. The nanofluid flowing between the tubes is heated by an electrical heating coil wrapped around it. The effects of different parameters such as flow Reynolds number, tube diameter ratio and nanofluid particle concentration on heat transfer coefficient are studied. Results show that, heat transfer coefficient increased by using nanofluid instead of pure oil. Maximum enhancement of heat transfer coefficient occurs in 0.171 vol%. In addition the results showed that, there are slight increases in pressure drop of nanofluid by increasing the nanoparticle concentration of nanofluid in compared to pure oil.

  17. Experimental investigation of heat transfer and pressure drop of turbulent flow inside tube with inserted helical coils

    NASA Astrophysics Data System (ADS)

    Sharafeldeen, M. A.; Berbish, N. S.; Moawed, M. A.; Ali, R. K.

    2016-08-01

    The heat transfer and pressure drop were experimentally investigated in a coiled wire inserted tube in turbulent flow regime in the range of Reynolds number of 14,400 ≤ Re ≤ 42,900. The present work aims to extend the experimental data available on wire coil inserts to cover wire diameter ratio of 0.044 ≤ e/d ≤ 0.133 and coil pitch ratio of 1 ≤ p/d ≤ 5. Uniform heat flux was applied to the external surface of the tube and air was selected as fluid. The effects of Reynolds number and wire diameter and coil pitch ratios on the Nusselt number and friction factor were studied. The enhancement efficiency and performance criteria ranges are of (46.9-82.6 %) and (100.1-128 %) within the investigated range of the different parameters, respectively. Correlations are obtained for the average Nusselt number and friction factor utilizing the present measurements within the investigated range of geometrical parameters and Re. The maximum deviation between correlated and experimental values for Nusselt number and friction factor are ±5 and ±6 %, respectively.

  18. The effect of twisted-tape width on heat transfer and pressure drop for fully developed laminar flow

    SciTech Connect

    Chakroun, W.M.; Al-Fahed, S.F.

    1996-07-01

    A series of experiments was conducted to study the effect of twisted-tape width on the heat transfer and pressure drop with laminar flow in tubes. Data for three twisted-tape wavelengths, each with five different widths, have been collected with constant wall temperature boundary condition. Correlations for the friction factor and Nusselt number are also available. The correlations predict the experimental data to within 10 to 15 percent for the heat transfer and friction factor, respectively. The presence of the twisted tape has caused the friction factor to increase by a factor of 3 to 7 depending on Reynolds number and the twisted-tape geometry. Heat transfer results have shown an increase of 1.5 to 3 times that of plain tubes depending on the flow conditions and the twisted-tape geometry. The width shows no effect on friction factor and heat transfer in the low range of Reynolds number but has a more pronounced effect on heat transfer at the higher range of Reynolds number. It is recommended to use loose-fit tapes for low Reynolds number flows instead of tight-fit in the design of heat exchangers because they are easier to install and remove for cleaning purposes.

  19. Designing Extraterrestrial Plant Growth Habitats With Low Pressure Atmospheres

    NASA Technical Reports Server (NTRS)

    Corey, Kenneth A.

    2001-01-01

    In-situ resource utilization, provision of human life support requirements by bioregenerative methods, and engineering constraints for construction and deployment of plant growth structures on the surface of Mars all suggest the need for plant growth studies at hypobaric pressures. Past work demonstrated that plants will likely tolerate and grow at pressures at or below 10 kPa. Based upon this premise, concepts are developed for the design of reduced pressure atmospheres in lightweight, inflatable structures for plant growth systems on Mars with the goals of maximizing design simplicity and the use of local resources. A modular pod design is proposed as it could be integrated with large-scale production systems. Atmospheric modification of pod clusters would be based upon a pulse and scrub system using mass flow methods for atmospheric transport. A specific modification and control scenario is developed for a lettuce pod to illustrate the dynamics of carbon dioxide and oxygen exchange within a pod. Considerations of minimal atmospheric crop requirements will aid in the development of engineering designs and strategies for extraterrestrial plant growth structures that employ rarefied atmospheres.

  20. Designing Extraterrestrial Plant Growth Habitats with Low Pressure Atmospheres

    NASA Technical Reports Server (NTRS)

    Corey, Kenneth A.

    2002-01-01

    In-situ resource utilization, provision of human life support requirements by bioregenerative methods, and engineering constraints for construction and deployment of plant growth structures on the surface of Mars all suggest the need for plant growth studies at hypobaric pressures. Past work demonstrated that plants will likely tolerate and grow at pressures at or below 10 kPa. Based upon this premise, concepts are developed for the design of reduced pressure atmospheres in lightweight, inflatable structures for plant growth systems on Mars with the goals of maximizing design simplicity and the use of local resources. A modular pod design is proposed as it could be integrated with large-scale production systems. Atmospheric modification of pod clusters would be based upon a pulse and scrub system using mass flow methods for atmospheric transport. A specific modification and control scenario is developed for a lettuce pod to illustrate the dynamics of carbon dioxide and oxygen exchange within a pod. Considerations of minimal atmospheric crop requirements will aid in the development of engineering designs and strategies for extraterrestrial plant growth structures that employ rarefied atmospheres.

  1. Designing Extraterrestrial Plant Growth Habitats With Low Pressure Atmospheres

    NASA Technical Reports Server (NTRS)

    Corey, Kenneth A.

    2001-01-01

    In-situ resource utilization, provision of human life support requirements by bioregenerative methods, and engineering constraints for construction and deployment of plant growth structures on the surface of Mars all suggest the need for plant growth studies at hypobaric pressures. Past work demonstrated that plants will likely tolerate and grow at pressures at or below 10 kPa. Based upon this premise, concepts are developed for the design of reduced pressure atmospheres in lightweight, inflatable structures for plant growth systems on Mars with the goals of maximizing design simplicity and the use of local resources. A modular pod design is proposed as it could be integrated with large-scale production systems. Atmospheric modification of pod clusters would be based upon a pulse and scrub system using mass flow methods for atmospheric transport. A specific modification and control scenario is developed for a lettuce pod to illustrate the dynamics of carbon dioxide and oxygen exchange within a pod. Considerations of minimal atmospheric crop requirements will aid in the development of engineering designs and strategies for extraterrestrial plant growth structures that employ rarefied atmospheres.

  2. Designing Extraterrestrial Plant Growth Habitats with Low Pressure Atmospheres

    NASA Technical Reports Server (NTRS)

    Corey, Kenneth A.

    2002-01-01

    In-situ resource utilization, provision of human life support requirements by bioregenerative methods, and engineering constraints for construction and deployment of plant growth structures on the surface of Mars all suggest the need for plant growth studies at hypobaric pressures. Past work demonstrated that plants will likely tolerate and grow at pressures at or below 10 kPa. Based upon this premise, concepts are developed for the design of reduced pressure atmospheres in lightweight, inflatable structures for plant growth systems on Mars with the goals of maximizing design simplicity and the use of local resources. A modular pod design is proposed as it could be integrated with large-scale production systems. Atmospheric modification of pod clusters would be based upon a pulse and scrub system using mass flow methods for atmospheric transport. A specific modification and control scenario is developed for a lettuce pod to illustrate the dynamics of carbon dioxide and oxygen exchange within a pod. Considerations of minimal atmospheric crop requirements will aid in the development of engineering designs and strategies for extraterrestrial plant growth structures that employ rarefied atmospheres.

  3. Injury to plants from rapidly dropping temperature in Washington and northern Idaho

    Treesearch

    R. Daubenmire

    1957-01-01

    In nearly 70 years of recorded weather history, Washington and northern Idaho have on three occasions experienced exceptionally sharp freezes in late autumn or early winter that caused considerable damage to plants. A brief review of these events is warranted since the records are consistent enough to permit the drawing of significant conclusions.

  4. Experimental study of single-phase pressure drop and heat transfer in a micro-fin tube

    SciTech Connect

    Li, Xiao-Wei; Meng, Ji-An; Li, Zhi-Xin

    2007-11-15

    The single-phase pressure drop and heat transfer in a micro-fin tube were measured using oil and water as the working fluids. The Prandtl number varied from 3.2 to 220 and the Reynolds number ranged from 2500 to 90,000. The results show that there is a critical Reynolds number, Re{sub cr}, for heat transfer enhancement. For Re

  5. Instant controlled pressure drop technology and ultrasound assisted extraction for sequential extraction of essential oil and antioxidants.

    PubMed

    Allaf, Tamara; Tomao, Valérie; Ruiz, Karine; Chemat, Farid

    2013-01-01

    The instant controlled pressure drop (DIC) technology enabled both the extraction of essential oil and the expansion of the matrix itself which improved solvent extraction. The sequential use of DIC and Ultrasound Assisted Extraction (UAE) triggered complementary actions materialized by supplementary effects. We visualized these combination impacts by comparing them to standard techniques: Hydrodistillation (HD) and Solvent Extraction (SE). First, the extraction of orange peel Essential Oils (EO) was achieved by HD during 4h and DIC process (after optimization) during 2 min; EO yields was 1.97 mg/g dry material (dm) with HD compared to 16.57 mg/g d m with DIC. Second, the solid residue was recovered to extract antioxidant compounds (naringin and hesperidin) by SE and UAE. Scanning electron microscope showed that after HD the recovered solid shriveled as opposite to DIC treatment which expanded the product structure. HPLC analyses showed that the best kinetics and yields of naringin and hesperidin extraction was when DIC and UAE are combined. Indeed, after 1h of extraction, DIC treated orange peels with UAE were 0.825 ± 1.6 × 10(-2)g/g of dry material (dm) for hesperidin and 6.45 × 10(-2) ± 2.3 × 10(-4)g/g d m for naringin compared to 0.64 ± 2.7 × 10(-2)g/g of dry material (dm) and 5.7 × 10(-2) ± 1.6 × 10(-3)g/g d m, respectively with SE. By combining DIC to UAE, it was possible to enhance kinetics and yields of antioxidant extraction.

  6. Heat transfer and pressure drop correlations of microchannel heat exchangers with S-shaped and zigzag fins for carbon dioxide cycles

    SciTech Connect

    Ngo, Tri Lam; Kato, Yasuyoshi; Nikitin, Konstantin; Ishizuka, Takao

    2007-11-15

    A new microchannel heat exchanger (MCHE) with S-shaped fins was developed using the three-dimensional computational fluid dynamics (3D CFD) FLUENT code. The MCHE provided 6-7 times lower pressure drop while maintaining heat-transfer performance that was almost equivalent to that of a conventional MCHE with zigzag fins. This study was done to confirm the simulation results of thermal-hydraulic performance using a supercritical carbon dioxide loop, and to propose empirical correlations of Nusselt numbers and pressure-drop factors for a new MCHE with S-shaped fins and a conventional one with zigzag fins. This study is also intended to confirm the independence of Pr obtained in the previous study by widely varying Pr from 0.75 to 2.2. Experimental results show that the pressure-drop factor of the MCHEs with S-shaped fins is 4-5 times less than that of MCHE with zigzag fins, although Nu is 24-34% less, depending on the Re within its range. The Nusselt number correlations are expressed, respectively as Nu{sub S-shaped} {sub fins} = 0.1740 Re{sup 0.593}Pr{sup 0.430} and Nu{sub zigzag} {sub fins} = 0.1696 Re{sup 0.629}Pr{sup 0.317} for the MCHE with S-shaped and zigzag fins, and their pressure-drop factors are given as f{sub S-shaped} {sub fins} = 0.4545 Re{sup -0.340} and f{sub zigzag} {sub fins} = 0.1924 Re{sup -0.091}. The Nu correlation of the MCHE with S-shaped fins reproduces the experimental data of overall heat transfer coefficients with a standard deviation (1 sigma) of {+-}2.3%, although it is {+-}3.0% for the MCHE with zigzag fins. The calculated pressure drops obtained from pressure-drop factor correlations agree with the experimental data within a standard deviation of {+-}16.6% and {+-}13.5% for the MCHEs with S-shaped and zigzag fins, respectively. (author)

  7. Measurement and modelling of forced convective heat transfer coefficient and pressure drop of Al2O3- and SiO2-water nanofluids

    NASA Astrophysics Data System (ADS)

    Julia, J. E.; Hernández, L.; Martínez-Cuenca, R.; Hibiki, T.; Mondragón, R.; Segarra, C.; Jarque, J. C.

    2012-11-01

    Forced convective heat transfer coefficient and pressure drop of SiO2- and Al2O3-water nanofluids were characterized. The experimental facility was composed of thermal-hydraulic loop with a tank with an immersed heater, a centrifugal pump, a bypass with a globe valve, an electromagnetic flow-meter, a 18 kW in-line pre-heater, a test section with band heaters, a differential pressure transducer and a heat exchanger. The test section consists of a 1000 mm long aluminium pipe with an inner diameter of 31.2 mm. Eighteen band heaters were placed all along the test section in order to provide a uniform heat flux. Heat transfer coefficient was calculated measuring fluid temperature using immersed thermocouples (Pt100) placed at both ends of the test section and surface thermocouples in 10 axial locations along the test section (Pt1000). The measurements have been performed for different nanoparticles (Al2O3 and SiO2 with primary size of 11 nm and 12 nm, respectively), volume concentrations (1% v., 5% v.), and flow rates (3 103Re<105). Maximum heat transfer coefficient enhancement (300%) and pressure drop penalty (1000%) is obtained with 5% v. SiO2 nanofluid. Existing correlations can predict, at least in a first approximation, the heat transfer coefficient and pressure drop of nanofluids if thermal conductivity, viscosity and specific heat were properly modelled.

  8. Sliding mode control application in ABWR plant pressure regulation

    SciTech Connect

    Huang, Zhengyu; Edwards, Robert M.

    2002-07-01

    A sliding mode controller is designed for an ABWR nuclear power plant turbine throttle pressure regulation. To avoid chattering problem, which is common to conventional sliding mode controllers, and estimation of uncertainties and disturbances, the recursive-form sliding mode control algorithm is developed. To apply the sliding mode control technique, the original plant's 11.-order dynamics model is first transformed to a canonical form differential equation of a relative order of 2 for turbine throttle pressure's dynamics. Simulation results show that the design objectives are achieved and the resulting controller is superior to the existing PI controller in many aspects, including settling time, overshoot/undershoot in response to setpoint step input and fluctuation amplitude in the presence of external disturbances. (authors)

  9. Characterisation of heat transfer and pressure drop in condensation processes within mini-channel tubes with last generation of refrigerant fluids

    NASA Astrophysics Data System (ADS)

    Lopez Belchi, D. Alejandro

    Heat exchanger developments are driven by energetic efficiency increase and emissionreduction. To reach the standards new system are required based on mini-channels. Mini-channels can be described as tubes with one or more ports extruded in aluminiumwith hydraulic diameter are in the range of 0.2 to 3 mm. Its use in refrigeration systemsfor some years ago is a reality thanks to the human ability to made micro-scale systems.Some heat exchanger enterprises have some models developed specially for their use inautomotive sector, cooling sector, and industrial refrigeration without having a deepknowledge of how these reduced geometries affect the most important parameters suchas pressure drop and the heat transfer coefficient. To respond to this objective, an exhaustive literature review of the last two decades hasbeen performed to determinate the state of the research. Between all the publications,several models have been selected to check the predicting capacities of them becausemost of them were developed for single port mini-channel tubes. Experimentalmeasurements of heat transfer coefficient and frictional pressure drop were recorded inan experimental installation built on purpose at the Technical University of Cartagena.Multiple variables are recorded in this installation in order to calculate local heattransfer coefficient in two-phase condensing flow within mini-channels. Both pressure drop and heat transfer coefficient experimental measurements arecompared to the previously mentioned models. Most of them capture the trend correctlybut others fail predicting experimental data. These differences can be explained by theexperimental parameters considered during the models development. In some cases themodels found in the literature were developed specific conditions, consequently theirpredicting capacities are restricted. As main contributions, this thesis provides new modelling tools for mini-channelscondensing pressure drop and heat transfer coefficient

  10. The effect of passive mixing on pressure drop and oxygen mass fraction using opposing channel flow field design in a Proton Exchange Membrane Fuel Cell

    NASA Astrophysics Data System (ADS)

    Singh, Anant Bir

    This study investigates a flow field with opposing channel design. Previous studies on flow field designs have been focused on improving fuel utilization which often leads to increased pressure drop. This increased pressure drop is typical because standard designs employ either a single flow channel to clear blockages or dead end condition to force the flow through the gas diffusion layer. The disadvantage with these designs is the increased resistance to the flow which requires higher pressure, which becomes a parasitic loss that lowers the system efficiency. For this study the focus was to reduce the pressure drop by providing a less resistive path to the flow. To achieve a less resistive path, the inlet channel was split into two opposing channels. These channels are then recombined only to be split again for the next leg. Therefore, the split channel design should reduce the pressure drop which reduces the parasitic load and ultimately contributes to higher system efficiency. In addition the recombining of the streams at each leg should induce mixing. Having opposing channels should also increase cross flow under the lands to reduce mass transfer loses. The cathode side of the fuel cell is especially sensitive to the mass transport losses since air (oxygen mixed with nitrogen) is used for supplying oxygen unlike the anode side which uses pure hydrogen. To test the hypothesis of having benefits from an opposing channel design, both an experimental and analytical approach was taken. For the experiment, a serpentine flow field and opposing channel flow field plates were compared over several flow rates with compressed air. To test the hypothesis of increased mass transfer, the two flow fields were modeled using a CFD software package, COMSOL. It was found that the opposing channel configuration for high flow rate with multiple entry and exit conditions exhibited significant improvement over the single serpentine channel. Pressure drop was ⅓ less than the

  11. A critical review of forced convection heat transfer and pressure drop of Al2O3, TiO2 and CuO nanofluids

    NASA Astrophysics Data System (ADS)

    Khurana, Deepak; Choudhary, Rajesh; Subudhi, Sudhakar

    2017-01-01

    Nanofluid is the colloidal suspension of nanosized solid particles like metals or metal oxides in some conventional fluids like water and ethylene glycol. Due to its unique characteristics of enhanced heat transfer compared to conventional fluid, it has attracted the attention of research community. The forced convection heat transfer of nanofluid is investigated by numerous researchers. This paper critically reviews the papers published on experimental studies of forced convection heat transfer and pressure drop of Al2O3, TiO2 and CuO based nanofluids dispersed in water, ethylene glycol and water-ethylene glycol mixture. Most of the researchers have shown a little rise in pressure drop with the use of nanofluids in plain tube. Literature has reported that the pumping power is appreciably high, only at very high particle concentration i.e. more than 5 %. As nanofluids are able to enhance the heat transfer at low particle concentrations so most of the researchers have used less than 3 % volume concentration in their studies. Almost no disagreement is observed on pressure drop results of different researchers. But there is not a common agreement in magnitude and mechanism of heat transfer enhancement. Few studies have shown an anomalous enhancement in heat transfer even at low particle concentration. On the contrary, some researchers have shown little heat transfer enhancement at the same particle concentration. A large variation (2-3 times) in Nusselt number was observed for few studies under similar conditions.

  12. A comparison of the heat transfer and pressure drop performance of R-134a-lubricant mixtures in different diameter smooth tubes and micro-fin tubes

    SciTech Connect

    Eckels, S.J.; Doerr, T.M.; Pate, M.B.

    1998-10-01

    The average heat transfer coefficients and pressure drops during evaporation and condensation are reported for mixtures of R-134a and an ester lubricant in tubes of 12.7 mm (1/2 in.) outer diameter. The objective of this paper is to evaluate the performance of the R-134a-lubricant mixtures in these tubes and determine the performance benefits of the micro-fin tube. The performance benefits of the tubes with 12.7 mm (1/2 in.) outer diameter are compared to those of smaller tubes with 9.52 mm (3/8 in.) outer diameter. The lubricant used was a 169 SUS penta erythritol ester mixed-acid lubricant. The lubricant concentration was varied from 0--5.1% in the mixture. The average heat transfer coefficients in the 12.7 mm (1/2 in.) micro-fin tube were 50--150% higher than those for the 12.7 mm (1/2 in.) smooth tube, while pressure drops in the micro-fin tube were 5% to 50% higher than in the smooth tube. The addition of lubricant degraded the average heat transfer coefficients in all cases except during evaporation at low lubricant concentrations. Pressure drops were always increased with the addition of lubricant. The experimental results also indicate that tube diameter has some effect on the performance benefits of the micro-fin tube over that of the smooth tube.

  13. Heat transfer and pressure drop characteristics of a plate heat exchanger using a propylene-glycol/water mixture as the working fluid

    SciTech Connect

    Talik, A.C.; Fletcher, L.S.; Anand, N.K.; Swanson, L.W.

    1995-12-31

    Plate heat exchangers are becoming increasingly important because of their potential applications in industrial processes, especially in terms of their thermal performance and their limited pressure drop. An experimental investigation to acquire both heat-transfer and pressure-drop data for a plate heat exchanger was conducted in order to respond to these interests. A propylene-glycol/water mixture was used as the working fluid in order to provide lower Reynolds numbers than those provided by water at similar test conditions. The plate heat exchanger was composed of 31 plates, each with a chevron angle of 30 degrees. The isothermal pressure drop data were taken in the fully laminar flow regime for Reynolds numbers from 10 to 80. The heat transfer data were taken in the fully laminar flow regime for Reynolds numbers of 80 to 720 with heat transfer rates of 1.1 {times} 10{sup 5} to 6.5 {times} 10{sup 5} W. The experimental data for the friction factor and Nusselt number were correlated using a standard power-law function. Other published heat-transfer and friction factor correlations for plate heat exchangers with similar plates at selected conditions are compared to the data.

  14. Effect of airstream velocity on mean drop diameters of water sprays produced by pressure and air atomizing nozzles. [for combustion studies

    NASA Technical Reports Server (NTRS)

    Ingebo, R. D.

    1977-01-01

    A scanning radiometer was used to determine the effect of airstream velocity on the mean drop diameter of water sprays produced by pressure atomizing and air atomizing fuel nozzles used in previous combustion studies. Increasing airstream velocity from 23 to 53.4 meters per second reduced the Sauter mean diameter by approximately 50 percent with both types of fuel nozzles. The use of a sonic cup attached to the tip of an air assist nozzle reduced the Sauter mean diameter by approximately 40 percent. Test conditions included airstream velocities of 23 to 53.4 meters per second at 293 K and atmospheric pressure.

  15. Demonstration plant for pressurized gasification of biomass feedstocks

    SciTech Connect

    Trenka, A.R. ); Kinoshita, C.M.; Takahashi, P.K.; Phillips, V.D. ); Caldwell, C. Co., Pasadena, CA ); Kwok, R. ); Onischak, M.; Babu, S.P. (Institute of Gas Technology

    1991-01-01

    A project to design, construct, and operate a pressurized biomass gasification plant in Hawaii will begin in 1991. Negotiations are underway with the United States Department of Energy (DOE) which is co-funding the project with the state of Hawaii and industry. The gasifier is a scale-up of the pressurized fluidized-bed RENUGAS process developed by the Institute of Gas Technology (IGT). The project team consists of Pacific International Center for High Technology Research (PICHTR), Hawaii Natural Energy Institute (HNEI) of the University of Hawaii, Hawaiian Commercial and Sugar Company (HC S), The Ralph M. Parsons Company, and IGT. The gasifier will be designed for 70 tons per day of sugarcane fiber (bagasse) and will be located at the Paia factory of HC S on the island of Maui. In addition to bagasse, other feedstocks such as wood, biomass wastes, and refuse-derived-fuel may be evaluated. The demonstration plant will ultimately supply part of the process energy needs for the sugar factory. The operation and testing phase will provide process information for both air- and oxygen-blown gasification, and at both low and high pressures. The process will be evaluated for both fuel gas and synthesis gas production, and for electrical power production with advanced power generation schemes. 6 refs., 3 figs., 1 tab.

  16. Determination of molybdenum in plants by vortex-assisted emulsification solidified floating organic drop microextraction and flame atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Oviedo, Jenny A.; Fialho, Lucimar L.; Nóbrega, Joaquim A.

    2013-08-01

    A fast and sensitive procedure for extraction and preconcentration of molybdenum in plant samples based on solidified floating organic drop microextraction combined with flame atomic absorption spectrometry and discrete nebulization was developed. 8-Hydroxyquinoline (8-HQ) was used as complexing agent. The experimental conditions established were: 0.5% m v- 1 of 8-HQ, 60 μL of 1-undecanol as the extractant phase, 2 min vortex extraction time, centrifugation for 2 min at 2000 rpm, 10 min into an ice bath and discrete nebulization by introducing 200 μL of solution. The calibration curve was linear from 0.02 to 4.0 mg L- 1 with a limit of detection of 4.9 μg L- 1 and an enhancement factor of 67. The relative standard deviations for ten replicate measurements of 0.05 and 1.0 mg L- 1 Mo were 6.0 and 14.5%, respectively. The developed procedure was applied for determining molybdenum in corn samples and accuracy was proved using certified reference materials.

  17. Fiber optic pressure sensors for nuclear power plants

    SciTech Connect

    Hashemian, H.M.; Black, C.L.

    1995-04-01

    In the last few years, the nuclear industry has experienced some problems with the performance of pressure transmitters and has been interested in new sensors based on new technologies. Fiber optic pressure sensors offer the potential to improve on or overcome some of the limitations of existing pressure sensors. Up to now, research has been motivated towards development and refinement of fiber optic sensing technology. In most applications, reliability studies and failure mode analyses remain to be exhaustively conducted. Fiber optic sensors have currently penetrated certain cutting edge markets where they possess necessary inherent advantages over other existing technologies. In these markets (e.g. biomedical, aerospace, automotive, and petrochemical), fiber optic sensors are able to perform measurements for which no alternate sensor previously existed. Fiber optic sensing technology has not yet been fully adopted into the mainstream sensing market. This may be due to not only the current premium price of fiber optic sensors, but also the lack of characterization of their possible performance disadvantages. In other words, in conservative industries, the known disadvantages of conventional sensors are sometimes preferable to unknown or not fully characterized (but potentially fewer and less critical) disadvantages of fiber optic sensors. A six-month feasibility study has been initiated under the auspices of the US Nuclear Regulatory Commission (NRC) to assess the performance and reliability of existing fiber optic pressure sensors for use in nuclear power plants. This assessment will include establishment of the state of the art in fiber optic pressure sensing, characterization of the reliability of fiber optic pressure sensors, and determination of the strengths and limitations of these sensors for nuclear safety-related services.

  18. Ultra high pressure liquid chromatography for crude plant extract profiling.

    PubMed

    Eugster, Philippe J; Guillarme, Davy; Rudaz, Serge; Veuthey, Jean-Luc; Carrupt, Pierre-Alain; Wolfender, Jean-Luc

    2011-01-01

    Ultra high pressure liquid chromatography (UHPLC) systems operating at very high pressures and using sub-2 microm packing columns have allowed a remarkable decrease in analysis time and increase in peak capacity, sensitivity, and reproducibility compared to conventional HPLC. This technology has rapidly been widely accepted by the analytical community and is being gradually applied to various fields of plant analysis such as QC, profiling and fingerprinting, dereplication, and metabolomics. For many applications, an important improvement of the overall performances has been reported. In this review, the basic principles of UHPLC are summarized, and practical information on the type of columns used and phase chemistry available is provided. An overview of the latest applications to natural product analysis in complex mixtures is given, and the potential and limitations as well as some new trends in the development of UHPLC are discussed.

  19. Influence of Atmospheric Pressure Torch Plasma Irradiation on Plant Growth

    NASA Astrophysics Data System (ADS)

    Akiyoshi, Yusuke; Hayashi, Nobuya; Kitazaki, Satoshi; Koga, Kazunori; Shiratani, Masaharu

    2011-10-01

    Growth stimulation characteristics of plants seeds are investigated by an atmospheric discharge irradiation into plasma seeds. Atmospheric pressure plasma torch is consisted of alumina ceramics tube and the steel mesh electrodes wind inside and outside of the tube. When AC high voltage (8 kHz) is applied to the electrode gap, the barrier discharge plasma is produced inside the alumina ceramics tube. The barrier discharge plasma is blown outside with the gas flow in ceramics tube. Radish sprouts seeds locate at 1 cm from the torch edge. The growth stimulation was observed in the length of a stem and a root after the plasma irradiation. The stem length increases approximately 2.8 times at the cultivation time of 24 h. And the growth stimulation effect is found to be maintained for 40 h, after sowing seeds. The mechanism of the growth stimulation would be the redox reaction inside plant cells induced by oxygen radicals.

  20. Pressure, temperature and density drops along supercritical fluid chromatography columns. II. Theoretical simulation for neat carbon dioxide and columns packed with 3-μm particles.

    PubMed

    Kaczmarski, Krzysztof; Poe, Donald P; Tarafder, Abhijit; Guiochon, Georges

    2012-08-10

    When chromatography is carried out with high-density carbon dioxide as the mobile phase, the required pressure gradient along the column is moderate but this mobile phase is highly compressible so, under certain experimental conditions, its density may decrease significantly along the column. Such an expansion absorbs heat and causes cooling of the column. The resulting heat transfer causes the formation of axial and radial gradients of temperature and density that may become large under certain conditions. In the first part of this series the pressure, temperature, and density drops were measured over a wide range of experimental temperature and pressure conditions, along columns packed with 3- and 5-μm particles. These columns were suspended in a circulating air bath and were either bare or covered with foam insulation. The behavior of these columns was discussed with special attention to their thermal heterogeneity. In this part we scrutinize the application of two heat transfer models to predict the pressure, temperature and density drops. One is a two-dimensional model that takes into account the axial and radial variations of the relevant chromatographic parameters along the column. The other, one-dimensional model ignores the radial variations of these parameters. The numerical solutions of the two-dimensional model are in excellent agreement with independent experimental data. The one-dimensional model can also be applied for the analysis of the behavior of supercritical fluid chromatography (SFC) columns away from the critical conditions. Copyright © 2012 Elsevier B.V. All rights reserved.

  1. Electric utility second-generation pressurized fluidized bed combustion plants

    SciTech Connect

    Robertson, A. ); Bonk, D. )

    1992-01-01

    In the search for a more efficient, less costly, and more environmentally responsible method for generating electrical power from coal, research and development has turned to advanced pressurized fluidized bed combustion (PFBC) and coal gasification technologies. A logical extension of this work is the second-generation PFBC plant, which incorporates key components of each of these technologies. In this new type of plant, coal is devolatilized/carbonized before it is injected into the PFB combustor bed, and the low-Btu fuel gas produced by this process is burned in a gas turbine topping combustor. By integrating coal carbonization with PFB coal/char combustion, gas turbine inlet temperatures higher than 1149{degrees}C (2100{degrees}F) can be achieved. The carbonizer, PFB combustor, and particulate-capturing hot gas cleanup systems operate at 871{degrees}C (1600{degrees}F), permitting sulfur capture by lime-based sorbents and minimizing the release of coal contaminants to the gases. This paper presents the performance and economics of this new type of plant and provides a brief overview of the pilot plant test programs being conducted to support its development.

  2. An analysis of experimental data and prediction methods for two-phase frictional pressure drop and flow boiling heat transfer in micro-scale channels

    SciTech Connect

    Ribatski, Gherhardt; Wojtan, Leszek; Thome, John R.

    2006-10-15

    Experimental results for two-phase frictional pressure drop and flow boiling heat transfer in micro-scale channels were obtained from the literature. The extensive pressure drop database comprises both diabatic and adiabatic results covering eight fluids, mass velocities from 23 to 6000kg/m{sup 2}s and vapor qualities up to 1. These data were carefully analyzed and compared against 12 two-phase frictional pressure drop prediction methods, including both macro- and micro-scale methods. Overall, the methods by Muller-Steinhagen and Heck and by Mishima and Hibiki, as well as the homogenous model, using the two-phase viscosity definition proposed by Cicchitti and coworkers, provide the most accurate predictions. However, they worked poorly at vapor qualities higher than 0.5 where annular, partial dryout and mist flow patterns would be expected. Similarly, a large database for micro-scale flow boiling heat transfer for eleven fluids covering mass velocities from 100 to 800kg/m{sup 2}s, reduced pressures from 0.03 to 0.77 and heat fluxes from 5 to 180kW/m{sup 2} were compared against three recently proposed micro-scale and one well-known macro-scale heat transfer prediction method. Although some heat transfer trends were captured by the methods, in general they poorly predicted the database. This is not surprising since an analysis of the trends of the experimental results revealed large discrepancies between different data sets, even at similar experimental conditions, and no present method could capture such contrasting trends. The study concludes that the 3-zone model proposed by Thome and coworkers based on the transient conduction through an evaporating liquid film seems to be the most promising approach to predict heat transfer coefficients in micro-scale channels but is still not sufficiently developed to use as a general design tool. (author)

  3. Flow pattern, pressure drop and void fraction of two-phase gas-liquid flow in an inclined narrow annular channel

    SciTech Connect

    Wongwises, Somchai; Pipathattakul, Manop

    2006-03-01

    Two-phase flow pattern, pressure drop and void fraction in horizontal and inclined upward air-water two-phase flow in a mini-gap annular channel are experimentally studied. A concentric annular test section at the length of 880mm with an outer diameter of 12.5mm and inner diameter of 8mm is used in the experiments. The flow phenomena, which are plug flow, slug flow, annular flow, annular/slug flow, bubbly/plug flow, bubbly/slug-plug flow, churn flow, dispersed bubbly flow and slug/bubbly flow, are observed and recorded by high-speed camera. A slug flow pattern is found only in the horizontal channel while slug/bubbly flow patterns are observed only in inclined channels. When the inclination angle is increased, the onset of transition from the plug flow region to the slug flow region (for the horizontal channel) and from the plug flow region to slug/bubbly flow region (for inclined channels) shift to a lower value of superficial air velocity. Small shifts are found for the transition line between the dispersed bubbly flow and the bubbly/plug flow, the bubbly/plug flow and the bubbly/slug-plug flow, and the bubbly/plug flow and the plug flow. The rest of the transition lines shift to a higher value of superficial air velocity. Considering the effect of flow pattern on the pressure drop in the horizontal tube at low liquid velocity, the occurrence of slug flow stops the rise of pressure drop for a short while, before rising again after the air velocity has increased. However, the pressure does not rise abruptly in the tubes with {theta}=30{sup o} and 60{sup o} when the slug/bubbly flow occurs. At low gas and liquid velocity, the pressure drop increases, when the inclination angles changes from horizontal to 30{sup o} and 60{sup o}. Void fraction increases with increasing gas velocity and decreases with increasing liquid velocity. After increasing the inclination angle from horizontal to {theta}=30{sup o} and 60{sup o}, the void fraction appears to be similar, with a

  4. Chemical composition of bioactive pressurized extracts of Romanian aromatic plants.

    PubMed

    Miron, T L; Plaza, M; Bahrim, G; Ibáñez, E; Herrero, M

    2011-07-29

    In this contribution, pressurized liquid extraction (PLE) has been employed to isolate bioactive compounds from three native Romanian plants, oregano (Origanum vulgare), tarragon (Artemisia dracunculus) and wild thyme (Thymus serpyllum). Different PLE conditions have been tested including extraction with water, ethanol and their mixtures in a wide range of extraction temperatures (50-200°C), and the antioxidant capacity of the extracts was measured using different assays (DPPH radical scavenging, TEAC assay and Folin-Ciocalteau assay to measure total phenols). Moreover, a complete chemical characterization by using LC-MS/MS was carried out to be able to correlate the bioactivity with the particular chemical composition of each extract and plant. The use of PLE with water as a solvent at the highest temperature tested (200°C) always provided the highest extraction yields for the three studied plants, being maximum for oregano (>60%). Besides, oregano's pressurized water extracts at lower temperatures (50°C) presented the highest content on total phenols (184.9 mg gallic acid/g extract) and the best antioxidant activities (EC(50) 6.98 μg/ml). In general, oregano extracts were the most active, followed by wild thyme extracts. The antioxidant capacity measured by DPPH assay was highly correlated with the amount of total phenols. Moreover, the use of a LC-MS/MS method allowed the identification of 30 different phenolic compounds in the different extracts, including phenolic acids, flavones, flavanones and flavonols, which have an important influence on the total antioxidant capacity of the different extracts. Copyright © 2010 Elsevier B.V. All rights reserved.

  5. Atmospheric pressure infrared MALDI imaging mass spectrometry for plant metabolomics.

    PubMed

    Li, Yue; Shrestha, Bindesh; Vertes, Akos

    2008-01-15

    The utility of atmospheric pressure infrared MALDI mass spectrometry (AP IR-MALDI) was assessed for plant metabolomics studies. Tissue sections from plant organs, including flowers, ovaries, aggregate fruits, fruits, leaves, tubers, bulbs, and seeds were studied in both positive and negative ion modes. For leaves, single laser pulses sampled the cuticle and upper epidermal cells, whereas multiple pulses were demonstrated to ablate some mesophyll layers. Tandem mass spectra were obtained with collision-activated dissociation to aid with the identification of some observed ions. In the positive mode, most ions were produced as potassium, proton, or sometimes sodium ion adducts, whereas proton loss was dominant in the negative ion mode. Over 50 small metabolites and various lipids were detected in the spectra including, for example, 7 of the 10 intermediates in the citric acid cycle. Key components of the glycolysis pathway occurring in the plant cytosol were found along with intermediates of phospholipid biosynthesis and reactants or products of amino acid, nucleotide, oligosaccharide, and flavonoid biosynthesis. AP IR-MALDI mass spectrometry was used to follow the fluid transport driven by transpiration and image the spatial distributions of several metabolites in a white lily (Lilium candidum) flower petal.

  6. Study on measurement of the coal powder concentration in pneumatic pipes of a boiler with relationship between air velocity and pressure drop

    SciTech Connect

    Pan, W.; Shen, F.; Lin, W.; Chen, L.; Zhang, D.; Wang, Q.; Ke, J.; Quan, W.

    1999-07-01

    According to the theoretical relationship between air velocity and pressure drop in different solid-air mass flow in vertical pipes with the condition of upward air-solid flowing, the experimental research on measuring the coal powder concentration is directed against the pneumatic pipes of a boiler's combustion system in the energy industry. Through analyzing the experimental results, a mathematical model for measuring the coal powder concentration in pneumatic pipes is obtained. Then, the error analysis is done, and the method of on-line measurement and its function are provided.

  7. Noninvasive estimation of transmitral pressure drop across the normal mitral valve in humans: importance of convective and inertial forces during left ventricular filling

    NASA Technical Reports Server (NTRS)

    Firstenberg, M. S.; Vandervoort, P. M.; Greenberg, N. L.; Smedira, N. G.; McCarthy, P. M.; Garcia, M. J.; Thomas, J. D.

    2000-01-01

    OBJECTIVES: We hypothesized that color M-mode (CMM) images could be used to solve the Euler equation, yielding regional pressure gradients along the scanline, which could then be integrated to yield the unsteady Bernoulli equation and estimate noninvasively both the convective and inertial components of the transmitral pressure difference. BACKGROUND: Pulsed and continuous wave Doppler velocity measurements are routinely used clinically to assess severity of stenotic and regurgitant valves. However, only the convective component of the pressure gradient is measured, thereby neglecting the contribution of inertial forces, which may be significant, particularly for nonstenotic valves. Color M-mode provides a spatiotemporal representation of flow across the mitral valve. METHODS: In eight patients undergoing coronary artery bypass grafting, high-fidelity left atrial and ventricular pressure measurements were obtained synchronously with transmitral CMM digital recordings. The instantaneous diastolic transmitral pressure difference was computed from the M-mode spatiotemporal velocity distribution using the unsteady flow form of the Bernoulli equation and was compared to the catheter measurements. RESULTS: From 56 beats in 16 hemodynamic stages, inclusion of the inertial term ([deltapI]max = 1.78+/-1.30 mm Hg) in the noninvasive pressure difference calculation significantly increased the temporal correlation with catheter-based measurement (r = 0.35+/-0.24 vs. 0.81+/-0.15, p< 0.0001). It also allowed an accurate approximation of the peak pressure difference ([deltapc+I]max = 0.95 [delta(p)cathh]max + 0.24, r = 0.96, p<0.001, error = 0.08+/-0.54 mm Hg). CONCLUSIONS: Inertial forces are significant components of the maximal pressure drop across the normal mitral valve. These can be accurately estimated noninvasively using CMM recordings of transmitral flow, which should improve the understanding of diastolic filling and function of the heart.

  8. Noninvasive estimation of transmitral pressure drop across the normal mitral valve in humans: importance of convective and inertial forces during left ventricular filling

    NASA Technical Reports Server (NTRS)

    Firstenberg, M. S.; Vandervoort, P. M.; Greenberg, N. L.; Smedira, N. G.; McCarthy, P. M.; Garcia, M. J.; Thomas, J. D.

    2000-01-01

    OBJECTIVES: We hypothesized that color M-mode (CMM) images could be used to solve the Euler equation, yielding regional pressure gradients along the scanline, which could then be integrated to yield the unsteady Bernoulli equation and estimate noninvasively both the convective and inertial components of the transmitral pressure difference. BACKGROUND: Pulsed and continuous wave Doppler velocity measurements are routinely used clinically to assess severity of stenotic and regurgitant valves. However, only the convective component of the pressure gradient is measured, thereby neglecting the contribution of inertial forces, which may be significant, particularly for nonstenotic valves. Color M-mode provides a spatiotemporal representation of flow across the mitral valve. METHODS: In eight patients undergoing coronary artery bypass grafting, high-fidelity left atrial and ventricular pressure measurements were obtained synchronously with transmitral CMM digital recordings. The instantaneous diastolic transmitral pressure difference was computed from the M-mode spatiotemporal velocity distribution using the unsteady flow form of the Bernoulli equation and was compared to the catheter measurements. RESULTS: From 56 beats in 16 hemodynamic stages, inclusion of the inertial term ([deltapI]max = 1.78+/-1.30 mm Hg) in the noninvasive pressure difference calculation significantly increased the temporal correlation with catheter-based measurement (r = 0.35+/-0.24 vs. 0.81+/-0.15, p< 0.0001). It also allowed an accurate approximation of the peak pressure difference ([deltapc+I]max = 0.95 [delta(p)cathh]max + 0.24, r = 0.96, p<0.001, error = 0.08+/-0.54 mm Hg). CONCLUSIONS: Inertial forces are significant components of the maximal pressure drop across the normal mitral valve. These can be accurately estimated noninvasively using CMM recordings of transmitral flow, which should improve the understanding of diastolic filling and function of the heart.

  9. Evaluation of Capiox FX05 oxygenator with an integrated arterial filter on trapping gaseous microemboli and pressure drop with open and closed purge line.

    PubMed

    Qiu, Feng; Peng, Sophia; Kunselman, Allen; Ündar, Akif

    2010-11-01

    Gaseous microemboli (GME) remain a challenge for cardiopulmonary bypass (CPB) because there is a positive correlation between microemboli exposure during CPB and postoperative neurological injury. Thus, minimizing the number of GME delivered to pediatric patients undergoing CPB procedures would lead to better clinical outcomes. In this study, we used a simulated CPB model to evaluate the effectiveness of capturing GME and the degree of membrane pressure drop for a new membrane oxygenator, Capiox Baby FX05 (Terumo Corporation,Tokyo, Japan), which has an integrated arterial filter with open and closed purge line.We used identical components in this study as our clinical CPB circuit. Three emboli detection and classification quantifier transducers were placed at prepump, preoxygenator, and postoxygenator sites in the circuit.Two flow probes as well as three pressure transducers were placed upstream and downstream of the oxygenator. The system was primed with human blood titrated to 30% hematocrit with Lactated Ringer’s solution.A bolus of air (1 mL) was injected in the prepump site under nonpulsatile perfusion mode at three flow rates (500,750, and 1000 mL/min) and with the purge line either open or closed. Six trials were performed for each unique set-up for a total of 36 trials.All trials were conducted at 35°C. The circuit pressure was kept constant at 100 mm Hg. Both the size and quantity of microemboli detected at postoxygenator site were recorded for 5 min postair injection. It was found that total counts of GME were significantly reduced with the purge line open when compared to keeping the purge line closed (P < 0.0001 at 1000 mL/min). At all flow rates, most of the GME were under 20 microns in size. In terms of microemboli greater than 40 microns, the counts were significantly higher with the purge line closed compared to keeping the purge line open at flow rates of 750 mL/min and 1000 mL/min (P < 0.01). At all flow rates,there is a tiny difference of less

  10. Flow pattern, void fraction and pressure drop of two-phase air-water flow in a horizontal circular micro-channel

    SciTech Connect

    Saisorn, Sira; Wongwises, Somchai

    2008-01-15

    Adiabatic two-phase air-water flow characteristics, including the two-phase flow pattern as well as the void fraction and two-phase frictional pressure drop, in a circular micro-channel are experimentally studied. A fused silica channel, 320 mm long, with an inside diameter of 0.53 mm is used as the test section. The test runs are done at superficial velocity of gas and liquid ranging between 0.37-16 and 0.005-3.04 m/s, respectively. The flow pattern map is developed from the observed flow patterns i.e. slug flow, throat-annular flow, churn flow and annular-rivulet flow. The flow pattern map is compared with those of other researchers obtained from different working fluids. The present single-phase experiments also show that there are no significant differences in the data from the use of air or nitrogen gas, and water or de-ionized water. The void fraction data obtained by image analysis tends to correspond with the homogeneous flow model. The two-phase pressure drops are also used to calculate the frictional multiplier. The multiplier data show a dependence on flow pattern as well as mass flux. A new correlation of two-phase frictional multiplier is also proposed for practical application. (author)

  11. Flow boiling heat transfer and pressure drop analysis of R134a in a brazed heat exchanger with offset strip fins

    NASA Astrophysics Data System (ADS)

    Amaranatha Raju, M.; Ashok Babu, T. P.; Ranganayakulu, C.

    2017-10-01

    The saturated flow boiling heat transfer and friction analysis of R 134a were experimentally analyzed in a brazed plate fin heat exchanger with offset strip fins. Experiments were performed at mass flux range of 50-82 kg/m2 s, heat flux range of 14-22 kW/m2 and quality of 0.32-0.75. The test section consists of three fins, one refrigerant side fin in which the boiling heat transfer was estimated and two water side fins. These three fins are stacked, held together and vacuum brazed to form a plate fin heat exchanger. The refrigerant R134a flowing in middle of the test section was heated using hot water from upper and bottom sides of the test section. The temperature and mass flow rates of water circuit is controlled to get the outlet conditions of refrigerant R134a. Two-phase flow boiling heat transfer and frictional coefficient was estimated based on experimental data for offset strip fin geometry and presented in this paper. The effects of mass flux, heat flux and vapour quality on heat transfer coefficient and pressure drop were investigated. Two-phase local boiling heat transfer coefficient is correlated in terms of Reynolds number factor F, and Martinelli parameter X. Pressure drop is correlated in terms of two-phase frictional multiplier ϕ f , and Martinelli parameter X.

  12. Drop dynamics

    NASA Technical Reports Server (NTRS)

    Elleman, D. D.

    1981-01-01

    The drop dynamics module is a Spacelab-compatible acoustic positioning and control system for conducting drop dynamics experiments in space. It consists basically of a chamber, a drop injector system, an acoustic positioning system, and a data collection system. The principal means of collecting data is by a cinegraphic camera. The drop is positioned in the center of the chamber by forces created by standing acoustic waves generated in the nearly cubical chamber (about 12 cm on a side). The drop can be spun or oscillated up to fission by varying the phse and amplitude of the acoustic waves. The system is designed to perform its experiments unattended, except for start-up and shutdown events and other unique events that require the attention of the Spacelab payload specialist.

  13. High Pressure, Transport Properties of Fluids: Theory and Data from Levitated Fluid-Drops at Combustion-Relevant Temperatures

    NASA Technical Reports Server (NTRS)

    Bellan, J.; Ohaska, K.

    2001-01-01

    The objective of this investigation is to derive a set of consistent mixing rules for calculating diffusivities and thermal diffusion factors over a thermodynamic regime encompassing the subcritical and supercritical ranges. These should serve for modeling purposes, and therefore for accurate simulations of high pressure phenomena such as fluid disintegration, turbulent flows and sprays. A particular consequence of this work will be the determination of effective Lewis numbers for supercritical conditions, thus enabling the examination of the relative importance of heat and mass transfer at supercritical pressures.

  14. Effect on blood pressure of a dietary supplement containing traditional medicinal plants of Côte d'Ivoire.

    PubMed

    Abrogoua, Danho Pascal; Dano, Djédjé Sébastien; Manda, Pierre; Adepo, Aholia Jean-Baptiste; Kablan, Brou Jérôme; Goze, Nomane Bernard; Ehoulé, Kroa

    2012-06-14

    A medicinal composition containing salt (sodium chloride) is given as a traditional dietary supplement to hypertensive patients (TDSHP) in Côte d'Ivoire. It consists of whole plant of Bidens pilosa (Asteraceae) and fresh leaves of Moringa oleifera (Moringaceae). The aim of this study was to establish the scientific basis for the use of this traditional recipe rich in sodium chloride in hypertension settings. We used a total aqueous extract of this traditional dietary supplement containing medicinal plants (Bidens pilosa, Moringa oleifera) and salt (sodium chloride). Experiment was carried out to evaluate its effect on arterial blood pressure of rabbits. The experimental device used for recording blood pressure in rabbits is based on the principle of Ludwig mercury manometer. TDSHP between 5×10(-8) and 5×10(-2) mg/kg caused a dose-dependent hypotension. TDSHP elicited drops in blood pressure ranging between 7.14±4 and 100±7.5%, compared to normal blood pressure of rabbits. Fifty percent effective dose of TDSHP was 3.95×10(-4) mg/kg. Similarly as the hypotension induced by acetylcholine, the one caused by TDSHP at dose of 3.95×10(-4) mg/kg in rabbit was progressively inhibited by atropine, dosed between 5×10(-4) to 5×10(-2) mg/kg. The percentage drop of recorded blood pressure ranged from 50.3±1.87 to 3.71±1.09% compared to the normal value of blood pressure. In the presence of atropine, TDSHP effect was partially inhibited. The same increasing doses of TDSHP reduced significantly the increase of blood pressure induced by adrenaline dosed at 4.76×10(-4) mg/kg from 89.3±2.19 to 1.19±0.59%. The consumption of this traditional dietary supplement is justified in hypertensive patients according to its composition and its ability to reduce blood pressure has been demonstrated experimentally. TDSHP should not be considered as an antihypertensive drug, it remains to us a salt substitute to be taken with moderation with strict adherence to the traditional dose

  15. Determination of musk fragrances in sewage sludge by pressurized liquid extraction coupled to automated ionic liquid-based headspace single-drop microextraction followed by GC-MS/MS.

    PubMed

    Vallecillos, Laura; Borrull, Francesc; Pocurull, Eva

    2012-10-01

    A method for the quantitative determination of ten musk fragrances extensively used in personal care products from sewage sludge was developed by using a pressurized liquid extraction (PLE) followed by an automated ionic liquid-based headspace single-drop microextraction and gas chromatography-tandem mass spectrometry. The influence of main factors on the efficiency of PLE was studied. For all musks, the highest recovery values were achieved using 1 g of pretreated sewage sludge, H(2) O/methanol (1:1) as an extraction solvent, a temperature of 80°C, a pressure of 1500 psi, an extraction time of 5 min, 2 cycles, a 100% flush volume, a purge time of 120 s, and 1 g Florisil as in-cell clean-up extraction sorbent. The use and optimization of an in-cell clean-up sorbent was necessary to remove fatty interferents of the PLE extract that make the subsequent ionic liquid-based headspace single-drop microextraction difficult. Validation parameters, namely LODs and LOQs, ranged from 0.5-1.5 to 2.5-5 ng/g, respectively. Good levels of intra- and interday repeatabilities were obtained analyzing sewage sludge samples spiked at 10 ng/g (n = 3, RSDs < 10%). The method applicability was tested with sewage sludge from different wastewater treatment plants. The analysis revealed the presence of all the polycyclic musks studied at concentrations higher than the LOQs, ranging from 6 to 530 ng/g. However, the nitro musk concentrations were below the LOQs or, in the case of musk xylene, was not detected. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Atmospheric pressure laser desorption/ionization of plant metabolites and plant tissue using colloidal graphite.

    PubMed

    Perdian, D C; Schieffer, G M; Houk, R S

    2010-02-01

    Colloidal graphite is a promising matrix for atmospheric pressure laser desorption/ionization mass spectrometry. Intact [M+H](+) and [M-H](-) ions are readily produced from a wide range of small molecule plant metabolites, particularly anthocyanins, fatty acids, lipids, glycerides, and ceramides. Compared with a more traditional organic acid matrix, colloidal graphite provides more efficient ionization for small hydrophobic molecules and has a much cleaner background spectrum, especially in negative ion mode. Some important metabolites, e.g., fatty acids and glycosylated flavonoids, can be observed from Arabidopsis thaliana leaf and flower petal tissues in situ. Copyright (c) 2010 John Wiley & Sons, Ltd.

  17. Sensitive Determination of Cd in Small-Volume Samples by Miniaturized Liquid Drop Anode Atmospheric Pressure Glow Discharge Optical Emission Spectrometry.

    PubMed

    Jamroz, Piotr; Greda, Krzysztof; Dzimitrowicz, Anna; Swiderski, Krzysztof; Pohl, Pawel

    2017-06-06

    A novel liquid drop anode (LDA) direct current atmospheric pressure glow discharge (dc-APGD) system was applied for direct determination of Cd in liquid microsamples (50 μL) by optical emission spectrometry (OES). The microdischarge was generated in open-to-air atmosphere between a solid pin type tungsten cathode and a liquid drop placed on a graphite disk anode. The arrangement of the graphite disk placed on a PTFE chip platform as well as the solid pin type cathode was simple and robust. The limit of detection (LOD) of Cd for the developed LDA-APGD-OES method was 0.20-0.40 μg L(-1), while precision (as the relative standard deviation for the repeated measurements) was within 2-5%. By using the liquid drop of 50 μL, the linearity range of 1-1000 μg L(-1) was achieved. The effect of addition of the low-molecular weight (LMW) organic compounds, easily ionized elements (EIEs), i.e., Ca, K, Mg, and Na, as well as the foreign ions (Al, Cu, Fe, Mn, Zn) to the solution on the in situ atomization and excitation processes occurred during operation of the LDA-APGD system, and the response of Cd was studied. Validation of the proposed method was demonstrated by analysis of Lobster hepatopancreas (TORT-2), pig kidney (ERM-BB186), and groundwater (ERM-CA615) certified reference materials (CRMs) and recoveries of Cd from water samples spiked with 25 μg L(-1) of Cd. Very good agreement between the found and certified values of Cd in the CRMs (the recoveries were within the range of 96.3-99.6%) indicated trueness of the method and its reliability for determination of traces of Cd. In the case of the spiked water samples, the recoveries obtained were in the range from 95.2 to 99.5%.

  18. Effect of oscillation frequency on wall shear stress and pressure drop in a rectangular channel for heat transfer applications

    NASA Astrophysics Data System (ADS)

    Blythman, R.; Persoons, T.; Jeffers, N.; Murray, DB

    2016-09-01

    The exploitation of flow unsteadiness in microchannels is a potentially useful technique for enhancing cooling of future photonics systems. Pulsation is thought to alter the thickness of the hydrodynamic and thermal boundary layers, and hence affect the overall thermal resistance of the heat sink. While the mechanical and thermal problems are inextricably linked, it is useful to decouple the parameters to better understand the mechanisms underlying any heat transfer enhancement. The current work characterises the behaviour of the wall shear stress and pressure gradient with frequency, using experimental particle image velocimetry (PIV) measurements and the analytical solution for oscillatory flow in a two-dimensional rectangular channel. Both wall shear stress and pressure gradient are augmented with frequency compared to steady flow, though the pressure gradient increases more significantly as a result of growing inertial losses. The three distinct regimes of unsteadiness are shown to display unique relationships between the parameters pertinent to heat transfer and should therefore be considered independently with respect to thermal enhancement capability. To this end, the regime boundaries are estimated at Womersley number Wo = 1.6 and 28.4 in a rectangular channel, based on the contribution of viscous and inertial losses.

  19. Ophthalmic administration of a 10-fold-lower dose of conventional nanoliposome formulations caused levels of intraocular pressure similar to those induced by marketed eye drops.

    PubMed

    Arroyo, C M; Quinteros, D; Cózar-Bernal, M J; Palma, S D; Rabasco, A M; González-Rodríguez, M L

    2017-09-15

    The purpose of this study was to compare the in vivo efficacy of several timolol (TM)-loaded liposomal formulations with current TM antiglaucoma treatment (aqueous 0.5% w/v eye drops). In this study, conventional liposomes (CL) and deformable liposomes, without (DL1) and with ethanol (DL2) were prepared and characterized. In addition, in vitro release and permeation studies, as well as in vivo lowering intraocular pressure (IOP) and biocompatibility studies were performed. It was found that the quali and quantitative lipid bilayer composition played a significant role in modifying the physical properties of vesicles. The deformability study and electronic microscopy images revealed that membrane elasticity of DL1 and DL2 was much higher than CL. However, in vitro permeation results showed that the flux and permeability coefficient were significantly higher in CL compared to DL. The IOP study revealed that TM-loaded CL showed the best pharmacological activity, in comparison to deformable vesicles. Compared to the eye drops, CL formulation could equally reduce the IOP but using a concentration 10-fold lower, whereas the effective time was significantly longer. In addition, the formulations showed no irritant effects after instillation on the ocular surface. Copyright © 2017. Published by Elsevier B.V.

  20. Air atmospheric pressure plasma jet pretreatment for drop-wise loading of dexamethasone on hydroxyapatite scaffold for increase of osteoblast attachment.

    PubMed

    Lee, Jung-Hwan; Kwon, Jae-Sung; Kim, Yong Hee; Choi, Eun Ha; Kim, Kwang-Mahn; Kim, Kyoung-Nam

    2014-10-01

    Periodontal disease affects alveolar bone resorption around the involved teeth. To gain bone height, bone graft materials have been widely used with drug carriers. Application of an atmospheric pressure plasma jet (APPJ) treatment is widely studied due to its ability to change surface characteristics without topographical change. The aim of this study is to identify whether the air APPJ (AAPPJ) treatment before drop-wise loading performance could change loaded amount of dexamethasone, and induce increase of cell attachment and proliferation. The results suggested that AAPPJ treatment decreased the contact angle down to about 13 degrees, which increased gradually but significantly lowered at least 4 days compared to no-treated group. After AAPPJ treatment, hydrocarbon was removed with change of zeta potential into positive charge. However, the AAPPJ treatment did not change the quantity or releasing profile of dexamethasone (p > 0.05). Confocal analysis combined with DNA proliferation analysis showed increase of osteoblast attachment and proliferation. Hence, AAPPJ could be a useful pretreatment method before drop-wise loading on HA scaffold with dexamethasone for increase of osteoblast attachment.

  1. Heat transfer and pressure drop in a compact pin-fin heat exchanger with pin orientation at 18 deg to the flow direction

    NASA Technical Reports Server (NTRS)

    Olson, D. A.

    1991-01-01

    The heat transfer and pressure drop characteristics of a novel, compact heat exchanger in helium gas were measured at 3.5 MPa and Reynolds numbers of 450 to 12,000. The pin-fin specimen consisted of pins, 0.51 mm high and spaced 2.03 mm on centers, spanning a channel through which the helium flows; the angle of the row of pins to the flow direction was 18 deg. The specimen was radiatively heated on the top side at heat fluxes up to 74 W/sq cm and insulated on the back side. Correlations were developed for the friction factor and Nusselt number. The Nusselt number compares favorably to those of past studies of staggered pin-fins, when the measured temperatures are extrapolated to the temperature of the wall-fluid interface.

  2. A Numerical Procedure for Flow Distribution and Pressure Drops for U and Z Type Configurations Plate Heat Exchangers with Variable Coefficients

    NASA Astrophysics Data System (ADS)

    López, R.; Lecuona, A.; Ventas, R.; Vereda, C.

    2012-11-01

    In Plate Heat Exchangers it is important to determine the flow distribution and pressure drops, because they affect directly the performance of a heat exchanger [1]. This work proposes an incompressible, one-dimensional, steady state, discrete model allowing for variable overall momentum coefficients to determine these magnitudes. The model consists on a modified version of the Bajura and Jones [2] model for dividing and combining flow manifolds. The numerical procedure is based on the finite differences approximation approach proposed by Datta and Majumdar [3]. A linear overall momentum coefficient distribution is used in the dividing manifold, but the model is not limited to linear distributions. Comparisons are made with experimental, numerical and analytical data, yielding good results.

  3. Investigations of Pressure Drops during Piston Flow Pneumatic Conveying of Ice Cubes and Applying It to High Density Conveying of Cold Energy

    NASA Astrophysics Data System (ADS)

    Ohira, Akiyoshi; Yanadori, Michio; Tsubota, Yuji

    To overcome the defect of conventional chilled water systems, we propose pneumatic conveying of ice cubes. We conducted experiments to investigate the pressure drops during pneumatic conveying of ice cubes in a prototype conveyance pipe, and obtained the following results : (1)The mean velocity of the ice cubes is proportional to the mean velocity of the conveying air flow regardless of balls in the pipe or the volume fraction of the ice cubes. (2) Difference in the velocity of the air flow cause variations in the density of ice cubes. If we convey ice cubes with balls, it is possible to convey a higher density. (3) The volume fraction of this method is about 10 times that of the previous experimental results. (4)The pump power of this proposed conveyance system is reduced to about 0.71 to 0.59 times that of the conventional chilled water systems.

  4. Smooth- and enhanced-tube heat transfer and pressure drop : Part I. Effect of Prandtl number with air, water, and glycol/water mixtures.

    SciTech Connect

    Obot, N. T.; Das, L.; Rabas, T. J.

    2000-11-14

    An extensive experimental investigation was carried out to determine the pressure drop and heat transfer characteristics in laminar, transitional, and turbulent flow through one smooth tube and twenty-three enhanced tubes. The working fluids for the experiments were air, water, ethylene glycol, and ethylene glycol/water mixtures; Prandtl numbers (Pr) ranged from 0.7 to 125.3. The smooth-tube experiments were carried out with Pr values of 0.7, 6.8, 24.8, 39.1, and 125.3; Pr values of 0.7, 6.8, and 24.8 were tested with enhanced tubes. Reynolds number (Re) range (based on the maximum internal diameter of a tube) was 200 to 55,000, depending on Prandtl number and tube geometry. The results are presented and discussed in this paper.

  5. Overall heat transfer coefficient and pressure drop in a typical tubular exchanger employing alumina nano-fluid as the tube side hot fluid

    NASA Astrophysics Data System (ADS)

    Kabeel, A. E.; Abdelgaied, Mohamed

    2016-08-01

    Nano-fluids are used to improve the heat transfer rates in heat exchangers, especially; the shell-and-tube heat exchanger that is considered one of the most important types of heat exchangers. In the present study, an experimental loop is constructed to study the thermal characteristics of the shell-and-tube heat exchanger; at different concentrations of Al2O3 nonmetallic particles (0.0, 2, 4, and 6 %). This material concentrations is by volume concentrations in pure water as a base fluid. The effects of nano-fluid concentrations on the performance of shell and tube heat exchanger have been conducted based on the overall heat transfer coefficient, the friction factor, the pressure drop in tube side, and the entropy generation rate. The experimental results show that; the highest heat transfer coefficient is obtained at a nano-fluid concentration of 4 % of the shell side. In shell side the maximum percentage increase in the overall heat transfer coefficient has reached 29.8 % for a nano-fluid concentration of 4 %, relative to the case of the base fluid (water) at the same tube side Reynolds number. However; in the tube side the maximum relative increase in pressure drop has recorded the values of 12, 28 and 48 % for a nano-material concentration of 2, 4 and 6 %, respectively, relative to the case without nano-fluid, at an approximate value of 56,000 for Reynolds number. The entropy generation reduces with increasing the nonmetallic particle volume fraction of the same flow rates. For increase the nonmetallic particle volume fraction from 0.0 to 6 % the rate of entropy generation decrease by 10 %.

  6. Experimental study of the effects of bleed holes on heat transfer and pressure drop in trapezoidal passages with tapered turbulators

    SciTech Connect

    Taslim, M.E.; Li, T.; Spring, S.D.

    1995-04-01

    Trailing edge cooling cavities in modern gas turbine blades often have trapezoidal cross-sectional areas of relatively low aspect ratio. To enhance cooling effectiveness in these passages, they are roughened with tapered turbulators. Furthermore, to provide additional cooling for the trailing edge, the cooling air may be ejected through trailing edge slots as it moves radially along the cooling passage. The tapered turbulators, in conjunction with the presence of these slots along the smaller base of the trapezoidal cavity, create both spanwise and longitudinal variations in heat transfer coefficient on the turbulated walls. Moreover, the continuous variation of cooling air velocity along these passages causes a continuous change in static pressure, which also requires investigation. Liquid crystals are used in this experimental investigation to study the effects of tapered turbulators on heat transfer coefficients in trailing edge passages with and without bleed holes. The tapered turbulators are configured on two opposite walls of the trapezoidal test section in a staggered arrangement with an angle of attack to the mainstream flow, {alpha}, of 90 deg. Nine different test geometries consisting of two passage aspect ratios, AR, were tested over a range of turbulator aspect ratios, AR{sub t}, blockage ratios, e{sub max}/D{sub h}, pitch-to-height ratios, S/e{sub max}, and Reynolds numbers. Channel pressure losses were also measured and both heat transfer and friction factor results for several geometries are compared. It is concluded that (a) there exists a large spanwise variation in heat transfer coefficient in test sections with no bleed holes, (b) adding bleed holes to the smaller base of the trapezoidal cavity gives a spanwise velocity component to the mainstream flow and reduces this variation, and (c) Nusselt numbers measured in the test sections with bleed holes correlate well with local Reynolds number.

  7. Plant hydraulic conductance measured by the high pressure flow meter in crop plants.

    PubMed

    Tsuda, M; Tyree, M T

    2000-04-01

    A new high pressure flow meter (HPFM) method for measuring plant hydraulic conductances (K) was investigated to examine whether its results are comparable to those from a conventional evaporative flux (EF) method in crops. Hydraulic conductance (K) was measured by the two methods under quasi-steady-state conditions in six crops grown in pots: soybean (Glycine max L. Merr. cv. Tsurunoko daizu), sunflower (Helianthus annuus L. cv. Russian mammoth), kidney bean (Phaseolus vulgaris L. cv. Tsurunashi morocco), tomato (Lycopersicon esculentum Mill. cv. Sekai-ichi), green pepper (Capsicum annuum L. cv. shishitou), and eggplant (Solanum melongena L. cv. Seiguro chunaga nasu). There was a 1:1 agreement between K values measured by the two methods for K values of whole plant, root and stem, and leaf under quasi-steady-state conditions. Leaf water potential (psi leaf) and evaporative flux density (E) in sunflower was curvilinear, indicating whole plant K estimated by the EF method increased with increase of E. Predicted psi leaf (= E divided by whole plant K measured by the HPFM method) agreed with measured psi leaf. Diurnal changes were also found in K measured by the HPFM confirming that K changed in response to temperature and E. The HPFM revealed that variable conductance was located in all organs: roots, stems, petioles, and leaves. These observations indicated that the HPFM is valid for crops as well as for trees (as previously established by Tsuda and Tyree) and has advantages over the EF method because of the speed and ease of the HPFM method.

  8. Pressure Drop Versus Flow Rate Analysis of the Limited Streamer Tube Gas System of the BaBar Muon Detector Upgrade

    SciTech Connect

    Yi, M.

    2004-09-03

    It has been proposed that Limited Streamer Tubes (LST) be used in the current upgrade of the muon detector in the BaBar detector. An LST consists of a thin silver plated wire centered in a graphite-coated cell. One standard LST tube consists of eight such cells, and two or three such tubes form an LST module. Under operation, the cells are filled with a gas mixture of CO{sub 2}, argon and isobutane. During normal operation of the detector, the gas will be flushed out of the system at a constant low rate of one volume change per day. During times such as installation, however, it is often desired to flush and change the LST gas volumes very rapidly, leading to higher than normal pressure which may damage the modules. This project studied this pressure as a function of flow rate and the number of modules that are put in series in search of the maximal safe flow rate at which to flush the modules. Measurements of pressure drop versus flow rate were taken using a flow meter and a pressure transducer on configurations of one to five modules put in series. Minimal Poly-Flo tubing was used for all connections between test equipment and modules. They contributed less than 25% to all measurements. A ratio of 0.00022 {+-} 0.00001 mmHg per Standard Cubic Centimeter per Minute (SCCM) per module was found, which was a slight overestimate since it included the contributions from the tubing connections. However, for the purpose of finding a flow rate at which the modules can be safely flushed, this overestimate acts as a safety cushion. For a standard module with a volume of 16 liters and a known safe overpressure of 2 inches of water, the ratio translates into a flow rate of 17000 {+-} 1000SCCM and a time requirement of 56 {+-} 5 seconds to flush an entire module.

  9. Flow rate/pressure drop data gathered from testing a sample of the Space Shuttle Strain Isolation Pad (SIP): Effects of ambient pressure combined with tension and compression conditions

    NASA Technical Reports Server (NTRS)

    Springfield, R. D.; Lawing, P. L.

    1983-01-01

    Tests were conducted on a sample of strain isolation pad (SIP) typical of that used in the shuttle orbiter thermal protection system to determine the characteristics of SIP internal flow. Data obtained were pressure drop as a function of flow rate for a range of ambient pressures representing various points along the Shuttle trajectory and for stretched and compressed conditions of the SIP. Flow was in the direction of the weave parallel to most of the fibers. The data are plotted in several standard engineering formats in order to be of maximum utility to the user. In addition to providing support to the Space Shuttle Program, these data are a source of experimental information on flow through fiberous (rather than the more usual sand bed type) porous media.

  10. [Effect of plant-associated methanolic bacteria on methane and methanol concentration dynamics in atmosphere of pressurized chamber].

    PubMed

    Berkovich, Iu A; Doronina, N V; Fedorov, D N; Mukhamedieva, L N; Mikos, K N; Krivobock, N M; Smolianin, V G; Smolianina, S O; Shanturin, N A

    2010-01-01

    Stability of Chinese cabbage crop colonization by methanolic bacteria Methylovorus mays, Methylomonas methanica and Methylosinus trichosporium inoculated using a space-applicable method was evaluated. Besides, trends of methane and methanol concentrations in the pressurized chamber with inoculated and uninoculated crops were calculated. Methylovorus mays and Methylosinus trichosporium were shown to establish more stable colonization as compared to Methylomonas methanica. Also, stable association of methanolic bacteria with plants reduced airborne methanol 75% faster owing to its uptake by bacteria. Therefore, inoculation of these microorganisms can be viewed as a promising method of controlling volatile pollutants in space vehicle atmosphere. Methane drop after 6-hour exposure to inoculated control and test crops was not significant.

  11. Impact of radiation embrittlement on integrity of pressure vessel supports for two PWR (pressurized-water-reactor) plants

    SciTech Connect

    Cheverton, R.D.; Pennell, W.E.; Robinson, G.C.; Nanstad, R.K.

    1988-01-01

    Recent pressure-vessel surveillance data from the High Flux Isotope Reactor (HFIR) indicate an embrittlement fluence-rate effect that is applicable to the evaluation of the integrity of light-water reactor (LWR) pressure vessel supports. A preliminary evaluation using the HFIR data indicated increases in the nil ductility transition temperature at 32 effective full-power years (EFPY) of 100 to 130/degree/C for pressurized-water-reactor (PWR) vessel supports located in the cavity at midheight of the core. This result indicated a potential problem with regard to life expectancy. However, an accurate assessment required a detailed, specific-plant, fracture-mechanics analysis. After a survey and cursory evaluation of all LWR plants, two PWR plants that appeared to have a potential problem were selected. Results of the analyses indicate minimum critical flaw sizes small enough to be of concern before 32 EFPY. 24 refs., 16 figs., 7 tabs.

  12. Experimental investigation of heat transfer and pressure drop characteristics of water and glycol-water mixture in multi-port serpentine microchannel slab heat exchangers

    NASA Astrophysics Data System (ADS)

    Khan, Md Mesbah-ul Ghani

    Microchannels have several advantages over traditional large tubes. Heat transfer using microchannels recently have attracted significant research and industrial design interests. Open literatures leave with question on the applicability of classical macroscale theory in microchannels. Better understanding of heat transfer in various microchannel geometries and building experimental database are continuously urged. The purpose of this study is to contribute the findings and data to this emerging area through carefully designed and well controlled experimental works. The commercially important glycol-water mixture heat transfer fluid and multiport slab serpentine heat exchangers are encountered in heating and cooling areas, e.g. in automotive, aircraft, and HVAC industries. For a given heat duty, the large diameter tubes experience turbulent flow whereas the narrow channels face laminar flow and often developing flow. Study of low Reynolds number developing glycol-water mixture laminar flow in serpentine microchannel heat exchanger with parallel multi-port slab is not available in the open literature. Current research therefore experimentally investigates glycol-water mixture and water in simultaneously developing laminar flows. Three multiport microchannel heat exchangers; straight and serpentine slabs, are used for each fluid. Friction factors of glycol-water mixture and water flows in straight slabs are higher than conventional fully developed laminar flow. If a comprehensive pressure balance is introduced, the results are well compared with conventional Poiseuille theory. Similar results are found in serpentine slab. The pressure drop for the straight core is the highest, manifolds are the intermediate, and serpentine is the least; which are beneficial for heat exchangers. The heat transfer results in serpentine slab for glycol-water mixture and water are higher and could not be compared with conventional fully developed and developing flow correlations. New

  13. Two-phase frictional pressure drop of R-134a and R-410A refrigerant-oil mixtures in straight tubes and U-type wavy tubes

    SciTech Connect

    Chen, Ing Youn; Wu, Yu-Shi; Chang, Yu-Juei; Wang, Chi-Chuan

    2007-02-15

    This study presents single-phase and two-phase pressure drop data for R-134a/oil mixture flowing in a wavy tube with inner diameter of D=5.07mm and curvature ratio 2R/D=5.18 and R-410A/oil mixture flowing in a wavy tube of D=3.25mm and 2R/D=3.91. Both mixtures have oil concentration C=0%, 1%, 3% and 5% for the tests. The ratio of frictional factor between U-bend in wavy tube and straight tube (f{sub C}/f{sub S}) is about 3.5 for Re<2500 and is approximate 2.5 for Re=3500-25,000 for oil and liquid R-134a mixture flowing in the 5.07mm diameter wavy tube. The influence of oil concentration on single-phase friction factor is negligible, provided that the properties are based on the mixture of lubricant and refrigerant. The ratio between two-phase pressure gradients of U-bend and straight tube is about 2.5-3.5. This ratio is increased with oil concentration and vapor quality. The influence of oil is augmented at a higher mass flux for liquid spreading around the periphery at an annular flow pattern. Moreover, the influence of lubricant becomes more evident of a U-bend configuration. This is associated the induced swirled flow motion and an early change of flow pattern from stratified to annular flow pattern. The frictional two-phase multiplier for straight tube can be fairly correlated by using the Chisholm correlation for the data having Martinelli parameter X between 0.05 and 1.0. Fridel correlation also shows a good agreement with a mean deviation of 17.6% to all the straight tube data. For the two-phase pressure drop in U-bend, the revised Geary correlation agrees very well with the R-134a and R-410A oil-refrigerant data with a mean deviation of 16.4%. (author)

  14. A novel target-type low pressure drop bidirectional optoelectronic air flow sensor for infant artificial ventilation: Measurement principle and static calibration

    SciTech Connect

    Saccomandi, Paola; Schena, Emiliano; Silvestri, Sergio

    2011-02-15

    An optoelectronic target-type volumetric air flow-rate transducer for bidirectional measurements is presented. The sensor is composed of a T-shaped target and two nominally identical LED-photodiode couples which are operated in differential mode. The sensitive surfaces of the photodiodes are differentially shadowed by the deflection of the target, which in turn depends on the gas flow-rate. The principle of operation is described in mathematical terms and the design parameters have been optimized in order to obtain the highest sensitivity along with minimal pressure drop and reduced dimensions. The sensor is placed in a 20 mm diameter hose and was tested with air flow-rate in the typical temperature range of mechanical ventilation between 20 and 40 deg. C. The theoretical model was validated through experiments carried out in the volumetric flow range from -7.0 to +7.0 l min{sup -1}. The nonlinear behavior allows sensitivities equal to 0.6 V l{sup -1} min for flow rates ranging from -2.0 to +2.0 l min{sup -1}, equal to 2.0 V l{sup -1} min for flow rates ranging from -3.0 to -2.0 l min{sup -1} and from +2.0 to +3.0 l min{sup -1}, up to 5.7 V l{sup -1} min at higher flow rates ranging from -7.0 to -3.0 l min{sup -1} and from +3.0 to +7.0 l min{sup -1}. The linear range extends from 3.0 to 7.0 l min{sup -1} with constant sensitivity equal to 5.7 V l{sup -1} min. The sensor is able to detect a flow-rate equal to 1.0 l min{sup -1} with a sensitivity of about 400 mV l{sup -1} min. The differential nature of the output minimizes the influence of the LEDs' power supply variations and allows to obtain a repeatability in the order of 3% of full scale output. The small pressure drop produced by the sensor placed in-line the fluid stream, of about 2.4 Pa at 7 l min{sup -1}, corresponds to a negligible fluid dynamic resistance lower than 0.34 Pa l{sup -1} min.

  15. A novel target-type low pressure drop bidirectional optoelectronic air flow sensor for infant artificial ventilation: measurement principle and static calibration.

    PubMed

    Saccomandi, Paola; Schena, Emiliano; Silvestri, Sergio

    2011-02-01

    An optoelectronic target-type volumetric air flow-rate transducer for bidirectional measurements is presented. The sensor is composed of a T-shaped target and two nominally identical LED-photodiode couples which are operated in differential mode. The sensitive surfaces of the photodiodes are differentially shadowed by the deflection of the target, which in turn depends on the gas flow-rate. The principle of operation is described in mathematical terms and the design parameters have been optimized in order to obtain the highest sensitivity along with minimal pressure drop and reduced dimensions. The sensor is placed in a 20 mm diameter hose and was tested with air flow-rate in the typical temperature range of mechanical ventilation between 20 and 40 °C. The theoretical model was validated through experiments carried out in the volumetric flow range from -7.0 to +7.0 l min(-1). The nonlinear behavior allows sensitivities equal to 0.6 V l(-1) min for flow rates ranging from -2.0 to +2.0 l min(-1), equal to 2.0 V l(-1) min for flow rates ranging from -3.0 to -2.0 l min(-1) and from +2.0 to +3.0 l min(-1), up to 5.7 V l(-1) min at higher flow rates ranging from -7.0 to -3.0 l min(-1) and from +3.0 to +7.0 l min(-1). The linear range extends from 3.0 to 7.0 l min(-1) with constant sensitivity equal to 5.7 V l(-1) min. The sensor is able to detect a flow-rate equal to 1.0 l min(-1) with a sensitivity of about 400 mV l(-1) min. The differential nature of the output minimizes the influence of the LEDs' power supply variations and allows to obtain a repeatability in the order of 3% of full scale output. The small pressure drop produced by the sensor placed in-line the fluid stream, of about 2.4 Pa at 7 l min(-1), corresponds to a negligible fluid dynamic resistance lower than 0.34 Pa l(-1) min.

  16. Pressure drop of two-phase helium along long cryogenic flexible transfer lines to support a superconducting RF operation at its cryogenic test stand.

    PubMed

    Chang, M H; Tsai, M H; Wang, Ch; Lin, M C; Chung, F T; Yeh, M S; Chang, L H; Lo, C H; Yu, T C; Chen, L J; Liu, Z K

    2016-01-01

    Establishing a stand-alone cryogenic test stand is of vital importance to ensure the highly reliable and available operation of superconducting radio-frequency module in a synchrotron light source. Operating a cryogenic test stand relies strongly on a capability to deliver two-phase helium along long cryogenic transfer lines. A newly constructed cryogenic test stand with flexible cryogenic transfer lines of length 220 m at National Synchrotron Radiation Research Center is required to support a superconducting radio-frequency module operated at 126.0 kPa with a 40-W dynamic load for a long-term reliability test over weeks. It is designed based on a simple analytical approach with the introduction of a so-called tolerance factor that serves to estimate the pressure drops in transferring a two-phase helium flow with a substantial transfer cryogenic heat load. Tolerance factor 1.5 is adopted based on safety factor 1.5 commonly applied in cryogenic designs to estimate the total mass flow rate of liquid helium demanded. A maximum 60-W dynamic load is verified with experiment measured with heater power 60 W instead after the cryogenic test stand has been installed. Aligning the modeled cryogenic accumulated static heat load with the results measured in situ, actual tolerance factor 1.287 is obtained. The feasibility and validity of our simple analytical approach with actual tolerance factor 1.287 have been scrutinized by using five test cases with varied operating conditions. Calculated results show the discrepancies of the pressure drops between the estimated and measured values for both liquid helium and cold gaseous helium transfer lines have an underestimate 0.11 kPa and an overestimate 0.09 kPa, respectively. A discrepancy is foreseen, but remains acceptable for engineering applications from a practical point of view. The simple analytical approach with the introduction of a tolerance factor can provide not only insight into optimizing the choice of each lossy

  17. A novel target-type low pressure drop bidirectional optoelectronic air flow sensor for infant artificial ventilation: Measurement principle and static calibration

    NASA Astrophysics Data System (ADS)

    Saccomandi, Paola; Schena, Emiliano; Silvestri, Sergio

    2011-02-01

    An optoelectronic target-type volumetric air flow-rate transducer for bidirectional measurements is presented. The sensor is composed of a T-shaped target and two nominally identical LED-photodiode couples which are operated in differential mode. The sensitive surfaces of the photodiodes are differentially shadowed by the deflection of the target, which in turn depends on the gas flow-rate. The principle of operation is described in mathematical terms and the design parameters have been optimized in order to obtain the highest sensitivity along with minimal pressure drop and reduced dimensions. The sensor is placed in a 20 mm diameter hose and was tested with air flow-rate in the typical temperature range of mechanical ventilation between 20 and 40 °C. The theoretical model was validated through experiments carried out in the volumetric flow range from -7.0 to +7.0 l min-1. The nonlinear behavior allows sensitivities equal to 0.6 V l-1 min for flow rates ranging from -2.0 to +2.0 l min-1, equal to 2.0 V l-1 min for flow rates ranging from -3.0 to -2.0 l min-1 and from +2.0 to +3.0 l min-1, up to 5.7 V l-1 min at higher flow rates ranging from -7.0 to -3.0 l min-1 and from +3.0 to +7.0 l min-1. The linear range extends from 3.0 to 7.0 l min-1 with constant sensitivity equal to 5.7 V l-1 min. The sensor is able to detect a flow-rate equal to 1.0 l min-1 with a sensitivity of about 400 mV l-1 min. The differential nature of the output minimizes the influence of the LEDs' power supply variations and allows to obtain a repeatability in the order of 3% of full scale output. The small pressure drop produced by the sensor placed in-line the fluid stream, of about 2.4 Pa at 7 l min-1, corresponds to a negligible fluid dynamic resistance lower than 0.34 Pa l-1 min.

  18. A single recessive gene conferring short leaves in romaine x Latin type lettuce (Lactuca sativa L.) crosses, and its effect on plant morphology and resistance to lettuce drop caused by Sclerotinia minor Jagger.

    USDA-ARS?s Scientific Manuscript database

    Understanding the relationship between plant morphology and disease resistance is crucial to successful breeding, particularly resistance to lettuce drop caused by Sclerotinia minor. Latin type lettuce cultivars are small plants with upright leaves longer than they are wide, similar to romaine type...

  19. Pressure Reducer for Coal Gasifiers

    NASA Technical Reports Server (NTRS)

    Kendall, James M., Sr.

    1983-01-01

    Quasi-porous-plug pressure reducer is designed for gases containing abrasive particles. Gas used to generate high pressure steam to drive electric power generators. In giving up heat to steam, gas drops in temperature. Device used for coal gasification plants.

  20. Ultrahigh pressure extraction of bioactive compounds from plants-A review.

    PubMed

    Xi, Jun

    2017-04-13

    Extraction of bioactive compounds from plants is one of the most important research areas for pharmaceutical and food industries. Conventional extraction techniques are usually associated with longer extraction times, lower yields, more organic solvent consumption, and poor extraction efficiency. A novel extraction technique, ultrahigh pressure extraction, has been developed for the extraction of bioactive compounds from plants, in order to shorten the extraction time, decrease the solvent consumption, increase the extraction yields, and enhance the quality of extracts. The mild processing temperature of ultrahigh pressure extraction may lead to an enhanced extraction of thermolabile bioactive ingredients. A critical review is conducted to introduce the different aspects of ultrahigh pressure extraction of plants bioactive compounds, including principles and mechanisms, the important parameters influencing its performance, comparison of ultrahigh pressure extraction with other extraction techniques, advantages, and disadvantages. The future opportunities of ultrahigh pressure extraction are also discussed.

  1. Turbulent Kinetic Energy Measurement Using Phase Contrast MRI for Estimating the Post-Stenotic Pressure Drop: In Vitro Validation and Clinical Application.

    PubMed

    Ha, Hojin; Kim, Guk Bae; Kweon, Jihoon; Huh, Hyung Kyu; Lee, Sang Joon; Koo, Hyun Jung; Kang, Joon-Won; Lim, Tae-Hwan; Kim, Dae-Hee; Kim, Young-Hak; Kim, Namkug; Yang, Dong Hyun

    2016-01-01

    Although the measurement of turbulence kinetic energy (TKE) by using magnetic resonance imaging (MRI) has been introduced as an alternative index for quantifying energy loss through the cardiac valve, experimental verification and clinical application of this parameter are still required. The goal of this study is to verify MRI measurements of TKE by using a phantom stenosis with particle image velocimetry (PIV) as the reference standard. In addition, the feasibility of measuring TKE with MRI is explored. MRI measurements of TKE through a phantom stenosis was performed by using clinical 3T MRI scanner. The MRI measurements were verified experimentally by using PIV as the reference standard. In vivo application of MRI-driven TKE was explored in seven patients with aortic valve disease and one healthy volunteer. Transvalvular gradients measured by MRI and echocardiography were compared. MRI and PIV measurements of TKE are consistent for turbulent flow (0.666 < R2 < 0.738) with a mean difference of -11.13 J/m3 (SD = 4.34 J/m3). Results of MRI and PIV measurements differ by 2.76 ± 0.82 cm/s (velocity) and -11.13 ± 4.34 J/m3 (TKE) for turbulent flow (Re > 400). The turbulence pressure drop correlates strongly with total TKE (R2 = 0.986). However, in vivo measurements of TKE are not consistent with the transvalvular pressure gradient estimated by echocardiography. These results suggest that TKE measurement via MRI may provide a potential benefit as an energy-loss index to characterize blood flow through the aortic valve. However, further clinical studies are necessary to reach definitive conclusions regarding this technique.

  2. Heat transfer and pressure drop characteristics of the tube bank fin heat exchanger with fin punched with flow redistributors and curved triangular vortex generators

    NASA Astrophysics Data System (ADS)

    Liu, Song; Jin, Hua; Song, KeWei; Wang, LiangChen; Wu, Xiang; Wang, LiangBi

    2017-10-01

    The heat transfer performance of the tube bank fin heat exchanger is limited by the air-side thermal resistance. Thus, enhancing the air-side heat transfer is an effective method to improve the performance of the heat exchanger. A new fin pattern with flow redistributors and curved triangular vortex generators is experimentally studied in this paper. The effects of the flow redistributors located in front of the tube stagnation point and the curved vortex generators located around the tube on the characteristics of heat transfer and pressure drop are discussed in detail. A performance comparison is also carried out between the fins with and without flow redistributors. The experimental results show that the flow redistributors stamped out from the fin in front of the tube stagnation points can decrease the friction factor at the cost of decreasing the heat transfer performance. Whether the combination of the flow redistributors and the curved vortex generators will present a better heat transfer performance depends on the size of the curved vortex generators. As for the studied two sizes of vortex generators, the heat transfer performance is promoted by the flow redistributors for the fin with larger size of vortex generators and the performance is suppressed by the flow redistributors for the fin with smaller vortex generators.

  3. Evaluation of browning ratio in an image analysis of apple slices at different stages of instant controlled pressure drop-assisted hot-air drying (AD-DIC).

    PubMed

    Gao, Kun; Zhou, Linyan; Bi, Jinfeng; Yi, Jianyong; Wu, Xinye; Zhou, Mo; Wang, Xueyuan; Liu, Xuan

    2017-06-01

    Computer vision-based image analysis systems are widely used in food processing to evaluate quality changes. They are able to objectively measure the surface colour of various products since, providing some obvious advantages with their objectivity and quantitative capabilities. In this study, a computer vision-based image analysis system was used to investigate the colour changes of apple slices dried by instant controlled pressure drop-assisted hot air drying (AD-DIC). The CIE L* value and polyphenol oxidase activity in apple slices decreased during the entire drying process, whereas other colour indexes, including CIE a*, b*, ΔE and C* values, increased. The browning ratio calculated by image analysis increased during the drying process, and a sharp increment was observed for the DIC process. The change in 5-hydroxymethylfurfural (5-HMF) and fluorescent compounds (FIC) showed the same trend with browning ratio due to Maillard reaction. Moreover, the concentrations of 5-HMF and FIC both had a good quadratic correlation (R(2)  > 0.998) with the browning ratio. Browning ratio was a reliable indicator of 5-HMF and FIC changes in apple slices during drying. The image analysis system could be used to monitor colour changes, 5-HMF and FIC in dehydrated apple slices during the AD-DIC process. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

  4. Validated heat-transfer and pressure-drop prediction methods based on the discrete-element method: Phase 2, two-dimensional rib roughness

    SciTech Connect

    James, C.A.; Hodge, B.K.; Taylor, R.P.

    1993-05-01

    Surface roughness is a commonly used approach for enhancing the rate of heat transfer of surfaces, such as in heat-exchanger tubes. Because the improved thermal performance of roughened surfaces is at the expense of increased flow resistance (increased pressure drop or friction factor), accurate prediction techniques for determining the friction factors and Nusselt numbers for roughened surfaces are required if such features are to be considered as design options. This report presents the results of the second phase of a research program sponsored by Argonne National Laboratory to validate models for the prediction of friction factors and Nusselt numbers for fully developed turbulent flow in enhanced heat-exchanger tubes. The first phase was concerned with validating a roughness model for turbulent flow in tubes internally roughened with three-dimensional distributed roughness elements, such as sandgrains, spheres, hemispheres, and cones. The second phase is concerned with devising and validating methods for the prediction of friction factors and Nusselt numbers for turbulent flow in tubes internally roughened with repeated, two-dimensional ribs aligned perpendicular to the flow. The ribs are spaced sufficiently far apart that the leeward-side separated flow reattaches to the wall before again separating in order to negotiate the next rib. This heat-transfer enhancement mechanism is called the separation and reattachment mechanism, after Rabas (1989). This work is limited to rectangular rib shapes.

  5. Heat transfer and pressure drop characteristics of the tube bank fin heat exchanger with fin punched with flow redistributors and curved triangular vortex generators

    NASA Astrophysics Data System (ADS)

    Liu, Song; Jin, Hua; Song, KeWei; Wang, LiangChen; Wu, Xiang; Wang, LiangBi

    2017-04-01

    The heat transfer performance of the tube bank fin heat exchanger is limited by the air-side thermal resistance. Thus, enhancing the air-side heat transfer is an effective method to improve the performance of the heat exchanger. A new fin pattern with flow redistributors and curved triangular vortex generators is experimentally studied in this paper. The effects of the flow redistributors located in front of the tube stagnation point and the curved vortex generators located around the tube on the characteristics of heat transfer and pressure drop are discussed in detail. A performance comparison is also carried out between the fins with and without flow redistributors. The experimental results show that the flow redistributors stamped out from the fin in front of the tube stagnation points can decrease the friction factor at the cost of decreasing the heat transfer performance. Whether the combination of the flow redistributors and the curved vortex generators will present a better heat transfer performance depends on the size of the curved vortex generators. As for the studied two sizes of vortex generators, the heat transfer performance is promoted by the flow redistributors for the fin with larger size of vortex generators and the performance is suppressed by the flow redistributors for the fin with smaller vortex generators.

  6. Laminar flow heat transfer and pressure drop characteristics of power-law fluids inside tubes with varying width twisted tape inserts

    SciTech Connect

    Patil, A.G.

    2000-02-01

    Results of an experimental investigation of heat transfer and flow friction of a generalized power-law fluid in tape generated swirl flow inside a 25.0 mm i.d. circular tube, are presented. In order to reduce excessive pressure drops associated with full width twisted tapes, with less corresponding reduction in heat transfer coefficients, reduced width twisted tapes of widths ranging from 11.0 to 23.8 mm, which are lower than the tube inside diameter are used. Reduced width twisted tape inserts give 18%--56% lower isothermal friction factors than the full width tapes. Uniform wall temperature Nusselt numbers decrease only slightly by 5%--25%, for tape widths of 19.7 and 11.0 mm, respectively. Based on the constant pumping power criterion, the tapes of width 19.7 mm perform more or less like full width tapes. Correlations are presented for isothermal and heating friction factors and Nusselt numbers (under uniform wall temperature condition) for a fully developed laminar swirl flow, which are applicable to full width as well as reduced width twisted tapes, using a modified twist ratio as pitch to width ratio of the tape. The reduced width tapes offer 20%--50% savings in the tape material as compared to the full width tapes.

  7. An investigation of the effects of separating pressure on the efficiency and the reliability of three-circuit combined-cycle power plants with steam reheating

    NASA Astrophysics Data System (ADS)

    Lukyanova, T. S.; Trukhniy, A. D.

    2012-04-01

    The authors discuss the influence of selection of the separating pressure in designing three-circuit combined-cycle power plants (CCPP) with steam reheating on their technical and economical characteristics. The changes occurring in steam flow rates in the circuits, as well as in the efficiency of the waste heat recovery boiler (WHRB), the dryness factor, heat drops, the capacity and the efficiency of the steam turbine cylinders, the efficiency of the steam turbine and the CCPP as a whole, with the changes in the separating pressure, have been analyzed. It has been shown that the optimum separating pressure for the steam-power cycle with subcritical steam conditions ranges from 2.0 to 2.5 MPa.

  8. Does a drop in the bucket make a splash? Assessing the impact of antibiotic use on plants.

    PubMed

    McManus, Patricia S

    2014-06-01

    Antibiotics are applied to plants to prevent bacterial diseases, although the diversity of antibiotics and total amounts used are dwarfed by antibiotic use in animal agriculture. Nevertheless, the release of antibiotics into the open environment during crop treatment draws scrutiny for its potential impact on the global pool of resistance genes. The main use of antibiotics on plants is application of streptomycin to prevent fire blight, a serious disease of apple and pear trees. A series of recent studies identified and quantified antibiotic resistance genes and profiled bacterial communities in apple orchard plots that were or were not sprayed with streptomycin. While the specific objectives and methods varied, the results of these studies suggest that streptomycin application for fire blight control does not influence bacterial community structure or increase the abundance of resistance genes in orchards. Copyright © 2014 Elsevier Ltd. All rights reserved.

  9. Effects of elevated pressure on rate of photosynthesis during plant growth.

    PubMed

    Takeishi, Hiroyuki; Hayashi, Jun; Okazawa, Atsushi; Harada, Kazuo; Hirata, Kazumasa; Kobayashi, Akio; Akamatsu, Fumiteru

    2013-10-20

    The aim of this study is to investigate the effects of an artificially controlled environment, particularly elevated total pressure, on net photosynthesis and respiration during plant growth. Pressure directly affects not only cells and organelles in leaves but also the diffusion coefficients and degrees of solubility of CO2 and O2. In this study, the effects of elevated total pressure on the rates of net photosynthesis and respiration of a model plant, Arabidopsis thaliana, were investigated in a chamber that newly developed in this study to control the total pressure. The results clearly showed that the rate of respiration decreased linearly with increasing total pressure at a high humidity. The rate of respiration decreased linearly with increasing total pressure up to 0.2 MPa, and increased with increasing total pressure from 0.3 to 0.5 MPa at a low humidity. The rate of net photosynthesis decreased linearly with increasing total pressure under a constant partial pressure of CO2 at 40 Pa. On the other hand, the rate of net photosynthesis was clearly increased by up to 1.6-fold with increasing total pressure and partial pressure of CO2.

  10. Effects of vegetative propagule pressure on the establishment of an introduced clonal plant, Hydrocotyle vulgaris.

    PubMed

    Liu, Ruihua; Chen, Qiuwen; Dong, Bicheng; Yu, Feihai

    2014-07-01

    Some introduced clonal plants spread mainly by vegetative (clonal) propagules due to the absence of sexual reproduction in the introduced range. Propagule pressure (i.e. total number of propagules) may affect the establishment and thus invasion success of introduced clonal plants, and such effects may also depend on habitat conditions. A greenhouse experiment with an introduced plant, Hydrocotyle vulgaris was conducted to investigate the role of propagule pressure on its invasion process. High (five ramets) or low (one ramet) propagule pressure was established either in bare soil or in an experimental plant community consisting of four grassland species. H. vulgaris produced more total biomass under high than under low propagule pressure in both habitat conditions. Interestingly, the size of the H. vulgaris individuals was smaller under high than under low propagule pressure in bare soil, whereas it did not differ between the two propagule pressure treatments in the grassland community. The results indicated that high propagule pressure can ensure the successful invasion in either the grass community or bare soil, and the shift in the intraspecific interaction of H. vulgaris from competition in the bare soil to facilitation in the grassland community may be a potential mechanism.

  11. Fire as an evolutionary pressure shaping plant traits.

    PubMed

    Keeley, Jon E; Pausas, Juli G; Rundel, Philip W; Bond, William J; Bradstock, Ross A

    2011-08-01

    Traits, such as resprouting, serotiny and germination by heat and smoke, are adaptive in fire-prone environments. However, plants are not adapted to fire per se but to fire regimes. Species can be threatened when humans alter the regime, often by increasing or decreasing fire frequency. Fire-adaptive traits are potentially the result of different evolutionary pathways. Distinguishing between traits that are adaptations originating in response to fire or exaptations originating in response to other factors might not always be possible. However, fire has been a factor throughout the history of land-plant evolution and is not strictly a Neogene phenomenon. Mesozoic fossils show evidence of fire-adaptive traits and, in some lineages, these might have persisted to the present as fire adaptations.

  12. Investigations of levitated helium drops

    NASA Astrophysics Data System (ADS)

    Whitaker, Dwight Lawrence

    1999-11-01

    We report on the development of two systems capable of levitating drops of liquid helium. Helium drops of ˜20 mum have been levitated with the radiation pressure from two counter-propagating Nd:YAG laser beams. Drops are produced with a submerged piezoelectric transducer, and could be held for up to three minutes in our optical trap. Calculations show that Brillouin and Raman scattering of the laser light in the liquid helium produces a negligible rate of evaporation of the drop. Evaporation caused by the enhanced vapor pressure of the curved drop surfaces appears to be a significant effect limiting the drop lifetimes. Helium drops as large as 2 cm in diameter have been suspended in the earth's gravitational field with a magnetic field. A commercial superconducting solenoid provides the necessary field, field-gradient product required to levitate the drops. Drops are cooled to 0.5 K with a helium-3 refrigerator, and can be held in the trap indefinitely. We have found that when two or more drops are levitated in the same magnetic trap, the drops often remain in a state of apparent contact without coalescing. This effect is a result of the evaporation of liquid from between the two drops, and is found to occur only for normal fluid drops. We can induce shape oscillations in charged, levitated drops with an applied ac electric field. We have measured the resonance frequencies and damping rates for the l = 2 mode of oscillation as function of temperature. We have also developed a theory to describe the small amplitude shape oscillations of a He II drop surrounded by its saturated vapor. In our theory, we have considered two sets of boundary conditions---one where the drop does not evaporate and another in which the liquid and vapor are in thermodynamic equilibrium. We have found that both solutions give a frequency that agrees well with experiment, but that the data for the damping rate agree better with the solution without evaporation.

  13. Drop-on-demand sample introduction system coupled with the flowing atmospheric-pressure afterglow for direct molecular analysis of complex liquid microvolume samples.

    PubMed

    Schaper, J Niklas; Pfeuffer, Kevin P; Shelley, Jacob T; Bings, Nicolas H; Hieftje, Gary M

    2012-11-06

    One of the fastest developing fields in analytical spectrochemistry in recent years is ambient desorption/ionization mass spectrometry (ADI-MS). This burgeoning interest has been due to the demonstrated advantages of the method: simple mass spectra, little or no sample preparation, and applicability to samples in the solid, liquid, or gaseous state. One such ADI-MS source, the flowing atmospheric-pressure afterglow (FAPA), is capable of direct analysis of solids just by aiming the source at the solid surface and sampling the produced ions into a mass spectrometer. However, direct introduction of significant volumes of liquid samples into this source has not been possible, as solvent loads can quench the afterglow and, thus, the formation of reagent ions. As a result, the analysis of liquid samples is preferably carried out by analyzing dried residues or by desorbing small amounts of liquid samples directly from the liquid surface. In the former case, reproducibility of sample introduction is crucial if quantitative results are desired. In the present study, introduction of liquid samples as very small droplets helps overcome the issues of sample positioning and reduced levels of solvent intake. A recently developed "drop-on-demand" (DOD) aerosol generator is capable of reproducibly producing very small volumes of liquid (∼17 pL). In this paper, the coupling of FAPA-MS and DOD is reported and applications are suggested. Analytes representing different classes of substances were tested and limits of detections were determined. Matrix tolerance was investigated for drugs of abuse and their metabolites by analyzing raw urine samples and quantification without the use of internal standards. Limits of detection below 2 μg/mL, without sample pretreatment, were obtained.

  14. Power generation plant integrating concentrated solar power receiver and pressurized heat exchanger

    DOEpatents

    Sakadjian, Bartev B; Flynn, Thomas J; Hu, Shengteng; Velazquez-Vargas, Luis G; Maryamchik, Mikhail

    2016-10-04

    A power plant includes a solar receiver heating solid particles, a standpipe receiving solid particles from the solar receiver, a pressurized heat exchanger heating working fluid by heat transfer through direct contact with heated solid particles flowing out of the bottom of the standpipe, and a flow path for solid particles from the bottom of the standpipe into the pressurized heat exchanger that is sealed by a pressure P produced at the bottom of the standpipe by a column of heated solid particles of height H. The flow path may include a silo or surge tank comprising a pressure vessel connected to the bottom of the standpipe, and a non-mechanical valve. The power plant may further include a turbine driven by heated working fluid discharged from the pressurized heat exchanger, and a compressor driven by the turbine.

  15. Pressurized thermal shock evaluation of the Calvert Cliffs Unit 1 Nuclear Power Plant

    SciTech Connect

    Abbott, L

    1985-09-01

    An evaluation of the risk to the Calvert Cliffs Unit 1 nuclear power plant due to pressurized thermal shock (PTS) has been completed by Oak Ridge National Laboratory (ORNL) with the assistance of several other organizations. This evaluation was part of a Nuclear Regulatory Commission program designed to study the PTS risk to three nuclear plants, the other two plants being Oconee Unit 1 and H.B. Robinson Unit 2. The specific objectives of the program were to (1) provide a best estimate of the frequency of a through-the-wall crack in the pressure vessel at each of the three plants, together with the uncertainty in the estimated frequency and its sensitivity to the variables used in the evaluation; (2) determine the dominant overcooling sequences contributing to the estimated frequency and the associated failures in the plant systems or in operator actions; and (3) evaluate the effectiveness of potential corrective measures.

  16. Fluidic origami with embedded pressure dependent multi-stability: a plant inspired innovation

    PubMed Central

    Li, Suyi; Wang, K. W.

    2015-01-01

    Inspired by the impulsive movements in plants, this research investigates the physics of a novel fluidic origami concept for its pressure-dependent multi-stability. In this innovation, fluid-filled tubular cells are synthesized by integrating different Miura-Ori sheets into a three-dimensional topological system, where the internal pressures are strategically controlled similar to the motor cells in plants. Fluidic origami incorporates two crucial physiological features observed in nature: one is distributed, pressurized cellular organization, and the other is embedded multi-stability. For a single fluidic origami cell, two stable folding configurations can coexist due to the nonlinear relationships among folding, crease material deformation and internal volume change. When multiple origami cells are integrated, additional multi-stability characteristics could occur via the interactions between pressurized cells. Changes in the fluid pressure can tailor the existence and shapes of these stable folding configurations. As a result, fluidic origami can switch between being mono-stable, bistable and multi-stable with pressure control, and provide a rapid ‘snap-through’ type of shape change based on the similar principles as in plants. The outcomes of this research could lead to the development of new adaptive materials or structures, and provide insights for future plant physiology studies at the cellular level. PMID:26400197

  17. Fluidic origami with embedded pressure dependent multi-stability: a plant inspired innovation.

    PubMed

    Li, Suyi; Wang, K W

    2015-10-06

    Inspired by the impulsive movements in plants, this research investigates the physics of a novel fluidic origami concept for its pressure-dependent multi-stability. In this innovation, fluid-filled tubular cells are synthesized by integrating different Miura-Ori sheets into a three-dimensional topological system, where the internal pressures are strategically controlled similar to the motor cells in plants. Fluidic origami incorporates two crucial physiological features observed in nature: one is distributed, pressurized cellular organization, and the other is embedded multi-stability. For a single fluidic origami cell, two stable folding configurations can coexist due to the nonlinear relationships among folding, crease material deformation and internal volume change. When multiple origami cells are integrated, additional multi-stability characteristics could occur via the interactions between pressurized cells. Changes in the fluid pressure can tailor the existence and shapes of these stable folding configurations. As a result, fluidic origami can switch between being mono-stable, bistable and multi-stable with pressure control, and provide a rapid 'snap-through' type of shape change based on the similar principles as in plants. The outcomes of this research could lead to the development of new adaptive materials or structures, and provide insights for future plant physiology studies at the cellular level. © 2015 The Author(s).

  18. Features of erosion-corrosion wear in low-pressure evaporators of combined-cycle plant heat-recovery boilers at high void factor values

    NASA Astrophysics Data System (ADS)

    Galetsky, N. S.; Schwarz, A. L.

    2013-12-01

    The features of erosion-corrosion wear (ECW) in a low-pressure evaporator (LPE) combinedcycle plant (CCP) at high void factor values in the heat carrier are considered. It is shown that if the medium pressure in the evaporator is less than 1 MPa and steam quality x ≈ 0.5, the void fraction β is close to 1, at the outlet of the evaporator almost dry saturated steam moves, and the formation of liquid films is excluded. Under these conditions, the wear of the evaporator coil sections has an erosive nature, caused by high velocity steam, carrying the dense particles of corrosion products and large drops of water, previously plucked from the surface of the liquid films.

  19. High-pressure processing as emergent technology for the extraction of bioactive ingredients from plant materials.

    PubMed

    Jun, Xi

    2013-01-01

    High-pressure processing is a food processing technique that has shown great potentials in the food industry. Recently, it was developed to extract bioactive ingredients from plant materials, known as ultrahigh pressure extraction (UPE), taking advantages of time saving, higher extraction yields, fewer impurities in the extraction solution, minimal heat and can avoid thermal degradation on the activity and structure of bioactive components, and so on. This review provides an overview of the developments in the UPE of bioactive ingredients from plant material. Apart from a brief presentation of the theories of UPE and extraction equipment systems, the principal parameters that influence the extraction efficiency to be optimized in the UPE (e.g., solvent, pressure, temperature, extraction time, and the number of cycle) were discussed in detail, and finally the more recent applications of UPE for the extraction of active compounds from plant materials were summarized.

  20. The effect of hydrostatic vs. shock pressure treatment on plant seeds

    NASA Astrophysics Data System (ADS)

    Mustey, Adrian; Leighs, James; Appleby-Thomas, Gareth; Wood, David; Hazael, Rachael; McMillan, Paul; Hazell, Paul

    2013-06-01

    The hydrostatic pressure and shock response of plant seeds have both been previously investigated (primarily driven by an interest in reducing bacterial contamination of crops and the theory of panspermia respectively). However, comparisons have not previously been made between these two methods of applying pressure to plant seeds. Here such a comparison has been undertaken based on the premise that any correlations in such data may provide a route to inform understanding of damage mechanisms in the seeds under test. In this work two varieties of plant seeds were subjected to hydrostatic pressure via a non-end-loaded piston cylinder set-up and shock compression via employment of a 50-mm bore, single stage gas gun using the flyer-plate technique. Results from germination tests of recovered seed samples have been compared and contrasted, and initial conclusions made regarding causes of trends in the resultant data-set.

  1. Characterization of pressurized fluidized bed and pulverized coal fired power plants

    SciTech Connect

    Doss, H.S.; Pietruszkiewicz, J.; Thomas, G.O.; Hamm, J.R.; Bezella, W.A.

    1984-01-01

    This paper presents the major technical and economic characteristics of a steam-cooled and an air-cooled pressurized fluidized bed (PFB) power plant concept along with the characteristics of a pulverized coal fired power plant equipped with an adipic acid enhanced wet-limestone flue gas desulfurization system. The conceptual designs were prepared to satisfy a set of common groundrules that were developed for the study. The power plants are of the grassroots type, located on a generic plant site. The designs incorporate technological advances available for commercialization in the 1990 time frame. The net power outputs of the base case plants, using Illinois No. 6 coal, range from 502 MWe for the pulverized coal fired plant to 554 MWe for the air-cooled PFB plant. The net power plant heat rates vary from 9725 Btu/kWh for the pulverized coal fired plant to 8710 Btu/kWh for the steam-cooled PFB plant. For the economic groundrules set for the study, the pulverized coal fired plant utilizing an advanced flue gas desulfurization concept had the lowest specific capital cost and lowest levelized cost of electricity. However, utility and site specific conditions could materially alter the relative merits of the various concepts in a given utility application.

  2. Selective Pressure along a Latitudinal Gradient Affects Subindividual Variation in Plants

    PubMed Central

    Sobral, Mar; Guitián, José; Guitián, Pablo; Larrinaga, Asier R.

    2013-01-01

    Individual plants produce repeated structures such as leaves, flowers or fruits, which, although belonging to the same genotype, are not phenotypically identical. Such subindividual variation reflects the potential of individual genotypes to vary with micro-environmental conditions. Furthermore, variation in organ traits imposes costs to foraging animals such as time, energy and increased predation risk. Therefore, animals that interact with plants may respond to this variation and affect plant fitness. Thus, phenotypic variation within an individual plant could be, in part, an adaptive trait. Here we investigated this idea and we found that subindividual variation of fruit size of Crataegus monogyna, in different populations throughout the latitudinal gradient in Europe, was explained at some extent by the selective pressures exerted by seed-dispersing birds. These findings support the hypothesis that within-individual variation in plants is an adaptive trait selected by interacting animals which may have important implications for plant evolution. PMID:24069297

  3. Worldwide assessment of steam-generator problems in pressurized-water-reactor nuclear power plants

    SciTech Connect

    Woo, H.H.; Lu, S.C.

    1981-09-15

    Objective is to assess the reliability of steam generators of pressurized water reactor (PWR) power plants in the United States and abroad. The assessment is based on operation experience of both domestic and foreign PWR plants. The approach taken is to collect and review papers and reports available from the literature as well as information obtained by contacting research institutes both here and abroad. This report presents the results of the assessment. It contains a general background of PWR plant operations, plant types, and materials used in PWR plants. A review of the worldwide distribution of PWR plants is also given. The report describes in detail the degradation problems discovered in PWR steam generators: their causes, their impacts on the performance of steam generators, and the actions to mitigate and avoid them. One chapter is devoted to operating experience of PWR steam generators in foreign countries. Another discusses the improvements in future steam generator design.

  4. Water cycle and its management for plant habitats at reduced pressures

    NASA Technical Reports Server (NTRS)

    Rygalov, Vadim Y.; Fowler, Philip A.; Wheeler, Raymond M.; Bucklin, Ray A.

    2004-01-01

    Experimental and mathematical models were developed for describing and testing temperature and humidity parameters for plant production in bioregenerative life support systems. A factor was included for analyzing systems operating at low (10-101.3 kPa) pressure to reduce gas leakage and structural mass (e.g., inflatable greenhouses for space application). The expected close relationship between temperature and relative humidity was observed, along with the importance of heat exchanger coil temperature and air circulation rate. The presence of plants in closed habitats results in increased water flux through the system. Changes in pressure affect gas diffusion rates and surface boundary layers, and change convective transfer capabilities and water evaporation rates. A consistent observation from studies with plants at reduced pressures is increased evapotranspiration rates, even at constant vapor pressure deficits. This suggests that plant water status is a critical factor for managing low-pressure production systems. The approach suggested should help space mission planners design artificial environments in closed habitats.

  5. Water cycle and its management for plant habitats at reduced pressures

    NASA Technical Reports Server (NTRS)

    Rygalov, Vadim Y.; Fowler, Philip A.; Wheeler, Raymond M.; Bucklin, Ray A.

    2004-01-01

    Experimental and mathematical models were developed for describing and testing temperature and humidity parameters for plant production in bioregenerative life support systems. A factor was included for analyzing systems operating at low (10-101.3 kPa) pressure to reduce gas leakage and structural mass (e.g., inflatable greenhouses for space application). The expected close relationship between temperature and relative humidity was observed, along with the importance of heat exchanger coil temperature and air circulation rate. The presence of plants in closed habitats results in increased water flux through the system. Changes in pressure affect gas diffusion rates and surface boundary layers, and change convective transfer capabilities and water evaporation rates. A consistent observation from studies with plants at reduced pressures is increased evapotranspiration rates, even at constant vapor pressure deficits. This suggests that plant water status is a critical factor for managing low-pressure production systems. The approach suggested should help space mission planners design artificial environments in closed habitats.

  6. CFD- and Bernoulli-based pressure drop estimates: A comparison using patient anatomies from heart and aortic valve segmentation of CT images.

    PubMed

    Weese, Jürgen; Lungu, Angela; Peters, Jochen; Weber, Frank M; Waechter-Stehle, Irina; Hose, D Rodney

    2017-06-01

    An aortic valve stenosis is an abnormal narrowing of the aortic valve (AV). It impedes blood flow and is often quantified by the geometric orifice area of the AV (AVA) and the pressure drop (PD). Using the Bernoulli equation, a relation between the PD and the effective orifice area (EOA) represented by the area of the vena contracta (VC) downstream of the AV can be derived. We investigate the relation between the AVA and the EOA using patient anatomies derived from cardiac computed tomography (CT) angiography images and computational fluid dynamic (CFD) simulations. We developed a shape-constrained deformable model for segmenting the AV, the ascending aorta (AA), and the left ventricle (LV) in cardiac CT images. In particular, we designed a structured AV mesh model, trained the model on CT scans, and integrated it with an available model for heart segmentation. The planimetric AVA was determined from the cross-sectional slice with minimum AV opening area. In addition, the AVA was determined as the nonobstructed area along the AV axis by projecting the AV leaflet rims on a plane perpendicular to the AV axis. The flow rate was derived from the LV volume change. Steady-state CFD simulations were performed on the patient anatomies resulting from segmentation. Heart and valve segmentation was used to retrospectively analyze 22 cardiac CT angiography image sequences of patients with noncalcified and (partially) severely calcified tricuspid AVs. Resulting AVAs were in the range of 1-4.5 cm(2) and ejection fractions (EFs) between 20 and 75%. AVA values computed by projection were smaller than those computed by planimetry, and both were strongly correlated (R(2) = 0.995). EOA values computed via the Bernoulli equation from CFD-based PD results were strongly correlated with both AVA values (R(2) = 0.97). EOA values were ∼10% smaller than planimetric AVA values. For EOA values < 2.0 cm(2) , the EOA was up to ∼15% larger than the projected AVA. The presented segmentation

  7. Design of Plant Gas Exchange Experiments in a Variable Pressure Growth Chamber

    NASA Technical Reports Server (NTRS)

    Corey, Kenneth A.

    1996-01-01

    Sustainable human presence in extreme environments such as lunar and martian bases will require bioregenerative components to human life support systems where plants are used for generation of oxygen, food, and water. Reduced atmospheric pressures will be used to minimize mass and engineering requirements. Few studies have assessed the metabolic and developmental responses of plants to reduced pressure and varied oxygen atmospheres. The first tests of hypobaric pressures on plant gas exchange and biomass production at the Johnson Space Center will be initiated in January 1996 in the Variable Pressure Growth Chamber (VPGC), a large, closed plant growth chamber rated for 10.2 psi. Experiments were designed and protocols detailed for two complete growouts each of lettuce and wheat to generate a general database for human life support requirements and to answer questions about plant growth processes in reduced pressure and varied oxygen environments. The central objective of crop growth studies in the VPGC is to determine the influence of reduced pressure and reduced oxygen on the rates of photosynthesis, dark respiration, evapotranspiration and biomass production of lettuce and wheat. Due to the constraint of one experimental unit, internal controls, called pressure transients, will be used to evaluate rates of CO2 uptake, O2 evolution, and H2O generation. Pressure transients will give interpretive power to the results of repeated growouts at both reduced and ambient pressures. Other experiments involve the generation of response functions to partial pressures of O2 and CO2 and to light intensity. Protocol for determining and calculating rates of gas exchange have been detailed. In order to build these databases and implement the necessary treatment combinations in short time periods, specific requirements for gas injections and removals have been defined. A set of system capability checks will include determination of leakage rates conducted prior to the actual crop

  8. The development of the fast-running simulation pressurized water reactor plant analyzer code (NUPAC-1)

    SciTech Connect

    Sasaki, K.; Terashita, N.; Ogino, T. . Central Research Lab.)

    1989-06-01

    This article discusses a pressurized water reactor plant analyzer code (NUPAC-1) has been developed to apply to an operator support system or an advanced training simulator. The simulation code must produce reasonably accurate results as well as fun in a fast mode for realizing functions such as anomaly detection, estimation of unobservable plant internal states, and prediction of plant state trends. The NUPAC-1 code adopts fast computing methods, i.e., the table fitting method of the state variables, time-step control, and calculation control of heat transfer coefficients, in order to attain accuracy and fast-running capability.

  9. Invasion resistance and persistence: established plants win, even with disturbance and high propagule pressure

    Treesearch

    Christopher M. McGlone; Carolyn Hull Sieg; Thomas E. Kolb

    2011-01-01

    Disturbances and propagule pressure are key mechanisms in plant community resistance to invasion, as well as persistence of invasions. Few studies, however, have experimentally tested the interaction of these two mechanisms. We initiated a study in a southwestern ponderosa pine (Pinus ponderosa Laws.)/bunch grass system to determine the susceptibility of remnant native...

  10. Second-Generation Pressurized Fluidized Bed Combustion: Small gas turbine induustrial plant study

    SciTech Connect

    Shenker, J.; Garland, R.; Horazak, D.; Seifert, F.; Wenglarz, R.

    1992-07-01

    Second-Generation Pressurized Fluidized Bed Combustion (PFBC) plants provide a coal-fired, high-efficiency, combined-cycle system for the generation of electricity and steam. The plants use lime-based sorbents in PFB combustors to meet environmental air standards without back-end gas desulfurization equipment. The second-generation system is an improvement over earlier PFBC concepts because it can achieve gas temperatures of 2100[degrees]F and higher for improved cycle efficiency while maintaining the fluidized beds at 1600[degrees]F for enhanced sulfur capture and minimum alkali release. Second-generation PFBC systems are capable of supplying the electric and steam process needs of industrial plants. The basic second-generation system can be applied in different ways to meet a variety of process steam and electrical requirements. To evaluate the potential of these systems in the industrial market, conceptual designs have been developed for six second-generation PFBC plants. These plants cover a range of electrical outputs from 6.3 to 41.5 MWe and steam flows from 46,067 to 442,337 lb/h. Capital and operating costs have been estimated for these six plants and for equivalent (in size) conventional, coal-fired atmospheric fluidized bed combustion cogeneration plants. Economic analyses were conducted to compare the cost of steam for both the second-generation plants and the conventional plants.

  11. Second-Generation Pressurized Fluidized Bed Combustion: Small gas turbine industrial plant study

    SciTech Connect

    Shenker, J.; Garland, R.; Horazak, D.; Seifert, F.; Wenglarz, R.

    1992-07-01

    Second-Generation Pressurized Fluidized Bed Combustion (PFBC) plants provide a coal-fired, high-efficiency, combined-cycle system for the generation of electricity and steam. The plants use lime-based sorbents in PFB combustors to meet environmental air standards without back-end gas desulfurization equipment. The second-generation system is an improvement over earlier PFBC concepts because it can achieve gas temperatures of 2100{degrees}F and higher for improved cycle efficiency while maintaining the fluidized beds at 1600{degrees}F for enhanced sulfur capture and minimum alkali release. Second-generation PFBC systems are capable of supplying the electric and steam process needs of industrial plants. The basic second-generation system can be applied in different ways to meet a variety of process steam and electrical requirements. To evaluate the potential of these systems in the industrial market, conceptual designs have been developed for six second-generation PFBC plants. These plants cover a range of electrical outputs from 6.3 to 41.5 MWe and steam flows from 46,067 to 442,337 lb/h. Capital and operating costs have been estimated for these six plants and for equivalent (in size) conventional, coal-fired atmospheric fluidized bed combustion cogeneration plants. Economic analyses were conducted to compare the cost of steam for both the second-generation plants and the conventional plants.

  12. Exploding Water Drops

    NASA Astrophysics Data System (ADS)

    Reich, Gary

    2016-01-01

    Water has the unusual property that it expands on freezing, so that ice has a specific gravity of 0.92 compared to 1.0 for liquid water. The most familiar demonstration of this property is ice cubes floating in a glass of water. A more dramatic demonstration is the ice bomb shown in Fig. 1. Here a cast iron flask is filled with water and tightly stoppered. The flask is then cooled, either by leaving it outdoors in winter or by immersing it in a cryogenic fluid, until the water freezes. As the water freezes and expands, the pressure inside the flask increases dramatically, eventually becoming sufficient to fracture the metal walls of the enclosure. A related, but much less familiar, phenomenon is the explosive fracturing of small water drops upon freezing. That water drops can fracture in this way has been known for many years, and the phenomenon has been described in detail in the atmospheric sciences literature, where it is seen as relevant to the freezing of raindrops as they fall through cold air. Carefully controlled experiments have been done documenting how the character and frequency of fracture is affected by such variables as drop size, rate of cooling, chemistry of dissolved gases, etc. Here I describe instead a simple demonstration of fracture suitable for video analysis and appropriate for study at the introductory physics level. Readers may also be interested in other characteristics of freezing and fragmenting water drops, for example, charge separation upon fracture and the appearance of spikes and bulges on the surface.

  13. Role of turgor pressure and solute transport in plant cell growth: Progress report

    SciTech Connect

    Cosgrove, D.J.

    1987-10-15

    Plant cell expansion requires coordinationion of three distinct processes: wall relaxation and synthesis, water uptake, and solute uptake. Wall relaxation reduces cell turgor pressure and thereby generates the reduced water for water potential needed uptake. Our studies with pea (Pisum sativum L.) and soybean (Glycine max Merr.) seedlings have shown that water uptake is rapid and is not a major control point for growth. Our current focus is on the processes of wall relaxation and solute transport, and how they are influenced by water stress. One major goal of this project is to examine in detail the dependence of wall yielding on turgor pressure. This is being done by detailed measurements of wall relaxation in living cells, using a computer-assisted pressure microprobe and the new pressure-block technique. Our pressure-block results indicate that wall relaxation is more dynamic than expected. Rapid changes in wall yielding appear to compensate for minor fluctuations in cell turgor pressure, thus maintaining stable growth rates. A second major goal of this project is to determine the interrelationship between cell expansion and solute transport into expanding cells. We will selectively block either cell expansion or solute transport, and measure the effect of such blockage on the unblocked process. A third goal is to examine the basis for reduced cell expansion when plants are water stressed. Our results indicate that growth is retarded in part because of reduced turgor pressure, and in part because of reduced cell wall relaxation. The alteration in wall relaxation will be examined by in-vivo relaxation methods. Thus studies will provide insight into the basic cellular and physical processes controlling plant growth, and how they are perturbed by water stress. 8 refs., 1 fig.

  14. Pressure and Flow Relations in Vascular Bundles of the Tomato Plant

    PubMed Central

    Dimond, A. E.

    1966-01-01

    In the tomato plant water flows through primary xylem in accordance with Poiseuille's law. This relation and the analogy between Poiseuille's and Ohm's law were employed to calculate rates of flow and differences in pressure within vascular bundles when transpiration rates from individual leaves were known. The resistance of vascular bundles to flow was calculated from a modification of Poiseuille's law and from measurements of vessels in all bundles. The rates of flow in all bundles were derived from a set of simultaneous linear equations of flow, written to correspond with the nature of the vascular network. Values of the difference in pressure associated with flow in bundles were derived from resistances and flow rates in individual bundles. These agreed substantially with values observed in a comparable plant. In large bundles, vessels occur in a frequency distribution that is approximately normal with respect either to the logarithms of their radii or to the fourth power of their radii. The largest vessels in a bundle transport most of the water when they are functioning. The tomato plant contains 2 types of vascular bundle. The large bundles of the stem form a network by joining above each node in combinations of 2 at a time. The small bundles of the stem and petiolar bundles are independent of other bundles from their origins at junctions to their termini. The small bundles offer high resistance to flow, whereas the resistance of large bundles is low. The average conductance of large bundles decreases from the base to the apex of the stem. That of small vascular bundles remains low and more or less constant throughout the plant. Only a small difference in pressure is required to maintain flow in large bundles. For lower leaves, the driving pressure required to move water to the base of a petiole is considerably less than that which moves water through petioles. The difference in pressure that maintains flow increases steadily for successively higher nodes

  15. Quantifying hydrostatic pressure in plant cells by using indentation with an atomic force microscope.

    PubMed

    Beauzamy, Léna; Derr, Julien; Boudaoud, Arezki

    2015-05-19

    Plant cell growth depends on a delicate balance between an inner drive-the hydrostatic pressure known as turgor-and an outer restraint-the polymeric wall that surrounds a cell. The classical technique to measure turgor in a single cell, the pressure probe, is intrusive and cannot be applied to small cells. In order to overcome these limitations, we developed a method that combines quantification of topography, nanoindentation force measurements, and an interpretation using a published mechanical model for the pointlike loading of thin elastic shells. We used atomic force microscopy to estimate the elastic properties of the cell wall and turgor pressure from a single force-depth curve. We applied this method to onion epidermal peels and quantified the response to changes in osmolality of the bathing solution. Overall our approach is accessible and enables a straightforward estimation of the hydrostatic pressure inside a walled cell. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

  16. Quantifying Hydrostatic Pressure in Plant Cells by Using Indentation with an Atomic Force Microscope

    PubMed Central

    Beauzamy, Léna; Derr, Julien; Boudaoud, Arezki

    2015-01-01

    Plant cell growth depends on a delicate balance between an inner drive—the hydrostatic pressure known as turgor—and an outer restraint—the polymeric wall that surrounds a cell. The classical technique to measure turgor in a single cell, the pressure probe, is intrusive and cannot be applied to small cells. In order to overcome these limitations, we developed a method that combines quantification of topography, nanoindentation force measurements, and an interpretation using a published mechanical model for the pointlike loading of thin elastic shells. We used atomic force microscopy to estimate the elastic properties of the cell wall and turgor pressure from a single force-depth curve. We applied this method to onion epidermal peels and quantified the response to changes in osmolality of the bathing solution. Overall our approach is accessible and enables a straightforward estimation of the hydrostatic pressure inside a walled cell. PMID:25992723

  17. The effect of hydrostatic vs. shock pressure treatment of plant seeds

    NASA Astrophysics Data System (ADS)

    Mustey, A.; Leighs, J. A.; Appleby-Thomas, G. J.; Wood, D. C.; Hazael, R.; McMillan, P. F.; Hazell, P. J.

    2014-05-01

    The hydrostatic pressure and shock response of plant seeds has been investigated antecedently, primarily driven by interest in reducing bacterial contamination of crops and the theory of panspermia, respectively. However, comparisons have not previously been made between these two methods ofapplying pressure to plant seeds. Here such a comparison has been undertaken based on the premise that any correlations in collected data may provide a route to inform understanding of damage mechanisms in the seeds under test. In this work two varieties of plant seeds were subjected to hydrostatic pressure via a non-end-loaded piston cylinder setup and shock compression via employment of a 50 mm bore, single stage gas gun using the flyer plate technique. Results from germination tests of recovered seed samples have been compared and contrasted, and initial conclusions made regarding causes of trends in the resultant data-set. Data collected has shown that cress seeds are extremely resilient to static loading, whereas the difference in the two forms of loading is negligible for lettuce seeds. Germination time has been seen to extend dramatically following static loading of cress seeds to greater than 0.4 GPa. In addition, the cut-off pressure previously seen to cause 0% germination in dynamic experiments performed on cress seeds has now also been seen in lettuce seeds.

  18. Effect of very high pressure on life of plants and animals

    NASA Astrophysics Data System (ADS)

    Ono, F.; Mori, Y.; Sougawa, M.; Takarabe, K.; Hada, Y.; Nishihira, N.; Motose, H.; Saigusa, M.; Matsushima, Y.; Yamazaki, D.; Ito, E.; Saini, N. L.

    2012-07-01

    We studied the tolerance of living organisms, such as a small animal (Milnesium tardigradum), a small crustacean (Artemia), non-vascular plants or moss (Ptichomitrium and Venturiella), and a vascular plant (Trifolium) to the extremely high hydrostatic pressure of 7.5 GPa. It turned out that most of the high pressure exposed seeds of white clover were alive. Those exposed to 7.5 GPa for up to 1 day and seeded on agar germinated roots. Those exposed for up to 1 hour and seeded on soil germinated stems and leaves. Considering the fact that proteins begins to unfold around 0.3 GPa, it seems difficult to understand that all the living samples which have been investigated can survive after exposure to 7.5 GPa.

  19. A survey of repair practices for nuclear power plant containment metallic pressure boundaries

    SciTech Connect

    Oland, C.B.; Naus, D.J.

    1998-05-01

    The Nuclear Regulatory Commission has initiated a program at the Oak Ridge National Laboratory to provide assistance in their assessment of the effects of potential degradation on the structural integrity and leaktightness of metal containment vessels and steel liners of concrete containments in nuclear power plants. One of the program objectives is to identify repair practices for restoring metallic containment pressure boundary components that have been damaged or degraded in service. This report presents issues associated with inservice condition assessments and continued service evaluations and identifies the rules and requirements for the repair and replacement of nonconforming containment pressure boundary components by welding or metal removal. Discussion topics include base and welding materials, welding procedure and performance qualifications, inspection techniques, testing methods, acceptance criteria, and documentation requirements necessary for making acceptable repairs and replacements so that the plant can be returned to a safe operating condition.

  20. Static Magnetowetting of Ferrofluid Drops.

    PubMed

    Rigoni, Carlo; Pierno, Matteo; Mistura, Giampaolo; Talbot, Delphine; Massart, René; Bacri, Jean-Claude; Abou-Hassan, Ali

    2016-08-02

    We report results of a comprehensive study of the wetting properties of sessile drops of ferrofluid water solutions at various concentrations deposited on flat substrates and subjected to the action of permanent magnets of different sizes and strengths. The amplitude and the gradient of the magnetic field experienced by the ferrofluid are changed by varying the magnets and their distance to the surface. Magnetic forces up to 100 times the gravitational one and magnetic gradients up to 1 T/cm are achieved. A rich phenomenology is observed, ranging from flattened drops caused by the magnetic attraction to drops extended normally to the substrate because of the normal traction of the magnetic field. We find that the former effect can be conveniently described in terms of an effective Bond number that compares the effective drop attraction with the capillary force, whereas the drop's vertical elongation is effectively expressed by a dimensionless number S, which compares the pressure jump at the ferrofluid interface because of the magnetization with the capillary pressure.

  1. Tandem High-pressure Freezing and Quick Freeze Substitution of Plant Tissues for Transmission Electron Microscopy

    PubMed Central

    Bobik, Krzysztof; Dunlap, John R.; Burch-Smith, Tessa M.

    2014-01-01

    Since the 1940s transmission electron microscopy (TEM) has been providing biologists with ultra-high resolution images of biological materials. Yet, because of laborious and time-consuming protocols that also demand experience in preparation of artifact-free samples, TEM is not considered a user-friendly technique. Traditional sample preparation for TEM used chemical fixatives to preserve cellular structures. High-pressure freezing is the cryofixation of biological samples under high pressures to produce very fast cooling rates, thereby restricting ice formation, which is detrimental to the integrity of cellular ultrastructure. High-pressure freezing and freeze substitution are currently the methods of choice for producing the highest quality morphology in resin sections for TEM. These methods minimize the artifacts normally associated with conventional processing for TEM of thin sections. After cryofixation the frozen water in the sample is replaced with liquid organic solvent at low temperatures, a process called freeze substitution. Freeze substitution is typically carried out over several days in dedicated, costly equipment. A recent innovation allows the process to be completed in three hours, instead of the usual two days. This is typically followed by several more days of sample preparation that includes infiltration and embedding in epoxy resins before sectioning. Here we present a protocol combining high-pressure freezing and quick freeze substitution that enables plant sample fixation to be accomplished within hours. The protocol can readily be adapted for working with other tissues or organisms. Plant tissues are of special concern because of the presence of aerated spaces and water-filled vacuoles that impede ice-free freezing of water. In addition, the process of chemical fixation is especially long in plants due to cell walls impeding the penetration of the chemicals to deep within the tissues. Plant tissues are therefore particularly challenging, but

  2. Tandem high-pressure freezing and quick freeze substitution of plant tissues for transmission electron microscopy.

    PubMed

    Bobik, Krzysztof; Dunlap, John R; Burch-Smith, Tessa M

    2014-10-13

    Since the 1940s transmission electron microscopy (TEM) has been providing biologists with ultra-high resolution images of biological materials. Yet, because of laborious and time-consuming protocols that also demand experience in preparation of artifact-free samples, TEM is not considered a user-friendly technique. Traditional sample preparation for TEM used chemical fixatives to preserve cellular structures. High-pressure freezing is the cryofixation of biological samples under high pressures to produce very fast cooling rates, thereby restricting ice formation, which is detrimental to the integrity of cellular ultrastructure. High-pressure freezing and freeze substitution are currently the methods of choice for producing the highest quality morphology in resin sections for TEM. These methods minimize the artifacts normally associated with conventional processing for TEM of thin sections. After cryofixation the frozen water in the sample is replaced with liquid organic solvent at low temperatures, a process called freeze substitution. Freeze substitution is typically carried out over several days in dedicated, costly equipment. A recent innovation allows the process to be completed in three hours, instead of the usual two days. This is typically followed by several more days of sample preparation that includes infiltration and embedding in epoxy resins before sectioning. Here we present a protocol combining high-pressure freezing and quick freeze substitution that enables plant sample fixation to be accomplished within hours. The protocol can readily be adapted for working with other tissues or organisms. Plant tissues are of special concern because of the presence of aerated spaces and water-filled vacuoles that impede ice-free freezing of water. In addition, the process of chemical fixation is especially long in plants due to cell walls impeding the penetration of the chemicals to deep within the tissues. Plant tissues are therefore particularly challenging, but

  3. Nurse plants, tree saplings and grazing pressure: changes in facilitation along a biotic environmental gradient.

    PubMed

    Smit, Christian; Vandenberghe, Charlotte; den Ouden, Jan; Müller-Schärer, Heinz

    2007-05-01

    Current conceptual models predict that an increase in stress shifts interactions between plants from competitive to facilitative; hence, facilitation is expected to gain in ecological importance with increasing stress. Little is known about how facilitative interactions between plants change with increasing biotic stress, such as that incurred by consumer pressure or herbivory (i.e. disturbance sensu Grime). In grazed ecosystems, the presence of unpalatable plants is reported to protect tree saplings against cattle grazing and enhance tree establishment. In accordance with current conceptual facilitation-stress models, we hypothesised a positive relationship between facilitation and grazing pressure. We tested this hypothesis in a field experiment in which tree saplings of four different species (deciduous Fagus sylvatica, Acer pseudoplatanus and coniferous Abies alba, Picea abies) were planted either inside or outside of the canopy of the spiny nurse shrub Rosa rubiginosa in enclosures differing in grazing pressure (low and high) and in exclosures. During one grazing season we followed the survival of the different tree saplings and the level of browsing on these; we also estimated browsing damage to the nurse shrubs. Shrub damage was highest at the higher grazing pressure. Correspondingly, browsing increased and survival decreased in saplings located inside the canopy of the shrubs at the high grazing pressure compared to the low grazing pressure. Saplings of both deciduous species showed a higher survival than the evergreens, while sapling browsing did not differ between species. The relative facilitation of sapling browsing and sapling survival - i.e. the difference between saplings inside and outside the shrub canopy - decreased at high grazing pressure as the facilitative species became less protective. Interestingly, these findings do not agree with current conceptual facilitation-stress models predicting increasing facilitation with abiotic stress. We used

  4. Injector Element which Maintains a Constant Mean Spray Angle and Optimum Pressure Drop During Throttling by Varying the Geometry of Tangential Inlets

    NASA Technical Reports Server (NTRS)

    Trinh, Huu P. (Inventor); Myers, William Neill (Inventor)

    2014-01-01

    A method for determining the optimum inlet geometry of a liquid rocket engine swirl injector includes obtaining a throttleable level phase value, volume flow rate, chamber pressure, liquid propellant density, inlet injector pressure, desired target spray angle and desired target optimum delta pressure value between an inlet and a chamber for a plurality of engine stages. The tangential inlet area for each throttleable stage is calculated. The correlation between the tangential inlet areas and delta pressure values is used to calculate the spring displacement and variable inlet geometry. An injector designed using the method includes a plurality of geometrically calculated tangential inlets in an injection tube; an injection tube cap with a plurality of inlet slots slidably engages the injection tube. A pressure differential across the injector element causes the cap to slide along the injection tube and variably align the inlet slots with the tangential inlets.

  5. Behavior of plant plasma membranes under hydrostatic pressure as monitored by fluorescent environment-sensitive probes.

    PubMed

    Roche, Yann; Klymchenko, Andrey S; Gerbeau-Pissot, Patricia; Gervais, Patrick; Mély, Yves; Simon-Plas, Françoise; Perrier-Cornet, Jean-Marie

    2010-08-01

    We monitored the behavior of plasma membrane (PM) isolated from tobacco cells (BY-2) under hydrostatic pressures up to 3.5kbar at 30 degrees C, by steady-state fluorescence spectroscopy using the newly introduced environment-sensitive probe F2N12S and also Laurdan and di-4-ANEPPDHQ. The consequences of sterol depletion by methyl-beta-cyclodextrin were also studied. We found that application of hydrostatic pressure led to a marked decrease of hydration as probed by F2N12S and to an increase of the generalized polarization excitation (GPex) of Laurdan. We observed that the hydration effect of sterol depletion was maximal between 1 and 1.5 kbar but was much less important at higher pressures (above 2 kbar) where both parameters reached a plateau value. The presence of a highly dehydrated gel state, insensitive to the sterol content, was thus proposed above 2.5 kbar. However, the F2N12S polarity parameter and the di-4-ANEPPDHQ intensity ratio showed strong effect on sterol depletion, even at very high pressures (2.5-3.5 kbar), and supported the ability of sterols to modify the electrostatic properties of membrane, notably its dipole potential, in a highly dehydrated gel phase. We thus suggested that BY-2 PM undergoes a complex phase behavior in response to the hydrostatic pressure and we also emphasized the role of phytosterols to regulate the effects of high hydrostatic pressure on plant PM.

  6. Interactions between abiotic constraint, propagule pressure, and biotic resistance regulate plant invasion.

    PubMed

    Byun, Chaeho; de Blois, Sylvie; Brisson, Jacques

    2015-05-01

    With multiple species introductions and rapid global changes, there is a need for comprehensive invasion models that can predict community responses. Evidence suggests that abiotic constraint, propagule pressure, and biotic resistance of resident species each determine plant invasion success, yet their interactions are rarely tested. To understand these interactions, we conducted community assembly experiments simulating situations in which seeds of the invasive grass species Phragmites australis (Poaceae) land on bare soil along with seeds of resident wetland plant species. We used structural equation models to measure both direct abiotic constraint (here moist vs. flooded conditions) on invasion success and indirect constraint on the abundance and, therefore, biotic resistance of resident plant species. We also evaluated how propagule supply of P. australis interacts with the biotic resistance of resident species during invasion. We observed that flooding always directly reduced invasion success but had a synergistic or antagonistic effect on biotic resistance depending on the resident species involved. Biotic resistance of the most diverse resident species mixture remained strong even when abiotic conditions changed. Biotic resistance was also extremely effective under low propagule pressure of the invader. Moreover, the presence of a dense resident plant cover appeared to lower the threshold at which invasion success became stable even when propagule supply increased. Our study not only provides an analytical framework to quantify the effect of multiple interactions relevant to community assembly and species invasion, but it also proposes guidelines for innovative invasion management strategies based on a sound understanding of ecological processes.

  7. [Recovery of CO from an ammonia plant tail gas with pressure swing adsorption process].

    PubMed

    Yi, Hong-hong; Ning, Ping; Hao, Ji-ming; Yang, Hao

    2004-09-01

    Ammonia plant tail gas is an important CO source for C1 chemistry if an efficient separation/purification technology is available. Presented is pressure swing adsorption using a home made catalyst PU1 for recovery of CO from ammonia plant tail gas. A performance comparison of PU1 with a commercial zeolite was also presented. The pilot plant experiments were carried out in an intermission one-bed PSA unit with ammonia plant tail gas and a feed flow rate of 0.2-0.8 m3/h. The purity and recovery of CO was studied under various operating conditions. The operating conditions for the process were optimized and an optimum cyclic sequence of operation steps was proposed. A good performance of PU1 in the process was experimentally demonstrated. Product gas with a CO purity over 98% could be produced at a CO recovery of 75% for a feed gas CO concentration of 30% and gas pressure of 0.3 MPa.

  8. Coalescence of a Drop inside another Drop

    NASA Astrophysics Data System (ADS)

    Mugundhan, Vivek; Jian, Zhen; Yang, Fan; Li, Erqiang; Thoroddsen, Sigurdur

    2016-11-01

    Coalescence dynamics of a pendent drop sitting inside another drop, has been studied experimentally and in numerical simulations. Using an in-house fabricated composite micro-nozzle, a smaller salt-water drop is introduced inside a larger oil drop which is pendent in a tank containing the same liquid as the inner drop. On touching the surface of outer drop, the inner drop coalesces with the surrounding liquid forming a vortex ring, which grows in time to form a mushroom-like structure. The initial dynamics at the first bridge opening up is quantified using Particle Image Velocimetry (PIV), while matching the refractive index of the two liquids. The phenomenon is also numerically simulated using the open-source code Gerris. The problem is fully governed by two non-dimensional parameters: the Ohnesorge number and the diameter ratios of the two drops. The validated numerical model is used to better understand the dynamics of the phenomenon. In some cases a coalescence cascade is observed with liquid draining intermittently and the inner drop reducing in size.

  9. Role of turgor pressure and solute transport in plant cell growth: Progress report

    SciTech Connect

    Cosgrove, D.J.

    1988-10-20

    Plant cell expansion involves simultaneous water absorption, solute uptake, and wall relaxation and synthesis. Our studies have shown that water absorption by the growing stems of pea (Pisum sativum L.) and other young seedlings is fast and is regulated primarily by wall yielding, which generates the lower water potential necessary for water absorption. Our current focus is on the nature of wall yielding, its dependence on cell turgor pressure, and the mechanism by which cell turgor is maintained in expanding cells. We have developed new relaxation methods to study wall yielding. With the pressure-probe technique we find that wall yielding in excised growing tissues is proportional to cell turgor pressure and exhibits a definite yield threshold. With the pressure-block method we can measure relaxation in intact growing tissues and find that such tissues show more complicated growth and relaxation responses than excised ones. Rapid feedback-regulation of growth is apparent from the pressure-block experiments. With these methods we have examined how drought-stress, light and growth retardants modulate stem elongation. The last two agents acts exclusively on cell wall yielding properties. With droughted pea plants, inhibition is partly through reduced cell turgor pressure and partly through reduced wall relaxation. Drought appears to alter feedback-regulation of cell expansion. Experiments are currently underway to characterize such regulation. In a related line of study we find close correspondence between rates of solute uptake from the phloem and rates of cell expansion. Work is underway to determine the nature of such coupling. 3 refs., 4 figs.

  10. Nanosize-induced drastic drop in equilibrium hydrogen pressure for hydride formation and structural stabilization in Pd-Rh solid-solution alloys.

    PubMed

    Kobayashi, Hirokazu; Morita, Hitoshi; Yamauchi, Miho; Ikeda, Ryuichi; Kitagawa, Hiroshi; Kubota, Yoshiki; Kato, Kenichi; Takata, Masaki; Toh, Shoichi; Matsumura, Syo

    2012-08-01

    We have synthesized and characterized homogeneous solid-solution alloy nanoparticles of Pd and Rh, which are immiscible with each other in the equilibrium bulk state at around room temperature. The Pd-Rh alloy nanoparticles can absorb hydrogen at ambient pressure and the hydrogen pressure of Pd-Rh alloys for hydrogen storage is dramatically decreased by more than 4 orders of magnitude from the corresponding pressure in the metastable bulk state. The solid-solution state is still maintained in the nanoparticles even after hydrogen absorption/desorption, in contrast to the metastable bulks which are separated into Pd and Rh during the process.

  11. Analyses of High Pressure Molten Debris Dispersion for a Typical PWR Plant

    SciTech Connect

    Osamu KAawabata; Mitsuhiro Kajimoto

    2006-07-01

    In such severe core damage accident, as small LOCAs with no ECCS injection or station blackout, in which the primary reactor system remains pressurized during core melt down, certain modes of vessel failure would lead to a high pressure ejection of molten core material. In case of a local failure of the lower head, the molten materials would initially be ejected into the cavity beneath the pressure vessel may subsequently be swept out from the cavity to the containment atmosphere and it might cause the early containment failure by direct contact of containment steel liner with core debris. When the contribution of a high-pressure scenario in a core damage frequency increases, early conditional containment failure probability may become large. In the present study, the verification analysis of PHOENICS code and the combining analysis with MELCOR and PHOENICS codes were performed to examine the debris dispersion behavior during high pressure melt ejection. The PHOENICS code which can treat thermal hydraulic phenomena, was applied to the verification analysis for melt dispersion experiments conducted by the Purdue university in the United States. A low pressure melt dispersion experiment at initial pressure 1.4 MPas used metal woods as a molten material was simulated. The analytical results with molten debris dispersion mostly from the model reactor cavity compartment showed an agreement with the experimental result, but the analysis result of a volumetric median diameter of the airborne debris droplets was estimated about 1.5 times of the experimental result. The injection rates of molten debris and steam after reactor vessel failure for a typical PWR plant were analyzed using the MELCOR code. In addition, PHOENICS was applied to a 3D analysis for debris dispersion with low primary pressure at the reactor vessel failure. The analysis result showed that almost all the molten debris were dispersed from the reactor vessel cavity compartment by about 45 seconds after the

  12. Effects of environmental parameters and irrigation on the turgor pressure of banana plants measured using the non-invasive, online monitoring leaf patch clamp pressure probe.

    PubMed

    Zimmermann, U; Rüger, S; Shapira, O; Westhoff, M; Wegner, L H; Reuss, R; Gessner, P; Zimmermann, G; Israeli, Y; Zhou, A; Schwartz, A; Bamberg, E; Zimmermann, D

    2010-05-01

    Turgor pressure provides a sensitive indicator for irrigation scheduling. Leaf turgor pressure of Musa acuminate was measured by using the so-called leaf patch clamp pressure probe, i.e. by application of an external, magnetically generated and constantly retained clamp pressure to a leaf patch and determination of the attenuated output pressure P(p) that is highly correlated with the turgor pressure. Real-time recording of P(p) values was made using wireless telemetric transmitters, which send the data to a receiver base station where data are logged and transferred to a GPRS modem linked to an Internet server. Probes functioned over several months under field and laboratory conditions without damage to the leaf patch. Measurements showed that the magnetic-based probe could monitor very sensitively changes in turgor pressure induced by changes in microclimate (temperature, relative humidity, irradiation and wind) and irrigation. Irrigation effects could clearly be distinguished from environmental effects. Interestingly, oscillations in stomatal aperture, which occurred frequently below turgor pressures of 100 kPa towards noon at high transpiration or at high wind speed, were reflected in the P(p) values. The period of pressure oscillations was comparable with the period of oscillations in transpiration and photosynthesis. Multiple probe readings on individual leaves and/or on several leaves over the entire height of the plants further emphasised the great impact of this non-invasive turgor pressure sensor system for elucidating the dynamics of short- and long-distance water transport in higher plants.

  13. Effects of EHD on heat transfer enhancement and pressure drop during two-phase condensation of pure R-134a at high mass flux in a horizontal micro-fin tube

    SciTech Connect

    Laohalertdecha, Suriyan; Wongwises, Somchai

    2006-07-15

    Effects of electrohydrodynamic (EHD) on the two-phase heat transfer enhancement and pressure drop of pure R-134a condensing inside a horizontal micro-fin tube are experimentally investigated. The test section is a 2.5m long counter flow tube-in-tube heat exchanger with refrigerant flowing in the inner tube and cooling water flowing in the annulus. The inner tube is made from micro-fin horizontal copper tubing of 9.52mm outer diameter. The electrode is made from cylindrical stainless steel of 1.47mm diameter. Positive high voltage is supplied to the electrode wire, with the micro-fin tube grounded. In the presence of the electrode, a maximum heat transfer enhancement of 1.15 is obtained at a heat flux of 10kW/m{sup 2}, mass flux of 200kg/m{sup 2}s and saturation temperature of 40{sup o}C, while the application of an EHD voltage of 2.5kV only slightly increases the pressure drop. New correlations of the experimental data based on the data gathered during this work for predicting the condensation heat transfer coefficients are proposed for practical application. (author)

  14. Experimental investigation of heat transfer and pressure drop characteristics of non-Newtonian nanofluids flowing in the shell-side of a helical baffle heat exchanger with low-finned tubes

    NASA Astrophysics Data System (ADS)

    Tan, Yunkai; He, Zhenbin; Xu, Tao; Fang, Xiaoming; Gao, Xuenong; Zhang, Zhengguo

    2017-09-01

    An aqueous solution of Xanthan Gum (XG) at a weight fraction as high as 0.2% was used as the base liquid, the stable MWCNTs-dispersed non-Newtonian nanofluids at different weight factions of MWCNTs was prepared. The base fluid and all nanofluids show pseudoplastic (shear-thinning) rheological behavior. Experiments were performed to compare the shell-side forced convective heat transfer coefficient and pressure drop of non-Newtonian nanofluids to those of non-Newtonian base fluid in an integrally helical baffle heat exchanger with low-finned tubes. The experimental results showed that the enhancement of the convective heat transfer coefficient increases with an increase in the Peclet number and the nanoparticle concentration. For nanofluids with 1.0, 0.5 and 0.2 wt% of multi-walled carbon nanotubes (MWCNTs), the heat transfer coefficients respectively augmented by 24.3, 13.2 and 4.7% on average and the pressure drops become larger than those of the base fluid. The comprehensive thermal performance factor is higher than one and increases with an increasing weight fraction of MWCNTs. A remarkable heat transfer enhancement in the shell side of helical baffle heat exchanger with low-finned tubes can be obtained by adding MWCNTs into XG aqueous solution based on thermal resistance analysis. New correlations have been suggested for the shell-side friction coefficient and the Nusselt numbers of non-Newtonian nanofluids and give very good agreement with experimental data.

  15. Electrohydrodynamics of a viscous drop with inertia.

    PubMed

    Nganguia, H; Young, Y-N; Layton, A T; Lai, M-C; Hu, W-F

    2016-05-01

    Most of the existing numerical and theoretical investigations on the electrohydrodynamics of a viscous drop have focused on the creeping Stokes flow regime, where nonlinear inertia effects are neglected. In this work we study the inertia effects on the electrodeformation of a viscous drop under a DC electric field using a novel second-order immersed interface method. The inertia effects are quantified by the Ohnesorge number Oh, and the electric field is characterized by an electric capillary number Ca_{E}. Below the critical Ca_{E}, small to moderate electric field strength gives rise to steady equilibrium drop shapes. We found that, at a fixed Ca_{E}, inertia effects induce larger deformation for an oblate drop than a prolate drop, consistent with previous results in the literature. Moreover, our simulations results indicate that inertia effects on the equilibrium drop deformation are dictated by the direction of normal electric stress on the drop interface: Larger drop deformation is found when the normal electric stress points outward, and smaller drop deformation is found otherwise. To our knowledge, such inertia effects on the equilibrium drop deformation has not been reported in the literature. Above the critical Ca_{E}, no steady equilibrium drop deformation can be found, and often the drop breaks up into a number of daughter droplets. In particular, our Navier-Stokes simulations show that, for the parameters we use, (1) daughter droplets are larger in the presence of inertia, (2) the drop deformation evolves more rapidly compared to creeping flow, and (3) complex distribution of electric stresses for drops with inertia effects. Our results suggest that normal electric pressure may be a useful tool in predicting drop pinch-off in oblate deformations.

  16. Sensor for measuring hydrogen partial pressure in parabolic trough power plant expansion tanks

    NASA Astrophysics Data System (ADS)

    Glatzmaier, Greg C.; Cooney, Daniel A.

    2017-06-01

    The National Renewable Energy Laboratory and Acciona Energy North America are working together to design and implement a process system that provides a permanent solution to the issue of hydrogen buildup at parabolic trough power plants. We are pursuing a method that selectively removes hydrogen from the expansion tanks that serve as reservoirs for the heat transfer fluid (HTF) that circulates in the collector field and power block components. Our modeling shows that removing hydrogen from the expansion tanks at a design rate reduces and maintains dissolved hydrogen in the circulating HTF to a selected target level. Our collaborative work consists of several tasks that are needed to advance this process concept to a development stage, where it is ready for implementation at a commercial power plant. Our main effort is to design and evaluate likely process-unit operations that remove hydrogen from the expansion tanks at a specified rate. Additionally, we designed and demonstrated a method and instrumentation to measure hydrogen partial pressure and concentration in the expansion-tank headspace gas. We measured hydrogen partial pressure in the headspace gas mixture using a palladium-alloy membrane, which is permeable exclusively to hydrogen. The membrane establishes a pure hydrogen gas phase that is in equilibrium with the hydrogen in the gas mixture. We designed and fabricated instrumentation, and demonstrated its effectiveness in measuring hydrogen partial pressures over a range of three orders of magnitude. Our goal is to install this instrument at the Nevada Solar One power plant and to demonstrate its effectiveness in measuring hydrogen levels in the expansion tanks under normal plant operating conditions.

  17. Second-generation pressurized fluidized bed combustion plants for electric power generation

    SciTech Connect

    Robertson, A. ); Bonk, D. ); Horazak, D. ); Newby, R. . Science and Technology Center); Rehmat, A.

    1992-01-01

    In the search for a more efficient, less costly, and more environmentally responsible method for generating electrical power from coal, research and development has turned to advanced pressurized fluidized bed combustion (PFBC) and coal gasification technologies. A logical extension of this work is the second-generation PFBC plant, which incorporates key components of each of these technologies. In this new type of plant, coal is devolatilized/carbonized before it is injected into the PFB combustor bed, and the low-Btu fuel gas produced by this process is burned in a gas turbine topping combustor. By integrating coal carbonization with PFB[degree]C (2300[degree]F) and higher can be achieved. When integrated with a conventional 16.5-MPa gage/538[degree]C/538[degree]C/8.5-kPa Hg (2400- psig/1000[degree]F/1000[degree]F/2.5-in. Hg) steam cycle, a plant electrical generating efficiency of 45-percent is predicted. Concomitant advantages, among others, are a 20-percent lower cost of electricity (compared with a conventional pulverized-coal-fired plant with stack gas scrubbing), reduced stack emissions, and components that can be shipped by barge. This paper presents a conceptual design and economic analysis of Pittsburgh No. 8 and Texas lignite coal-fired 500-MWe second-generation PFB combustion plants.

  18. Instability of development and fractal architecture in dryland plants as an index of grazing pressure

    USGS Publications Warehouse

    Alados, C.L.; Emlen, J.M.; Wachocki, B.; Freeman, D.C.

    1998-01-01

    Developmental instability has been used to monitor the well-being of natural populations exposed to physical, chemical and biological stressors. Here, we use developmental instability to assess the impact of grazing on Chrysothamnus greenii and Seriphidium novumshrubs, and Oryzopsis hymenoidesgrass, common in the arid intermountain west of the U.S.A. Statistical noise in allometric relations was used as an indicator of developmental instability arising from grazing-induced stress. Unpalatable species that are not grazed (Chrysothamnus greenii) or species that are dormant during the winter–spring grazing period (Oryzopsis hymenoides) show lower allometric variability under high grazing pressure. Palatable species (Seriphidium novum) exhibit high developmental instability under low and high grazing pressure. Grazing pressure imposed by presumably co-adapted wild herbivores enhances developmental stability in species habituated to moderate grazing, likeOryzopsis hymenoides, but stresses plants such as Chrysothamnus greenii that prefer disturbed environments. These grazing effects are probably due to the impact grazing has on competitive relationships and not to the direct action of the herbivore on the plants.

  19. Linking Turgor with ABA Biosynthesis: Implications for Stomatal Responses to Vapor Pressure Deficit across Land Plants.

    PubMed

    McAdam, Scott A M; Brodribb, Timothy J

    2016-07-01

    Stomatal responses to changes in vapor pressure deficit (VPD) constitute the predominant form of daytime gas-exchange regulation in plants. Stomatal closure in response to increased VPD is driven by the rapid up-regulation of foliar abscisic acid (ABA) biosynthesis and ABA levels in angiosperms; however, very little is known about the physiological trigger for this increase in ABA biosynthesis at increased VPD Using a novel method of modifying leaf cell turgor by the application of external pressures, we test whether changes in turgor pressure can trigger increases in foliar ABA levels over 20 min, a period of time most relevant to the stomatal response to VPD We found in angiosperm species that the biosynthesis of ABA was triggered by reductions in leaf turgor, and in two species tested, that a higher sensitivity of ABA synthesis to leaf turgor corresponded with a higher stomatal sensitivity to VPD In contrast, representative species from nonflowering plant lineages did not show a rapid turgor-triggered increase in foliar ABA levels, which is consistent with previous studies demonstrating passive stomatal responses to changes in VPD in these lineages. Our method provides a new tool for characterizing the response of stomata to water availability.

  20. Star-shaped oscillations of Leidenfrost drops

    NASA Astrophysics Data System (ADS)

    Ma, Xiaolei; Liétor-Santos, Juan-José; Burton, Justin C.

    2017-03-01

    We experimentally investigate the self-sustained, star-shaped oscillations of Leidenfrost drops. The drops levitate on a cushion of evaporated vapor over a heated, curved surface. We observe modes with n =2 -13 lobes around the drop periphery. We find that the wavelength of the oscillations depends only on the capillary length of the liquid and is independent of the drop radius and substrate temperature. However, the number of observed modes depends sensitively on the liquid viscosity. The dominant frequency of pressure variations in the vapor layer is approximately twice the drop oscillation frequency, consistent with a parametric forcing mechanism. Our results show that the star-shaped oscillations are driven by capillary waves of a characteristic wavelength beneath the drop and that the waves are generated by a large shear stress at the liquid-vapor interface.

  1. Eye Drop Tips

    MedlinePlus

    ... Involved News About Us Donate In This Section Eye Drop Tips en Español email Send this article ... the reach of children. Steps For Putting In Eye Drops: Start by tilting your head backward while ...

  2. Attracting Water Drops

    NASA Image and Video Library

    Astronauts Cady Coleman and Ron Garan perform the Attracting Water Drops experiment from Chabad Hebrew Academy in San Diego, Calif. This research determines if a free-floating water drop can be att...

  3. Nuclear power plant containment metallic pressure boundary materials and plans for collecting and presenting their properties

    SciTech Connect

    Oland, C.B.

    1995-04-01

    A program is being conducted at the Oak Ridge National Laboratory (ORNL to assist the Nuclear Regulatory Commission (NRC)) in their assessment of the effects of degradation (primarily corrosion) on the structural capacity and leaktight integrity of metal containments and steel liners of reinforced concrete structures in nuclear power plants. One of the program objectives is to characterize and quantify manifestations of corrosion on the properties of steels used to construct containment pressure boundary components. This report describes a plan for use in collecting and presenting data and information on ferrous alloys permitted for use in construction of pressure retaining components in concrete and metal containments. Discussions about various degradation mechanisms that could potentially affect the mechanical properties of these materials are also included. Conclusions and recommendations presented in this report will be used to guide the collection of data and information that will be used to prepare a material properties data base for containment steels.

  4. Dosimetry assessments for the reactor pressure vessel and core barrel in UK PWR plant

    SciTech Connect

    Thornton, D.A.; Allen, D.A.; Huggon, A.P.; Picton, D.J.; Robinson, A.T.; Steadman, R.J.; Seren, T.; Lipponen, M.; Kekki, T.

    2011-07-01

    Specimens for the Sizewell B reactor pressure vessel (RPV) inservice steels surveillance program are irradiated inside eight capsules located within the reactor pressure vessel and loaded prior to commissioning. The periodic removal of these capsules and testing of their contents provides material properties data at intervals during the lifetime of the plant. Neutron activation measurements and radiation transport calculations play an essential role in assessing the neutron exposure of the specimens and RPV. Following the most recent withdrawal, seven capsules have now been removed covering nine cycles of reactor operation. This paper summarizes the dosimetry results of the Sizewell B surveillance program obtained to date. In addition to an overview of the calculational methodology it includes a review of the measurements. Finally, it describes an extension of the methodology to provide dosimetry recommendations for the core barrel and briefly discusses the results that were obtained. (authors)

  5. Plant growth modeling at the JSC variable pressure growth chamber - An application of experimental design

    NASA Technical Reports Server (NTRS)

    Miller, Adam M.; Edeen, Marybeth; Sirko, Robert J.

    1992-01-01

    This paper describes the approach and results of an effort to characterize plant growth under various environmental conditions at the Johnson Space Center variable pressure growth chamber. Using a field of applied mathematics and statistics known as design of experiments (DOE), we developed a test plan for varying environmental parameters during a lettuce growth experiment. The test plan was developed using a Box-Behnken approach to DOE. As a result of the experimental runs, we have developed empirical models of both the transpiration process and carbon dioxide assimilation for Waldman's Green lettuce over specified ranges of environmental parameters including carbon dioxide concentration, light intensity, dew-point temperature, and air velocity. This model also predicts transpiration and carbon dioxide assimilation for different ages of the plant canopy.

  6. Plant growth modeling at the JSC variable pressure growth chamber - An application of experimental design

    NASA Technical Reports Server (NTRS)

    Miller, Adam M.; Edeen, Marybeth; Sirko, Robert J.

    1992-01-01

    This paper describes the approach and results of an effort to characterize plant growth under various environmental conditions at the Johnson Space Center variable pressure growth chamber. Using a field of applied mathematics and statistics known as design of experiments (DOE), we developed a test plan for varying environmental parameters during a lettuce growth experiment. The test plan was developed using a Box-Behnken approach to DOE. As a result of the experimental runs, we have developed empirical models of both the transpiration process and carbon dioxide assimilation for Waldman's Green lettuce over specified ranges of environmental parameters including carbon dioxide concentration, light intensity, dew-point temperature, and air velocity. This model also predicts transpiration and carbon dioxide assimilation for different ages of the plant canopy.

  7. Demonstrating Structural Adequacy of Nuclear Power Plant Containment Structures for Beyond Design-Basis Pressure Loadings

    SciTech Connect

    Braverman, J.I.; Morante, R.

    2010-07-18

    ABSTRACT Demonstrating the structural integrity of U.S. nuclear power plant (NPP) containment structures, for beyond design-basis internal pressure loadings, is necessary to satisfy Nuclear Regulatory Commission (NRC) requirements and performance goals. This paper discusses methods for demonstrating the structural adequacy of the containment for beyond design-basis pressure loadings. Three distinct evaluations are addressed: (1) estimating the ultimate pressure capacity of the containment structure (10 CFR 50 and US NRC Standard Review Plan, Section 3.8) ; (2) demonstrating the structural adequacy of the containment subjected to pressure loadings associated with combustible gas generation (10 CFR 52 and 10 CFR 50); and (3) demonstrating the containment structural integrity for severe accidents (10 CFR 52 as well as SECY 90-016, SECY 93-087, and related NRC staff requirements memoranda (SRMs)). The paper describes the technical basis for specific aspects of the methods presented. It also presents examples of past issues identified in licensing activities related to these evaluations.

  8. Strategies to reduce the environmental impact of an aluminium pressure die casting plant: a scenario analysis.

    PubMed

    Neto, Belmira; Kroeze, Carolien; Hordijk, Leen; Costa, Carlos; Pulles, Tinus

    2009-02-01

    This study explores a model (MIKADO) to analyse scenarios for the reduction of the environmental impact of an aluminium die casting plant. Our model calculates the potential to reduce emissions, and the costs associated with implementation of reduction options. In an earlier paper [Neto, B., Kroeze, C., Hordijk, L., Costa, C., 2008. Modelling the environmental impact of an aluminium pressure die casting company and options for control. Environmental Modelling & Software 23 (2) 147-168] we included the model description and explored the model by applying it to a plant in which no reduction options are assumed to be implemented (so-called zero case, reflecting the current practice in the plant). Here, we perform a systematic analysis of reduction options. We analysed seven types of reduction strategies, assuming the simultaneous implementation of different reduction options. These strategies are analysed with respect to their potential to reduce emissions, environmental impact and costs associated with the implementation of options. These strategies were found to differ largely in their potential to reduce the environmental impact of the plant (10-87%), as well as in the costs associated with the implementation of options (-268 to +277keuro/year). We were able to define 11 strategies, reducing the overall environmental impact by more than 50%. Of these, two have net negative costs, indicating that the company may in fact earn money through their implementation.

  9. Eye drop neurology.

    PubMed

    Bennetto, Luke; Guly, Catherine; Ormerod, Ian; Plant, Gordon T

    2014-06-01

    Eye drops can help to diagnose and prevent complications of neurological disorders. Guttae ophthalmicae (eye drops) are generally safe because the drugs rarely achieve significant systemic concentrations, although there are rare exceptions. This article covers contemporary pharmacological pupil testing; how to dilate a pupil safely; common reasons why pupils do not respond to drops; and corneal lubrication to prevent complications of weak eye closure.

  10. Efficiency for unretained solutes in packed column supercritical fluid chromatography II. Experimental results for elution of methane using large pressure drops.

    PubMed

    Xu, Wensheng; Peterson, Dawn L; Schroden, Jonathan J; Poe, Donald P

    2005-06-17

    At near-critical temperatures and pressures, experimental results for elution of methane with neat carbon dioxide on a 150 mm x 2.0 mm I.D. column packed with 5 microm porous silica with a bonded octylsilica stationary phase show much greater efficiency losses than predicted by theory if isothermal conditions are assumed. Experiments with insulated, air- and water-thermostatted columns demonstrate that significant axial and radial temperature gradients are produced by Joule-Thomson cooling of the mobile phase, and that radial temperature gradients can be a major cause of band spreading at low temperatures and pressures. The use of thermal insulation on the column can greatly improve efficiency under these conditions.

  11. The dissipation and risk assessment of 2,4-D sodium, a preharvest anti-fruit-drop plant hormone in bayberries.

    PubMed

    Zhao, Huiyu; Yang, Guiling; Liang, Senmiao; Huang, Qianbin; Wang, Qiang; Dai, Wanze; Zhang, Zhiheng; Wang, Wen; Song, Wen; Cai, Zheng

    2017-09-09

    Preharvest fruit-drop is a challenge to bayberry production. 2,4-D sodium as a commonly used anti-fruit-drop hormone on bayberry can reduce the yield loss caused by preharvest fruit-drop. The persistence and risk assessment of 2,4-D sodium after applying on bayberries were investigated. A method for determining 2,4-D sodium in bayberry was established based on LC-MS-MS. The average recoveries of 2,4-D sodium were at the range of 93.7-95.8% with relative standard deviations (RSDs) ranging from 0.9 to 2.8%. The dissipation rates of 2,4-D sodium were described using first-order kinetics, and its half-life ranged from 11.2 to 13.8 days. A bayberry consumption survey was carried out for Chinese adults for the first time. The safety assessments of 2,4-D sodium were conducted by using field trail data as well as monitoring data. Results showed that the chronic risk quotient and the acute risk quotient were calculated to be 0.23-0.59 and 0.02-0.05%, respectively, for Chinese adults, indicating low dietary risk for adults and children. In the end, the household cleaning steps were compared, and results showed that water rinsing for 1 min can remove 49.9% 2,4-D sodium residue, which provides pesticide removal suggestion for consumers.

  12. Drop coalescence studies

    NASA Technical Reports Server (NTRS)

    Anikumar, A. V.; Wang, T. G.

    1990-01-01

    The objective of this experimental study is to understand the detailed mechanics of the coalescence of liquid drops. The experiments are being conducted in an immiscible acoustic levitator with degassed water as the host medium. Typically, a quasineutrally buoyant drop of silicon oil mixed with bromobenzene is levitated close to the velocity node of the levitator. A second drop of the same liquid is introduced, and as it slowly seeks levitation position, the drops coalesce. Coalescence is delayed until the host film between drops is completely drained. Following coalescence, the excess surface energy in the coalesced drop is dissipated through shape oscillations. The final events of film rupture followed by drop coalescence are rapid and are photographically studied with high-speed video (1000 fps). The laser-induced fluorescence technique is used to visualize the dynamics of host film drainage. The details of the coalescence mechanics are presented.

  13. Pressure drop, heat transfer, critical heat flux, and flow stability of two-phase flow boiling of water and ethylene glycol/water mixtures - final report for project "Efficent cooling in engines with nucleate boiling."

    SciTech Connect

    Yu, W.; France, D. M.; Routbort, J. L.

    2011-01-19

    Because of its order-of-magnitude higher heat transfer rates, there is interest in using controllable two-phase nucleate boiling instead of conventional single-phase forced convection in vehicular cooling systems to remove ever increasing heat loads and to eliminate potential hot spots in engines. However, the fundamental understanding of flow boiling mechanisms of a 50/50 ethylene glycol/water mixture under engineering application conditions is still limited. In addition, it is impractical to precisely maintain the volume concentration ratio of the ethylene glycol/water mixture coolant at 50/50. Therefore, any investigation into engine coolant characteristics should include a range of volume concentration ratios around the nominal 50/50 mark. In this study, the forced convective boiling heat transfer of distilled water and ethylene glycol/water mixtures with volume concentration ratios of 40/60, 50/50, and 60/40 in a 2.98-mm-inner-diameter circular tube has been investigated in both the horizontal flow and the vertical flow. The two-phase pressure drop, the forced convective boiling heat transfer coefficient, and the critical heat flux of the test fluids were determined experimentally over a range of the mass flux, the vapor mass quality, and the inlet subcooling through a new boiling data reduction procedure that allowed the analytical calculation of the fluid boiling temperatures along the experimental test section by applying the ideal mixture assumption and the equilibrium assumption along with Raoult's law. Based on the experimental data, predictive methods for the two-phase pressure drop, the forced convective boiling heat transfer coefficient, and the critical heat flux under engine application conditions were developed. The results summarized in this final project report provide the necessary information for designing and implementing nucleate-boiling vehicular cooling systems.

  14. Climate and Human Pressure Constraints Co-Explain Regional Plant Invasion at Different Spatial Scales

    PubMed Central

    García-Baquero, Gonzalo; Caño, Lidia; Biurrun, Idoia; García-Mijangos, Itziar; Loidi, Javier; Herrera, Mercedes

    2016-01-01

    Alien species invasion represents a global threat to biodiversity and ecosystems. Explaining invasion patterns in terms of environmental constraints will help us to assess invasion risks and plan control strategies. We aim to identify plant invasion patterns in the Basque Country (Spain), and to determine the effects of climate and human pressure on that pattern. We modeled the regional distribution of 89 invasive plant species using two approaches. First, distance-based Moran’s eigenvector maps were used to partition variation in the invasive species richness, S, into spatial components at broad and fine scales; redundancy analysis was then used to explain those components on the basis of climate and human pressure descriptors. Second, we used generalized additive mixed modeling to fit species-specific responses to the same descriptors. Climate and human pressure descriptors have different effects on S at different spatial scales. Broad-scale spatially structured temperature and precipitation, and fine-scale spatially structured human population density and percentage of natural and semi-natural areas, explained altogether 38.7% of the total variance. The distribution of 84% of the individually tested species was related to either temperature, precipitation or both, and 68% was related to either population density or natural and semi-natural areas, displaying similar responses. The spatial pattern of the invasive species richness is strongly environmentally forced, mainly by climate factors. Since individual species responses were proved to be both similarly constrained in shape and explained variance by the same environmental factors, we conclude that the pattern of invasive species richness results from individual species’ environmental preferences. PMID:27741276

  15. Climate and Human Pressure Constraints Co-Explain Regional Plant Invasion at Different Spatial Scales.

    PubMed

    Campos, Juan Antonio; García-Baquero, Gonzalo; Caño, Lidia; Biurrun, Idoia; García-Mijangos, Itziar; Loidi, Javier; Herrera, Mercedes

    2016-01-01

    Alien species invasion represents a global threat to biodiversity and ecosystems. Explaining invasion patterns in terms of environmental constraints will help us to assess invasion risks and plan control strategies. We aim to identify plant invasion patterns in the Basque Country (Spain), and to determine the effects of climate and human pressure on that pattern. We modeled the regional distribution of 89 invasive plant species using two approaches. First, distance-based Moran's eigenvector maps were used to partition variation in the invasive species richness, S, into spatial components at broad and fine scales; redundancy analysis was then used to explain those components on the basis of climate and human pressure descriptors. Second, we used generalized additive mixed modeling to fit species-specific responses to the same descriptors. Climate and human pressure descriptors have different effects on S at different spatial scales. Broad-scale spatially structured temperature and precipitation, and fine-scale spatially structured human population density and percentage of natural and semi-natural areas, explained altogether 38.7% of the total variance. The distribution of 84% of the individually tested species was related to either temperature, precipitation or both, and 68% was related to either population density or natural and semi-natural areas, displaying similar responses. The spatial pattern of the invasive species richness is strongly environmentally forced, mainly by climate factors. Since individual species responses were proved to be both similarly constrained in shape and explained variance by the same environmental factors, we conclude that the pattern of invasive species richness results from individual species' environmental preferences.

  16. Membrane associated qualitative differences in cell ultrastructure of chemically and high pressure cryofixed plant cells.

    PubMed

    Zechmann, Bernd; Müller, Maria; Zellnig, Günther

    2007-06-01

    Membrane contrast can sometimes be poor in biological samples after high pressure freezing (HPF) and freeze substitution (FS). The addition of water to the FS-medium has been shown to improve membrane contrast in animal tissue and yeast. In the present study we tested the effects of 1% and 5% water added to the FS-medium (2% osmium with 0.2% uranyl acetate in anhydrous acetone) on the quality and visibility of membranes in high pressure frozen leaf samples of Cucurbita pepo L. plants and compared them to chemically fixed cells (3% glutaraldehyde post-fixed with 1% osmium tetroxide). The addition of water to the FS-medium drastically decreased the amounts of well preserved cells and did not significantly improve the quality nor visibility of membranes. In samples that were freeze substituted in FS-media containing 1% and 5% water the width of thylakoid membranes was found to be significantly increased of about 20% and the perinuclear space was up to 76% wider in comparison to what was found in samples which were freeze substituted without water. No differences were found in the thickness of membranes between chemically and cryofixed cells that were freeze substituted in the FS-medium without water. Nevertheless, in chemically fixed cells the intrathylakoidal space was about 120% wider than in cryofixed cells that were freeze substituted with or without water. The present results demonstrate that the addition of water to the FS-medium does not improve membrane contrast but changes the width of thylakoid membranes and the perinuclear space in the present plant material. The addition of water to the FS-medium is therefore not as essential for improved membrane contrast in the investigated plant samples as it was observed in cells of animal tissues and yeast cells.

  17. Estimating past leaf-to-air vapour pressure deficit from terrestrial plant 13C

    NASA Astrophysics Data System (ADS)

    Turney, Chris S. M.; Barringer, James; Hunt, John E.; McGlone, Matt S.

    1999-08-01

    13C was determined in lignin extracted from present-day cladodes of Phyllocladus alpinus (a small coniferous tree) from seven well-lit sites across New Zealand. The 13C values ranged from -30.9 to -23.6 and were compared with monthly means of temperature, precipitation, relative humidity and vapour pressure deficit from the nearest recording stations. Of these parameters, the leaf-to-air vapour pressure deficit of the first month of cladode growth and expansion proved to be the most significantly correlated with lignin 13C, over a range of 0.3 to 0.8 kPa, confirming the importance of atmospheric moisture content on stomatal conductance. The carbon isotopic signature of lignin from fossilised cladodes preserved under the Kawakawa Tephra (22.6 k 14C yr BP) on the North Island is identical to that of the whole tissue, suggesting that for this species at least, fossil material can be used to approximate the lignin 13C. The 13C of species- and organ-specific fossil terrestrial plant material therefore provides an excellent method to quantify past changes in leaf-to-air vapour pressure deficit.

  18. Role of turgor pressure and solute transport in plant cell growth: Progress report

    SciTech Connect

    Cosgrove, D.J.

    1987-10-15

    We have worked on three major areas, as outlined in the major grant proposal of last year. These are measurement of wall relaxation by pressurization, coupling between cell expansion and solute uptake, and experiments with severed aphids. We have advanced very rapidly in the first area, reasonably well in the second area, and have been delayed in the third area. A new method, termed the pressure-block technique, was developed this past year to measure the yielding characteristics of growing plant cell walls. The way it works is as follows. Our first approach in studying the relationship between solute uptake and growth was to reduce the solute supply to elongating pea stems of etiolated seedlings by excising the cotyledons. Solute import was effectively stopped over the 5 h period after excision; no net change in dry weight of a 0.5 cm segment occurred 5 h after cotyledon removal, compared to an increase of 0.3 mg in intact seedlings. We constructed a radio frequency microcautery device, and succeeded in excising the stylets from pea aphids feeding on pea epicotyls, but exudation quickly ceased. It may prove more practical to probe into the phloem directly with the pressure probe, without using the aphid stylet.

  19. Non-coalescence of oppositely charged drops

    NASA Astrophysics Data System (ADS)

    Ristenpart, W. D.; Bird, J. C.; Belmonte, A.; Dollar, F.; Stone, H. A.

    2009-11-01

    Electrically induced droplet motion manifests itself in processes as diverse as storm cloud formation, commercial ink-jet printing, petroleum and vegetable oil dehydration, electrospray ionization in mass spectrometry, electrowetting and lab-on-a-chip manipulations. An important issue in practical applications is the tendency for adjacent drops to coalesce, and oppositely charged drops have long been assumed to experience an attractive force that favors their coalescence. Here we report the existence of a critical field strength above which oppositely charged drops do not coalesce. We observe that appropriately positioned and oppositely charged drops migrate towards one another in an applied electric field; but whereas the drops coalesce as expected at low field strengths, they are repelled from one another after contact at higher field strengths. Qualitatively, the drops appear to ``bounce'' off one another. We directly image the transient formation of a meniscus bridge between the bouncing drops, and propose that this temporary bridge is unstable with respect to capillary pressure when it forms in an electric field exceeding a critical strength. The observation of oppositely charged drops bouncing in strong electric fields should affect our understanding of any process involving charged liquid drops, including de-emulsification, electrospray ionization and atmospheric conduction.

  20. Micro-explosion of compound drops

    NASA Astrophysics Data System (ADS)

    Chen, Chun-Kuei; Lin, Ta-Hui

    2014-08-01

    Introducing water into spray combustion systems, by either water-in-oil emulsification or supplementary water injection, is one of the major techniques for combustion improvement and NOx reduction. Plentiful researches are available on combustion of water-in-oil emulsion fuel drops. The emulsified liquid is a heterogeneous mixture of immiscible liquids. One component forms the continuous phase and the other component forms the discrete phase. The discrete phase consists of globules of the one fluid that are suspended in the continuous phase fluid. Water-in-oil emulsions are commonly considered for combustion applications because emulsions can result in micro-explosion, thereby reducing the average drop diameter to enhance liquid vaporization, and suppressing the formation of soot and NOx. However, the water addition generally does not exceed about 20% for smooth engine operations[!, 21. The combustion characteristics and micro-explosion of emulsion drop were studied by many researchers. The micro-explosion of water in fuel emulsion drops was caused by very fast growth of superheated water vapor bubbles, its superheat limits must be lower than the boiling point temperature of the fuel. These bubbles were primarily governed by the pressure difference between the superheated vapor and the liquid, and by the inertia imparted to the liquid by the motion of the bubble surface[3 6 In this study, we used a coaxial nozzle to generation the multi-component drop. The different type of water-in-oil fuel drops called the compound drops. Unlike an emulsion drop, a compound drop consists of a water core and a fuel shell, which can originate from the phase separation of emulsion[7, 81 or a water drop colliding with a fuel drop[9, 101 Burning and micro-explosion of compound drops have been found to be distinct from those of emulsion drops[9-111 Wang et al.[9 , 101 studied the combustion characteristics of collision merged alkane-water drops. The merged drops appeared in adhesive

  1. Aging of the containment pressure boundary in light-water reactor plants

    SciTech Connect

    Naus, D.J.; Oland, C.B.; Ellingwood, B.R.

    1997-01-01

    Research is being conducted by the Oak Ridge National Laboratory to address aging of the containment pressure boundary in light-water reactor plants. The objectives of this work are to (1) identify the significant factors related to occurrence of corrosion, efficacy of inspection, and structural capacity reduction of steel containments and liners of concrete containments, and to make recommendations on use of risk models in regulatory decisions; (2) provide NRC reviewers a means of establishing current structural capacity margins for steel containments, and concrete containments as limited by liner integrity; and (3) provide recommendations, as appropriate, on information to be requested of licensees for guidance that could be utilized by NRC reviewers in assessing the seriousness of reported incidences of containment degradation. In meeting these objectives research is being conducted in two primary task areas - pressure boundary condition assessment and root-cause resolution practices, and reliability-based condition assessments. Under the first task area a degradation assessment methodology was developed for use in characterizing the in-service condition of metal and concrete containment pressure boundary components and quantifying the amount of damage that is present. An assessment of available destructive and nondestructive techniques for examining steel containments and liners is ongoing. Under the second task area quantitative structural reliability analysis methods are being developed for application to degraded metallic pressure boundaries to provide assurances that they will be able to withstand future extreme loads during the desired service period with a level of reliability that is sufficient for public safety. To date, mathematical models that describe time-dependent changes in steel due to aggressive environmental factors have been identified, and statistical data supporting their use in time-dependent reliability analysis have been summarized.

  2. Ethylene reduces plant gas exchange and growth of lettuce grown from seed to harvest under hypobaric and ambient total pressure.

    PubMed

    He, Chuanjiu; Davies, Fred T

    2012-03-01

    Naturally occurring high levels of ethylene can be a problem in spaceflight and controlled environment agriculture (CEA) leading to sterility and irregular plant growth. There are engineering and safety advantages of growing plants under hypobaria (low pressure) for space habitation. The goals of this research were to successfully grow lettuce (Lactuca sativa cv. Buttercrunch) in a long-term study from seed to harvest under hypobaric conditions, and to investigate how endogenously produced ethylene affects gas exchange and plant growth from seed germination to harvest under hypobaric and ambient total pressure conditions. Lettuce was grown under two levels of total gas pressure [hypobaric or ambient (25 or 101 kPa)] in a long-term, 32-day study. Significant levels of endogenous ethylene occurred by day-15 causing reductions in photosynthesis, dark-period respiration, and a subsequent decrease in plant growth. Hypobaria did not mitigate the adverse ethylene effects on plant growth. Seed germination was not adversely affected by hypobaria, but was reduced by hypoxia (6 kPa pO(2)). Under hypoxia, seed germination was higher under hypobaria than ambient total pressure. This research shows that lettuce can be grown from seed to harvest under hypobaria (≅25% of normal earth ambient total pressure). Copyright © 2011 Elsevier GmbH. All rights reserved.

  3. The photosynthetic response of tobacco plants overexpressing ice plant aquaporin McMIPB to a soil water deficit and high vapor pressure deficit.

    PubMed

    Kawase, Miki; Hanba, Yuko T; Katsuhara, Maki

    2013-07-01

    We investigated the photosynthetic capacity and plant growth of tobacco plants overexpressing ice plant (Mesembryanthemum crystallinum L.) aquaporin McMIPB under (1) a well-watered growth condition, (2) a well-watered and temporal higher vapor pressure deficit (VPD) condition, and (3) a soil water deficit growth condition to investigate the effect of McMIPB on photosynthetic responses under moderate soil and atmospheric humidity and water deficit conditions. Transgenic plants showed a significantly higher photosynthesis rate (by 48 %), higher mesophyll conductance (by 52 %), and enhanced growth under the well-watered growth condition than those of control plants. Decreases in the photosynthesis rate and stomatal conductance from ambient to higher VPD were slightly higher in transgenic plants than those in control plants. When plants were grown under the soil water deficit condition, decreases in the photosynthesis rate and stomatal conductance were less significant in transgenic plants than those in control plants. McMIPB is likely to work as a CO2 transporter, as well as control the regulation of stomata to water deficits.

  4. Assessing the impact of electrolyte conductivity and viscosity on the reactor cost and pressure drop of redox-active polymer flow batteries

    NASA Astrophysics Data System (ADS)

    Iyer, Vinay A.; Schuh, Jonathon K.; Montoto, Elena C.; Pavan Nemani, V.; Qian, Shaoyi; Nagarjuna, Gavvalapalli; Rodríguez-López, Joaquín; Ewoldt, Randy H.; Smith, Kyle C.

    2017-09-01

    Redox-active small molecules, used traditionally in redox flow batteries (RFBs), are susceptible to crossover and require expensive ion exchange membranes (IEMs) to achieve long lifetimes. Redox-active polymer (RAP) solutions show promise as candidate electrolytes to mitigate crossover through size-exclusion, enabling the use of porous separators instead of IEMs. Here, poly(vinylbenzyl ethyl viologen) is studied as a surrogate RAP for RFBs. For oxidized RAPs, ionic conductivity varies weakly between 1.6 and 2.1 S m-1 for RAP concentrations of 0.13-1.27 mol kg-1 (monomeric repeat unit per kg solvent) and 0.32 mol kg-1 LiBF4 with a minor increase upon reduction. In contrast, viscosity varies between 1.8 and 184.0 mPa s over the same concentration range with weakly shear-thinning rheology independent of oxidation state. Techno-economic analysis is used to quantify reactor cost as a function of electrolyte transport properties for RAP concentrations of 0.13-1.27 mol kg-1, assuming a hypothetical 3V cell and facile kinetics. Among these concentrations, reactor cost is minimized over a current density range of 600-1000 A m-2 with minimum reactor cost between 11-17 per kWh, and pumping pressures below 10 kPa. The predicted low reactor cost of RAP RFBs is enabled by sustained ionic mobility in spite of the high viscosity of concentrated RAP solutions.

  5. Scanning drop sensor

    DOEpatents

    Jin, Jian; Xiang, Chengxiang; Gregoire, John M.; Shinde, Aniketa A.; Guevarra, Dan W.; Jones, Ryan J.; Marcin, Martin R.; Mitrovic, Slobodan

    2017-05-09

    Electrochemical or electrochemical and photochemical experiments are performed on a collection of samples by suspending a drop of electrolyte solution between an electrochemical experiment probe and one of the samples that serves as a test sample. During the electrochemical experiment, the electrolyte solution is added to the drop and an output solution is removed from the drop. The probe and collection of samples can be moved relative to one another so the probe can be scanned across the samples.

  6. Scanning drop sensor

    DOEpatents

    Jin, Jian; Xiang, Chengxiang; Gregoire, John

    2017-05-09

    Electrochemical experiments are performed on a collection of samples by suspending a drop of electrolyte solution between an electrochemical experiment probe and one of the samples that serves as a test sample. During the electrochemical experiment, the electrolyte solution is added to the drop and an output solution is removed from the drop. The probe and collection of samples can be moved relative to one another so the probe can be scanned across the samples.

  7. Generalized Charts for Determination of Pressure Drop of a High-speed Compressible Fluid in Heat-exchanger Passages I : Air Heated in Smooth Passages of Constant Area with Constant Wall Temperature

    NASA Technical Reports Server (NTRS)

    Valerino, Michael F

    1948-01-01

    In the present paper an analysis is made of the compressible-flow variations occurring in heat-exchanger passages. The results of the analysis describe the flow and heating characteristics for which specific flow passages can be treated as segments of generalized flow systems. The graphical representation of the flow variations in the generalized flow systems can then be utilized as working charts to determine directly the pressure changes occurring in any specific flow passage. On the basis of these results, working charts are constructed to handle the case of air heated at constant wall temperature under turbulent-flow conditions. A method is given of incorporating the effect on the heat-exchanger flow process of high temperature differential between passage wall and fluid as based on recent NACA experimental data. Good agreement is obtained between the experimental and the chart pressure-drop values for passage-wall average temperatures as high as 1752 degrees R (experimental limit) and for flow Mach numbers ranging from 0.32 to 1.00 (choke) at the passage exit.

  8. Drag on Sessile Drops

    NASA Astrophysics Data System (ADS)

    Milne, Andrew J. B.; Fleck, Brian; Nobes, David; Sen, Debjyoti; Amirfazli, Alidad; University of Alberta Mechanical Engineering Collaboration

    2013-11-01

    We present the first ever direct measurements of the coefficient of drag on sessile drops at Reynolds numbers from the creeping flow regime up to the point of incipient motion, made using a newly developed floating element differential drag sensor. Surfaces of different wettabilities (PMMA, Teflon, and a superhydrophobic surface (SHS)), wet by water, hexadecane, and various silicone oils, are used to study the effects of drop shape, and fluid properties on drag. The relation between drag coefficient and Reynolds number (scaled by drop height) varies slightly with liquid-solid system and drop volume with results suggesting the drop experiences increased drag compared to similar shaped solid bodies due to drop oscillation influencing the otherwise laminar flow. Drops adopting more spherical shapes are seen to experience the greatest force at any given airspeed. This indicates that the relative exposed areas of drops is an important consideration in terms of force, with implications for the shedding of drops in applications such as airfoil icing and fuel cell flooding. The measurement technique used in this work can be adapted to measure drag force on other deformable, lightly adhered objects such as dust, sand, snow, vesicles, foams, and biofilms. The authours acknowledge NSERC, Alberta Innovates Technology Futures, and the Killam Trusts.

  9. Inhibition of Angiotensin Converting Enzyme, Angiotensin II Receptor Blocking, and Blood Pressure Lowering Bioactivity across Plant Families.

    PubMed

    Patten, Glen S; Abeywardena, Mahinda Y; Bennett, Louise E

    2016-01-01

    Hypertension is a major risk factor for coronary heart disease, kidney disease, and stroke. Interest in medicinal or nutraceutical plant bioactives to reduce hypertension has increased dramatically. The main biological regulation of mammalian blood pressure is via the renin-angiotensin-aldosterone system. The key enzyme is angiotensin converting enzyme (ACE) that converts angiotensin I into the powerful vasoconstrictor, angiotensin II. Angiotensin II binds to its receptors (AT1) on smooth muscle cells of the arteriole vasculature causing vasoconstriction and elevation of blood pressure. This review focuses on the in vitro and in vivo reports of plant-derived extracts that inhibit ACE activity, block angiotensin II receptor binding and demonstrate hypotensive activity in animal or human studies. We describe 74 families of plants that exhibited significant ACE inhibitory activity and 16 plant families with potential AT1 receptor blocking activity, according to in vitro studies. From 43 plant families including some of those with in vitro bioactivity, the extracts from 73 plant species lowered blood pressure in various normotensive or hypertensive in vivo models by the oral route. Of these, 19 species from 15 families lowered human BP when administered orally. Some of the active plant extracts, isolated bioactives and BP-lowering mechanisms are discussed.

  10. Regulator or driving force? The role of turgor pressure in oscillatory plant cell growth.

    PubMed

    Kroeger, Jens H; Zerzour, Rabah; Geitmann, Anja

    2011-04-25

    Turgor generates the stress that leads to the expansion of plant cell walls during cellular growth. This has been formalized by the Lockhart equation, which can be derived from the physical laws of the deformation of viscoelastic materials. However, the experimental evidence for such a direct correlation between growth rate and turgor is inconclusive. This has led to challenges of the Lockhart model. We model the oscillatory growth of pollen tubes to investigate this relationship. We couple the Lockhart equation to the dynamical equations for the change in material properties. We find that the correct implementation of the Lockhart equation within a feedback loop leading to low amplitude oscillatory growth predicts that in this system changes in the global turgor do not influence the average growth rate in a linear manner, consistent with experimental observations. An analytic analysis of our model demonstrates in which regime the average growth rate becomes uncorrelated from the turgor pressure.

  11. Regulator or Driving Force? The Role of Turgor Pressure in Oscillatory Plant Cell Growth

    PubMed Central

    Kroeger, Jens H.; Zerzour, Rabah; Geitmann, Anja

    2011-01-01

    Turgor generates the stress that leads to the expansion of plant cell walls during cellular growth. This has been formalized by the Lockhart equation, which can be derived from the physical laws of the deformation of viscoelastic materials. However, the experimental evidence for such a direct correlation between growth rate and turgor is inconclusive. This has led to challenges of the Lockhart model. We model the oscillatory growth of pollen tubes to investigate this relationship. We couple the Lockhart equation to the dynamical equations for the change in material properties. We find that the correct implementation of the Lockhart equation within a feedback loop leading to low amplitude oscillatory growth predicts that in this system changes in the global turgor do not influence the average growth rate in a linear manner, consistent with experimental observations. An analytic analysis of our model demonstrates in which regime the average growth rate becomes uncorrelated from the turgor pressure. PMID:21541026

  12. High-pressure freezing and low-temperature processing of plant tissue samples for electron microscopy.

    PubMed

    Karahara, Ichirou; Kang, Byung-Ho

    2014-01-01

    Use of electron tomography methods improves image resolution of transmission electron microscopy especially in the z-direction, enabling determination of complicated 3D structures of organelles and cytoskeleton arrays. The increase in resolution necessitates preservation of cellular structures close to the native states with minimum artifacts. High-pressure freezing (HPF) that immobilizes molecules in the cell instantaneously has been used to avoid damages caused by convention chemical fixation. Despite the advantages of HPF, cells could still be damaged during dissection prior to HPF. Therefore, it is critical to isolate cells/tissues of interest quickly and carefully. The samples frozen by HPF are often processed by freeze substitution (FS), and FS should be carried out under appropriate conditions. Here we describe dissection, HPF, and FS methods that we have utilized to prepare plant samples for electron tomography/immuno-electron microscopy.

  13. Ball tonometry: a rapid, nondestructive method for measuring cell turgor pressure in thin-walled plant cells

    NASA Technical Reports Server (NTRS)

    Lintilhac, P. M.; Wei, C.; Tanguay, J. J.; Outwater, J. O.

    2000-01-01

    In this article we describe a new method for the determination of turgor pressures in living plant cells. Based on the treatment of growing plant cells as thin-walled pressure vessels, we find that pressures can be accurately determined by observing and measuring the area of the contact patch formed when a spherical glass probe is lowered onto the cell surface with a known force. Within the limits we have described, we can show that the load (determined by precalibration of the device) divided by the projected area of the contact patch (determined by video microscopy) provides a direct, rapid, and accurate measure of the internal turgor pressure of the cell. We demonstrate, by parallel measurements with the pressure probe, that our method yields pressure data that are consistent with those from the pressure probe. Also, by incubating target tissues in stepped concentrations of mannitol to incrementally reduce the turgor pressure, we show that the pressures measured by tonometry accurately reflect the predicted changes from the osmotic potential of the bathing medium. The advantages of this new method over the pressure probe are considerable, however, in that we can move rapidly from cell to cell, taking measurements every 20 s. In addition, the nondestructive nature of the method means that we can return to the same cell repeatedly for periodic pressure measurements. The limitations of the method lie in the fact that it is suitable only for superficial cells that are directly accessible to the probe and to cells that are relatively thin walled and not heavily decorated with surface features. It is also not suitable for measuring pressures in flaccid cells.

  14. Ball tonometry: a rapid, nondestructive method for measuring cell turgor pressure in thin-walled plant cells

    NASA Technical Reports Server (NTRS)

    Lintilhac, P. M.; Wei, C.; Tanguay, J. J.; Outwater, J. O.

    2000-01-01

    In this article we describe a new method for the determination of turgor pressures in living plant cells. Based on the treatment of growing plant cells as thin-walled pressure vessels, we find that pressures can be accurately determined by observing and measuring the area of the contact patch formed when a spherical glass probe is lowered onto the cell surface with a known force. Within the limits we have described, we can show that the load (determined by precalibration of the device) divided by the projected area of the contact patch (determined by video microscopy) provides a direct, rapid, and accurate measure of the internal turgor pressure of the cell. We demonstrate, by parallel measurements with the pressure probe, that our method yields pressure data that are consistent with those from the pressure probe. Also, by incubating target tissues in stepped concentrations of mannitol to incrementally reduce the turgor pressure, we show that the pressures measured by tonometry accurately reflect the predicted changes from the osmotic potential of the bathing medium. The advantages of this new method over the pressure probe are considerable, however, in that we can move rapidly from cell to cell, taking measurements every 20 s. In addition, the nondestructive nature of the method means that we can return to the same cell repeatedly for periodic pressure measurements. The limitations of the method lie in the fact that it is suitable only for superficial cells that are directly accessible to the probe and to cells that are relatively thin walled and not heavily decorated with surface features. It is also not suitable for measuring pressures in flaccid cells.

  15. Nematicidal potential of hydrolates from the semi industrial vapor-pressure extraction of Spanish aromatic plants.

    PubMed

    Andrés, Maria Fe; González-Coloma, Azucena; Muñoz, Ruben; De la Peña, Felipe; Julio, Luis Fernando; Burillo, Jesus

    2017-06-22

    The nematicidal activity of hydrolate by-products from the semi industrial vapor-pressure essential oil extraction of selected aromatic plant species (commercial: Lavandula × intermedia Emeric ex Loisel. var. super, Thymus vulgaris L., T. zygis Loefl ex L. and experimentally pre-domesticated: L. luisieri (Rozeira) Rivas-Martínez) was investigated against the root-knot nematode Meloidogyne javanica by in vitro and in vivo bioassays. Liquid-liquid extraction of hydrolates yielded the corresponding aqueous and organic fractions which were biological and chemically studied. Hydrolates from L. × intermedia var. super, L. luisieri, T. vulgaris, and T. zygis showed strong in vitro nematicidal effects against M. javanica (J2 mortality and suppression of egg hatching). In the case of the Thymus species, the active components were found in the organic fraction, characterized by thymol as major component. Conversely, the nematicidal activity of L. × intermedia var. super and L. luisieri remained in the corresponding aqueous fractions. In vivo tests on tomato seedlings at sublethal doses of the hydrolates/organic fractions induced a significant reduction of nematode infectivity. In pot experiments, all hydrolates tested on tomato plants significantly affect the infection frequency and reproduction rate of the nematode population. This study demonstrates that L. × intermedia var. super, L. luisieri, T. vulgaris, and T. zygis hydrolates could be an exploitable source of potential waste protection products on root-knot nematodes.

  16. Propagule Pressure, Habitat Conditions and Clonal Integration Influence the Establishment and Growth of an Invasive Clonal Plant, Alternanthera philoxeroides.

    PubMed

    You, Wen-Hua; Han, Cui-Min; Fang, Long-Xiang; Du, Dao-Lin

    2016-01-01

    Many notorious invasive plants are clonal, spreading mainly by vegetative propagules. Propagule pressure (the number of propagules) may affect the establishment, growth, and thus invasion success of these clonal plants, and such effects may also depend on habitat conditions. To understand how propagule pressure, habitat conditions and clonal integration affect the establishment and growth of the invasive clonal plants, an 8-week greenhouse with an invasive clonal plant, Alternanthera philoxeroides was conducted. High (five fragments) or low (one fragment) propagule pressure was established either in bare soil (open habitat) or dense native vegetation of Jussiaea repens (vegetative habitat), with the stolon connections either severed from or connected to the relatively older ramets. High propagule pressure greatly increased the establishment and growth of A. philoxeroides, especially when it grew in vegetative habitats. Surprisingly, high propagule pressure significantly reduced the growth of individual plants of A. philoxeroides in open habitats, whereas it did not affect the individual growth in vegetative habitats. A shift in the intraspecific interaction on A. philoxeroides from competition in open habitats to facilitation in vegetative habitats may be the main reason. Moreover, clonal integration significantly improved the growth of A. philoxeroides only in open habitats, especially with low propagule pressure, whereas it had no effects on the growth and competitive ability of A. philoxeroides in vegetative habitats, suggesting that clonal integration may be of most important for A. philoxeroides to explore new open space and spread. These findings suggest that propagule pressure may be crucial for the invasion success of A. philoxeroides, and such an effect also depends on habitat conditions.

  17. Propagule Pressure, Habitat Conditions and Clonal Integration Influence the Establishment and Growth of an Invasive Clonal Plant, Alternanthera philoxeroides

    PubMed Central

    You, Wen-Hua; Han, Cui-Min; Fang, Long-Xiang; Du, Dao-Lin

    2016-01-01

    Many notorious invasive plants are clonal, spreading mainly by vegetative propagules. Propagule pressure (the number of propagules) may affect the establishment, growth, and thus invasion success of these clonal plants, and such effects may also depend on habitat conditions. To understand how propagule pressure, habitat conditions and clonal integration affect the establishment and growth of the invasive clonal plants, an 8-week greenhouse with an invasive clonal plant, Alternanthera philoxeroides was conducted. High (five fragments) or low (one fragment) propagule pressure was established either in bare soil (open habitat) or dense native vegetation of Jussiaea repens (vegetative habitat), with the stolon connections either severed from or connected to the relatively older ramets. High propagule pressure greatly increased the establishment and growth of A. philoxeroides, especially when it grew in vegetative habitats. Surprisingly, high propagule pressure significantly reduced the growth of individual plants of A. philoxeroides in open habitats, whereas it did not affect the individual growth in vegetative habitats. A shift in the intraspecific interaction on A. philoxeroides from competition in open habitats to facilitation in vegetative habitats may be the main reason. Moreover, clonal integration significantly improved the growth of A. philoxeroides only in open habitats, especially with low propagule pressure, whereas it had no effects on the growth and competitive ability of A. philoxeroides in vegetative habitats, suggesting that clonal integration may be of most important for A. philoxeroides to explore new open space and spread. These findings suggest that propagule pressure may be crucial for the invasion success of A. philoxeroides, and such an effect also depends on habitat conditions. PMID:27200041

  18. Cause Analysis of Pressure Plate Breakage of Valve Limit Switch in Turbine Bypass System of Nuclear Power Plant

    NASA Astrophysics Data System (ADS)

    Li, Nan; Wang, Ming chang; Guan, Jian jun; Li, Guo dong

    2017-07-01

    The limit switch plates of nuclear power plant unit 1 in the turbine bypass system valve are finding multiple fractures. On the basis of metallographic analysis and vibration analysis, the stress state of the pressure plate is simulated and calculated. The results show that there are some creases in the original plate of the limit switch and the installation error of the pressure plate is the main reason for the break.

  19. Drop Tower Physics

    ERIC Educational Resources Information Center

    Dittrich, William A.

    2014-01-01

    The drop towers of yesteryear were used to make lead shot for muskets, as described in "The Physics Teacher" in April 2012. However, modern drop towers are essentially elevators designed so that the cable can "break" on demand, creating an environment with microgravity for a short period of time, currently up to nine seconds at…

  20. Youth Crime