Behzadian, Farnaz; Yerushalmi, Laleh; Alimahmoodi, Mahmood; Mulligan, Catherine N
2013-08-01
The hydrodynamic characteristics and the overall volumetric oxygen transfer coefficient of a new multi-environment bioreactor which is an integrated part of a wastewater treatment system, called BioCAST, were studied. This bioreactor contains several zones with different environmental conditions including aerobic, microaerophilic and anoxic, designed to increase the contaminant removal capacity of the treatment system. The multi-environment bioreactor is designed based on the concept of airlift reactors where liquid is circulated through the zones with different environmental conditions. The presence of openings between the aerobic zone and the adjacent oxygen-depleted microaerophilic zone changes the hydrodynamic properties of this bioreactor compared to the conventional airlift designs. The impact of operating and process parameters, notably the hydraulic retention time (HRT) and superficial gas velocity (U(G)), on the hydrodynamics and mass transfer characteristics of the system was examined. The results showed that liquid circulation velocity (V(L)), gas holdup (ε) and overall volumetric oxygen transfer coefficient (k(L)a(L)) increase with the increase of superficial gas velocity (U(G)), while the mean circulation time (t(c)) decreases with the increase of superficial gas velocity. The mean circulation time between the aerobic zone (riser) and microaerophilic zone (downcomer) is a stronger function of the superficial gas velocity for the smaller openings (1/2 in.) between the two zones, while for the larger opening (1 in.) the mean circulation time is almost independent of U(G) for U(G) ≥ 0.023 m/s. The smaller openings between the two zones provide higher mass transfer coefficient and better zone generation which will contribute to improved performance of the system during treatment operations. PMID:23142846
Effects of oxygen transfer coefficient on dihydroxyacetone production from crude glycerol
Zheng, Xiao-juan; Jin, Kui-qi; Zhang, Lei; Wang, Gang; Liu, Yu-Peng
2016-01-01
The principal objective of this study was to evaluate the kinetics of dihydroxyacetone production by Gluconobacter frateurii CGMCC 5397 under different oxygen volumetric mass transfer coefficient (kLa) conditions in submerged bioreactors using biodiesel-derived crude glycerol as the carbon source. kLa is a key fermentation parameter for the production of dihydroxyacetone. Cultivations were conducted in baffled- and unbaffled-flask cultures (the kLa values were 24.32 h−1 and 52.05 h−1, respectively) and fed-batch cultures (the kLa values were held at 18.21 h−1, 46.03 h−1, and 82.14 h−1) to achieve high dihydroxyacetone concentration and productivity. The results showed that a high kLa could dramatically increase dihydroxyacetone concentrations and productivities. The baffled-flask culture (with a kLa of 52.05 h−1) favored glycerol utilization and dihydroxyacetone production, and a dihydroxyacetone concentration as high as 131.16 g/L was achieved. When the kLa was set to 82.14 h−1 in the fed-batch culture, the dihydroxyacetone concentration, productivity and yield were 175.44 g/L, 7.96 g/L/h and 0.89 g/g, respectively, all of which were significantly higher than those in previous studies and will benefit dihydroxyacetone industrial production. PMID:26887235
NASA Technical Reports Server (NTRS)
Liebert, Curt H.; Ehlers, Robert C.
1961-01-01
Local experimental heat-transfer coefficients were measured in the chamber and throat of a 2400-pound-thrust ammonia-oxygen rocket engine with a nominal chamber pressure of 600 pounds per square inch absolute. Three injector configurations were used. The rocket engine was run over a range of oxidant-fuel ratio and chamber pressure. The injector that achieved the best performance also produced the highest rates of heat flux at design conditions. The heat-transfer data from the best-performing injector agreed well with the simplified equation developed by Bartz at the throat region. A large spread of data was observed for the chamber. This spread was attributed generally to the variations of combustion processes. The spread was least evident, however, with the best-performing injector.
Parente, Eugenio; Piraino, Paolo; Fidaleo, Marcello; Moresi, Mauro
2004-10-01
The dynamic gassing-out method was used to assess the effect of stirrer speed, air flow rate and alginate concentration on the overall volumetric oxygen mass transfer coefficient (K(L)a) in a bench-top stirred fermenter equipped with two Rushton-type turbines. As the alginate concentration in the medium was increased from 0 to 2% (w/v), the liquid film time constant (tau(F)) increased from approx. 30 to 300% of the electrode time constant (tau(E)), clearly showing that the liquid-probe diffusion film affected the oxygen-electrode response. By accounting for delayed probe response, liquid film time constant and gas residence time, the corrected values of K(L)a were empirically correlated with the above independent variables as converted into gassed power input and aeration number per unit liquid volume and the effective liquid/water shear viscosity ratio. Despite an average error of 19%, such a correlation might be useful to adjust the oxygen transfer in bench-top stirred reactors during viscous aerobic fermentations. PMID:15015940
NASA Astrophysics Data System (ADS)
Consalvi, J. L.; Nmira, F.
2016-03-01
The main objective of this article is to quantify the influence of the soot absorption coefficient-Planck function correlation on radiative loss and flame structure in an oxygen-enhanced propane turbulent diffusion flame. Calculations were run with and without accounting for this correlation by using a standard k-ε model and the steady laminar flamelet model (SLF) coupled to a joint Probability Density Function (PDF) of mixture fraction, enthalpy defect, scalar dissipation rate, and soot quantities. The PDF transport equation is solved by using a Stochastic Eulerian Field (SEF) method. The modeling of soot production is carried out by using a flamelet-based semi-empirical acetylene/benzene soot model. Radiative heat transfer is modeled by using a wide band correlated-k model and turbulent radiation interactions (TRI) are accounted for by using the Optically-Thin Fluctuation Approximation (OTFA). Predicted soot volume fraction, radiant wall heat flux distribution and radiant fraction are in good agreement with the available experimental data. Model results show that soot absorption coefficient and Planck function are negatively correlated in the region of intense soot emission. Neglecting this correlation is found to increase significantly the radiative loss leading to a substantial impact on flame structure in terms of mean and rms values of temperature. In addition mean and rms values of soot volume fraction are found to be less sensitive to the correlation than temperature since soot formation occurs mainly in a region where its influence is low.
Gaspar, A; Strodiot, L; Thonart, P
1998-01-01
To improve xylanase productivity from Penicillium canescens 10-10c culture, an optimization of oxygen supply is required. Because the strain is sensitive to shear forces, leading to lower xylanase productivity as to morphological alteration, vigorous mixing is not desired. The influence of turbine design, agitation speed, and air flow rate on K1a (global mass transfer coefficient, h(-1)) and enzyme production is discussed. K1a values increased with agitation speed and air flow rate, whatever the impeller, in our assay conditions. Agitation had more influence on K1a values than air flow, when a disk-mounted blade's impeller (DT) is used; an opposite result was obtained with a hub-mounted pitched blade's impeller (PBT). Xylanase production appeared as a function of specific power (W/m3), and an optimum was found in 20 and 100 L STRs fitted with DT impellers. On the other hand, the use of a hub-mounted pitched blade impeller (PBT8), instead of a disk-mounted blade impeller (DT4), reduced the lag time of hemicellulase production and increased xylanase productivity 1.3-fold. PMID:18576019
Oxygen atom loss coefficient of carbon nanowalls
NASA Astrophysics Data System (ADS)
Mozetic, Miran; Vesel, Alenka; Stoica, Silviu Daniel; Vizireanu, Sorin; Dinescu, Gheorghe; Zaplotnik, Rok
2015-04-01
Extremely high values of atomic oxygen loss coefficient on carbon nanowall (CNW) surface are reported. CNW layers consisting of interconnected individual nanostructures with average length of 1.1 μm, average thickness of 66 nm and surface density of 3 CNW/μm2 were prepared by plasma jet enhanced chemical-vapor deposition using C2H2/H2/Ar gas mixtures. The samples were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), Raman spectrometry (RS) as well as X-ray photoelectron spectroscopy (XPS). The surface loss coefficient was measured at room temperature in a flowing afterglow at different densities of oxygen atoms supplied from inductively coupled radiofrequency O2 plasma. The RF generator operated at 13.56 MHz and different nominal powers up to 900 W corresponding to different O-atom density in the afterglow up to 1.3 × 1021 m-3. CNW and several different samples of known coefficients for heterogeneous surface recombination of neutral oxygen atoms have been placed separately in the afterglow chamber and the O-atom density in their vicinity was measured with calibrated catalytic probes. Comparison of measured results allowed for determination of the loss coefficient for CNWs and the obtained value of 0.59 ± 0.03 makes this material an extremely effective sink for O-atoms.
Oxygen transfer in a pressurized airlift bioreactor.
Campani, Gilson; Ribeiro, Marcelo Perencin Arruda; Horta, Antônio Carlos Luperni; Giordano, Roberto Campos; Badino, Alberto Colli; Zangirolami, Teresa Cristina
2015-08-01
Airlift bioreactors (ALBs) offer advantages over conventional systems, such as simplicity of construction, reduced risk of contamination, and efficient gas-liquid dispersion with low power consumption. ALBs are usually operated under atmospheric pressure. However, in bioprocesses with high oxygen demand, such as high cell density cultures, oxygen limitation may occur even when operating with high superficial gas velocity and air enriched with oxygen. One way of overcoming this drawback is to pressurize the reactor. In this configuration, it is important to assess the influence of bioreactor internal pressure on the gas hold-up, volumetric oxygen transfer coefficient (k(L)a), and volumetric oxygen transfer rate (OTR). Experiments were carried out in a concentric-tube airlift bioreactor with a 5 dm(3) working volume, equipped with a system for automatic monitoring and control of the pressure, temperature, and inlet gas flow rate. The results showed that, in disagreement with previous published results for bubble column and external loop airlift reactors, overpressure did not significantly affect k(L)a within the studied ranges of pressure (0.1-0.4 MPa) and superficial gas velocity in the riser (0.032-0.065 m s(-1)). Nevertheless, a positive effect on OTR was observed: it increased up to 5.4 times, surpassing by 2.3 times the oxygen transfer in a 4 dm(3) stirred tank reactor operated under standard cultivation conditions. These results contribute to the development of non-conventional reactors, especially pneumatic bioreactors operated using novel strategies for oxygen control. PMID:25903476
Radionuclide transfer to animal products: revised recommended transfer coefficient values.
Howard, B J; Beresford, N A; Barnett, C L; Fesenko, S
2009-03-01
A compilation has been undertaken of data which can be used to derive animal product transfer coefficients for radionuclides, including an extensive review of Russian language information. The resultant database has been used to provide recommended transfer coefficient values for a range of radionuclides to (i) cow, sheep and goat milk, (ii) meat (muscle) of cattle, sheep, goats, pigs and poultry and (iii) eggs. The values are used in a new IAEA handbook on transfer parameters which replaces that referred to as 'TRS 364'. The paper outlines the approaches and procedures used to identify and collate data, and assumptions used. There are notable differences between the TRS 364 'expected' values and the recommended values in the revised Handbook from the new database. Of the recommended values, three milk values are at least an order of magnitude higher than the TRS 364 values (Cr, Pu (cow) Pu (sheep)) and one milk value is lower (Ni (cow)). For meat, four values (Am, Cd, Sb (beef) I (pork)) are at least an order of magnitude higher than the TRS 364 values and eight values are at least an order of magnitude lower (Ru, Pu (beef), Ru, Sr, Zn (sheep), Ru, Sr (pork), Mn (poultry)). Many data gaps remain. PMID:19200625
Measuring Furnace/Sample Heat-Transfer Coefficients
NASA Technical Reports Server (NTRS)
Rosch, William R.; Fripp, Archibald L., Jr.; Debnam, William J., Jr.; Woodell, Glenn A.
1993-01-01
Complicated, inexact calculations now unnecessary. Device called HTX used to simulate and measure transfer of heat between directional-solidification crystal-growth furnace and ampoule containing sample of crystalline to be grown. Yields measurement data used to calculate heat-transfer coefficients directly, without need for assumptions or prior knowledge of physical properties of furnace, furnace gas, or specimen. Determines not only total heat-transfer coefficients but also coefficients of transfer of heat in different modes.
Analysis of a heat transfer device for measuring film coefficients
NASA Technical Reports Server (NTRS)
Medrow, R. A.; Johnson, R. L.; Loomis, W. R.; Wedeven, L. D.
1975-01-01
A heat transfer device consisting of a heated rotating cylinder in a bath was analyzed for its effectiveness to determine heat transfer coefficient of fluids. A time dependent analysis shows that the performance is insensitive to the value of heat transfer coefficient with the given rig configuration.
Heat transfer coefficients for drying in pulsating flows
Fraenkel, S.L.
1998-05-01
Pulsating flows generated by a Rijke type combustor are studied for drying of grains and food particles. It is assumed that the velocity fluctuations are the main factor in the enhancement of the drying process. The heat transfer coefficients for drying in vibrating beds are utilized to estimate the heat transfer coefficients of fixed beds in pulsating and permeating flows and are compared to the steady flow heat transfer coefficients obtained for solid porous bodies, after perturbing the main flow. The cases considered are compared to the convective heat transfer coefficients employed in non-pulsating drying.
Calculation of the mass transfer coefficient for the combustion of a carbon particle
Scala, Fabrizio
2010-01-15
In this paper we address the calculation of the mass transfer coefficient around a burning carbon particle in an atmosphere of O{sub 2}, N{sub 2}, CO{sub 2}, CO, and H{sub 2}O. The complete set of Stefan-Maxwell equations is analytically solved under the assumption of no homogeneous reaction in the boundary layer. An expression linking the oxygen concentration and the oxygen flux at the particle surface (as a function of the bulk gas composition) is derived which can be used to calculate the mass transfer coefficient. A very simple approximate explicit expression is also given for the mass transfer coefficient, that is shown to be valid in the low oxygen flux limit or when the primary combustion product is CO{sub 2}. The results are given in terms of a correction factor to the equimolar counter-diffusion mass transfer coefficient, which is typically available in the literature for specific geometries and/or fluid-dynamic conditions. The significance of the correction factor and the accuracy of the different available expressions is illustrated for several cases of practical interest. Results show that under typical combustion conditions the use of the equimolar counter-diffusion mass transfer coefficient can lead to errors up to 10%. Larger errors are possible in oxygen-enriched conditions, while the error is generally low in oxy-combustion. (author)
Viscosity and thermal conductivity coefficients of gaseous and liquid oxygen
NASA Technical Reports Server (NTRS)
Hanley, H. J. M.; Mccarty, R. D.; Sengers, J. V.
1974-01-01
Equations and tables are presented for the viscosity and thermal conductivity coefficients of gaseous and liquid oxygen at temperatures between 80 K and 400 K for pressures up to 200 atm. and at temperatures between 80 K and 2000 K for the dilute gas. A description of the anomalous behavior of the thermal conductivity in the critical region is included. The tabulated coefficients are reliable to within about 15% except for a region in the immediate vicinity of the critical point. Some possibilities for future improvements of this reliability are discussed.
Measurement of heat transfer coefficients by nuclear magnetic resonance.
Gultekin, David H; Gore, John C
2008-11-01
We demonstrate an experimental method for the measurement of heat transfer coefficient for a fluid system by magnetic resonance imaging. In this method, the temporal variation of thermally induced nuclear shielding is monitored and the average heat transfer coefficient is measured as a function of fluid velocity. We examine the cases of natural convection and forced convection at fluid velocity up to 0.8 m s(-1). These cases correspond to low dimensionless Biot (Bi) number where the heat transfer is limited by thermal convection. We demonstrate the NMR method for two simple geometries, a cylinder and a sphere, to experimentally determine the heat transfer coefficient (h) in two NMR imaging and spectroscopy systems through measuring three NMR parameters, the chemical shift, magnetization and spin self diffusion coefficient. PMID:18524523
Wind heat transfer coefficient in solar collectors in outdoor conditions
Kumar, Suresh; Mullick, S.C.
2010-06-15
Knowledge of wind heat transfer coefficient, h{sub w}, is required for estimation of upward losses from the outer surface of flat plate solar collectors/solar cookers. In present study, an attempt has been made to estimate the wind induced convective heat transfer coefficient by employing unglazed test plate (of size about 0.9 m square) in outdoor conditions. Experiments, for measurement of h{sub w}, have been conducted on rooftop of a building in the Institute campus in summer season for 2 years. The estimated wind heat transfer coefficient has been correlated against wind speed by linear regression and power regression. Experimental values of wind heat transfer coefficient estimated in present work have been compared with studies of other researchers after normalizing for plate length. (author)
Laser Measurement Of Convective-Heat-Transfer Coefficient
NASA Technical Reports Server (NTRS)
Porro, A. Robert; Hingst, Warren R.; Chriss, Randall M.; Seablom, Kirk D.; Keith, Theo G., Jr.
1994-01-01
Coefficient of convective transfer of heat at spot on surface of wind-tunnel model computed from measurements acquired by developmental laser-induced-heat-flux technique. Enables non-intrusive measurements of convective-heat-transfer coefficients at many points across surfaces of models in complicated, three-dimensional, high-speed flows. Measurement spot scanned across surface of model. Apparatus includes argon-ion laser, attenuator/beam splitter electronic shutter infrared camera, and subsystem.
Effect of impeller geometry on gas-liquid mass transfer coefficients in filamentous suspensions.
Dronawat, S N; Svihla, C K; Hanley, T R
1997-01-01
Volumetric gas-liquid mass transfer coefficients were measured in suspensions of cellulose fibers with concentrations ranging from 0 to 20 g/L. The mass transfer coefficients were measured using the dynamic method. Results are presented for three different combinations of impellers at a variety of gassing rates and agitation speeds. Rheological properties of the cellulose fibers were also measured using the impeller viscometer method. Tests were conducted in a 20 L stirred-tank fermentor and in 65 L tank with a height to diameter ratio of 3:1. Power consumption was measured in both vessels. At low agitation rates, two Rushton turbines gave 20% better performance than the Rushton and hydrofoil combination and 40% better performance than the Rushton and propeller combination for oxygen transfer. At higher agitation rates, the Rushton and hydrofoil combination gave 14 and 25% better performance for oxygen transfer than two Rushton turbines and the Rushton and hydrofoil combination, respectively. PMID:18576095
Overall Heat and Mass Transfer Coefficient of Water Vapor Adsorption
NASA Astrophysics Data System (ADS)
Hamamoto, Yoshinori; Mori, Hideo; Godo, Masazumi; Miura, Kunio; Watanabe, Yutaka; Ishizawa, Toshihiko; Takatsuka, Takeshi
A fundamental investigation was performed to develop a compact and simple desiccant ventilation unit which is one of the main components of a novel energy saving air-conditioning system. Water vapor in the air is adsorbed and/or desorbed to be controlled the humidity of supply air through a unit of an adsorbent rotor. A numerical simulation helps to understand the phenomena of heat and mass transfer in the rotor block. Overall transfer coefficients were estimated by performing both experiment and calculation. It was examined that the transient overall equivalent heat and mass transfer coefficient was not constant. It seems that both film fluid and diffusion resistance govern the coefficients in the block, and the influence of air flow on the time averaged coefficients is estimated by a considering the laminar forced convection from a flat plate. There is little difference of the coefficient between adsorption and desorption process. The correlation and fitting parameters are presented for prediction of the overall heat and mass transfer coefficients. The estimation accuracy was improved.
Measurement of airfoil heat transfer coefficients on a turbine stage
NASA Astrophysics Data System (ADS)
Dring, Robert P.; Blair, Michael F.; Joslyn, H. David
1986-10-01
The Primary basis for heat transfer analysis of turbine airfoils is experimental data obtained in linear cascades. These data were very valuable in identifying the major heat transfer and fluid flow features of a turbine airfoil. The first program objective is to obtain a detailed set of heat transfer coefficients along the midspan of a stator and a rotor in a rotating turbine stage. The data are to be compared to some standard analysis of blade boundary layer heat transfer which is in use today. A second program objective is to obtain a detailed set of heat transfer coefficients along the midspan of a stator located in the wake of an upstream turbine stage.
Overall Heat and Mass Transfer Coefficient of Water Vapor Adsorption
NASA Astrophysics Data System (ADS)
Hamamoto, Yoshinori; Mori, Hideo; Godo, Masazumi; Miura, Kunio; Watanabe, Yutaka; Ishizawa, Toshihiko; Takatsuka, Takeshi
A fundamental investigation was performed to develop a compact and simple desiccant ventilation unit which is one of the main components of a novel energy saving air-conditioning system. Water vapor in the air is adsorbed and/or desorbed to be controlled the humidity of supply air through a unit of an adsorbent packed bed. A numerical simulation helps to understand the phenomena of heat and mass transfer in the bed. Overall transfer coefficients of them as properties for the simulation were estimated by performing both experiment and calculation. It was clarified that the transient overall equivalent heat and mass transfer does not strongly depend on the air flow rate through the packed bed, the averaged equivalent mass transfer is governed by surface and pore diffusion in a particle of adsorbent at low flow rate. Moreover, the coefficient during the adsorption process is slightly larger than desorption. An equation of the overall mass transfer coefficient is derived. It shows five times as large as the value estimated by experiment. Therefore, the correlation and fitting parameters are presented for prediction of the overall heat and mass transfer coefficients. The estimation accuracy was improved.
Heat transfer coefficient in serpentine coolant passage for CCDTL
Leslie, P.; Wood, R.; Sigler, F.; Shapiro, A.; Rendon, A.
1998-12-31
A series of heat transfer experiments were conducted to refine the cooling passage design in the drift tubes of a coupled cavity drift tube linac (CCDTL). The experimental data were then compared to numerical models to derive relationships between heat transfer rates, Reynold`s number, and Prandtl number, over a range of flow rates. Data reduction consisted of axisymmetric finite element modeling where the heat transfer coefficients were modified to match the experimental data. Unfortunately, the derived relationship is valid only for this specific geometry of the test drift tube. Fortunately, the heat transfer rates were much better (approximately 2.5 times) than expected.
Determination of the heat transfer coefficients in transient heat conduction
NASA Astrophysics Data System (ADS)
Nho Hào, Dinh; Thanh, Phan Xuan; Lesnic, D.
2013-09-01
The determination of the space- or time-dependent heat transfer coefficient which links the boundary temperature to the heat flux through a third-kind Robin boundary condition in transient heat conduction is investigated. The reconstruction uses average surface temperature measurements. In both cases of the space- or time-dependent unknown heat transfer coefficient the inverse problems are nonlinear and ill posed. Least-squares penalized variational formulations are proposed and new formulae for the gradients are derived. Numerical results obtained using the nonlinear conjugate gradient method combined with a boundary element direct solver are presented and discussed.
Fermentation and oxygen transfer in microgravity
NASA Technical Reports Server (NTRS)
Dunlop, Eric H.
1989-01-01
The need for high rate oxygen transfer in microgravity for a Controlled Ecological Life Support System (CELSS) environment offers a number of difficulties and challenges. The use of a phase separated bioreactor appears to provide a way of overcoming these problems resulting in a system capable of providing high cell densities with rapid fermentation rates. Some of the key design elements are discussed.
Dissociation and Mass Transfer Coefficients for Ammonia Volatilization Models
Technology Transfer Automated Retrieval System (TEKTRAN)
Process-based models are being used to predict ammonia emissions from manure sources, but their accuracy has not been fully evaluated for cattle manure. Laboratory trials were conducted to measure the dissociation and mass transfer coefficients for ammonia volatilization from media of buffered ammon...
Design code verification of external heat transfer coefficients
NASA Astrophysics Data System (ADS)
Soechting, F. O.; Sharma, O. P.
1988-07-01
A comparative study is conducted for measured and predicted heat-transfer coefficients of air-cooled turbine blade airfoils. A modified version of the STAN-5 boundary layer code was used to obtain analytical predictions of the heat transfer levels for the cascade test conditions. A two-dimensional cascade test was conducted at engine-level Mach number and Reynolds number distributions in order to obtain baseline data that can be used with engine data in order to quantify the effects of environmental conditions on heat transfer levels and distributions.
CFD Extraction of Heat Transfer Coefficient in Cryogenic Propellant Tanks
NASA Technical Reports Server (NTRS)
Yang, H. Q.; West, Jeff
2015-01-01
Current reduced-order thermal model for cryogenic propellant tanks is based on correlations built for flat plates collected in the 1950's. The use of these correlations suffers from inaccurate geometry representation; inaccurate gravity orientation; ambiguous length scale; and lack of detailed validation. This study uses first-principles based CFD methodology to compute heat transfer from the tank wall to the cryogenic fluids and extracts and correlates the equivalent heat transfer coefficient to support reduced-order thermal model. The CFD tool was first validated against available experimental data and commonly used correlations for natural convection along a vertically heated wall. Good agreements between the present prediction and experimental data have been found for flows in laminar as well turbulent regimes. The convective heat transfer between the tank wall and cryogenic propellant, and that between the tank wall and ullage gas were then simulated. The results showed that the commonly used heat transfer correlations for either vertical or horizontal plate over-predict heat transfer rate for the cryogenic tank, in some cases by as much as one order of magnitude. A characteristic length scale has been defined that can correlate all heat transfer coefficients for different fill levels into a single curve. This curve can be used for the reduced-order heat transfer model analysis.
Measurement of airfoil heat transfer coefficients on a turbine stage
NASA Astrophysics Data System (ADS)
Dring, Robert P.; Blair, Michael F.; Joslyn, H. David
1987-10-01
A combined experimental and analytical program was conducted to examine the impact of a number of variables on the midspan heat transfer coefficients of the three airfoil rows in a one and one-half stage large scale turbine model. Variables included stator/rotor axial spacing, Reynolds number, turbine inlet turbulence, flow coefficient, relevant stator 1/stator 2 circumferential position, and rotation. Heat transfer data were acquired on the suction and pressure surfaces of the three airfoils. High density data were also acquired in the leading edge stagnation regions. Extensive documentation of the steady and unsteady aerodynamics was acquired. Finally, heat transfer data were compared with both a steady and an unsteady boundary layer analysis.
Determination of the heat transfer coefficients in porous media
Kim, L.V.
1994-06-01
The process of transpiration cooling is considered. Methods are suggested for estimating the volumetric coefficient of heat transfer with the use of a two-temperature model and the surface heat transfer coefficient at entry into a porous wall. The development of new technology under conditions of increasing heat loads puts the search for effective methods of heat transfer enhancement in the forefront of theoretical investigations. One of the promising trends in the solution of this problem is the use of porous materials (PM) in the elements of power units. For thermal protection against convective or radiative heat fluxes, the method of transpiration cooling is successfully used. The mechanism operative in the thermal protection involves the injection of a coolant through a porous medium to produce a screen over the contour of a body in a flow for removing heat energy from the skeleton of the porous material.
Study of acetic acid production by immobilized acetobacter cells: oxygen transfer
Ghommidh, C.; Navarro, J.M.; Durand, G.
1982-03-01
The immobilization of living Acetobacter cells by adsorption onto a large-surface-area ceramic support was studied in a pulsed flow reactor. The high oxygen transfer capability of the reactor enabled acetic acid production rates up to 10.4 g/L/h to be achieved. Using a simple mathematical model incorporating both internal and external mass transfer coefficients, it was shown that oxygen transfer in the microbial film controls the reactor productivity. (Refs. 10).
Heat transfer coefficients for staggered arrays of short pin fins
NASA Technical Reports Server (NTRS)
Vanfossen, G. J.
1981-01-01
Short pin fins are often used to increase that heat transfer to the coolant in the trailing edge of a turbine blade. Due primarily to limits of casting technology, it is not possible to manufacture pins of optimum length for heat transfer purposes in the trailing edge region. In many cases the pins are so short that they actually decrease the total heat transfer surface area compared to a plain wall. A heat transfer data base for these short pins is not available in the literature. Heat transfer coefficients on pin and endwall surfaces were measured for several staggered arrays of short pin fins. The measured Nusselt numbers when plotted versus Reynolds numbers were found to fall on a single curve for all surfaces tested. The heat transfer coefficients for the short pin fins (length to diameter ratios of 1/2 and 2) were found to be about a factor of two lower than data from the literature for longer pin arrays (length to diameter ratios of about 8).
Heat transfer coefficients for staggered arrays of short pin fins
NASA Technical Reports Server (NTRS)
Vanfossen, G. J.
1981-01-01
Short pin fins are often used to increase the heat transfer to the coolant in the trailing edge of a turbine blade. Due primarily to limits of casting technology, it is not possible to manufacture pins of optimum length for heat transfer purposes in the trailing edge region. In many cases the pins are so short that they actually decrease the total heat transfer surface area compared to a plain wall. A heat transfer data base for these short pins is not available in the literature. Heat transfer coefficients on pin and endwall surfaces were measured for several staggered arrays of short pin fins. The measured Nusselt numbers when plotted versus Reynolds numbers were found to fall on a single curve for all surfaces tested. The heat transfer coefficients for the short pin fins (length to diameter ratios of 1/2 and 2) were found to be about a factor of two lower than data from the literature for longer pin arrays (length to diameter ratios of about 8).
Bell, J H; Hand, L A
2005-04-21
The growth rate of a crystal in a supersaturated solution is limited by both reaction kinetics and the local concentration of solute. If the local mass transfer coefficient is too low, concentration of solute at the crystal-solution interface will drop below saturation, leading to a defect in the growing crystal. Here, mass transfer coefficients are calculated for a rotating crystal growing in a supersaturated solution of potassium diphosphate (KDP) in water. Since mass transfer is difficult to measure directly, the heat transfer coefficient of a scale model crystal in water is measured using temperature-sensitive paint (TSP). To the authors' knowledge this is the first use of TSP to measure temperatures in water. The corresponding mass transfer coefficient is then calculated using the Chilton- Colburn analogy. Measurements were made for three crystal sizes at two running conditions each. Running conditions include periodic reversals of rotation direction. Heat transfer coefficients were found to vary significantly both across the crystal faces and over the course of a rotation cycle, but not from one face to another. Mean heat transfer coefficients increased with both crystal size and rotation rate. Computed mass transfer coefficients were broadly in line with expectations from the full-scale crystal growth experiments. Additional experiments show that continuous rotation of the crystal results in about a 30% lower heat transfer compared to rotation with periodic reversals. The continuous rotation case also shows a periodic variation in heat transfer coefficient of about 15%, with a period about 1/20th of the rotation rate.
NASA Astrophysics Data System (ADS)
Keshavarz Moraveji, Mostafa; Ebrahimi Fakhari, Mona; Mohsenzadeh, Elmira; Davarnejad, Reza
2013-01-01
In this article, the influences of alcohols on the hydrodynamics and oxygen mass transfer characteristics in an airlift reactor equipped with packing were investigated. The hydrodynamic parameters and mass transfer coefficient in 1 % (v/v) aqueous solutions of four aliphatic alcohols were tested. It was concluded that alcohols addition increased gas holdup and gas-liquid mass transfer coefficient. The packing installation increased mass transfer coefficient, gas holdup and liquid circulation velocity, as well.
Convection heat transfer coefficients at convective drying of porous materials
Szentgyoergyi, S.; Toemoesy, L.; Molnar, O.
2000-07-01
Measurements proved that the convective heat transfer coefficient (h) has a larger value h{sub wet} at the constant drying rate period and after that it falls down to a minimum one: h{sub dry} in the equilibrium dried state. Measurements showed also that the heat of vaporization in the last phase of the falling drying rate period is far greater than it was in the constant drying rate period. The first measurements were made on a gypsum plate. Afterwards the authors carried out measurement research with fine glass powder and cement-perlite plate and determined h{sub wet} and h{sub dry} heat transfer coefficients as a function of Reynolds number. All of these measurements confirmed the conclusion that h{sub wet} is far greater than h{sub dry}.
BIOLOGICALLY ENHANCED OXYGEN TRANSFER IN THE ACTIVATED SLUDGE PROCESS (JOURNAL)
Biologically enhanced oxgyen transfer has been a hypothesis to explain observed oxygen transfer rates in activated sludge systems that were well above that predicted from aerator clean-water testing. The enhanced oxygen transfer rates were based on tests using BOD bottle oxygen ...
Mass transfer coefficients developed from the air gasification of wood pellets
Botts, J.W.
1998-07-01
A convertible updraft/downdraft, fixed-bed gasifier was used in the gasification of 3/8-inch diameter wood pellets. The test data was used to develop mass transfer coefficients and describe the gasification process for each gasifier configuration. The results show that the production of the principal combustion gases, i.e., hydrogen (H{sub c}), carbon monozide (CO), and methane (CH{sub 4}), varies directly as to their mass transfer coefficient: H{sub 2}, CO, and CH{sub 4} = k h{sub DA}. Factoring the Reynolds (Re{sub d}) and Schmidt (Sc) numbers with the influence of the noncombustible gases, i.e., nitrogen (N{sub 2}), oxygen (O{sub 2}), and carbon dioxide (CO{sub 2}), is used to define the mass transfer coefficients. The general form describing this joint variation is: H{sub 2}, CO, and CH{sub 4} = kx (the effect of the noncombustible gases) x Re x Sc where Re = Reynolds number and Sc = Schmidt number. The developments of these mass transfer coefficients are shown for updraft and downdraft gasification.
MASS TRANSFER COEFFICIENTS FOR A NON-NEWTONIAN FLUID AND WATER WITH AND WITHOUT ANTI-FOAM AGENTS
Leishear, R.
2009-09-09
Mass transfer rates were measured in a large scale system, which consisted of an 8.4 meter tall by 0.76 meter diameter column containing one of three fluids: water with an anti-foam agent, water without an anti-foam agent, and AZ101 simulant, which simulated a non-Newtonian nuclear waste. The testing contributed to the evaluation of large scale mass transfer of hydrogen in nuclear waste tanks. Due to its radioactivity, the waste was chemically simulated, and due to flammability concerns oxygen was used in lieu of hydrogen. Different liquids were used to better understand the mass transfer processes, where each of the fluids was saturated with oxygen, and the oxygen was then removed from solution as air bubbled up, or sparged, through the solution from the bottom of the column. Air sparging was supplied by a single tube which was co-axial to the column, the decrease in oxygen concentration was recorded, and oxygen measurements were then used to determine the mass transfer coefficients to describe the rate of oxygen transfer from solution. Superficial, average, sparging velocities of 2, 5, and 10 mm/second were applied to each of the liquids at three different column fill levels, and mass transfer coefficient test results are presented here for combinations of superficial velocities and fluid levels.
Rapid assessment of oxygen transfer impact for Corynebacterium glutamicum.
Käß, Friedrich; Prasad, Arjun; Tillack, Jana; Moch, Matthias; Giese, Heiner; Büchs, Jochen; Wiechert, Wolfgang; Oldiges, Marco
2014-12-01
Oxygen supply is crucial in industrial application of microbial systems, such as Corynebacterium glutamicum, but oxygen transfer is often neglected in early strain characterizations, typically done under aerobic conditions. In this work, a new procedure for oxygen transfer screening is presented, assessing the impact of maximum oxygen transfer conditions (OTRmax) within microtiter plate-based cultivation for enhanced throughput. Oxygen-dependent growth and productivity were characterized for C. glutamicum ATCC13032 and C. glutamicum DM1933 (lysine producer). Biomass and lysine product yield are affected at OTRmax below 14 mmol L(-1) h(-1) in a standardized batch process, but not by further increase of OTRmax above this threshold value indicating a reasonable tradeoff between power input and oxygen transfer capacity OTRmax. The described oxygen transfer screening allows comparative determination of metabolic robustness against oxygen transfer limitation and serves identification of potential problems or opportunities later created during scale-up. PMID:24981020
Heat transfer coefficient of nanofluids in minichannel heat sink
NASA Astrophysics Data System (ADS)
Utomo, Adi T.; Zavareh, Ashkan I. T.; Poth, Heiko; Wahab, Mohd; Boonie, Mohammad; Robbins, Phillip T.; Pacek, Andrzej W.
2012-09-01
Convective heat transfer in a heat sink consisting of rectangular minichannels and cooled with alumina and titania nanofluids has been investigated experimentally and numerically. Numerical simulations were carried out in a three dimensional domain employing homogeneous mixture model with effective thermo-physical properties of nanofluids. The predictions of base temperature profiles of the heat sink cooled with both water and nanofluids agree well with the experimental data. Experimental and numerical results show that the investigated nanofluids neither exhibits unusual enhancement of heat transfer coefficient nor decreases the heat sink base temperature. Although both nanofluids showed marginal thermal conductivity enhancements, the presence of solid nanoparticles lowers the specific heat capacity of nanofluids offseting the advantage of thermal conductivity enhancement. For all investigated flow rates, the Nusselt number of both nanofluids overlaps with that of water indicating that both nanofluids behave like single-phase fluids.
Oxygen Transfer Characteristics of Miniaturized Bioreactor Systems
Kirk, Timothy V; Szita, Nicolas
2013-01-01
Since their introduction in 2001 miniaturized bioreactor systems have made great advances in function and performance. In this article the dissolved oxygen (DO) transfer performance of submilliliter microbioreactors, and 1–10 mL minibioreactors was examined. Microbioreactors have reached kLa values of 460 h-1, and are offering instrumentation and some functionality comparable to production systems, but at high throughput screening volumes. Minibioreactors, aside from one 1,440 h-1 kLa system, have not offered as high rates of DO transfer, but have demonstrated superior integration with automated fluid handling systems. Microbioreactors have been typically limited to studies with E. coli, while minibioreactors have offered greater versatility in this regard. Further, mathematical relationships confirming the applicability of kLa measurements across all scales have been derived, and alternatives to fluorescence lifetime DO sensors have been evaluated. Finally, the influence on reactor performance of oxygen uptake rate (OUR), and the possibility of its real-time measurement have been explored. Biotechnol. Bioeng. 2013; 110: 1005–1019. © 2012 Wiley Periodicals, Inc. PMID:23280578
Ratios of transfer coefficients for radiocesium transport in ruminants
Assimakopoulos, P.A.; Ioannides, K.G.; Karamanis, D.
1995-09-01
A corollary of the multiple-compartment model for the transport of trace elements through animals was tested for cows, goats, and sheep. According to this corollary, for a given body {open_quotes}compartment{close_quotes} k of the animal (soft tissue, lung, liver, etc.), the ratio a(k)=f(k)/f(blood) of the transfer coefficients f, should exhibit similar values for physiologically similar animals. In order to verify this prediction, two experiments were performed at the Agricultural Research Station of Ioannina and at the facilities of Ria Pripyat in Pripyat, Ukranine. Eight animals in the first experiment and eighteen in the second were housed in individual pens and were artificially contaminated with a constant daily dose of radiocesium until equilibrium was reached. the animals were then sacrificed and transfer coefficients f(k) to twelve body {open_quotes}compartments{close_quotes} k were measured. These data were used to calculate the ratios a(k). The results were in accordance with predictions of the model and average values of a(k) were extracted for ruminants. It is concluded that these values may be employed for the prediction of animal contamination in any body compartment through the measurement of blood samples. 7 refs., 8 tabs.
Optimization of 2,3-butanediol production by Klebsiella oxytoca through oxygen transfer rate control
Beronio, P.B. Jr. . Amoco Research Center); Tsao, G.T. . Lab. of Renewable Resources Engineering)
1993-12-01
Production of 2,3-butanediol by Klebsiella oxytoca is influenced by the degree of oxygen limitation. During batch culture studies, two phases of growth are observed: energy-coupled growth, during which cell growth and oxygen supply are coupled; and, energy-uncoupled growth, which arises when the degree of oxygen limitation reaches a critical value. Optimal 2,3-butanediol productivity occurs during the energy-coupled growth phase. In this article, a control system which maintains the batch culture at a constant level of oxygen limitation in the energy-coupled growth regime has been designed. Control, which involves feedback control on the oxygen transfer coefficient, is achieved by continually increasing the partial pressure of oxygen in the feed gas, which in turn continually increases the oxygen transfer rate. Control has resulted in a balanced state of growth, a repression of ethanol formation, and an increase in 2,3-butanediol productivity of 18%.
Proton Transfer Rate Coefficient Measurements of Selected Volatile Organic Molecules
NASA Astrophysics Data System (ADS)
Brooke, G.; Popović, S.; Vušković, L.
2002-05-01
We have developed an apparatus based on the selected ion flow tube (SIFT)footnote D. Smith and N.G. Adams, Ads. At. Mol. Phys. 24, 1 (1987). that allows the study of proton transfer between various positive ions and volatile organic molecules. Reactions in the flow tube occur at pressures of approximately 300 mTorr, eliminating the requirement of thermal beam production. The proton donor molecule H_3O^+ has been produced using several types of electrical discharges in water vapor, such as a capacitively coupled RF discharge and a DC hollow cathode discharge. Presently we are developing an Asmussen-type microwave cavity discharge using the components of a standard microwave oven that has the advantages of simple design and operation, as well as low cost. We will be presenting the results of the microwave cavity ion source to produce H_3O^+, and compare it to the other studied sources. In addition, we will be presenting a preliminary measurement of the proton transfer rate coefficient in the reaction of H_3O^+ with acetone and methanol.
Nanoparticulate-catalyzed oxygen transfer processes
Hunt, Andrew T.; Breitkopf, Richard C.
2009-12-01
Nanoparticulates of oxygen transfer materials that are oxides of rare earth metals, combinations of rare earth metals, and combinations of transition metals and rare earth metals are used as catalysts in a variety of processes. Unexpectedly large thermal efficiencies are achieved relative to micron sized particulates. Processes that use these catalysts are exemplified in a multistage reactor. The exemplified reactor cracks C6 to C20 hydrocarbons, desulfurizes the hydrocarbon stream and reforms the hydrocarbons in the stream to produce hydrogen. In a first reactor stage the steam and hydrocarbon are passed through particulate mixed rare earth metal oxide to crack larger hydrocarbon molecules. In a second stage, the steam and hydrocarbon are passed through particulate material that desulfurizes the hydrocarbon. In a third stage, the hydrocarbon and steam are passed through a heated, mixed transition metal/rare earth metal oxide to reform the lower hydrocarbons and thereby produce hydrogen. Stages can be alone or combined. Parallel reactors can provide continuous reactant flow. Each of the processes can be carried out individually.
Experimentally Determined Heat Transfer Coefficients for Spacesuit Liquid Cooled Garments
NASA Technical Reports Server (NTRS)
Bue, Grant; Watts, Carly; Rhodes, Richard; Anchondo, Ian; Westheimer, David; Campbell, Colin; Vonau, Walt; Vogel, Matt; Conger, Bruce
2015-01-01
A Human-In-The-Loop (HITL) Portable Life Support System 2.0 (PLSS 2.0) test has been conducted at NASA Johnson Space Center in the PLSS Development Laboratory from October 27, 2014 to December 19, 2014. These closed-loop tests of the PLSS 2.0 system integrated with human subjects in the Mark III Suit at 3.7 psi to 4.3 psi above ambient pressure performing treadmill exercise at various metabolic rates from standing rest to 3000 BTU/hr (880 W). The bulk of the PLSS 2.0 was at ambient pressure but effluent water vapor from the Spacesuit Water Membrane Evaporator (SWME) and the Auxiliary Membrane Evaporator (Mini-ME), and effluent carbon dioxide from the Rapid Cycle Amine (RCA) were ported to vacuum to test performance of these components in flight-like conditions. One of the objectives of this test was to determine the heat transfer coefficient (UA) of the Liquid Cooling Garment (LCG). The UA, an important factor for modeling the heat rejection of an LCG, was determined in a variety of conditions by varying inlet water temperature, flowrate, and metabolic rate. Three LCG configurations were tested: the Extravehicular Mobility Unit (EMU) LCG, the Oceaneering Space Systems (OSS) LCG, and the OSS auxiliary LCG. Other factors influencing accurate UA determination, such as overall heat balance, LCG fit, and the skin temperature measurement, will also be discussed.
Miles, Robin; Havstad, Mark; LeBlanc, Mary; Golosker, Ilya; Chang, Allan; Rosso, Paul
2015-09-15
External heat transfer coefficients were measured around a surrogate Indirect inertial confinement fusion (ICF) based on the Laser Inertial Fusion Energy (LIFE) design target to validate thermal models of the LIFE target during flight through a fusion chamber. Results indicate that heat transfer coefficients for this target 25-50 W/m^{2}∙K are consistent with theoretically derived heat transfer coefficients and valid for use in calculation of target heating during flight through a fusion chamber.
Miles, Robin; Havstad, Mark; LeBlanc, Mary; Golosker, Ilya; Chang, Allan; Rosso, Paul
2015-09-15
External heat transfer coefficients were measured around a surrogate Indirect inertial confinement fusion (ICF) based on the Laser Inertial Fusion Energy (LIFE) design target to validate thermal models of the LIFE target during flight through a fusion chamber. Results indicate that heat transfer coefficients for this target 25-50 W/m2∙K are consistent with theoretically derived heat transfer coefficients and valid for use in calculation of target heating during flight through a fusion chamber.
Determination of heat transfer coefficients during solidification of a casting in a jet crystallizer
NASA Astrophysics Data System (ADS)
Borukhov, V. T.; Zayats, G. M.; Stetsenko, V. Yu.; Konovalov, R. V.
2012-01-01
The problem of determining heat transfer coefficients in thermal processes described by nonlinear initial boundary-value problems for heat conduction equations in a cylindrical coordinate system is considered subject to axial symmetry. An algorithm is suggested and program means are created for identifying heat transfer coefficients. A computational experiment on determining heat transfer coefficients for the AK12 alloy is carried out, and recommendations for selecting numerical calculation parameters have been developed.
Design of experiments for measuring heat-transfer coefficients with a lumped-parameter calorimeter
NASA Technical Reports Server (NTRS)
Vanfossen, G. J., Jr.
1975-01-01
A theoretical investigation was conducted to determine optimum experimental conditions for using a lumped-parameter calorimeter to measure heat-transfer coefficients and heating rates. A mathematical model of the transient temperature response of the calorimeter was used with the measured temperature response to predict the heat-transfer coefficient and the rate of heating. A sensitivity analysis was used to determine the optimum transient experiment for simultaneously measuring the heat addition during heating and the convective heat-transfer coefficient during heating and cooling of a lumped-parameter calorimeter. Optimum experiments were also designed for measuring the convective heat-transfer coefficient during both heating and cooling and cooling only.
NASA Astrophysics Data System (ADS)
Inoue, Gen; Yokoyama, Kouji; Ooyama, Junpei; Terao, Takeshi; Tokunaga, Tomomi; Kubo, Norio; Kawase, Motoaki
2016-09-01
The reduction of oxygen transfer resistance through porous components consisting of a gas diffusion layer (GDL), microporous layer (MPL), and catalyst layer (CL) is very important to reduce the cost and improve the performance of a PEFC system. This study involves a systematic examination of the relationship between the oxygen transfer resistance of the actual porous components and their three-dimensional structure by direct measurement with FIB-SEM and X-ray CT. Numerical simulations were carried out to model the properties of oxygen transport. Moreover, based on the model structure and theoretical equations, an approach to the design of new structures is proposed. In the case of the GDL, the binder was found to obstruct gas diffusion with a negative effect on performance. The relative diffusion coefficient of the MPL is almost equal to that of the model structure of particle packing. However, that of CL is an order of magnitude less than those of the other two components. Furthermore, an equation expressing the relative diffusion coefficient of each component can be obtained with the function of porosity. The electrical conductivity of MPL, which is lower than that of the carbon black packing, is considered to depend on the contact resistance.
Banerjee, S.; Hassan, Y.A.
1995-09-01
Condensation in the presence of noncondensible gases plays an important role in the nuclear industry. The RELAP5/MOD3 thermal hydraulic code was used to study the ability of the code to predict this phenomenon. Two separate effects experiments were simulated using this code. These were the Massachusetts Institute of Technology`s (MIT) Pressurizer Experiment, the MIT Single Tube Experiment. A new iterative approach to calculate the interface temperature and the degraded heat transfer coefficient was developed and implemented in the RELAP5/MOD3 thermal hydraulic code. This model employs the heat transfer simultaneously. This model was found to perform much better than the reduction factor approach. The calculations using the new model were found to be in much better agreement with the experimental values.
Effect of polymer additives on hydrodynamics and oxygen transfer in a bubble column bioreactor.
Kawase, Y
1993-01-01
The influence of polymer additives (polyethylene oxide and polyacrylamide) on the hydrodynamics and oxygen transfer in a bubble column bioreactor was examined. The addition of small amounts of these polymers has been known to cause significant drag reduction in turbulent flow circumstances. The gas hold-up was slightly decreased and the liquid-phase mixing was somewhat enhanced due to the addition of the polymers. The addition of polymer additives brought about a reduction of the volumetric oxygen transfer coefficient by about 40%. In dilute polymer solutions, large bubbles formed by bubble coalescence moved with high rise velocities in the presence of many small bubbles and the bubble size distributions were less uniform compared with those in water. The complicated changes in bubble hydrodynamic characteristics were examined to give possible explanations for oxygen transfer reduction. PMID:7763940
Transfer having a coupling coefficient higher than its active material
NASA Technical Reports Server (NTRS)
Lesieutre, George A. (Inventor); Davis, Christopher L. (Inventor)
2001-01-01
A coupling coefficient is a measure of the effectiveness with which a shape-changing material (or a device employing such a material) converts the energy in an imposed signal to useful mechanical energy. Device coupling coefficients are properties of the device and, although related to the material coupling coefficients, are generally different from them. This invention describes a class of devices wherein the apparent coupling coefficient can, in principle, approach 1.0, corresponding to perfect electromechanical energy conversion. The key feature of this class of devices is the use of destabilizing mechanical pre-loads to counter inherent stiffness. The approach is illustrated for piezoelectric and thermoelectrically actuated devices. The invention provides a way to simultaneously increase both displacement and force, distinguishing it from alternatives such as motion amplification, and allows transducer designers to achieve substantial performance gains for actuator and sensor devices.
Investigation of two-phase heat transfer coefficients of argon-freon cryogenic mixed refrigerants
NASA Astrophysics Data System (ADS)
Baek, Seungwhan; Lee, Cheonkyu; Jeong, Sangkwon
2014-11-01
Mixed refrigerant Joule Thomson refrigerators are widely used in various kinds of cryogenic systems these days. Although heat transfer coefficient estimation for a multi-phase and multi-component fluid in the cryogenic temperature range is necessarily required in the heat exchanger design of mixed refrigerant Joule Thomson refrigerators, it has been rarely discussed so far. In this paper, condensation and evaporation heat transfer coefficients of argon-freon mixed refrigerant are measured in a microchannel heat exchanger. A Printed Circuit Heat Exchanger (PCHE) with 340 μm hydraulic diameter has been developed as a compact microchannel heat exchanger and utilized in the experiment. Several two-phase heat transfer coefficient correlations are examined to discuss the experimental measurement results. The result of this paper shows that cryogenic two-phase mixed refrigerant heat transfer coefficients can be estimated by conventional two-phase heat transfer coefficient correlations.
NASA Technical Reports Server (NTRS)
Banan, Mohsen; Gray, Ross T.; Wilcox, William R.
1992-01-01
The heat transfer coefficient between a molten charge and its surroundings in a Bridgman furnace was experimentally determined using in-situ temperature measurement. The ampoule containing an isothermal melt was suddenly moved from a higher temperature zone to a lower temperature zone. The temperature-time history was used in a lumped-capacity cooling model to evaluate the heat transfer coefficient between the charge and the furnace. The experimentally determined heat transfer coefficient was of the same order of magnitude as the theoretical value estimated by standard heat transfer calculations.
A novel approach to determine the heat transfer coefficient in directional solidification furnaces
NASA Technical Reports Server (NTRS)
Banan, Mohsen; Gray, Ross T.; Wilcox, William R.
1990-01-01
The heat transfer coefficient between a molten charge and its surroundings in a Bridgman furnace was determined using an approach utilizing in-situ temperature measurement. The ampoule containing an isothermal melt was suddenly moved from a higher temperature zone to a lower temperature zone. The temperature-time history was used in a lumped-capacity cooling model to evaluate the heat transfer coefficient between the charge and the furnace. The experimentally determined heat transfer coefficient was of the same order of magnitude as the value estimated by standard heat transfer calculations.
The heat transfer coefficients of the heating surface of 300 MWe CFB boiler
NASA Astrophysics Data System (ADS)
Wu, Haibo; Zhang, Man; Lu, Qinggang; Sun, Yunkai
2012-08-01
A study of the heat transfer about the heating surface of three commercial 300 MWe CFB boilers was conducted in this work. The heat transfer coefficients of the platen heating surface, the external heat exchanger (EHE) and cyclone separator were calculated according to the relative operation data at different boiler loads. Moreover, the heat transfer coefficient of the waterwall was calculated by heat balance of the hot circuit of the CFB boiler. With the boiler capacity increasing, the heat transfer coefficients of these heating surface increases, and the heat transfer coefficient of the water wall is higher than that of the platen heating surface. The heat transfer coefficient of the EHE is the highest in high boiler load, the heat transfer coefficient of the cyclone separator is the lowest. Because the fired coal is different from the design coal in No.1 boiler, the ash content of the fired coal is much lower than that of the design coal. The heat transfer coefficients which calculated with the operation data are lower than the previous design value and that is the reason why the bed temperature is rather high during the boiler operation in No.1 boiler.
Small chamber tests were conducted to experimentally determine the overall mass transfer coefficient for pollutant emissions from still water under simulated indoor-residential or occupational-environmental conditions. Fourteen tests were conducted in small environmental chambers...
Support nanostructure boosts oxygen transfer to catalytically active platinum nanoparticles.
Vayssilov, Georgi N; Lykhach, Yaroslava; Migani, Annapaola; Staudt, Thorsten; Petrova, Galina P; Tsud, Nataliya; Skála, Tomáš; Bruix, Albert; Illas, Francesc; Prince, Kevin C; Matolín, Vladimír; Neyman, Konstantin M; Libuda, Jörg
2011-04-01
Interactions of metal particles with oxide supports can radically enhance the performance of supported catalysts. At the microscopic level, the details of such metal-oxide interactions usually remain obscure. This study identifies two types of oxidative metal-oxide interaction on well-defined models of technologically important Pt-ceria catalysts: (1) electron transfer from the Pt nanoparticle to the support, and (2) oxygen transfer from ceria to Pt. The electron transfer is favourable on ceria supports, irrespective of their morphology. Remarkably, the oxygen transfer is shown to require the presence of nanostructured ceria in close contact with Pt and, thus, is inherently a nanoscale effect. Our findings enable us to detail the formation mechanism of the catalytically indispensable Pt-O species on ceria and to elucidate the extraordinary structure-activity dependence of ceria-based catalysts in general. PMID:21423188
Support nanostructure boosts oxygen transfer to catalytically active platinum nanoparticles
NASA Astrophysics Data System (ADS)
Vayssilov, Georgi N.; Lykhach, Yaroslava; Migani, Annapaola; Staudt, Thorsten; Petrova, Galina P.; Tsud, Nataliya; Skála, Tomáš; Bruix, Albert; Illas, Francesc; Prince, Kevin C.; MatolíN, VladimíR.; Neyman, Konstantin M.; Libuda, Jörg
2011-04-01
Interactions of metal particles with oxide supports can radically enhance the performance of supported catalysts. At the microscopic level, the details of such metal-oxide interactions usually remain obscure. This study identifies two types of oxidative metal-oxide interaction on well-defined models of technologically important Pt-ceria catalysts: (1) electron transfer from the Pt nanoparticle to the support, and (2) oxygen transfer from ceria to Pt. The electron transfer is favourable on ceria supports, irrespective of their morphology. Remarkably, the oxygen transfer is shown to require the presence of nanostructured ceria in close contact with Pt and, thus, is inherently a nanoscale effect. Our findings enable us to detail the formation mechanism of the catalytically indispensable Pt-O species on ceria and to elucidate the extraordinary structure-activity dependence of ceria-based catalysts in general.
Charge transfer induced activity of graphene for oxygen reduction
NASA Astrophysics Data System (ADS)
Shen, Anli; Xia, Weijun; Zhang, Lipeng; Dou, Shuo; Xia, Zhenhai; Wang, Shuangyin
2016-05-01
Tetracyanoethylene (TCNE), with its strong electron-accepting ability, was used to dope graphene as a metal-free electrocatalyst for the oxygen reduction reaction (ORR). The charge transfer process was observed from graphene to TCNE by x-ray photoelectron spectroscopy and Raman characterizations. Our density functional theory calculations found that the charge transfer behavior led to an enhancement of the electrocatalytic activity for the ORR.
70. DETAIL OF OXYGEN TRANSFER PRESSURE GAUGE IN UPPER LEFT ...
70. DETAIL OF OXYGEN TRANSFER PRESSURE GAUGE IN UPPER LEFT CORNER OF SKID ON RIGHT IN CA-133-1-C-69 - Vandenberg Air Force Base, Space Launch Complex 3, Launch Pad 3 West, Napa & Alden Roads, Lompoc, Santa Barbara County, CA
A new interpretation of internal heat transfer coefficients of porous media
NASA Technical Reports Server (NTRS)
Dybbs, A.; Kar, K.; Groeneweg, M.; Ling, J. X.; Naraghi, M.
1984-01-01
The results of laser anemometer and flow visualization based fluid mechanics studies of porous media are used to obtain heat transfer coefficients for porous materials. Average pore flow Re ranging from 0.16-700 were examined. Darcy, inertial steady laminar, unsteady laminar and turbulent flow regimes were detected. A passage length model was devised to derive the heat transfer coefficient. Sample data from flows through porous metals composed of powders and fibers validated the passage length for Darcy and inertial flow regimes. Unsteady laminar and turbulent flow coefficients require the identification of new parameters.
Study on heat transfer coefficients during cooling of PET bottles for food beverages
NASA Astrophysics Data System (ADS)
Liga, Antonio; Montesanto, Salvatore; Mannella, Gianluca A.; La Carrubba, Vincenzo; Brucato, Valerio; Cammalleri, Marco
2016-08-01
The heat transfer properties of different cooling systems dealing with Poly-Ethylene-Terephthalate (PET) bottles were investigated. The heat transfer coefficient (Ug) was measured in various fluid dynamic conditions. Cooling media were either air or water. It was shown that heat transfer coefficients are strongly affected by fluid dynamics conditions, and range from 10 W/m2 K to nearly 400 W/m2 K. PET bottle thickness effect on Ug was shown to become relevant under faster fluid dynamics regimes.
Study on heat transfer coefficients during cooling of PET bottles for food beverages
NASA Astrophysics Data System (ADS)
Liga, Antonio; Montesanto, Salvatore; Mannella, Gianluca A.; La Carrubba, Vincenzo; Brucato, Valerio; Cammalleri, Marco
2015-08-01
The heat transfer properties of different cooling systems dealing with Poly-Ethylene-Terephthalate (PET) bottles were investigated. The heat transfer coefficient (Ug) was measured in various fluid dynamic conditions. Cooling media were either air or water. It was shown that heat transfer coefficients are strongly affected by fluid dynamics conditions, and range from 10 W/m2 K to nearly 400 W/m2 K. PET bottle thickness effect on Ug was shown to become relevant under faster fluid dynamics regimes.
Measurement of local connective heat transfer coefficients of four ice accretion shapes
NASA Technical Reports Server (NTRS)
Smith, M. E.; Armilli, R. V.; Keshock, E. G.
1984-01-01
In the analytical study of ice accretions that form on aerodynamic surfaces (airfoils, engine inlets, etc.) it is often necessary to be able to calculate convective heat transfer rates. In order to do this, local convective heat transfer coefficients for the ice accretion shapes must be known. In the past, coefficients obtained for circular cylinders were used as an approximation to the actual coefficients since no better information existed. The purpose of this experimental study was to provide local convective heat transfer coefficients for four shapes that represent ice accretions. The shapes were tested with smooth and rough surfaces. The experimental method chosen was the thin-skin heat rate technique. Using this method local Nusselt numbers were determined for the ice shapes. In general it was found that the convective heat transfer was higher in regions where the model's surfaces were convex and lower in regions where the model's surfaces were concave. The effect of roughness was to increase the heat transfer in the high heat transfer regions by approximately 100% while little change was apparent in the low heat transfer regions.
Ihlefeld, Jon F.; Brown-Shaklee, Harlan James; Sharma, Peter Anand
2015-04-28
The transport properties of ceramic materials strongly depend on oxygen activity, which is tuned by changing the partial oxygen pressure (pO_{2}) prior to and during measurement. Within, we describe an instrument for highly stable measurements of Seebeck coefficient and electrical resistivity at temperatures up to 1300 K with controlled oxygen partial pressure. An all platinum construction is used to avoid potential materials instabilities that can cause measurement drift. Two independent heaters are employed to establish a small temperature gradient for Seebeck measurements, while keeping the average temperature constant and avoiding errors associated with pO_{2}-induced drifts in thermocouple readings. Oxygen equilibrium is monitored using both an O_{2} sensor and the transient behavior of the resistance as a proxy. A pO_{2} range of 10^{-25}–10^{0} atm can be established with appropriate gas mixtures. Seebeck measurements were calibrated against a high purity platinum wire, Pt/Pt–Rh thermocouple wire, and a Bi_{2}Te3 Seebeck coefficient Standard Reference Material. To demonstrate the utility of this instrument for oxide materials we present measurements as a function of pO_{2} on a 1 % Nb-doped SrTiO_{3} single crystal, and show systematic changes in properties consistent with oxygen vacancy defect chemistry. Thus, an approximately 11% increase in power factor over a pO_{2} range of 10^{-19}–10^{-8} atm at 973 K for the donor-doped single crystals is observed.
Ihlefeld, Jon F.; Brown-Shaklee, Harlan James; Sharma, Peter Anand
2015-04-28
The transport properties of ceramic materials strongly depend on oxygen activity, which is tuned by changing the partial oxygen pressure (pO2) prior to and during measurement. Within, we describe an instrument for highly stable measurements of Seebeck coefficient and electrical resistivity at temperatures up to 1300 K with controlled oxygen partial pressure. An all platinum construction is used to avoid potential materials instabilities that can cause measurement drift. Two independent heaters are employed to establish a small temperature gradient for Seebeck measurements, while keeping the average temperature constant and avoiding errors associated with pO2-induced drifts in thermocouple readings. Oxygen equilibriummore » is monitored using both an O2 sensor and the transient behavior of the resistance as a proxy. A pO2 range of 10-25–100 atm can be established with appropriate gas mixtures. Seebeck measurements were calibrated against a high purity platinum wire, Pt/Pt–Rh thermocouple wire, and a Bi2Te3 Seebeck coefficient Standard Reference Material. To demonstrate the utility of this instrument for oxide materials we present measurements as a function of pO2 on a 1 % Nb-doped SrTiO3 single crystal, and show systematic changes in properties consistent with oxygen vacancy defect chemistry. Thus, an approximately 11% increase in power factor over a pO2 range of 10-19–10-8 atm at 973 K for the donor-doped single crystals is observed.« less
Lewis Acid Coupled Electron Transfer of Metal-Oxygen Intermediates.
Fukuzumi, Shunichi; Ohkubo, Kei; Lee, Yong-Min; Nam, Wonwoo
2015-12-01
Redox-inactive metal ions and Brønsted acids that function as Lewis acids play pivotal roles in modulating the redox reactivity of metal-oxygen intermediates, such as metal-oxo and metal-peroxo complexes. The mechanisms of the oxidative CH bond cleavage of toluene derivatives, sulfoxidation of thioanisole derivatives, and epoxidation of styrene derivatives by mononuclear nonheme iron(IV)-oxo complexes in the presence of triflic acid (HOTf) and Sc(OTf)3 have been unified as rate-determining electron transfer coupled with binding of Lewis acids (HOTf and Sc(OTf)3 ) by iron(III)-oxo complexes. All logarithms of the observed second-order rate constants of Lewis acid-promoted oxidative CH bond cleavage, sulfoxidation, and epoxidation reactions of iron(IV)-oxo complexes exhibit remarkably unified correlations with the driving forces of proton-coupled electron transfer (PCET) and metal ion-coupled electron transfer (MCET) in light of the Marcus theory of electron transfer when the differences in the formation constants of precursor complexes were taken into account. The binding of HOTf and Sc(OTf)3 to the metal-oxo moiety has been confirmed for Mn(IV) -oxo complexes. The enhancement of the electron-transfer reactivity of metal-oxo complexes by binding of Lewis acids increases with increasing the Lewis acidity of redox-inactive metal ions. Metal ions can also bind to mononuclear nonheme iron(III)-peroxo complexes, resulting in acceleration of the electron-transfer reduction but deceleration of the electron-transfer oxidation. Such a control on the reactivity of metal-oxygen intermediates by binding of Lewis acids provides valuable insight into the role of Ca(2+) in the oxidation of water to dioxygen by the oxygen-evolving complex in photosystem II. PMID:26404482
Electrocatalysis of anodic and cathodic oxygen-transfer reactions
Wels, B.R.
1990-09-21
The electrocatalysis of oxygen-transfer reactions is discussed in two parts. In Part I, the reduction of iodate (IO{sub 3}{sup {minus}}) is examined as an example of cathodic oxygen transfer. On oxide-covered Pt electrodes (PtO), a large cathodic current is observed in the presence of IO{sub 3}{sup {minus}} to coincide with the reduction of PtO. The total cathodic charge exceeds the amount required for reduction of PtO and IO{sub 3}{sup {minus}} to produce an adsorbed product. An electrocatalytic link between reduction of IO{sub 3}{sup {minus}} and reduction of PtO is indicated. In addition, on oxide-free Pt electrodes, the reduction of IO{sub 3}{sup {minus}} is determined to be sensitive to surface treatment. The electrocatalytic oxidation of CN{sup {minus}} is presented as an example of anodic oxygen transfer in Part II. The voltametric response of CN{sup {minus}} is virtually nonexistent at PbO{sub 2} electrodes. The response is significantly improved by doping PbO{sub 2} with Cu. Cyanide is also oxidized effectively at CuO-film electrodes. Copper is concluded to serve as an adsorption site for CN{sup {minus}}. It is proposed that an oxygen tunneling mechanism comparable to electron tunneling does not occur at the electrode-solution interface. The adsorption of CN{sup {minus}} is therefore considered to be a necessary prerequisite for oxygen transfer. 201 refs., 23 figs., 2 tabs.
Ab initio calculation of oxygen self-diffusion coefficient in uranium dioxide UO2
NASA Astrophysics Data System (ADS)
Dorado, Boris; Garcia, Philippe; Torrent, Marc
Uranium dioxide UO2 is the most widely used nuclear fuel worldwide and its atomic transport properties are relevant to practically all engineering aspects of the material. Although transport properties have already been studied in UO2 by means of first-principles calculations, the ab initio determination of self-diffusion coefficients has up to now remained unreachable because the relevant computational tools were neither available or adapted. The present work reports our results related to the ab initio calculation of the oxygen self-diffusion coefficient in UO2. We first determine the Gibbs free energies of formation of oxygen charged defects by calculating both the electronic and vibrational (hence entropic) contributions. Then, we use the transition state theory in order to compute the effective jump frequency of the defects, which in turn provides us with the value of the pre-exponential factor. The results are compared to self-diffusion data obtained experimentally with a careful monitoring of the relevant thermodynamic conditions (oxygen partial pressure, temperature, impurity content).
Development of a biomimetic microfluidic oxygen transfer device.
Gimbel, A A; Flores, E; Koo, A; García-Cardeña, G; Borenstein, J T
2016-08-16
Blood oxygenators provide crucial life support for patients suffering from respiratory failure, but their use is severely limited by the complex nature of the blood circuit and by complications including bleeding and clotting. We have fabricated and tested a multilayer microfluidic blood oxygenation prototype designed to have a lower blood prime volume and improved blood circulation relative to current hollow fiber cartridge oxygenators. Here we address processes for scaling the device toward clinically relevant oxygen transfer rates while maintaining a low prime volume of blood in the device, which is required for clinical applications in cardiopulmonary support and ultimately for chronic use. Approaches for scaling the device toward clinically relevant gas transfer rates, both by expanding the active surface area of the network of blood microchannels in a planar layer and by increasing the number of microfluidic layers stacked together in a three-dimensional device are addressed. In addition to reducing prime volume and enhancing gas transfer efficiency, the geometric properties of the microchannel networks are designed to increase device safety by providing a biomimetic and physiologically realistic flow path for the blood. Safety and hemocompatibility are also influenced by blood-surface interactions within the device. In order to further enhance device safety and hemocompatibility, we have demonstrated successful coating of the blood flow pathways with human endothelial cells, in order to confer the ability of the endothelium to inhibit coagulation and thrombus formation. Blood testing results provide confirmation of fibrin clot formation in non-endothelialized devices, while negligible clot formation was documented in cell-coated devices. Gas transfer testing demonstrates that the endothelial lining does not reduce the transfer efficiency relative to acellular devices. This process of scaling the microfluidic architecture and utilizing autologous cells to
NASA Technical Reports Server (NTRS)
Schacht, R. L.; Quentmeyer, R. J.
1973-01-01
An experimental investigation was conducted to determine the coolant-side, heat transfer coefficients for a liquid cooled, hydrogen-oxygen rocket thrust chamber. Heat transfer rates were determined from measurements of local hot gas wall temperature, local coolant temperature, and local coolant pressure. A correlation incorporating an integration technique for the transport properties needed near the pseudocritical temperature of liquid hydrogen gives a satisfactory prediction of hot gas wall temperatures.
Calculation of heat transfer coefficients at the ingot surface during DC casting
Kuwana, K.; Viswanathan, S.; Clark, John A, III; Sabau, A.; Hassan, M.; Saito, K.; Das, S.
2005-02-01
Surface heat transfer coefficients representing the various regimes of water cooling during the Direct Chill (DC) casting of aluminum 3004 alloy ingots have been calculated using the inverse heat transfer technique. ProCAST, a commercial casting simulation package, which includes heat transfer, fluid flow, solidification, and inverse heat transfer, was used for this effort. Thermocouple data from an experimental casting run, and temperature-dependent thermophysical properties of the alloy were used in the calculation. The use of a structured vs. unstructured mesh was evaluated. The calculated effective heat transfer coefficient, which is a function of temperature and time, covers three water cooling regimes, i.e., convection, nucleate boiling, and film boiling, and the change of water flow rate with time.
Watkis, Andrew; Hueting, Rebekka; Sørensen, Thomas Just; Tropiano, Manuel; Faulkner, Stephen
2015-11-01
Pyrene-appended ytterbium complexes have been prepared using Ugi reactions to vary the chromophore-lanthanide separation. Formation of the ytterbium(iii) excited state is sensitised via both the singlet and triplet excited states of the chromophore. Energy transfer from the latter is relatively slow, and gives rise to oxygen-dependent luminescence. PMID:26346499
Oxygen diffusion coefficient and solubility in a new proton exchange membrane
Haug, A.T.; White, R.E.
2000-03-01
The electrochemical monitoring technique is used to measure the solubility and the diffusion coefficient of oxygen in a new proton exchange membrane that is being developed by Cape Cod Research, Inc., Using the method of least squares, the data were fit to an analytical solution of Fick's second law to determine D and c{sub 0}. Values of 0.40 x 10{sup {minus}6}cm{sup 2}/s and 4.98 x 10{sup {minus}6} mol/cm{sup 3} were obtained for the diffusion coefficient and solubility, respectively, of the Cape Cod membrane. These values are significantly less than those of Nafion 117 tested under identical conditions.
Global rate coefficients for ionization and recombination of carbon, nitrogen, oxygen, and argon
Annaloro, Julien; Morel, Vincent; Bultel, Arnaud; Omaly, Pierre
2012-07-15
The flow field modeling of planetary entry plasmas, laser-induced plasmas, inductively coupled plasmas, arcjets, etc., requires to use Navier-Stokes codes. The kinetic mechanisms implemented in these codes involve global (effective) rate coefficients. These rate coefficients result from the excited states coupling during a quasi-steady state. In order to obtain these global rate coefficients over a wide electron temperature (T{sub e}) range for ionization and recombination of carbon, nitrogen, oxygen, and argon, the behavior of their excited states is investigated using a zero-dimensional (time-dependent) code. The population number densities of these electronic states are considered as independent species. Their relaxation is studied within the range 3000 K{<=}T{sub e}{<=}20 000 K and leads to the determination of the ionization (k{sub i}) and recombination (k{sub r}) global rate coefficients. Comparisons with existing data are performed. Finally, the ratio k{sub i}/k{sub r} is compared with the Saha equilibrium constant. This ratio increases more rapidly than the equilibrium constant for T{sub e}>15 000 K.
Measurement of impingement heat transfer coefficient on a HIPS liner sheet
Fu, X.
1999-07-01
A test facility was built to measure the impingement convective heat transfer coefficient for a high impact polystyrene (HIPS) liner sheet which was heated by an array of air slot nozzles. A HIPS liner sheet having a thickness of 6 mm is a typical material used for inside shells of refrigerators. The nozzle geometry was optimally designed. The pressure drops through the nozzles, the velocities at the exits of nozzles, temperatures on the sheet surface and in the sheet center were measured. The impingement heat transfer coefficient on the sheet was determined using the measured sheet temperature history in conjunction with an inverse analysis which was based on a one-dimensional transient heat conduction model. The effect of air flow rate ranging from 8 to 32 m/s on the heat transfer coefficient is discussed.
NASA Astrophysics Data System (ADS)
Oralsyn, Gulaym
2016-08-01
We study an inverse coefficient problem for a model equation for one-dimensional heat transfer with a preservation of medium temperature. It is needed (together with finding its solution) to find time dependent unknown coefficient of the equation. So, for this inverse problem, existence of an unique generalized solution is proved. The main difficulty of the considered problems is that the eigenfunction system of the corresponding boundary value problems does not have the basis property.
CFD simulation of simultaneous monotonic cooling and surface heat transfer coefficient
NASA Astrophysics Data System (ADS)
Mihálka, Peter; Matiašovský, Peter
2016-07-01
The monotonic heating regime method for determination of thermal diffusivity is based on the analysis of an unsteady-state (stabilised) thermal process characterised by an independence of the space-time temperature distribution on initial conditions. At the first kind of the monotonic regime a sample of simple geometry is heated / cooled at constant ambient temperature. The determination of thermal diffusivity requires the determination rate of a temperature change and simultaneous determination of the first eigenvalue. According to a characteristic equation the first eigenvalue is a function of the Biot number defined by a surface heat transfer coefficient and thermal conductivity of an analysed material. Knowing the surface heat transfer coefficient and the first eigenvalue the thermal conductivity can be determined. The surface heat transport coefficient during the monotonic regime can be determined by the continuous measurement of long-wave radiation heat flow and the photoelectric measurement of the air refractive index gradient in a boundary layer. CFD simulation of the cooling process was carried out to analyse local convective and radiative heat transfer coefficients more in detail. Influence of ambient air flow was analysed. The obtained eigenvalues and corresponding surface heat transfer coefficient values enable to determine thermal conductivity of the analysed specimen together with its thermal diffusivity during a monotonic heating regime.
NASA Technical Reports Server (NTRS)
Schey, Oscar W; Rollin, Vern G
1936-01-01
This report presents the results of an investigation to determine the effect of baffles on the temperature distribution and the heat-transfer coefficient of finned cylinders. The tests were conducted in a 30-inch wind tunnel on electrically heated cylinders with fins of 0.25 and 0.31 inch pitch. The results of these tests showed that the use of integral baffles gave a reduction of 31.9 percent in the rear wall temperatures and an increase of 54.2 percent in the heat transfer coefficient as compared with a cylinder without baffles.
Measuring the heat-transfer coefficient of nanofluid based on copper oxide in a cylindrical channel
NASA Astrophysics Data System (ADS)
Guzei, D. V.; Minakov, A. V.; Rudyak, V. Ya.; Dekterev, A. A.
2014-03-01
The heat-transfer coefficient of nanofluid during its flow in a cylindrical channel is studied experimentally. The studied nanofluid was prepared based on distilled water and CuO nanoparticles. Nanoparticle concentration varied in the range from 0.25 to 2% in the volume. The nanofluid was stabilized using a xanthane gum biopolymer the mass concentration of which did not exceed 0.03%. Considerable intensification of heat transfer was found. The nanofluid appeared to be Newtonian when particle concentrations exceeded 0.25%. Estimates for rheological parameters of the nanofluid and thermal conductivity coefficient have been obtained.
Heat/Mass Transfer Coefficients of an Absorber in Absorption Refrigeration System
NASA Astrophysics Data System (ADS)
Fujita, Isamu; Hihara, Eiji
This paper presents a new method to calculate heat and mass transfer coefficients applicable to the vertical tube or plate type absorber of absorption refrigeration system. Conventional method for calculating the coefficients using logarithmic mean temperature/ concentration differences is criticized for its lacking in the theoretical rationality and usually giving untrue values except some limited situations such that temperature of the solution can be assumed to change linearly along the heat transfer surface. The newly introduced method, which is intended to overcome this difficulty, is verified by numerical simulation and is accompanied by an example applied to the experimental results.
NASA Astrophysics Data System (ADS)
Piasecka, Magdalena; Strąk, Kinga
2016-03-01
The aim of the paper is to estimate effect of the heating surface enhancement on FC-72 flow boiling heat transfer for a vertical minichannel 1.7 mm deep, 24 mm wide and 360 mm long. Two types of enhanced heating surfaces were used: one with minicavities distributed unevenly, and the other with capillary metal fibrous structure. It was to measure temperature field on the plain side of the heating surface by means of the infrared thermography and to observe the two-phase flow patterns on the enhanced foil side. The paper analyses mainly the impact of the microstructured heating surface on the heat transfer coefficient. The results are presented as heat transfer coefficient dependences on the distance along the minichannel length. The data obtained using two types of enhanced heating surfaces in experiments was compared with the data when smooth foil as the heating surface was used. The highest local values of heat transfer coefficient were obtained using enhanced foil with minicavities - in comparison to other cases. Local values of heat transfer coefficient received for capillary fibrous structure were the lowest, even compared with data obtained for smooth foil. Probably this porous structure caused local flow disturbances.
2013-01-01
Background Among disposable bioreactor systems, cylindrical orbitally shaken bioreactors show important advantages. They provide a well-defined hydrodynamic flow combined with excellent mixing and oxygen transfer for mammalian and plant cell cultivations. Since there is no known universal correlation between the volumetric mass transfer coefficient for oxygen kLa and relevant operating parameters in such bioreactor systems, the aim of this current study is to experimentally determine a universal kLa correlation. Results A Respiration Activity Monitoring System (RAMOS) was used to measure kLa values in cylindrical disposable shaken bioreactors and Buckingham’s π-Theorem was applied to define a dimensionless equation for kLa. In this way, a scale- and volume-independent kLa correlation was developed and validated in bioreactors with volumes from 2 L to 200 L. The final correlation was used to calculate cultivation parameters at different scales to allow a sufficient oxygen supply of tobacco BY-2 cell suspension cultures. Conclusion The resulting equation can be universally applied to calculate the mass transfer coefficient for any of seven relevant cultivation parameters such as the reactor diameter, the shaking frequency, the filling volume, the viscosity, the oxygen diffusion coefficient, the gravitational acceleration or the shaking diameter within an accuracy range of +/− 30%. To our knowledge, this is the first kLa correlation that has been defined and validated for the cited bioreactor system on a bench-to-pilot scale. PMID:24289110
Convective and radiative heat transfer coefficients for individual human body segments.
de Dear, R J; Arens, E; Hui, Z; Oguro, M
1997-05-01
Human thermal physiological and comfort models will soon be able to simulate both transient and spatial inhomogeneities in the thermal environment. With this increasing detail comes the need for anatomically specific convective and radiative heat transfer coefficients for the human body. The present study used an articulated thermal manikin with 16 body segments (head, chest, back, upper arms, forearms, hands, pelvis, upper legs, lower legs, feet) to generate radiative heat transfer coefficients as well as natural- and forced-mode convective coefficients. The tests were conducted across a range of wind speeds from still air to 5.0 m/s, representing atmospheric conditions typical of both indoors and outdoors. Both standing and seated postures were investigated, as were eight different wind azimuth angles. The radiative heat transfer coefficient measured for the whole-body was 4.5 W/m2 per K for both the seated and standing cases, closely matching the generally accepted whole-body value of 4.7 W/m2 per K. Similarly, the whole-body natural convection coefficient for the manikin fell within the mid-range of previously published values at 3.4 and 3.3 W/m2 per K when standing and seated respectively. In the forced convective regime, heat transfer coefficients were higher for hands, feet and peripheral limbs compared to the central torso region. Wind direction had little effect on convective heat transfers from individual body segments. A general-purpose forced convection equation suitable for application to both seated and standing postures indoors was hc = 10.3v0.6 for the whole-body. Similar equations were generated for individual body segments in both seated and standing postures. PMID:9195861
Technology Transfer Automated Retrieval System (TEKTRAN)
An empirical correlation of volumetric mass transfer coefficient was developed for a pilot scale internal-loop rectangular airlift bioreactor that was designed for biotechnology. The empirical correlation combines classic turbulence theory, Kolmogorov’s isotropic turbulence theory with Higbie’s pen...
Development of particulate matter transfer coefficients using a three-dimensional air quality model
Seigneur, C.; Tonne, C.; Vijayaraghavan, K.; Pai, P.; Levin, L.
1999-07-01
Air quality model simulations constitute an effective approach to develop source-receptor relationships (so-called transfer coefficients in the risk analysis framework) because a significant fraction of particulate matter (particularly PM{sub 2.5}) is secondary and, therefore, depends on the atmospheric chemistry of the airshed. These source-receptor relationships can be made specific to source regions and major pollutants. In this study, the authors have used a comprehensive three-dimensional air quality model for PM (SAQM-AERO) to generate episodic transfer coefficients for several source regions in the Los Angeles basin (i.e., surface coastal region, elevated coastal region, central basin, and downwind region). Transfer coefficients were developed by conducting PM air quality simulations with reduced emissions of one of the four precursors (i.e., primary PM, SO{sub 2}, NO{sub x}, and VOC) from each source region. The authors have also compared the transfer coefficients generated from explicit modeling with those based on expert judgment, which were obtained by integrating information from the development of the baseline simulation and across-the-board emission reduction simulations.
NASA Astrophysics Data System (ADS)
Luo, Benyi; Lu, Yigang
2008-10-01
Based on several hypotheses about the process of supercritical carbon dioxide extraction, the onflow around the solute granule is figured out by the Navier-Stocks equation. In combination with the Higbie’s solute infiltration model, the link between the mass-transfer coefficient and the velocity of flow is found. The mass-transfer coefficient with the ultrasonical effect is compared with that without the ultrasonical effect, and then a new parameter named the ultrasonic-enhanced factor of mass-transfer coefficient is brought forward, which describes the mathematical model of the supercritical carbon dioxide extraction process enhanced by ultrasonic. The model gives out the relationships among the ultrasonical power, the ultrasonical frequency, the radius of solute granule and the ultrasonic-enhanced factor of mass-transfer coefficient. The results calculated by this model fit well with the experimental data, including the extraction of Coix Lacryma-jobi Seed Oil (CLSO) and Coix Lacryma-jobi Seed Ester (CLSE) from coix seeds and the extraction of Eicosapentaenoic Acid (EPA) and Docosahexaenoic Acid (DHA) from the alga by means of the ultrasonic-enhanced supercritical carbon dioxide extraction (USFE) and the supercritical carbon dioxide extraction (SFE) respectively. This proves the rationality of the ultrasonic-enhanced factor model. The model provides a theoretical basis for the application of ultrasonic-enhanced supercritical fluid extraction technique.
Measurements of pressure drop, heat transfer coefficient and critical energy of a bundle conductor
Junghans, D.
1981-09-01
Friction factor, saturation temperature, heat transfer coefficient and critical energy of an eight strand bundle conductor were measured in the test facility SULTAN at SIN in Switzerland. The measured values of the critical energy are in good agreement with those calculated by the computer code LONSA. 10 refs.
Simpson, R; Abakarov, A; Almonacid, S; Teixeira, A
2008-10-01
This study attempts to examine the significance of recent research that has focused on efforts to estimate values for global and surface heat transfer coefficients under forced convection heating induced by end-over-end rotation in retorting of canned peas in brine. The study confirms the accuracy of regression analysis used to predict values for heat transfer coefficients as a function of rotating speed and headspace, and uses them to predict values over a range of process conditions, which make up the search domain for process optimization. These coefficients were used in a convective heat transfer model to establish a range of lethality-equivalent retort temperature-time processes for various conditions of retort temperature, rotating speed, and headspace. Then, they were coupled with quality factor kinetics to predict the final volume average and surface quality retention resulting from each process and to find the optimal thermal process conditions for canned fresh green peas. Results showed that maximum quality retention (surface and volume average retention) was achieved with the shortest possible process time (made possible with highest retort temperature), and reached the similar level in all cases with small difference between surface and volume average quality retention. The highest heat transfer coefficients (associated with maximum rotating speed and headspace) showed a 10% reduction in process time over that required with minimum rotating speed and headspace. The study concludes with a discussion of the significance of these findings and degree to which they were expected. PMID:19019110
Heat transfer coefficients in two-dimensional Yukawa systems (numerical simulations)
NASA Astrophysics Data System (ADS)
Khrustalyov, Yu. V.; Vaulina, O. S.
2013-05-01
New data on heat transfer in two-dimensional Yukawa systems have been obtained. The results of a numerical study of the thermal conductivity for equilibrium systems with parameters close to the conditions of laboratory experiments in dusty plasma are presented. The Green-Kubo relations are used to calculate the heat transfer coefficients. The influence of dissipation (internal friction) on the heat transfer processes in nonideal systems is studied. New approximations are proposed for the thermal conductivity and diffusivity for nonideal dissipative systems. The results obtained are compared with the existing experimental and numerical data.
NASA Astrophysics Data System (ADS)
Taler, Dawid
2012-09-01
This paper presents a numerical method for determining heat transfer coefficients in cross-flow heat exchangers with extended heat exchange surfaces. Coefficients in the correlations defining heat transfer on the liquid- and air-side were determined using a nonlinear regression method. Correlation coefficients were determined from the condition that the sum of squared liquid and air temperature differences at the heat exchanger outlet, obtained by measurements and those calculated, achieved minimum. Minimum of the sum of the squares was found using the Levenberg-Marquardt method. The uncertainty in estimated parameters was determined using the error propagation rule by Gauss. The outlet temperature of the liquid and air leaving the heat exchanger was calculated using the analytical model of the heat exchanger.
Jimenez, Mélanie; Dietrich, Nicolas; Grace, John R; Hébrard, Gilles
2014-07-01
Powerful techniques, based on the Planar Laser Induced Fluorescence (PLIF) technique, are deployed to locally visualize and quantify the impact of surfactants in wastewaters on hydrodynamics and oxygen mass transfer. Bubble diameter, aspect ratio, rise velocity, contamination angle, as well as flux, flux density, liquid side mass transfer and diffusion coefficients of transferred oxygen are determined based on these techniques applied in the wake of rising bubbles of diameter 1 mm and through planar gas/liquid interfaces. The initial experiments were performed in demineralized water containing small amounts of surfactant. Different concentrations of surfactant were added to finally reach the Critical Micelle Concentration (CMC). Bubbles have classically been found to be more spherical with a reduced rise velocity in the presence of surfactants up to the CMC. Above the CMC, these hydrodynamic characteristics were found to be almost constant, although the oxygen mass transfer decreased due to the presence of surfactants. Experimental results were markedly lower than predicted by the well-known Frössling equation with rigid surfaces. This is believed to be caused by a barrier of surfactants hindering the oxygen mass transfer at the interface. Similar hindrance of oxygen mass transfer applies to waters from sewage plants (filtered raw water and treated water), making accurate design of aeration tanks difficult. PMID:24747142
Structure and energy transfer in photosystems of oxygenic photosynthesis.
Nelson, Nathan; Junge, Wolfgang
2015-01-01
Oxygenic photosynthesis is the principal converter of sunlight into chemical energy on Earth. Cyanobacteria and plants provide the oxygen, food, fuel, fibers, and platform chemicals for life on Earth. The conversion of solar energy into chemical energy is catalyzed by two multisubunit membrane protein complexes, photosystem I (PSI) and photosystem II (PSII). Light is absorbed by the pigment cofactors, and excitation energy is transferred among the antennae pigments and converted into chemical energy at very high efficiency. Oxygenic photosynthesis has existed for more than three billion years, during which its molecular machinery was perfected to minimize wasteful reactions. Light excitation transfer and singlet trapping won over fluorescence, radiation-less decay, and triplet formation. Photosynthetic reaction centers operate in organisms ranging from bacteria to higher plants. They are all evolutionarily linked. The crystal structure determination of photosynthetic protein complexes sheds light on the various partial reactions and explains how they are protected against wasteful pathways and why their function is robust. This review discusses the efficiency of photosynthetic solar energy conversion. PMID:25747397
Yao, Kangning; Chi, Yong; Wang, Fei; Yan, Jianhua; Ni, Mingjiang; Cen, Kefa
2016-01-01
A commonly used aeration device at present has the disadvantages of low mass transfer rate because the generated bubbles are several millimeters in diameter which are much bigger than microbubbles. Therefore, the effect of a microbubble on gas-liquid mass transfer and wastewater treatment process was investigated. To evaluate the effect of each bubble type, the volumetric mass transfer coefficients for microbubbles and conventional bubbles were determined. The volumetric mass transfer coefficient was 0.02905 s(-1) and 0.02191 s(-1) at a gas flow rate of 0.67 L min(-1) in tap water for microbubbles and conventional bubbles, respectively. The degradation rate of simulated municipal wastewater was also investigated, using aerobic activated sludge and ozone. Compared with the conventional bubble generator, the chemical oxygen demand (COD) removal rate was 2.04, 5.9, 3.26 times higher than those of the conventional bubble contactor at the same initial COD concentration of COD 200 mg L(-1), 400 mg L(-1), and 600 mg L(-1), while aerobic activated sludge was used. For the ozonation process, the rate of COD removal using microbubble generator was 2.38, 2.51, 2.89 times of those of the conventional bubble generator. Based on the results, the effect of initial COD concentration on the specific COD degradation rate were discussed in different systems. Thus, the results revealed that microbubbles could enhance mass transfer in wastewater treatment and be an effective method to improve the degradation of wastewater. PMID:27120652
NASA Technical Reports Server (NTRS)
Yang, H. Q.; West, Jeff
2015-01-01
Current reduced-order thermal model for cryogenic propellant tanks is based on correlations built for flat plates collected in the 1950's. The use of these correlations suffers from: inaccurate geometry representation; inaccurate gravity orientation; ambiguous length scale; and lack of detailed validation. The work presented under this task uses the first-principles based Computational Fluid Dynamics (CFD) technique to compute heat transfer from tank wall to the cryogenic fluids, and extracts and correlates the equivalent heat transfer coefficient to support reduced-order thermal model. The CFD tool was first validated against available experimental data and commonly used correlations for natural convection along a vertically heated wall. Good agreements between the present prediction and experimental data have been found for flows in laminar as well turbulent regimes. The convective heat transfer between tank wall and cryogenic propellant, and that between tank wall and ullage gas were then simulated. The results showed that commonly used heat transfer correlations for either vertical or horizontal plate over predict heat transfer rate for the cryogenic tank, in some cases by as much as one order of magnitude. A characteristic length scale has been defined that can correlate all heat transfer coefficients for different fill levels into a single curve. This curve can be used for the reduced-order heat transfer model analysis.
Calculations of the time-averaged local heat transfer coefficients in circulating fluidized bed
Dai, T.H.; Qian, R.Z.; Ai, Y.F.
1999-04-01
The great potential to burn a wide variety of fuels and the reduced emission of pollutant gases mainly SO{sub x} and NO{sub x} have inspired the investigators to conduct research at a brisk pace all around the world on circulating fluidized bed (CFB) technology. An accurate understanding of heat transfer to bed walls is required for proper design of CFB boilers. To develop an optimum economic design of the boiler, it is also necessary to know how the heat transfer coefficient depends on different design and operating parameters. It is impossible to do the experiments under all operating conditions. Thus, the mathematical model prediction is a valuable method instead. Based on the cluster renewal theory of heat transfer in circulating fluidized beds, a mathematical model for predicting the time-averaged local bed-to-wall heat transfer coefficients is developed. The effects of the axial distribution of the bed density on the time-average local heat transfer coefficients are taken into account via dividing the bed into a series of sections along its height. The assumptions are made about the formation and falling process of clusters on the wall. The model predictions are in an acceptable agreement with the published data.
Therese, L; Ghalem, Z; Guillot, P; Belenguer, P
2006-09-01
In radiofrequency glow discharge emission spectrometry (RF-GDOES), the excitation voltage used to create the plasma is applied to the back or front end of the sample to be analyzed. In this paper we focus on back-applied voltage systems (a configuration that represents about half of the instruments available on the market), and on applied voltage problems (the power coupling efficiency and materials analysis are beyond the scope of this study). In the RF-GDOES of nonconductive samples, a voltage drop develops inside the material. The voltage transfer coefficient is defined as the ratio between the peak voltage in front of the sample (facing the plasma) and the peak voltage applied to the back of the sample. In this work, we show that it is possible to increase the voltage transfer coefficient by increasing the capacitance of the sample. The capacitance of a given nonconductive material depends on its surface, its thickness and its permittivity. Increasing the voltage transfer coefficient permits higher power deposition in the plasma. This study is based on an electrical equivalent circuit for the discharge device, which takes into account the sample and reactor capacitances as well as the voltage probes used for the measurements. This circuit, when modeled by a commercial electrical circuit simulator, gives the voltage transfer coefficient as a function of the sample capacitance. Different approaches to increasing the sample capacitance and their influence on the voltage transfer coefficient are presented and related to the 750.4 nm argon line intensity, which is correlated to the electron density. PMID:16724217
Heat transfer coefficients in bubbly and slug flows under microgravity conditions
Rezkallah, K.S.; Rite, R.W.
1996-12-31
Experimental local heat transfer data were collected onboard NASA`s KC-135 reduced gravity aircraft for two-phase, air-water flow in vertical, upward, co-current flow through a 9.53 mm circular tube. It was found that in the bubbly and slug flow regimes (surface tension dominated regimes), reduced gravity has a tendency to lower the heat transfer coefficient by up to 50% at the lowest gas qualities. As the gas quality is increased (transition to annular flow), the difference between the 1-g and {micro}-g heat transfer coefficients is much less significant. Empirical correlations were developed in terms of the pertinent dimensionless groups; namely the superficial liquid Reynolds number, the Froude number, the Graetz number and the Morton number. The correlations predicted the experimental data within 10--25%, depending on the flow regime and the superficial gas Weber number.
NASA Astrophysics Data System (ADS)
Clifford, R. J.; Jones, T. V.; Dunnne, S. T.
1983-03-01
Techniques developed jointly by Rolls-Royce Bristol and Oxford University for determining detailed heat transfer distributions inside turbine blade and vane cooling passages are reviewed. Use is made of a low temperature phase change paint to map the heat flux distributions within models of the cooling passages; the paints change from an opaque coating to a clear liquid at a well-defined melting point. In this way the surface temperature history of a model subjected to transient convective heating is recorded. The heat transfer coefficient distribution is deduced from this history using a transient conduction analysis within the model. Results are presented on detailed heat transfer coefficient distributions within a variety of cooling passages; and data obtained from a comprehensive study of a typical engine multipass cooling geometry are examined.
NASA Astrophysics Data System (ADS)
Jun, Oh-Sung; Kim, Paul Y.
1994-02-01
The influence coefficients for undamped flexible rotors are analytically derived and then compared and discussed for various damping coefficients. The concept of the transfer matrix method is partially adapted in the formulation. Single-disk and single cylinder rotor models are used for one- and two-plane balancing models, respectively. The gyroscopic effect of the disk or cylinder, which has been included in the formulation, is proved important through a simplified example rotor model. Taking the gyroscopic effect into account when calculating the influence coefficient is especially important near the resonant and antiresonant frequencies of the rotor. The simplified model also shows that an increase in damping reduces the sharpness of magnitude curve of influence coefficients and smoothens the change of phase at around the resonant and antiresonant frequencies.
Oxygen transfer rate and sophorose lipid production by Candida bombicola.
Guilmanov, Vladimir; Ballistreri, Alberto; Impallomeni, Giuseppe; Gross, Richard A
2002-03-01
Sophorose lipids (SLs) have applications as surfactants and are produced at high levels by several yeasts. We developed a fed-batch shake-flask method for the production of SLs by Candida bombicola ATCC 22214. Optimal aeration, expressed in terms of oxygen transfer rate, was between 50 and 80 mM O(2)/L h(-1) and resulted in maximum values for both volumetric product formation (1-1.5 g/L h(-1)) and SL yield (350 g/L). The lowest aeration levels resulted in the enrichment in saturated fatty acid SLs at the expense of unsaturated fatty acid SLs. PMID:11788948
Determination of the heat transfer coefficient from IRT measurement data using the Trefftz method
NASA Astrophysics Data System (ADS)
Maciejewska, Beata; Strąk, Kinga; Piasecka, Magdalena
2016-03-01
The paper presents the method of heat transfer coefficient determination for boiling research during FC-72 flow in the minichannels, each 1.7 mm deep, 24 mm wide and 360 mm long. The heating element was the thin foil, enhanced on the side which comes into contact with fluid in the minichannels. Local values of the heat transfer coefficient were calculated from the Robin boundary condition. The foil temperature distribution and the derivative of the foil temperature were obtained by solving the two-dimensional inverse heat conduction problem, due to measurements obtained by IRT. Calculations was carried out by the method based on the approximation of the solution of the problem using a linear combination of Trefftz functions. The basic property of this functions is they satisfy the governing equation. Unknown coefficients of linear combination of Trefftz functions are calculated from the minimization of the functional that expresses the mean square error of the approximate solution on the boundary. The results presented as IR thermographs, two-phase flow structure images and the heat transfer coefficient as a function of the distance from the channel inlet, were analyzed.
Determination of drying kinetics and convective heat transfer coefficients of ginger slices
NASA Astrophysics Data System (ADS)
Akpinar, Ebru Kavak; Toraman, Seda
2015-12-01
In the present work, the effects of some parametric values on convective heat transfer coefficients and the thin layer drying process of ginger slices were investigated. Drying was done in the laboratory by using cyclone type convective dryer. The drying air temperature was varied as 40, 50, 60 and 70 °C and the air velocity is 0.8, 1.5 and 3 m/s. All drying experiments had only falling rate period. The drying data were fitted to the twelve mathematical models and performance of these models was investigated by comparing the determination of coefficient (R 2), reduced Chi-square (χ 2) and root mean square error between the observed and predicted moisture ratios. The effective moisture diffusivity and activation energy were calculated using an infinite series solution of Fick's diffusion equation. The average effective moisture diffusivity values and activation energy values varied from 2.807 × 10-10 to 6.977 × 10-10 m2/s and 19.313-22.722 kJ/mol over the drying air temperature and velocity range, respectively. Experimental data was used to evaluate the values of constants in Nusselt number expression by using linear regression analysis and consequently, convective heat transfer coefficients were determined in forced convection mode. Convective heat transfer coefficient of ginger slices showed changes in ranges 0.33-2.11 W/m2 °C.
NASA Astrophysics Data System (ADS)
Matsunaga, Takeshi; Yoshida, Suguru
A method which is generally applicable to predict the axially local (circumferentially averaged) heat transfer coefficient for refrigerant with oil contained flowing in horizontal evaporator tubes was developed by modifying a prediction method for pure refrigerants. The dimensionless correlation for an annular flow regime takes account of the influence of oil on an improvement or a reduction in the heat transfer, in addition to the change of the properties due to the addition of oil. For a separated flow regime, the correlations of the average heat transfer coefficients in the top part and the bottom part and their boundary angle were developed by modifying each correlation for pure refrigerants. The circumferentially averaged heat transfer coefficient for the separated flow regime can be obtained by using the solution of the steady heat conduction equation in the tube wall, to which the values calculated from the above correlations are applied as the boundary conditions at the inside surface of the tube. Which flow regime, annular or separated, prevails can be determined by the correlation of the boundary angle. The present prediction method was confirmed to be applicable to various kinds of refrigerant-oil mixture.
Integration Of Heat Transfer Coefficient In Glass Forming Modeling With Special Interface Element
Moreau, P.; Gregoire, S.; Lochegnies, D.; Cesar de Sa, J.
2007-05-17
Numerical modeling of the glass forming processes requires the accurate knowledge of the heat exchange between the glass and the forming tools. A laboratory testing is developed to determine the evolution of the heat transfer coefficient in different glass/mould contact conditions (contact pressure, temperature, lubrication...). In this paper, trials are performed to determine heat transfer coefficient evolutions in experimental conditions close to the industrial blow-and-blow process conditions. In parallel of this work, a special interface element is implemented in a commercial Finite Element code in order to deal with heat transfer between glass and mould for non-meshing meshes and evolutive contact. This special interface element, implemented by using user subroutines, permits to introduce the previous heat transfer coefficient evolutions in the numerical modelings at the glass/mould interface in function of the local temperatures, contact pressures, contact time and kind of lubrication. The blow-and-blow forming simulation of a perfume bottle is finally performed to assess the special interface element performance.
Integration Of Heat Transfer Coefficient In Glass Forming Modeling With Special Interface Element
NASA Astrophysics Data System (ADS)
Moreau, P.; César de Sá, J.; Grégoire, S.; Lochegnies, D.
2007-05-01
Numerical modeling of the glass forming processes requires the accurate knowledge of the heat exchange between the glass and the forming tools. A laboratory testing is developed to determine the evolution of the heat transfer coefficient in different glass/mould contact conditions (contact pressure, temperature, lubrication…). In this paper, trials are performed to determine heat transfer coefficient evolutions in experimental conditions close to the industrial blow-and-blow process conditions. In parallel of this work, a special interface element is implemented in a commercial Finite Element code in order to deal with heat transfer between glass and mould for non-meshing meshes and evolutive contact. This special interface element, implemented by using user subroutines, permits to introduce the previous heat transfer coefficient evolutions in the numerical modelings at the glass/mould interface in function of the local temperatures, contact pressures, contact time and kind of lubrication. The blow-and-blow forming simulation of a perfume bottle is finally performed to assess the special interface element performance.
Heat transfer coefficient measurements on the pressure surface of a transonic airfoil
NASA Astrophysics Data System (ADS)
Kodzwa, Paul M.; Eaton, John K.
2010-02-01
This paper presents steady-state recovery temperature and heat transfer coefficient measurements on the pressure surface of a modern, highly cambered transonic airfoil. These measurements were collected with a peak Mach number of 1.5 and a maximum turbulence intensity of 30%. We used a single passage model to simulate the idealized two-dimensional flow path between rotor blades in a modern transonic turbine. This set up offered a simpler construction than a linear cascade, yet produced an equivalent flow condition. We performed validated high accuracy (±0.2°C) surface temperature measurements using wide-band thermochromic liquid crystals allowing separate measurements of the previously listed parameters with the same heat transfer surface. We achieved maximum heat transfer coefficient uncertainties that were equivalent to similar investigations (±10%). Two key observations are the heat transfer coefficient along the aft portion of the airfoil is sensitive to the surface heat flux and is highly insensitive to the level of freestream turbulence. Possible explanations for these observations are discussed.
Calculation of muon transfer from muonic hydrogen to atomic oxygen
Dupays, Arnaud; Lepetit, Bruno; Beswick, J. Alberto; Rizzo, Carlo; Bakalov, Dimitar
2003-06-01
The muon-transfer probabilities between muonic hydrogen and an oxygen atom are calculated in a constrained geometry one-dimensional model for collision energies between 10{sup -6} and 10{sup 3} eV. For relative translational energies below 10{sup -1} eV, for which the de Broglie wavelength (>1 Aa) is much larger than the characteristic distance of the potential interaction ({approx}0.1 Aa), the problem corresponds to an ultracold collision. The close-coupling time-independent quantum equations are written in terms of hyperspherical coordinates and a diabatic-by-sectors basis set. The muon-transfer probabilities are qualitatively interpreted in terms of a model involving two Landau-Zener crossings together with the threshold energy dependence. Based on this analysis, a simple procedure to estimate the energy dependence of the muon-transfer rate in three dimensions is proposed. These estimated rates are discussed in the light of previous model calculations and available experimental data for this process. It is concluded that the high transfer rates at epithermal energies inferred from experiments are unlikely to be correct.
Measurement and prediction of the oxygen diffusion coefficient in partly saturated media
NASA Astrophysics Data System (ADS)
Aachib, M.; Mbonimpa, M.; Aubertin, M.; Bussiere, B.
2004-05-01
Molecular diffusion is an important mechanism for gas transport in various natural and man-made systems. This is particularly the case with soil covers installed on acid generating mine tailings, where oxygen availability has to be controlled. One of the most important roles of such covers is to limit gas flux, which depends on the effective diffusion coefficient De of the cover materials. This paper presents an experimental procedure and results from oxygen diffusion tests performed on different types of materials, at various degrees of saturation. The determination of De in the laboratory from the test data is based on solutions to Fick's laws. The ensuing values of De are compared to values calculated from available models that relate De to basic material properties, including porosity and degree of saturation. Statistical indicators are used to evaluate the accuracy of selected models, individually and on a comparative basis. It is shown that modified versions of the Millington-Quirk and Millington-Shearer models provide De values close to the measured data. A semi-empirical expression, ensuing from these models and measurements, is proposed as a simple means of estimating De.
Dimethylsulfide gas transfer coefficients from algal blooms in the Southern Ocean
NASA Astrophysics Data System (ADS)
Bell, T. G.; De Bruyn, W.; Marandino, C. A.; Miller, S. D.; Law, C. S.; Smith, M. J.; Saltzman, E. S.
2015-02-01
Air-sea dimethylsulfide (DMS) fluxes and bulk air-sea gradients were measured over the Southern Ocean in February-March 2012 during the Surface Ocean Aerosol Production (SOAP) study. The cruise encountered three distinct phytoplankton bloom regions, consisting of two blooms with moderate DMS levels, and a high biomass, dinoflagellate-dominated bloom with high seawater DMS levels (> 15 nM). Gas transfer coefficients were considerably scattered at wind speeds above 5 m s-1. Bin averaging the data resulted in a linear relationship between wind speed and mean gas transfer velocity consistent with that previously observed. However, the wind-speed-binned gas transfer data distribution at all wind speeds is positively skewed. The flux and seawater DMS distributions were also positively skewed, which suggests that eddy covariance-derived gas transfer velocities are consistently influenced by additional, log-normal noise. A flux footprint analysis was conducted during a transect into the prevailing wind and through elevated DMS levels in the dinoflagellate bloom. Accounting for the temporal/spatial separation between flux and seawater concentration significantly reduces the scatter in computed transfer velocity. The SOAP gas transfer velocity data show no obvious modification of the gas transfer-wind speed relationship by biological activity or waves. This study highlights the challenges associated with eddy covariance gas transfer measurements in biologically active and heterogeneous bloom environments.
Ludlow, Michelle K; Soudackov, Alexander V; Hammes-Schiffer, Sharon
2010-02-01
Electrochemical proton-coupled electron transfer of an osmium aquo complex attached to a self-assembled monolayer on a gold electrode is studied with a recently developed theoretical formulation. The calculated hydrogen/deuterium kinetic isotope effect for the standard rate constant, the cathodic transfer coefficient at zero overpotential, and the Tafel plot are in excellent agreement with experimental data. The input quantities to the heterogeneous rate constant expressions were calculated with density functional theory in conjunction with dielectric continuum models, and no parameters were fit to experimental data. The theoretical calculations indicate that the asymmetry of the Tafel plot and the deviation of the transfer coefficient at zero overpotential from the standard value of one-half arise from the change in the equilibrium proton donor-acceptor distance upon electron transfer. The direction of the asymmetry and deviation from one-half is determined by the sign of this distance change, and the magnitude of these effects is determined by the magnitude of this distance change, as well as the reorganization energy and the distance dependence of the overlap between the initial and final proton vibrational wave functions. This theory provides experimentally testable predictions for the impact of specific system properties on the qualitative behavior of the Tafel plots. PMID:20067257
Single-phase ambient and cryogenic temperature heat transfer coefficients in microchannels
NASA Astrophysics Data System (ADS)
Baek, S.; Bradley, P. E.
2015-12-01
Micro-scaling cryogenic refrigerators, in particular the Joule-Thomson (JT) variety require very good information about heat transfer characteristics of the refrigerants flowing in the microchannels for optimal design and performance. The extremely low Reynolds flow is present in a micro JT cryocooler, the heat transfer characteristics at these conditions require investigation. There are numerous studies regarding heat transfer coefficient measurements of liquid flow in microchannels at/near ambient temperature and high Reynolds flow (Re>2000), that agree well with the conventional correlations. However, results from previous studies of gaseous flow in microchannels at low Reynolds flow (Re<1000) disagree with conventional theory. Moreover, the studies performed at cryogenic temperatures are quite limited in number. In this paper, the single-phase heat transfer coefficients and friction factors for nitrogen are measured at ambient and cryogenic temperatures. The hydraulic diameters for this study are 60, 110 and 180 μm for circular microchannels. The Reynolds numbers varied from a very low value of 10 to 3000. The measured friction factors are comparable to those in macro-scale tubes. The experimental results of the heat transfer indicate that Nusselt numbers derived from measurements are significantly affected by axial conduction at low Reynolds flow (Re<500). The Nusselt numbers at high Reynolds flow (Re>1000) follow conventional theory. The detailed experiment, procedure, and measured results are presented in this paper and discussed regarding deviation from ideal theory at low Reynolds flow.
Fukui, Toru; Kataoka, Yoshiyuki; Hatamiya, Shigeo
1990-01-01
New concepts with passive safety systems that use no active compounds, such as pumps, have been recently developed for next-generation nuclear power plants. In these concepts, several ideas and their combination of passive components were adopted for emergency core cooling and residual heat removal systems. For the residual heat removal system, utilization of natural circulation heat transfer in water pools was proposed as a passive containment cooling system (PCCS), which removes decay heat from the primary containment vessel (PCV) during loss-of-coolant accidents (LOCAs). This system consists of a suppression pool (S/P) and an outer pool (O/P), which are set adjacently inside and outside of the steel PCV wall. The core decay heat during LOCA is released through a break as steam and is led into the S/P. The injected steam condenses there, resulting a pool temperature rise. The adsorbed heat in the S/P is transferred to the O/P by convection in both pools and thermal conduction through the steel PCV wall. The heat transferred to the O/P is finally released to the atmosphere by vaporization of the O/P water. Estimation of the convectional heat transfer coefficients in both pools is necessary to predict the heat removal capability in this system precisely. The heat transfer coefficients measured in this study are useful for the design of the next-generation nuclear reactor as the fundamental thermal-hydraulic data in the primary containment vessel with the outer pool.
Huerst, C.; Schulz, A.; Wittig, S.
1995-04-01
The present study compares measured and computed heat transfer coefficients for high-speed boundary layer nozzle flows under engine Reynolds number conditions (U{sub {infinity}} = 230 {divided_by} 880 m/s, Re* = 0.37 {divided_by} 1.07 {times} 10{sup 6}). Experimental data have been obtained by heat transfer measurements in a two-dimensional, nonsymmetric, convergent-divergent nozzle. The nozzle wall is convectively cooled using water passages. The coolant heat transfer data and nozzle surface temperatures are used as boundary conditions for a three-dimensional finite-element code, which is employed to calculate the temperature distribution inside the nozzle wall. Heat transfer coefficients along the hot gas nozzle wall are derived from the temperature gradients normal to the surface. The results are compared with numerical heat transfer predictions using the low-Reynolds-number {kappa}-{epsilon} turbulence model by Lam and Bremhorst. Influence of compressibility in the transport equations for the turbulence properties is taken into account by using the local averaged density. The results confirm that this simplification leads to good results for transonic and low supersonic flows.
Study of the average heat transfer coefficient at different distances between wind tunnel models
NASA Astrophysics Data System (ADS)
Gnyrya, A.; Korobkov, S.; Mokshin, D.; Koshin, A.
2015-01-01
The paper presents investigations of physical and climatic factors with regard to design and process variables having effect on heat transfer in the building model system at different distances between them in the airflow direction. The aim of this work is to improve energy efficiency of exterior walls of buildings. A method of physical simulation was used in experiments. Experimental results on the average values of the heat transfer coefficient in the building model system are presented herein. A series of experiments was carried out on a specific aerodynamic test bench including a subsonic wind tunnel, heat models and devices for giving thermal boundary conditions, transducers, and the record system equipment. The paper contains diagrams of the average heat transfer distribution at fixed Reynolds number and the airflow angle of attack; the average values of the heat transfer coefficient for each face and wind tunnel models as a whole at maximum, medium, and large distances between them. Intensification of the average heat transfer was observed on the downstream model faces depending on the distance between models.
NASA Technical Reports Server (NTRS)
Chung, S.
1973-01-01
Heat transfer phenomena of rarefied gas flows is discussed based on a literature survey of analytical and experimental rarefied gas dynamics. Subsonic flows are emphasized for the purposes of meteorological thermometry in the high atmosphere. The heat transfer coefficients for three basic geometries are given in the regimes of free molecular flow, transition flow, slip flow, and continuum flow. Different types of heat phenomena, and the analysis of theoretical and experimental data are presented. The uncertainties calculated from the interpolation rule compared with the available experimental data are discussed. The recovery factor for each geometry in subsonic rarefied flows is also given.
Determination of heat transfer coefficient for an interaction of sub-cooled gas and metal
NASA Astrophysics Data System (ADS)
Zaidi Sidek, Mohd; Syahidan Kamarudin, Muhammad
2016-02-01
Heat transfer coefficient (HTC) for a hot metal surface and their surrounding is one of the need be defined parameter in hot forming process. This study has been conducted to determine the HTC for an interaction between sub-cooled gas sprayed on a hot metal surface. Both experiments and finite element have been adopted in this work. Initially, the designated experiment was conducted to obtain temperature history of spray cooling process. Then, an inverse method was adopted to calculate the HTC value before we validate in a finite element simulation model. The result shows that the heat transfer coefficient for interaction of subcooled gas and hot metal surface is 1000 W/m2K.
Analytical Solutions of Heat-Conduction Problems with Time-Varying Heat-Transfer Coefficients
NASA Astrophysics Data System (ADS)
Kudinov, V. A.; Eremin, A. V.; Stefanyuk, E. V.
2015-05-01
The problem on heat conduction of an infinite plate with a heat-transfer coefficient changing linearly with time for third-kind boundary conditions was solved analytically based on determination of the front of a temperature disturbance in this plate and introduction of additional boundary conditions. On the basis of the solution obtained, graphs of the distribution of isotherms in the indicated plate and the velocities of their movement along a spatial variable in it were constructed. As a result of the solution of the inverse problem on the heat conduction of the infinite plate with the use of the results of numerical calculation of the change in its temperature at any point on the indicated spatial coordinate, the Predvoditelev number was identified with an accuracy of 2%, which made it possible to determine the time dependence of the heat-transfer coefficient of the plate.
NASA Technical Reports Server (NTRS)
Masiulaniec, K. Cyril; Vanfossen, G. James, Jr.; Dewitt, Kenneth J.; Dukhan, Nihad
1995-01-01
A technique was developed to cast frozen ice shapes that had been grown on a metal surface. This technique was applied to a series of ice shapes that were grown in the NASA Lewis Icing Research Tunnel on flat plates. Nine flat plates, 18 inches square, were obtained from which aluminum castings were made that gave good ice shape characterizations. Test strips taken from these plates were outfitted with heat flux gages, such that when placed in a dry wind tunnel, can be used to experimentally map out the convective heat transfer coefficient in the direction of flow from the roughened surfaces. The effects on the heat transfer coefficient for both parallel and accelerating flow will be studied. The smooth plate model verification baseline data as well as one ice roughened test case are presented.
Negative ion clusters in oxygen: collision cross sections and transport coefficients
NASA Astrophysics Data System (ADS)
de Urquijo, J.; Bekstein, A.; Ducasse, O.; Ruíz-Vargas, G.; Yousfi, M.; Benhenni, M.
2009-12-01
Using a pulsed Townsend experiment, we have observed the formation of two negative ion species in oxygen over the pressure range 100-600 torr, and the density-normalised electric field strength, E/N, from 2 to 14 Td. The peculiar shape of these transients has led us to propose a scheme of three-body ion-molecule reactions leading to the formation of O4 - and O6 -, which is substantiated by a curve fitting procedure. The resulting mobility data of these two ionic species have been used to calculate their respective momentum transfer collision cross sections, together with the dissociation cross sections that are needed to extend the range of calculation of mobility and diffusion (transverse and longitudinal) to 1000 Td. These calculations were based on an optimised Monte Carlo algorithm, using collision cross sections obtained from a JWKB approximation (Jeffreys-Wentzel-Kramers-Brillouin) or taken from literature.
Determining the nominal power transfer coefficient for passive surface acoustic wave devices
NASA Astrophysics Data System (ADS)
Timoshenko, A. N.; Palamarchuk, A. A.; Semenko, A. I.
1982-05-01
A method for calculating the nominal power transfer coefficient of passive SAW devices operating in a linear mode is described. Relations of practical importance are obtained, making it possible, on the basis of known characteristics of acousto-electric transducers and acoustic lines, to determine the losses incurred by devices when they are connected to radioelectronic equipment. The relations also permit an assessment of the uniformity of the amplitude-frequency characteristics of the devices.
NASA Astrophysics Data System (ADS)
Yu, Huidan; Zhang, Jinsuo; Li, Ning
2006-03-01
We investigate the enhancement of mass transfer in 2D thermally driven cavities using lattice Boltzmann equation (LBE) method. The computational technique integrates three coupled LBEs for solving velocity, temperature, and concentration fields simultaneously. Simulation is performed for oxygen transfer in lead/lead-bismuth eutectic with variations of temperature boundary, Schmidt number, and field aspect ratio to investigate the effects on enhancement of oxygen transfer. Interested characteristics include oxygen concentration, Sherwood number, and velocity profiles, etc. Our results clearly indicate that oxygen transfer is dominated by convection while diffusion also plays a role on it. Comparative studies demonstrate that side heating and top cooling device is more efficient to transfer oxygen than side heating and cooling device and oxygen transfers more rapidly in square cavity than in rectangular cavity. This work establishes a reliable thermal LBE model for thermally driven heat and mass transfer.
NASA Astrophysics Data System (ADS)
Mirmanto, M.
2016-01-01
Experiments to investigate local pressure distribution and local heat transfer coefficients during flow boiling of water in a microchannel were performed. The hydraulic diameter of the channel was 0.635 mm. The nominal mass fluxes used were varied from 200 to 700 kg/m2 s and heat fluxes ranging from 171 to 685 kW/m2 were applied. An inlet fluid temperature of 98 °C and pressure of 125 kPa were maintained at the microchannel entrance. There were six pressure tappings inserted into the channel to measure the local pressures and six thermocouple inserted into the channel block with equally distances to measure the wall local temperatures. The local pressure measurements during flow boiling show a non linear line connecting each local pressure, especially at higher heat fluxes or pressure drops. The non linear local pressure influences the value of the estimated local heat transfer coefficient. The effects of mass flux and heat flux on local heat transfer coefficient are also discussed.
Adiabatic Effectiveness and Heat Transfer Coefficient on a Film-Cooled Rotating Blade
NASA Technical Reports Server (NTRS)
Garg, Vijay K.
1997-01-01
three-dimensional Navier-Stokes code has been used to compute the adiabatic effectiveness and heat transfer coefficient on a rotating film-cooled turbine blade. The blade chosen is the United Technologies Research Center(UTRC) rotor with five film-cooling rows containing 83 holes, including three rows on the shower head with 49 holes, covering about 86% of the blade span. The mainstream is akin to that under real engine conditions with stagnation temperature 1900 K and stagnation pressure 3 MPa. The blade speed is taken to be 5200 rpm. The adiabatic effectiveness is higher for a rotating blade as compared to that for a stationary blade. Also, the direction of coolant injection from the shower-head holes considerably affects the effectiveness and heat transfer coefficient values on both the pressure and suction surfaces. In all cases the heat transfer coefficient and adiabatic effectiveness are highly three-dimensional in the vicinity of holes but tend to become two-dimensional far downstream.
NASA Astrophysics Data System (ADS)
Dag, Yusuf
Forced convection over traditional surfaces such as flat plate, cylinder and sphere have been well researched and documented. Data on forced convection over airfoil surfaces, however, remain very scanty in literature. High altitude vehicles that employ airfoils as lifting surfaces often suffer leading edge ice accretions which have tremendous negative consequences on the lifting capabilities and stability of the vehicle. One of the ways of mitigating the effect of ice accretion involves judicious leading edge convective cooling technique which in turn depends on the accuracy of convective heat transfer coefficient used in the analysis. In this study empirical investigation of convective heat transfer measurements on asymmetric airfoil is presented at different angle of attacks ranging from 0° to 20° under subsonic flow regime. The top and bottom surface temperatures are measured at given points using Senflex hot film sensors (Tao System Inc.) and used to determine heat transfer characteristics of the airfoils. The model surfaces are subjected to constant heat fluxes using KP Kapton flexible heating pads. The monitored temperature data are then utilized to determine the heat convection coefficients modelled empirically as the Nusselt Number on the surface of the airfoil. The experimental work is conducted in an open circuit-Eiffel type wind tunnel, powered by a 37 kW electrical motor that is able to generate subsonic air velocities up to around 41 m/s in the 24 square-inch test section. The heat transfer experiments have been carried out under constant heat flux supply to the asymmetric airfoil. The convective heat transfer coefficients are determined from measured surface temperature and free stream temperature and investigated in the form of Nusselt number. The variation of Nusselt number is shown with Reynolds number at various angles of attacks. It is concluded that Nusselt number increases with increasing Reynolds number and increase in angle of attack from 0
NASA Astrophysics Data System (ADS)
Mobile, Michael; Widdowson, Mark; Stewart, Lloyd; Nyman, Jennifer; Deeb, Rula; Kavanaugh, Michael; Mercer, James; Gallagher, Daniel
2016-04-01
Better estimates of non-aqueous phase liquid (NAPL) mass, its persistence into the future, and the potential impact of source reduction are critical needs for determining the optimal path to clean up sites impacted by NAPLs. One impediment to constraining time estimates of source depletion is the uncertainty in the rate of mass transfer between NAPLs and groundwater. In this study, an innovative field test is demonstrated for the purpose of quantifying field-scale NAPL mass transfer coefficients (klN) within a source zone of a fuel-contaminated site. Initial evaluation of the test concept using a numerical model revealed that the aqueous phase concentration response to the injection of clean groundwater within a source zone was a function of NAPL mass transfer. Under rate limited conditions, NAPL dissolution together with the injection flow rate and the radial distance to monitoring points directly controlled time of travel. Concentration responses observed in the field test were consistent with the hypothetical model results allowing field-scale NAPL mass transfer coefficients to be quantified. Site models for groundwater flow and solute transport were systematically calibrated and utilized for data analysis. Results show klN for benzene varied from 0.022 to 0.60 d- 1. Variability in results was attributed to a highly heterogeneous horizon consisting of layered media of varying physical properties.
Mobile, Michael; Widdowson, Mark; Stewart, Lloyd; Nyman, Jennifer; Deeb, Rula; Kavanaugh, Michael; Mercer, James; Gallagher, Daniel
2016-04-01
Better estimates of non-aqueous phase liquid (NAPL) mass, its persistence into the future, and the potential impact of source reduction are critical needs for determining the optimal path to clean up sites impacted by NAPLs. One impediment to constraining time estimates of source depletion is the uncertainty in the rate of mass transfer between NAPLs and groundwater. In this study, an innovative field test is demonstrated for the purpose of quantifying field-scale NAPL mass transfer coefficients (kl(N)) within a source zone of a fuel-contaminated site. Initial evaluation of the test concept using a numerical model revealed that the aqueous phase concentration response to the injection of clean groundwater within a source zone was a function of NAPL mass transfer. Under rate limited conditions, NAPL dissolution together with the injection flow rate and the radial distance to monitoring points directly controlled time of travel. Concentration responses observed in the field test were consistent with the hypothetical model results allowing field-scale NAPL mass transfer coefficients to be quantified. Site models for groundwater flow and solute transport were systematically calibrated and utilized for data analysis. Results show kl(N) for benzene varied from 0.022 to 0.60d(-1). Variability in results was attributed to a highly heterogeneous horizon consisting of layered media of varying physical properties. PMID:26855386
Mass transfer coefficient in ginger oil extraction by microwave hydrotropic solution
NASA Astrophysics Data System (ADS)
Handayani, Dwi; Ikhsan, Diyono; Yulianto, Mohamad Endy; Dwisukma, Mandy Ayulia
2015-12-01
This research aims to obtain mass transfer coefficient data on the extraction of ginger oil using microwave hydrotropic solvent as an alternative to increase zingiberene. The innovation of this study is extraction with microwave heater and hydrotropic solvent,which able to shift the phase equilibrium, and the increasing rate of the extraction process and to improve the content of ginger oil zingiberene. The experiment was conducted at the Laboratory of Separation Techniques at Chemical Engineering Department of Diponegoro University. The research activities carried out in two stages, namely experimental and modeling work. Preparation of the model postulated, then lowered to obtain equations that were tested and validated using data obtained from experimental. Measurement of experimental data was performed using microwave power (300 W), extraction temperature of 90 ° C and the independent variable, i.e.: type of hydrotropic, the volume of solvent and concentration in order, to obtain zingiberen levels as a function of time. Measured data was used as a tool to validate the postulation, in order to obtain validation of models and empirical equations. The results showed that the mass transfer coefficient (Kla) on zingiberene mass transfer models ginger oil extraction at various hydrotropic solution attained more 14 ± 2 Kla value than its reported on the extraction with electric heating. The larger value of Kla, the faster rate of mass transfer on the extraction process. To obtain the same yields, the microwave-assisted extraction required one twelfth time shorter.
NASA Technical Reports Server (NTRS)
Neeman, Binyamin U.; Ohring, George; Joseph, Joachim H.
1989-01-01
This paper examines a parameterization of a quasi-geostrophic eddy transport that takes into account the time variation of eddy transfer coefficients according to Green's (1970) theory. It was found that, in the original eddy transfer relationship of Green, connecting the integral of the northward eddy entropy flux through midlatitudes with the second power of the difference in 500-mb entropy across the region of baroclinic activity, a value of 4 for the exponent is obtained when the temperature gradients at 500 mb are used. When the gradients at 1000 mb are used, an exponent of 1.5 is obtained. The differences in the powers in the eddy transfer relation were explored in a two-level zonally averaged model. It was found that an appropriate choice of power may be of special importance if the model is devised to simulate the seasonal climate cycle or to test astronomical changes inducing different seasonalities.
NASA Astrophysics Data System (ADS)
Tobajas, M.; García-Calvo, E.
Mass transfer in bioreactors has been examined. In the present work, dynamic methods are used for the determination of KLa values for water, model media and a fermentation broth (Candida utilis) in an airlift reactor. The conventional dynamic method is applied at the end of the microbial process in order to avoid an alteration in the metabolism of the microorganisms. New dynamic methods are used to determine KLa in an airlift reactor during the microbial growth of Candida utilis on glucose. One of the methods is based on the continuous measurement of carbon dioxide production while the other method is based on the relationship between the oxygen transfer and biomass growth rates. These methods of determining KLa does not interfere with the microorganisms action. A theoretical mass transfer model has been used for KLa estimation for the systems described above. Some differences between calculated and measured values are found for fermentation processes due to the model is developed for two-phase air-water systems. Nevertheless, the average deviation between the predicted values and those obtained from the relationship between oxygen transfer and biomass production rates are lower than 25% in any case.
Esperança, M N; Cunha, F M; Cerri, M O; Zangirolami, T C; Farinas, C S; Badino, A C
2014-05-01
Sugarcane bagasse is a low-cost and abundant by-product generated by the bioethanol industry, and is a potential substrate for cellulolytic enzyme production. The aim of this work was to evaluate the effects of air flow rate (QAIR), solids loading (%S), sugarcane bagasse type, and particle size on the gas hold-up (εG) and volumetric oxygen transfer coefficient (kLa) in three different pneumatic bioreactors, using response surface methodology. Concentric tube airlift (CTA), split-cylinder airlift (SCA), and bubble column (BC) bioreactor types were tested. QAIR and %S affected oxygen mass transfer positively and negatively, respectively, while sugarcane bagasse type and particle size (within the range studied) did not influence kLa. Using large particles of untreated sugarcane bagasse, the loop-type bioreactors (CTA and SCA) exhibited higher mass transfer, compared to the BC reactor. At higher %S, SCA presented a higher kLa value (0.0448 s−1) than CTA, and the best operational conditions in terms of oxygen mass transfer were achieved for %S < 10.0 g L−1 and QAIR > 27.0 L min−1. These results demonstrated that pneumatic bioreactors can provide elevated oxygen transfer in the presence of vegetal biomass, making them an excellent option for use in three-phase systems for cellulolytic enzyme production by filamentous fungi. PMID:24078146
Revisiting direct electron transfer in nanostructured carbon laccase oxygen cathodes.
Adam, Catherine; Scodeller, Pablo; Grattieri, Matteo; Villalba, Matías; Calvo, Ernesto J
2016-06-01
The biocatalytic electroreduction of oxygen has been studied on large surface area graphite and Vulcan® carbon electrodes with adsorbed Trametes trogii laccase. The electrokinetics of the O2 reduction reaction (ORR) was studied at different electrode potentials, O2 partial pressures and concentrations of hydrogen peroxide. Even though the overpotential at 0.25 mA·cm(-2) for the ORR at T1Cu of the adsorbed laccase on carbon is 0.8 V lower than for Pt of similar geometric area, the rate of the reaction and thus the operative current density is limited by the enzyme reaction rate at the T2/T3 cluster site for the adsorbed enzyme. The transition potential for the rate determining step from the direct electron transfer (DET) to the enzyme reaction shifts to higher potentials at higher oxygen partial pressure. Hydrogen peroxide produced by the ORR on bare carbon support participates in an inhibition mechanism, with uncompetitive predominance at high H2O2 concentration, non-competitive contribution can be detected at low inhibitor concentration. PMID:26883057
The Seebeck Coefficient in Oxygen Enriched La2NiO4
NASA Astrophysics Data System (ADS)
Bach, Paul; Leboran, Victor; Rivadulla, Francisco
2013-03-01
Oxide-based devices show promise for themoelectric applications due to their chemical stability and straightforward fabrication. The La2NiO4+δ system has been predicted to show an increased thermopower coupled with an increased electrical conductivity around δ = 0 . 05 [Pardo et al. PRB 86, 165114 (2012)] that could lead to a large thermoelectric figure of merit (ZT). We investigate the suitability of lanthanum nickelate as a candidate material for high-ZT devices through a systematic study of oxygenated thin films grown by pulsed laser deposition. We report the electrical conductivity, Seebeck coefficient, and structural morphology of La2NiO4 grown in a range of oxidizing atmospheres and discuss their implications for controlled engineering of thermoelectric properties. We have explored the possibility of gate-tuning these systems in order to fabricate single-oxide based devices. This work was supported by the Ministerio de Ciencia e Innovación (Spain), grant MAT2010-16157, and the European Research Council, grant ERC-2010-StG 259082 2D THERMS.
Goemans, M.G.E.; Gloyna, E.F.
1996-10-01
The potential of sub- and supercritical water as extraction solvents has been demonstrated for the (reactive) extraction of coals, used car tires, organic species from residual aqueous solutions, and class selective extraction of organic pollutants with different polarities from solids. In addition, the potential of extraction of coal with supercritical aqueous solutions has been studied. However, physical transport in water at elevated temperature and pressures- and their impact on heterogenous reactions and (reactive) extraction -are not adequately understood. This situation is largely due to the limited data that is available for diffusion in high temperature, high pressure water mixture. Only the molecular diffusion of Iodine ions and hydroquinone in near-critical subcritical water and the self diffusion of coefficient of compressed supercritical water have been reported. In this paper, we present molecular diffusion coefficients of benzophenone, acetone, naphthalene, and anthracene in water at infinite dilution. Pressures ranged from 250 to 500 bar at temperatures ranging from 50{degrees}C to 500{degrees}C resulting in water densities ranging from 1000 to 150 kg/m{sup 3}. Diffusion coefficients were determined by the Taylor-Aris dispersion technique. The effects of increased diffusion on the mass transfer coefficients for emulsions and packed beds were quantified. Molecular division coefficients were 10 to 20 times faster in supercritical water than in water at ambient conditions. Experimental results were correlated with hydrodynamic and kinetic theory. This study and results to be published elsewhere show that diffusion-limited conditions are much more likely to be encountered in supercritical water than is commonly acknowledged.
Parameterizations of interactions of polar multifunctional organic oxygenates in PM2.5 must be included in aerosol chemistry models for evaluating control strategies for reducing ambient concentrations of PM2.5 compounds. Vapor pressures and activity coefficients of these compo...
NASA Astrophysics Data System (ADS)
Wang, Z.; Ireland, P. T.; Jones, T. V.
1995-04-01
The heat transfer coefficient over the surface of a pedestal with fillet radii has been measured using thermochromic liquid crystals and the transient heat transfer method. The tests were performed at engine representative Reynolds numbers for a geometry typical of those used in turbine blade cooling systems. The heat conduction process that occurs in the engine was subsequently modeled numerically with a finite element discretization of the solid pedestal. The measured heat transfer coefficients were used to derive the exact boundary conditions applicable to the engine. The temperature field within the pedestal, calculated using the correct heat transfer coefficient distribution, is compared to that calculated using an area-averaged heat transfer coefficient. Metal temperature differences of 90 K are predicted across the blade wall.
NASA Astrophysics Data System (ADS)
Gladden, H. J.; Proctor, M. P.
A transient technique was used to measure heat transfer coefficients on stator airfoils in a high-temperature annular cascade at real engine conditions. The transient response of thin film thermocouples on the airfoil surface to step changes in the gas stream temperature was used to determine these coefficients. In addition, gardon gages and paired thermocouples were also utilized to measure heat flux on the airfoil pressure surface at steady state conditions. The tests were conducted at exit gas stream Reynolds numbers of one-half to 1.9 million based on true chord. The results from the transient technique show good comparison with the steady-state results in both trend and magnitude. In addition, comparison is made with the STAN5 boundary layer code and shows good comparison with the trends. However, the magnitude of the experimental data is consistently higher than the analysis.
Surface heat transfer coefficient, heat efficiency, and temperature of pulsed solid-state lasers
Mann, K.; Weber, H.
1988-08-01
The temperature of solid-state lasers is a critical parameter. Efficiency and output power are strongly influenced by it. The two parameters which determine the temperature are the heat generation efficiency (HGE) and the surface heat transfer coefficient (SHTC) of the laser rod. These parameters allow the scaling of the rod temperature up to high pumping powers. Moreover, from the temperature inside the rod, the temperature gradients and the mechanical stress can be evaluated. Using transient temperature measurements, the SHTC and the HGE were determined for air- and water-cooled Nd:YAG and alexandrite lasers. The SHTC can be confirmed by theoretical considerations.
Effect of Mixed Working Fluid Composition on Binary Cycle Condenser Heat Transfer Coefficients
Dan Wendt; Greg Mines
2011-10-01
Effect of Mixed Working Fluid Composition on Binary Cycle Condenser Heat Transfer Coefficients Dan Wendt, Greg Mines Idaho National Laboratory The use of mixed working fluids in binary power plants can provide significant increases in plant performance, provided the heat exchangers are designed to take advantage of these fluids non-isothermal phase changes. In the 1980's testing was conducted at DOE's Heat Cycle Research Facility (HCRF) where mixtures of different compositions were vaporized at supercritical pressures and then condensed. This testing had focused on using the data collected to verify that Heat Transfer Research Incorporated (HTRI) codes were suitable for the design of heat exchangers that could be used with mixtures. The HCRF data includes mixture compositions varying from 0% to 40% isopentane and condenser tube orientations of 15{sup o}, 60{sup o}, and 90{sup o} from horizontal. Testing was performed over a range of working fluid and cooling fluid conditions. Though the condenser used in this testing was water cooled, the working fluid condensation occurred on the tube-side of the heat exchanger. This tube-side condensation is analogous to that in an air-cooled condenser. Tube-side condensing heat transfer coefficient information gleaned from the HCRF testing is used in this study to assess the suitability of air-cooled condenser designs for use with mixtures. Results of an air-cooled binary plant process model performed with Aspen Plus indicate that that the optimal mixture composition (producing the maximum net power for the scenario considered) is within the range of compositions for which data exist. The HCRF data is used to assess the impact of composition, tube orientation, and process parameters on the condensing heat transfer coefficients. The sensitivity of the condensing coefficients to these factors is evaluated and the suitability of air-cooled condenser designs with mixtures is assessed. This paper summarizes the evaluation of the HCRF
Evaluation of oxygen mass transfer in Aspergillus niger fermentation using data reconciliation.
Patel, Nilesh; Thibault, Jules
2004-01-01
Fermentation experiments using Aspergillus niger result in a very viscous broth due to the growth of filamentous microorganism. For viscous fermentation processes, it is difficult to estimate with confidence the volumetric oxygen mass transfer coefficient (K(L)a), which can be used for scale-up or design of bioreactors. In the present study, four methods based on dynamic and stationary approaches were used to measure K(L)a throughout the fermentation. Data reconciliation was used to obtain a more reliable and consistent K(L)a. The K(L)a value obtained by a data reconciliation technique was found to be more reliable since it takes into consideration both the reliability of all measured variables and the accuracy of all mass balance equations. PMID:14763848
NASA Astrophysics Data System (ADS)
Li, Huiping; He, Lianfang; Zhang, Chunzhi; Cui, Hongzhi
2016-04-01
The thermal physical parameters have significant effects on the calculation accuracy of physical fields, and the boundary heat transfer coefficient between the die and water is one of the most important thermal physical parameters in the hot stamping. In order to attain the boundary heat transfer coefficient, the testing devices and test procedures are designed according to the characteristic of heat transfer in the hot stamping die. A method of estimating the temperature-dependent boundary heat transfer coefficient is presented, and an inverse heat conduction software is developed based on finite element method, advance-retreat method and golden section method. The software is used to calculate the boundary heat transfer coefficient according to the temperatures measured by NiCr-NiSi thermocouples in the experiment. The research results show that, the convergence of the method given in the paper is well, the surface temperature of sample has a significant effect on the boundary heat transfer coefficient between the die and water. The boundary heat transfer coefficient increases as the surface temperature of sample reduces, and the variation is nonlinear.
Oxygen-reducing biocathodes operating with passive oxygen transfer in microbial fuel cells.
Xia, Xue; Tokash, Justin C; Zhang, Fang; Liang, Peng; Huang, Xia; Logan, Bruce E
2013-02-19
Oxygen-reducing biocathodes previously developed for microbial fuel cells (MFCs) have required energy-intensive aeration of the catholyte. To avoid the need for aeration, the ability of biocathodes to function with passive oxygen transfer was examined here using air cathode MFCs. Two-chamber, air cathode MFCs with biocathodes produced a maximum power density of 554 ± 0 mW/m(2), which was comparable to that obtained with a Pt cathode (576 ± 16 mW/m(2)), and 38 times higher than that produced without a catalyst (14 ± 3 mW/m(2)). The maximum current density with biocathodes in this air-cathode MFC was 1.0 A/m(2), compared to 0.49 A/m(2) originally produced in a two-chamber MFC with an aqueous cathode (with cathode chamber aeration). Single-chamber, air-cathode MFCs with the same biocathodes initially produced higher voltages than those with Pt cathodes, but after several cycles the catalytic activity of the biocathodes was lost. This change in cathode performance resulted from direct exposure of the cathodes to solutions containing high concentrations of organic matter in the single-chamber configuration. Biocathode performance was not impaired in two-chamber designs where the cathode was kept separated from the anode solution. These results demonstrate that direct-air biocathodes can work very well, but only under conditions that minimize heterotrophic growth of microorganisms on the cathodes. PMID:23360098
Calculating Hot Spring/Atmospheric Coupling Using the Coefficient of Convective Heat Transfer
NASA Astrophysics Data System (ADS)
Lindsey, C.; Price, A. N.; Fairley, J. P., Jr.; Larson, P. B.
2015-12-01
We calculated the correlation between discharge temperature and wind speed for multiple hydrothermal springs, both in the Alvord Basin of southeast Oregon and our primary field location in Yellowstone National Park, using spring temperatures, wind speeds, and air temperatures logged at three minute intervals for multiple days. We find that some hydrothermal springs exhibit strong coupling with wind speed and/or air temperatures. The three springs described in this work display this strong coupling, with correlations between wind speed and spring temperature as high as 70 percent; as a result, we can use the changes in spring temperature as a proxy for changes in the coefficient of convective heat transfer (h) between the springs and the atmosphere. The coefficient of convective heat transfer is a complex parameter to measure, but is a necessary input to many heat and mass flux analyses. The results of this study provide a way to estimate h for springs with strong atmospheric coupling, which is a critical component of a total energy balance for hydrothermal discharge areas.
Transfer coefficient of 137Cs from feed to cow milk in tropical region Kaiga, India.
Joshi, R M; James, J P; Dileep, B N; Mulla, R M; Reji, T K; Ravi, P M; Hegde, A G; Sarkar, P K
2012-04-01
In the transport model for the prediction of the concentration of (137)Cs in milk, the transfer coefficient from feed to milk, F(m), is an important parameter. Site-specific transfer coefficient from feed to cow's milk, for (137)Cs in the Kaiga environment, a nuclear power station site in India, determined over a period of 10 y is presented in this paper. The value is determined from (137)Cs concentration in milk and grass samples of the Kaiga region and the result ranged from 6.43E-03 to 1.09E-02 d l(-1) with a geometric mean value of 8.0E-03 d l(-1). The result is compared with that for (40)K, determined concurrently at the same region and ranged from 3.06E-03 to 3.48E-03 d l(-1) with a geometric mean value of 3.26E-03 d l(-1). This parameter is quite useful in decision-making for implementing countermeasures during a large area contamination with (137)Cs in tropical areas like Kaiga. PMID:21685495
NASA Astrophysics Data System (ADS)
Crow, Wade T.; Kustas, William P.
2005-04-01
Recent advances in land data assimilation have yielded variational smoother techniques designed to solve the surface energy balance based on remote observations of surface radiometric temperature. These approaches have a number of potential advantages over existing diagnostic models, including the ability to make energy flux predictions between observation times and reduced requirements for ancillary parameter estimation. Here, the performance of a recently developed variational smoother approach is examined in detail over a range of vegetative and hydrological conditions in the southern U.S.A. during the middle part of the growing season. Smoother results are compared with flux tower observations and energy balance predictions obtained from the two-source energy balance model (TSM). The variational approach demonstrates promise for flux retrievals at dry and lightly vegetated sites. However, results suggest that the simultaneous retrieval of both evaporative fraction and turbulent transfer coefficients by the variational approach will be difficult for wet and/or heavily vegetated land surfaces. Additional land surface information (e.g. leaf area index ( L AI) or the rough specification of evaporative fraction bounds) will be required to ensure robust predictions under such conditions. The single-source nature of the variational approach also hampers the physical interpretation of turbulent transfer coefficient retrievals. Intercomparisons between energy flux predictions from the variational approach and the purely diagnostic TSM demonstrate that the relative accuracy of each approach is contingent on surface conditions and the accuracy with which L AI values required by the TSM can be estimated.
Dissolved oxygen transfer to sediments by sweep and eject motions in aquatic environments
O'Connor, B.L.; Hondzo, Miki
2008-01-01
Dissolved oxygen (DO) concentrations were quantified near the sediment-water interface to evaluate DO transfer to sediments in a laboratory recirculating flume and open channel under varying fluid-flow conditions. DO concentration fluctuations were observed within the diffusive sublayer, as defined by the time-averaged DO concentration gradient near the sediment-water interface. Evaluation of the DO concentration fluctuations along with detailed fluid-flow characterizations were used to quantify quasi-periodic sweep and eject motions (bursting events) near the sediments. Bursting events dominated the Reynolds shear stresses responsible for momentum and mass fluctuations near the sediment bed. Two independent methods for detecting bursting events using DO concentration and velocity data produced consistent results. The average time between bursting events was scaled with wall variables and was incorporated into a similarity model to describe the dimensionless mass transfer coefficient (Sherwood number, Sh) in terms of the Reynolds number, Re, and Schmidt number, Sc, which described transport in the flow. The scaling of bursting events was employed with the similarity model to quantify DO transfer to sediments and results showed a high degree of agreement with experimental data. ?? 2008, by the American Society of Limnology and Oceanography, Inc.
Turbulent transfer coefficient and roughness length in a high-altitude lake, Tibetan Plateau
NASA Astrophysics Data System (ADS)
Li, Zhaoguo; Lyu, Shihua; Zhao, Lin; Wen, Lijuan; Ao, Yinhuan; Wang, Shaoying
2016-05-01
A persistent unstable atmospheric boundary layer was observed over Lake Ngoring, caused by higher temperature on the water surface compared with the overlying air. Against this background, the eddy covariance flux data collected from Lake Ngoring were used to analyse the variation of transfer coefficients and roughness lengths for momentum, heat and moisture. Results are discussed and compared with parameterization schemes in a lake model. The drag coefficient and momentum roughness length rapidly decreased with increasing wind velocity, reached a minimum value in the moderate wind velocity and then increased slowly as wind velocity increased further. Under weak wind conditions, the surface tension or small scale capillary wave becomes more important and increases the surface roughness. The scalar roughness length ratio was much larger than unity under weak wind conditions, and it decreased to values near unity as wind velocity exceeded 4.0 m s-1. The lake model could not reproduce well the variation of drag coefficient, or momentum roughness length, versus wind velocity in Lake Ngoring, but it did simulate well the sensible heat and latent heat fluxes, as a result of complementary opposite errors.
Electrocatalysis of anodic oxygen-transfer reactions: Evolution of ozone
Feng, J.; Johnson, D.C. ); Lowery, S.N.; Carey, J.J. . Kodak Research Labs.)
1994-10-01
Current efficiencies are compared for the generation of O[sub 3] simultaneously with O[sub 2] during anodic discharge of H[sub 2]O at pure and iron(III)-doped [beta]-lead dioxide film electrodes in phosphate buffer (pH 7.5, 10 C) containing 2.5 mM KF. Also examined is the effect of applied current density. A current efficiency of 14.6% was obtained for the Fe(III)-doped PbO[sub 2] film electrode deposited on a internally cooled (10 C) tubular titanium substrate at a current density of 200 mA cm[sup [minus]2] as compared to only 6.1% at the undoped PbO[sub 2] electrode under the same conditions. This result is tentatively explained on the basis of a mechanism involving the transfer of oxygen from hydroxyl radicals adsorbed on Pb(IV) sites adjacent to Fe(III) sites to O[sub 2] adsorbed at the Fe(III) sites in the surface of the Fe(III)-doped PbO[sub 2] electrodes.
NASA Astrophysics Data System (ADS)
Chabi, A. R.; Zarrinabadi, S.; Peyghambarzadeh, S. M.; Hashemabadi, S. H.; Salimi, M.
2016-06-01
Forced convective heat transfer in a microchannel heat sink (MCHS) using CuO/water nanofluids with 0.1 and 0.2 vol% as coolant was investigated. The experiments were focused on the heat transfer enhancement in the channel entrance region at Re < 1800. Hydraulic performance of the MCHS was also estimated by measuring friction factor and pressure drop. Results showed that higher convective heat transfer coefficient was obtained at the microchannel entrance. Maximum enhancement of the average heat transfer coefficient compared with deionized water was about 40 % for 0.2 vol% nanofluid at Re = 1150. Enhancement of the convective heat transfer coefficient of nanofluid decreased with further increasing of Reynolds number.
Hindasageri, V; Vedula, R P; Prabhu, S V
2013-02-01
Temperature measurement by thermocouples is prone to errors due to conduction and radiation losses and therefore has to be corrected for precise measurement. The temperature dependent emissivity of the thermocouple wires is measured by the use of thermal infrared camera. The measured emissivities are found to be 20%-40% lower than the theoretical values predicted from theory of electromagnetism. A transient technique is employed for finding the heat transfer coefficients for the lead wire and the bead of the thermocouple. This method does not require the data of thermal properties and velocity of the burnt gases. The heat transfer coefficients obtained from the present method have an average deviation of 20% from the available heat transfer correlations in literature for non-reacting convective flow over cylinders and spheres. The parametric study of thermocouple error using the numerical code confirmed the existence of a minimum wire length beyond which the conduction loss is a constant minimal. Temperature of premixed methane-air flames stabilised on 16 mm diameter tube burner is measured by three B-type thermocouples of wire diameters: 0.15 mm, 0.30 mm, and 0.60 mm. The measurements are made at three distances from the burner tip (thermocouple tip to burner tip/burner diameter = 2, 4, and 6) at an equivalence ratio of 1 for the tube Reynolds number varying from 1000 to 2200. These measured flame temperatures are corrected by the present numerical procedure, the multi-element method, and the extrapolation method. The flame temperatures estimated by the two-element method and extrapolation method deviate from numerical results within 2.5% and 4%, respectively. PMID:23464237
NASA Astrophysics Data System (ADS)
Hindasageri, V.; Vedula, R. P.; Prabhu, S. V.
2013-02-01
Temperature measurement by thermocouples is prone to errors due to conduction and radiation losses and therefore has to be corrected for precise measurement. The temperature dependent emissivity of the thermocouple wires is measured by the use of thermal infrared camera. The measured emissivities are found to be 20%-40% lower than the theoretical values predicted from theory of electromagnetism. A transient technique is employed for finding the heat transfer coefficients for the lead wire and the bead of the thermocouple. This method does not require the data of thermal properties and velocity of the burnt gases. The heat transfer coefficients obtained from the present method have an average deviation of 20% from the available heat transfer correlations in literature for non-reacting convective flow over cylinders and spheres. The parametric study of thermocouple error using the numerical code confirmed the existence of a minimum wire length beyond which the conduction loss is a constant minimal. Temperature of premixed methane-air flames stabilised on 16 mm diameter tube burner is measured by three B-type thermocouples of wire diameters: 0.15 mm, 0.30 mm, and 0.60 mm. The measurements are made at three distances from the burner tip (thermocouple tip to burner tip/burner diameter = 2, 4, and 6) at an equivalence ratio of 1 for the tube Reynolds number varying from 1000 to 2200. These measured flame temperatures are corrected by the present numerical procedure, the multi-element method, and the extrapolation method. The flame temperatures estimated by the two-element method and extrapolation method deviate from numerical results within 2.5% and 4%, respectively.
NASA Astrophysics Data System (ADS)
Sharifi Haddad, Amin
characterize the slope of the linear function for different rock geometries. The final part of the study is the development of a lumped mass transfer coefficient between fractures and rock matrix blocks with different geometries. The obtained lumped mass transfer coefficient confirms that the scale of study, dispersivity, and the rate of injection of the fluid into the wellbore are important variables in solute transport in fractured rocks.
Heat transfer coefficient for flow boiling in an annular mini gap
NASA Astrophysics Data System (ADS)
Hożejowska, Sylwia; Musiał, Tomasz; Piasecka, Magdalena
2016-03-01
The aim of this paper was to present the concept of mathematical models of heat transfer in flow boiling in an annular mini gap between the metal pipe with enhanced exterior surface and the external glass pipe. The one- and two-dimensional mathematical models were proposed to describe stationary heat transfer in the gap. A set of experimental data governed both the form of energy equations in cylindrical coordinates and the boundary conditions. The models were formulated to minimize the number of experimentally determined constants. Known temperature distributions in the enhanced surface and in the fluid helped to determine, from the Robin condition, the local heat transfer coefficients at the enhanced surface - fluid contact. The Trefftz method was used to find two-dimensional temperature distributions for the thermal conductive filler layer, enhanced surface and flowing fluid. The method of temperature calculation depended on whether the area of single-phase convection ended with boiling incipience in the gap or the two-phase flow region prevailed, with either fully developed bubbly flow or bubbly-slug flow. In the two-phase flow, the fluid temperature was calculated by Trefftz method. Trefftz functions for the Laplace equation and for the energy equation were used in the calculations.
Leung, Juliana Y; Srinivasan, Sanjay
2016-09-01
Modeling transport process at large scale requires proper scale-up of subsurface heterogeneity and an understanding of its interaction with the underlying transport mechanisms. A technique based on volume averaging is applied to quantitatively assess the scaling characteristics of effective mass transfer coefficient in heterogeneous reservoir models. The effective mass transfer coefficient represents the combined contribution from diffusion and dispersion to the transport of non-reactive solute particles within a fluid phase. Although treatment of transport problems with the volume averaging technique has been published in the past, application to geological systems exhibiting realistic spatial variability remains a challenge. Previously, the authors developed a new procedure where results from a fine-scale numerical flow simulation reflecting the full physics of the transport process albeit over a sub-volume of the reservoir are integrated with the volume averaging technique to provide effective description of transport properties. The procedure is extended such that spatial averaging is performed at the local-heterogeneity scale. In this paper, the transport of a passive (non-reactive) solute is simulated on multiple reservoir models exhibiting different patterns of heterogeneities, and the scaling behavior of effective mass transfer coefficient (Keff) is examined and compared. One such set of models exhibit power-law (fractal) characteristics, and the variability of dispersion and Keff with scale is in good agreement with analytical expressions described in the literature. This work offers an insight into the impacts of heterogeneity on the scaling of effective transport parameters. A key finding is that spatial heterogeneity models with similar univariate and bivariate statistics may exhibit different scaling characteristics because of the influence of higher order statistics. More mixing is observed in the channelized models with higher-order continuity. It
NASA Astrophysics Data System (ADS)
Leung, Juliana Y.; Srinivasan, Sanjay
2016-09-01
Modeling transport process at large scale requires proper scale-up of subsurface heterogeneity and an understanding of its interaction with the underlying transport mechanisms. A technique based on volume averaging is applied to quantitatively assess the scaling characteristics of effective mass transfer coefficient in heterogeneous reservoir models. The effective mass transfer coefficient represents the combined contribution from diffusion and dispersion to the transport of non-reactive solute particles within a fluid phase. Although treatment of transport problems with the volume averaging technique has been published in the past, application to geological systems exhibiting realistic spatial variability remains a challenge. Previously, the authors developed a new procedure where results from a fine-scale numerical flow simulation reflecting the full physics of the transport process albeit over a sub-volume of the reservoir are integrated with the volume averaging technique to provide effective description of transport properties. The procedure is extended such that spatial averaging is performed at the local-heterogeneity scale. In this paper, the transport of a passive (non-reactive) solute is simulated on multiple reservoir models exhibiting different patterns of heterogeneities, and the scaling behavior of effective mass transfer coefficient (Keff) is examined and compared. One such set of models exhibit power-law (fractal) characteristics, and the variability of dispersion and Keff with scale is in good agreement with analytical expressions described in the literature. This work offers an insight into the impacts of heterogeneity on the scaling of effective transport parameters. A key finding is that spatial heterogeneity models with similar univariate and bivariate statistics may exhibit different scaling characteristics because of the influence of higher order statistics. More mixing is observed in the channelized models with higher-order continuity. It
NASA Technical Reports Server (NTRS)
Brown, W Byron; Esgar, Jack B
1950-01-01
Analytical methods are presented for the determination of local values of outside and inside heat-transfer coefficients and effective gas temperatures by use of turbine-blade-temperature measurements. The methods are derived for a number of configurations that can be applied to typical cooled-turbine-blade shapes as well as to other types of heat-transfer apparatus.
Buoyancy flux, turbulence, and the gas transfer coefficient in a stratified lake
NASA Astrophysics Data System (ADS)
MacIntyre, Sally; Jonsson, Anders; Jansson, Mats; Aberg, Jan; Turney, Damon E.; Miller, Scott D.
2010-12-01
Gas fluxes from lakes and other stratified water bodies, computed using conservative values of the gas transfer coefficient k600, have been shown to be a significant component of the carbon cycle. We present a mechanistic analysis of the dominant physical processes modifying k600 in a stratified lake and resulting new models of k600 whose use will enable improved computation of carbon fluxes. Using eddy covariance results, we demonstrate that i) higher values of k600 occur during low to moderate winds with surface cooling than with surface heating; ii) under overnight low wind conditions k600 depends on buoyancy flux β rather than wind speed; iii) the meteorological conditions at the time of measurement and the inertia within the lake determine k600; and iv) eddy covariance estimates of k600 compare well with predictions of k600 using a surface renewal model based on wind speed and β.
NASA Astrophysics Data System (ADS)
Zhang, Liqiang; Li, Luoxing
2013-08-01
The present work focuses on the determination of interfacial heat transfer coefficients (IHTCs) between the casting and metal chill during casting solidification. The proposed method is established based on the least-squares technique and sequential function specification method and can be applied to calculate heat fluxes and IHTCs for other alloys. The accuracy and stability of the method has been investigated by using a typical profile of heat fluxes simulating the practical conditions of casting solidification. In the test process, the effects of various calculation parameters in the inverse algorithm are also analyzed. Moreover, numerically calculated and experimental results are compared by applying the determined IHTCs into the forward heat conduction model with the same boundary conditions. The results show that the numerically calculated temperatures are in good agreement with those measured experimentally. This confirms that the proposed method is a feasible and effective tool for determination of the casting-mold IHTCs.
NASA Astrophysics Data System (ADS)
Lee, Haw-Long; Chang, Win-Jin; Chen, Wen-Lih; Yang, Yu-Ching
2012-06-01
This paper numerically investigates the hyperbolic thermoelastic problem of an annular fin. The ambient convection heat transfer coefficient of the fin is assumed to be spatially varying. The major difficulty in dealing with such problems is the suppression of numerical oscillations in the vicinity of a jump discontinuity. An efficient numerical scheme involving hybrid application of Laplace transform and control volume method in conjunction with hyperbolic shape functions is used to solve the linear hyperbolic heat conduction equation. The transformed nodal temperatures are inverted to the physical quantities by using numerical inversion of the Laplace transform. Then the stress distributions in the annular fin are calculated subsequently. The results in the illustrated examples show that the application of hyperbolic shape functions can successfully suppress the numerical oscillations in the vicinity of jump discontinuities.
NASA Astrophysics Data System (ADS)
Cao, Yongyou; Guo, Zhipeng; Xiong, Shoumei
2012-07-01
High-pressure die cast B390 alloy was prepared on a 350 ton cold chamber die casting machine. The metal/die interfacial heat transfer coefficient of the alloy was investigated. Considering the filling process, a "finger"-shaped casting was designed for the experiments. This casting consisted of five plates with different thicknesses (0.05 inch or 1.27 mm to 0.25 inch or 6.35 mm) as well as individual ingates and overflows. Experiments under various operation conditions were conducted, and temperatures were measured at various specific locations inside the die. Based on the results, the interfacial heat transfer coefficient and heat flux were determined by solving the inverse heat transfer problem. The influence of the mold-filling sequence, sensor locations, as well as processing parameters including the casting pressure, die temperature, and fast/slow shot speeds on the heat transfer coefficient were discussed.
NASA Astrophysics Data System (ADS)
Vacca, Santiago; Martorano, Marcelo A.; Heringer, Romulo; Boccalini, Mário
2015-05-01
The heat transfer coefficient at the metal-mold interface ( h MM) has been determined for the first time during the centrifugal casting of a Fe-C alloy tube using the inverse solution method. To apply this method, a centrifugal casting experiment was carried out to measure cooling curves within the tube wall under a mold rotation speed of 900 rpm, imposing a centrifugal force 106 times as large as the gravity force (106 G). As part of the solution method, a comprehensive heat transfer model of the centrifugal casting was also developed and coupled to an optimization algorithm. Finally, the evolution of h MM with time that gives the minimum squared error between measured and calculated cooling curves was obtained. The determined h MM is approximately 870 W m-2 K-1 immediately after melt pouring, decreasing to about 50 W m-2 K-1 when the average temperature of the tube is ~973 K (700 °C), after the end of solidification. Despite the existence of a centrifugal force that could enhance the metal-mold contact, these values are lower than those generally reported for static molds with or without an insulating coating at the mold inner surface. The implemented model shows that the heat loss by radiation is dominant over that by convection at the tube inner surface, causing the formation of a solidification front that meets another front coming from the outer surface of the tube.
Local Mass Transfer Coefficient for Idealized 2D Urban Street Canyon Models
NASA Astrophysics Data System (ADS)
Leung, Ka Kit; Liu, Chun-Ho
2011-09-01
Human activities in urban areas is one of the major sources of anthropogenic releases in the atmospheric boundary layer (ABL). The mechanism of urban morphology for the heat and mass transfer in built environment is thus an attractive topic in the research community. In this paper, a series of laboratory measurements is conducted to elucidate the mass transfer from hypothetical urban roughness constructed by idealized 2D street canyons. The experiments are carried out in the wind tunnel in the University of Hong Kong. The urban ABL structure inside the wind tunnel is controlled by placing small cubic Styrofoam blocks upstream of the test section. The street canyons are fabricated by movable rectangular acrylic blocks so that different building height to street width (aspect) ratios are examined. The height of building blocks is kept minimum to make sure that the urban ABL over the street canyons is high enough for fully developed turbulent flows. The prevailing wind is normal to the street axis, demonstrating the scenario of least pollutant removal from the street canyons to the urban ABL. The sample street canyon is covered by soaked filter papers to represent uniform mass concentrations on the building facades and ground surface. The wet bulb temperature of the filter papers is continuously monitored to ensure saturated conditions. Their weight before and after an experiment is used to measure the amount of water evaporated. Preliminary results illustrate the local mass transfer coefficient distribution for aspect ratios 1/4, 1/2, 1, and 2, which are comparable with those available in literuatre.
NASA Astrophysics Data System (ADS)
Thoo, K. K.; Chin, W. M.; Heikal, M. R.
2013-12-01
In this study, the air side heat transfer coefficient of an aluminium mini-channel heat exchanger was investigated for single-phase flow in the mini-channel, with water in the tubes and air on the outside. Research methods included hydraulic tests on a single mini-channel tube, Wilson Plot experiments and experiment validation. Results obtained from the hydraulic test showed that turbulent flow occurred in the tube at a Reynolds number of 830. Wilson Plot experiments were conducted to determine air side heat transfer coefficient of the heat exchanger. The tube side Reynolds number was maintained above 1000 to ensure turbulent flow and tube side heat transfer coefficient was calculated using Gnielinski equation for turbulent flow. The air side heat transfer coefficients obtained from the Wilson Plot experiments were in good agreement with known correlations. The outcome of this study is to use the air side heat transfer coefficient to calculate the performance of refrigerant condensers for different tube pass ratios and flow pass configurations.
Revised model coefficients for vibrational relaxation in a nitrogen-oxygen gas mixture
NASA Astrophysics Data System (ADS)
Gehre, R. M.; Wheatley, V.; Boyce, R. R.
2012-11-01
A numerical investigation of thermal non-equilibrium flows requires species specific relaxation rates, which are often calculated using the Landau-Teller model. This model requires the determination of collision specific relaxation times, which can be computed using Millikan and White's empirical formula. The coefficients used in this formula for each specific collision pair form a set of coefficients, which are assessed here. The focus of the investigation lies on their performance in hypersonic low-temperature (300-2,500 K) flows that occur at shock-tunnel nozzle exits or in supersonic combustion ramjets (scramjets) before combustion. Two experimental validation cases are chosen; a shock-tunnel nozzle and a sharp cone in hypersonic cross-flow experiment. A comparison of the experimentally measured vibrational temperatures at the nozzle exit against numerical data shows large discrepancies for two commonly used coefficient sets. A revised set of coefficients is proposed that greatly improves the agreement between the numerical and experimental results. Furthermore, the numerically generated shock shape over the sharp cone using the revised set of coefficients correlates well with the experimental measurements.
Improved oxygen mass transfer modeling for diffused or subsurface aeration systems
McWhirter, J.R.; Hutter, J.C. . Dept. of Chemical Engineering)
1988-01-01
The mass transfer analysis of the oxygen transfer performance of diffused air or subsurface mechanical aeration systems has progressed very little over the past twenty years. The ASCE Standard Method for determination of the oxygen mass transfer performance as applied to a diffused or subsurface aeration systems is based on a greatly over-simplified mass transfer model. Although the ASCE Standard can be used to empirically evaluate point performance conditions, it is not suitable for prediction of the performance of diffused aeration systems under changing operating or environmental conditions. A new oxygen mass transfer model has been developed which is a fundamentally more rigorous description of the actual mass transfer process in diffused aeration systems. This model can be confidently used to predict aerator performance under changing operation and environmental conditions and is easily adapted to numerical solution on a computer for routing aeration system performance evaluation as well as process design. The model is presented in this book.
Oxygen transfer in marsh-pond-marsh constructed wetlands treating swine wastewater.
Ro, Kyoung S; Hunt, Patrick G; Johnson, Melvin H; Matheny, Terry A; Forbes, Dean; Reddy, Gudigopuram B
2010-01-01
Oxygen transfer efficiencies of various components of the marsh-pond-marsh (M-P-M) and marsh-floating bed-marsh (M-FB-M) wetlands treating swine wastewater were determined by performing oxygen mass balance around the wetlands. Biological oxygen demand (BOD) and total nitrogen (TN) loading and escaping rates from each wetland were used to calculate carbonaceous and nitrogenous oxygen demands. Ammonia emissions were measured using a wind tunnel. Oxygen transfer efficiencies of the aerated ponds were estimated by conducting the ASCE standard oxygen transfer test in a tank using the same aeration device. Covering pond water surface with the floating bed slightly decreased oxygen transfer efficiency. The diffused membrane aeration (26.7 kg O2 ha-1 d-1) of M-P-M was surprisingly not as effective as plant aeration in the marsh (38.9 to 42.0 kg O2 ha-1 d-1). This unusually low oxygen transfer efficiency of the diffused aeration was attributed to its low submergence depth of 0.8 m compared to typical depth of 4.5 m. The wetlands consisting entirely of marsh removed similar amounts of C and N without investing additional equipment and energy costs of aerating ponds in the middle of wetlands. PMID:20390880
Orbit transfer rocket engine technology program: Oxygen materials compatibility testing
NASA Technical Reports Server (NTRS)
Schoenman, Leonard
1989-01-01
Particle impact and frictional heating tests of metals in high pressure oxygen, are conducted in support of the design of an advanced rocket engine oxygen turbopump. Materials having a wide range of thermodynamic properties including heat of combustion and thermal diffusivity were compared in their resistance to ignition and sustained burning. Copper, nickel and their alloys were found superior to iron based and stainless steel alloys. Some materials became more difficult to ignite as oxygen pressure was increased from 7 to 21 MPa (1000 to 3000 psia).
Sengupta, S.; Sherif, S.A.; Wong, K.V.
1995-12-31
This paper reports on results of an experimental investigation where the emphasis was placed on obtaining empirical correlations for the frost thickness-time history and the heat transfer coefficient-time history for a cylinder in humid air cross flow. The facility employed for the investigation consisted of a low velocity wind tunnel comprised of a rectangular test section, a transition section and a honeycomb placed at the tunnel entrance. An external refrigerator was used to cool an antifreeze solution having a mixture of 90% methanol and 10% ethylene glycol. Measured parameters included, among other things, the heat transfer coefficient as well as the frost thickness.
NASA Astrophysics Data System (ADS)
Piasecka, Magdalena; Maciejewska, Beata
2015-05-01
The paper presents flow boiling heat transfer of FC-72 in 1 mm depth, 40 mm width minichannel where a foil with evenly distributed recesses on one side acts as a heating surface. The minichannel is set at various angles, i.e. 0, 45, 90, 135 and 180 degrees inclinations in relation to the horizontal plane. The plain side of the foil is observed to determine the surface temperature by liquid crystal thermography. Two heat transfer models: one- and two-dimensional are proposed to calculate local heat transfer coefficients. In the two-dimensional approach the inverse problem in the heating wall is solved by the semi-analytical method based on Trefftz functions in subareas, abbreviated to the nodeless Trefftz method. Local values of heat transfer coefficient on the surface between the heating foil and boiling liquid were calculated on the basis of the third-kind boundary condition. The influence of minichannel orientation on heat transfer coefficient at boiling incipience region values were analyzed. The same tendencies in the results were observed for the two applied methods. The one-dimensional approach seems to be less sensitive to measurement errors. The polynomial smoothing of the results applied in the two-dimensional method can affect the rounding values of coefficient.
Oxygen Transfer in a Fluctuating Capillary Fringe: Impact of Porous Medium Heterogeneity
NASA Astrophysics Data System (ADS)
Haberer, C.; Rolle, M.; Cirpka, O. A.; Grathwohl, P.
2013-12-01
Mass transfer of oxygen from the atmosphere, across the capillary fringe, to anoxic groundwater is of primary importance for many biogeochemical processes affecting groundwater quality. The controlling mechanisms for oxygen transfer across the capillary fringe are the diffusive/dispersive transport as well as mass exchange between entrapped air and groundwater. In addition, the presence of physical heterogeneity in the porous medium may strongly affect the oxygen fluxes. We performed quasi two-dimensional flow-through experiments at the laboratory bench-scale to study the effect of a coarse-material inclusion, located in proximity of the water table, on flow and oxygen transfer in the capillary fringe. Flow and transport were monitored under both steady-state and transient flow conditions, the latter obtained by fluctuating the water table. We visually inspected the complex flow field using a dye tracer solution, measured vertical oxygen profiles across the capillary fringe at high spatial resolution, and determined oxygen fluxes in the effluent of the flow-through chamber. Our results show that the coarse-material inclusion significantly affected oxygen transfer during the different phases of the experiments. At steady state, the oxygen flux across the unsaturated/saturated interface was considerably enhanced due to flow focusing in the fully water-saturated coarse lens. During drainage, the capillary barrier effect prevented water to drain from the fine material overlying the coarse lens. The entrapped oxygen-rich aqueous phase contributed to the total amount of oxygen supplied to the system when the water table was raised back to its initial level. In case of imbibition, also pronounced entrapment of air occurred in the coarse lens, causing oxygen to partition between the aqueous and gaseous phases. Thus, we found that oxygen transfer across the capillary fringe was significantly enhanced by the coarse-material inclusion due to flow focusing, the capillary
Experimentally Determined Overall Heat Transfer Coefficients for Spacesuit Liquid Cooled Garments
NASA Technical Reports Server (NTRS)
Bue, Grant; Rhodes, Richard; Anchondo, Ian; Westheimer, David; Campbell, Colin; Vogel, Matt; Vonaue, Walt; Conger, Bruce; Stein, James
2015-01-01
A Human-In-The-Loop (HITL) Portable Life Support System 2.0 (PLSS 2.0) test has been conducted at NASA Johnson Space Center in the PLSS Development Laboratory from October 27, 2014 to December 19, 2014. These closed-loop tests of the PLSS 2.0 system integrated with human subjects in the Mark III Suit at 3.7 psi to 4.3 psi above ambient pressure performing treadmill exercise at various metabolic rates from standing rest to 3000 BTU/hr (880 W). The bulk of the PLSS 2.0 was at ambient pressure but effluent water vapor from the Spacesuit Water Membrane Evaporator (SWME) and the Auxiliary Membrane Evaporator (Mini-ME), and effluent carbon dioxide from the Rapid Cycle Amine (RCA) were ported to vacuum to test performance of these components in flight-like conditions. One of the objectives of this test was to determine the overall heat transfer coefficient (UA) of the Liquid Cooling Garment (LCG). The UA, an important factor for modeling the heat rejection of an LCG, was determined in a variety of conditions by varying inlet water temperature, flow rate, and metabolic rate. Three LCG configurations were tested: the Extravehicular Mobility Unit (EMU) LCG, the Oceaneering Space Systems (OSS) LCG, and the OSS auxiliary LCG. Other factors influencing accurate UA determination, such as overall heat balance, LCG fit, and the skin temperature measurement, will also be discussed.
Cloutier, N.R.; Clulow, F.V.; Lim, T.P.; Dave, N.K.
1986-06-01
The 226Ra level in vegetation growing on U mine tailings in Elliot Lake, Ontario, Canada, was 211 + 22 mBq g-1 (dry weight) compared to less than 7 mBq g-1 (dry weight) in material from a control site. Skeletons of meadow voles (Microtus pennsylvanicus) established on the tailings had concentrations of 226Ra of 6083 +/- 673 mBq per animal in winter; 7163 +/- 1077 mBq per animal in spring; 1506 +/- 625 mBq per animal in summer; and 703 +/- 59 mBq per animal in fall, compared to less than 7 mBq per animal in controls. The /sup 226/Ra transfer coefficient from vegetation to voles (defined as total millibecquerels of /sup 226/Ra in adult vole per total millibecquerels of 226Ra consumed by the vole in its lifetime) was calculated as 4.6 +/- 2.9 X 10(-2) in summer and 2.8 +/- 0.6 X 10(-2) in fall.
Giese, Heiner; Azizan, Amizon; Kümmel, Anne; Liao, Anping; Peter, Cyril P; Fonseca, João A; Hermann, Robert; Duarte, Tiago M; Büchs, Jochen
2014-02-01
In biotechnological screening and production, oxygen supply is a crucial parameter. Even though oxygen transfer is well documented for viscous cultivations in stirred tanks, little is known about the gas/liquid oxygen transfer in shake flask cultures that become increasingly viscous during cultivation. Especially the oxygen transfer into the liquid film, adhering on the shake flask wall, has not yet been described for such cultivations. In this study, the oxygen transfer of chemical and microbial model experiments was measured and the suitability of the widely applied film theory of Higbie was studied. With numerical simulations of Fick's law of diffusion, it was demonstrated that Higbie's film theory does not apply for cultivations which occur at viscosities up to 10 mPa s. For the first time, it was experimentally shown that the maximum oxygen transfer capacity OTRmax increases in shake flasks when viscosity is increased from 1 to 10 mPa s, leading to an improved oxygen supply for microorganisms. Additionally, the OTRmax does not significantly undermatch the OTRmax at waterlike viscosities, even at elevated viscosities of up to 80 mPa s. In this range, a shake flask is a somehow self-regulating system with respect to oxygen supply. This is in contrary to stirred tanks, where the oxygen supply is steadily reduced to only 5% at 80 mPa s. Since, the liquid film formation at shake flask walls inherently promotes the oxygen supply at moderate and at elevated viscosities, these results have significant implications for scale-up. PMID:23904288
Orbital transfer vehicle oxygen turbopump technology. Volume 3: Hot oxygen testing
NASA Technical Reports Server (NTRS)
Urke, Robert L.
1992-01-01
This report covers the work done in preparation for a liquid oxygen rocket engine turbopump test utilizing high pressure hot oxygen gas for the turbine drive. The turbopump (TPA) is designed to operate with 400 F oxygen turbine drive gas. The goal of this test program was to demonstrate the successful operation of the TPA under simulated engine conditions including the hot oxygen turbine drive. This testing follows a highly successful series of tests pumping liquid oxygen with gaseous nitrogen as the turbine drive gas. That testing included starting of the TPA with no assist to the hydrostatic bearing. The bearing start entailed a rubbing start until the pump generated enough pressure to support the bearing. The articulating, self-centering hydrostatic bearing exhibited no bearing load or stability problems. The TPA was refurbished for the hot gas drive tests and facility work was begun, but unfortunately funding cuts prohibited the actual testing.
Improvement of foam breaking and oxygen-transfer performance in a stirred-tank fermenter.
Takesono, Satoshi; Onodera, Masayuki; Toda, Kiyoshi; Yoshida, Masanori; Yamagiwa, Kazuaki; Ohkawa, Akira
2006-03-01
This study examined a stirred-tank fermenter (STF) containing low-viscosity foaming liquids with an agitation impeller and foam-breaking impeller mounted on the same shaft. Results showed that the performance of the foam-breaking impeller can be improved by changing a conventional six-blade turbine impeller into a rod impeller as the agitation impeller. The volumetric oxygen-transfer coefficient, kLa, in the mechanical foam-control method (MFM) using a six-blade vaned disk as the foam-breaking impeller in the STF with the rod impeller was approximately five times greater than that of the chemical foam-control method (CFM) adding an anti-foaming agent in the STF with the six-blade turbine impeller. Application of the present method to the cultivation of Saccharomyces cerevisiae K-7 demonstrated that the cultivation time up to the maximum cell concentration was remarkably shorter than that achieved using a conventional CFM. PMID:16208498
NASA Technical Reports Server (NTRS)
Donegan, James J; Robinson, Samuel W , Jr; Gates, Ordway, B , jr
1955-01-01
A method is presented for determining the lateral-stability derivatives, transfer-function coefficients, and the modes for lateral motion from frequency-response data for a rigid aircraft. The method is based on the application of the vector technique to the equations of lateral motion, so that the three equations of lateral motion can be separated into six equations. The method of least squares is then applied to the data for each of these equations to yield the coefficients of the equations of lateral motion from which the lateral-stability derivatives and lateral transfer-function coefficients are computed. Two numerical examples are given to demonstrate the use of the method.
NASA Technical Reports Server (NTRS)
Porro, A. Robert; Keith, Theo G., Jr.; Hingst, Warren R.; Chriss, Randall M.; Seablom, Kirk D.
1991-01-01
A technique is developed to measure the local convective heat transfer coefficient on a model surface in a supersonic flow field. The technique uses a laser to apply a discrete local heat flux at the model test surface, and an infrared camera system determines the local temperature distribution due to heating. From this temperature distribution and an analysis of the heating process, a local convective heat transfer coefficient is determined. The technique was used to measure the load surface convective heat transfer coefficient distribution on a flat plate at nominal Mach numbers of 2.5, 3.0, 3.5, and 4.0. The flat plate boundary layer initially was laminar and became transitional in the measurement region. The experimental results agreed reasonably well with theoretical predictions of convective heat transfer of flat plate laminar boundary layers. The results indicate that this non-intrusive optical measurement technique has the potential to obtain high quality surface convective heat transfer measurements in high speed flowfields.
NASA Astrophysics Data System (ADS)
Nikkhou, Fatemeh; Keshavarz, Peyman; Ayatollahi, Shahab; Jahromi, Iman Raoofi; Zolghadr, Ali
2014-09-01
CO2 gas injection is known as one of the most popular enhanced oil recovery techniques for light and medium oil reservoirs, therefore providing an acceptable mass transfer mechanism for CO2-oil systems seems necessary. In this study, interfacial mass transfer coefficient has been evaluated for CO2-normal heptane and CO2-normal hexadecane systems using equilibrium and dynamic interfacial tension data, which have been measured using the pendant drop method. Interface mass transfer coefficient has been calculated as a function of temperature and pressure in the range of 313-393 K and 1.7-8.6 MPa, respectively. The results showed that the interfacial resistance is a parameter that can control the mass transfer process for some CO2-normal alkane systems, and cannot be neglected. Additionally, it was found that interface mass transfer coefficient increased with pressure. However, the variation of this parameter with temperature did not show a clear trend and it was strongly dependent on the variation of diffusivity and solubility of CO2 in the liquid phase.
NASA Astrophysics Data System (ADS)
Nikkhou, Fatemeh; Keshavarz, Peyman; Ayatollahi, Shahab; Jahromi, Iman Raoofi; Zolghadr, Ali
2015-04-01
CO2 gas injection is known as one of the most popular enhanced oil recovery techniques for light and medium oil reservoirs, therefore providing an acceptable mass transfer mechanism for CO2-oil systems seems necessary. In this study, interfacial mass transfer coefficient has been evaluated for CO2-normal heptane and CO2-normal hexadecane systems using equilibrium and dynamic interfacial tension data, which have been measured using the pendant drop method. Interface mass transfer coefficient has been calculated as a function of temperature and pressure in the range of 313-393 K and 1.7-8.6 MPa, respectively. The results showed that the interfacial resistance is a parameter that can control the mass transfer process for some CO2-normal alkane systems, and cannot be neglected. Additionally, it was found that interface mass transfer coefficient increased with pressure. However, the variation of this parameter with temperature did not show a clear trend and it was strongly dependent on the variation of diffusivity and solubility of CO2 in the liquid phase.
Karunakara, N; Ujwal, P; Yashodhara, I; Rao, Chetan; Sudeep Kumara, K; Dileep, B N; Ravi, P M
2013-10-01
Detailed studies were carried out to establish site-specific soil to grass transfer factors (Fv) and grass to cow milk transfer coefficients (Fm) for radioactive cesium ((137)Cs) and stable cesium (Cs) for Kaiga region, where a nuclear power station has been in operation for more than 10 years. The study included adopted cows, cows of local farmers, and cows from the dairy farm. A grass field was developed specifically for the study and 2 local breed cows were adopted and allowed to graze in this grass field. The soil and grass samples were collected regularly from this field and analyzed for the concentrations of (137)Cs and stable Cs to evaluate the soil to grass Fv values. The milk samples from the adopted cows were analyzed for the (137)Cs and stable Cs concentrations to evaluate Fm values. For comparison, studies were also carried out in dominant grazing areas in different villages around the nuclear power plant and the cows of local farmers which graze in these areas were identified and milk samples were collected and analyzed regularly. The geometric mean values of Fv were found to be 1.1 × 10(-1) and 1.8 × 10(-1) for (137)Cs and stable Cs, respectively. The Fm of (137)Cs had geometric mean values of 1.9 × 10(-2) d L(-1) and 4.6 × 10(-2) d L(-1), respectively, for adopted Cows 1 and 2; 1.7 × 10(-2) d L(-1) for the cows of local farmers, and 4.0 × 10(-3) d L(-1) for the dairy farm cows. The geometric mean values of Fm for stable Cs were similar to those of (137)Cs. The Fm value for the dairy farm cows was an order of magnitude lower than those for local breed cows. The Fm values observed for the local breed cows were also an order of magnitude higher when compared to the many values reported in the literature and in the IAEA publication. Possible reasons for this higher Fm values were identified. The correlation between Fv and Fm values for (137)Cs and stable Cs and their dependence on the potassium content ((40)K and stable K) in
Choi, M F; Hawkins, P
1995-07-01
The contact charge transfer (CCT) absorption spectra of dimethylsulphoxide (DMSO), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), ethanol, methanol, water, benzene (Bz), N,N'-diethylaniline (DEA), N,N'-dimethyl-p-toluidine (DMT) and N,N'-diethyl-p-toluidine with molecular oxygen have been investigated. These solvents form strong ultraviolet/visible CCT absorption spectra with intensities that are related to the partial pressure of the applied oxygen. DMSO, DMF, DMA, Bz, DEA and DMT are shown to form 1:1 molecular contact complexes with molecular oxygen. A simple oxygen sensing system is described using CCT absorption spectroscopy of DMT at a wavelength of 400 nm, with a gas flow rate of 60 cm(3) min(-1) through the solvent in a cuvette with a pathlength of 1 cm. Inexpensive plastic fibres are used to relay the light from a xenon lamp source to the cuvette and back to a photo-detector. The response of the sensing system to changes in oxygen concentration is reversible, non-linear and in good agreement with the Beer-Lambert law. The most sensitive response region is from 0 to 20% O(2) with a change in signal level of about 35%. The solvent used shows no deterioration in performance over a long period and can be used to determine gaseous oxygen concentrations from 0 to 100%. It does not respond to carbon dioxide. PMID:18966322
Data Qualification Report For DTN: MO0012RIB00065.002, Parameter Values For Transfer Coefficients
C.H. Tung
2001-01-09
A data-qualification evaluation was conducted on Reference Information Base (RIB) data set MOO0 12RIB00065.002, ''Parameter Values for Transfer Coefficients''. The corroborating data method was used to evaluate the data. This method was selected because it closely matches the literature-review method followed to select parameter values. Five criteria were considered when the corroborating method was used: adequacy of the corroborative literature, sufficiency of value-selection criteria, implementation of the selection criteria, documentation of the process, and whether the analysis was conducted in accordance with applicable quality assurance (QA) procedures. Three criteria were used when a literature review was not conducted: appropriate logic used to select parameters, documentation of the process, and whether the analysis was conducted in accordance with applicable QA procedures. The RIB data item, the associated Analysis and Model Report (AMR), the corroborative literature, and the results of an audit revision O/ICN 0 of the AMR were examined. All calculations and the selection process for all values were repeated and confirmed. The qualification team concluded: (1) A sufficient quantity of corroborative literature was reviewed and no additional literature was identified that should have been considered. (2) The selection criteria were sufficient and resulted in valid parameter values. (3) The process was well defined, adequately documented in the AMR, and correctly followed. (4) The analysis was developed in accordance with applicable QA procedures. No negative findings were documented that resulted in questions about the quality of the data. The qualification team therefore recommends that the qualification status of RIB data set MO0012RIB00065.002 be changed to qualified.
NASA Astrophysics Data System (ADS)
Baricci, Andrea; Casalegno, Andrea
2016-09-01
Limiting current density of oxygen reduction reaction in polymer electrolyte fuel cells is determined by several mass transport resistances that lower the concentration of oxygen on the catalyst active site. Among them, diffusion across porous media plays a significant role. Despite the extensive experimental activity documented in PEMFC literature, only few efforts have been dedicated to the measurement of the effective transport properties in porous layers. In the present work, a methodology for ex situ measurement of the effective diffusion coefficient and Knudsen radius of porous layers for polymer electrolyte fuel cells (gas diffusion layer, micro porous layer and catalyst layer) is described and applied to high temperature polymer fuel cells State of Art materials. Regression of the measured quantities by means of a quasi 2D physical model is performed to quantify the Knudsen effect, which is reported to account, respectively, for 30% and 50% of the mass transport resistance in micro porous layer and catalyst layer. On the other side, the model reveals that pressure gradient consequent to permeation in porous layers of high temperature polymer fuel cells has a negligible effect on oxygen concentration in relevant operating conditions.
NASA Astrophysics Data System (ADS)
Zhang, Liqiang; Tan, Wenfang; Hu, Hao
2016-06-01
For modeling solidification process of casting accurately, a reliable heat transfer boundary condition data is required. In this paper, an inverse conduction model was established to determine the heat flux and heat transfer coefficient at the metal-sand mold interface for cylindrical casting in the lost foam process. The numerically calculated temperature was compared with analytic solution and simulation solution obtained by commercial software ProCAST to investigate the accuracy of heat conduction model. The instantaneous cast and sand mold temperatures were measured experimentally and these values were used to determine the interfacial heat transfer coefficient (IHTC). The IHTC values during lost foam casting were shown to vary from 20 to 800 W m-2 K-1. Additionally, the characteristics of the time-varying IHTC have also been discussed in this study.
NASA Technical Reports Server (NTRS)
Whitesides, R. Harold; Majumdar, Alok K.; Jenkins, Susan L.; Bacchus, David L.
1990-01-01
A series of cold flow heat transfer tests was conducted with a 7.5-percent scale model of the Space Shuttle Rocket Motor (SRM) to measure the heat transfer coefficients in the separated flow region around the nose of the submerged nozzle. Modifications were made to an existing 7.5 percent scale model of the internal geometry of the aft end of the SRM, including the gimballed nozzle in order to accomplish the measurements. The model nozzle nose was fitted with a stainless steel shell with numerous thermocouples welded to the backside of the thin wall. A transient 'thin skin' experimental technique was used to measure the local heat transfer coefficients. The effects of Reynolds number, nozzle gimbal angle, and model location were correlated with a Stanton number versus Reynolds number correlation which may be used to determine the convective heating rates for the full scale Space Shuttle Solid Rocket Motor nozzle.
Nogueira, Bruno L; Pérez, Julio; van Loosdrecht, Mark C M; Secchi, Argimiro R; Dezotti, Márcia; Biscaia, Evaristo C
2015-09-01
In moving bed biofilm reactors (MBBR), the removal of pollutants from wastewater is due to the substrate consumption by bacteria attached on suspended carriers. As a biofilm process, the substrates are transported from the bulk phase to the biofilm passing through a mass transfer resistance layer. This study proposes a methodology to determine the external mass transfer coefficient and identify the influence of the mixing intensity on the conversion process in-situ in MBBR systems. The method allows the determination of the external mass transfer coefficient in the reactor, which is a major advantage when compared to the previous methods that require mimicking hydrodynamics of the reactor in a flow chamber or in a separate vessel. The proposed methodology was evaluated in an aerobic lab-scale system operating with COD removal and nitrification. The impact of the mixing intensity on the conversion rates for ammonium and COD was tested individually. When comparing the effect of mixing intensity on the removal rates of COD and ammonium, a higher apparent external mass transfer resistance was found for ammonium. For the used aeration intensities, the external mass transfer coefficient for ammonium oxidation was ranging from 0.68 to 13.50 m d(-1) and for COD removal 2.9 to 22.4 m d(-1). The lower coefficient range for ammonium oxidation is likely related to the location of nitrifiers deeper in the biofilm. The measurement of external mass transfer rates in MBBR will help in better design and evaluation of MBBR system-based technologies. PMID:25996756
Orbital transfer vehicle oxygen turbopump technology. Volume 2: Nitrogen and ambient oxygen testing
NASA Technical Reports Server (NTRS)
Brannam, R. J.; Buckmann, P. S.; Chen, B. H.; Church, S. J.; Sabiers, R. L.
1990-01-01
The testing of a rocket engine oxygen turbopump using high pressure ambient temperature nitrogen and oxygen as the turbine drive gas in separate test series is discussed. The pumped fluid was liquid nitrogen or liquid oxygen. The turbopump (TPA) is designed to operate with 400 F oxygen turbine drive gas which will be demonstrated in a subsequent test series. Following bearing tests, the TPA was finish machined (impeller blading and inlet/outlet ports). Testing started on 15 February 1989 and was successfully concluded on 21 March 1989. Testing started using nitrogen to reduce the ignition hazard during initial TPA checkout. The Hydrostatic Bearing System requires a Bearing Pressurization System. Initial testing used a separate bearing supply to prevent a rubbing start. Two test series were successfully completed with the bearing assist supplied only by the pump second stage output which entailed a rubbing start until pump pressure builds up. The final test series used ambient oxygen drive and no external bearing assist. Total operating time was 2268 seconds. There were 14 starts without bearing assist and operating speeds up to 80,000 rpm were logged. Teardown examination showed some smearing of silverplated bearing surfaces but no exposure of the underlying monel material. There was no evidence of melting or oxidation due to the oxygen exposure. The articulating, self-centering hydrostatic bearing exhibited no bearing load or stability problems. The only anomaly was higher than predicted flow losses which were attributed to a faulty ring seal. The TPA will be refurbished prior to the 400 F oxygen test series but its condition is acceptable, as is, for continued operating. This was a highly successful test program.
Kim, Eun-Jin; Sabra, Wael; Zeng, An-Ping
2003-09-01
Pseudomonas aeruginosa PAO1 was recently found to exhibit two remarkable physiological responses to oxidative stress: (1) a strong reduction in the efficiency of oxygen transfer from the gas phase into the liquid phase, thus causing oxygen limitation in the culture and (2) formation of a clear polysaccharide capsule on the cell surface. In this work, it has been shown that the iron concentration in the culture plays a crucial role in evoking these phenomena. The physiological responses of two P. aeruginosa PAO1 isolates (NCCB 2452 and ATCC 15692) were examined in growth media with varied iron concentrations. In a computer-controlled bioreactor cultivation system for controlled dissolved oxygen tension (pO2), a strong correlation between the exhaustion of iron and the onset of oxygen limitation was observed. The oxygen transfer rate of the culture, characterized by the volumetric oxygen transfer coefficient, kLa, significantly decreased under iron-limited conditions. The formation of alginate and capsule was more strongly affected by iron concentration than by oxygen concentration. The reduction of the oxygen transfer rate and the subsequent oxygen limitation triggered by iron deficiency may represent a new and efficient way for P. aeruginosa PAO1 to adapt to growth conditions of iron limitation. Furthermore, the secretion of proteins into the culture medium was strongly enhanced by iron limitation. The formation of the virulence factor elastase and the iron chelators pyoverdine and pyochelin also significantly increased under iron-limited conditions. These results have implications for lung infection of cystic fibrosis patients by P. aeruginosa in view of the prevalence of iron limitation at the site of infection and the respiratory failure leading to death. PMID:12949186
Micro-scale Modeling of Flow and Oxygen Transfer in Hollow Fiber Membrane Bundle
Taskin, M. Ertan; Fraser, Katharine H.; Zhang, Tao; Griffith, Bartley P.; Wu, Zhongjun J.
2010-01-01
The aim of this work was to develop a modeling approach to solve the flow and oxygen transfer when the blood passes through the hollow-fiber membrane bundle. For this purpose, a “two-region” modeling approach was developed regarding the hollow fiber and blood regions. The oxygen transfer in these regions was defined with separate diffusion processes. Two dimensional single and multi-fiber geometries were created and flow solutions were obtained for a non-Newtonian fluid. The convection-diffusion-reaction equation was solved to produce the oxygen partial pressure distributions. As a benefit of coupling the interstitial flow field into the oxygen transfer through the hollow-fiber membrane bundle, the membrane resistance was taken into consideration. Thus, varying oxygen partial pressures were observed on the outer fiber surface, which is contrary to the common simplifying assumptions of negligible membrane resistance and uniform oxygen content on the fiber surface (Traditional approach). It was illustrated that, the current approach can be utilized to predict the mass transfer efficiencies without overestimating as compared to the predictions obtained with the traditional approach. Utilization of the current approach was found to be beneficial for the geometries with lower packing density which allows significant PO2 variations on the fiber surfaces. For the geometries with dense packings, the above simplifying assumptions could be applicable. The model predictions were validated with the experimental measurements taken from a benchmark device. PMID:20802783
NASA Astrophysics Data System (ADS)
Santos, Jane Meri; Kreim, Virginie; Guillot, Jean-Michel; Reis, Neyval Costa; de Sá, Leandro Melo; Horan, Nigel John
2012-12-01
This study has investigated overall mass transfer coefficients of hydrogen sulphide from quiescent liquid surfaces under simulated laboratory conditions. Wind flow (friction velocity) has been correlated with the overall mass transfer coefficient (KL) of hydrogen sulphide in the liquid phase using a wind tunnel study. The experimental values for this coefficient have been compared with predicted KL values obtained from three different emission models that are widely used to determine volatilization rates from the quiescent surfaces of wastewater treatment unit processes. Friction velocity (in a range of 0.11 and 0.27 m s-1) was found to have a negligible influence on the overall mass transfer coefficients for hydrogen sulphide but by contrast two of the models predicted a stronger influence of friction velocity and overestimate the KL values by up to a factor of 12.5, thus risking unnecessary expenditure on odour control measures. However, at low wind speeds or friction velocities, when more odour complaints might be expected due to poor atmospheric dispersion, a better agreement of emission rates with experimental data was found for all the models.
Bhargava, Swapnil; Wenger, Kevin S; Marten, Mark R
2003-01-01
Productivity in many fungal fermentations is detrimentally affected by high broth viscosity and consequent reduced oxygen mass transfer capacity. The goal here was to determine whether pulsed feeding of limiting carbon in a fungal fermentation could lead to reduced viscosity and improved oxygen mass transfer. As a model, an industrially relevant recombinant strain of Aspergillus oryzae was grown in carbon-limited, fed-batch mode. Maltodextrin was used as a carbon source and was added either continuously or in 1.5-min pulses, 3.5 min apart. In both feeding modes the same total amount of carbon was added, and carbon feed rate was at sufficiently low levels to ensure cultures were always carbon-limited. Compared to continuous feeding, pulsed addition of substrate led to smaller fungal elements, which resulted in a significant reduction in broth viscosity. This in turn led to higher dissolved oxygen concentrations and increased oxygen uptake rates during pulsed feeding. PMID:12790687
Patnaik, Pratap R
2008-01-01
Background Although the production of poly-β-hydroxybutyrate (PHB) has many biological, energetic and environmental advantages over chemically synthesized polymers, synthetic polymers continue to be produced industrially since the productivities of fermentation processes fr PHB are not yet economically competitive. Improvement of a PHB fermentation requires good understanding and optimization under the realistic conditions of large bioreactors. Laboratory-scale studies have shown that co-cultures of Ralstonia eutropha and Lactobacillus delbrueckii generate better fermentation efficiencies than R. eutropha alone. In large bioreactors, incomplete dispersioin and perturbations in the dissolved oxygen (DO) concentration, both of which affect the fermentation, have to be considered. This study analyzes the effect of DO fluctuations on bioreactor performance for both ideal and optimally dispersed broths. Results Response coefficient analysis was employed to obtain quantitative information on the effect of DO perturbations on different variables. Three values of the Peclet number (Pe) cheracterized three levels of dispersion: Pe = 0.01 for nearly complete dispersion, Pe = 20 for optimum dispersion and Pe = 60 for insufficient dispersion. The response coefficients (RCs) of the pairs of bacterial concentrations and the main substrates, glucose and ammonium chloride, showed contrasting variations with time. Lactate, a critical intermediate, and PHB had similar RC profiles but those of lactate were one to two orders of magnitude larger than other RCs. Significantly, the optimum Pe also resulted in the largest RCs, suggesting a balance between productivity and reactor stability. Conclusion Since R. eutropha requires oxygen for its growth whereas L. delbrueckii does not, fluctuations in the DO concentartion have a strong influence on the fermentation. Apart from this, the mechanism of PHB biosynthesis indicates that control of lactate is a critical determinant of fermentation
NASA Astrophysics Data System (ADS)
Kubota, C.; Kawanami, O.; Asada, Y.; Wada, Y.; Nagayasu, T.; Shinmoto, Y.; Ohta, H.; Kabov, O.; Queeckers, P.; Chikov, S.; Straub, J.
2011-12-01
Investigation of mechanisms in nucleate boiling under microgravity conditions is essential for the development of the cooling systems handling a large amount of waste heat. A transparent heating surface with multiple arrays of 88 thin film temperature sensors and mini-heaters was developed for the clarification of boiling heat transfer mechanisms in microgravity. To investigate gravity effects on the microlayer behaviors and corresponding local heat transfer coefficients, images of liquid-vapor behaviors underneath attached bubbles and local heat transfer data were simultaneously obtained in microgravity pool boiling. The present paper reports the analysis of the data measured during the ESA parabolic flight campaign. It was found that the liquid-vapor behaviors were strongly affected by the direction and the level of residual gravity. Various patterns of liquid-vapor behaviours and corresponding enhancement or deterioration of the heat transfer are observed.
NASA Astrophysics Data System (ADS)
Kirichenko, Iu. A.; Gladchenko, G. M.; Rusanov, K. V.
1984-11-01
Heat transfer during the nucleate boiling of liquid oxygen under conditions of simulated microgravity is investigated experimentally over a wide range of pressures (600-70,000 Pa) and relative accelerations (0.01-1). The objective of the study is to verify some of the existing models for the critical region of heat transfer. Formulas are obtained yielding different acceleration dependences of the critical density of the heat flux for high and low pressures, which is consistent with experimental data on oxygen boiling.
NASA Astrophysics Data System (ADS)
Bozzoli, F.; Cattani, L.; Pagliarini, G.; Rainieri, S.
2015-03-01
This paper presents and assesses an inverse heat conduction problem (IHCP) solution procedure which was developed to determine the local convective heat transfer coefficient along the circumferential coordinate at the inner wall of a coiled pipe by applying the filtering technique approach to infrared temperature maps acquired on the outer tube's wall. The data-processing procedure filters out the unwanted noise from the raw temperature data to enable the direct calculation of its Laplacian which is embedded in the formulation of the inverse heat conduction problem. The presented technique is experimentally verified using data that were acquired in the laminar flow regime that is frequently found in coiled-tube heat-exchanger applications. The estimated convective heat transfer coefficient distributions are substantially consistent with the available numerical results in the scientific literature.
Karamavruc, A.I.; Clark, N.N.
1996-09-01
A stainless steel heat transfer tube, carrying a hot water flow, was placed in a cold bubbling fluidized bed. The tube was instrumented in the circumferential direction with five fast-responding surface thermocouples and a vertical pressure differential sensor. The local temperature and pressure data were measured simultaneously at a frequency of 120 Hz. Additionally, the local instantaneous heat transfer coefficient was evaluated by solving the transient two-dimensional heat conduction equation across the tube wall numerically. The mutual information function (MIF) has been applied to the signals to observe the relationship between points separated in time. MIF was also used to provide the most appropriate time delay constant {tau} to reconstruct an m-dimensional phase portrait of the one-dimensional time series. The distinct variation of MIF around the tube indicates the variations of solid-surface contact in the circumferential direction. The correlation coefficient was evaluated to calculate the correlation exponent {nu}, which is closely related to the fractal dimension. The correlation exponent is a measure of the strange attractor. The minimum embedding dimension as well as the degrees of freedom of the system were evaluated via the correlation coefficient. Kolmogorov entropies of the signals were approximated by using the correlation coefficient. Kolmogorov entropy considers the inherent multi-dimensional nature of chaotic data. A positive estimation of Kolmogorov entropy is an indication of the chaotic nature of the signal. The Kolmogorov entropies of the temperature data around the tube were found to be between 10 bits/s and 24 bits/s. A comparison between the signals has shown that the local instantaneous heat transfer coefficient exhibits a higher degree of chaos than the local temperature and pressure signals.
NASA Astrophysics Data System (ADS)
Mihailovic, D. T.; Alapaty, K.; Lalic, B.; Arsenic, I.; Rajkovic, B.; Malinovic, S.
2004-10-01
A method for estimating profiles of turbulent transfer coefficients inside a vegetation canopy and their use in calculating the air temperature inside tall grass canopies in land surface schemes for environmental modeling is presented. The proposed method, based on K theory, is assessed using data measured in a maize canopy. The air temperature inside the canopy is determined diagnostically by a method based on detailed consideration of 1) calculations of turbulent fluxes, 2) the shape of the wind and turbulent transfer coefficient profiles, and 3) calculation of the aerodynamic resistances inside tall grass canopies. An expression for calculating the turbulent transfer coefficient inside sparse tall grass canopies is also suggested, including modification of the corresponding equation for the wind profile inside the canopy. The proposed calculations of K-theory parameters are tested using the Land Air Parameterization Scheme (LAPS). Model outputs of air temperature inside the canopy for 8 17 July 2002 are compared with micrometeorological measurements inside a sunflower field at the Rimski Sancevi experimental site (Serbia). To demonstrate how changes in the specification of canopy density affect the simulation of air temperature inside tall grass canopies and, thus, alter the growth of PBL height, numerical experiments are performed with LAPS coupled with a one-dimensional PBL model over a sunflower field. To examine how the turbulent transfer coefficient inside tall grass canopies over a large domain represents the influence of the underlying surface on the air layer above, sensitivity tests are performed using a coupled system consisting of the NCEP Nonhydrostatic Mesoscale Model and LAPS.
Zyvoloski, George A.; Dash, Zora V.; Murphy, Hugh D.
1983-06-20
The accurate assessment of temperatures in the casing and liner is critical to the safety of EE-3 during the upcoming fracturing experiment. The purpose of this experiment is to obtain heat transfer coefficients for the nitrogen filled annulus as well as the water filled annulus below the nitrogen water interface. In addition the flowing temperature logs that were not obtained during Experiment 2026 because of an obstruction; will now be obtained in this experiment.
NASA Astrophysics Data System (ADS)
Monguzzi, A.; Tubino, R.; Salamone, M. M.; Meinardi, F.
2010-09-01
Triplet-triplet energy transfer in multicomponent organic systems is usually entirely ascribed to a Dexter-type mechanism involving only short-range donor/acceptor interactions. We demonstrate that the presence of molecular oxygen introduces a perturbation to the electronic structure of one of the involved moieties which can induce a large increase in the spin-forbidden transition oscillator strength so that the otherwise negligible Förster contribution dominates the overall energy transfer rate.
Tangwongsan, Chanchana; Chachati, Louay; Webster, John G; Farrell, Patrick V
2006-01-01
Background We need a sensor to measure the convective heat transfer coefficient during ablation of the heart or liver. Methods We built a minimally invasive instrument to measure the in vivo convective heat transfer coefficient, h in animals, using a Wheatstone-bridge circuit, similar to a hot-wire anemometer circuit. One arm is connected to a steerable catheter sensor whose tip is a 1.9 mm × 3.2 mm thin film resistive temperature detector (RTD) sensor. We used a circulation system to simulate different flow rates at 39°C for in vitro experiments using distilled water, tap water and saline. We heated the sensor approximately 5°C above the fluid temperature. We measured the power consumed by the sensor and the resistance of the sensor during the experiments and analyzed these data to determine the value of the convective heat transfer coefficient at various flow rates. Results From 0 to 5 L/min, experimental values of h in W/(m2·K) were for distilled water 5100 to 13000, for tap water 5500 to 12300, and for saline 5400 to 13600. Theoretical values were 1900 to 10700. Conclusion We believe this system is the smallest, most accurate method of minimally invasive measurement of in vivo h in animals and provides the least disturbance of flow. PMID:17067386
NASA Astrophysics Data System (ADS)
Alfandi, Ashraf; Yoon, Juhyeon; Abusaleem, Khalifeh; Albati, Mohammad; Khafaji, Salih
2015-11-01
In this study, the effect on a shell-side heat transfer coefficient is investigated using the CFD code FLUENT with a variation in longitudinal pitch to diameter ratio, SL, in the range of 1.15 to 2.6 with a fixed transverse pitch to diameter ratio. For the benchmark purposes with the available empirical correlation, typical thermal-hydraulic conditions for the Zukauskas correlation are assumed. Many sensitivity calculations for different mesh sizes and turbulent models are performed to check the accuracy of the numerical solution. A realizable κ- ɛ turbulence model was found to be in good agreement with results of the Zukauskas correlation among the other turbulence models, at least for the staggered tube bank. It was found that the average heat transfer coefficient of a crossflow over a staggered tube bank calculated using FLUENT is in good agreement with the Zukauskas correlation-calculated heat transfer coefficient in the range of 1.15 - 2.6. For a staggered tube bank, using the Zukauskas correlation seems to be valid down to SL = 1.15.
A Study of the Heat Transfer Coefficient of a Mini Channel Evaporator with R-134a as Refrigerant
NASA Astrophysics Data System (ADS)
Dollera, E. B.; Villanueva, E. P.
2015-09-01
The present study is to evaluate the heat transfer coefficient of the minichannel copper blocks used as evaporator with R-134a as the refrigerant. Experiments were conducted using three evaporator specimens of different channel hydraulic diameters (1.0mm, 2.0mm, 3.0mm). The total length for each channel is 640 mm. The dimension of each is 100mm.x50mm.x20mm. and the outside surfaces were machined to have fins. They were connected to a standard vapour compression refrigeration system. During each run of the experiment, the copper block evaporator was placed inside a small wind tunnel where controlled flow of air from a forced draft fan was introduced for the cooling process. The experimental set-up used data acquisition software and computer-aided simulation software was used to simulate the pressure drop and temperature profiles of the evaporator during the experimental run. The results were then compared with the Shah correlation. The Shah correlation over predicted and under predicted the values as compared with the experimental results for all of the three diameters and high variation for Dh=1.0mm. This indicates that the Shah correlation at small diameters is not the appropriate equation for predicting the heat transfer coefficient. The trend of the heat transfer coefficient is increasing as the size of the diameter increases.
Liu, Xiaoyu; Guo, Zhishi; Roache, Nancy F; Mocka, Corey A; Allen, Matt R; Mason, Mark A
2015-02-01
The Henry's law constant (HLC) and the overall mass transfer coefficient are both important parameters for modeling formaldehyde emissions from aqueous solutions. In this work, the apparent HLCs for formaldehyde aqueous solutions were determined in the concentration range from 0.01% to 1% (w/w) and at different temperatures (23, 40, and 55 °C) by a static headspace extraction method. The aqueous solutions tested included formaldehyde in water, formaldehyde-water with nonionic surfactant Tergitol NP-9, and formaldehyde-water with anionic surfactant sodium dodecyl sulfate. Overall, the measured HLCs ranged from 8.33 × 10(-6) to 1.12 × 10(-4) (gas-concentration/aqueous-concentration, dimensionless). Fourteen small-chamber tests were conducted with formaldehyde solutions in small pools. By applying the measured HLCs, the formaldehyde overall liquid-phase mass transfer coefficients (KOLs) were determined to be in the range of 8.12 × 10(-5) to 2.30 × 10(-4) m/h, and the overall gas-phase mass transfer coefficients were between 2.84 and 13.4 m/h. The influences of the formaldehyde concentration, temperature, agitation rate, and surfactant on HLC and KOL were investigated. This study provides useful data to support source modeling for indoor formaldehyde originating from the use of household products that contain formaldehyde-releasing biocides. PMID:25564098
NASA Astrophysics Data System (ADS)
Haddag, B.; Atlati, S.; Nouari, M.; Zenasni, M.
2015-10-01
This paper deals with the modelling and identification of the heat exchange at the tool-workpiece interface in machining. A thermomechanical modelling has been established including heat balance equations of the tool-workpiece interface which take into account the heat generated by friction and the heat transfer by conduction due to the thermal contact resistance. The interface heat balance equations involve two coefficients: heat generation coefficient (HGC) of the frictional heat and heat transfer coefficient (HTC) of the heat conduction (inverse of the thermal contact resistance coefficient). Using experimental average heat flux in the tool, estimated for several cutting speeds, an identification procedure of the HGC-HTC couple, involved in the established thermomechanical FE-based modelling of the cutting process, has been proposed, which gives the numerical heat flux equal the measured one for each cutting speed. Using identified values of the HGC-HTC couple, evolution laws are proposed for the HGC as function of cutting speed, and then as function of sliding velocity at the tool-workpiece interface. Such laws can be implemented for instance in a Finite Element code for machining simulations.
Beecher, D.T.; Fagan, T.J.
1987-06-01
The effects of air velocity, heat exchanger geometry, and fin patternation on air-side heat transfer in plate finned tube heat exchangers were investigated experimentally using a single-fin passage model. The geometric parameters considered included tube diameter, transverse tube spacing, longitudinal tube spacing, number of tube rows, and fin spacing. The effects of fin pattern depth and number of fin patterns per longitudinal tube row were investigated for a pattern consisting of corrugations of triangular cross-section transverse to the direction of airflow. The heat transfer data were correlated in terms of the dimensionless heat transfer coefficient (Nusselt number) based on the arithmetic mean temperature difference, Nu/sub a/, and the Graetz number, Gz, a dimensionless measure of the level of flow development.
Beecher, D.T.; Fagan, T.J.
1987-06-01
The effects of air velocity, heat exchanger geometry and fin pattern on air side heat transfer in plate finned tube heat exchangers were investigated experimentally using a single fin passage model. The geometric parameters considered included tube diameter, transverse tube spacing, longitudinal tube spacing, number of tube rows and fin spacing. The effects of fin pattern depth and number of fin patterns per longitudinal tube row were investigated for a pattern consisting of corrugations of triangular cross section transverse to the direction of air flow. The heat transfer data were correlated in terms of the dimensionless heat transfer coefficient (Nussult number) based on the arithmetic mean temperature difference Nu/sub a/ and the Graetz number Gz, a dimensionless measure of the level of flow development.
2013-01-01
In this study, a miniature stirred tank bioreactor was designed for treatment of waste gas containing benzene, toluene and xylene. Oxygen mass transfer characteristics for various twin and single-impeller systems were investigated for 6 configurations in a vessel with 10 cm of inner diameter and working volume of 1.77L. Three types of impellers, namely, Rushton turbine, Pitched 4blades and Pitched 2blades impellers with downward pumping have been used. Deionized water was used as a liquid phase. With respect to other independent variables such as agitation speed, aeration rate, type of sparger, number of impellers, the relative performance of these impellers was assessed by comparing the values of (KLa) as a key parameter. Based on the experimental data, empirical correlations as a function of the operational conditions have been proposed, to study the oxygen transfer rates from air bubbles generated in the bioreactor. It was shown that twin Rushton turbine configuration demonstrates superior performance (23% to 77% enhancement in KLa) compared with other impeller compositions and that sparger type has negligible effect on oxygen mass transfer rate. Agitation speeds of 400 to 800 rpm were the most efficient speeds for oxygen mass transfer in the stirred bioreactor. PMID:23369581
Karimi, Ali; Golbabaei, Farideh; Mehrnia, Momammad Reza; Neghab, Masoud; Mohammad, Kazem; Nikpey, Ahmad; Pourmand, Mohammad Reza
2013-01-01
In this study, a miniature stirred tank bioreactor was designed for treatment of waste gas containing benzene, toluene and xylene. Oxygen mass transfer characteristics for various twin and single-impeller systems were investigated for 6 configurations in a vessel with 10 cm of inner diameter and working volume of 1.77L. Three types of impellers, namely, Rushton turbine, Pitched 4blades and Pitched 2blades impellers with downward pumping have been used. Deionized water was used as a liquid phase. With respect to other independent variables such as agitation speed, aeration rate, type of sparger, number of impellers, the relative performance of these impellers was assessed by comparing the values of (KLa) as a key parameter. Based on the experimental data, empirical correlations as a function of the operational conditions have been proposed, to study the oxygen transfer rates from air bubbles generated in the bioreactor. It was shown that twin Rushton turbine configuration demonstrates superior performance (23% to 77% enhancement in KLa) compared with other impeller compositions and that sparger type has negligible effect on oxygen mass transfer rate. Agitation speeds of 400 to 800 rpm were the most efficient speeds for oxygen mass transfer in the stirred bioreactor. PMID:23369581
OXYGEN TRANSFER EFFICIENCY SURVEYS AT THE JONES ISLAND TREATMENT PLANTS - 1985-1988
Ceramic plate diffusers were among the earliest forms of fine pore diffusers used for oxygen transfer in activated sludge treatment. hey have been successfully used for over 60 years in the Jones Island West Plant of the Milwaukee Metropolitan Sewerage District and, since initial...
OXYGEN TRANSFER EFFICIENCY SURVEYS AT THE SOUTH SHORE WASTEWATER TREATMENT PLANT - 1985-1987
Ceramic plate diffusers were among the earliest forms of fine pore diffusers used for oxygen transfer in activated sludge treatment. hey have been successfully used for over 60 years in the Jones Island West Plant of the Milwaukee Metropolitan Sewerage District and, since initial...
OXYGEN TRANSFER EFFICIENCY SURVEYS AT THE JONES ISLAND TREATMENT PLANTS - 1985-1988
Ceramic plate diffusers were among the earliest forms of fine pore diffusers used for oxygen transfer in activated sludge treatment. They have been successfully used for over 60 years in the Jones Island West Plant of the Milwaukee Metropolitan Sewerage District and, since initia...
OXYGEN TRANSFER EFFICIENCY SURVEYS AT THE SOUTH SHORE WASTEWATER TREATMENT PLANT - 1985-1987
Ceramic plate diffusers were among the earliest forms of fine pore diffusers used for oxygen transfer in activated sludge treatment. They have been successfully used for over 60 years in the Jones Island West Plant of the Milwaukee Metropolitan Sewerage District and, since initi...
Two Experiments for Estimating Free Convection and Radiation Heat Transfer Coefficients
ERIC Educational Resources Information Center
Economides, Michael J.; Maloney, J. O.
1978-01-01
This article describes two simple undergraduate heat transfer experiments which may reinforce a student's understanding of free convection and radiation. Apparatus, experimental procedure, typical results, and discussion are included. (Author/BB)
Nonthermal radiative transfer of oxygen 98.9 nm ultraviolet emission: Solving an old mystery
NASA Astrophysics Data System (ADS)
Hubert, B.; Gérard, J.-C.; Shematovich, V. I.; Bisikalo, D. V.; Chakrabarti, S.; Gladstone, G. R.
2015-12-01
Sounding rocket measurements conducted in 1988 under high solar activity conditions revealed that the intensity of thermospheric OI emissions at 98.9 nm presents an anomalous vertical profile, showing exospheric intensities much higher than expected from radiative transfer model results, which included the known sources of excited oxygen. All attempts based on modeling of the photochemical processes and radiative transfer were unable to account for the higher than predicted brightnesses. More recently, the SOHO-Solar Ultraviolet Measurements of Emitted Radiation instrument measured the UV solar flux at high-spectral resolution, revealing the importance of a significant additional source of oxygen emission at 98.9 nm that had not been accounted for before. In this study, we simulate the radiative transfer of the OI-98.9 nm multiplet, including the photochemical sources of excited oxygen, the resonant scattering of solar photons, and the effects of nonthermal atoms, i.e., a population of fast-moving oxygen atoms in excess of the Maxwellian distribution. Including resonance scattering of the 98.9 nm solar multiplet, we find good agreement with the previous sounding rocket observation. The inclusion of a nonthermal oxygen population with a consistent increase of the total density produces a larger intensity at high altitude that apparently better accounts for the observation, but such a correction cannot be demonstrated given the uncertainties of the observations. A good agreement between model and sounding rocket observation is also found with the triplet at 130.4 nm. We further investigate the radiative transfer of the OI-98.9 nm multiplet and the oxygen emissions at 130.4 and 135.6 nm using observations from the STP78-1 satellite. We find a less satisfying agreement between the model and the STP78-1 data that can be accounted for by scaling the modeled intensity within a range acceptable given the uncertainties on the STP78-1 absolute calibration.
Gallis, Michail A.; Castaneda, Jaime N.; Rader, Daniel John; Torczynski, John Robert; Trott, Wayne Merle
2010-10-01
Thermal accommodation coefficients have been derived for a variety of gas-surface combinations using an experimental apparatus developed to measure the pressure dependence of the conductive heat flux between parallel plates at unequal temperature separated by a gas-filled gap. The heat flux is inferred from temperature-difference measurements across the plates in a configuration where the plate temperatures are set with two carefully controlled thermal baths. Temperature-controlled shrouds provide for environmental isolation of the opposing test plates. Since the measured temperature differences in these experiments are very small (typically 0.3 C or less over the entire pressure range), high-precision thermistors are used to acquire the requisite temperature data. High-precision components have also been utilized on the other control and measurement subsystems in this apparatus, including system pressure, gas flow rate, plate alignment, and plate positions. The apparatus also includes the capability for in situ plasma cleaning of the installed test plates. Measured heat-flux results are used in a formula based on Direct Simulation Monte Carlo (DSMC) code calculations to determine the thermal accommodation coefficients. Thermal accommodation coefficients have been determined for three different gases (argon, nitrogen, helium) in contact with various surfaces. Materials include metals and alloys such as aluminum, gold, platinum, and 304 stainless steel. A number of materials important to fabrication of Micro Electro Mechanical Systems (MEMS) devices have also been examined. For most surfaces, coefficient values are near 0.95, 0.85, and 0.45 for argon, nitrogen, and helium, respectively. Only slight differences in accommodation as a function of surface roughness have been seen. Surface contamination appears to have a more significant effect: argon plasma treatment has been observed to reduce thermal accommodation by as much as 0.10 for helium. Mixtures of argon and
NASA Astrophysics Data System (ADS)
Lewandowska, Monika; Malinowski, Leszek
2016-01-01
The data resulting from the thermal-hydraulic test of the ITER TF CICC are used to determine the flow partition and the overall effective heat transfer coefficient (hBC) between bundle and central channel in a direct way, i.e. by analysis of the heat transfer between both flow channels, based on the mass and energy balance equations and the readings of thermometers located inside the cable. In cases without a local heat source in the considered cable segment the obtained hBC values were consistent with those obtained in earlier studies by analysis of experimental data using indirect methods. It was also observed that the transverse heat transfer was strongly enhanced in a cable segment heated from outside. This phenomenon results from the mass transfer from the bundle region to the central channel. The experimental hBC data obtained for the case without a heat source in the considered segment were also compared with those calculated using various heat transfer correlations.
NASA Astrophysics Data System (ADS)
Inoue, Gen; Kawase, Motoaki
2016-09-01
It is important to reduce the oxygen diffusion resistance through PEFC porous electrode, because it is the key to reduce the PEFC cost. However, the gas diffusion coefficient of CL is lower than MPL in spite of framework consisted of same carbon blacks. In this study, in order to understand the reasons of the lower gas diffusion performance of CL, the relationship between a carbon black agglomerate structure and ionomer adhesion condition is evaluated by a numerical analysis with an actual reconstructed structure and a simulated structure. As a result, the gas diffusion property of CL strongly depends on the ionomer adhesion shape. In the case of adhesion shape with the same curvature of ionomer interface, each pore can not be connected enough. So the pore tortuosity increases. Moreover, in the case of existence of inefficient large pores formed by carbon black agglomerate and ununiformly coated ionomer, the gas diffusion performance decrease rapidly. As the measurement values in actual CL are almost equal to that with model structure with inefficient large pores. These characteristics can be confirmed by actual cross-section image obtained by FIB-SEM.
A technique for measuring the heat transfer coefficient inside a Bridgman furnace
NASA Technical Reports Server (NTRS)
Rosch, W.; Jesser, W.; Debnam, W.; Fripp, A.; Woodell, G.; Pendergrass, T. K.
1993-01-01
Knowledge of the amount of heat that is conducted, advected and radiated between an ampoule and the furnace is important for understanding vertical Bridgman crystal growth. This heat transfer depends on the temperature, emissivities and geometries of both the furnace and ampoule, as well as the choice of ambient gas inside the furnace. This paper presents a method which directly measures this heat transfer without the need to know any physical properties of the furnace, the ampoule, or the gaseous environment. Data are given for one specific furnace in which this method was used.
NASA Astrophysics Data System (ADS)
Karaś, Marcin; Zając, Daniel; Ulbrich, Roman
2014-03-01
This paper presents the results of studies in two phase gasliquid flow around tube bundle in the model of shell tube heat exchanger. Experimental investigations of heat transfer coefficient on the tubes surface were performed with the aid of electrochemical technique. Chilton-Colburn analogy between heat and mass transfer was used. Twelve nickel cathodes were mounted on the outside surface of one of the tubes. Measurement of limiting currents in the cathodic reduction of ferricyanide ions on nickel electrodes in aqueous solution of equimolar quantities of K3Fe(CN)6 and K4Fe(CN)6 in the presence of NaOH basic solution were applied to determine the mass transfer coefficient. Controlled diffusion from ions at the electrode was observed and limiting current plateau was measured. Measurements were performed with data acquisition equipment controlled by software created for this experiment. Mass transfer coefficient was calculated on the basis of the limiting current measurements. Results of mass transfer experiments (mass transfer coefficient) were recalculated to heat transfer coefficient. During the experiments, simultaneously conducted was the the investigation of two-phase flow structures around tubes with the use of digital particle image velocimetry. Average velocity fields around tubes were created with the use of a number of flow images and compared with the results of heat transfer coefficient calculations.
NASA Technical Reports Server (NTRS)
Fang, Z.; Kwong, Victor H. S.
1997-01-01
The charge transfer rate coefficient for the reaction N(2+)(2p(sup 2)P(sup 0)) + He yields products is measured by recording the time dependence of the N(2+) ions stored in an ion trap. A cylindrical radio-frequency ion trap was used to store N(2+) ions produced by laser ablation of a solid titanium nitride target. The decay of the ion signals was analyzed by single exponential least-squares fits to the data. The measured rate coefficient is 8.67(0.76) x 10(exp -11)sq cm/s. The N(2+) ions were at a mean energy of 2.7 eV while He gas was at room temperature, corresponding to an equivalent temperature of 3.9 x 10(exp 3) K. The measured value is in good agreement with a recent calculation.
NASA Astrophysics Data System (ADS)
Manapova, Aigul
2016-08-01
We consider optimal control problems for second order elliptic equations with non-self-adjoint operators-convection-diffusion problems. Control processes are described by semi-linear convection-diffusion equation with discontinuous data and solutions (states) subject to the boundary interface conditions of imperfect type (i.e., problems with a jump of the coefficients and the solution on the interface; the jump of the solution is proportional to the normal component of the flux). Controls are involved in the coefficients of diffusion and convective transfer. We prove differentiability and Lipshitz continuity of the cost functional, depending on a state of the system and a control. The calculation of the gradients uses the numerical solutions of direct problems for the state and adjoint problems.
Güneş, Hande; Çalık, Pınar
2016-07-01
Effects of oxygen transfer on recombinant protein production by Pichia pastoris under glyceraldehyde-3-phosphate dehydrogenase promoter were investigated. Recombinant glucose isomerase was chosen as the model protein. Two groups of oxygen transfer strategies were applied, one of which was based on constant oxygen transfer rate where aeration rate was Q O/V = 3 and 10 vvm, and agitation rate was N = 900 min(-1); while the other one was based on constant dissolved oxygen concentrations, C DO = 5, 10, 15, 20 and 40 % in the fermentation broth, by using predetermined exponential glucose feeding with μ o = 0.15 h(-1). The highest cell concentration was obtained as 44 g L(-1) at t = 9 h of the glucose fed-batch phase at C DO = 20 % operation while the highest volumetric and specific enzyme activities were obtained as 4440 U L(-1) and 126 U g(-1) cell, respectively at C DO = 15 % operation. Investigation of specific enzyme activities revealed that keeping C DO at 15 % was more advantageous with an expense of relatively higher by-product formation and lower specific cell growth rate. For this strategy, the highest oxygen transfer coefficient and oxygen uptake rate were K L a = 0.045 s(-1) and OUR = 8.91 mmol m(-3) s(-1), respectively. PMID:27003824
NASA Technical Reports Server (NTRS)
Powell, W. B.
1973-01-01
A methodology is described for the analysis of a transient temperature measurement made in a flat or curved plate subjected to convective heat transfer, such that the surface heat flux, the hot-gas temperture, and the gas heat transfer coefficient can be determined. It is shown that if the transient temperature measurement is made at a particular point located nearly midway in the thickness of the plate there is an important simplification in the data analysis process, in that the factor relating the surface heat flux to the measured rate of rise of temperature becomes invariant for a Fourier Number above 0.60 and for all values of the Biot Number. Parameters are derived, tabulated, and plotted which enable straightforward determination of the surface heat flux, the hot-gas temperature, of the plate, the rate of rise of temperature, the plate thickness and curvature, and the mean thermal properties of the plate material at the test temperature.
Fielitz, Peter; Borchardt, Günter
2016-08-10
In the dedicated literature the oxygen surface exchange coefficient KO and the equilibrium oxygen exchange rate [Fraktur R] are considered to be directly proportional to each other regardless of the experimental circumstances. Recent experimental observations, however, contradict the consequences of this assumption. Most surprising is the finding that the apparent activation energy of KO depends dramatically on the kinetic regime in which it has been determined, i.e. surface exchange controlled vs. mixed or diffusion controlled. This work demonstrates how the diffusion boundary condition at the gas/solid interface inevitably entails a correlation between the oxygen surface exchange coefficient KO and the oxygen self-diffusion coefficient DO in the bulk ("on top" of the correlation between KO and [Fraktur R] for the pure surface exchange regime). The model can thus quantitatively explain the range of apparent activation energies measured in the different regimes: in the surface exchange regime the apparent activation energy only contains the contribution of the equilibrium exchange rate, whereas in the mixed or in the diffusion controlled regime the contribution of the oxygen self-diffusivity has also to be taken into account, which may yield significantly higher apparent activation energies and simultaneously quantifies the correlation KO ∝ DO(1/2) observed for a large number of oxides in the mixed or diffusion controlled regime, respectively. PMID:27460608
Heat and mass transfer of submerged helium injection in liquid oxygen vessel
NASA Astrophysics Data System (ADS)
Jung, Youngsuk; Cho, Namkyung; Baek, Seungwhan; Jeong, Sangkwon
2014-11-01
The submerged helium injection process results in the heat and mass transfer between the helium bubble and the cryogenic liquid. The objective of this paper is to analyze the dynamics of the heat and mass transfer process. It is observed that during the helium injection process the dynamics of mass transfer is dominant and the transient heat transfer is negligible. The helium bubble shape and rising patterns are observed with a visualization device that helps to discern the dominant process between heat transfer and mass transfer. The clustering patterns such as coalescence of helium bubbles are observed with the visualization device. The visualization results indicate that, it is very difficult to determine the representative size of bubbles due to the irregular shape of the helium bubbles. The shape and size of the helium bubbles are important parameters for evaluating the overall mass transfer coefficient (kGA) which is the essential parameter for calculating the evaporation rate of the bulk liquid into the helium bubbles. In this paper, the simplified lumped model is considered to fairly approximate the evaporation rate of the cryogenic liquid into the bubbles and the cooling rate of helium injection. The empirical correlation for the average concentration (C‾A) of evaporated cryogenic liquid into the helium bubbles is presented and the overall mass transfer coefficients (kGA) are calculated as the result of the lumped model. The proposed model and empirical correlations are compared with the experimental results, and the comparison result shows good agreement with differences that are less than ±0.4 K.
The effect of the liquid-solid system properties on the interline heat transfer coefficient
NASA Technical Reports Server (NTRS)
Wayner, P. C., Jr.
1977-01-01
A theoretical procedure to determine the heat transfer characteristics of the interline region of an evaporating meniscus using the macroscopic optical and thermophysical properties of the system is outlined. The analysis is based on the premise that the interline transport processes are controlled by the London-van der Waals forces between condensed phases (solid and liquid). The procedure is used to compare the relative size of the interline heat sink of various systems using a constant heat flux model. This solution demonstrates the importance of the interline heat flow number which is evaluated for various systems. The heat transfer characteristics of the decane-steel system are numerically compared with those of the carbon tetrachloride-quartz system.
Triplet-triplet energy transfer and protection mechanisms against singlet oxygen in photosynthesis
NASA Astrophysics Data System (ADS)
Kihara, Shigeharu
individual BChl pigments within that photosynthetic antenna complex are accessed via their triplet state dynamics. It is found that the currently used exciton model of FMO needs to be revised. It is also shown that triplet excited states can be readily transferred between the molecules. It is proposed that the triplet energy transfer between the BChl molecules can also serve as a protection mechanism. Finally, it is inferred that at least one of the BChl molecules within the FMO has a triplet state energy that is lower than that of singlet oxygen. This effectively prevents the formation of singlet oxygen and protects the complex from oxidative damage. The energy of BChl is apparently lowered by the specific protein environment, as in solution its energy is measured to be somewhat higher than the energy of singlet oxygen. Finally, the results of the triplet energy transfer within the cytochrome b6f complex are presented. This part of the work is not conclusive, and some of the problems encountered in experiments are described, as well as a new method of sample degassing developed for this type of study is presented.
Ju, L K; Ho, C S; Shanahan, J F
1991-12-01
Fermentations of Penicillium chrysogenum have been made with different CO(2) contents in the influent gas streams. The rheological behavior of the culture broth was found to be significantly changed by exposure to high levels of CO(2). This is attributed to the wide variation in the morphology of P. chrysogenum, from normal mycelia with long hyphae to roughly spherical pellets when subjected to high levels of CO(2). A correlation has been developed relating volumetric O(2) transfer coefficients, k(L)a, with the effective O(2) diffusion coefficients, D(e), and the apparent viscosities, micro(app), based on the results obtained in this study. The use of CO(2) as a potent means for altering the rheological properties of culture broths and consequently improving the O(2) transfer capabilities in penicillin fermentations was clearly demonstrated. PMID:18600719
Performance and heat transfer characteristics of a carbon monoxide/oxygen rocket engine
NASA Technical Reports Server (NTRS)
Linne, Diane L.
1993-01-01
The combustion and heat transfer characteristics of a carbon monoxide and oxygen rocket engine were evaluated. The test hardware consisted of a calorimeter combustion chamber with a heat sink nozzle and an eighteen element concentric tube injector. Experimental results are given at chamber pressures of 1070 and 3070 kPa, and over a mixture ratio range of 0.3 to 1.0. Experimental C efficiency was between 95 and 96.5 percent. Heat transfer results are discussed both as a function of mixture ratio and axial distance in the chamber. They are also compared to a Nusselt number correlation for fully developed turbulent flow.
Pressure-induced absorption coefficients for radiative transfer calculations in Titan's atmosphere
NASA Technical Reports Server (NTRS)
Courtin, Regis
1988-01-01
The semiempirical theory of Birnbaum and Cohen (1976) is used to calculate the FIR pressure-induced absorption (PIA) spectra of N2, CH4, N2 + Ar, N2 + CH4, and N2 + H2 under conditions like those in the Titan troposphere. The results are presented graphically and compared with published data from laboratory measurements of PIA in the same gases and mixtures (Dagg et al., 1986; Dore et al., 1986). Good agreement is obtained, with only a slight underestimation of PIA at 300-400/cm in the case of CH4. The absorption coefficients are presented in tables, and it is suggested that the present findings are of value for evaluating the effects of tropospheric clouds on the Titan FIR spectrum and studying the greenhouse effect near the Titan surface.
Bennion, Kevin; Moreno, Gilberto
2015-09-29
Thermal management for electric machines (motors/ generators) is important as the automotive industry continues to transition to more electrically dominant vehicle propulsion systems. Cooling of the electric machine(s) in some electric vehicle traction drive applications is accomplished by impinging automatic transmission fluid (ATF) jets onto the machine's copper windings. In this study, we provide the results of experiments characterizing the thermal performance of ATF jets on surfaces representative of windings, using Ford's Mercon LV ATF. Experiments were carried out at various ATF temperatures and jet velocities to quantify the influence of these parameters on heat transfer coefficients. Fluid temperatures were varied from 50 degrees C to 90 degrees C to encompass potential operating temperatures within an automotive transaxle environment. The jet nozzle velocities were varied from 0.5 to 10 m/s. The experimental ATF heat transfer coefficient results provided in this report are a useful resource for understanding factors that influence the performance of ATF-based cooling systems for electric machines.
NASA Astrophysics Data System (ADS)
Zajaczkowski, Bartosz; Halon, Tomasz; Krolicki, Zbigniew
2016-02-01
In this paper we study the influence of sub-atmospheric pressure on nucleate boiling. Sixteen correlations for pool boiling available in literature are gathered and evaluated. Analysis is performed in the pressure range 1-10 kPa and for heat flux densities 10-45 kW/m2. Superheats are set between 6.2 and 28.7 K. The results of calculations were compared with experimental values for the same parameters. The experiments were conducted using isolated glass cylinder and water boiling above the copper plate. Results show that low pressure adjust the character of boiling curve—the curve flattened and the natural convection region of boiling is shifted towards higher wall temperature superheats due to the influence of low pressure on the bubble creation and process of its departure. In result, 8 of 16 analyzed correlations were determined as completely invalid in subatmospheric conditions and the remaining set of equations was compared to experimental results. Experimentally obtained values of heat transfer coefficients are between 1 and 2 kW/m2K. With mean absolute deviation (MAD) we have found that the most accurate approximation of heat transfer coefficient is obtained using Mostinski reduced pressure correlation (0.13-0.35 MAD) and Labuntsov correlation (0.12-0.89 MAD).
Johnson, J.E.; Ward, G.M.; Ennis, M.E. Jr.; Boamah, K.N.
1988-02-01
The diet-milk transfer coefficient, Fm (Bq L-1 output in milk divided by Bq d-1 intake to the animal) was studied for eight radionuclides that previously had been given little attention. The Fm values for cows and goats, respectively, were: 2.3 x 10(-5) and 1.5 x 10(-4) for /sup 99m/Tc, 1.4 x 10(-4) and 8.5 x 10(-4) for /sup 95m/Tc, 1.1 x 10(-2) for /sup 99/Tc (goats only); 1.7 x 10(-3) and 9 x 10(-3) for /sup 99/Mo; 4.8 x 10(-4) and 4.4 x 10(-3) for /sup 123m/Te; 4.8 x 10(-4) and 4.6 x 10(-3) for /sup 133/Ba; 5.5 x 10(-7) and 5.5 x 10(-6) for /sup 95/Zr; and 4.1 x 10(-7) and 6.4 x 10(-6) for /sup 95/Nb. The goat/cow transfer coefficient ratios for milk were approximately 10, but the goat/cow ratios for meat varied by three orders of magnitude.
NASA Technical Reports Server (NTRS)
Heath, D. Michele; Winfree, William P.; Carraway, Debra L.; Heyman, Joseph S.
1987-01-01
An infrared measurement system is used that consists of a laser heating source, an infrared camera for data acquisition, and a video recorder for data storage. A laser beam is scanned over an airfoil, heating its surface to a few degrees above ambient. An infrared camera then measures the temperature of the airfoil over a two-dimensional field, and these temperatures are stored as a function of time on a video recorder. The resulting temperature pictures are digitized and an iterative approximation algorithm is used to extract the heat transfer coefficient. The resulting values are normalized to the natural convection condition. The technique has been applied in low-speed wind tunnel tests and compared to well-established hot-film measurements which were made simultaneously to confirm the flow conditions. Heat transfer coefficients were determined using a linear scanning pattern, to indicate the position of natural and of artificially induced transition on an airfoil, at various wind speeds. The technique is shown to be sensitive to transition at low Mach numbers. The advantages of the technique are discussed.
Hodge, S.A.
1980-08-01
The friction factor and Stanton number for flow past a roughened surface are determined by the parameters A and R(h/sup +/) of the universal law of friction and A/sub H/ and G(h/sup +/) of the universal law of heat transfer. The methods to be used for determination of these parameters for the particular roughness to be used in the Core Flow Test Loop (CFTL) are presented. Examples are given concerning the application of these methods to both transitional and fully rough flow using experimental results taken from the literature.
Using eddy covariance to estimate air–sea gas transfer velocity for oxygen
NASA Astrophysics Data System (ADS)
Andersson, Andreas; Rutgersson, Anna; Sahlée, Erik
2016-07-01
Air-sea gas transfer velocity for O2 is calculated using directly measured fluxes with the eddy covariance technique. It is a direct method and is frequently used to determine fluxes of heat, humidity, and CO2, but has not previously been used to estimate transfer velocities for O2, using atmospheric eddy covariance data. The measured O2 fluxes are upward directed, in agreement with the measured air-sea gradient of the O2 concentration, and opposite to the direction of the simultaneously measured CO2 fluxes. The transfer velocities estimated from measurements are compared with prominent wind speed parameterizations of the transfer velocity for CO2 and O2, previously established from various measurement techniques. Our result indicates stronger wind speed dependence for the transfer velocity of O2 compared to CO2 starting at intermediate wind speeds. This stronger wind speed dependence appears to coincide with the onset of whitecap formation in the flux footprint and the strong curvature of a cubic wind-dependent function for the transfer velocity provides the best fit to the data. Additional data using the measured O2 flux and an indirect method (based on the Photosynthetic Quotient) to estimate oxygen concentration in water, support the stronger wind dependence for the transfer velocity of O2 compared to CO2.
NASA Technical Reports Server (NTRS)
Ibrahim, Mounir; Kannapareddy, Mohan; Tew, Roy C.; Dudenhoefer, James E.
1991-01-01
Twelve different cases of multidimensional models of Stirling engine components for space applications have been numerically investigated for oscillating, incompressible laminar flow with heat transfer. The cases studied covered wide ranges of Valensi number (from 44 to 700), Re(max) number (from 8250 to 60,000), and relative amplitude of fluid motion of 0.686 and 1.32. The Nusselt numbers obtained from the present study indicate a very complex shape with respect to time and axial location in the channel. The results indicate that three parameters can be used to define the local Nusselt number variation, namely: time average, amplitude, and phase angle. These parameters could be correlated respectively using: Re(max), Va and Re(max), and the relative amplitude of fluid motion.
Measurements of absorbed heat flux and water-side heat transfer coefficient in water wall tubes
NASA Astrophysics Data System (ADS)
Taler, Jan; Taler, Dawid; Kowal, Andrzej
2011-04-01
The tubular type instrument (flux tube) was developed to identify boundary conditions in water wall tubes of steam boilers. The meter is constructed from a short length of eccentric tube containing four thermocouples on the fire side below the inner and outer surfaces of the tube. The fifth thermocouple is located at the rear of the tube on the casing side of the water-wall tube. The boundary conditions on the outer and inner surfaces of the water flux-tube are determined based on temperature measurements at the interior locations. Four K-type sheathed thermocouples of 1 mm in diameter, are inserted into holes, which are parallel to the tube axis. The non-linear least squares problem is solved numerically using the Levenberg-Marquardt method. The heat transfer conditions in adjacent boiler tubes have no impact on the temperature distribution in the flux tubes.
Drag and Bulk Transfer Coefficients Over Water Surfaces in Light Winds
NASA Astrophysics Data System (ADS)
Wei, Zhongwang; Miyano, Aiko; Sugita, Michiaki
2016-04-01
The drag coefficient (CD) , experimentally determined from observed wind speed and surface stress, has been reported to increase in the low wind-speed range (< 3 m s^{-1} ) as wind speed becomes smaller. However, until now, the exact causes for its occurrence have not been determined. Here, possible causes for increased CD values in near-calm conditions are examined using high quality datasets selected from three-year continuous measurements obtained from the centre of Lake Kasumigaura, the second largest lake in Japan. Based on our analysis, suggested causes including (i) measurement errors, (ii) lake currents, (iii) capillary waves, (iv) the possibility of a measurement height within the interfacial/transition sublayer, and (v) a possible mismatch in the representative time scale used for mean and covariance averaging, are not considered major factors. The use of vector-averaged, instead of scalar-averaged, wind speeds and the presence of waves only partially explain the increase in CD under light winds. A small increase in turbulent kinetic energy due to buoyant production at low wind speeds is identified as the likely major cause for this increase in CD in the unstable atmosphere dominant over inland water surfaces.
Drag and Bulk Transfer Coefficients Over Water Surfaces in Light Winds
NASA Astrophysics Data System (ADS)
Wei, Zhongwang; Miyano, Aiko; Sugita, Michiaki
2016-08-01
The drag coefficient (CD), experimentally determined from observed wind speed and surface stress, has been reported to increase in the low wind-speed range (<3 m s^{-1}) as wind speed becomes smaller. However, until now, the exact causes for its occurrence have not been determined. Here, possible causes for increased CD values in near-calm conditions are examined using high quality datasets selected from three-year continuous measurements obtained from the centre of Lake Kasumigaura, the second largest lake in Japan. Based on our analysis, suggested causes including (i) measurement errors, (ii) lake currents, (iii) capillary waves, (iv) the possibility of a measurement height within the interfacial/transition sublayer, and (v) a possible mismatch in the representative time scale used for mean and covariance averaging, are not considered major factors. The use of vector-averaged, instead of scalar-averaged, wind speeds and the presence of waves only partially explain the increase in CD under light winds. A small increase in turbulent kinetic energy due to buoyant production at low wind speeds is identified as the likely major cause for this increase in CD in the unstable atmosphere dominant over inland water surfaces.
Nemykin, Victor N.; Laskin, Julia; Basu, Partha
2004-07-19
Redox reactions coupled with the formal loss or gain of an oxygen atom are ubiquitous in chemical processes. Such reactions proceed through the reduction of the donor center (XO) and the oxidation of the acceptor (Y) molecule. Among many examples of the metal centered oxygen atom transfer (OAT) reactivity, those involving molybdenum complexes have been widely investigated due to their involvement in mononuclear molybdenum enzymes. The heat of reaction of the overall atom transfer process can be expressed as a difference between the bond dissociation energies (BDEs) of the oxygen-donor(X) and oxygen-acceptor(Y) bond, i.e., H=DX=o-DY=O.
Han, Xianhong; Hao, Xin; Yang, Kun; Zhong, Yaoyao
2013-12-16
Heat transfer is a crucial aspect for hot stamping process, the fully austenitized boron steel blank with temperature about 900°C is transferred to the tool, then formed rapidly and quenched in the cooled tool. The desired fully martensitic transformation will happen only if the cooling rate exceeds a critical value approximately 27 K/s. During such process, the heat transfer coefficient (abbreviated as HTC) between the tool and blank plays a decisive role for the variation of the blank temperature. In this work, a theoretical formula based on the joint-roughness model is presented to describe the law of HTC, which relies on the roughness, hardness, and other material parameters of the tool and blank. Moreover, a non-contact temperature measuring system based on the infrared thermal camera is built to catch the temperature change course, and then the HTC value is derived through the inverse analysis. Based on the theoretical and experimental results, the change rule of HTC especially its dependence on the process pressure will be discussed in detail.
Gillespie, D.R.H.; Wang, Z.; Ireland, P.T.; Kohler, S.T.
1998-01-01
Cast impingement cooling geometries offer the gas turbine designer higher structural integrity and improved convective cooling when compared to traditional impingement cooling systems, which rely on plate inserts. In this paper, it is shown that the surface that forms the jets contributes significantly to the total cooling. Local heat transfer coefficient distributions have been measured in a model of an engine wall cooling geometry using the transient heat transfer technique. The method employs temperature-sensitive liquid crystals to measure the surface temperature of large-scale perspex models during transient experiments. Full distributions of local Nusselt number on both surfaces of the impingement plate, and on the impingement target plate, are presented at engine representative Reynolds numbers. The relative effects of the impingement plate thermal boundary condition and the coolant supply temperature on the target plate heat transfer have been determined by maintaining an isothermal boundary condition at the impingement plate during the transient tests. The results are discussed in terms of the interpreted flow field.
Tyroller, Lina; Rousseau, Diederik P L; Santa, Santa; García, Joan
2010-07-01
The oxygen transfer rate (OTR) has a significant impact on the design, optimal operation and modelling of constructed wetlands treating wastewater. Oxygen consumption is very fast in wetlands and the OTR cannot be determined using an oxygen mass balance. This problem is circumvented in this study by applying the gas tracer method. Experiments were conducted in an unplanted gravel bed (dimensions L x W x d 125 x 50 x 35 cm filled with a 30-cm layer of 10-11-mm gravel) and a planted horizontal subsurface flow constructed wetland (HSSFCW) (L x W x d 110 x 70 x 38 cm filled with a 30-cm layer of 3.5-mm gravel with Phragmites australis). Tap water saturated with propane as gas tracer (pure or commercial cooking gas, depending on the test) was used. The mass transfer ratio between oxygen and commercial propane gas was quite constant and averaged R = 1.03, which is slightly lower than the value of R = 1.39 that is usually reported for pure propane. The OTR ranged from 0.31 to 5.04 g O(2) m(-2) d(-1) in the unplanted gravel bed and from 0.3 to 3.2 g O(2) m(-2) d(-1) in the HSSFCW, depending on the hydraulic retention time (HRT). The results of this study suggest that the OTR in HSSFCW is very low for the oxygen demand of standard wastewater and the OTR calculations based on mass balances and theoretical stoichiometric considerations overestimate OTR values by a factor that ranges from 10 to 100. The gas tracer method is a promising tool for determining OTR in constructed wetlands, with commercial gas proving to be a viable low-cost alternative for determining OTR. PMID:20542312
NASA Technical Reports Server (NTRS)
Hippensteele, Steven A.; Poinsatte, Philip E.
1993-01-01
In this transient technique the preheated isothermal model wall simulates the classic one-dimensional, semi-infinite wall heat transfer conduction problem. By knowing the temperature of the air flowing through the model, the initial temperature of the model wall, and the surface cooling rate measured at any location with time (using the fast-response liquid-crystal patterns recorded on video tape), the heat transfer coefficient can be calculated for the color isothermal pattern produced. Although the test was run transiently, the heat transfer coefficients are for the steady-state case. The upstream thermal boundary condition was considered to be isothermal. This transient liquid-crystal heat-transfer technique was used in a transient air tunnel in which a square-inlet, 3-to-1 exit transition duct was placed. The duct was preheated prior to allowing room temperature air to be suddenly drawn through it. The resulting isothermal contours on the duct surfaces were revealed using a surface coating of thermochromic liquid crystals that display distinctive colors at particular temperatures. A video record was made of the temperature and time data for all points on the duct surfaces during each test. The duct surfaces were uniformly heated using two heating systems: the first was an automatic temperature-controlled heater blanket completely surrounding the test duct like an oven, and the second was an internal hot-air loop through the inside of the test duct. The hot-air loop path was confined inside the test duct by insulated heat dams located at the inlet and exit ends of the test duct. A recirculating fan moved hot air into the duct inlet, through the duct, out of the duct exit, through the oven, and back to the duct inlet. The temperature nonuniformity of the test duct model wall was held very small. Test results are reported for two inlet Reynolds numbers of 200,000 and 1,150,000 (based on the square-inlet hydraulic diameter) and two free-stream turbulence
NASA Astrophysics Data System (ADS)
Hippensteele, Steven A.; Poinsatte, Philip E.
1993-08-01
In this transient technique the preheated isothermal model wall simulates the classic one-dimensional, semi-infinite wall heat transfer conduction problem. By knowing the temperature of the air flowing through the model, the initial temperature of the model wall, and the surface cooling rate measured at any location with time (using the fast-response liquid-crystal patterns recorded on video tape), the heat transfer coefficient can be calculated for the color isothermal pattern produced. Although the test was run transiently, the heat transfer coefficients are for the steady-state case. The upstream thermal boundary condition was considered to be isothermal. This transient liquid-crystal heat-transfer technique was used in a transient air tunnel in which a square-inlet, 3-to-1 exit transition duct was placed. The duct was preheated prior to allowing room temperature air to be suddenly drawn through it. The resulting isothermal contours on the duct surfaces were revealed using a surface coating of thermochromic liquid crystals that display distinctive colors at particular temperatures. A video record was made of the temperature and time data for all points on the duct surfaces during each test. The duct surfaces were uniformly heated using two heating systems: the first was an automatic temperature-controlled heater blanket completely surrounding the test duct like an oven, and the second was an internal hot-air loop through the inside of the test duct. The hot-air loop path was confined inside the test duct by insulated heat dams located at the inlet and exit ends of the test duct. A recirculating fan moved hot air into the duct inlet, through the duct, out of the duct exit, through the oven, and back to the duct inlet. The temperature nonuniformity of the test duct model wall was held very small. Test results are reported for two inlet Reynolds numbers of 200,000 and 1,150,000 (based on the square-inlet hydraulic diameter) and two free-stream turbulence
NASA Astrophysics Data System (ADS)
Rajaraman, R.; Velraj, R.
2008-07-01
The interfacial heat transfer coefficient (IHTC) is necessary for accurate simulation of the casting process. In this study, a cylindrical geometry is selected for the determination of the IHTC between aluminum alloy casting and the surrounding sand mold. The mold surface heat flux and temperature are estimated by two inverse heat conduction techniques, namely Beck’s algorithm and control volume technique. The instantaneous cast and mold temperatures are measured experimentally and these values are used in the theoretical investigations. In the control volume technique, partial differential heat conduction equation is reduced to ordinary differential equations in time, which are then solved sequentially. In Beck’s method, solution algorithm is developed under the function specification method to solve the inverse heat conduction equations. The IHTC was determined from the surface heat flux and the mold surface temperature by both the techniques and the results are compared.