bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical Prediction of Local Temperature and Current Density in a PEM Fuel Cell
Authors: Shimpalee S. , Dutta S. , Van Zee J. W. 
Published: November 2021

Abstract
The heat generation inside polymer electrolyte membrane (PEM) fuel cells affects fuel cell performance significantly. A numerical model for three-dimensional single fuel cell is developed by including the energy equation and the phase change aspects. A control volume approach is used and source terms for species transport equations, heat generation, and phase change model are introduced to incorporate the coupled flow physics in commercial flow solvers. Details of local current density distribution and temperature profiles are obtained and predictions from this model are compared with previous conclusions. The results reveal that the water evaporation and condensation generated by temperature change in fuel cell control humidity of the membrane and vary the local current density value. Further, the temperature distributions are dependent on the amount of heat generation created by electrical losses and water phase change. The predictions also present that the performance of the fuel cell relies not only on the inlet humidity condition but also on the temperature change inside the fuel cell.
3-D Model of Proton Exchange Membrane Fuel Cells
Authors: Zhou Tianhong , Liu Hongtan 
Published: November 2021

Abstract
A comprehensive three-dimensional model for a proton exchanger membrane (PEM) fuel cell is developed to evaluate the effects of various design and operating parameters on fuel cell performance. The geometrical model includes two distinct flow channels separated by the membrane and electrode assembly (MEA). This model is developed by coupling the governing equations for reactant mass transport and chemical reaction kinetics. To facilitate the numerical solution, the full PEM fuel cell was divided into three coupled domains according to the flow characteristics. The 3-D model has been applied to study species transport, heat transfer, and current density distributions within a fuel cell. The predicated polarization behavior is shown to compare well with experimental data from the literature. The modeling results demonstrate good potential for this computational model to be used in operation simulation as well as design optimization.
A Pseudo-Homogeneous Model for Cathode Catalyst Layer of PEM Fuel Cells
Authors: You Lixin , Liu Hongtan 
Published: November 2021

Abstract
A pseudo-homogeneous model for cathode catalyst layer performance in PEM fuel cells is derived from a basic mass-current balance by the control volume approach. The model considers kinetics of oxygen reduction at the catalyst/electrolyte interface, proton transport through the polymer electrolyte and oxygen diffusion through porous voids. A relaxation method is developed to solve the governing equations, which belong to the two-point boundary problem. The numerical results are compared well with our experimental data. The influences of various parameters such as overpotential, proton conductivity, catalyst layer porosity, and catalyst surface area on the performance of catalyst layer are quantitatively studied. The model can be used to determine important catalyst layer design parameters for different working conditions. From the discussions in this paper, it is possible to design high performance, low cost cathode catalyst layer, and hence, to improve PEM fuel cell performances.
A Passive Portable Water Pasteurization System for Developing Countries: Design, Analysis and Proof-of-Concept Experiments
Authors: Anderson Christianne V. D. R. , Kulacki Francis A. 
Published: November 2021

Abstract
The design, simulation, and testing of a novel portable pasteurization system suitable for the daily needs of four individuals are presented. This is the first self-powered, large-scale portable system developed to kill waterborne pathogens that contaminate current water supplies worldwide. The major components of the system consist of available technology: two evacuated solar collectors, a heat exchanger, two holding tanks, and a thermostatic valve. Flow of contaminated water through these components is permitted only when the temperature specified by the thermostatic valve is reached. Simulation of system performance is obtained via a lumped capacitance, time-dependent analysis with a limited number of input parameters. A prototype pasteurizer was designed and constructed, and proof-of-concept experiments were conducted in Minnesota in May 1998. The system was able to deliver nearly the predicted quantity of pasteurized water, approximately 70 liter/day.
Two Dimensional Simulations of Enhanced Heat Transfer in an Intermittently Grooved Channel
Authors: Greiner M. , Fischer P. F. , Tufo H. M. 
Published: November 2021

Abstract
Two-dimensional Navier-Stokes simulations of heat and momentum transport in an intermittently grooved passage are performed using the spectral element technique for the Reynolds number range 600 ≤ Re ≤ 1800. The computational domain has seven contiguous transverse grooves cut symmetrically into opposite walls, followed by a flat section with the same length. Periodic inflow/outflow boundary conditions are employed. The development and decay of unsteady flow is observed in the grooved and flat sections, respectively. The axial variation of the unsteady component of velocity is compared to the local heat transfer, shear stress and pressure gradient. The results suggest that intermittently grooved passages may offer even higher heat transfer for a given pumping power than the levels observed in fully grooved passages.
On the Optimal Configuration of Three Cylinders in a Row Cooled by a Slot Jet of Air
Authors: Gori F. , Bossi L. 
Published: November 2021

Abstract
The optimal positions of three circular cylinders, cooled by a slot jet of air, are investigated. The diameters of the three cylinders are the same, D = 10 mm, while the slot jet has an height of S = 5 mm. The first cylinder is set up at a distance, H, from the slot exit, H/S = 6, which is the optimum in a one cylinder configuration. The second cylinder is set up at a distance from the first one, L1, with L1/S = 4, which is the optimum when two cylinders are present. The optimal distance of the third cylinder from the second one is L2, such that L2/S = 4, and the mean heat transfer coefficient on the third cylinder is at the maximum value. Local heat transfer coefficients on the surface of the third cylinder varies with L2/S. Measurements of axial velocity and turbulence intensity, in the axial direction, accompany the heat transfer results.
Free Convective Flow in a Two Enclosure Arrangement With a High Aspect Ratio Side Enclosure Joined to a Large Square Enclosure
Authors: Oosthuizen Patrick H. 
Published: November 2021

Abstract
A numerical study of free convective flow in a vertical joined two-enclosure arrangement has been undertaken. In this arrangement, a vertical heated wall kept at a uniform high temperature is contained in a high aspect ratio rectangular side enclosure. This enclosure is separated from a larger square enclosure by a vertical dividing wall which is impermeable but offers no resistance to heat transfer. The vertical wall of the main flow enclosure opposite to the dividing wall is maintained at a uniform lower temperature. All remaining walls in both enclosures are adiabatic. The situation considered is an approximate model of a window exposed to a hot outside environment and covered by a plane blind which in turn is exposed to cooled room. The flow has been assumed to be laminar and two-dimensional and results have been obtained for a Prandtl number of 0.7. The effects of Rayleigh number and the dimensionless width of the side enclosure on the Nusselt number have been investigated. The results show that there is a minimum in the Nusselt number variation with side enclosure width for a fixed Rayleigh number. The effect of Rayleigh number on the conditions under which this minimum occurs and on the value of the minimum Nusselt number has been investigated.
Numerical Modeling of Radiative and Convective Heat Transfer From an Irradiated Complex Window Assembly
Authors: Collins M. , Harrison S. J. , Oosthuizen P. H. , Naylor D. 
Published: November 2021

Abstract
The present numerical study examines the influence of heated, horizontal, and rotateable louvers on the convective and radiative heat transfer from a hot or cold vertical isothermal surface. The system models absorption of solar energy in a Venetian blind adjacent to the indoor surface of a window. Building on previous analyses, a steady, laminar, two-dimensional, conjugate conduction / convection / radiation model of this problem has been developed, and solutions have been obtained using the finite element method. Validation of the model against existing solutions has been undertaken. Results were obtained for two window temperatures (warm and cool compared to ambient), two louver to plate spacings, and three louver angles.
The results clearly demonstrate the effect of the model variables on heat transfer from the plate surface. With few exceptions, steady periodicity along the plate was clearly demonstrated. More importantly, increased independence of the results from the louver angle as louver to plate distance increased was demonstrated.
Mechanically Optimized Orientation of Intracellular Stress Fibers Under Cyclic Stretch
Authors: Yamada Hiroshi , Takemasa Tohru , Yamaguchi Takami 
Published: November 2021

Abstract
To elucidate the orientation of stress fibers in a cultured endothelial cell under cyclic stretch, we hypothesized that a stress fiber aligns so as to minimize the summation of its length change under cyclic stretch, and that there is a limit in the sensitivity of cellular response to the mechanical stimulus. Results from numerical simulations based on the continuum mechanics describe the experimental observations under uniaxial stretch well. They give us an insight to the biological phenomenon of the orientation in stress fibers under biaxial stretch from the viewpoint of mechanical engineering.
Determination of Flow and Heat-Transfer Parameters in Porous Media With Consideration of Density Variation of Working Fluid
Authors: Hsieh W. H. , Wu W. T. 
Published: November 2021

Abstract
An experimental investigation is conducted to determine the flow and heat-transfer parameters of porous media with the consideration of density-variation effect of the working fluid. The permeability (K), inertial coefficient (F), and local convective heat transfer coefficient (hloc) are determined for two types of metal screens at Reynolds numbers ranging from 20 to 400. A single-blow transient technique combined with a compressible non-local-thermal-equilibrium model determines the hloc. The compressible non-local-thermal-equilibrium model is also adopted in a Levenberg-Marquardt optimization technique for deducing the K and F from measured steady-state pressure drops at different flow rates. Results show that the permeability increases with the increase of the porosity. A set of empirical correlations is obtained for calculating the Nusselt number. Results also show that, under the test condition of this study, consideration of the density-variation effect would improve the accuracy in deducing the K, F, and hloc.
A Parametric Study of Phonon Energy Transport in Semiconductor Devices
Authors: Walker D. Greg , Fisher Tim S. , Ralston-Good Jeremy , Schrimpf Ron D. 
Published: November 2021

Abstract
Microscale energy transport typically can not be described by traditional continuum models. This is especially true for semiconductor devices where length and time scales are continually becoming smaller. These conditions tend to place the physics of the energy transport into the non-equilibrium regime. Moments of the Boltzmann equations which describe average quantities of particle physics can be used under these conditions to obtain solutions to the transport problem. Most simulations, using this approach neglect non-equilibrium energy transport through phonon interactions. The goal of this work is to identify parameters crucial to non-equilibrium energy transport in semiconductor devices specifically where phonon interactions are concerned through a systematic variation of parameters. A Gallium Arsenide device that has been examined in previous research will be used as a benchmark for comparisons.
Effects of the Manufacturing Process on the Dimensional Accuracy of Thermoset Composites
Authors: Zhu Qi , Geubelle Philippe H. 
Published: November 2021

Abstract
The warpage of thermoset composite structures during the manufacturing process is a direct consequence of residual stress development. The capability to predict residual stresses is crucial to the manufacture of dimensionally accurate composite structures. This paper is focused on understanding the fundamental issues leading to residual stresses in thermoset polymer composites and their effect on the dimensional accuracy of the manufactured components. Special emphasis is placed on the simulation of autoclave curing and hot pressing. A three-dimensional coupled thermo-chemo-viscoelastic model is developed to simulate the heat transfer, curing, residual stresses and deformation of a composite part during the entire cure cycle. The predicted values of curvature for cross-ply graphite-epoxy laminates agree well with experimental observations. The numerical result indicates that a significant fraction of the residual stress develops before cooldown. Detailed studies are also performed to examine the springforward phenomenon in L-shaped composite parts. The finite element results show that mold design (male vs. female mold), mold thermal expansion, and part thickness all play an important role on the final shape of the parts.
A New Facility for Measurements of Three-Dimensional, Local Subcooled Flow Boiling Heat Flux and Related Critical Heat Flux
Authors: Boyd Ronald D. , Cofie Penrose , Li Qing-Yuan , Ekhlassi Ali 
Published: November 2021

Abstract
In the development of plasma-facing components (PFC) for fusion reactors and high heat flux heat sinks (or components) for electronic applications, the components are usually subjected to a peripherally non-uniform heat flux. Even if the applied heat flux is uniform in the axial direction [which is unlikely], both intuition and recent investigations have clearly shown that both the local heat flux and the eventual critical heat flux (CHF) in this three-dimensional case will differ significantly from similar quantities found in the voluminous body of data for uniformly heated tubes and flow channels. Although this latter case has been used in the past as an estimate for the former case, more study has become necessary to examine the three-dimensional temperature and heat flux distributions and related CHF. Work thus far has shown that the non-uniform peripheral heat flux condition enhances CHF in some cases.
In order to avoid the excess costs associated with using electron- or ion-beams to produce the non-uniform heat flux, a new facility was developed which will allow three-dimensional conjugate heat transfer measurements and two-dimensional local subcooled flow boiling heat flux and related critical heat flux measurements.
The configurations under study consist of: (1) a non-uniformly heated cylindrical-like test section with a circular coolant channel bored through the center, and (2) a monoblock which is a square cross-section parallelepiped with a circular drilled flow channel through the center line along its length. The theoretical or idealization of the cylindrical-like test section would be a circular cylinder with half (−90 degrees to +90 degrees) of its outside boundary subjected to a uniform heat flux and the remaining half insulated. For the monoblock, a uniform heat flux is applied to one of the outside surfaces and the remaining surfaces are insulated. The outside diameter of the cylindrical-like test section is 30.0 mm and its length is 200.0 mm. The monoblock square has lengths 30.0 mm. The inside diameter of the flow channel for both types of test sections is 10.0 mm. Water is the coolant. The inlet water temperature can be set at any level in the range from 26.0 °C to 130.0 °C and the exit pressure can be set at any level in the range from 0.4 MPa to 4.0 MPa. Thermocouples are placed at forty-eight locations inside the solid cylindrical-like or monoblock test section. For each of four axial stations, three thermocouples are embedded at four circumferential locations (0, 45, 135, and 180 degrees, where 0 degrees corresponds to that portion of the axis of symmetry close to the heated surface) in the wall of the test section. Finally, the mass velocity can be set at any level in the range from 0.6 to 10.0 Mg/m2s.
Analysis of RELAP5 Drift-Flux Model for Vertical Subcooled Boiling Flow at Low Pressure Conditions
Authors: Končar Boštjan , Kljenak Ivo , Mavko Borut 
Published: November 2021

Abstract
The RELAP5/MOD3.2.2 Gamma code was assessed against low pressure boiling flow experiments performed by Zeitoun and Shoukri (1997) in a vertical annulus. The predictions of subcooled boiling bubbly flow showed that the present version of the RELAP5 code underestimates the void fraction increase along the flow and strongly overestimates the vapor drift velocity. It is shown that in the calculations, a higher vapor drift velocity causes a lower interphase drag and may be a possible reason for underpredicted void fraction development. A modification is proposed, which introduces the replacement of the EPRI drift-flux formulation, which is currently incorporated in the RELAP5 code, with the Zuber-Findlay (1965) drift-flux model for the experimental low pressure conditions of the vertical bubbly flow regime. The improved experiment predictions with the modified RELAP5 code are presented and analysed.
Percolation Theory Applied to Study the Effect of Shape and Size of the Filler Particles in Thermal Interface Materials
Authors: Devpura Amit , Phelan Patrick E. , Prasher Ravi S. 
Published: November 2021

Abstract
An important aspect in electronic packaging is the heat dissipation. Flip-chip technology is widely being used to increase the rate of heat transfer from the chip. A method to further enhance the thermal conductivity is by the use of a thermal interface material between the device and the heat sink attached to it in the flip-chip technology. Percolation theory holds a key to understanding the behavior of thermal interface materials. Percolation, used widely in electrical engineering, is a physical phenomenon in which the highly conducting particles distributed randomly in the matrix form at least one continuous chain connecting the opposite faces of the matrix. This phenomenon was simulated using the matrix method, to study the effect of different shapes and size of the filler particles. The different shapes considered were spherical, vertical or horizontal rods, and flakes in horizontal or vertical orientation. The effect of the size of these particles was also examined. The results indicate that the composites with particles having the largest side in the direction of heat flow will always have a better conductivity than the particles oriented normal to it. Also, from the results, we can choose the best filler size in the composite if we know the filler concentration we are aiming at.
A Thermal Model for Reburning Fuel Injectors in Glass Furnaces
Authors: Swanson L. W. , Koppang R. R. 
Published: November 2021

Abstract
A quasi-steady multi-mode heat-transfer model for retraining fuel injectors in glass furnaces has been developed that predicts the effect of geometry, furnace heat source and heat sink temperatures, radial and axial injector wall conduction, and coolant flow rate on the injector wall temperature distribution. The model imposes a radiation boundary condition at the outlet tip of the injector, which acts as a heat source. A parametric study has been conducted to investigate effects that the furnace gas temperature, reburning methane fuel and purge-air flow rates, and furnace wall temperature have on the injector wall temperature distribution. For nominal operating conditions, highly nonlinear temperature distributions were observed throughout the injector. Operation with methane as the coolant produced an extremely large temperature gradient near the injector tip that could cause excessive thermal stresses in the injector wall. The results also showed that nominal injector operating conditions should prevent alkali deposition at the injector tip and produce injector/metallic disconnect temperatures well below the initial deformation temperature for stainless steel.
Experiments and Numerical Simulations of Flow Patterns of Water Droplets From Fire-Fighting Helicopters
Authors: Satoh Kohyu , Sagae Kohei , Kuwahara Kunio , Yang K. T. 
Published: November 2021

Abstract
In large forest fires over wide areas, aerial fire fighting with water drop from helicopters has been widely employed in the world. After the large earthquake fires in Japan, possibilities were raised to employ similar fire-fighting technique to city fires. However, forest and city fires were inherently different in nature and require different fire-fighting implementations. Since the city fires are concentrated in extent and isolated, thus requiring more dense water application to extinguish fires. As a result, accurate engineering data on the optimum water application relative to a given fire are critically needed to design fire-fighting strategies. This study describes the experiments carried out in open fields using real-life helicopters, in comparison with the 3-D numerical simulations. Numerical simulations can provide reasonable flow patterns of the water droplets from the helicopters, and can be used as a design tool for implementing the fire-fighting technique for real city fires.
A New Method for Estimating the Effects of Thermal Radiation From Fires on Building Occupants
Authors: Torvi David A. , Hadjisophocleous George V. , Hum Joe 
Published: November 2021

Abstract
A new model for estimating the effects of high thermal radiation heat fluxes on occupants has been developed. This model allows the user to specify the type of clothing worn by typical occupants (e.g., street clothing or protective clothing), percentage of body covered by clothing, and occupant characteristics (e.g., age). Numerical models of heat transfer in fabrics and skin are used to estimate the times required to produce burn damage to bare and clothed skin. These skin burn estimates are used along with occupant characteristics to estimate the time-dependent probability of death from a fire. This paper reviews existing models for estimating the effects of high heat fluxes on occupants, describes the heat transfer models used to make skin burn estimates, and compares the results of the new model with those from existing models.