The Experts below are selected from a list of 282 Experts worldwide ranked by ideXlab platform
Peiwen Li - One of the best experts on this subject based on the ideXlab platform.
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numerical investigation of the performance of Symmetric Flow distributors as Flow channels for pem fuel cells
International Journal of Hydrogen Energy, 2012Co-Authors: Bladimir Ramosalvarado, Abel Hernandezguerrero, Daniel Juarezrobles, Peiwen LiAbstract:This work reports on the performance of a single PEM fuel cell using Symmetric Flow patterns as gas delivery channels. Three Flow patterns, two Symmetric and one serpentine, are taken from the literature on cooling of electronics and they are implemented in a computational model as gas Flow channels in the anode and cathode side of a PEMFC. A commercial CFD code was used to solve the physics involved in a fuel cell namely: the Flow field, the mass conservation, the energy conservation, the species transport, and the electric/ionic fields under the assumptions of steady state and single phase. An important feature of the current modeling efforts is the analysis of the main irreversibilities at different current densities showing the main energy dissipation phenomena in each cell design. Also, the hydraulic performance of the Flow patterns was studied by evaluating the pressure drop and pumping power. The first part of this work reveals the advantages of using a serpentine pattern over the base Symmetric distributors. The second part is an optimization of the Symmetric patterns using the entropy minimization criteria. Such an optimization led to the creation of a Flow structure that promotes an improved performance from the point of view of power generation, uniformity of current density, and low pumping power.
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Parametric Study of a Symmetric Flow Distributor
Volume 9: Heat Transfer Fluid Flows and Thermal Systems Parts A B and C, 2009Co-Authors: Bladimir Ramos-alvarado, Abel Hernandez-guerrero, Daniel Juarez-robles, Peiwen Li, J. C. Rubio-aranaAbstract:A parametric study was conducted in order to reduce the pressure drop and to improve the uniformity of Flow distribution in a Symmetric Flow distributor. A CFD model was employed to simulate the Flow behavior by solving the Navier-Stokes equations in a complete 3D model. The present work is a complete parametric study of a base model, reported in previous studies, but keeping the same Flow pattern. To improve the performance of the base design, three known successive parametric ratios, as functions of the hydraulic diameters of the channels, were tested in order to study the advantages and disadvantages of each one in terms of two dimensionless parameters that measure the uniformity of Flow distribution. A remarkable improvement in the performance of the base model was achieved by modifying the width ratio of the channels. The present work is a contribution to the study of Flow distributors to be used as heat exchangers, PEMFC Flow channels and other Flow devices.© 2009 ASME
Andre Lisibach - One of the best experts on this subject based on the ideXlab platform.
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characteristic initial value problem for spherically Symmetric barotropic Flow
Journal of Hyperbolic Differential Equations, 2017Co-Authors: Andre LisibachAbstract:We study the equations of motion for a barotropic fluid in spherical Symmetric Flow. Making use of the Riemann invariants, we consider the characteristic form of these equations. In a first part, w...
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characteristic initial value problem for spherically Symmetric barotropic Flow
arXiv: Analysis of PDEs, 2016Co-Authors: Andre LisibachAbstract:We study the equations of motion for a barotropic fluid in spherical Symmetric Flow. Making use of the Riemann invariants we consider the characteristic form of these equations. In a first part, we show that the resulting constraint equations along characteristics can be solved globally away from the center of symmetry. In a second part, given data on two intersecting characteristics, we show existence and uniqueness of a smooth solution in a neighborhood in the future of these characteristics.
Andre Revil - One of the best experts on this subject based on the ideXlab platform.
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theory of transient streaming potentials associated with axial Symmetric Flow in unconfined aquifers
Geophysical Journal International, 2009Co-Authors: Bwalya Malama, Kristopher L Kuhlman, Andre RevilAbstract:SUMMARY We present a semi-analytical solution for the transient streaming potential response of an unconfined aquifer to continuous constant rate pumping. We assume that Flow occurs without leakage from the unit below a transverse anisotropic aquifer and neglect Flow in the unsaturated zone by treating the water-table as a moving material boundary. In the development of the solution to the streaming potential problem, we impose insulating boundary conditions at land surface and the lower boundary of the lower confining unit. We solve the problem exactly in the double Laplace–Hankel transform space and obtain the inverse transforms numerically. The solution is used to analyse transient streaming potential data collected during dipole hydraulic tests conducted at the Boise Hydrogeophysical Research Site in 2007 June. This analysis yields estimates of aquifer hydraulic parameters. The estimated hydraulic parameters, namely, hydraulic conductivity, transverse hydraulic anisotropy, specific storage and specific yield, compare well to published estimates obtained by inverting drawdown data collected at the field site.
V Eswaran - One of the best experts on this subject based on the ideXlab platform.
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a numerical study on the forced convection heat transfer from an isothermal and isoflux sphere in the steady Symmetric Flow regime
International Journal of Heat and Mass Transfer, 2006Co-Authors: S D Dhole, R P Chhabra, V EswaranAbstract:Abstract The effects of Reynolds and Prandtl numbers on the heat transfer characteristics of an unconfined sphere for different thermal boundary conditions (isothermal and isoflux) on the sphere surface have been investigated numerically by using a finite volume method for the range of conditions as 5 ⩽ Re ⩽ 200 and 0.7 ⩽ Pr ⩽ 400 (the maximum value of Peclet number being 2000). Based on the numerical results obtained herein, heat transfer correlations are developed for the constant temperature and the constant heat flux boundary conditions on the solid sphere surface in the steady Symmetric Flow regime. The variation of local Nusselt number on the sphere surface shows the effect of Prandtl number on heat transfer from a sphere in this Flow regime. In addition, this work also demonstrates an approach to solve such Flow problems using the Cartesian form of the field equations.
Hiroshi Yamaguchi - One of the best experts on this subject based on the ideXlab platform.
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bifurcation phenomenon for forced convection of supercritical co2 sudden expansion Flow and heat transfer in Symmetric regime
International Journal of Heat and Mass Transfer, 2010Co-Authors: Bili Deng, Xinrong Zhang, Hiroshi YamaguchiAbstract:Abstract A computational investigation of laminar forced convection of supercritical CO2 Flow in horizontal duct with plane Symmetric sudden expansion and its bifurcation phenomenon are presented in this study. The computations were conducted at various Reynolds numbers for cases of different wall heat fluxes. A parameter named recirculation disturbance intensity is introduced that is aimed to shed some light on the reduction of Flow stability when Reynolds number or wall heat flux increases. The Nusselt number distribution in the Symmetric Flow regime is presented, the variations of peak Nusselt number and its relative location are discussed. Wall friction coefficient and pressure coefficient distributions are presented and discussed.
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Stability of Flow in a channel with a suddenly expanded part
Physics of Fluids, 1996Co-Authors: J. Mizushima, H. Okamoto, Hiroshi YamaguchiAbstract:The stability of a two‐dimensional Flow in a Symmetric channel with a suddenly expanded part is investigated numerically and analyzed by using the method of the nonlinear stability theory. From results of the numerical simulation, it is shown that the Flow is steady, Symmetric and unique at very low Reynolds numbers, while the Symmetric Flow loses its stability at a critical Reynolds number resulting in an appearance of aSymmetric Flow. The transition from the steady Symmetric Flow to the steady aSymmetric one is found to occur due to the symmetry breaking pitchfork bifurcation when the aspect ratio, the ratio of the length of the expanded part to its width, is large. It is also found that the bifurcated Flow becomes Symmetric again when the Reynolds number is increased and the resultant Symmetric Flow loses its stability becoming periodic in time as the Reynolds number is further increased. On the other hand, when the aspect ratio is small there occurs no pitchfork bifurcation and the direct transition f...
