Daniel Juarez-Robles

Experimental study and comparison of various designs of gas flow fields to PEM fuel cells and cell stack performance

In this study, a significant number of experimental tests to PEM fuel cells were conducted to investigate the effect of gas flow fields on fuel cell performance. Graphite plates with various flow field or flow channel designs, from literature survey and also novel designs by the authors, were used for the PEM fuel cell assembly. The fabricated fuel cells all have an effective membrane area of 23.5 cm2. The results showed that the serpentine flow channel design is still favorable, giving the best single fuel cell performance amongst all the studied flow channel designs. A novel symmetric serpentine flow field was proposed for relatively large size fuel cell application. Four fuel cell stacks each including four cells were assembled using different designs of serpentine flow channels. The output power performances of fuel cell stacks were compared and the novel symmetric serpentine flow field design is recommended for its very good performance.

Entropy Generation Analysis for a PEM Fuel-Cell With a Biomimetic Flow Field

The present paper shows an entropy generation analysis for a PEM fuel cell. The numerical model takes into account the complete solution of Navier-Stokes, energy conservation, species conservation and two potential fields for the transport of electrons and protons in the collectors and membrane respectively. The entropy generation equation is added to the governing equations using the solutions provided from the energy, momentum, species and potential flow equations. The entropy generation analysis reveals the locations where the main losses (irreversibilities) are produced. This in consequence shows the best flow field to minimize the entropy production. A new parameter is proposed in this work that will compare the entropy production due to the mass flow to the total entropy production.Copyright

Three Dimensional Analysis of a PEM Fuel Cell with the Shape of a Fermat Spiral for the Flow Channel Configuration

This work presents the analysis of a non-isothermal three-dimensional model in single phase of a PEM fuel cell with an innovative flow field path in the form of the Fermat spiral, i.e. two concentric spirals. The model is used to predict the current density contours and the water content in all of the zones of the fuel cell. The three-dimensional model includes: the gas flow channels with the shape of the new geometry proposed, the current collectors, gas diffusion layers, catalyst layers on both sides of the model, anode and cathode, and a proton exchange membrane in between. The model solves the energy equation, mass conservation, and species transport equations, including the source terms due the electrochemical effects occurring in the cell. The results show a higher average current density than the fuel cells with conventional flow paths, showing also that the current density attained is more uniform from the inlet to the outlet of the flow channels.Copyright

Parametric Study of a Symmetric Flow Distributor

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

3D Analysis of a New Radial Channel for PEMFCs and Comparison With a Traditional Channeled System

The present study shows a 3D analysis of a new radial geometry for a PEM fuel cell flow field. The objective of this study is to understand the effects of this configuration on the fuel cell performance. The geometry is proposed with the objective to increase the fuel cell performance while reducing the pressure drop. In order to compare the results, a conventional commercial geometry was also analyzed and then both geometries were compared via polarization and power curves. The geometry proposed in this work shows quite a good improvement with respect to conventional geometries reducing the pressure drop and generating also a good power.Copyright

New Radial-Based Flow Configurations for PEMFCs

This work presents the results of a study of a new radial configuration proposed for the gas flow field for a PEM fuel cell. The objective of this study is to understand the effects of this configuration on the fuel cell performance. The results are compared with the radial designs proposed in previous analysis. The proposed designs on this work show an improvement on the cell performance, with a better use of the reaction area compared with a flow free radial design. The results also show that the effect of channeling the flow inside these radial configurations helps to improve the fuel cell performance.Copyright

CFD Analysis of a Constructal Flow Distributor as a Bipolar Plate for PEMFC’s

A plate-type constructal flow distributor is implemented as a gas distributor for a proton exchange membrane fuel cell. A 3D complete model is simulated using CFD techniques. The fuel cell model includes the gas flow channels, the gas diffusion layers and the membrane electrode assembly (MEA). The governing equations for the mass and momentum transfer are solved including the pertinent source terms due to the electrochemical reactions in the different zones of the fuel cell. Similar configurations have been already presented in previous studies but using the flow distributor as a heat remover; however, the similarity between heat transfer and mass transfer phenomena has lead to investigate the performance of such distributors in fuel cells. In terms of flow analysis, it was found that the constructal flow distributor presents a low pressure drop for a wide range of Reynolds number conditions at the inlet, as well as an excellent uniformity of flow distribution. Some of the advantages of the constructal model, over traditional flow patterns, are the uniformity of current density distribution, the adequate consumption of species and the possibility to increase the bifurcation levels to cover a larger reaction area.Copyright