Award Date

1-1-2008

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

First Committee Member

Yitung Chen

Number of Pages

113

Abstract

Performance of proton exchange membrane (PEM) fuel cells is dependent of a set of complex physical and chemical processes occurring simultaneously. Bipolar plates are important components of PEM fuel cells because they are the first stage of the flow distribution system. A non-uniform flow distribution across the active reaction area within PEM fuel cells will probably lead to an unbalanced use of the precious catalyst, and a lower overall efficiency of the device than expected. A three-dimensional numerical model has been developed to evaluate the PEM fuel cell including the current collectors, flow channels, gas diffusion layers, and membrane. This model takes into account the multi-component fluid flow in porous medium, electrochemical kinetics and water transport across membrane by electro-osmosis, diffusion and convection. Different fuel cell design cases, associated with their own bipolar plate designs, have been studied. Numerical results from the developed model show that the predicted polarization curve is in very good agreement with the experimental data. Results also show that the fluid flow distribution in the baseline design is very non-uniform, which is not favorable for the use of catalyst and the high efficiency fuel cell. In order to improve the fuel cell efficiency, the bipolar plate design has been optimized, which then greatly increases the current density or power of fuel cell under the same operating conditions compared with the baseline design. Parametric study of the fuel flow rate on the current density has also been performed. Results reveal that the flow rate of fuel or air greatly influences the water content distribution within the proton exchange membrane, thus significantly impacting the performance of the PEM fuel cell. Generally, uniform fluid flow inside the entire plates and the proper humidity of the fuel cell are significantly important to the high performance PEM fuel cell.

Keywords

Cell; Design; Dimensional; Exchange; Fuel; Membrane; Numerical; Proton; Study; Three

Controlled Subject

Mechanical engineering

File Format

pdf

File Size

3031.04 KB

Degree Grantor

University of Nevada, Las Vegas

Language

English

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