The present work presents a three-dimensional, non-isothermal computational model of PEMFC, implemented in the CFD code Fluent. The model accounts for all major transport phenomena, including: water and proton transport through the membrane; electrochemical reaction; transport of electrons; transport and phase change of water in the gas diffusion electrodes; diffusion of multi-component gas mixtures in the electrodes; and mass transport in the gas flow channels. First, the polarization behavior or steady state performance of the PEMFC has been simulated and then the transient response subjected to a variable load has been studied. In the steady state analysis, the polarization curves, obtained by single phase and two-phase numerical simulations, have been compared with the experimental data given in literature. A good agreement is evident for the curve given by the two-phase simulations, while the single-phase model is unable to reproduce the experimental data at the high current densities. A parametric study has been done to validate the model and the predicted polarization curves have been compared with experiments. Finally unsteady simulations have been performed. The effect of the rate of change in cell voltage on cell performance for three different rates have been shown. The transient results demonstrate that current density overshoots the stabilized state value when cell voltage is abruptly decreased.

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