Two-phase modeling of gas purge in a polymer electrolyte fuel cell

Gas purge intended to minimize residual water in a polymer electrolyte fuel cell (PEFC) is critical for successful shutdown and sub-zero startup. In the present work, we present a two-phase transient model describing water removal from PEFC under gas purge conditions. The role of back diffusion from the cathode to anode along with liquid water transport in the gas diffusion layers behind the drying front and vapor diffusion ahead of the drying front is highlighted. The underlying ineffectiveness of cathode-only purge is outlined. The model predictions are compared with experimental results under various purge conditions. A good match with experiments is obtained at higher purge temperatures whereas some differences in the HFR profile is observed at lower temperatures. The role of drying front morphology in addressing the observed differences between numerical and experimental results is hypothesized.