Comparison of liquid water dynamics in bent gas channels of a polymer electrolyte membrane fuel cell with different channel cross sections in a channel flooding situation

Abstract

The transport characteristics of water slugs in a bent gas channel of a polymer electrolyte membrane (PEM) fuel cell are numerically studied using the volume of fluid (VOF) method. To investigate the effects of channel cross-sectional shape in a channel flooding situation, the gas channels (GCs) with one rectangular and two trapezoidal cross sections are compared. Parametric studies are also conducted to evaluate the effects of the contact angle of the top and side walls, the contact angle of the gas diffusion layer (GDL) surface, and the air inlet velocity. Considering both of the water volume fraction (WVF) and GDL water coverage ratio (WCR), the trapezoidal channel with open angles of 60 degrees provides the most favorable performance in a channel flooding condition. Among all the top and side wall contact angles considered, the hydrophobic contact angle of 120 degrees shows the best results. Among the three GDL contact angles of 90, 110 and 140 degrees, the hydrophobic GDL contact angle of 140 degrees provides the most favorable water removal characteristics in a channel flooding situation. For all cross-sectional shapes, the water removal rate increases and the liquid water interface shows more complex patterns as the air inlet velocity increases.