Probing Effects of GDL Microstructure on Liquid Water Transport by Pore Network Modeling

Abstract

A pore-network model is developed to study the liquid water movement and flooding of gas diffusion layer (GDL) with GDL morphology taken into account. We have computed capillary pressure and relative permeability as function of liquid water saturation. The dynamics of liquid water transport and evolution of the saturation profile in GDL under realistic fuel cell operating conditions is examined for the first time. It is found that capillary forces control the liquid water movement in the GDL and liquid water moves in connected clusters with finger-shaped liquid water fronts. Relative permeability of liquid water is found to be very small at high saturation due to poor connectivity among liquid water clusters. The effect of mixed wettability (contact angle varying from 60o-120o) on capillary pressure and relative permeability functions is also investigated.