Effect of the porosity distribution on the liquid water transport in the gas diffusion layer of PEMFC

Water management significantly influences the life and power output of the proton exchange membrane fuel cell (PEMFC). The gas diffusion layer (GDL) provides key transport paths of reactant gas and liquid water in the PEMFC. This study uses the volume of fluid (VOF) method to numerically investigate the liquid water transport in the GDL with different porosity distributions. The GDL geometry is reconstructed based on the stochastic parameter method. Five GDL structures with different porosity distributions are investigated on the liquid water transport. And different contact angles are defined on the carbon fiber surface and their effect is discussed. The results show that the porosity distribution and contact angle have dramatic influence on the water distribution and saturation in the GDL. The liquid water accumulation tends to occur in the high porosity GDL region. The water saturation is higher and flow rate is lower in the GDL with inverted “V” shaped porosity distribution than “V” shaped porosity distribution. The water saturation and flow rate is smaller when the porosity gradient is greater for both the “V” and inverted “V” shaped porosity, due to fewer water penetration paths. The water saturation in the hydrophilic GDL is higher than in the hydrophobic GDL for all the five porosity distributions.