Effect of wettability heterogeneity and compression on liquid water transport in gas diffusion layer coated with microporous layer of PEMFC

Abstract

This study applied the pseudo-potential Lattice Boltzmann method (LBM) for investigating liquid water transport in the microporous layer (MPL) and gas diffusion layer (GDL) of polymer electrolyte fuel cell. The MPL and GDL reconstruction is performed by using a stochastic method. Unlike previous studies that examined the GDL as two distinct layers of hydrophilic and hydrophobic, this study considered the wettability heterogeneity. In the present study, some of the carbon fibers in the GDL are randomly considered hydrophilic. Moreover, liquid water transport in the compressed and uncompressed GDL with different hydrophilic fibers percentage are compared. The effect of hydrophilic fibers percentage and the compression ratio of the GDL on the liquid water saturation level, the steady-state time, and the formation and growth of droplets in the gas channel (GC) are investigated. The results indicated that more than 10% of hydrophilicity of the fibers lead to the formation of discontinuous water clusters. This phenomenon increased the steady-state time and water saturation level significantly. The simulation showed that compression increased the number of discontinuous water clusters in the GDL. The obtained results demonstrated that the hydrophilic fibers may have positive or negative effects on water transport in the GDL due to their location. In addition, this study indicated that for 10% of hydrophilic fibers with 10% compression, water saturation level and time required to reach steady-state decreased by 5.2% and 22% respectively compared to purely hydrophobic GDL.