Numerical investigation of liquid water transport and distribution in porous gas diffusion layer of a proton exchange membrane fuel cell using lattice Boltzmann method

Lattice Boltzmann method (LBM) is used to investigate liquid water transport and distribution in a porous gas diffusion layer (GDL). The GDL with microscopic porous structures is obtained from three-dimensional reconstruction using the stochastic method, and its macroscopic transport properties including permeability and effective diffusivity are numerically predicted which agree well with the existing experimental results. Simulation results show that liquid water transport mechanism in the GDL is capillary fingering and liquid water pathway is interconnected, which confirms the previous experimental results in literature. Further, effects of GC wettability are explored and it is found out that a hydrophilic GC leads to less liquid water accumulated in the GDL compared with a hydrophobic GC. In addition, effects of GDL wettability on liquid water distribution are explored. Simulation results show that PTFE content itself cannot determine liquid water distribution inside the GDL and detailed distributions of hydrophobic and hydrophilic regions within the GDL also play an import role. Moreover, a hydrophilic GDL is more beneficial for reactant transport than a hydrophobic GDL if liquid water presents as separated droplets or films in the GDL.