Lattice Boltzmann simulation of liquid water transport in microporous and gas diffusion layers of polymer electrolyte membrane fuel cells

In this study, the lattice Boltzmann method (LBM) is used to investigate liquid water transport in the microporous layer (MPL) and gas diffusion layer (GDL) of polymer electrolyte membrane fuel cells (PEMFCs). Two-phase LB simulations are performed with modeled porous geometries that imitate multi-layer porous transport layers (PTLs) consisting of an MPL and a GDL. The simulation conditions are closely matched to the actual liquid water transport conditions in the PEMFCs. The results indicate that invasion-percolation processes due to strong capillary effects govern liquid water transport in PEMFCs. In addition, LB simulations are conducted by varying the intrusion thickness of the MPL and the surface wettability of the PTL. The results clearly show that the liquid water content can be reduced in the PTL by employing a thicker MPL and/or more hydrophobic surfaces. The steady-state water distribution is observed to occur more rapidly as the MPL becomes thicker or as the solid surfaces become more hydrophobic. Furthermore, several dynamic liquid water transport behaviors are identified from the results and explained in detail.