Numerical investigations of vapor condensation and water transport in gas diffusion layers of PEMFC

Abstract

Water transport in vapor/liquid form in gas diffusion layers (GDL) of proton exchange membrane fuel cell (PEMFC) are numerically investigated in this study. A stochastic method is employed to reconstruct the 3D structured GDL, then a validated phase change solver is developed and implemented in the OpenFOAM platform to simulate the vapor condensation process. Comprehensive simulations are carried out to analyze the GDL porosity distribution, compressed deformation, mass flow rate, local temperature and contact angle effects on the vapor condensation and transport dynamics. Two GDL with gradient porosities and one with TGP-H-060 type are reconstructed to compare the vapor/liquid-water transport behaviors. It is found that the spatial distribution of the condensate water is comparatively different from the liquid water transport patterns. It reveals that the water transport in liquid form was much more sensitive to the GDL design, while it is more applicable in vapor form. Due to the GDL compression, the vapor/liquid water transport are impeded, especially in the middle layers of the GDL and large velocity separations are detected during the vapor transport. Meanwhile, the results of the parametric analysis indicate that water transport in vapor form provides more options in avoiding water flooding. This study is significant to deepen our understanding on the vapor condensation process and water transport dynamics in GDL, which can further guide the GDL design and optimization.