Pore-scale investigation of transport properties and two-phase flow in compressed gas diffusion layers using an integrated FEM-CFD framework

The gas diffusion layer (GDL) is pivotal to water and thermal management in proton exchange membrane fuel cells (PEMFCs), with its transport properties severely altered by assembly-induced mechanical deformation. Existing studies often represent compression through porosity reduction alone, while the influence of GDL microstructural characteristics has received less attention. This study develops an integrated framework combining high-fidelity finite element method (FEM) mechanical simulations and multiphysics-coupled computational fluid dynamics (CFD) analysis. Six stochastically reconstructed GDL microstructures (varying in porosity, fiber diameter, thickness) were tested under 0–2.5 MPa compression. Results show compression impairs gas diffusivity and permeability by narrowing transport pathways but enhances thermal/electrical conductivity via increased fiber contacts, with a 58% to 78% porosity rise doubling diffusivity. Volume of fluid (VOF) two-phase flow simulations reveal that compression elevates capillary resistance, inhibiting liquid water invasion and reducing saturation at the same capillary pressure. Fiber diameter and porosity couple with compression-driven deformation, while GDL thickness uniquely modulates liquid storage capacity without changing the fundamental liquid transport mechanism. These results provide useful insights for GDL design and assembly in PEM fuel cells.