Gradient‐Porosity Metal Foam Flow Fields for Uniform Mass and Heat Transfer in PEMFCs

ABSTRACT Nonuniform distributions of reactants, liquid water, and temperature constrain the performance and durability of proton exchange membrane fuel cells (PEMFCs), especially at high current densities. This study numerically evaluates a novel flow field design where metal foam is symmetrically embedded in both the anode and cathode of straight channels, focusing on the effect of porosity grading on multiphysics transport and overall cell performance. A three‐dimensional, nonisothermal, two‐phase PEMFC model is developed and validated against published polarization data. Nine porosity configurations are examined, comprising four uniform foams and five with a linear porosity gradient from the channel side (with higher porosity) to the gas diffusion layer (GDL) side (with higher density). Compared to a conventional parallel channel, the optimized graded foam channel increases the peak power density from 0.494 to 0.588 (a 19.0% improvement), raises the total current by 22.3%, and reduces the average membrane temperature by approximately 10% while improving temperature uniformity. Field analyses reveal that the graded structure enhances under‐rib oxygen supply, directs liquid water toward high‐porosity regions for removal, and strengthens lateral heat spreading. These mechanisms collectively expand the effectively utilized reaction zone and mitigate flooding and local hot spots. The findings provide preliminary numerical guidance for the further development of gradient‐porosity metal foam flow fields in PEMFCs.