Full‐Scale Simulation and Performance Improvement of PEMFCs With Different Flow Channel Cross‐Sections

Flow‐channel design plays a decisive role in the performance and water management of large‐scale proton exchange membrane (PEM) fuel cells (PEMFCs), especially for parallel flow fields (FFs) that feature low pressure drop but are prone to flow maldistribution. In this study, a three‐dimensional (3D) multiphase CFD model is developed to systematically investigate the effects of cathode flow‐channel cross‐sectional geometry on mass transport and electrochemical performance in a large‐area parallel‐flow PEMFC. Square, trapezoidal, and inverted‐trapezoidal channel cross‐sections are comparatively analyzed under identical structural parameters and operating conditions. The results show that the trapezoidal channel achieves the highest current density and power density by enhancing near‐gas diffusion layer (GDL) gas velocity and under‐rib convection, thereby improving oxygen transport and reaction uniformity, albeit with a higher liquid‐water saturation and potential flooding risk. In contrast, the inverted‐trapezoidal channel exhibits the lowest pressure drop and liquid‐water saturation due to its larger effective flow area but suffers from reduced reaction intensity and inferior overall performance. The square channel presents intermediate behavior. Temperature distributions remain highly uniform for all configurations, indicating a limited influence of channel cross‐section on thermal behavior. These results provide useful guidance for the engineering design of channel cross‐sections in large‐scale PEMFCs under different design priorities.