Numerical studies on rib and channel designs considering interfacial contact resistance

Abstract

The mass transport and ohmic losses in proton exchange membrane fuel cells (PEMFCs) is significantly influenced by the channel to rib width ratio (CRWR), particularly when accounting for the interfacial contact resistance between bipolar plates (BPs) and gas diffusion layers (GDLs) (ICR_BP-GDL). Both the determination of the optimal CRWR value and the development of an efficient flow field structure are significantly influenced by ICR_BP-GDLs. To investigate this, three-dimensional numerical models were developed, revealing that selecting an optimal CRWR tailored to specific ICR_BP-GDL values can effectively balance mass transport and ohmic losses. Building on this insight, a novel island two-dimensional flow field design is proposed, demonstrating the ability to enhance oxygen transport to the catalyst layer (CL) and achieve a more uniform oxygen distribution without increasing ohmic losses. Compared to conventional straight and serpentine flow fields, the island flow field improves output power density by 4.5% and 3.5%, respectively, while reducing the liquid water coverage ratio by 30%. Additionally, the study identifies optimal CRWR values for conventional flow fields corresponding to ICR_BP-GDLs of 2.5, 5, 10, 20, and 40 mΩ·cm² as 1.5, 1.5, 1.0, 0.67, and 0.43, respectively. For the island flow field, the optimal CRWRs are consistently smaller—1.5, 1.0, 0.67, 0.43, and 0.43—due to its superior mass transfer capability. This work provides a valuable framework for optimizing flow field designs to achieve improved PEMFC performance.