An engineering approach to optimal metallic bipolar plate designs reflecting gas diffusion layer compression effects

Abstract

GDL (Gas diffusion layer) intrusion into gas feeding channels narrows the effective channel cross-sectional area and eventually results in performance degradation of PEFCs (polymer electrolyte fuel cells). Therefore, cross-sectional channel design of metallic bipolar plates should be optimized to resolve this problem. In this study, effects of the cross-sectional configuration of metallic gas channels on pressure drops are numerically investigated for the comprehensive fluid dynamic analysis of channel flow. Multi-physics numerical systems combining solid mechanics and fluid dynamics are applied to figure out the GDL behavior. First, static structural analysis is performed to determine elastic deformation of GDLs under clamping forces. Subsequently, computational flow analysis in the deformed regions is conducted to visualize flow patterns and estimate corresponding pressure drops. Four cross-sectional parameters are selected: channel to rib width ratio, draft angle, inner fillet radius and clamping pressure. Results are validated against experimental data. The GDL intrusion is found to be greatly affected by draft angle and channel to rib ratio. Cross-sectional area is reduced down to 45% in the most shrunk channel, leading additional pressure drop of 0.12 bar. It is suggested that fluid dynamics should be combined with solid mechanics for better accuracy in computational fuel cell modeling.