Computational Engineering of Porous Flow Field PEFCs to Enable High Temperature High Power Density Operation

Abstract

A comprehensive 2D + 1 multi-phase computational model has been applied to polymer electrolyte fuel cells with a porous metallic flow field to investigate operating strategies which enable high power density operation in dry, elevated temperature environment. Extensive experimental model validation has been completed under a wide range of temperature, pressure, stoichiometry and humidity conditions. Both qualitative and quantitative agreement has been achieved in regard to voltage, area-specific resistance, and net water drag coefficient. Internal water distribution predictions show that modest changes in operating parameters on the cathode side help maintain a hydrated anode stream and thus effectively push the envelope of stable operating temperature 20°C higher, enabling more efficient heat dissipation in coolant system. Results also show that thermo-osmotic water flux across the membrane, as observed and measured experimentally, can be significant compared to electro-osmosis under high current (> 2 A/cm2) hot and dry conditions, even with thin electrolyte membranes.