Analytical model of flow maldistribution in polymer electrolyte fuel cell channels

Abstract

Gas–liquid, two-phase flow through channels of a polymer electrolyte fuel cell (PEFC) is of great interest as reactant oxygen is supplied and liquid product water is removed via these PEFC channels. Gas diffusion layer (GDL) intrusion in the channels, which is inherent to the process of PEFC cell and stack assembling, increases the local flow resistance in the intruded channels and consequently lowers their flowrates. This flow maldistribution renders the intruded channels more susceptible to liquid water accumulation or flooding. A one-dimensional analytical model is developed in this work to elucidate the two-phase flow maldistribution in PEFC channels resulting from GDL intrusion. Relative humidity (RH) and the stoichiometric flow ratio of inlet gases are found to be the two key parameters controlling the flow maldistribution in PEFC channels. Interestingly, our analysis shows that decreasing the inlet RH worsens flow maldistribution. As GDL intrusion in channels is inevitable, a good flow-field design must be inherently tolerable to flow maldistribution. Using the analytical model presented herein, the number of flow channels and their U-turns are optimized to minimize the detrimental effect of GDL intrusion.