Water Transport Dynamics in Fuel Cell Micro-Channels

摘要

The formation, phase change and transport of water have a major impact on the operation, performance and durability of PEM fuel cells, specifically in terms of start up, including freeze-start, transient response and degradation. Net water balance is primarily determined by the water production rate at the cathode, and transport across the membrane via diffusion and electro-osmotic drag. At higher currents, excessive water condensation can lead to ‘flooding’ of the cathode porous layers. Eventually, discrete water droplets can emerge through the pores of the gas diffusion layer (GDL) into the air distribution micro-channels. Such droplets may grow and coalesce, partially or completely blocking the transport pathways for the reactant (particularly oxygen), and also causing a substantial increase in pressure drop. The resulting starvation of the reaction sites induces dips in current density as well as flow maldistribution.