Multiphase Simulations and Design of Validation Experiments for Proton Exchange Membrane Fuel Cells

Proton exchange membrane fuel cells directly convert into electricity the chemical energy of hydrogen and oxygen from air. The by-products are just water and waste heat. Depending on the operating conditions the water may be in the liquid or gas phase, and liquid water can hence plug the porous media in the fuel cell, and, more importantly, the flow channels and outlet ports of a single cell in a stack. These problems may be avoided if the fuel cell operates in a way that both the anode and cathode outlet stream are exactly fully humidified, i.e. the relative humidity is at 100 %. Such operation can conceivably be obtained by adjusting the operating conditions using dew point diagrams. In this paper numerical results will be presented of two different flow field arrangements, both using the interdigitated flow field. It will be shown that arranging the gas streams in a counter-flow, “x-flow” modus is the preferred option. Moreover, a detailed analysis of the preferred channel width and land area shows that the finest pitch is predicted to yield the highest membrane hydration levels and is thus preferred.