Hydrogen-Water Flow Regime Transitions Applied to Anode Flow Phenomena in a PEMFC

Although water is produced on the cathode side of a polymer electrolyte membrane fuel cell (PEMFC), it is known to migrate to the anode, where the two-phase hydrogen-water interactions become critical to keep the channels clear for effective reactant delivery. Hydrogen-water flow regime transitions were experimentally investigated and compared to air-water transitions in a 1.0 mm square channel. Gas superficial velocities were evaluated for an anode stoichiometric ratio of 2.0 over a current density range from 0.1 A/cm² to 2.0 A/cm². Liquid superficial velocities were controlled at the corresponding cathodic water production rate. It is shown that the annular transition in a hydrogen system occurs at as much as twice the gas velocity required for the same transition in an air system. At the low liquid flux expected in the anode channels of a PEMFC, a transition from slug to annular two-phase flow will occur at an unobtainable velocity for efficient fuel cell operation.