MASS TRANSPORT ANALYSIS IN A PULSATING CATHODE FLOW OF PEM FUEL CELL

A theoretical and experimental study is performed for the mass transfer enhancement by a cathode flow pulsation in a fuel cell. The cathode flow pulsation is considered to reduce the stoichiometry of air. Emphasis is given to explicit role of the cathode flow pulsation on the mass transfer enhancement over the electrode surface. A simple 2D mass transport model for a pulsating cathode flow is developed to investigate the effect of cathode flow pulsation on the oxygen concentration distribution over the cathode channel length in the mass transfer limit situation. Comprehensive analytic solutions disclose the improved concentration distribution by the flow pulsation, which increases mass transfer from the cathode channel to the catalyst layer. Enhancement of mass transport is more pronounced at lower Reynolds numbers. The performance enhancement by flow pulsation is shown to be consistent with the experiment of a 10-cell proton exchange membrane fuel cell stack. The effects of the pulsating frequency on the fuel cell performance are examined at a fixed pulsating velocity amplitude. The experimental results obtained show that both the maximum power density and limiting current density are substantially enhanced when the pulsating component is added to cathode mainstream flow.