Numerical Predictions of Transport Phenomena in a Proton Exchange Membrane Fuel Cell

Abstract

Transport phenomena play an important role in the performance of the proton exchange membrane fuel cell. Water generated by electrochemical reactions and transported by osmotic drag and back diffusion can cause saturation or flooding, preventing oxygen from reaching catalysis sites. Dehydration may also occur, resulting in poor proton conductivity. Balancing water content within the membrane involves judicious water and heat management strategies. In this paper, detailed mathematical models for the prediction of all significant aspects of physicochemical hydrodynamics for a proton exchange membrane fuel cell are employed. Fully coupled heat and mass transfer and electrochemistry are considered, and the dependence of water transport on these factors is taken into account. Two distinct approaches were considered: a fully three-dimensional approach and a hybrid scheme, whereby the electrochemistry and electric fields are treated as locally one dimensional in the membrane assembly. Comparisons between the two approaches are presented and discussed. The numerical results suggest a dependence of the rate-of-water removal on temperature, current density, and inlet humidification levels, and also that the oxygen concentration in the air channels significantly affects current density distribution.