Concentration and ohmic losses in free-breathing PEMFC

Non-isothermal and three-dimensional simulations were carried out to study concentration and ohmic losses in free-breathing PEMFC under diverse conditions. Flow fields, species transport, transport of water in polymer membrane and movement of liquid water in cathode and anode porous layers were determined. Numerical results were obtained under different hydrating conditions, cell temperatures, cathode catalyst loadings and channel lengths. Current density and polymer electrolyte water content distributions as well as average power density were used as main output variables to study effects of operative conditions on performance. Results show that slow oxygen transport to active sites constitutes the most limiting factor to consider. Dehydrating conditions slightly affect free-breathing PEMFC performance. The numerical model showed to be suitable to study diverse phenomenon involved in free-breathing PEMFC performance. (C) 2007 Elsevier B.V. All rights reserved.