A two-phase non-isothermal mass transport model for direct methanol fuel cells

A two-phase non-isothermal mass transport model is presented in this paper. The heat and mass transfer across the membrane electrode assembly (MEA), coupled with the electrochemical reactions in the catalyst layers (CLs), are calculated based on the classical two-phase flow model in the porous media. The effect of methanol crossover on the cell performance and the non-equilibrium evaporation/condensation of water are considered in this model. The modeling results show that the distribution of temperature in the MEA is not uniform, and the highest temperature appears in the cathode CL. The non-uniform distributed methanol concentration leads to the non-uniform distributed methanol oxidization reaction (MOR) rate while the oxygen reduction reaction (ORR) rate mainly depends on the distribution of the local overpotential in the cathode CL. The increase in the open ratio of the flow field plate results in more uniform distribution of physical fields in the fuel cell and the cell performance is also improved with a larger open ratio.