Full-scale three-dimensional simulation of air cooling metal bipolar plate proton exchange membrane fuel cell stack considering a non-isothermal multiphase model

Abstract

Addressing issues such as the mass transfer characteristics and internal performance consistency of the air cooling (AC) proton exchange membrane fuel cell (PEMFC) stack. A full-scale AC metal bipolar plate (BP) stack is proposed in this study, comprising inlet and outlet manifolds, membrane electrode assembly (MEA), reaction flow field (FF) and cooling FF. The coupling of electrochemical reactions and heat and mass transfer processes in the stack is simulated using a non-isothermal multiphase numerical model. The characterization of the mass spatial distribution in the stack is explored by varying the stoichiometric ratio of the cathode gas, the thermal boundary conditions, the flow direction of the reaction gas and the air inlet flow configuration. According to the simulation results, it is found that, initially, the simulation errors in the one-dimensional (1D) AC stack are large and mainly concentrated in the concentration loss region. Subsequently, the increased stoichiometric ratio enhances the proton exchange membrane (PEM) water content, improves the local current density by 1.6% and facilitates the discharge of waste heat from the stack. Furthermore, thermal boundary conditions significantly affect the distribution of temperature uniformity in the stack, with high local temperatures causing significant water vapor generation and resulting in oxygen dilution. The counter-flow of hydrogen and air enhances the electrochemical reaction rates in the cathode catalyst layer (CCL) by 0.353%, with the lowest liquid water content in the seventh cell, influenced by the uneven distribution of manifold flow. Finally, changing the position of the cathode manifold gas inlet indicates that the positive flow of the cathode and AC inlets from the Z axis reduces the maximum stack temperature and water vapor by 1.04% and 0.38% respectively. The CCLs in Case 4 have optimal oxygen distribution and output voltages of approximately 0.66 V per fuel cell (FC).