Abstract: The heat transport between a fuel cell(FC) and the external thermal environment and the mass transport of the porous layer will affect the hydrothermal, gas-electric state in the FC, which in turn affects the electrochemical reaction rate of the catalyst layer,thereby significantly affecting its transient performance(TSP). The pore characteristics and anisotropy of the porous layer are the key factors affecting its heat and mass transport capacity. Fully understanding its influence on the FC-TSP is of great significance for optimizing the load response of the vehicle-mounted FC power source. To this end, comprehensively considering the dynamic heat exchange between FC and the external environment, the spatial dynamic distribution of physical properties such as water, heat and electricity, as well as the multi-phase time-varying transformation relationship of gas, liquid and dissolved phase, the multi-phase 3D transient mass and heat transfer numerical model of FC was established to analyse the influence of heterogeneous properties of porous layer on the dynamic process. Further, the dynamic load was simulated with a step change of the current density, and the voltage of the FC, the water content and temperature of the membrane, and the oxygen concentration at the microporous layer | catalyst layer interface were analysed. The results show that the pore size and distribution and anisotropy of the porous layer have obvious effects on the TSP of the FC. In addition, the influence of different thermal conditions on the distribution of internal physical quantities of FC is more significant than that of TSP.

Key words: proton exchange membrane fuel cell, transient performance, porous layer, pore characteristics, anisotropy, non-isothermal