Impact of different descriptions for diffusion, heat transfer, and capillary pressure on a physics-based proton-exchange membrane fuel cell model

A physics-based, two-phase, and non-isothermal proton-exchange membrane fuel cell model is developed and used to evaluate the impact of three common modeling assumptions concerning mass and heat transport in a single-cell system. Firstly, using Fick's law to describe the diffusive transport caused significant differences in the concentration profiles when compared to the Stefan-Maxwell equation, resulting in considerable deviations in the polarization curve. Moreover, the description of thermal effects is found to be crucial to obtaining accurate water molar fraction profiles for the cathode, even when heat removal is effective. Finally, while the impact related to the capillary pressure description in the polarization curve is insignificant when ohmic losses dominate, as they considerably affect the liquid water and oxygen profiles, they may be crucial to obtain precise values at high current densities when water removal is less efficient. These results should provide valuable insights for the development of better models.