PEM fuel cell performance and its two-phase mass transport

A two-phase flow model for a proton exchange membrane (PEM) fuel cell is developed. The model is based on the mixture flow model and the unified approach is used. Instead of using a separate model for the catalyst layer, the catalyst layers are now included in the respective unified domains for the cathode and anode, thus continuity boundary conditions at the interface between the catalyst layer (CL) and the gas diffuser layer (GDL) are no longer needed. The model couples the flows, species, electrical potential, and current density distributions in the cathode and anode fluid channels, gas diffusers, catalyst layers and membrane respectively. Furthermore, the two-phase flow model is also used in the anode side, and the momentum transfer between the liquid and gas phases due to phase change is taken into consideration. Experiments have been conducted to study the performances of a PEM fuel cell and the results are used to improve and validate our model. The modeling results of polarization curves compared well with the experimental data. The model is used to study the influences of fuel cell operating temperature, operating pressure and humidification temperature on the oxygen, vapor and liquid water transports, as well as fuel cell performances.