A numerical study on the effects of temperature and mass transfer in high temperature PEM fuel cells with ab-PBI membrane

Abstract

A two-dimensional, single-phase model is developed to study high temperature proton exchange membrane (HT-PEM) fuel cell with poly(2,5-benzimidazole) (ab-PBI) membrane. In this model, simulation region not only includes the cathode and anode, but also includes ab-PBI membrane; the continuity boundary condition at the interface between the catalyst layer (CL) and the gas diffusion layer (GDL) at each side of the cell is omitted by including the catalyst layers in the respective unified domains for the cathode and the anode. The flows, species, energy, current density are all coupled in the model. Experiments have been conducted to validate the proposed numerical simulations, and it is found that there is a good agreement between the modeling results and those obtained experimentally. By this simulation, not only the oxygen and water fraction distribution in the cathode, but also the temperature distribution and resistance distribution in the ab-PBI membrane are obtained, and the effects of the cell temperature, the porosity in the diffusion layer and its thickness on the current density are analyzed. The innovative researching results are that the temperature distribution is uneven in the ab-PBI membrane and its resistance is greatly affected by the operating temperature. Other results show that the increase of the cell temperature and the porosity in the diffusion layer, and the decrease of the diffusion layer thickness all improve the performance of HT-PEM fuel cells by promoting its internal mass transfer.