Electromechanical numerical simulation of contact resistance between BPP and GDL in a PEM fuel cell with TLM method

High efficiency, portability and near zero emissions have made fuel cell a very promising solution for generating electricity. Proton exchange membrane fuel cell is one of the most complete and important fuel cell technologies owing to its low operating temperature, quick start-up and high efficiency. The contact resistance between the bipolar plates and the gas diffusion layer plays crucial role in the power loss in a proton exchange membrane fuel cell. By optimizing the design, contact resistance can be minimized, resulting in improved fuel cell performance. Therefore, in this paper, the study of the mechanical-electrical behavior of the contact surface, pressure distribution and contact resistance between the bipolar plates and the gas diffusion layer has been on the agenda. Since the electric current and mechanical pressure are simultaneously applied to the fuel cell assembly, a mechanical-electrical coupled model should be developed to study its contact behavior. For this purpose, a numerical electromechanical model has been developed using the COMSOL Multiphysics commercial software. The transmission length method (TLM) [۱] has been employed to measure the contact resistance under mechanical compression and the Cooper-Mikic-Yovanovich uneven surface model ۲]has been used at the junction of the bipolar plates and the gas diffusion layer for pairing of the contacts. The effect of different parameters on the contact resistance between the bipolar plates and the gas diffusion layer has been studied. It was found that the contact resistance increases by increasing parameters such as the microhardness of the gas diffusion layer, contact surface roughness height, contact surface roughness slope, rib width, channel height and rib corner radius and decreases by increasing the gas diffusion layer thickness and contact pressure, while changing the length of the gas diffusion layer has no effect on the performance of the contact resistance. According to the results, the high accuracy and the superior numerical efficiency make the TLM a good alternative to previous conventional methods to predict the contact resistance.Figures ۱ and ۲ show the schematic of the electrical circuit and calculation of the contact resistance in the transmission length method, respectively. The geometric characteristics and boundary conditions of the numerical model is given in figure ۴, and the validation of the modeling results with the experimental data of Oualid et al. [۳] is presented in figure ۳.