Accuracy estimation of a CFD multiphysics approach to study a mixed parallel and serpentine flow channels PEM fuel cell

Abstract

Abstract This study presents a comprehensive analysis of a 50 cm2 fuel cell with mixed parallel and serpentine flow channels using Computational Fluid Dynamics modelling. Through rigorous validation against experimental measurements, the numerical model ensures accuracy in capturing convective and diffusive fluid flows, thermodynamic, and electrochemical phenomena and their mutual interaction. The study discusses a systematic procedure for achieving model convergence and identifies key parameters influencing the fitting of numerical polarization curves with experimental data. Operating within a temperature of 333 K, at atmospheric pressure, with a relative humidity of 100% for both the anode and cathode, the model offers crucial insights for advancing our understanding of fuel cell operation and guiding the development of more efficient and reliable technologies. In the activation region, reference exchange current densities and charge transfer coefficients were proved to play a significant role in reproducing the PEM fuel cell behaviour. Increasing the exchange current densities raises the voltage output in the activation polarization region while charge transfer coefficients affect the slope of the curve. In the ohmic region, a proton conduction coefficient of 1.84 and a contact resistance between gas diffusion layers and bipolar plates equal to 4.03e-7 Ω·m2 were used to fit the experimental polarization curve. After the tuning process, the numerical curve closely matches the experimental one with a maximum relative error of 2.40% and an R2 value of 0.9848. Moreover, a detailed analysis of the internal distribution of key variables was conducted for a specific point on the polarization curve (0.25 A/cm2). This analysis provided significant insights into the complex interplay of fluid dynamics, heat transfer, and electrochemical processes. Specifically, it was observed how the flow distribution, pressure drop, and reactant concentrations within the fuel cell channels and gas diffusion layers affect overall performance, highlighting the crucial role of convection and diffusion in reactant transport and the importance of managing heat for optimal cell operation.