3D CFD Modelling of Low Temperature Pemfcs

Abstract

Computational fluid dynamics (CFD) is becoming more and more an essential tool to gain deeper insight into the physics of proton exchange membrane fuel cells (PEMFCs). The goal is to achieve an optimized fuel cell design as a further step towards the commercialization of PEMFCs as an alternative to common automotive fuel engines. Nowadays a validated CFD model provides one means of improving the performance of fuel cells. The open-source code of Beale et al. [1] is a generic framework for simulating different types of fuel cells. The authors extended it to a full three-dimensional model using additional model equations and modified source terms. According to the integrated cell concept used in the open-source code three additional so-called 'child' meshes are introduced to account for charge transport and water transport in the polymer electrolyte membrane. The parameters of the Butler-Volmer equation (Figure 1, top), describing the electrochemical kinetics of the fuel cell, are used as fitting parameters in most existing literature. In this work the authors use a set of experimentally determined parameters in order to reduce the number of uncertain/fitting parameters.The method used to determine this set of parameters is electrochemical impedance spectroscopy whereby the data is analysed using the distribution function of relaxation times [2]. This method helps to separate the polarization processes contributing to the overall polarization loss in a clearer way. The numerical results of the model described above are compared to polarization curves measured by experiments. The results show good agreement (Figure 1, bottom) for two different humidifications (40% RH and 70% RH) in the activation and ohmic regions.