CFD Optimization of Multi-Pass Serpentine Flow Distributors for PEM Fuel Cells

Polymer electrolyte membrane (PEM) fuel cells represent one of the most promising solutions for decarbonizing powertrain technologies, as they can be employed as carbon-free electrical power source. However, performance degradation during their operating lifetime - caused among other factors by non-uniform reactant distribution and improper membrane humidification, which may lead to the formation of local hot spots - remains a significant challenge. Computational fluid dynamics (CFD) tools represent an effective approach for investigating the transport of oxygen and hydrogen within the cell and for optimizing the geometry of PEM fuel cell flow distributors. Thus, they can be exploited in order to improve the uniformity of current density and temperature distributions over the cell active area. In this work, a serpentine flow field PEM fuel cell is considered as test case. The distributor consists of a multi-pass serpentine flow-field composed of repeated sets of five parallel channels interconnected by transverse manifolds. First, an open-source simulation library based on the OpenFOAM framework is validated against the cell polarization curve experimental data. Subsequently, a parametric analysis of the most relevant geometric parameters characterizing the flow distributor, such as channel width, channel height and manifold geometry, is carried out to assess their influence on the overall cell performance, reactants and current density distribution. The results demonstrate that appropriate optimization of the manifold geometry leads to a more uniform flow field within adjacent channels in both the anodic and cathodic distributors, resulting in an overall increase of reactants and temperature homogeneity distribution.