Single serpentine flow fields design and sub-rib convection analysis for a PEM fuel cell

Abstract

In a polymer electrolyte membrane fuel cell (PEMFC), transport of reactant gases through a bypass convection mechanism established between two adjacent channels along the gas diffusion layer (GDL) under the serpentine type flow field of a bipolar plate can enhance the fuel cell performance by reducing the power losses. In this paper, three different serpentine type flow field models for bipolar plates of a PEM fuel cell unit have been designed, with different channel width/rib width ratios of 1, 1.05 and 1.2, and different pressure loses have been evaluated. An analytical model for bypass sub-rib convection, based on two adjacent flow channels and a serpentine in contact with a GDL layer was used here. This model established the influence of bypass convection in the form of Peclet number Pe for the flow field models, by modifying the GDL thickness t (mm) and active channel length L (mm). The optimal combination of thickness t, porosity ε and permeability k for a series of commercial GDL materials from the perspective of sub-rib convection was established for Sigracet^TM GDL 35 BC, with highest Pe number modified along the channel.