Evaluation of sub-rib convection in PEM fuel cell flow fields with different geometrical characteristics

The flow field configuration in a bipolar plate represents an important factor for performance enhancement of Proton Exchange Membrane Fuel Cells (PEMFC). The sub-rib convection of reactant gases and pressure drop along the gas channel, which are affecting the oxygen supply at the catalyst electrode active area and the electrochemical reaction rate at cathode, are influenced by some geometrical flow field factors like channel/rib width and channel cross sectional area. In this study, the overall under-rib convection along the entire active area is quantified in the form of Peclet number for seven single serpentine - two channels flow field models, differing by their geometrical dimensions: channel width, height and length and distance between channels (rib width). The Finite Element Method (FEM) based Comsol Multiphysics software (vers. 5.2) is used here for numerically computing the convective type velocity field distribution along gas diffusion layer (GDL) and local current density distribution at oxygen reaction site boundary for all the models investigated. Pressure drop along the channel length, oxygen molar concentration and oxygen diffusive flux at the cathode boundary is also evaluated numerically.