Effect of Channel Width on Flow Characteristics in PEM Fuel Cell Anode and Cathode Flow Fields – a CFD Study

The performance of Proton Exchange Membrane Fuel Cells (PEMFCs) is highly influenced by the geometric design of the flow field channels that deliver reactants and remove by products. In this study, the effect of channel width in anode and cathode flow fields with a four-channel multiple-pass short serpentine (FCMPSS) configuration was investigated using Computational Fluid Dynamics (CFD) simulations in ANSYS Fluent under laminar flow conditions to identify optimal width combinations. The analysis includes three anode and cathode width combinations for a fixed channel depth of 1.25 mm and cell active area of 112 cm2. The tested combinations are 0.8 mm, 1 mm, and 1.2 mm for the anode, and 0.6 mm, 0.8 mm, and 1 mm for the cathode, respectively. Flow rates are derived for the target current density of 0.7 A/cm2. This study focuses on flow characteristics by excluding electrochemical reactions to understand the flow behaviour before incorporating electrochemical models, and was validated through a grid independence study and Reynolds number analysis. Simulation results showed that narrower channels significantly increase pressure drop and reactant velocity, thereby enhancing reactant convection and water removal. However, they can also increase reactant pumping power and the risk of membrane dehydration. Conversely, wider channels reduce pressure drop and velocity, thereby lowering pumping energy losses, but risk poor reactant distribution and local flooding. The configuration with 1.0 mm anode and 0.8 mm cathode widths achieved the most balanced performance, exhibiting moderate pressure drops of approximately 2044 Pa and 8822 Pa, and corresponding velocities of 4.76 m/s and 4.17 m/s, which support efficient transport phenomena while minimising energy losses.