CFD simulation of water droplet adhesion on the GDL of a low temperature PEM FC in air cross-flow conditions

Abstract

Water management is a critical challenge in low temperature (LT) Proton Exchange Membrane Fuel Cells (PEM FC); condensed liquid appears mainly at the cathode side, where water from the reduction reaction is generated. Differences in concentration may result in the transfer of water to the anode side across the membrane electrode assembly (MEA). Excessive liquid can negatively affect fuel cell performance, causing low efficiency and instability. This occurs due to water movement through porous layers and channels that are the essential pathways for the reactant gas to reach the MEA. However, water is necessary in the PEM FC for enhancing ion conductivity of the membrane. The present study can contribute to the optimization of LT PEM FCs by analysing the water behaviour under flow conditions. The widely used Volume Of Fluid (VOF) method is adopted for simulating multiphase flow. CFD simulation of droplet adhesion on the gas diffusion layer (GDL) is performed to describe the interaction between water and gas flow. Deformation and oscillations of droplets with diameters in the 0.3-1.0 mm range are investigated by considering airflow rates up to 15.0 m/s. CFD analysis is validated by optical data from digital imaging with high spatial (up to 5.8 μm/pixel) and temporal (up to 1.0 ms) resolution.