ABSTRACT Gas purging is a critical operation in low‐temperature PEM fuel cells (PEMFC) for removing the accumulated liquid water, preventing freezing after shutdown, and maintaining the cell's durability. In this work, a high‐fidelity workflow based on the volume‐of‐fluid (VOF) method is presented for simulating shutdown purging in PEMFC's with parallel channels. The initialization of liquid water is derived from PEMFC multiphysics simulations, complemented with experimental assumptions of corner attachment and droplet sizes forming on the surface of the gas diffusion layer (GDL). The workflow is tested on the purging of a cathode flow field after shutdown. Parametric studies were performed varying temperature, initial water accumulation scenarios, droplet size, and purging pressure drop. In all cases, a quasi‐steady state was reached in which residual water persisted in the flow field, even when the purging time was extended. Liquid water preferentially accumulated in the central channels and at outlet edges, where sharp edge pinning caused slug retention and even complete channel blockage. These results underline two key design limitations of parallel flow fields: maldistribution and outlet pinning. Purging at higher temperatures, closer to the operating temperatures, can reduce the purging time, although it does not improve the amount of remaining water. A sweeping effect has been identified as a positive purging mechanism, in which nearby droplets coalesce into a bigger slug that travels downstream, flushing smaller droplets. Increasing the pressure drop initially improves water removal by up to 10%, but excessive values lead to flow maldistribution and backflow in the central channels, limiting water removal performance. The proposed workflow successfully captures the underlying flow and water‐removal dynamics and offers a foundation for optimizing purge strategies and refining flow field designs.
Sanchez‐Gamero et al. (Fri,) studied this question.