Liquid water transport in gas flow channels of PEMFCs: A review on numerical simulations and visualization experiments

Proper water management in gas flow channels of a proton exchange membrane fuel cell (PEMFC) necessitates a comprehensive understanding of liquid water generation and motion, which are strongly related to droplet dynamics and flow patterns. Based on existing literature on numerical simulations using Volume of Fluid (VOF) method and Lattice Boltzmann method (LBM), this review identifies and analyzes the main factors in detail that affect the droplet dynamics including surface wettability, initial states of liquid water, geometrical structures of channels, and operating conditions. In addition, visualization experiments can effectively compensate for numerical simulations restricted by the limitations of length and time scale. This review focuses on optical photography, which is currently considered as the most convenient and low-cost method and discusses experimental apparatuses, qualitative flow pattern maps, and quantitative information. Finally, strategies for liquid water removal from gas flow channels are extracted to further enhance the performance of low-temperature PEMFCs.