Transient 2D numerical study of water transport in porous media of a fuel cell using VOF model

To improve the effectiveness and durability of proton exchange membrane and alkaline exchange membrane fuel cells, understanding water transport in porous media is crucial. The standard porous media consist of three layers: the gas diffusion layer, microporous layer, and catalyst layer. Water plays a vital role in maintaining membrane hydration; however, excessive accumulation leads to flooding and performance loss. This study numerically investigates the effects of mixed wettability, pore size, operating temperature, and polytetrafluoroethylene (PTFE) loading on water transport within porous media. The model captures water breakthrough and capillary fingering phenomena, revealing that lower PTFE loading increases water saturation. However, the local microstructure of the porous media significantly influences overall water distribution, particularly near localized water generation points. Furthermore, the results indicate that for a water mass flow rate of 0.41 g/s, the pressure required to permeate through the microporous layer exceeds 600 kPa, which is physically unrealistic for a practical fuel cell. By strategically engineering the porous media microstructure, such as optimizing pore distributions and PTFE loading, water transport can be enhanced, reducing water accumulation in the catalyst layer and gas diffusion layer. These findings provide valuable insights for fuel cell design and performance optimization. • VOF model using an actual GDL microstructure for water permeation analysis. • Effects of temperature, velocity, porosity, and wettability on water permeation. • Surface contact angle identified as the key factor controlling water transport. • Extremely high capillary pressure is required for water permeation through the MPL.