Thin porous layers are seen in many applications such as hydrogen fuel cells and hygiene products, in which air-water flow is of great interest. Navier-Stokes-based direct simulations are very computationally expensive, and even prohibitive for low capillary number flow such as water flooding in hydrogen fuel cells. Alternatively, the pore-network modeling needs much less computational resources, while retaining essentials of pore structure information. In this work, a dynamic pore-network model of air-water flow with phase change has been developed. We focused on water drainage processes through thin porous layers. Three test cases were conducted, namely, air-water flow through a thin porous layer, air-water flow through a bilayer of fine and coarse thin porous layers, and water flooding in the gas diffusion layer of a polymer electrolyte fuel cell with phase change between water and water vapor. We aim to demonstrate the application of dynamic pore-network modeling in thin porous media studies. With the help of the case studies, we particularly discussed the challenge of modeling thin porous media at the average scale, and highlighted the role of phase change in removing liquid water in the cathode gas diffusion layer.
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