Numerical Investigation on Two-Phase Flow Pressure Drop in Cathode Channels of Proton Exchange Membrane Fuel Cells

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Water management remains a critical challenge in proton exchange membrane (PEM) fuel cells, particularly concerning flooding under high-current density and prolonged operation. Dynamic water distribution directly affects gas phase transport, encompassing convection within gas channels (GCs) and diffusion through porous electrodes. The fluctuation of pressure drop has been highlighted in previous studies [1-3], which is more frequent when compared with that when only single-phase flow in the channel is considered. A reasonable cathode channel pressure drop can benefit fuel cell performance [1] and energy efficiency [4]. Although pressure drop correlations have been conducted experimentally and numerically [5], the pressure drop prediction still needs to be improved, for example, involving the liquid transport from gas diffusion layers (GDLs) [6]. In this study, two-phase flow simulations in an assembled GC and fibrous GDL are conducted by the volume of fluid method in OpenFOAM. To utilize the fibrous GDL structures to mimic the natural breakthrough water, different GDLs are stochastically reconstructed using straight- and curved- cylinders (regarded as carbon fibers) and keeping the same bulk porosity and fiber diameter, as shown in Figure 1. The GC pressure drop is studied in local and total regions in different scenarios, e.g, different GDL structures (see Figure 1(c)), different surface wettability, and different air flow rates. Preliminary results show that the pressure drop does not exhibit a direct correlation with the liquid amount present in the GC, suggesting a multifaceted relationship that extends beyond mere liquid content, as shown in Figure 2. Therefore, it is imperative to explore additional factors that may influence this critical parameter. Figure 3 displays the spatial and temporal distribution of pressure and water cross-section area of 23 cross-section along the GC length direction in 13.5 ms in Case A and B. The breakthrough types in the GDL/GC interface and drainage flow types in GCs are found to relate more to the pressure drop. In future work, we aim to explore all the above scenarios to gain deeper insights into their impact on pressure drop behavior and ultimately enhance our understanding of the complex interactions governing two-phase flow in PEM fuel cell systems.References Li, P. Pei, Z. Wu, H. Xu, D. Chen and S. Huang, Applied Energy, 190, 713 (2017). Liu, L. Guo, R. Zhang, L. Chen and W.-Q. Tao, Applied Energy, 302, 117625 (2021). Zhang, S. Liu, Z. Wang, R. Li and Q. Zhang, International Journal of Hydrogen Energy, 47, 17713 (2022). S. Ijaodola, Z. El- Hassan, E. Ogungbemi, F. N. Khatib, T. Wilberforce, J. Thompson and A. G. Olabi, Energy, 179, 246 (2019). Li, H. Zhou, C. Li, Z. Liu, P. Zhang and C. Lu, Experimental Thermal and Fluid Science, 155, 111198 (2024). Mortazavi and K. Tajiri, Renewable and Sustainable Energy Reviews, 45, 296 (2015). Figure 1