Two-phase flow and transport in the air cathode of proton exchange membrane fuel cells |
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| Affiliation: | 1. Electrochemical Engine Center, Department of Mechanical and Nuclear Engineering, Pennsylvania State University, University Park, PA 16802, USA;2. Engineering Sciences Center, Sandia National Laboratories, Albuquerque, NM 87185-0834, USA;1. Department of Chemical and Biological Engineering, Montana State University, Bozeman, MT 59718, USA;2. Department of Chemical and Biological Engineering, University of Saskatchewan, Saskatoon, SK S7N 5A9, Canada;1. School of Chemical Engineering and Advanced Materials, Merz Court, Newcastle University, Newcastle upon Tyne NE1 7RU, UK;2. School of Chemical Engineering, Inner Mongolia University of Technology, Hohhot 010051, China;1. State Key Laboratory of Engines, Tianjin University, 135 Yaguan Rd, Tianjin 300350, China;2. Renewable Energy Resources Laboratory (RERL), Department of Mechanical and Aerospace Engineering, University of California, Irvine, CA 92697-3975, United States |
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| Abstract: | Two-phase flow and transport of reactants and products in the air cathode of proton exchange membrane (PEM) fuel cells is studied analytically and numerically. Single- and two-phase regimes of water distribution and transport are classified by a threshold current density corresponding to first appearance of liquid water at the membrane/cathode interface. When the cell operates above the threshold current density, liquid water appears and a two-phase zone forms within the porous cathode. A two-phase, multicomponent mixture model in conjunction with a finite-volume-based computational fluid dynamics (CFD) technique is applied to simulate the cathode operation in this regime. The model is able to handle the situation where a single-phase region co-exists with a two-phase zone in the air cathode. For the first time, the polarization curve as well as water and oxygen concentration distributions encompassing both single- and two-phase regimes of the air cathode are presented. Capillary action is found to be the dominant mechanism for water transport inside the two-phase zone of the hydrophilic structure. The liquid water saturation within the cathode is predicted to reach 6.3% at 1.4 A cm−2 for dry inlet air. |
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