| Summary: | 碩士 === 國立成功大學 === 航空太空工程學系碩博士班 === 98 === Water management in a PEM fuel cell has been a critical challenging issue, especially in the porous electrodes and reactant flow channels. As the partial pressure of water vapor exceeds the saturation pressure of water or the operating temperature of a PEM fuel cell is lower than the dew point of water vapor, liquid water may form to occupy the pore of gas diffusion layer and block the gas transport path. Consequently, the limiting current density is lowered, resulted from the mass-transport-limitation. Therefore, this study presents a numerical investigation of air-water flow in single serpentine channel on the cathode of a PEM fuel cell by using the commercial computational fluid dynamics (CFD-ACE+). The volume of fluid (VOF) model is adopted to trace the shape if the water droplet. The dynamic behavior of the droplet is simulated in flow channel of fuel cell at different reactant flow velocities. In addition, the effect of surface properties of flow channel was examined under various hydrophilic/hydrophobic characteristics, such as the contact angle of droplet. In this study a single-cell PEMFC with a serpentine gas flow channel is made as the model for experiment. The base conditions are : The air velocity is fixed at 2 m/s; the gravity is in negative y direction; the contact angle is 70 degrees. Results show the contact angle is the most important factor for liquid droplet removal.
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