The effect of relative humidity of the cathode on the performance and the uniformity of PEM fuel cells |
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Authors: | Dong Hyup Jeon Kwang Nam KimSeung Man Baek Jin Hyun Nam |
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Affiliation: | a Core Technology Lab., Corporate R & D Center, Samsung SDI Co. Ltd., 428-5, Gongse-dong, Giheung-gu, Yongin-si, Gyeonggi-do 446-577, Republic of Korea b School of Mechanical and Aerospace Engineering, Seoul National University, Seoul 151-742, Republic of Korea c School of Mechanical and Automotive Engineering, Daegu University, Gyungsan 712-714, Republic of Korea |
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Abstract: | The effect of relative humidity of the cathode (RHC) on proton exchange membrane (PEM) fuel cells has been studied focusing on automotive operation. Computational fluid dynamics (CFD) simulations were performed on a 300-cm2 serpentine flow-field configuration at various RHC levels. The dependency of current density, membrane water contents, net water flux on the performance and the uniformity was investigated. The uniformity of current density and temperature was evaluated by employing standard deviation. The water balance inside a fuel cell was examined by describing electro-osmotic drag and back diffusion. It was concluded that the RHC has strong effect on the cell performance and uniformity. The dry RHC showed low cell voltage and non-uniform distributions of current density and temperature, whereas high RHC presented increased cell performance and uniform distributions of current density and temperature with well-hydrated membrane electrode assembly (MEA). Also the local current density distribution was strongly dependent on the local membrane water contents distribution that has complex phenomena of water transport. The elimination of external humidifier is desirable for the automotive operation, but it could degrade cell performance and durability due to dehydration of the MEA. Therefore a proper humidification of the reactant is necessary. |
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Keywords: | PEM fuel cells CFD modeling Relative humidity Uniformity Water balance |
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