The Modeling and Calculating of Heat Transfer in Proton Exchange Membrane Fuel Cell

Abstract: Proton exchange membrane fuel cell (PEMFC) has become one of the most important and popular research items in energy resource field due to its great advantages, such as high efficiency, no pollution, fast start-up, high power density and so on. Because the heat of the PEMFC is non-reversible and nearly 50% of the energy dissipation is heat energy. If there is ineffective thermal management, the temperature of the fuel cell will ascend endlessly, and then the membrane will dehydrate and shrink. Temperature distribution of PEMFC also has an important effect on the water management, heat transfer and mass transfer and it is regarded as the most important research direction. In this paper, computer simulation is used to analyze performance and temperature distribution rules of PEMFC and the simulation tool is the PEM module of computer fluid dynamics software Fluent.First, heat resource of PEMFC is analyzed that one part of heat is produced directly or indirectly by electrochemistry reaction and another part of heat is independent of electrochemistry reaction, and then illuminate the effect of temperature on the polarization in different polarization zone. Mathematic models used in the simulation work are presented.Then, the paper discusses the effects of some operating conditions on the cell's performance and temperature distribution in membrane. The results are as follows: The cell's performance improves by promoting the operating pressure, and at the same time the highest temperature increases and the temperature distribution in the membrane is worse because of the more heat energy created. With the stoichiometric flow ratio of cathode increasing, the fuel cell performance improves, especially during low stoichiometric flow ratio. The highest temperature and temperature difference in membrane decreases tinily. Inlet gas humidification greatly influences the fuel cell performance and temperature distribution. Generally, the cell's performance can be raised when raising the gas humidification; but due to the effect of concentration polarization at high current density, the performance of cell contrarily descends as cathode gas humidification is raised. The highest temperature and temperature difference in membrane both increase when raising the gas humidification of cathode or anode.At last, the effects of fuel cell temperature, humidified temperature of cathode and anode on cell's performance and temperature distribution are discussed. The results show that while the working temperature increasing, the humidification of membrane becomes badly and fuel cell performance decreases at lower current density, while the saturation in diffusion layer increases and the performance improves at higher current density. Humidification of membrane and fuel cell performance improves when the anode humidified temperature increases. While cathode full humidified, the cell's performance decreased when cathode humidified temperature increases. The highest temperature and temperature difference in membrane increased when one of the fuel cell temperature and humidified temperature of cathode and anode increases…
Key words: proton exchange membranes fuel cell; temperature; modeling; Fluent

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