本文建立了直接甲醇燃料电池的两相、非等温模型.采用多孔介质中的经典多相流动模型来计算电池内与电化学反应相耦合的传质、传热问题;模型中考虑了水的汽化凝结过程和甲醇窜流对电池性能的影响.计算结果表明电池内温度分布不均匀,温度最高点出现在阴极催化层;阳极甲醇浓度分布不均匀是造成阳极催化层内局部反应速率不均匀分布的主要原因,而阴极催化层局部反应速率主要依赖于阴极过电势的分布;大的流场板开口比条件下电池整体均匀性较好,性能得到提高.
A two-phase non-isothermal mass transport model is presented in this paper. The heat and mass transfer across the membrane electrode assembly (MEA), coupled with the electrochemical reactions in the catalyst layers (CLs), are calculated based on the classical two-phase flow model in the porous media. The effect of methanol crossover on the cell performance and the non-equilibrium evaporation/condensation of water are considered in this model. The modeling results show that the distribution of temperature in the MEA is not uniform, and the highest temperature appears in the cathode CL. The non-uniform distributed methanol concentration leads to the non-uniform distributed methanol oxidization reaction (MOR) rate while the oxygen reduction reaction (ORR) rate mainly depends on the distribution of the local overpotential in the cathode CL. The increase in the open ratio of the flow field plate results in more uniform distribution of physical fields in the fuel cell and the cell performance is also improved with a larger open ratio.
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