刘易斯因子及其对板式蒸发冷却器性能的影响

Lewis Factor and Its Effect on Performance of Plate Evaporative Cooler

对热湿交换过程进行质量与能量衡算，建立逆流板式蒸发冷却器传递过程的数学模型．分析了刘易斯数、刘易斯关系式与刘易斯因子之间的区别与联系；计算得到了蒸发式冷却器空气与水热湿交换过程的刘易斯因子取值范围大约在0．75-0．95之间，其受水温和空气湿球温度影响较大．分析了刘易斯因子取值在0．5～1．5范围内对冷却器流体出口状态、热量交换与冷却效率的影响，以及应用刘易斯关系式所导致的误差，结果表明应用刘易斯关系式导致的冷却效率相对误差小于2％，工程应用该简化是合理的．

This paper presents the differential equation group of heat and mass transfer process in the plate evaporative coolers theoretically. The difference and relation among Lewis number （Le）, Lewis relation and Lewis factor （Lef） discussed. Lewis factor of heat and mass transfer from water to air is influenced by water temperature and air wet bulb temperature greatly and the value range of Lef is from 0.75 to 0.95. The influences on the performance prediction, such as outlet temperatures for hot water and moist air,heat transfer rate and cooling efficiency, were analyzed in the Lewis factor range of 0.5 1.5. The deviation resulted from applying Lewis relation is less than 2%. Applying Lewis relation is reasonable to simplify the evaporative cooler mathematical model.