一次侧凝结对间接蒸发冷却换热性能的影响

Effect of condensation area in primary air channels on heat transfer capacity of indirect evaporative cooling

在夏季高温高湿的环境下,使用间接蒸发冷却器对空调新风冷却时,由于新风露点温度较高,在一次风通道壁面上容易产生凝结水和潜热换热。为此,开发了考虑凝结换热的二维板式叉流间接蒸发冷却传热传质分析解数学模型,采用有限差分法和Matlab程序对模型计算求解,提出在非凝结、全部凝结和部分凝结3种凝结状态下与凝结面积比的判断和求解方法。该模型与实验呈现较好的吻合性,最大误差为8.6%。通过凝结面积比对间接蒸发冷却湿球效率、除湿率、潜热换热量、显热换热量、放大系数的影响分析,表明凝结面积比与潜热换热量、总换热量、放大系数和除湿率成正相关,对显热换热量和湿球效率成负相关。在全部凝结状态下,放大系数变化范围3.7~4.9,其中潜热换热量占总换热量的73%~79%,潜热换热加强了节能效果。

In the high temperature and humidity environment in summer,the dew point temperature of fresh air is fairly high.When indirect evaporative cooler is applied to cool fresh air in air conditioning system,condensation easily occurs on the wall of primary air channels.Thus a two-dimensional mathematical model is developed for heat and mass transfer of a plate cross-flow indirect evaporative cooler based on condensation area ratio(σ).The model is solved by the finite difference method and MATLAB program.A method for judging condensation state and solving condensation area ratio is proposed,including three state of non-condensation(σ=0),total condensation(σ=1)and partial condensation(0<σ<1).The computational result is in good agreement with the experimental result,and the maximum error is 8.6%.The effect of condensation area ratio on wet-bulb efficiency,dehumidification rate,latent heat transfer,sensible heat transfer and enlargement coefficient of indirect evaporative cooling is investigated.The result shows that condensation area ratio is positively correlated with latent heat transfer,total heat transfer,enlargement coefficient and dehumidification rate,and negatively correlated with sensible heat transfer and wet-bulb efficiency.