工质对重力热管壁温与传热特性的影响

Effect of Working Fluids on Wall Temperature and Heat Transfer Characteristics of Gravity Heat Pipe

实验中以水、乙醇和FC-72为工质,对重力热管的传热性能、温度均匀性以及温度波动进行了分析。结果显示,当加热功率为20 W时,以水为工质可导致蒸发段壁面的温度波动达3.0℃,以乙醇为工质时,壁面温度波动幅值显著降低,而当以FC-72为工质时,其壁面温度波动很小,稳定性良好。以乙醇和水为工质时,蒸发段温度均匀性与韦伯数We大小有关,We小于1时,温度均匀性随加热功率的增加而升高,We大于1时,温度均匀性随加热功率的增加整体呈降低趋势。同时工质物性对蒸发段和冷凝段热阻的影响具有差异性,以水为工质时蒸发段热阻占比为55%∼80%。而以乙醇和FC-72为工质时冷凝段热阻在总热阻中所占比例较大。

Water, ethanol and FC-72 are used as the working fluids in gravity heat pipe, the heat transfer performance, temperature uniformity and temperature fluctuation were analyzed. The results show that when the heating power is 20 W, the fluctuation of the evaporation section wall temperature can reach 3.0℃ when water is used as the working fluid. As ethanol is used, the fluctuation amplitude decreases significantly. However, as FC-72 is used, the wall temperature fluctuation is small and the stability is good. The temperature uniformity of evaporation section is related to Weber number We. When ethanol and water are used, for We.1, the temperature uniformity improved with the increasing of heating power. When We>1, the temperature uniformity decreased with the increasing of heating power. At the same time, the physical properties of the working fluid have different effects on the thermal resistance of the evaporation section and the condensation section.When water is used as the working fluid, the thermal resistance of the evaporation section accounts for 55%~80% of total thermal resistance, higher than 50%. When ethanol and FC-72 are used as working fluids, the thermal resistance of the condensation section accounts for a large proportion of the total thermal resistance.