The Impact of Wick Wettability on Heat Transfer Performance of Loop Heat Pipe
Date Issued
2012
Date
2012
Author(s)
Chun-Yao, Chan
Abstract
Loop heat pipe (LHP) is a passive two phase heat transfer device, which has ability to transport heat in long-distance, low thermal resistance, and high heat transfer capacity compared with a traditional heat pipe. During thermal transfer process, the wettability of the wick in the evaporator of LHP has impacts on capillary force, disjoining pressure and evaporative thin film. Then, it could affect the heat transfer performance of LHP significantly. However, the related research about the effect of wettability on LHP’s evaporation still lacks. Therefore, the purpose of this article is to discuss the impact of wick wettability on heat transfer performance of loop heat pipe.
In this study, the material of wick was copper, and the working fluid was water. The methods to change wick’s wettability were the oxidation and the layer-by-layer thin film coating. In the experiment results of monoporous wick, as the wick’s wettability increased, the critical heat load reduced. While the wick’s contact angle was more than 90°the working fluid did not penetrate into the wick. That caused that loop heat pipe could not start.
The impact of wick wettability on film evaporation also varies with pore size. Therefore, in this study, the biporous wick was manufactured by using Na2CO3 powder as pore former which has 105~125μm in diameter. The impact of wettability in biporous wick on the heat transfer performance in LHP was discussed. The biporous experiment result indicated that the wick had a good wettability which leaded a lower evaporator wall temperature as well as a lower total thermal resistance.
Subjects
Loop heat pipe
wick wettability
biporous wick
heat leakage
Type
thesis
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