Investigation of the Effect of Heat Leak in Loop Heat Pipes with Flat Evaporator
Date Issued
2007
Date
2007
Author(s)
Lai, Shih-Ru
DOI
zh-TW
Abstract
Loop heat pipes (LHPs), which are generally and widely used with cylindrical evaporators, have a great potential for applications of spacecrafts and electronic cooling due to the advantages of high transfer capacity, low thermal resistance and long transport distances.
However, the cylindrical evaporators of loop heat pipes cannot work on a flat thermo-contact surface without saddle. The saddle not only creates an extra thermal resistance but also makes evaporators less isothermal. To avoid the above disadvantages, we adopt the flat evaporators of loop heat pipes.
According to the literature, however, the heat leak problem is more serious in the flat evaporators than the cylindrical evaporators. This problem also makes the thermal resistance of flat evaporators higher. Hence this study tries to solve the difficulties and provides two solutions. The first method is to increase the thermal resistance of the wick by raising the wick thickness. The second method, we design a double-decked wick, which is composed of the primary wick sintered with metal powder and the secondary wick made of the low thermal conductivity polymer. The material wick generates higher capillary forces and the polymer has lower thermal conductivity. Such design can ease the heat leak problem.
The results show that both methods can ease heat leak problem. When primary wick thickness of double-decked wick is 4 mm, the temperature of the evaporators is less than 100oC and the sink temperature is at 30oC. The maximum heat capacity increases from 40W to 180W. In addition, the thermal resistance decreases from 0.69 K/W to 0.38 K/W
Subjects
熱管
迴路式熱管
平板蒸發器
熱洩漏
heat pipe
loop heat pipe (LHP)
flat evaporator
heat leak
Type
thesis
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