| Summary: | 碩士 === 國立臺灣科技大學 === 機械工程系 === 96 === This experimental and fabrication investigation aims to develop and manufacture a high-efficiency composite heat pipe incorporated with the thermal module for the thermal management of advanced computers. The fundamental concept is taking advantage of both the high permeability of grooved wick and the strong capillary force of sintered wick. In this study, the sintered and grooved wicks are combined together to form a composite wick structure in enforcing the maximum heat-transfer capability for this micro heat pipe. At first, an appropriate set of processing parameters are determined from the theoretical analysis on capillary radius, porosity, permeability, and the amount of working mediums for this heat pipe. Then, the manufacture facility, process procedure, and performance test system are set up to perform a parametric study on the influences of sintered-wick length, heat-pipe length, and inclined angle.
To serve as the comparison foundation, the performance differences between the sintered and the grooved wick structures are obtained on this test platform. It is found that gravity has little impact on the sintered heat pipe while a strong downgrade is observed for an increasing heat pipe length. Also, due to the weak capillary force, the grooved wick structure can not function normally at a 20° inclination angle; however, a 50% performance enhancement compared to sintered wick is observed under horizontal position due to the high permeability.
Regarding the composite-wick heat pipe, it is demonstrated that the maximum heat transfer rate varies significantly with the length of sintered wick under both positive and negative inclination angles. Clearly, the shorter the sintered wick is, the higher the permeability and the weaker the capillary force will be. Thus, gravity has significant influences on maximum heat transfer rate, which can be twice as much as that of the sintered heat pipe under level test. In the other end, the longer the sintered wick is, the lower the permeability and the higher the capillary force will be. Nevertheless, the maximum heat transfer rate still can be 60% times as much as that of the sintered heat pipe at the worst case. In summary, the performance of this composite heat pipe is superior to both of the sintered-wick and grooved-wick heat pipe. Moreover, to meet the specified need for different applications, it is possible for engineers to reinforce the permeability or the capillary force to obtain a better heat pipe by adjusting the length of sintered wick
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