| Summary: | 碩士 === 國立臺北科技大學 === 冷凍與低溫科技研究所 === 92 === In this study, the heat transfer performance of sintered copper heat pipes by the power scanning method is reported. By measuring the temperature variations along a heat pipe, the maximum axial heat transfer rate and its operating temperature, as well as its axial thermal resistance and the radial thermal resistance in different orientations and condensation temperatures, could be obtained.
This experiment has proved that the "Figure of Merits" (M) is proportional to the maximum heat transfer rate, and the evaporator will dry out after the heat pipe reaches the maximum heat transfer rate. The maximum heat transfer rate in the gravity-assisted orientation is much larger than in the antigravity orientation. The maximum heat transfer rate measured in the horizontal orientation lies in between the values of the gravity-assisted and antigravity orientations, but is close to that of the anti-gravity orientation. The reason is that the liquid and vapor phases are separated in the horizontal orientation, such that the evaporation and the condensation areas are less than those in the other orientations. The experiments also proved that the capillary force of heat pipes is larger than the gravity force. Nevertheless, in the anti-gravity orientation, since the capillary force has to overcome the gravity, liquid pressure loss, and vapor pressure loss, the heat transfer rate of the pipes is usually compromised. In summary, for optimum heat transfer rate, a gravity-assisted orientation is recommended in setting-up a heat pipe.
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