| Summary: | 碩士 === 國立成功大學 === 工程科學系碩博士班 === 90 === The purpose of this investigation is to study experimentally the thermal performance of heat pipes coupling with a cooling fan, the effects of thermal conductivity of thermal grease, and the difference in efficiency of different diameter and multiple heat pipes. The thermal resistance deduced from thermocouple temperature measurements is used as the basis of judging the thermal performance in the heat pipes.
The results indicate that the thermal grease with higher thermal conductivity mainly reduces the contact resistance but not convection resistance and equivalent heat pipe resistance. Because the maximum heat removal capacity of smaller diameter heat pipes ,such as 4mm and 5mm ones ,is small, the thermal performance is limited. When using one heat pipe in natural convection, a single 6mm heat pipe can reduce the temperature by about 3.3 ℃~10.2 ℃, as compared with the 4mm and 5mm one. When using two heat pipes in natural convection, the 6mm heat pipe can reduce the temperature by about 0.7 ℃∼5.7 ℃, as compared with the 4mm and 5mm ones. This is because the maximum heat removal capacity of the multiple heat pipes can handle the heat dissipated. Thus using multiple heat pipes for 6mm in diameter, the efficiency is not significantly improved. On the other hand for 4mm and 5mm ones, multiple heat pipes can improve the thermal performance ,as compared with that of a single heat pipe. Cooling the heat pipe condenser section has greater influence than those of the diameter and the number of the heat pipes. Forced convection at the condenser section can reduce thermal resistance by about 60.6% than that of natural convection.
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