루프형 세관 히트 파이프의 열전달 특성에 관한 연구

Abstract

Heat pipes have a very excellent heat transfer performance. They are utilized latent heat for heat transfer. But existing heat pipes have several defects in spite of excellent heat transfer performance. The Loop type capillary heat pipe is an epoch-making heat pipe and it is removed several defects of existing heat pipes. This study is performed to obtain the foundation materials about the loop type capillary heat pipe.

In this paper, heat transfer characteristics of loop type capillary heat pipe is experimentally investigated for the effect of several charge quantity ratios of working fluid and heat loads. And characteristics of temperature oscillation on looped capillary heat pipe are experimentally analyzed by means of the deterministic's manner on chaotic dynamics. Heat loads and working fluid were changed from 100W to 600W and 20% to 80%. Water was used as working fluid inside heat pipe. This type heat pipe consists of a heating section, a cooling section and an adiabatic section. A heating section is processed a copper block and an electric heater is inserted inside a copper block. An adiabatic section consists of very excellent insulations like ceramic insulation. A cooling section is made a transparent acryl plate. The heat pipe used has a 0.002m internal diameter, a 0.34m length in one turn and consists of 19 turns. Heating and cooling sections each have a length of 0.07m. Adibatic section has a length of 0.2m. Experiments were performed to measure the temperature and the pressure variation of heat pipe. A K-type thermocouple is adhere to a heating section, a cooling section and an adiabatic section. A pressure tranducer adhere to an upper end of the cooling section. And then, After the heat pipe is done a stationary state, Data were sampled 1000, 1000, 4000 by 3, 9, 135Hz respectively. This study was made use of a mean value of each section. Heat transfer performance, effective thermal conductivity, boiling heat transfer and condensation heat transfer coefficients were calculated for various operating conditions of heat pipe and it is found that heat transfer characteristics of this type heat pipe is very excellent. An effective thermal conductivity was thousands as much as that of copper. As this experimental results, this type heat pipe operates by the oscillatory flow caused by the pressure and temperature oscillation. Besides the looped heat pipe was operated by self-excited oscillation and circulation of working fluid, and oscillation of capillary heat pipes assumed chaotic behavior.