Investigation Of The Effect Of Thermal Conductivity On Capillary Wick And Loop Heat Pipe

Loop heat pipe (LHP), as a two-phase heat transfer device, has been widely used because of its high heat transfer capacity, flexible arrangement, high reliability, strong adaptability and long service life. LHP has been widely used in thermal control system of space equipment and become one of the most promising technology. In addition, LHP has been more and more applied in the field of the ground in recent years, such as electronic devices. The research on the improvement of the performance of LHP has become the main focus.In this work, the effect of thermal conductivity of the wick was studied. The numerical model of LHP was studied by local to integral construction. Two Stainless steel-Ammonia LHPs were fabricated. From the view of temperature and heat distribution, the heat transfer mechanism of bi-thermal-conductivity wick was deeply explored. The main work and conclusions are as follows:1. A simplified evaporator model was constructed. The effect of thermal conductivity distribution on capillary wick was analyzed. It was found that con-thermal-conductivity wick was very difficult to reduce the heat leak. Bi-thermal-conductivity wick could optimize the internal temperature field and heat flow field. The side wall heat leak was decreased obviously as well as the average temperature of evaporator was getting lower. The advantages of bi-thermal-conductivity wick heat transfer performance were verified preliminarily.2. Constructed global mathematical physics model of LHP. It showed that the existence of thermal contact resistance made the temperature difference between the evaporator and the compensation chamber. There was an optimal value of the effective thermal conductivity of the capillary wick in steady state operation, which made the total heat leak minimum. The thicker the capillary wick was, the greater the thermal resistance was. Thus the heat leak through wick body was suppressed to a certain extent. The operating temperature and thermal resistance of LHP with bi-thermal-conductivity wick were lower than that with con-thermal-conductivity wick. The bi-thermal-conductivity wick could effectively reduce the heat leak through the wick body and the evaporator wall, so that more heat flow was used for the evaporation of the working fluid under current configuration.3. Design and develop two sets of LHPs. Set up a comprehensive test experimental platform. Two LHPs with con-thermal-conductivity wick and bi-thermal-conductivity wick were tested, which the fluid was ammonia. The result showed that the influence of heat leak was remarkable under low heat load. Under the same conditions, the starting time, steady operating temperature and temperature oscillation at the condenser inlet of the LHP with bi-thermal-conductivity wick were better than that of the LHP with con-thermal-conductivity wick.