Experimental Investigation Of Heat Performance For Loop Heat Pipe With Self-Rewetting Fluid

Acting a highly efficient passive heat transfer element,the loop heat pipe(LHP)can effectively solve the thermal management constraints in the rapid development of electronic equipment.The factors that affect the heat transfer performance of the LHP mainly include structural design,selection of working fluid and temperature of the cold source,etc.Among them,it is particularly important to study the influence of the working fluid on improving the heat transfer performance of the LHP.A self-rewetting fluid has a special surface tension change with increasing temperature,and its value first decreases to a certain minimum value and then increases with increasing temperature.In this paper,a n-heptanol solution was used to prepare a self-rewetting fluid,and a loop heat pipe experimental system was set up.The heat transfer performance of water-LHP and 0.1wt% n-heptanol aqueous solution(NHAS)-LHP was compared to investigate the effect of self-rewetting fluid on the heat transfer performance of LHP.The main research contents and main conclusions of the full text are as follows:(1)Preparation of NHAS with mass fractions of 0.02%,0.04%,0.06%,0.08%,0.1%,respectively,the higher the concentration of n-heptanol solution,the smaller the contact angle of n-heptanol solution.Water-LHP and 0.1wt% NHAS-LHP experimental systems were set up,and the parameters characterizing the performance of the heat pipe were introduced.Uncertainty analysis was carried out on the measured temperature and system thermal resistance.(2)By testing the heat transfer performance of loop heat pipe under different heat loads,the results show that the self-rewetting fluid as the heat pipe working fluid can make the LHP start under a lower heat load.Under the same heat load,self-rewetting fluid as working fluid not only decreases the system start-up time and improves start-up stability of LHP than water as working fluid,but reduces the stable operating temperature of LHP and increases the maximum heat load of LHP.The self-rewetting fluid can effectively enhance the heat transfer of the LHP,which can reduce the system thermal resistance.At 290 W,the system thermal resistance of the 0.1wt% NHAS-LHP is reduced by 16.2% compared with water-LHP,and the thermal resistance of the evaporator is reduced by 22.4%.(3)Through the constant load operation tests at different cold source temperatures of 0°C,10°C,and 20°C,the cold source temperature has a greater impact on the start-up performance of the water-LHP system under low load,and lower cold source temperature will lead to more severe system temperature fluctuation,but the operation of 0.1wt% NHASLHP is more stable.The temperature of the cold source under high load has less impact on the stability of the LHP system operation.The thermal resistance of the system under different cold source temperatures shows a tendency to decrease with increasing cold source temperature.