Hysteresis phenomena in loop heat pipes

Abstract

Testing of loop heat pipes (LHPs) has shown that the heat-load dependence of the operating temperature is not always unambiguous. It may have a hysteresis nature. It has been found that temperature hysteresis is connected with changes in the liquid distribution between the compensation chamber (CC) and the condenser. Analysis makes it possible to distinguish three types of temperature hysteresis. In the first case this redistribution is caused by the change in the amount of the parasitic heat flow that penetrates into the CC, which in its turn is a result of heat-transfer hysteresis in the evaporation zone. In the second, temperature hysteresis is connected with the liquid metastable state, which leads to a delay of formation of the vapor phase in the compensation chamber. The reason for hysteresis of the third type is the change of the initial liquid distribution in an LHP during a start-up.