Experimental study on a liquid nitrogen temperature region loop heat pipe with flat evaporator

The cryogenic loop heat pipe is an efficient deep-hypothermic two-phase heat transfer device, which will be widely applied to cryogenic thermal control system for space projects such as infrared detection in the future. Zirconia is used to develop nitrogenous flat evaporator loop heat pipe for capillary wicking materials, effectively reducing the contact thermal resistance between the heat pipe and the heat load and the back leakage heat of the heat pipe. The experiment focuses on studying the non-assisted start-up characteristics, heat transfer performance and operation under intermittent thermal load of the heat pipe. The conclusion was drawn as follows:the flat evaporator loop heat pipe at liquid nitrogen temperature is in a good condition of self-start performance without assistance, which can be rapidly cooled down from room temperature to liquid nitrogen temperature by the diffusion of working fluids. The loop heat pipe can stably run from the liquid nitrogen temperature of 70 K to 100 K, and the thermal resistance will decrease with the increase of operating temperature and heat load at the maximum heat transfer power of 15 W and the minimum thermal resistance of 0.5 K/W. The loop heat pipe can keep the temperature stable and thermal response fast under the condition of intermittent heating of evaporator without secondary cooling. The flat evaporator loop heat pipe at liquid nitrogen temperature region effectively meets the requirements for the heat transfer of the thermal control system of the space cryogenic optical system.