A new way of supercritical startup of a cryogenic loop heat pipe

Abstract

Space applications require low power consumption, light weight and no gravity-assistant heat transfer devices. Cryogenic loop heat pipe (CLHP) is an effective heat transport device, which is able to fulfil supercritical startup with the help of a secondary evaporator or a secondary loop. However, both of the secondary evaporator and the secondary loop require additional power consumption on the CLHPs, which increase the burden of a cryocooler. This paper presents a new way of supercritical startup of a cryogenic loop heat pipe with simple structure and reliable operation performance. A flexible porous wick was introduced into the liquid line, connecting the condenser and the evaporator, to provide capillary force as the motive power for the liquid in the condenser flowing into the evaporator, which dispensed with the gravity assistance and additional power consumption. The CLHP operated at liquid-state nitrogen temperature range with nitrogen as working fluid. Investigations on the supercritical startup process and the operation process were presented in the paper. The CLHP could be cooled down from 299 K and realize supercritical startup without additional power consumption. 20 W heat loads were transported across a 0.51 m distance, and dryout was not happened all through the experiments. Furthermore, the supercritical startup process with 0.5 W heat load on the evaporator from the initial ambient temperature, and the operation process of 15 W-1 W-15 W-1 W-15 W heat load on the evaporator were also investigated. The CLHP with new way of supercritical startup performed well during the tests. The experimental results were presented and analyzed in this paper.