Experimental analysis of operation failure for a neon cryogenic loop heat pipe

As a highly efficient cryogenic heat transfer device, cryogenic loop heat pipes (CLHP) hold significant application potential in the thermal control of future generation space infrared detection system. However, operation failure or anomaly occurs more easily for CLHPs, no matter in the supercritical startup or steady-state operation, due to very low operating temperature combined with narrow operating temperature range. In this work, a neon CLHP operating at 30–40 K was developed, and its operating characteristics were investigated experimentally mainly about the temperature fluctuation and operation failure phenomena. To be specific, the influences of charged pressure of working fluid, primary heat load and impurity air on the supercritical startup, and the effects of heat sink temperature, charged pressure of working fluid and auxiliary heat load on the steady-state operation were studied. Experimental results showed that the application of small primary and secondary heat loads may lead to a supercritical startup failure. Insufficient working fluid under relatively low charged pressure would cause temperature fluctuation of the secondary evaporator during the supercritical startup. There existed a maximum percentage of impurity gas, i.e., about 0.35%, allowing the CLHP to achieve a successful supercritical startup. The secondary evaporator would dry out if the CLHP was subject to improper heat sink temperature, charged pressure of working fluid or auxiliary heat load, due to insufficient liquid supply to the secondary evaporator wick or the capillary limit.