Experimental study on the supercritical startup of cryogenic loop heat pipes with redundancy design

Abstract

Abstract:Cryogenic loop heat pipe (CLHP) is one of the key components in the future space infrared 10 exploration system, which enables effective and efficient cryogenic heat transport over a long distance with a 11 flexible thermal link. To realize reliable and long life operation, a CLHP-based thermal control system with 12 redundancy design was proposed in this work, where two nitrogen-charged CLHPs were employed to provide 13 cryocooling at 80-100K. This study focused on the supercritical startup of the CLHPs with redundancy design, 14and an extensive experimental study under four possible working modes was conducted. Experimental results 15showed that with 2.5W applied to the secondary evaporator, each CLHP could realize the supercritical startup 16 successfully in the normal working mode; however, the required time differed a lot because the difference in the 17 transport line diameter significantly affected the cryocooling capacity to the primary evaporator. In the backup 18 conversion mode, instant switch of the two primary evaporators may cause an operation failure, and an auxiliary 19 operation of the secondary evaporator in advance was necessary to make the primary liquid line filled with liquid. 20In the malfunction conversion mode, the simulated infrared detector had to be first shut down, but the time needed 21 for the backup CLHP to realize the supercritical startup became obviously shorter than that in the normal working 22 mode, because the primary evaporator of the backup CLHP was always in a cryogenic state. In the dual operation 23 mode, the two CLHPs could realize the supercritical startup simultaneously, but a temperature oscillation 24 phenomenon was observed, which can be eliminated by increasing the heat load applied to the secondary 25 evaporator. 26

Performance and impact of cryogenic pulsating heat pipe using a different number of turns and helium gas

“…The thermal conductivity fill ratio was measured in 2014 using a horizontal 60 PHP through 990 mm of adiabatic area length. Prior experiment we used8turn PHP, the length of which were 50, 50 and 100 mm respectively for evaporator, condenser and adiabatic sections [6]. The test report shows the most efficient that thermal conductivity was obtained at a helium fill ratio (HFR) of 70.8% at 15625 W/mK and was vertically focused [7].…”

The Pore Microstructure Evolution and Porous Properties of Large Capillary Pressure Wicks Sintered with Carbonyl Nickel Powder

“…For LHPs, the maximum pore diameter in wicks is vitally important because there is backflow of vapor from the evaporation zone to the compensation chamber through the pore with the largest diameter due to the inverse dependence of capillary pressure on pore diameter [ 9 ]. This kind of wick is usually characterized by a porosity of around 50% and a maximum pore diameter of about 1.0 μm [ 13 , 14 , 15 , 16 , 17 , 18 , 19 ]. Although this kind of wick is widely used and exhibits excellent performance, few studies have focused on the fabrication processes of this kind of wick, and its optimal sintering temperature is still unknown.…”

Study of the heat transfer performance of a loop heat pipe with aluminum wick

“…In addition, metallic wicks are also widely used. Guo [4] assembled an LHP with nickel wick to study the startup of a cryogenic loop heat pipe (CLHP) with redundancy and reliable and long-life operation. Experiments showed that its startup was affected by the inner diameter of the transport line and the distribution of working fluid in the system.…”