Abstract
Infrared detectors on satellites and spacecraft require cooling to increase their measurement sensitivity. To efficiently cool infrared detectors in a zero gravity environment and in limited spaces, a cryogenic loop heat pipe (CLHP) can be used to transfer heat over a certain distance by the capillary forces generated from porous wicks without a mechanical power source. The CLHP presented in this study transfers the heat load to a condenser 0.5 m away from an evaporator at temperatures below −150 °C. The CLHP with two evaporators includes a subloop for initial start-up, and uses a pressure reduction reservoir (PRR) for the supercritical start-up from room to cryogenic temperature. Nitrogen is used as the working fluid to verify the thermal behavior of the CLHP, and the heat-transfer capacity according to the nitrogen charging pressure of the PRR is investigated. To simulate a cryogenic environment, the CLHP is installed inside a space environment simulator, including a single-stage GM (Gifford McMahon) cryocooler to cool the condenser. The CLHP is horizontally installed to simulate zero gravity. The heat-transfer characteristics are experimentally evaluated through the loop circulation of the CLHP.
Highlights
Infrared detectors for space applications require efficient cooling to increase their measurement sensitivity
The evaporator consists of a wick and a compensation chamber (CC), which is a device that makes it possible for the working fluid to circulate through the loop with capillary pressure
Capillary pressures that can occur at the interface of the working condenser, and the liquid condenser flows through the main liquid line to the main CC
Summary
Infrared detectors for space applications require efficient cooling to increase their measurement sensitivity. Zhao et al designed and experimentally investigated a CLHP to cool parallel condensers using liquid nitrogen, and showed a maximum heat-transfer capacity of 41 W at a heat-transfer distance of. Experimentally investigated a prototype CLHP operating at 80 K using liquid nitrogen and achieved a maximum heat-transfer capacity of 19 W, a temperature difference of 5 K, and a heat-transfer distance of 0.5 m [17]. Previous studies have clearly demonstrated the heat-transfer performance of CLHPs, but some aspects have not been properly considered, e.g., a thermo-hydraulic design for loop circulation, optimization of the cooling flow path in the condenser, the thermal behavior of the CLHP in a subcooled condenser, and the durability of the CLHP for long-term operation. Long-term experiments were conducted over 32 hours to verify operational stability
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