Experimental study on operating characteristics of a cryogenic loop heat pipe without additional power consumption

The infrared sensors/detectors in the space infrared detection system are required to be cooled down to a cryogenic temperature range. Cryogenic loop heat pipes (CLHPs) are promising thermal management devices, which could isolate the mechanical vibration and electromagnetic interference from cryocoolers. However, the traditional CLHPs require additional power consumption during the cooling down or even normal operation, which add more burden of cryocoolers. An innovative CLHP with a flexible wick was described in this paper, which could transport cryogenic liquid by capillary effect. Additional power consumption is not required at all for this CLHP during the cooling down and normal operation. In this paper, the cooling down characteristic and operating performance of the CLHP with nitrogen as working fluid were experimentally investigated in detail. The maximum heat transport capacity of the CLHP with 1.31 MPa filling pressure was experimentally examined, which achieved 28 W over a 0.5 m distance. With the increase of filling pressures from 0.42 MPa to 1.28 MPa, the CLHP could realize cooling down process successfully and the total cooling down time decreased significantly from 245 min to 137 min. The CLHP could operate stably with the filling pressure from 1.1 MPa to 1.31 MPa. A minimum thermal resistance of 0.43 K/W was obtained corresponding to 1.1 MPa filling pressure. The CLHP failed to work with a low filling pressure of 0.85 MPa or 1.0 MPa. In addition, the performance optimization of the CLHP was analyzed and experimentally validated.