Experimental study of the thermal performance of a neon cryogenic loop heat pipe

Cryogenic loop heat pipes (CLHP) hold significant potential for applications in the thermal control of advanced, space based infrared exploration systems. In the current investigation, a neon CLHP operating in the 30–40 K temperature range was developed and evaluated. The thermal performance characteristics, included assessment of the supercritical startup, matching characteristics of heat loads applied to the primary and secondary evaporators, power cycling, heat transfer limit and thermal resistance variations, all of which were explored and evaluated experimentally. The longitudinal temperature and pressure variations were measured simultaneously at several locations along the loop. The experimental results indicated that the CLHP could successfully achieve the supercritical startup with an input power of 1.5 W applied to the secondary evaporator, and reach a heat transfer limit of approximately 4.0 W over a 0.6 m distance. The CLHP exhibited good response characteristics to step changes in the heat load applied to the primary evaporator, resulting in smooth temperature transitions in the primary evaporator. The thermal resistance of the CLHP was found to decrease monotonically with increasing heat load applied to the primary evaporator, with values as low as 0.4 K/W.