Experimental study of a nitrogen-charged cryogenic loop heat pipe

Cryogenic loop heat pipes (CLHPs) are effective and efficient cryogenic heat transport devices suitable for many space applications. In this work, a miniature cryogenic loop heat pipe (CLHP) with nitrogen as the working fluid was designed and experimentally investigated. An auxiliary loop was employed to assist the supercritical startup of the primary evaporator. The operational characteristics of the CLHP and the matching characteristics of heat loads applied to the primary and secondary evaporators were investigated experimentally. The results show that the CLHP can achieve reliably the supercritical startup when the heat load applied to the secondary evaporator is no less than 3 W; when the heat load applied to the primary evaporator is no less than 2.5 W, the primary evaporator can operate independently, otherwise a proper selection of the heat load applied to the secondary evaporator should be considered to overcome the parasitic heat load from the ambient. The CLHP is working at the variable conductance mode and can achieve smooth operational transition subject to a large step change of the heat load applied to the primary evaporator.

► A miniature nitrogen-charged cryogenic loop heat pipe (CLHP) was designed. ► The operating characteristics of the miniature CLHP were experimentally studied. ► Based on the experimental results, many important conclusions have been drawn.