Experimental characterization of neon pulsating heat pipes for cryocooler-based HTS magnets

Abstract

Pulsating heat pipes (PHPs), i.e. passive devices employing two-phase flow, are increasingly studied in cryogenic conditions to improve heat transfer between cryocoolers and high temperature superconducting (HTS) magnets. This paper presents the experimental characterization of PHPs tested in vertical orientation using neon as working fluid. The main objective is to carry out a parametric study to assess the optimum parameters for a potential application to the cooling of HTS magnets. A summary of the literature on PHPs experiments under cryogenic conditions justifies the choice of neon as the working fluid for this specific application. It also leads to the selection of high-performance PHP designs for the parametric study. The PHP designs, the experimental setup, procedures, and campaigns are described. The results of the individual characterization of two PHPs, having 5 and 10 turns respectively, are analyzed and their performances are compared. In addition, a specific configuration operating simultaneously two 5-turn PHPs in parallel is investigated. The experiments are performed for two condenser temperatures (27 and

), a wide range of filling ratios (15 to 90%) and of heat loads (2 to

). The effect of the number of turns and the series or parallel configuration on the thermal performance is quantified and discussed, along with the effect of condenser temperature, filling ratio and heat load. The optimum parameters are found to be the two 5-turn PHPs in parallel, the filling ratio of 35% and the condenser temperature of

. These conditions lead to the lowest evaporator temperatures with thermal resistances ranging from 0.15 to

, while keeping a reliable working stability and no dry-out phenomena occurrence in the heat load range tested.