Experimental investigation and multiparameter analysis of variable conductance heat pipes

Abstract

This paper presents an experimental investigation of the influence of multiple parameters on the thermal performance of variable conductance heat pipes (VCHPs) according to theoretical design and analysis. The operating characteristics of four VCHPs, such as the steady-state temperature, thermal resistance, and degree of self-control, were systematically analysed and compared. The design principles were examined considering the structural matching design, thermal-physical properties, and charging mass of the fluids. The examined types included the cold-gas reservoir VCHP (CGR-VCHP) and the hot-gas reservoir VCHP (HGR-VCHP), whose steady-state operating temperatures and thermal resistances were compared. The HGR-VCHP attained a higher degree of self-control than the CGR-VCHP for the same heat pipe (HP) structure size. The effects of the reservoir volume of the CGR-VCHP were experimentally and theoretically assessed. Compared to a small volume of 33.66 mL, a large volume of 43.27 mL increased the self-control, with dTva/dQ dropping from 0.272 K/J to 0.042 K/J. Moreover, the temperature difference decreased from 13.6 to 2.09 °C under the same heat load increase of 50 W. Both R22 and ammonia were chosen as working fluids due to their similar sensitivity factors. The self-control ability of the ammonia CGR-VCHP was higher than that of the R22 CGR-VCHP based on the obtained experimental and theoretically calculated results. This research provides valuable insights into VCHP multiparameter analysis, which are of great significance for the practical application of VCHPs in self-control thermal.