Experimental investigation on anti-gravity loop heat pipe based on bubbling mode

Traditional loop heat pipes (LHPs) have disadvantages including high operating temperature, large heat resistance and low heat transfer efficiency under anti-gravity condition. An anti-gravity loop heat pipe (AG-LHP), in which a bubbler is added between the condenser and the compensation chamber (CC), is studied and analyzed in this paper. The bubbler is designed to enforce circumfluence of the working fluid. Integral outside fins (IOF) are used as inner cylinder surface structure of the bubbler. Bubbling experiment was conducted to evaluate the performance of the bubbler with IOF surface structure, compared with those with smooth and knurled surface structures. The infrared ray (IR) thermal imaging method was used to investigate the working process of the bubbler. Furthermore, start-up experiment was carried out to investigate the start-up phenomenon and the performance at steady state of the AG-LHP. The results of the bubbling experiment under different heating power showed that the bubbler with IOF inner cylinder surface structure had the highest bubbling height and the shortest steady time, which demonstrated that the IOF surface structure effectively improved the thermal and steady performance of the bubbler. The start-up experiment confirmed that the AG-LHP could achieve steady state in 20 min and could easily adapt to different heating loads under anti-gravity condition. The thermal resistance of the AG-LHP can approach to a value as high as 150 W/K with the heating load of 80 W.