Laboratory investigation of the heat transfer characteristics of a two-phase closed thermosyphon

Two-phase closed thermosyphons (TPCTs) are widely used as heat transfer devices in engineering structures in permafrost regions to prevent freeze–thaw damage. In this paper, we reported on a laboratory experiment to study the heat transfer characteristics and working state of a TPCT installed in the soil based on the typical temperature conditions in the permafrost regions of the Qinghai–Tibet Plateau. The results indicated that when the temperature of the condenser section was lower than that of the evaporator section, and the negative temperature difference between the condenser and evaporator sections was beyond a critical temperature difference, the TPCT was active; otherwise, the TPCT was inactive. The critical temperature difference between the condenser and evaporator sections that was required for the TPCT to begin to work was defined as the “startup temperature difference”. Furthermore, we found that the efficiency of the TPCT improved linearly with the negative temperature difference between the condenser and evaporator sections when the TPCT was working. In this study, the startup temperature difference of the TPCT was about −0.20°C and the total thermal resistance was about 0.31°C/W. These results provide a basis for future work evaluating and improving the performance of TPCTs used for embankment design in permafrost regions. •A two-phase closed thermosyphon (TPCT) had a good thermal semi-conduction effect.•Its efficiency was linearly related to the negative temperature difference in working state.•The startup temperature difference of the TPCT was about -0.20°C.•The total thermal resistance of the TCPT was about 0.31°C/W.