INFLUENCE OF VAPOR BUBBLES ON THE THERMAL PERFORMANCE OF A TWO-PHASE CLOSED THERMOSYPHON LOOP WITH A LIQUID HEAT TRANSFER AGENT

In this paper, an experimental investigation on the thermal performance of a two-phase closed thermosyphon loop with a liquid heat transfer agent (TPCTLL) is considered for the first time. TPCTLLs have shown interesting heat transfer characteristics, though it has not attracted very much attention from researchers. In this work, repetitive experiments were conducted on the designed closed thermosyphon loop with a filling ratio of 95% and with the focus on the heat transfer performance along with increasing heat input. The experimental results of the TPCTLL reveal three types of heat transfer phenomena, including natural convection around the heating section at low heating power, quasisteady-state flow with periodic fluctuations at a medium heating power, and stable flow with consecutively generated vapor bubbles at a high heating power. In addition, an experiment on the thermal performance of a SPCTL is conducted for comparison purposes. The analysis indicates that the stable and outstanding operation of the TPCTLL appears at high input heat which exceeds the heat transfer limitation of the SPCTL with the same structure and working fluid, and the heat transfer coefficient of the TPCTLL becomes higher than that of the SPCTL.