Effect of non-condensable gas on thermal characteristics in two-phase closed thermosyphon

Abstract With the development of building energy saving technology, low-temperature two-phase closed thermosyphon (TPCT) will be widely used in building energy supply and storage. However, the non-condensable gas (NCG) can affect the performance of TPCT. In this paper, experiment, theoretical heat transfer model and CFD simulation model have been established to comprehensive analyze the operation performance of the TPCT with NCG (NTPCT). The research contents include the variation of TPCT wall temperature, heat transfer efficiency ( η ), thermal resistance ( R ) and NCG phase distribution. Experimental results showed that the temperature difference between the evaporator and condenser sections of the NTPCT was greater than that of the TPCT in the steady state, resulting in R exp NTPCT being higher than R exp TPCT , and the difference was widening with the decrease of input temperature ( T b ), leading to serious adverse impact on heat transfer. When T b was higher than 60℃, the η theory difference with different mass of NCG ( X NCG =0.0418%∼0.0746%) was small, but when T b was low, the difference became larger, and even when T b =27℃, the η theory =44.02% for X NCG =0.0418%, and η theory =0.04% for X NCG =0.0746%, i.e., the heat pipe failed to work. In addition, with the decrease of inclination angle, NCG diffused downward and occupied more and more length of the condenser section, resulting in worse and worse heat transfer performance.