Experimental Investigation on Heat Transfer in Two-Phase Closed Thermosyphon Containing Non-Condensable Gas

Given that two-phase closed thermosiphons (TPCT) are a prevalent and efficacious means of heat transfer. However, non-condensable gas (NCG) may potentially impact the heat transfer performance of the aforementioned devices. Nevertheless, the theoretical analysis of heat transfer in TPCT containing NCG is not fully comprehensive and therefore requires further supplementation by means of relevant experiments. This paper presents the development and experimental investigation of a theoretical heat transfer model for a TPCT containing NCG. The research encompasses the optimal fluid-filling ratio of R22 and R410a working fluid and the impact of NCG on heat transfer in the condenser section of TPCT. Experimental findings indicate that TPCT with R22 and R410a working fluids at a fluid-filling ratio of 60% and 50%, respectively, demonstrate excellent isotherm and heat transfer efficiency. The presence of NCG affects the condenser section heat transfer process of the vapor, leading to a 2 °C decrease in the average temperature of the condenser section of the TPCT (Tca). In comparison with the TPCT without NCG, it was observed that an increase in the mass of NCG from 0.0097 to 0.0197 mol resulted in a reduction in the effective length of the condenser section (La) and effective heat transfer rate (κ) of R22 TPCT. The decrease in La was 75.1 mm, while the decrease in κ was 15.02%. Furthermore, at the same NCG mass, the effective heat transfer rate of R410a TPCT is evidently superior to that of R22 TPCT. The NCG in the TPCT can be removed by using a check valve. Nevertheless, this will result in a reduction in the fluid-filling ratio of the TPCT. The temperature of the R410a TPCT containing 0.0197 mol NCG with a fluid-filling ratio of 50% is comparable to that observed in fluid-filling ratio of 40% after the NCG is exhausted.