Flow boiling heat transfer analysis of new experimental data of CO_2 in a micro-fin tube at -30℃

摘要

This paper presents an experimental investigation of the flow boiling heat transfer characteristics of CO_2 in a horizontal micro-fin tube at saturation temperature of -30℃. The test tube, made of copper, with outer diameter of 7.94 mm, was uniformly heated ohmically by high electric current through a transformer. The tests were conducted at mass and heat fluxes, ranging from 100 to 250 kg m~(-2) s~(-1) and 10-25 kW m~(-2), respectively. The new experimental data from these tests for varying conditions is provided in Appendix 1 for future research. The experimental data shows that h_(tp) increases with vapour quality until dryout, and decreases with saturation temperature, while heat flux has more pronounced effect on h_(tp), suggesting the dominance of nucleate boiling. Furthermore, predictions from several empirical correlations disagree with the current CO_2 experimental data in the micro-fin tube. [11] and [4] correlations predict with deviations of up to ±50%.