Flow boiling heat transfer analysis of new experimental data of CO2 in a micro-fin tube at −30 °C

Abstract

This paper presents an experimental investigation of the flow boiling heat transfer characteristics of CO2 in a horizontal micro-fin tube at saturation temperature of −30 °C. 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 htp increases with vapour quality until dryout, and decreases with saturation temperature, while heat flux has more pronounced effect on htp, suggesting the dominance of nucleate boiling. Furthermore, predictions from several empirical correlations disagree with the current CO2 experimental data in the micro-fin tube. [11] and [4] correlations predict with deviations of up to ±50%.