Flow boiling heat transfer characteristics of CO2 at low temperatures

This paper presents an overview of the flow boiling heat transfer characteristics and the special thermo-physical properties of CO2 at low temperatures (down to −30 °C). Subsequently, the boiling heat transfer of CO2 at low temperatures is experimentally investigated in a horizontal tube with inner diameter of 4.57 mm. Due to the large surface tension, the boiling heat transfer coefficient of CO2 is found to be much lower at low temperatures but it increases with vapour quality (until dryout), which is contrary to the trend at high temperatures around 0 °C. None of the empirical correlations from open literature were able to predict the boiling heat transfer coefficient for CO2 in good agreement with the experimental data, suggesting the need for further research in this area.