Research on phase change of vertical annular falling film heat transfer in tube at high liquid film Reynolds number

The turbulent gas–liquid heat transfer process in inlet section of falling film heat transfer in tube is very severe. To research the effect of high Reynolds number (Re_l=1.81 × 10⁴∼4.23 × 10⁴) phase change heat transfer characteristics and mechanism of falling liquid film in the scrubbing cooling tube. Vertical falling film flow model of the scrubbing cooling tube is established. The influence of liquid film temperature, Re_l and gas phase temperature on gas–liquid two-phase phase change heat transfer effect is studied using User Defined Function (UDF) in FLUENT. The results show that outlet temperature of gas–liquid mixed fluid rises with the increase of the initial gas temperature, and the gas–liquid heat transfer effect is most intense at 0–0.1 m. When gas temperature is 673 K, the maximum heat transfer coefficient (HTC)is about 899 W/(m²·K).When liquid film inlet temperature rises, HTC decreases, and the maximum deviation between calculated data and experimental correlations is about 12.43 %. When the gas temperature is between 1173 K and 1573 K, the cross-sectional temperature and water vapor content inside the tube increase. The HTC between gas and liquid phases is directly proportional to the liquid film Re_l and the dimensionless temperature. The maximum deviation between the fitted curve value and the calculated value is 11 %, fitting degree R² = 0.98.