Experimental investigation of tube diameter and inclination angle on steam condensation accompanying with air in tube bundles.

• The pressure range for the experiment was 0.2~1.6 MPa and the subcooling was 28~114 °C. • The effect of tube diameter and inclination angle in the tube bundle was analyzed. • A segmented experimental correlation with high relevance was obtained. Steam condensation accompanying with air is an important thermal-hydraulic phenomenon in reactor containment. Condensation outside tubes is an important method to remove heat out of the containment under an accident. Most of the previous studies have been conducted on single tube and vertical plates, where the findings may not reflect the heat transfer in tube bundle well. The experimental studies were firstly carried out based on 3 × 3 tube bundle with diameters of 12–19 mm and inclination angles of 0–90° in the parameter range of pressure 0.2–1.6 MPa, air mass fraction of 12.1–75.2% and wall subcooling of 28.3–114.1℃. The results indicate that the effect of diameter and inclination angle in the tube bundle varies significantly in different pressure ranges. When the pressure is less than 0.8 MPa, the condensation heat transfer coefficient (CHTC) generally increases with decreasing tube diameter and inclination angle. The CHTC of the heat transfer tube with a tube diameter of 12 mm and an inclination angle of 0° increased by a maximum of 29% compared to that of the heat transfer tube with a tube diameter of 19 mm and an inclination angle of 90°. When the pressure is 0.8–1.6 MPa, the overall CHTC decreases as the diameter of the tube decreases, and the maximum reduction is about 20%. It decreases first and then increases with the decrease of the inclination angle, and the CHTC is the smallest when the inclination angle is about 60°. [ABSTRACT FROM AUTHOR]