Steam condensation heat transfer coefficient (HTC) in a large, flattened tube with variable heat flux, wall temperature and inclination angle is determined experimentally. The condenser tube is that used in air-cooled condensers for power plants.

The steel tube has an elongated-slot cross section with inner dimensions of 216 x 16 mm. Vapor and liquid flow concurrently through a 5.7 m long air-cooled conditioning section. Tube inclination angle is varied from 0 – 50^o downwards. The long conditioning section mimics conditions in an operating condenser, and allows for realistic development of flow regime and void fraction.

HTC is determined in a water-cooled section. Quality in this section ranges from 0 – 0.3. A visualization section allows determination of flow regime and void fraction.

The flow is found to be stratified for all conditions. Results are compared to inclined condensation HTC correlations, and the correlations are found to underpredict the experimental HTC by up to 50%.