Heat Transfer in a Large, Inclined, Flattened-Tube Steam Condenser

Abstract

Experimental results for capacity and heat transfer coefficient during steam condensation in a power-plant air-cooled condenser are presented. The condenser test section is a flattened steel tube with brazed aluminum fins. The tube is 5.7 m long with inner dimensions of 216 mm × 16 mm. The cooling air is in crossflow to the steam, with velocity at the fin inlet of 2.4–3.0 m s−1. Condensation pressures range from 70–105 kPa, with the tube inclined from 0–49° downwards. Adiabatic visualization sections at the tube inlet and outlet provide identification of annular flow at the inlet and stratified flow at the outlet. Steam-side heat transfer coefficient is found to depend on wall-steam temperature difference, with minimal dependence on quality or vapor Reynolds number. As a result, steam-side heat transfer coefficient does not decrease significantly along the condenser length, as is common for smaller condenser tubes with higher mass flux. There is a slight decrease in steam-side heat transfer coefficient near the condenser outlet due to a build-up of condensate at the tube bottom. Overall condenser heat transfer coefficient is found to decrease near the condenser outlet due to an increase in the thickness of the stratified condensate layer.