Condensation heat transfer enhancement using steam-ethanol mixtures on horizontal finned tube

Condensation of steam-ethanol mixtures was investigated experimentally on instrumented, finned copper tube. The tube had length 70 mm, fin root diameter 12.7 mm. Height, thickness and inter-fin space was of rectangular fins was 1.6 mm, 0.5 mm and 0.6 mm. Concentration of ethanol by mass in the boiler when cold prior to the start-up were 0.025, 0.05, 0.1, 0.5 and 1.0%. Experiments were conducted over a range of vapor-to-surface temperature difference at three pressures of 14 kPa, 55 kPa and atmospheric. Maximum upstream vapor velocity on condensing finned test tube at atmospheric pressure and 14 kPa was 7.5 and 15.0 m/s respectively. Heat transfer enhancement as compared to pure steam of around 3 times was obtained over a range of vapor to surface temperature difference. Results have been compared with the available data for pure steam condensation on finned tube and steam-ethanol condensation on the smooth tube under same conditions of pressure, vapor velocity and vapor to surface temperature difference. Photographs showing increase of retention angle due to ethanol are included in the paper.