Condensation From Pure Steam and Steam–Air Mixtures on Integral-Fin Tubes in a Bank

Data are reported for condensation of steam with and without the presence of air on three rows of integral-fin tubes situated in a bank of plain tubes. The data cover a wide range of vapor velocities and air concentrations. Unlike previously reported data for plain tubes using the same test bank and apparatus, the heat-transfer coefficients for the finned tubes were largely unaffected by vapor velocity. When compared to a plain tube of fin-tip diameter and at the same vapor side temperature difference, heat-transfer enhancement ratios between 3.7 and 4.9 were found for the finned tubes compared to a plain tube in quiescent vapor conditions, while values between 1.9 and 3.9 were found when compared to a plain tube at the same vapor velocity. When compared to the plain tubes, the heat transfer to the finned tubes was much more susceptible to the presence of noncondensing gas (air) in the vapor, with enhancement ratios falling as low as 1.5 compared to the plain tubes when even small concentrations of air were present.