Marangoni condensation on external wall of vertical tube under different vapor velocities

The effect of vapor velocity on the condensation heat transfer characteristics of the ethanol-water vapor mixtures on vertical tube was investigated. The results indicated that, under the same vapor pressure, the condensation heat transfer coefficients generally increased with increasing vapor velocity. However, there were some differences when the different ethanol concentrations were used. At lower ethanol concentrations (1%, 2%, 5%), with the increase of the vapor velocity, the heat transfer coefficients increased noticeably. At higher ethanol concentrations (20%, 50%), the effect of vapor velocity on the heat transfer coefficients became less. It is possible that, with the increase of the ethanol concentration, the effect of the vapor velocity on the vapor diffusion layer becomes less because the vapor diffusion layer grows thicker.