Research on Marangoni condensation heat transfer of ethanol-water vapor on external wall of micro-vertical tube

In this article the effects of vapor concentration, vapor pressure and vapor velocity on the condensation heat transfer characteristics of ethanol-water mixture vapor on external wall of vertical micro tube(inner and outer diameter were 0.727/1.032 mm) were investigated experimentally. Visual results showed that condensation modes changed with the vapor-to-surface temperature difference. When the vapor-to-surface temperature difference was larger, the condensation modes were typical dropwise condensation. The condensation modes changed to filmwise with decreasing the vapor-to-surface temperature difference. The experimental results indicated that the condensation heat transfer coefficients revealed nonlinear characteristics. The condensation heat transfer coefficient of the ethanol-water mixture was found to have a maximum value of 45 kW·m ^-2·k ^-1. The heat transfer coefficients increased significantly when the vapor mixture concentrations were lower, and the heat transfer coefficients increased slowly when the vapor mixture concentrations was higher. The condensation heat transfer coefficient increased with the increase of vapor pressure and vapor velocity.