Effects of Vapor Pressure on Marangoni Condensation of Steam-Ethanol Mixtures

Abstract

Reported herein are the experimental data for Marangoni condensation of steam-ethanol on a vertical plane surface. To clarify the effect of vapor pressure on Marangoni condensation, the heat flux and the vapor-to-surface temperature difference (surface subcooling) were measured for steam-ethanol mixtures over a wide range of compositions at vapor pressures of 84.5, 47.36, and 31.16 kPa. Seven condensation modes, smooth film, drop, film-drop, streak, drop-streak, wavy-streak, and drop with tail, were observed in this experiment The experimental results showed that heat transfer coefficients of vapor mixtures of different compositions increased with vapor pressure. The effect of vapor pressure in enhancing the condensation heat transfer coefficient was less for pure steam and extremely high compositions (22 and 51%) than for low and middle compositions (0.5,1, 5, and 10%). The maximum heat flux and heat transfer coefficient in the condensation characteristic curves were 2.37 MW/m 2 and 0.15 MW/(m 2 K), respectively, for a vapor velocity of 2.0 m/s, and appeared at an ethanol vapor mass fraction of approximately 1% and a pressure of 84.53 kPa. The condensation heat transfer was enhanced approximately 7.5 times compared with pure steam.