蒸汽流速对竖直管外Marangoni凝结换热特性影响的实验研究

MARANGONI CONDENSATION ON EXTERNAL WALL OF VERTICAL TUBE UNDER DIFFERENT VAPOR VELOCITIES

本文在不同蒸汽流速下对水-酒精混合蒸汽在竖直管外Marangoni凝结换热特性进行了实验研究.结果表明:在相同蒸汽压力下,混合蒸汽在竖直管外凝结换热系数随蒸汽流速的增加而增加.当蒸汽酒精浓度较低时(1%、2%、5%),凝结换热系数随流速的增加而明显增加.当蒸汽酒精浓度较高时(20%、50%),流速的增加对凝结换热系数影响较小.这主要是由于蒸汽流速在低酒精浓度下对凝结扩散层热阻的影响大于在高酒精浓度下对扩散层热阻的影响.

The effect of vapor velocity on the condensation heat transfer characteristics of the ethanolwater 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.