流速对混合蒸汽Marangoni凝结换热影响的实验研究

本文在蒸汽压力为47.36 kPa的条件下,通过实验研究了不同蒸汽流速(u=2、4、5 m/s)下纯水和不同酒精浓度水-酒精混合蒸汽沿重力方向流过竖直紫铜平板表面上的凝结换热特性,并实现了实验的可视化,同时分析了不同蒸汽流速下造成Marangoni凝结换热特性差异的原因.实验及分析结果表明,在相同蒸汽浓度、蒸汽压力和表面过冷度条件下,高流速下的凝结换热系数比低流速的大.且蒸汽流速对凝结换热的影响因混合蒸汽酒精浓度的不同而不同,低浓度0.5%和高浓度50%时流速的增加对凝结换热特性的影响较小,而在中间浓度2%时凝结换热强度随流速的增加明显.

EFFECT OF VAPOR VELOCITY ON MARANGONI CONDENSATION HEAT TRANSFER FOR WATER-ETHANOL BINARY VAPOR MIXTURE

Reported herein are the experimental data for so-called Marangoni condensation of steam- ethanol on small vertical plane surfaces at the vapor pressure of 47.36 kPa.In order to clarify the effect of vapor velocity on Marangoni condensation,heat flux and vapor-to-surface temperature difference were measured for steam-ethanol mixtures over a wide range of composition at vapor velocity of 2, 4 and 5 m/s.The experimental results showed that heat transfer coefficients of mixture vapors with different composition increased with vapor velocity,and the effect of vapor velocity in enhancing the condensation heat transfer coefficient was less for pure steam or extremely low or high composition of 0.5% and 50% than for middle composition of 2%.