不同压力下竖直管外Marangoni凝结换热特性研究

RESEARCH OF THE CONDENSATION HEAT TRANSFER FOR ETHANOL-WATER VAPOR ON A VERTICAL TUBE UNDER DIFFERENT VAPOR PRESSURE

本文在不同压力状态下对水与酒精混合蒸汽在竖直管外Marangoni凝结换热特性进行了可视化实验研究,观测到不同过冷度下的凝结状态．实验结果表明,在相同流速和浓度条件下,酒精浓度较低时凝结换热系数随蒸汽压力的升高而升高．但在高酒精浓度下,凝结液表面张力梯度减小,扩散热阻的影响增大,蒸汽压力对于凝结换热系数的影响并不明显．

This article experimentally studied Marangoni condensation characteristics of ethanol - water vapor on a vertical tube at different pressures, and observed the variation of condensation condition. The experimental results demonstrate that on the same condition of vapor concentration and speed, heat transfer coefficients of high pressure are bigger than those of low pressure in the lowethanol concentration range. But the effect of vapor pressure on the heat transfer coefficients is not obvious in the high-ethanol concentration range. The reason for this is that bigger diffusion resistance and the gradient of the surface tension versus the condensate mass fraction becomes smaller with the increase in vapor concentration.