Free Convection Condensation of Multi-component Vapor Mixture on a Horizontal Smooth Tube (Surface Shape and Heat Transfer Characteristics of Condensate)

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This research project deals with the experiment of free-convection condensation of multi-component vapor mixtures on a horizontal smooth tube. Five kinds of binary mixtures of methanol/water, ethanol/water, n-propanol /water, reethanol/ethanol and methanol/n-propanol were used as test fluids. The observation of the surface shape of condensate and the measurement of the heat transfer characteristics were performed under various conditions of bulk vapor mass fraction, pressure and wall heat flux. The results are as follows :(1) For reethanol/ethanol and methanol/n-propanol mixtures the surface shape is smooth filmwise.(2) For methanol/water, ethanol/water and n-propanol/water mixtures four types of the surface shape are observed. In case of low alcohol mass fraction the surface shape is always dropwise. In case of high alcohol mass fraction the surface shape changes from drop to filmwise through streak and ringwise as the wall heat flux increases. Near azeotrope the surfaced shape is always smooth filmwise.(3) The surface shapes is classified by using the dimensionless condensate film thicknessdelta/ROO< >sigma/(rhog).(4) Non-filmwise surface shapes are induced by the surface tension inhomogeneity.(5) The heat transfer coefficient of condensate is 1.1 to 7 times higher than the theoretical values for smooth filmwise condensation, depending on the surface shapes.