Study on Condensation Heat Transfer for Steam-Ethanol Vapor Mixture : Relation between Condensation Characteristic Curves and Modes of Condensate

The relation between the condensation characteristic curves, which show the variations of heat flux or heat transfer coefficient with the changes in surface subcooling, and the aspects of condensate on the heat transfer surface was investigated. The aspects of condensate were divided into six different characteristic modes, that is, ordinary smooth film, rivulets on smooth film, relatively large drops on smooth film, dropwise with drops of various sizes, rivulets on dropwise and wavy film, which appeared in order of increasing surface subcooling for all ethanol concentrations (mass fraction between 0.17 and 0.74). Furthermore, on the basis of photographs taken simultaneously with the measurement, the coverages of the surface by the condensate, which were the main heat transfer resistances for each mode of condensate, were measured. The correspondence among the heat transfer characteristic curves, the modes of condensate and the surface coverage of condensate of main resistance are shown quantitatively.