Interfacial waves with condensation of a vapor flowing inside a horizontal, rectangular duct

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Interfacial waves on condensate films inside ducts increase heat transfer rates and lead to changes inflow regimes. We report the results of an experimental study of interfacial waves with condensation of a vapor on the cooled bottom surface of horizontal duct and with air-glycerine-water mixture flow in an identical duct. R-I13 and FC-72 (developed by the 3M Company) were used in the condensation experiments. Wavy flow patterns with two- and three-dimensional waves were observed. Interfacial waves with condensation appeared when the vapor velocity was in the range 1.24-1.56 m/sfor R-I13 and 0.81-1.13 m/sfor FC-72, corresponding to vapor Reynolds numbers in the range 20,000-30,000—the value depends on the difference in the temperatures of the condensing surface and saturated vapor. The ratio of the distance from the leading edge (at which the waves appeared) to the liquid film thickness was found to be a Junction of the liquid Reynolds number. Condensation stabilizes the interface. None of the several available criteria for the incipience of the waves was found to be satisfactory. A modification to the criterion employed by Jensen and Yuen ill is suggested. Other details such as wave speed and wave separation distance are included. © 1994 Taylor & Francis Group, LLC.

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Experimental Heat Transfer