Heat transfer at evaporation of falling films of Freon mixture on the smooth and structured surfaces |
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Authors: | N I Pecherkin A N Pavlenko O A Volodin |
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Institution: | 1.Kutateladze Institute of Thermophysics SB RAS,Novosibirsk,Russia;2.Novosibirsk State University,Novosibirsk,Russia |
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Abstract: | The paper presents the results of experimental investigation of heat transfer and hydrodynamics of falling films of binary
mixtures of R21 and R114 freons on the surfaces with complex configuration. The vertical tubes of 50-mm diameter with the
smooth and structured surfaces, made of D16T alloy, were used as the working sections. The range of film Reynolds number at
the inlet to the working section was Re =10÷155. The image of wave surface of the falling liquid film was visualized and recorded
by a high-speed digital video camera. At evaporation the heat transfer coefficients on the smooth and structured surfaces
are determined by the liquid flow rate and weakly depend on the heat flux. At low liquid flows, the heat transfer coefficients
on the structured surface decrease in comparison with the smooth surface because of liquid accumulation and enlargement of
efficient thickness in microtexture channels. At high liquid flows, a change in the structure of the wave film surface leads
to an increase in heat transfer coefficients in comparison with the smooth surface. |
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Keywords: | |
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