TED-AJ03-306 Effect of Flow Direction on Condensation Heat Transfer of Air-water Mixture inside a Vertical Cooled Tube :

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Abstract

As a basic research for the development of an environment-friendly thermal energy recovery system with high-performance and compact size, detailed experiments have been conducted to investigate the possibility and the mechanism of the enhancement of condensation heat transfer by the countercurrent wavy flow. Based on the results of a visual observation of the phenomena by using a high-speed video recorder and the measurement of condensate rate respectively from an upper and a bottom end of a cooled tube, in which constant humidity vapor of air and water flowed upward or downward, the dynamic behavior of liquid film and vapor flow was classified into four distinctive patterns in quality and quantity. The heat transfer characteristics were discussed in relation to the above flow patterns and the transitional condition of the each pattern due to the interfacial shear stress between the condensed liquid and the vapor[figure] flow. Conclusively, it was clarified that the condensation heat transfer rate was enhanced by the effects of the countercurrent flow, and that there existed the optimum operating condition since the enhancement ration of condensation hear transfer was affected by the tube sizes.[figure]

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