Condensation Heat Transfer Characteristics of Moist Air Outside Hydrophilic and Super-hydrophobic 3D Pin Fin Tube

Three dimensional pin fin tube is an effective heat transfer element. It has been widely used in industry process. However, condensation heat transfer characteristic of moist air outside it has not been experimentally studied. The wettability of tube surface has an important effect on this process. In this study, experiments were carried out, in which moist air condensing outside three dimensional pin fin tube with different wettability. Smooth tube is also tested to make comparison. Effects of steam mole fraction, moist air temperature, and wall subcooling are analysed in detail. Super-hydrophobic surface is obtained using oxidation and self-assembling monolayer method. The results show that heat transfer coefficient increases with the increase of steam mole fraction, wall subcooling and the decrease of moist air temperature. Heat transfer coefficient ranges from 55 to 2,035 W/mK within the study of this paper, and hydrophilic three dimensional finned tube can achieve 2 times heat transfer coefficient compared with smooth tube and superhydrophobic three dimensional pin fin tube.

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