Experimental study on the boiling/condensation heat transfer performance of a finned tube with a hydrophilic/hydrophobic surface

Abstract

Currently, a increasing number of exchange tubes are requied for both boiling heat transfer and condensation heat transfer. Thus, it is necessary to enhance, both the boiling heat transfer performance and condensation heat transfer performance of the tube is necessary. However, few studies have been conducted in this field. A stepped lattice finned tube is suggested to enhance both boiling heat transfer and condensation heat transfer. There is room for the heat transfer enhancment of efficiency considering that wettability can also influence the heat transfer. Hence, in this study, the heat transfer performances of tubes with hybrid Hydrophilic-hydrophobic surfaces and functional fins are experimentally investigated. The condensation heat transfer coeffient and boiling heat transfer coefficient of the tube with an inner hydrophobic cavity wall and outer hydrophilic fin are nearly 3 times and 1.8 times those of the smooth tube, respectively. In boiling heat transfer, the inner hydrophobic surface can lower the bubble nucleation barrier and the outer hydrophilic surface can prevent the heat transfer surface from being covered by a vapour film. In condensation heat transfer, the outer hydrophilic surface can lower the droplet nucleation barrier and the inner hydrophobic surface contributes to dropwise condensation.