Numerical and experimental investigation on condensing heat transfer and flow characteristics outside horizontal dentate-fin tubes

•In this study, 3D numerical models of condensation heat transfer and flow outside horizontal dentate fin tubes were established.•The validity of the developed CFD model was verified by comparing the simulation results with experimental data.•The film thickness, 3D flow process, and HTC data were analyzed. Moreover, the effects of different fin densities on the condensation, heat transfer, and flow outside the dentate-fin tubes are discussed.•The idea of optimizing the structure of the dentate-fin tube was provided and the optimal structural parameters were derived.•The mechanism of the effect of the structure and external working conditions of the high-performance tube on the heat transfer and flow processes has been thoroughly investigated. The condensing flow and heat-transfer characteristics around dentate-fin tubes were investigated using numerical and experimental methods. Using the examined computational model, the film flow characteristics and condensing heat-transfer coefficient of the dentate-fin tubes in the circumferential and axial directions were analyzed. Comprehensive information regarding the condensation process in high-performance tubes is provided for the first time. The results showed that the circumferential and axial film thicknesses of the dentate-fin tubes increased with increasing fin density. The liquid film distribution of dentate-fin tubes with a low fin density was relatively uniform, and condensate drainage was easy. The special heat-transfer structure of dentate-fin tubes was examined, and it was found that the complex heat-transfer structure led to variations in the surface tension, which changes the liquid-film distribution. The local condensing heat-transfer coefficient of the dentate-fin tubes was very sensitive to the liquid-film distribution. The optimal fin density corresponding to the maximum overall heat-transfer coefficient was obtained, which showed that the mechanism of heat-transfer enhancement for dentate-fin tubes was a joint effect of the heat-transfer area and liquid-film thickness.