Experiment on liquid film flow and heat transfer of laminar liquid jet impacting on cylindrical surface

Abstract

Laminar liquid jet impact has good heat transfer performance with low impact stress on targets. In order to explore the liquid film flow and heat transfer under laminar liquid jet impact on a cylindrical surface, first the flow of a liquid film was analyzed visually; then, the local convective heat transfer characteristics on the cylindrical surface at different impact heights and outlet Reynolds numbers (Re) were obtained by a combination of direct measurement and numerical simulation, followed by a comparative analysis with continuous droplets impacting on the cylindrical surface. The results show that according to flow behavior of the liquid film along the circumferential direction, circumference can be classified into stagnation, thin liquid film, hydraulic jump, stable flow path, and dripping regions. Local convective heat transfer coefficient first drops and subsequently increases marginally along the circumferential direction, while decreasing monotonically along the axial direction. The effect of impact height and outlet Re on local convective heat transfer coefficient is manifested mainly in stagnation, thin liquid film, and hydraulic jump regions. For outlet Re = 984, as impact height rises to a certain degree, there are apparent enhancements of the liquid film perturbation and convective heat transfer performance. Finally, the local Nusselt number correlations in different circumferential regions were proposed.