Three-dimensional film thickness distribution of horizontal tube falling film with droplet and sheet flow

Abstract

The flow characteristics of horizontal tube falling film for droplet and sheet flow were numerically and experimentally investigated with tube diameters of 19 ∼ 28.8 mm and tube spacings of 10 ∼ 30 mm. The inter-tube flow patterns were captured by a high-speed camera and the film thicknesses around the tube were measured by a chromatic confocal displacement sensor. With the help of optical experiments and numerical simulations, the results show the flow characteristics of droplet flow and sheet flow in detail. The droplet flow includes asynchronous and synchronous droplet falls. The time-averaged film thickness for droplet flow increases with increasing Reynolds number but decreases with increasing tube spacing and tube diameter. The sheet flow experiences incomplete and complete sheet with Reynolds number increasing. The film distribution around the tube is not evenly in incomplete sheet flow stage and tends to be uniform when entering complete sheet. As for complete sheet flow, the film thickness distribution was nearly independent of tube diameter, while the upper part film thickness is mainly influenced by tube spacing.