Three-dimensional film thickness distribution of horizontal tube falling film with column flow

Highlights: • 3-D film thickness of horizontal tube falling film with column flow is analyzed. • Correlations are proposed to predict the film thickness based on different sections. • Effects of Re and tube spacing on film thickness have been investigated. -- Abstract: A three-dimensional numerical simulation with VOF (Volume of Fluid) model was performed to investigate horizontal tube falling film with column flow. The film thickness variation along circumferential and axial directions was studied with the effects of tube spacing ranging from 10 to 30 mm and Reynolds number varying from 221 to 295. The numerical simulation results accurately match the experimental flow behavior and show that horizontal tube falling film with column flow exhibits strong three-dimensional features. The film thickness at impingement and transition section have a relatively good agreement with Nusselt's solution, but the film thickness at departure section is much larger. The liquid film under column flow in a "flow element" can be classified into five regions. The enhancement in Reynolds number has a greater influence on film thickness in crest region. Compared with water, seawater has similar film thickness in stable region but slightly larger in crest region under same conditions. Moreover, a series of correlations have been proposed to predict the film thickness with column flow based on three typical sections.