Falling film hydrodynamics of horizontal elliptical tube under column flow

Abstract

Flow characteristics of falling film around a horizontal elliptical tube under column flow were numerically investigated with the volume of fluid method. The three-dimensional film thickness distributions for elliptical tubes with three ellipticities and two arrangements (the major axis oriented vertically and the major axis oriented horizontally) were captured. This investigation also considered the effects of spray Reynolds number and contact angle on film thickness distribution. A comparison between elliptical tube and circular tube was also performed under typical spray Reynolds number of 258 and tube spacing of 20 mm. The results show that the tube shape has a great influence on the film thickness and flow behaviors: The liquid film formed outside the elliptical tube with the major axis oriented vertically is thinner and more uniform than that of the circular tube. Conversely, the film on the elliptical tube with the major axis oriented horizontally is thicker and more non-uniform than that of the circular tube. The increasing of Reynolds number generally increases film thickness, particularly in the crest region. Under incompletely wetted condition, the increasing of ellipticity decreases the liquid film coverage rate around the tube. In addition, a correlation for predicting the film thickness around elliptical tubes was proposed.