Motion Evolution Mechanism of Falling Film over Horizontal Tube at Low-Spray Density

Abstract

Horizontal falling film absorber has been widely applied in petroleum, chemical industry, and toxic gas disposal due to its advantages of large fluctuation of gas–liquid interface, accurately controlled interface, easy separation of gas–liquid interface, and low-pressure drop. The study of the velocity evolution of the liquid film at low-spray density is essential to understand the micro-mass transfer mechanism of the reactor and strengthen the absorption. The present study first deciphered the subregion features of the falling film motion over a horizontal tube with varied flow patterns and the parameters, such as spray density, spray height, and salinity that affects the velocity distribution of the falling film at low-spray density for the superhydrophilic surface, were also investigated using the modified PIV method. The result indicated that the velocity distribution of the film renders a typical subregion effect, i.e., nonimpact zone and impact zone for droplet mode, while, for jet mode, the film between the adjacent columns exists in the form of mutual repetition, and the velocity of the film will be slightly higher than that of the body motion region at the interaction ring. It was also found that the spray density and spray height had a positive effect on the average velocity of falling film over the horizontal tube for droplet mode and jet mode. However, for the droplet mode, the spray density increases the velocity of the film by increasing the frequency of the droplet impact. In addition, the average velocity of the film decreases with the increase in the salinity (viscosity).