Gas desorption from falling liquid films in entrance region of inclined wetted-wall columns with an overflow-type distributor
✍ Scribed by Haruo Hikita; Ishimi Kosaku; Koroyasu Sadatoshi
- Publisher
- Elsevier Science
- Year
- 1990
- Tongue
- English
- Weight
- 655 KB
- Volume
- 45
- Category
- Article
- ISSN
- 0009-2509
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✦ Synopsis
The effect of the developing laminar flow of falling liquid films in inclined wetted-wall columns with an overflow-type distributor on the liquid-phase mass transfer was investigated theoretically and experimentally. The equation of motion for wave-free flow of the falling liquid film and the convectivediffusion equation for mass transfer in the falling liquid film, based on the boundary layer approximation, were solved simultaneously. A numerical solution for the liquid-phase Sherwood number was obtained as a function of the liquid-phase Reynolds and Schmidt numbers, the angle of inclination of the wetted-wall plate and the dimensionless distance in flow direction. Experiments were carried out on the desorption of oxygen from water into pure nitrogen. The experimental data were in fairly good agreement with the theoreticai predictions in the entrance region of the failing liquid films. 1NTRODUCTION Falling liquid films are encountered in various types of mass and heat transfer equipment and a number of investigations have been carried out on transport phenomena such as mass, heat and momentum transfer in falling liquid films, as reviewed by Fulford (1964). However, transport phenomena in the entrance region have received less attention than that in the fullydeveloped region. Ito and Tomura (1979), Brauner and Maron (1982) and Hikita et al. (1987) have investigated the entrance region flow of falling liquid films in inclined wetted-wall columns with an overflow-type distributor.
The experimental and theoretical results have shown extremely long entrance regions, where the falling liquid film was laminar and had a smooth surface, although the liquid-phase Reynolds number was greater than 2500. Further, Hikita et al. (1987) have found that the surface velocity and the liquid film thickness varied greatly downstream in the entrance region. For this situation the effect of the developing flow on transfer rates must be taken into account.
Since industrial wetted-wall columns are operated at high liquid flow rates to avoid dry patches and to attain high transfer rates, the existence of the long entrance region cannot be neglected, and thus the effect of the developing flow is of practical importance. Further, wetted-wall columns are used as an apparatus to measure liquid-phase diffusivity of gases '\ ', -.