Publisher Summary This chapter studies fluid–flow characteristics of liquids in layers, with and without a superimposed gas velocity. The types of turbulence in layers need to be investigated and also the nature of a laminar layer containing ripples. As regards the theoretical studies of film flow, it is shown in the chapter that it is possible to predict quite accurately the flow behavior in the smooth laminar flow regime of the film; unfortunately, this flow regime is not of great practical importance. The Kapitsa theory for wavy film flow appears to apply over only a very limited part of the total wavy flow regime. Several new experimental techniques for the study of film flow have been developed. Film flow is a special case of two-phase flow. It takes place along a solid surface of some sort, with only one free surface. The second phase in contact with the free surface of the film may be either a gas or a second liquid, which may be at rest or in motion relative to the solid surface on which the film flows. Film flow is distinguished from other forms of two-phase flow by the presence of large interfaces of basically simple geometrical configuration. Two-phase flows are also often further classified as single-component. The occurrence and applications of film flow in modern technology are numerous and important.

Mass Transfer between the Wall Surface and the Falling Liquid Film

The Flow of Liquids in Thin Films

Mass transfer equations are derived and compared with dissolution experiments of C6H5COOH-H2O and Cu-H2SO4-K2Cr2O7 systems on single spheres (6 different sizes from 3/4" to 3"). In region I (long contact time with smooth laminar film), Sh converges Sh=1.608 (GaSc/Pe*)1/3 or k=2.01 D√δ(δ: mean film thickness) and increases with decreasing volumetric flow rate Q. In region II (short contact time with smooth laminar film), Sh converges Sh=0.716 Pe*1/9(GaSc)2/9The transition from region I to II occurs around Pe*/(GaSc)1/4≤10. In region III (short contact time with wavy film surface), Sh increases with Pe* to the 1/3 - 1/2 power and is substantially higher than that in region II. A generalized short contact time equation using the measured local film thickness δ Sh=0.501 Pe*1/3{∫π0(d/δ)sinθdθ}2/3is valid in this region. Thus, main cause for enhancement in Sh is the reduction in film thickness relevant to the wave formation. The II-III transition is somewhere between wave inception and wave coverage flow rates. In the above, Sh=kd/D, Pe*=Q/dD and Ga=gd3/v2, in which k is based on a log-mean driving force.

https://www.jstage.jst.go.jp/article/jcej1968/7/1/7_1_19/_pdf

Mass Transfer between the Wall Surface and the Falling Liquid Film

Citations

The Flow of Liquids in Thin Films

Solid-liquid mass transfer in falling liquid films on single spheres

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