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Turbulence in falling liquid films
Author(s) -
Stirba Clifford,
Hurt D. M.
Publication year - 1955
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690010209
Subject(s) - reynolds number , mass transfer , turbulence , laminar flow , momentum transfer , momentum (technical analysis) , chemistry , thermodynamics , heat transfer , mechanics , diffusion , materials science , chromatography , optics , physics , finance , scattering , economics
On the basis of fluid dynamic and heat transfer studies on falling‐film towers by various investigators, it has been commonly accepted by most workers that the liquid flow is essentially streamline in nature for liquid‐film Reynolds numbers under 1,800 to 2,000; conseuquently it would be expected that the rate of physical gas absorption in such liquid films could be predicted directly from a knowledge of molecular diffusion rates. Measurements of the absorption of pure gases in falling liquid films at low Reynolds numbers substantiated the findings of other investigators that the mass transfer rates were manyfold greater than could have been predicted if molecular diffusion were the only transfer process. Increased interfacial area due to rippling of the liquid films could not account for the large increase in mass transfer rates found, and experiments with the addition of a dye stream to the liquid at the freer interface indicated turbulence. Dissolution rates of slightly soluble solids coated on the tube wall to liquid films were measured and showed that the liquid film was not in laminar flow even for Reynolds numbers as low as 300. An explanation is proposed which resolves these apparently conflicting results between momentum and heat and mass transfer, based on the fact that mass transfer measurements provide a more sensitive test for the presence of turbulence than do momentum or heat transfer measurements.