Falling-film column
A falling-film column (or wetted-wall column) is a kind of laboratory equipment used to achieve mass and heat transfer between two fluid phases (in general one gas phase and one liquid phase).
It consists of a vertical tube-shaped vessel: the liquid stream flows downwards through the inner wall of the tube and the gas stream flows up through of the centre of the tube.[citation needed]
Description
[edit]
In the most common case, the column contains one liquid stream and one gas stream. The liquid forms a thin film that covers the inner surface of the vessel;[1] the gas stream is normally injected from the bottom of the column, so the two fluids are subjected to a counter-current exchange of matter and heat, that happens through the gas-liquid interface.[citation needed]
Sometimes, the same equipment is used to achieve the co-current mass and heat transfer between two immiscible liquids.[2]
Applications
[edit]Because they are easy to model, falling-film columns are generally used as laboratory equipment, for example to measure experimentally the values of transport coefficients.[1] A significant experiment was carried out in 1934 by Edwin R. Gilliland and Thomas Kilgore Sherwood that used a falling-film column to study the mass transfer phenomenon between a liquid phase and a gas phase, obtaining an experimental correlation between the Sherwood number, Reynolds number and Schmidt number.[3]
Falling-film columns are not used at industrial scales, because they have a low surface area and liquid hold-up[definition needed] compared to other gas-liquid contactors (e.g. a packed column or a plate column).[citation needed]
References
[edit]- ^ a b Binay K. Dutta, Principles of Mass Transfer and Separation Processes, Nuova Delhi, Prentice-Hall of India Private Limited, 2007, p. 91. ISBN 8120329902.
- ^ Satoru Asai, Junichi Hatanaka , Toshiya Kimura , Hidekazu Yoshizawa, Mass transfer in wetted-wall column with cocurrent laminar liquid-liquid flow in Industrial & Engineering Chemistry Research, vol. 26, n. 3, ACS Publications, marzo 1987, pp. 483–488. DOI:10.1021/ie00063a014.
- ^ Robert S. Brodkey, Harry C. Hershey, Transport Phenomena: A Unified Approach, Brodkey Publishing, 2003. ISBN 0972663584.