Lewis number
In
dimensionless number defined as the ratio of thermal diffusivity to mass diffusivity. It is used to characterize fluid flows where there is simultaneous heat and mass transfer. The Lewis number puts the thickness of the thermal boundary layer in relation to the concentration boundary layer.[1] The Lewis number is defined as[2]
- .
where:
- α is the thermal diffusivity,
- D is the mass diffusivity,
- λ is the thermal conductivity,
- ρ is the density,
- Dim is the mixture-averaged diffusion coefficient,
- cp is the specific heat capacity at constant pressure.
In the field of fluid mechanics, many sources define the Lewis number to be the inverse of the above definition.[3][4]
The Lewis number can also be expressed in terms of the Prandtl number (Pr) and the Schmidt number (Sc):[5]
It is named after
MIT. Some workers in the field of combustion assume (incorrectly) that the Lewis number was named for Bernard Lewis (1899–1993), who for many years was a major figure in the field of combustion research[citation needed
].
Literature
- Bird, R.B. (Fall 2001). "Who Was Who in Transport Phenomena". Chemical Engineering Education. 35 (4). Retrieved 20 May 2021.
- ISBN 0-471-38650-2.
References
- ^ "Lewis number". tec-science. 10 May 2020. Retrieved 25 June 2020.
- IUPAC. p. 82.
- Von Karman Institute. Von Karman Institute for Fluid Dynamics Lecture Series Hypersonic Entry and Cruise Vehicles – via Defence Technical Information Centre.
- OCLC 21874250.
- ^ Guruge, Amila Ruwan (2022-02-10). "What is the Lewis Number". Chemical and Process Engineering. Retrieved 2022-12-20.
- .
- ^ Klinkenberg, A.; Mooy, H. H. (1948). "Dimensionless Groups in Fluid Friction, Heat, and Material Transfer". Chemical Engineering Progress. 44 (1): 17–36.