The Lewis number (Le) is a 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]
\( {\displaystyle \mathrm {Le} ={\frac {\alpha }{D}}={\frac {\lambda }{\rho D_{im}c_{p}}}} \)
where \( \alpha \) is the thermal diffusivity and D the mass diffusivity, \( \lambda \) the thermal conductivity, \( \rho \) the density, \( {\displaystyle D_{im}} \) the mixture-averaged diffusion coefficient, and \( c_{p} \) the specific heat capacity at constant pressure.
The Lewis number can also be expressed in terms of the Prandtl number and the Schmidt number :
\( {\displaystyle \mathrm {Le} ={\frac {\mathrm {Sc} }{\mathrm {Pr} }}}. \)
It is named after Warren K. Lewis (1882–1975),[3][4] who was the first head of the Chemical Engineering Department at 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.
Literature
Bird, R.B. (2001). "Who Was Who in Transport Phenomena". Retrieved 2008-02-08.
Incropera, F. P.; DeWitt, D. P. (1996). Heat and Mass Transfer, fifth edition. New York, NY: Wiley. ISBN 0-471-38650-2.
References
tec-science (2020-05-10). "Lewis number". tec-science. Retrieved 2020-06-25.
E.R. Cohen et al. "Quantities, Units and Symbols in Physical Chemistry", IUPAC Green Book 3rd Ed., IUPAC & RSC Publishing, 2007
W. K. Lewis: The Evaporation of a Liquid Into a Gas In: Transactions of the American Society of Mechanical Engineers, No. 1849, 1922, p. 325-340.
A. Klinkenberg, H. H. Mooy: Dimensionless Groups in Fluid Friction, Heat, and Material Transfer In: Chemical Engineering Progress, Vol. 44, No. 1, 1948, p. 17-36.
See also
vte
Dimensionless numbers in fluid mechanics
Archimedes Atwood Bagnold Bejan Biot Bond Brinkman Capillary Cauchy Chandrasekhar Damköhler Darcy Dean Deborah Dukhin Eckert Ekman Eötvös Euler Froude Galilei Graetz Grashof Görtler Hagen Iribarren Kapitza Keulegan–Carpenter Knudsen Laplace Lewis Mach Marangoni Morton Nusselt Ohnesorge Péclet Prandtl
magnetic turbulent Rayleigh Reynolds
magnetic Richardson Roshko Rossby Rouse Schmidt Scruton Sherwood Shields Stanton Stokes Strouhal Stuart Suratman Taylor Ursell Weber Weissenberg Womersley
Hellenica World - Scientific Library
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