Contents

Lewis number

${\displaystyle \mathrm {Le} ={\frac {\alpha }{D}}={\frac {\lambda }{\rho D_{im}c_{p}}}}$.

where:

• α is the thermal diffusivity,
• D is the mass diffusivity,
• λ is the thermal conductivity,
• ρ is the density,
• D_im is the mixture-averaged diffusion coefficient,
• c_p 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]

${\displaystyle \mathrm {Le} ={\frac {\mathrm {Sc} }{\mathrm {Pr} }}}$

It is named after Warren K. Lewis (1882–1975),^[6][7] 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^{[citation needed]}.

Literature[edit]

• Bird, R.B. (Fall 2001). "Who Was Who in Transport Phenomena". Chemical Engineering Education. 35 (4). Retrieved 20 May 2021.
• Incropera, F. P.; DeWitt, D. P. (1996). Heat and Mass Transfer, fifth edition. New York, NY: Wiley. ISBN 0-471-38650-2.

References[edit]