# Lewis number

(Difference between revisions)
 Revision as of 16:50, 17 November 2005 (view source)Salva (Talk | contribs)m← Older edit Revision as of 16:52, 17 November 2005 (view source)Salva (Talk | contribs) mNewer edit → Line 6: Line 6: can be expressed as can be expressed as :$:[itex] - Le_k = \frac{D_{th}}{ D_k} + Le_k \equiv \frac{D_{th}}{ D_k}$ [/itex] which is the ratio of the heat diffusion speed to the diffusion speed of species $k$. which is the ratio of the heat diffusion speed to the diffusion speed of species $k$. In many combustion models, all species are assumed to diffuse at the same speed and therefore In many combustion models, all species are assumed to diffuse at the same speed and therefore - $Le \equiv 1$ + $Le = 1$ [[Category:Dimensionless parameters]] [[Category:Dimensionless parameters]]

## Revision as of 16:52, 17 November 2005

The Lewis number for a given species $k$ is

$Le_k \equiv \frac{\lambda}{\rho C_p D_k}$

Denoting $D_{th}= \lambda / \rho C_p$ the heat diffusivity coefficient the Lewis number can be expressed as

$Le_k \equiv \frac{D_{th}}{ D_k}$

which is the ratio of the heat diffusion speed to the diffusion speed of species $k$.

In many combustion models, all species are assumed to diffuse at the same speed and therefore $Le = 1$