# Diffusion coefficients for binary gas systems at low pressure

Estimated using the empirical correlation of Wilke and Lee (1955).

K
bar
g mol-1
g mol-1
cm3 mol-1
cm3 mol-1
K
K
cm2 s-1

#### Notes

This calculator uses the Wilke and Lee empirical correlation to estimate the diffusion coefficients of binary gas systems at low pressure.

$D_\mathrm{12} \: \mathrm{[cm^2 \: s^{-1}]} = \frac{[3.03 - (0.98 / M_\mathrm{12}^{1/2})] (10^{-3}) T^{3/2}}{P M_\mathrm{12}^{1/2} \sigma_\mathrm{12}^{2} \Omega_\mathrm{D}}$

$M_\mathrm{12} = \frac{2}{1/M_1 + 1/M_2}$

where $$D_\mathrm{12}$$ is the binary diffusion coefficient in cm2/s, $$T$$ is the temperature in K, $$P$$ is pressure in bar, $$M_\mathrm{A}$$ and $$M_\mathrm{B}$$ are the molecular weights of components 1 and 2 in g/mol, $$\sigma_\mathrm{12}$$ is the scale parameter, and $$\Omega_\mathrm{D}$$ is a function with tabulated parameters.

Values of the diffusion coefficient estimated using Wilke and Lee correlation generally agree with experimental values to within 5 to 10 %, although discrepancies of more than 20 % are possible.

#### References

B.E. Poling, J.M. Prausnitz, J.P. O'Connell. Properties of Gases and Liquids, 5th Edition, McGraw-Hill, 2001.