# Diffusion coefficients for binary gas systems at low pressure

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

#### 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 cm^{2}/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.