Quite a number of different correlations and methods have been proposed over the years but the one semi-empirical equation from Chen and Othmer (J. Chem. Eng. Data 7 (1962), 37) is preferable because
• It is Simple
• Sufficiently Accurate in most of the cases
• Availability of inputs required
According to Chen and Othmer the diffusion coefficient D1,2 for the diffusion of gas 1 in gas 2 at moderate pressures can be calculated from the following equation:
The equation is very simple to use & is given below.
D(1,2) = 6.04 x 10 ^ -9 x (T^1.81 / p) x ( (M1+M2)/M1/M2)^0.5 x (Tc1 x Tc2)^0.1405
x (Vc1 ^0.4 + Vc2 ^0.4)^2
M1, M2 = Mol Wt of both components
Tc1, Tc2 = Critical Temp in K
Vc1, Vc2 = Critical Volume in Cm3/mol
P = System Pressure in bar
T = Temp in K
D1,2 = Diffusion Coeff in M2/sec
I hope it is useful for many of you.