Chapter 11

Example 11.1: Prediction of Binary Gas Diffusivities

Fuller, Schettler, and Giddings Correlation

One of the most common equations used in predicting binary gas diffusivities owing to its theoretical foundations, is the Hirschfelder-Bird-Spotz equation. A more recent empirical correlation has been developed by Fuller. Fuller used 308 experimental values of the diffusivities of various gases to determine the coefficients a, b, c, d, g, and f equation Using a nonlinear least-squares analysis, the empirical equation that gives the smallest standard deviation is where P = total pressure, atm Mi = molecular weight DAB = diffusivity, cm2/s T = temperature, K ΣVi = Sum of the diffusion volume for component i, as given in Table D-1

See R. B. Bird, W. E. Stewart, and E. N. Lightfoot, Transport Phenomena (New York: Wiley, 1960), p. 511.

E. N. Fuller, P. D. Schettler, and J. C. Giddings, Ind. Eng. Chem. 58(5), 19 (1966).
Several other equations for predicting diffusion coefficients can be found in R. C. Rcid, J. M. Prausnitz and T. K Sherwood, The Properties of Gases and Liquids 3rd ed. (New York: McGraw-Hill, 1977), Chap 11. Example

Calculate the diffusivity of CS2 in air at 35°C at 1 atm

Solution For air:

1. VA = 20.1.
2. 2. Molecular weight = 29.0.

For CS2, from Table D-1:

 C = 16.5 C = 16.5 S = 17.0 S2 = 34.0 total 50.5

1. VCS2 = 50.5
2. Molecular weight = 76. Back to Chapter 11