6 Estimation of Diffusion Coefficients

The diffusion coefficients appearing in the above developments are macroscopic parameters. Macroscopic values for these parameters are automatically obtained when measured by application of macroscopic equations. The estimation of Knudsen diffusion coefficients by the method described in this section is an example of this circumstance. On the other hand, values for molecular diffusion coefficients tabulated in handbooks are not macroscopic and must be modified to account for obstructions present in the diffusion space.


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