Fluxes with an Effective Diffusivity Model

Example 6.3.1 Computation ofthe Fluxes with an Effective Diffusivity Model 

Let us illustrate the calculation of the effective diffusivity and the molar fluxes for the conditions existing at the start of the two bulb diffusion cell experiment of Duncan and Toor discussed in Examples 5.3.1 and 5.4.1. The components are hydrogen (1), nitrogen (2), and carbon dioxide (3) and the values of the diffusion coefficients of the three binary pairs at 35.2° C and 1-atm pressure were 

SOLUTION Strictly speaking none of the limiting cases of the two general expressions (Eqs. 6.1.10-6.1.14) applies to the two bulb diffusion cell. Nevertheless, we will proceed to calculate and the molar fluxes through the capillary tube using Wilke s method (Eq. 6.1.14). 

The mole fractions at equilibrium are used in the evaluation of the effective diffusivities (from Example 5.4.1) 

The effective diffusivities are computed from Wilke s Eq. 6.1.14 as follows  

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