Analysis of boundary conditions

It is not unusual that the boundary conditions consider changes at the interface, in the case of heterogeneous systems, where these conditions are different. Let us consider only the boundary conditions for the mass balance where there is change phase, neglecting the radial flow. Thus, we can say that the molar flows in the interface are equals, i.e.  

It is known that the diffusion and dispersion coefficients are different in z = 0+ and z = 0 . Similarly z = L in another part of the reactor. If there is no difference, the reactor behaves like a piston, i.e., ideal behavior. Therefore, the above equation is simplified as  

But the flow heterophasic or even with nonuniform flow (laminar, turbulent, or particulate) one can assume that in z = 0 . The dispersion coefficient is negligible, but not in z = 0+. In that sense, boundary condition will be  

Therefore, when z = 0+ the conversion is nonzero. There are mixing effects on the input of the reactor. 

When Pe = 0 (s = oo), we get the ideal tank reactor (CSTR). Thus  

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Analysis of Boundary Conditions at the Symmetry Plane Via the Central Difference... 

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