Viscous Flow and the Transition Region

The viscous flow of a binary mixture which is fully in the continuum regime does not affect the concentration of both gases and relation (9.2) applies for the mixture as for a single gas with the mixture viscosity ti(x) of the mixture with a constant mole fraction x. 

The viscous flow of each species i of the mixture equals the total flow t multiplied by the mole fraction x (proportional to the partial pressure p)  

9 TRANSPORT AND SEPARATION PROPERTIES OE MEMBRANES WITH GASES AND VAPOURS 

The transition region ofKnudsen and continuum diffusion or viscous flow 

Two important cases must be considered (i) non-isobaric, and (ii) isobaric situations. The non-isobaric situation will first be discussed. 

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