5 Flux Equations

With Equation 14 now understood in the context of conservation of momentum, we replace partial pressure, pA, with the more familiar molar concentration, CA and use Equation 10 to replace JA and obtain Equation 22.

\displaystyle -D\frac{dC_{A}}{dl}=\left ( x_{B}N_{A}^{D}-x_{A}N_{B}^{D} \right )+\frac{D}{D_{A}^{K}}N_{A}^{D} (22)

Equation 22 and the corresponding equation for species B (interchange the subscripts) apply in both the molecular and transition regimes under both isobaric and non-isobaric conditions. The total diffusive fluxes are expressed by Equations 20 and 21 for the non-isobaric and isobaric condition, respectively.


Flux Equations for Gas Diffusion in Porous Media Copyright © 2021 by David B. McWhorter. All Rights Reserved.