11 Notation

Subscript denoting species A A
Subscript denoting species B B
Klinkenberg parameter (F/L2) b
Moles of gas per unit volume (moles/L3) C
Moles of species i per unit volume (moles/L3) Ci
Effective molecular diffusion coefficient (L2/T) D
Molecular diffusion coefficient (L2/T) Dm
Knudsen diffusion coefficient for species i (L2/T) D_{i}^{K}
Equimolar flux of species i (moles/L2T) Ji
Intrinsic permeability (L2) k
Permeability to gas or effective gas permeability (L2) kg
Apparent gas permeability (L2) kga
Knudsen number Kn
Coordinate tangent to path of motion (L) l
Molecular weight of specie i Mi
Molecular mass of specie i mi
Porosity n
Number of molecules per unit volume (L-3) ñ
Mole flux of species i (moles/L2T) Ni
Mole flux of species i due to diffusion (moles/L2T) N_{i}^{D}
Diffusive flux for the gas as a whole (non-equimolar flux) (moles/L2T) ND
Mole flux of gas due to viscous flow (moles/L2T) Nv
Mole flux of species i due to advection in viscous flow (moles/L2T) N_{i}^{v}
Pressure (F/L2) p
Mean pressure (F/L2) \bar{p}
Partial pressure of species i pi
Ideal gas law constant (FL)/(moles temperature) R
Absolute temperature T
Volume flux (L/T) v
Mean speed of species i molecules (L/T) \bar{v}_i
Mole fraction of species i xi
Vertical coordinate (L) z
Volume of gas per unit bulk volume θg
Mean free path length (L) λ
Characteristic pore dimension (L) λp
Molecular diameter (L) σ
Dynamic viscosity (FT/L2) μ
Tortuosity τ


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