a	Molecular radius, Solute radius (m)
DAB	Diffusive coefficient in a homogeneous fluid, usually used for water at 37 ℃ (m2/s)
$D_m$	Diffusive coefficient in membrane (m2/s)
K	Partition coefficient (–)
$\overline{L}$	Membrane thickness (m)
$P_m$	Permeability in membrane (m/s)
r	Pore radius (m)
Greek letters
ε	Surface porosity (–)
τ	Membrane tortuosity (–)
${\omega }_r$	Hindered diffusion parameter (–)
Subscripts/superscripts
m	Membrane