A	membrane area [m2]
B	constant in Model I, II and III
c	total molar concentration [mol/mol]
ci	concentration of component i [mol/m3]
Di	diffusion coefficient [m2/h]
D i0	diffusion coefficient of component i [ kmol/m2 h]
$\overline{D_i}$	transport coefficient of component i [kmol/m2 h]
${\overline{D}}_{i,exp}$	modified transport coefficient of component i in Model I, II and III [kmol/m2 h]
$\overline{D_i^{\ast }}$	relative transport coefficient of component i [kmol/m2 h]
Ei	activation energy of component i [kJ/mol]
f i0	fugacity of pure i component [mbar, kPa]
f i1	fugacity of component i in the feed side [mbar, kPa]
f i3	fugacity of component i in the permeate side [mbar, kPa]
J	total flux [kg/m2h]
Ji	partial flux [kg/m2h]
L	distance of diffusion [m]
ni	weight of component i [mol]
pi0	vapour pressure of pure i component [bar, kPa]
p i1	partial pressure of component i in the feed side [bar, kPa]
p i2	partial pressure of component i between the two layers of the membrane [bar, kPa]
p i3	partial pressure of component i in the permeate side [bar, kPa]
p 3	pressure on the permeate side [bar, kPa]
Q 0	permeability of the porous supporting layer of the membrane [kmol/m2 h bar]
R	gas constant [kJ/kmol K]
t	time [s, h]
T	temperature [K, °C]
T*	reference temperature: 273 K = 20 °C
wF	feed concentration of component i [wt%]
x i1	mol fraction of component i in the feed [mol/mol]
yi	mol fraction of component i in the permeate [mol/mol]
Greek letters:
βij	selectivity for component i and j
δ	thickness of the membrane [m]
γ i1	activity coefficient of component i in the feed
γ i3	activity coefficient of component i in the permeate
$\overline{{\gamma }_i}$	average activity coefficient of component i