A	water permeability, m/(s bar)
B	salt permeability, m/s
C	salt concentration, mol/L
D	fluid diffusion coefficient, m2/s
E	power density, W/m2
Js	solute transport rate, kg/m2s
Jw	water flux, m/s
Jw ,∞	water flux at kd = kf→∞, m/s
k	diffusive mass transfer coefficient, m/s
P	hydraulic pressure, bar
R	rejection coefficient
S	structural parameter, m
S ∞	structural parameter without external mass transfer resistances, m
v	convective fluid velocity perpendicular to the membrane surface, m/s
Greek
β	diffusive plus convective transport coefficient, m/s
π	osmotic pressure, bar
δ	thickness of the fluid boundary layer, m
ε	porosity,
τ	tortuosity,
ΔCm	concentration difference on the active layer, mol/L
ΔP	hydraulic pressure difference, bar
Δπ	effective osmotic pressure difference on the active layer, bar
Subscripts
b	bulk solute concentration
d	draw solution
f	feed solution
m	membrane active layer
i	interface between selective and the support layer (with P, π, β, or C)
p	permeate
s	support layer (with S, τ, ε, δ, or D)
sp	external interface of the support layer
w	water