Am	active membrane area (m2)
Cp	non-condensable heat capacity (J/mol/K)
Cpf	feed stream heat capacity (J/kg/K)
Cp,g	water (vapour) heat capacity (J/kg/K)
Cp,l	water (liquid) heat capacity (J/kg/K)
D	pipe diameter (m)
DH	hydraulic diameter (m)
ev	friction loss factor (dimensionless)
Ef	feed pump electrical energy (J)
Er	latent heat of condensation (J)
ETotal	overall energy requirement (J)
Ev	vacuum pump electrical energy (J)
f	Darcy’s friction factor (dimensionless)
J	permeate flux (kg/m2·h)
L	channel length (m)
mf	mass flow rate of feed stream (kg/s)
mnc	non-condensable flow rate (mol/s)
mp	mass flow rate of permeate (kg/s)
MW	molecular weight of non-condensable gases (g/mol)
Pin	vacuum pump inlet pressure (Pa)
Pout	vacuum pump outlet pressure (Pa)
Qc	permeate stream cooling energy (J)
Qh	feed stream heating energy (J)
Q init	one-off initial heating energy (J)
R	universal gas constant (J/mol/K)
Re	Reynold’s number (dimensionless)
Tfi	temperature of feed inlet (K)
Tfo	temperature of feed outlet (K)
Tin	temperature of vacuum pump inlet stream (K)
Tpc	condensation temperature of permeate (K)
Tpi	temperature of permeate inlet (K)
Tpo	temperature of permeate outlet (K)
TRes	temperature of feed reservoir (K)
Tout	temperature of vacuum pump outlet stream (K)
u	linear velocity of feed stream (m/s)
Vf	volumetric flow rate of feed stream (m3/s)
ΔPf	pressure drop of pipe due to friction (Pa)
ε	surface roughness (m)
β	smaller cross section/larger cross section (dimensionless)
γ	adiabatic expansion coefficient (dimensionless)
λ	latent heat of condensation of water vapour (J/kg)
ρ	fluid density (kg/m3)
μ	fluid viscosity (Pa.s)
η p1	feed pump efficiency (%)
η p2	vacuum pump efficiency (%)
Subscripts
fi	feed inlet
fo	feed outlet
pi	permeate inlet
po	permeate outlet