Symbols
$Af$	side area of the fins (mm2)
$Ar$	surface area of the substrate (mm2)
$B$	mass transfer coefficient of the MD process (kg/m2/Pa/s)
$H_{fin}$	height of the fins (mm)
$J$	permeate flux (kg/m2/h)
$L_{fin}$	length of the fins (mm)
$N$	number of the fin
$P$	saturated vapor pressure
$R_{\mathrm{s}}$	salt rejection ratio
$t$	temperature (°C)
$u$	velocity (m/s)
$W_{fin}$	width of the fins (mm)
Greek letters
$\delta$	thickness (m)
${\delta }_{base}$	thickness of the substrate (mm)
${\delta }_{ch}$	the fin pitch (mm)
${\delta }_{fin,1}$	thickness of the inner fin (mm)
${\delta }_{fin,2}$	thickness of the outer fin (mm)
$\lambda$	thermal conductivity (W/m/K)
$\sigma$	specific correction value
$\phi$	temperature correction coefficient
$\omega$	surface area ratio of the condensing plate
Subscripts
a	cooling air
c	cooling side
cp	condensing plate
f	feed side
fin	rectangular straight fins
w	cooling water
Abbreviations
ACMD	air-cooled membrane distillation
GMD	gap membrane distillation
LEP	liquid entry pressure
MD	membrane distillation
PMMA	polymethyl methacrylate
PTFE	polytetrafluoroethylene
RO	reverse osmosis
SEM	scanning electron microscope
WCA	water contact angle
WCMD	water-cooled membrane distillation