$a_w$	Water activity in NaCl solution
$Cp,c$	Heat capacity of cold fluid (J kg−1K−1)
$Cp,h$	Heat capacity of hot fluid (J kg−1K−1)
$c_m$	Mass transfer coefficient of membrane (kg m−2 Pa−1 s−1)
$D_h$	Equivalent hydraulic diameter of empty channel (m)
$D_{h,h}$	Equivalent hydraulic diameter of hot side (m)
$D_{h,c}$	Equivalent hydraulic diameter of cold side (m)
$d$	Height of flow channel (m)
$Dp$	Height of 3D printed turbulence promoter (m)
$E$	Deviation of experimental results from the theoretical predictions
$f_F$	Fanning friction factor
$h_c$	Convection coefficient of cold fluid (W m−2 K−1)
$h_h$	Convection coefficient of hot fluid (W m−2 K−1)
$H_i$	Hydraulic dissipate energy (J kg−1), $i=promoter,empty$
$H_m$	Thermal convection coefficient of membrane (W m−2 K−1)
$I_E$	Raised percentage of permeate flux
$I_P$	Raised percentage of hydraulic loss
$L$	Axial distance (m)
$k$	Thermal conductivity coefficient of hot saline feed (W m−1 K−1)
$kg$	Thermal conductivity coefficient of the vapor in the membrane pore (W m−1 K−1)
$ks$	Thermal conductivity coefficient of the solid membrane material (W m−1 K−1)
$\ell wf$	Friction loss of conduits (J kg−1)
$M_W$	Molecular weight of water (kg mol−1)
$\dot{m}$	Mass flow rate (kg s−1)
$N^{″}$	Permeate flux (kg m−2 h−1)
$N{u}_{}$	Nusselt number
$N{u}^p$	Nusselt number of the turbulence promoter
$N{u}_{lam}$	Dimensionless Nusselt number for laminar flow
np	Number of promoters per row
$P$	Pressure (Pa)
$P_1^{sat}$	Saturation vapor pressure in the cold feed flow side (Pa)
$P_2^{sat}$	Saturation vapor pressure in the hot feed flow side (Pa)
$P_w{}^{sat}$	Saturated vapor pressure of pure water (Pa)
$\mathrm{Pr}$	Prandtl number
${q^{″}}_{}$	Heat transfer rate (W/m2)
${q^{″}}_c$	Heat transfer rate between cooling plate and cold fluid (W/m2)
${q^{″}}_h$	Heat transfer rate between hot fluid and membrane surface (W/m2)
${q^{″}}_m$	Heat transfer rate between membrane surface of hot fluid and air gap (W/m2)
$Q$	Volumetric flow rate (m3 s−1)
$R$	Gas constant (8.314 J mol−1 K−1)
Re	Reynolds number
$S{h}_{lam}$	Dimensionless Schmidt number for laminar flow
$S{N}^{″}$	The precision index of an experimental measurements of permeate flux (kg m−2 h−1)
$S\overline{N^{″}}$	The mean value of $S{N}^{″}$(kg m−2 h−1)
$T$	Temperature (°C)
$T_m$	Mean temperature in membrane (°C)
$\overline{v}$	Average velocity (m s−1)
$Wp$	Average equivalent width of 3D printed turbulence promoters
${\left|Y_m\right|}_{\ell n}$	Natural log mean mole fraction of air
$x_{NaCl}$	Liquid mole fraction of NaCl
$x_w$	Liquid mole fraction of water
$z$	Axial coordinate along flow direction (m)
Greek letters
${\alpha }^p$	Heat-transfer enhancement factor
$\beta$	Aspect ratio of the channel
$\Delta P$	Vapor pressure difference of membrane (Pa)
${\delta }_m$	Thickness of membrane (µm)
$\epsilon$	Membrane porosity
$\lambda$	Latent heat of water (J/kg)
$\mu$	Fluid viscosity (kg s−1 m−1)
$\rho$	Density (kg m−3)
${\tau }_{temp}$	Temperature polarization coefficients
Subscripts
1	Membrane surface on cold feed side
2	Membrane surface on hot feed side
h	In the hot feed flow channel
c	In the cold feed flow channel
promoter	Inserting turbulence promoters
empty	Inserting nylon fiber as supporters
exp	Experimental results
in	Inlet
lam	Empty channel
out	Outlet
theo	Theoretical predictions
Superscripts
p	The channel with inserting turbulence promoters