$f$	friction factor [-]	$La$	the Laplace number [-]
$h$	enthalpy [J/kg]		$La=\sqrt{\frac{\sigma }{g\left({\rho }_l-{\rho }_g\right)D_h^2}}$
$h_{lg}$	latent heat of vaporization [J/kg]
$j_g$	superficial gas flux [m/s]	$\mathrm{MAE}$	mean absolute error
$\dot{m}$	mass flow rate [kg/s]	$N$	number of experimental data points
$p$	pressure [Pa]	$\dot{P}$	heating power of the preheating section [W]
$v$	flow velocity [m/s]
$x$	thermodynamic equilibrium vapor quality [-]	$\dot{Q}$	heating power of the test-section [W]
		$Re$	the Reynolds number [-]
$z$	coordinate along microchannel [mm]	$W_{ch}$	channel width [mm]
$C$	the Chisholm parameter [-]	$We$	the Weber number [-]
$C_c$	contraction coefficient [-]		$We=\frac{\rho v^2{D}_h}{\sigma }$
$D_h$	hydraulic diameter [mm]
$G$	mass velocity [kg/(m2·s)]	$X$	the Martinelli parameter [-]
$H_{ch}$	channel depth [mm]		$X^2={\left(\frac{dP}{dz}\right)}_l/{\left(\frac{dP}{dz}\right)}_g$
$L$	channel length [mm]
Greek Symbols
$\alpha$	void fraction [-]	${\sigma }_e$	expansion area ratio [-]
$\beta$	channel aspect ratio [-]	$\Delta$	difference [-]
$\rho$	density [kg/m3]	$\varphi$	two-phase pressure drop
${\rho }_{tp}$	mixture density [kg/m3]		multiplier [-]
${\sigma }_c$	contraction area ratio [-]
Subscripts
$a$	accelerational	$lo$	liquid only
$ave$	average	$out$	microchannel outlet
$c$	contraction	$pre$	predicted
$e$	expansion	$tot$	total
$exp$	experimental	$tp$	two-phase
$fric$	frictional	$tt$	turbulent liquid-turbulent vapor
$g$	saturated vapor	$tv$	turbulent liquid-laminar vapor
$in$	microchannel inlet	$vt$	laminar liquid-turbulent vapor
$l$	saturated liquid	$vv$	laminar liquid-laminar vapor