Nomenclature
$a_n, b_n$	Mie coefficients
$D$	diameter of the fiber, m
$f$	porosity
$g$	asymmetry factor
$h_c$	non-radiative heat coefficient, W m−2 K−1
$h_{fg}$	enthalpy of vapor, kJ kg−1
$I_B\left(T,\lambda \right)$	the spectral radiance of a black body, W
$I_{sun}\left(\lambda \right)$	solar illumination, W m−2
$k$	thermal conductivity, W m−1 K−1
$P_{atm}$	absorbed IR radiation, W m−2
$P_{cond+conv}$	non-radiation heat transfer, W m−2
$P_{eva}$	evaporative cooling power, W m−2
$P_{net}$	net passive cooling power, W m−2
$P_r$	emitted IR radiation, W m−2
$P_{rad}$	radiative cooling power, W m−2
$P_{sun}$	solar intensity absorbed by radiative paints, W m−2
$Q_{sca}$	scattering efficiency
$R_{aer}$	mass transfer resistance, s m−1
$T_c$	cooling temperature, K
$t$	thickness, m
$x$	size parameter
Greek symbols
$\alpha$	spectral and angular solar absorptivity
$\lambda$	length of incident wave, m
${\rho }_h$	density of the hydrogel layer, kg m−3
${\rho }_v$	vapor mass density, g kg−1
$\sigma$	scattering coefficient of the fiber coma
${\sigma }_r$	spectral and angular emissivity in the infrared region
$\mathsf{\tau }$	cooling time, h
$\mathsf{\Omega }$	solid angel for scattering
$\mathsf{\omega }$	water mass fraction of the hydrogel
Superscripts and subscripts
aer	aerogel
amb	ambient
atm	atmospheric
ext	external
g	gaseous phase
h	hydrogel
r	radiation
s	solid phase