c	Specific heat capacity, J·kg−1·K−1
d	Size parameter
E	Foam expansion ratio
f	Volume fraction of particle
H	Thickness of the foam layer, cm
mf	Total mass of the gel foam layer, kg
Q	Efficiency factor
qr	Radiant heating flux, kW·m−2
T	Temperature, K
V	Volume, m3
v	Velocity, m·s−1
Greek symbols
γ	Structure coefficient
θ	Mass fraction of the gas, liquid, or solid phase, %
κ	Scattering or absorption coefficient, m−1
$\Lambda$	Mean free path of phonon, m
λ	Thermal conductivity, W·m−1·K−1
ρ	Density, kg·m−3
$\tau$	Heating time, s
$\phi$	Volume fraction of gas, liquid, or solid phase
Subscripts
bulk	Body phase
$f$	Foam layer
g	Gas phase
l	Liquid phase
p	Particle phase
r	Radiation
s	Solid phase
sh,lo	Lower surface of shell
sh,up	Upper surface of shell
strut	Plateau border of foam cell
wall	Wall of foam cell