Boundary Condition for the Radiative Transfer Equation
For gray walls, corresponding to opaque surfaces reflecting diffusively and emitting, the radiative intensity
I
(Ω)
entering participating media along the
Ω
direction is
where
(4-92)
•
Equation 4-91
is the blackbody radiation intensity and
n
r
is the refractive index
•
ε
is the surface emissivity, which is in the range [
0
,
1
]
•
1
− ε
is the diffusive reflectivity
•
n
is the outward normal vector
•
q
r,out
is the heat flux striking the wall:
For black walls
ε =
1
. Thus
I
(Ω) =
I
b
(
T
)
.
