Chapter 11
Fundamentals of Thermal Radiation
1131
A surface is subjected to radiation emitted by another surface. The solid angle subtended and the rate
at which emitted radiation is received are to be determined.
Assumptions
1
Surface
A
1
emits diffusely as a blackbody.
2
Both
A
1
and
A
2
can be approximated as
differential surfaces since both are very small compared to the square of the distance between them.
Analysis
Approximating both
A
1
and
A
2
as differential
surfaces, the solid angle subtended by
A
2
when viewed from
A
1
can be determined from Eq. 1112 to be
A
1
= 4 cm
2
T
1
= 600 K
θ
2
= 60
°
r
= 80 cm
1
= 45
°
A
2
= 4 cm
2
sr
10
3.125
4
−
−
×
=
°
=
θ
=
≅
ω
2
2
2
2
2
2
2
,
1
2
cm)
80
(
60
cos
)
cm
4
(
cos
r
A
r
A
n
since the normal of
A
2
makes 60
°
with the direction of viewing.
Note that solid angle subtended by
A
2
would be maximum if
A
2
were positioned normal to the direction of viewing. Also, the
point of viewing on
A
1
is taken to be a point in the middle, but
This is the end of the preview.
Sign up
to
access the rest of the document.
 Fall '10
 Dr.DanielArenas
 Thermodynamics, Energy, Mass, Radiation, Surface, Thermal radiation, Solid angle

Click to edit the document details