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Chapter 11
Fundamentals of Thermal Radiation
Atmospheric and Solar Radiation
1150C
The solar constant represents the rate at which solar energy is incident on a surface normal to sun's
rays at the outer edge of the atmosphere when the earth is at its mean distance from the sun. It value is
. The solar constant is used to estimate the effective surface temperature of the sun from
the requirement that
2
W/m
1353
=
s
G
4
2
1
2
)
4
(
)
4
(
sun
s
T
r
G
L
σπ
π
=
where L is the mean distance between the sun and the earth and r is the
radius of the sun. If the distance between the earth and the sun doubled,
the value of
drops to onefourth since
G
s
SUN
Earth
L
r
(4
π
L
2
)
G
s
4
π
r
2
(
σ
T
sun
4
)
4
2
2
2
4
2
2
2
)
4
(
16
)
4
(
)
2
(
4
sun
s
sun
s
T
r
G
L
T
r
G
L
=
=
4
G
G
s1
s2
=
⎯→
⎯
=
1
2
2
2
4
16
s
s
G
L
G
L
1151C
The amount of solar radiation incident on earth will decrease by a factor of
Reduction factor
==
=
σ
T
T
sun
sun new
4
4
4
4
5762
2000
68 9
,
.
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This note was uploaded on 01/24/2012 for the course PHY 4803 taught by Professor Dr.danielarenas during the Fall '10 term at UNF.
 Fall '10
 Dr.DanielArenas
 Thermodynamics, Energy, Mass, Radiation

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