Chapter 11
Fundamentals of Thermal Radiation
1148E
A spherical ball emits radiation at a certain rate. The average
emissivity of the ball is to be determined at the given temperature.
Ball
T
=950 R
D
= 5 in
Analysis
The surface area of the ball is
AD
==
=
ππ
22
12
05454
(5/
)
.
ft
ft
2
Then the average emissivity of the ball at this temperature is
determined to be
0.158
=
⋅
×
=
=
⎯→
⎯
=
4
4
2
8
2
4
4
R)
950
)(
R
Btu/h.ft
10
)(0.1714
ft
(0.5454
Btu/h
120
T
A
E
T
A
E
σ
εσ
ε
1149
The variation of transmissivity of a glass is given. The average transmissivity of the pane at two
temperatures and the amount of solar radiation transmitted through the pane are to be determined.
Analysis
For
T=
5800 K:
λμ
μ
λ
11
03
0035
1
T
=⎯
→
This is the end of the preview. Sign up
to
access the rest of the document.
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, Mass, Radiation

Click to edit the document details