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Chapter 15
Steady Heat Conduction
358
A composite wall consists of several horizontal and vertical layers. The left and right surfaces of the
wall are maintained at uniform temperatures. The rate of heat transfer through the wall, the interface
temperatures, and the temperature drop across the section F are to be determined.
Assumptions
1
Heat transfer is steady since there is no indication of change with time.
2
Heat transfer
through the wall is onedimensional.
3
Thermal conductivities are constant.
4
Thermal contact resistances
at the interfaces
are to be considered.
Properties
The thermal conductivities of various materials used are given to be
k
A
=
k
F
= 2,
k
B
= 8,
k
B
C
= 20,
k
D
= 15, and
k
E
= 35 W/m
⋅
°C.
Analysis
The
representative surface area is
A
=
×
=
012 1 012
..
m
2
R
1
R
3
R
2
R
4
R
5
R
6
R
7
R
8
(
a
) The thermal resistance network and the individual thermal resistances are
C/W
16
.
0
)
m
04
.
0
(
C)
W/m.
8
(
m
05
.
0
C/W
06
.
0
)
m
04
.
0
(
C)
W/m.
20
(
m
05
.
0
C/W
04
.
0
)
m
12
.
0
(
C)
W/m.
2
(
m
01
.
0
2
3
2
4
2
2
1
°
=
°
=
⎟
⎠
⎞
⎜
⎝
⎛
=
=
°
=
°
=
⎟
⎠
⎞
⎜
⎝
⎛
=
=
=
°
=
°
=
⎟
⎠
⎞
⎜
⎝
⎛
=
=
B
B
C
C
A
A
kA
L
R
R
kA
L
R
R
R
kA
L
R
R
C/W
001
.
0
m
12
.
0
C/W
m
00012
.
0
C/W
25
.
0
)
m
12
.
0
(
C)
W/m.
2
(
m
06
.
0
C/W
05
.
0
)
m
06
.
0
(
C)
W/m.
35
(
m
1
.
0
C/W
11
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This note was uploaded on 01/14/2012 for the course PHY 4803 taught by Professor Dr.danielarenas during the Fall '10 term at UNF.
 Fall '10
 Dr.DanielArenas
 Thermodynamics, Mass, Heat

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