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Problem Set #2
Due Wednesday 4/14
1.
The planar, composite wall shown below consists of common building brick (k=0.72W/mK) and
fiberboard sheathing (k=0.06 W/mK).
The wall is in contact with air on both sides, with the
temperatures and heat transfer coefficients shown.
a.
Find the total thermal resistance to heat transfer through the wall.
b.
Find the overall heat transfer coefficient.
c.
Calculate the heat flux through the wall.
d.
Calculate the temperatures of the air/solid interfaces for both the brick and the sheathing.
T
∞
,1
=
45
o
C
h
1
=
25
W
m
2
K
T
3
T
1
T
2
T
∞
,2
=
25
o
C
h
1
=
8
W
m
2
K
sheathing
2 cm
10 cm
brick
air
air
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An insulated steel pipe carries steam at 180
°
C in a room where the air temperature is 25
°
C.
Calculate the heat loss per meter of pipe length, as shown below.
The physical parameters are given
by
r
1
=
2cm, r
2
=
2.5cm, r
3
=
4.0cm
k
1
=
43W/mK, k
2
=
0.04W/ mK
T
i
=
180
o
C, T
0
=
25
o
C
h
i
=
12kW /m
2
K, h
0
=
6W /m
2
K
.
k
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This note was uploaded on 05/22/2011 for the course ECH 142 taught by Professor Phillips during the Spring '10 term at UC Davis.
 Spring '10
 Phillips

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