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MindTap Engineering for Dunlap's Sustainable Energy, SI Edition, 2nd Edition [Instant Access], 1 term (6 months)
2nd Edition
ISBN: 9781337551755
Author: DUNLAP
Publisher: Cengage Learning US
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Chapter 8, Problem 17P
To determine
Calculate the outside temperature for which the heat loss through the wall is
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Help your customer to calculate the heat losses through a composite wall that includes
an 8-mm-thick hardwood siding, 40-mm by 130-mm hardwood studs with glass fiber
insulation (paper faced, 28 kg/m3 ), and a 12-mm layer of gypsum (vermiculite) wall
board as shown. The wall is 2.5 m high by 6.5 m wide.
- 20 °C
Wood siding
Stud
130 mm
Insulation
Wall board
21 °C
40 mm
Figure 1: The top view of thecomposite wall.
A 1,065 ft², 7 in. thick concrete wall has inside and outside surface temperatures of 25°C and 9°C. A 2 in. insulation batt with a thermal conductivity of k = 0.03 Btu/(h· ft· °F) is added
to the wall. Determine the reduction in heat transfer rate.
What is the thickness of the insulation in meters?
m
What is the thermal conductivity value of the insulation batt in W/(m .K)?
W/(mK)
What is the R-value of the concrete wall (in m². K/W)?
m². K/W
What is the R-value of the insulation batt (in m². K/W)?
m². K/W
What is the heat transfer rate (in W) when the insulation is added?
W
What is the percent reduction in the heat transfer rate?
%
3.
6.0" wide wooden fence posts are embedded in a concrete driveway a distance 12.125" apart. There is
a 1/16" gap between the post and the concrete (see diagram). The posts are installed when the temperature is
12°C. Determine if the gap will close when the temperature increases to 32°C and if not how big the gap will
be at that temperature. The thermal expansion coefficients of wood and concrete are awood =32 x 105 °C and
aconcrete =13 x 106 °C. 1 inch3D2.54 cm.
6.0"
12.0"
0.0625"
Chapter 8 Solutions
MindTap Engineering for Dunlap's Sustainable Energy, SI Edition, 2nd Edition [Instant Access], 1 term (6 months)
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