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06_Properties_GB_2007
1
Thermal Properties of Materials
Arch 140, Lecture #7  Tuesday, Feb 12, 2008
CONDUCTION
•
T
hot
T
cold
Δ
T
d
A
Q
•
Q
= heat flow (Btu/hr)
d
= thickness (in)
Δ
T = temperature (ºF)
A
= area (ft
2
)
k
= conductivity
Btuin
hr ft
2
ºF
•
k
CONDUCTION
•
T
hot
T
cold
Δ
T
d
A
Q
•
Q =
x A x
Δ
T
k
d
Q
= heat flow (Btu/hr)
d
= thickness (in)
Δ
T = temperature (ºF)
A
= area (ft
2
)
k
= conductivity
Btuin
hr ft
2
ºF
•
•
k
Q =
x A x
Δ
T
k
d
•
CONDUCTION
Btu
1
*
Btuin
*
ft
2
*
°F
hr
in
hrft
2
°F
=
d
= thickness (in)
Δ
T = temperature (ºF)
A
= area (ft
2
)
k
= conductivity
(Btuin/hr ft
2
ºF)
Q =
x A x
Δ
T
k
d
•
CONDUCTION
Btu
1
*
Btuin
*
ft
2
*
°F
hr
in
hrft
2
°F
=
d
= thickness (in)
Δ
T = temperature (ºF)
A
= area (ft
2
)
k
= conductivity
(Btuin/hr ft
2
ºF)
A * 1/rd *
Δ
T
hrft
2
ºF/Btuin
r
resistivity
A * 1/R *
Δ
T
hrft
2
ºF/Btu
R
resistance
A * C *
Δ
T
Btu/hrft
2
ºF
C
conductance
A * k/d *
Δ
T
Btuin/hrft
2
ºF
k
conductivity
Heat flow,Q=
Units
Symbol
Property
•
“___ivity” = property of a material
(independent of amount)
“___ance” = property of an object
(depends on amount)
C = 1/R = k/d = 1/dr
or
R = d/k
Alternative Measures of
Conductive Properties
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2
Conductive Properties of
Typical Building Materials
4.26
Water (still)
0.17
Air (still)
1500.
Aluminum
310.
Steel
1.72
8” concrete block
12.
Stone
0.6
3” common brick
5.0
Brick
0.05
¼” glass
5.4
Glass
4.3
2x4 wood stud
0.8
Wood (soft)
19.0
51/2” insulation
0.3
Insulation
(hrft2°F/Btu)
Resistance, R
Component
(Btuin/hrft2°F)
Conductivity, k
Material
See Reader, Appendix 5
for property values
NOTE:
R = d/k
Example
• 4" thick wall of concrete, k = 12 (Btuin / hrft
2
ºF)
• Find R
= d/k
= 4 (in) / 12 (Btuin / hrft
2
ºF)
= 0.33 hrft
2
ºF/Btu
Example
• 4" thick wall of concrete, k = 12 (Btuin / hrft
2
ºF)
• Find R
= d/k
= 4 (in) / 12 (Btuin / hrft
2
ºF)
= 0.33 hrft
2
ºF/Btu
• If the wall was 10 ft
2
and had a 5ºF temperature
difference across it, how much heat would flow?
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This note was uploaded on 01/13/2010 for the course ARCH 140 taught by Professor Benton during the Spring '08 term at University of California, Berkeley.
 Spring '08
 Benton

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