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Chapter 4
Transient Heat Conduction
4106
A curing kiln is heated by injecting steam into it and raising its inner surface temperature to a
specified value. It is to be determined whether the temperature at the outer surfaces of the kiln changes
during the curing period.
Assumptions
1
The temperature in the wall is affected by the thermal conditions at inner surfaces only and
the convection heat transfer coefficient inside is very large. Therefore, the wall can be considered to be a
semiinfinite medium with a specified surface temperature of 45
°
C.
2
The thermal properties of the
concrete wall are constant.
Properties
The thermal properties of the concrete wall are given to be
k
= 0.9 W/m.
°
C and
α
= 0.23
×
10
5
m
2
/s.
Analysis
We determine the temperature at a depth of
x
= 0.3 m in 3 h using the analytical solution,
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
=
−
−
t
x
erfc
T
T
T
t
x
T
i
s
i
α
2
)
,
(
2
°
C
42
°
C
30 cm
Kiln wall
x
0
Substituting,
C
9.1
°
=
=
=
⎟
⎟
⎟
⎠
⎞
⎜
⎜
⎜
⎝
⎛
×
×
=
−
−
−
)
,
(
1782
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 Fall '10
 Dr.DanielArenas
 Thermodynamics, Mass, Heat

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