An experimental procedure for validating results of Problem 6.14 involves preheating a copper disk to an initial elevated temperature T i and recording its temperature history T ( t ) as it is subsequently cooled by the impinging flow to a final temperature T f . The measured temperature decay may then be compared with predictions based on the correlation for N u ¯ D . Assume that values of a = 0.30 and n = 2 are associated with the correlation. Consider experimental conditions for which a disk of diameter D = 50 mm and length L = 25 mm is preheated to T i = 1000 K and cooled to T f = 400 K by an impinging airflow at T ∞ = 300 K . The cooled surface of the disk has an emissivity of ε = 0.8 and is exposed to large, isothermal surroundings for which T s u r = T ∞ . The remaining surfaces of the disk are well insulated, and heat transfer through the supporting rod may be neglected. Using results from Problem 6.14, compute and plot temperature histories corresponding to air velocities of V = 4 , 20 , and 50 m/s . Constant properties may be assumed for the copper ( ρ = 8933 kg/m 3 , c p = 425 J/kg ⋅ K, k = 386 W/m ⋅ K ) and air ( v = 38.8 × 10 − 6 m 2 /s, k = 0.0407 W/m ⋅ k, Pr = 0.684 ) .
An experimental procedure for validating results of Problem 6.14 involves preheating a copper disk to an initial elevated temperature T i and recording its temperature history T ( t ) as it is subsequently cooled by the impinging flow to a final temperature T f . The measured temperature decay may then be compared with predictions based on the correlation for N u ¯ D . Assume that values of a = 0.30 and n = 2 are associated with the correlation. Consider experimental conditions for which a disk of diameter D = 50 mm and length L = 25 mm is preheated to T i = 1000 K and cooled to T f = 400 K by an impinging airflow at T ∞ = 300 K . The cooled surface of the disk has an emissivity of ε = 0.8 and is exposed to large, isothermal surroundings for which T s u r = T ∞ . The remaining surfaces of the disk are well insulated, and heat transfer through the supporting rod may be neglected. Using results from Problem 6.14, compute and plot temperature histories corresponding to air velocities of V = 4 , 20 , and 50 m/s . Constant properties may be assumed for the copper ( ρ = 8933 kg/m 3 , c p = 425 J/kg ⋅ K, k = 386 W/m ⋅ K ) and air ( v = 38.8 × 10 − 6 m 2 /s, k = 0.0407 W/m ⋅ k, Pr = 0.684 ) .
Solution Summary: The author explains how to calculate and plot the effect of jet velocity on temperature.
An experimental procedure for validating results of Problem 6.14 involves preheating a copper disk to an initial elevated temperature
T
i
and recording its temperature history
T
(
t
)
as it is subsequently cooled by the impinging flow to a final temperature
T
f
.
The measured temperature decay may then be compared with predictions based on the correlation for
N
u
¯
D
.
Assume that values of
a
=
0.30
and
n
=
2
are associated with the correlation. Consider experimental conditions for which a disk of diameter
D
=
50
mm
and length
L
=
25
mm
is preheated to
T
i
=
1000
K
and cooled to
T
f
=
400
K
by an impinging airflow at
T
∞
=
300
K
.
The cooled surface of the disk has an emissivity of
ε
=
0.8
and is exposed to large, isothermal surroundings for which
T
s
u
r
=
T
∞
.
The remaining surfaces of the disk are well insulated, and heat transfer through the supporting rod may be neglected. Using results from Problem 6.14, compute and plot temperature histories corresponding to air velocities of
V
=
4
,
20
,
and
50
m/s
.
Constant properties may be assumed for the copper
(
ρ
=
8933
kg/m
3
,
c
p
=
425
J/kg
⋅
K,
k
=
386
W/m
⋅
K
)
and air
(
v
=
38.8
×
10
−
6
m
2
/s,
k
=
0.0407
W/m
⋅
k,
Pr
=
0.684
)
.
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flux is maintained along the tube and the tube wall is at a temperature 20◦C higher than the bismuth
bulk temperature, calculate the length of tube required to effect the heat transfe
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a) Find the temperature (°C) and power rating (kW) of the heater coil.
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c) Find the proportion of water…
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