Introduction to Heat Transfer
6th Edition
ISBN: 9780470501962
Author: Frank P. Incropera, David P. DeWitt, Theodore L. Bergman, Adrienne S. Lavine
Publisher: Wiley, John & Sons, Incorporated
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Textbook Question
Chapter 3, Problem 3.68P
Referring to the semiconductor processing tool of Problem 5.13, it is desired at some point in the manufacturing cycle to cool the chuck, which is made of aluminum alloy 2024. The proposed cooling scheme passes air at 20°C between the air-supply head and the chuck surface.
(a) If the chuck is initially at a uniform temperature of l00°C, calculate the time required for its lower surface to reach 25°C, assuming a uniform convection coefficient of
(b) Generate a plot of the time-to-cool as a function of the convection coefficient for the range
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O H.W.:
The heat transfer coefficient for air flowing over a sphere is to be
determined by observing the temperature-time history of a sphere
fabricated from pure copper. The sphere, which is 12.7 mm in
diameter, is at 66°C before it is inserted into an airstream having a
temperature of 27°C. A thermocouple on the outer surface of the
sphere indicates 55°C 69 s after the sphere is inserted in the
airstream. Assume, and then justify, that the sphere behaves as a
spacewise isothermal object and calculate the heat transfer
coefficient.
p= 8933 kg/m", Cp
3
= 389 J/kg-K, k= 398
%3D
-T(0)= 66°C
T(69s) =55°C
Teo =27°C
-D=12.7mm
Worith Alenbiveo (Dr ALLMA
Hoot Tronofor
Task 3
Superheated steam at 575°C is routed from a boiler to the turbine of an electric power plant through
steel tubes (k = 35 W/m K) of 300 mm inner diameter and 30 mm wall thickness. To reduce heat loss
to the surroundings and to maintain a safe-to-touch outer surface temperature, a layer of calcium
silicate insulation (k = 0.10 W/m K) is applied to the tubes, while degradation of the insulation is
reduced by degradation of the insulation is reduced by wrapping it in a thin sheet of aluminium having
an emissivity of = 0.20. The air and wall temperatures of the power plant are 27°C. Assume that the
inner surface temperature of a steel tube corresponds to that of the steam and the convection coefficient
outside the aluminium sheet is 6 W/m²K,
(a) What is the minimum insulation thickness needed to ensure that the temperature of the
aluminium does not exceed 50°C?
(b) What is the corresponding heat loss per unit meter?
(c) What is the difference between lagged and unlagged pipes in…
FE
O H.W.:
The heat transfer coefficient for air flowing over a sphere is to be
determined by observing the temperature-time history of a sphere
fabricated from pure copper. The sphere, which is 12.7 mm in
diameter, is at 66°C before it is inserted into an airstream having a
temperature of 27°C. A thermocouple on the outer surface of the
sphere indicates 55°C 69 s after the sphere is inserted in the
airstream. Assume, and then justify, that the sphere behaves as a
spacewise isothermal object and calculate the heat transfer
coefficient.
3.
p= 8933 kg/m", Cp = 389 J/kg-K, k = 398
T(0) = 66°C
T(69s) = 55°C
Teo =27°C
-D=12.7mm
Warith Alanbiyaa (Dr. ALI M)
Heat Transfer
21
Chapter 3 Solutions
Introduction to Heat Transfer
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