INTRODUCTION TO HEAT TRANSFER

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INTRODUCTION TO HEAT TRANSFER (ME 411) Summer
2003 Lecture Number V Ali R. Mazaheri Course
webpage www.clarkson.edu/mazahear/MAIN/ME411 De
partment of Mechanical and Aeronautical
Engineering Clarkson University
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Unsteady State Conduction(Transient Heat
Transfer)
Initial Condition(I.C.)
Boundary Conditions (B.Cs.)
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Changing variable
New Initial and Boundary Conditions
Solution Method Separation of Variable
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Lumped Heat Capacity System
Quenching with uniform temperature.
Condition It is realistic for small physical
size bodies.
Heat transferred to the environmentchange of
internal energy
I.C.
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Validity of the Lumped Capacity Method
The lumped capacity method is only valid when
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Example1
A steel ball (5Cm in diameter) with uniform
temperature of 450 oC is suddenly placed in a
100 oC environment. How much time needed for
the ball to attain a temperature of 150 oC? (

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Solution
Lumped-Capacity Method

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Example2(Quenching of a steel plate)
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Transient Heat Flow in Semi-Infinite Solid
Initial Condition(I.C.)
Boundary Conditions (B.Cs.)
Using Laplace-Transform
Solution is shown in Figure 4-4, Page 137 of the
book!
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Constant Heat Flux on Semi-Infinite Solid
(Transient Heat Flow)
Initial Condition(I.C.)
Boundary Conditions (B.Cs.)
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Convection Boundary Condition on Semi-Infinite
Solid (Transient Heat Flow)
Initial Condition(I.C.)
Boundary Conditions (B.Cs.)

Solution is shown in Figure 4-5, Page 140 of the
book!
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Infinite surfaces
(suddenly subjected to convection environment)
Definition Surface whose thickness is smaller
than the other two dimensions.
The solution is plotted in Figures 4-7 through
4-12
Biot Number

Fourier Number
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Note
If the centerline temperature is desired only one
chart/graph is required. (Charts/graphs 4-7
through 4-9) To determine an off-center
temperature two charts/graphs are required.
(Charts/graphs 4-7 through 4-9 and
Charts/graphs 4-10 through 4-12) If
Bilt0.01 and Fogt0.2 then Chart/graph 4-13 should
be used for Small value of h, convection heat
coefficient. To evaluate the HEAT LOSS
charts/graphs 4-14 through 4-16 should be used.
In these graphs .
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Multi-Dimensional Systems
Semi-Infinite rectangular bar
Semi-infinite Plate
Infinite rectangular bar
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Short Cylinder
Rectangular parallelepiped
Semi-Infinite Cylinder
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Heat Transfer In Multi-Dimensional Systems
Intersection of Two bodies
Intersection of Three bodies (Semi-infinite
rectangular bar rectangular parallelepiped)