INTRODUCTION TO HEAT TRANSFER

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INTRODUCTION TO HEAT TRANSFER (ME 411) Summer
2003 Lecture Number VII Ali R. Mazaheri Course
webpage www.clarkson.edu/mazahear/MAIN/ME411 De
partment of Mechanical and Aeronautical
Engineering Clarkson University
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Forced Convection Heat Transfer
Empirical Relations for Pipe Flow
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Empirical Relations for Pipe Flow
Dittus and Boelter (1930)
Fully developed turbulent in smooth pipe
Physical properties are evaluated at the Tb
Applicability Moderate temperature differences
between wall and the fluid
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Empirical Relations for Pipe Flow
When Wide temperature differences are present in
the flow
Sieder and Tate (1936)
Fully developed turbulent in smooth pipe
All physical properties are evaluated at the
Tb Except which is evaluated at the Tw.
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Empirical Relations for Pipe Flow
For the entrance region where the flow is not
fully developed
Nusselt (1931)
Entrance Regions
All physical properties are evaluated at the
Tb Except which is evaluated at the Tw.
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Empirical Relations for Pipe Flow
Petukhov (1970)
Fully developed turbulent in smooth pipe
Applicability
All properties are evaluated at the film
temperature Tf , Except
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Empirical Relations for Pipe Flow
Hausen (1943)
Fully developed Laminar flow in tubes _at_ constant
wall temperature
Sieder and Tate (1936)
Fully developed Laminar flow in tubes (simpler
formula)
Applicability
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Note Channel flow
If the channel is not of circular cross section,
it is recommended that the Hydraulic Diameter,
DH, be used.
A Cross sectional area of the flow P Wetted
perimeter
For example
Di
Do
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Empirical Relations for Flow Across Cylinders and
Spheres
Knudsen and Katz (1958)
(Liquids and gases)
All properties are evaluated at the film
temperature Tf.
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Empirical Relations for Flow Across Cylinders and
Spheres
(Liquids)
Fand (1965)
Applicability
(Liquids and Gases)
Eckert and Drake (1972)
For gases properties _at_ film temperature. For
liquids properties _at_ free-stream temperature.
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Empirical Relations for Flow Across Cylinders and
Spheres
Churchill and Bernstein (1977)
Applicability

Applicability
This formula is even accurate for liquid metals!
Properties _at_ the film temperature
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Empirical Relations for Flow Across Cylinders and
Spheres
Whitaker (1972)
Properties _at_ the free-stream temperature.
Applicability
Nakai and Okazaki (1975)
Applicability
Properties _at_ the film temperature
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Flow Across Tube Banks
In-line arrangement
Staggered arrangement
C and n are given in Table 6-4.