Welty Ingles 5 Ed Libro

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  • Fundamentals of Momentum,Heat, and Mass Transfer5th Edition

  • Fundamentals of Momentum,Heat, and Mass Transfer5th Edition

    James R. Welty

    Department of Mechanical Engineering

    Charles E. Wicks

    Department of Chemical Engineering

    Robert E. Wilson

    Department of Mechanical Engineering

    Gregory L. Rorrer

    Department of Chemical Engineering

    Oregon State University

    John Wiley & Sons, Inc.



    MARKETING MANAGER Christopher Ruel


    DESIGNER Michael St. Martine




    This book was set in by Thomson Digital and printed and bound by Hamilton Printing. The cover was

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    This book is printed on acid free paper.1

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    ISBN-13 978-0470128688

    Printed in the United States of America

    10 9 8 7 6 5 4 3 2 1

  • Preface to the 5th Edition

    The rst edition of Fundamentals of Momentum, Heat, and Mass Transfer, published in1969, was written to become a part of what was then known as the engineering science

    core of most engineering curricula. Indeed, requirements for ABET accreditation have

    stipulated that a signicant part of all curricula must be devoted to fundamental subjects.

    The emphasis on engineering science has continued over the intervening years, but the

    degree of emphasis has diminished as new subjects and technologies have entered the

    world of engineering education. Nonetheless, the subjects of momentum transfer (uid

    mechanics), heat transfer, and mass transfer remain, at least in part, important components

    of all engineering curricula. It is in this context that we now present the fth edition.

    Advances in computing capability have been astonishing since 1969. At that time, the

    pocket calculator was quite new and not generally in the hands of engineering students.

    Subsequent editions of this book included increasingly sophisticated solution techniques as

    technology advanced. Now,more than 30 years since the rst edition, computer competency

    among students is a fait accompli and many homework assignments are completed using

    computer software that takes care of most mathematical complexity, and a good deal of

    physical insight. We do not judge the appropriateness of such approaches, but they surely

    occur and will do so more frequently as software becomes more readily available, more

    sophisticated, and easier to use.

    In this edition, we still include some examples and problems that are posed in English

    units, but a large portion of the quantitative work presented is now in SI units. This is

    consistent withmost of the current generation of engineering textbooks. There are still some

    subdisciplines in the thermal/uid sciences that use English units conventionally, so it

    remains necessary for students to have some familiarity with pounds, mass, slugs, feet, psi,

    and so forth. Perhaps a fth edition, if it materializes, will nally be entirely SI.

    We, the original three authors (W3), welcome Dr. Greg Rorrer to our team. Greg is a

    member of the faculty of the Chemical Engineering Department at Oregon State University

    with expertise in biochemical engineering. He has had a signicant inuence on this

    editions sections on mass transfer, both in the text and in the problem sets at the end of

    Chapters 24 through 31. This edition is unquestionably strengthened by his contributions,

    and we anticipate his continued presence on our writing team.

    We are gratied that the use of this book has continued at a signicant level since the

    rst edition appeared some 30 years ago. It is our continuing belief that the transport

    phenomena remain essential parts of the foundation of engineering education and practice.

    With the modications and modernization of this fourth edition, it is our hope that

    Fundamentals of Momentum, Heat, and Mass Transfer will continue to be an essential

    part of students educational experiences.

    Corvallis, Oregon J.R. Welty

    March 2000 C.E. Wicks

    R.E. Wilson

    G.L. Rorrer


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  • Contents

    1. Introduction to Momentum Transfer 1

    1.1 Fluids and the Continuum 1

    1.2 Properties at a Point 2

    1.3 Point-to-Point Variation of Properties in a Fluid 5

    1.4 Units 8

    1.5 Compressibility 9

    1.6 Surface Tension 11

    2. Fluid Statics 16

    2.1 Pressure Variation in a Static Fluid 16

    2.2 Uniform Rectilinear Acceleration 19

    2.3 Forces on Submerged Surfaces 20

    2.4 Buoyancy 23

    2.5 Closure 25

    3. Description of a Fluid in Motion 29

    3.1 Fundamental Physical Laws 29

    3.2 Fluid-Flow Fields: Lagrangian and Eulerian Representations 29

    3.3 Steady and Unsteady Flows 30

    3.4 Streamlines 31

    3.5 Systems and Control Volumes 32

    4. Conservation of Mass: Control-Volume Approach 34

    4.1 Integral Relation 34

    4.2 Specic Forms of the Integral Expression 35

    4.3 Closure 39

    5. Newtons Second Law of Motion: Control-Volume Approach 43

    5.1 Integral Relation for Linear Momentum 43

    5.2 Applications of the Integral Expression for Linear Momentum 46

    5.3 Integral Relation for Moment of Momentum 52

    5.4 Applications to Pumps and Turbines 53

    5.5 Closure 57

    6. Conservation of Energy: Control-Volume Approach 63

    6.1 Integral Relation for the Conservation of Energy 63

    6.2 Applications of the Integral Expression 69


  • 6.3 The Bernoulli Equation 72

    6.4 Closure 76

    7. Shear Stress in Laminar Flow 81

    7.1 Newtons Viscosity Relation 81

    7.2 Non-Newtonian Fluids 82

    7.3 Viscosity 83

    7.4 Shear Stress in Multidimensional Laminar Flows of a Newtonian Fluid 88

    7.5 Closure 90

    8. Analysis of a Differential Fluid Element in Laminar Flow 92

    8.1 Fully Developed Laminar Flow in a Circular Conduit of Constant

    Cross Section 92

    8.2 Laminar Flow of a Newtonian Fluid Down an Inclined-Plane Surface 95

    8.3 Closure 97

    9. Differential Equations of Fluid Flow 99

    9.1 The Differential Continuity Equation 99

    9.2 Navier-Stokes Equations 101

    9.3 Bernoullis Equation 110

    9.4 Closure 111

    10. Inviscid Fluid Flow 113

    10.1 Fluid Rotation at a Point 113

    10.2 The Stream Function 114

    10.3 Inviscid, Irrotational Flow about an Innite Cylinder 116

    10.4 Irrotational Flow, the Velocity Potential 117

    10.5 Total Head in Irrotational Flow 119

    10.6 Utilization of Potential Flow 119

    10.7 Potential Flow AnalysisSimple Plane Flow Cases 120

    10.8 Potential Flow AnalysisSuperposition 121

    10.9 Closure 123

    11. Dimensional Analysis and Similitude 125

    11.1 Dimensions 125

    11.2 Dimensional Analysis of Governing Differential Equations 126

    11.3 The Buckingham Method 128

    11.4 Geometric, Kinematic, and Dynamic Similarity 131

    11.5 Model Theory 132

    11.6 Closure 134

    12. Viscous Flow 137

    12.1 Reynoldss Experiment 137

    12.2 Drag 138

    viii Contents

  • 12.3 The Boundary-Layer Concept 144

    12.4 The Boundary-Layer Equations 145

    12.5 Blasiuss Solution for the Laminar Boundary Layer on a Flat Plate 146

    12.6 Flow with a Pressure Gradient 150

    12.7 von Karman Momentum Integral Analysis 152

    12.8 Description of Turbulence 155

    12.9 Turbulent Shearing Stresses 157

    12.10 The Mixing-Length Hypothesis 158

    12.11 Velocity Distribution from the Mixing-Length Theory 160

    12.12 The Universal Velocity Distribution 161

    12.13 Further Empirical Relations for Turbulent Flow 162

    12.14 The Turbulent Boundary Layer on a Flat Plate 163

    12.15 Factors Affecting the Transition From Laminar to Turbulent Flow 165

    12.16 Closure 165

    13. Flow in Closed Conduits 168

    13.1 Dimensional Analysis of Conduit Flow 168

    13.2 Friction Factors for Fully Developed Laminar, Turbulent,

    and Transition Flow in Circular Conduits 170

    13.3 Friction Factor and Head-Loss Determination for Pipe Flow 173

    13.4 Pipe-Flow Analysis 176

    13.5 Friction Factors for Flow in the Entrance to a Circular Conduit 179

    13.6 Closure 182

    14. Fluid Machinery 185

    14.1 Centrifugal Pumps 186

    14.2 Scaling Laws for Pumps and Fans 194

    14.3 Axial and Mixed Flow Pump Congurations 197

    14.4 Turbines 197

    14.5 Closure 197

    15. Fundamentals of Heat Transfer 201

    15.1 Conduction 201

    15.2 Thermal Conductivity 202