Principles of Heat Transfer -Kreith 7th

Principles of Heat Transfer -Kreith 7th

(Parte 1 de 6)

Conversion Factors for Commonly Used Quantities in Heat Transfer

QuantitySI :EnglishEnglish :SI*

Density1 kg/m3 0.06243 lbm/ft31 lbm/ft3 16.018 kg/m3 1 slug/ft3 515.38 kg/m3

Energy per unit mass1 J/kg 4.2995 10 4Btu/lbm1 Btu/lbm 2326 J/kg

Force1 N 0.22481 lbf1 lbf 4.448 N

Heat generation 1 W/m3 0.09665 Btu/(h ft3)1 Btu/(h ft3) 10.343 W/m3 per unit volume

Heat transfer rate1 W 3.412 Btu/h1 Btu/h 0.2931 W 1 ton 12,0 Btu/h 3517.2 W

Length1m 3.281 ft1 ft 0.3048 m 39.37 in1 in 0.0254 m

Mass1 kg 2.2046 lbm1 lbm 0.4536 kg 1 slug 14.594 kg

Mass flow rate1 kg/s 7936.6 lbm/h1 lbm/h 0.000126 kg/s 2.2046 lbm/s1 lbm/s 0.4536 kg/s

Power1 W 3.4123 Btu/h1 Btu/h 0.2931 W 1 Btu/s 1055.1 W

Pressure and stress 1 N/m2 0.02089 lbf/ft21 lbf/ft2 47.8 N/m2

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Conversion Factors for Commonly Used Quantities in Heat Transfer (Continued) QuantitySI :EnglishEnglish :SI*

Thermal diffusivity1 m2/s 10.7639 ft2/s1 ft2/s 0.0929 m2/s 1 ft2/h 2.581 10 5m2/s

Viscosity (kinematic)1 m2/s 10.7639 ft2/s1 ft2/s 0.0929 m2/s 1 ft2/h 2.581 10 5m2/s

*Some units in this column belong to the cgs and mks metric systems. †Definitions of the units of energy which are based on thermal phenomena:

1 Btu energy required to raise 1 lbmof water 1°F at 68°F 1 cal energy required to raise 1 g of water 1°C at 20°C

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Seventh Edition

Principles of HEAT TRANSFER

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Seventh Edition

Principles of HEAT TRANSFER

Frank Kreith Professor Emeritus, University of Colorado at Boulder, Boulder, Colorado

Raj M. Manglik Professor, University of Cincinnati, Cincinnati, Ohio

Mark S. Bohn Former Vice President, Engineering Rentech, Inc., Denver, Colorado

Australia • Brazil • Japan • Korea • Mexico • Singapore • Spain • United Kingdom • United States

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This ia an electronic version of the print textbook. Due to electronic rights restrictions, some third party may be suppressed. Edition review has deemed that any suppresed content does not materially affect the over all learning experience. The publisher reserves the right to remove the contents from this title at any time if subsequent rights restrictions require it. For valuable information on pricing, previous editions, changes to current editions, and alternate format, please visit w.cengage.com/highered to search by ISBN#, author, title, or keyword for materials in your areas of interest.

Copyright 2011 Cengage Learning, Inc. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part.

Principles of Heat Transfer, Seventh Edition

Authors Frank Kreith, Raj M. Manglik, Mark S. Bohn

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To our students all over the world

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When a textbook that has been used by more than a million students all over the world reaches its seventh edition, it is natural to ask, “What has prompted the authors to revise the book?” The basic outline of how to teach the subject of heat transfer, which was pioneered by the senior author in its first edition, published 60 years ago, has now been universally accepted by virtually all subsequent authors of heat transfer texts. Thus, the organization of this book has essentially remained the same over the years, but newer experimental data and, in particular the advent of computer technology, have necessitated reorganization, additions, and integration of numerical and computer methods of solution into the text.

The need for a new edition was prompted primarily by the following factors: 1)When a student begins to read a chapter in a textbook covering material that is new to him or her, it is useful to outline the kind of issues that will be important. We have, therefore, introduced at the beginning of each chapter a summary of the key issues to be covered so that the student can recognize those issues when they come up in the chapter. We hope that this pedagogic technique will help the students in their learning of an intricate topic such as heat transfer. 2) An important aspect of learning engineering science is to connect with practical applications, and the appropriate modeling of associated systems or devices. Newer applications, illustrative modeling examples, and more current state-of-the art predictive correlations have, therefore, been added in several chapters in this edition. 3) The sixth edition used MathCAD as the computer method for solving real engineering problems. During the ten years since the sixth edition was published, the teaching and utilization of MathCAD has been supplanted by the use of MATLAB. Therefore, the MathCAD approach has been replaced by MATLAB in the chapter on numerical analysis as well as for the illustrative problems in the real world applications of heat transfer in other chapters. 4) Again, from a pedagogic perspective of assessing student learning performance, it was deemed important to prepare general problems that test the students’ ability to absorb the main concepts in a chapter. We have, therefore, provided a set of Concept Review Questions that ask a student to demonstrate his or her ability to understand the new concepts related to a specific area of heat transfer. These review questions are available on the book website in the Student Companion Site at w.cengage.com/engineering. Solutions to the Concepts Review Questions are available for Instructors on the same website. 5) Furthermore, even though the sixth edition had many homework problems for the students, we have introduced some additional problems that deal directly with topics of current interest such as the space program and renewable energy.

The book is designed for a one-semester course in heat transfer at the junior or senior level. However, we have provided some flexibility. Sections marked with vii

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asterisks can be omitted without breaking the continuity of the presentation. If all the sections marked with an asterisk are omitted, the material in the book can be covered in a single quarter. For a full semester course, the instructor can select five or six of these sections and thus emphasize his or her own areas of interest and expertise.

The senior author would also like to express his appreciation to Professor Raj

M. Manglik, who assisted in the task of updating and refreshing the sixth edition to bring it up to speed for students in the twenty-first century. In turn, Raj Manglik is profoundly grateful for the opportunity to join in the authorship of this revised edition, which should continue to provide students worldwide an engaging learning experience in heat transfer. Although Dr. Mark Bohn decided not to participate in the seventh edition, we wish to express our appreciation for his previous contribution. In addition, the authors would like to acknowledge the contributions by the reviewers of the sixth edition who have provided input and suggestions for the update leading to the new edition of the book: B. Rabi Baliga, McGill University; F.C. Lai, University of Oklahoma; S. Mostafa Ghiaasiaan, Georgia Tech; Michael Pate, Iowa State University; and Forman A. Williams, University of California, San Diego. The authors would also like to thank Hilda Gowans, the Senior Developmental Editor for Engineering at Cengage Learning, who has provided support and encouragement throughout the preparation of the new edition. On a more personal level, Frank Kreith would like to express his appreciation to his assistant, Bev Weiler, who has supported his work in many tangible and intangible ways, and to his wife, Marion Kreith, whose forbearance with the time taken in writing books has been of invaluable help. Raj Manglik would like to thank his graduate students Prashant Patel, Rohit Gupta, and Deepak S. Kalaikadal for the computational solutions and algorithms in the book. Also, he would like to express his fond gratitude to his wife, Vandana Manglik, for her patient encouragement during the long hours needed in this endeavor, and to his children, Aditi and Animaesh, for their affection and willingness to forego some of our shared time.

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Chapter1Basic Modes of Heat Transfer2

1.1The Relation of Heat Transfer to Thermodynamics3 1.2Dimensions and Units7 1.3Heat Conduction9 1.4 Convection 17 1.5 Radiation 21 1.6Combined Heat Transfer Systems23 1.7 Thermal Insulation 45 1.8Heat Transfer and the Law of Energy Conservation51

References 58 Problems 58 Design Problems68

Chapter 2 Heat Conduction 70

2.1 Introduction 71 2.2The Conduction Equation71 2.3Steady Heat Conduction in Simple Geometries78 2.4 Extended Surfaces 95 2.5* Multidimensional Steady Conduction 105 2.6Unsteady or Transient Heat Conduction116 2.7*Charts for Transient Heat Conduction134 2.8 Closing Remarks 150

References 150 Problems 151 Design Problems163

Chapter3Numerical Analysis of Heat Conduction166

3.1 Introduction 167 3.2One-Dimensional Steady Conduction168 3.3 One-Dimensional Unsteady Conduction 180

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3.4*Two-Dimensional Steady and Unsteady Conduction195 3.5* Cylindrical Coordinates 215 3.6* Irregular Boundaries 217 3.7 Closing Remarks 221

References 221 Problems 2 Design Problems228

Chapter4Analysis of Convection Heat Transfer230

4.1 Introduction 231 4.2Convection Heat Transfer231 4.3Boundary Layer Fundamentals233 4.4Conservation Equations of Mass, Momentum, and Energy for Laminar Flow Over a Flat Plate235 4.5Dimensionless Boundary Layer Equations and Similarity

Parameters 239 4.6Evaluation of Convection Heat Transfer Coefficients243 4.7 Dimensional Analysis 245 4.8*Analytic Solution for Laminar Boundary Layer Flow Over a Flat Plate252 4.9*Approximate Integral Boundary Layer Analysis261 4.10*Analogy Between Momentum and Heat Transfer in Turbulent Flow Over a Flat Surface267 4.11Reynolds Analogy for Turbulent Flow Over Plane Surfaces273 4.12Mixed Boundary Layer274 4.13*Special Boundary Conditions and High-Speed Flow277 4.14 Closing Remarks 282

References 283 Problems 284 Design Problems294

Chapter 5 Natural Convection 296

5.1 Introduction 297 5.2Similarity Parameters for Natural Convection299 5.3Empirical Correlation for Various Shapes308 5.4*Rotating Cylinders, Disks, and Spheres322 5.5Combined Forced and Natural Convection325 5.6* Finned Surfaces 328 x Contents 67706_00_FM_pi-xi.qxd 5/14/10 9:32 AM Page x

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5.7 Closing Remarks 3

References 338 Problems 340 Design Problems348

Chapter6Forced Convection Inside Tubes and Ducts350

6.1 Introduction 351 6.2*Analysis of Laminar Forced Convection in a Long Tube360 6.3Correlations for Laminar Forced Convection370 6.4*Analogy Between Heat and Momentum Transfer in Turbulent Flow382 6.5Empirical Correlations for Turbulent Forced Convection386 6.6Heat Transfer Enhancement and Electronic-Device Cooling395 6.7 Closing Remarks 406

References 408 Problems 411 Design Problems418

Chapter7Forced Convection Over Exterior Surfaces420

7.1Flow Over Bluff Bodies421 7.2Cylinders, Spheres, and Other Bluff Shapes422 7.3*Packed Beds440 7.4Tube Bundles in Cross-Flow444 7.5*Finned Tube Bundles in Cross-Flow458 7.6*Free Jets461 7.7 Closing Remarks 471

References 473 Problems 475 Design Problems482

(Parte 1 de 6)

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