design and optimization of thermal systems A Series of Textbooks and Reference Books Founding ppt

Plastics Products Design Handbook, Part A: Materials and Components; Part B: Processes and Design for Processes, edited by Edward Miller 9.. Practical Stress Analysis in Engineering Des

6HFRQG(GLWLRQ

Founding Editor

L L Faulkner

Columbus Division, Battelle Memorial Institute

and Department of Mechanical Engineering

The Ohio State University Columbus, Ohio

1 Spring Designer’s Handbook, Harold Carlson

2 Computer-Aided Graphics and Design, Daniel L Ryan

3 Lubrication Fundamentals, J George Wills

4 Solar Engineering for Domestic Buildings, William A Himmelman

5 Applied Engineering Mechanics: Statics and Dynamics, G Boothroyd

and C Poli

6 Centrifugal Pump Clinic, Igor J Karassik

7 Computer-Aided Kinetics for Machine Design, Daniel L Ryan

8 Plastics Products Design Handbook, Part A: Materials

and Components; Part B: Processes and Design for Processes,

edited by Edward Miller

9 Turbomachinery: Basic Theory and Applications, Earl Logan, Jr.

10 Vibrations of Shells and Plates, Werner Soedel

11 Flat and Corrugated Diaphragm Design Handbook, Mario Di Giovanni

12 Practical Stress Analysis in Engineering Design, Alexander Blake

13 An Introduction to the Design and Behavior of Bolted Joints,

John H Bickford

14 Optimal Engineering Design: Principles and Applications,

James N Siddall

15 Spring Manufacturing Handbook, Harold Carlson

16 Industrial Noise Control: Fundamentals and Applications, edited by

20 Gear Drive Systems: Design and Application, Peter Lynwander

21 Controlling In-Plant Airborne Contaminants: Systems Design

and Calculations, John D Constance

22 CAD/CAM Systems Planning and Implementation, Charles S Knox

23 Probabilistic Engineering Design: Principles and Applications,

James N Siddall

25 Finite Element Methods: An Introduction, Ronald L Huston

and Chris E Passerello

26 Mechanical Fastening of Plastics: An Engineering Handbook,

Brayton Lincoln, Kenneth J Gomes, and James F Braden

27 Lubrication in Practice: Second Edition, edited by W S Robertson

28 Principles of Automated Drafting, Daniel L Ryan

29 Practical Seal Design, edited by Leonard J Martini

30 Engineering Documentation for CAD/CAM Applications,

and Mark E Coticchia

34 Steam Plant Calculations Manual, V Ganapathy

35 Design Assurance for Engineers and Managers, John A Burgess

36 Heat Transfer Fluids and Systems for Process and Energy

Applications, Jasbir Singh

37 Potential Flows: Computer Graphic Solutions, Robert H Kirchhoff

38 Computer-Aided Graphics and Design: Second Edition,

Daniel L Ryan

39 Electronically Controlled Proportional Valves: Selection

and Application, Michael J Tonyan, edited by Tobi Goldoftas

40 Pressure Gauge Handbook, AMETEK, U.S Gauge Division, edited by

Philip W Harland

41 Fabric Filtration for Combustion Sources: Fundamentals and Basic Technology, R P Donovan

42 Design of Mechanical Joints, Alexander Blake

43 CAD/CAM Dictionary, Edward J Preston, George W Crawford,

and Mark E Coticchia

44 Machinery Adhesives for Locking, Retaining, and Sealing,

Girard S Haviland

45 Couplings and Joints: Design, Selection, and Application,

Jon R Mancuso

46 Shaft Alignment Handbook, John Piotrowski

47 BASIC Programs for Steam Plant Engineers: Boilers, Combustion, Fluid Flow, and Heat Transfer, V Ganapathy

48 Solving Mechanical Design Problems with Computer Graphics,

Jerome C Lange

49 Plastics Gearing: Selection and Application, Clifford E Adams

50 Clutches and Brakes: Design and Selection, William C Orthwein

51 Transducers in Mechanical and Electronic Design, Harry L Trietley

52 Metallurgical Applications of Shock-Wave and High-Strain-Rate Phenomena, edited by Lawrence E Murr, Karl P Staudhammer,

and Marc A Meyers

53 Magnesium Products Design, Robert S Busk

55 Cam Design and Manufacture: Second Edition; with cam design software for the IBM PC and compatibles, disk included,

Preben W Jensen

56 Solid-State AC Motor Controls: Selection and Application,

Sylvester Campbell

57 Fundamentals of Robotics, David D Ardayfio

58 Belt Selection and Application for Engineers, edited by

Wallace D Erickson

59 Developing Three-Dimensional CAD Software with the IBM PC,

C Stan Wei

60 Organizing Data for CIM Applications, Charles S Knox, with

contributions by Thomas C Boos, Ross S Culverhouse,

and Paul F Muchnicki

61 Computer-Aided Simulation in Railway Dynamics, by Rao V Dukkipati

and Joseph R Amyot

62 Fiber-Reinforced Composites: Materials, Manufacturing, and Design,

P K Mallick

63 Photoelectric Sensors and Controls: Selection and Application,

Scott M Juds

64 Finite Element Analysis with Personal Computers,

Edward R Champion, Jr and J Michael Ensminger

65 Ultrasonics: Fundamentals, Technology, Applications: Second Edition, Revised and Expanded, Dale Ensminger

66 Applied Finite Element Modeling: Practical Problem Solving

for Engineers, Jeffrey M Steele

67 Measurement and Instrumentation in Engineering: Principles

and Basic Laboratory Experiments, Francis S Tse and Ivan E Morse

68 Centrifugal Pump Clinic: Second Edition, Revised and Expanded,

Igor J Karassik

69 Practical Stress Analysis in Engineering Design: Second Edition, Revised and Expanded, Alexander Blake

70 An Introduction to the Design and Behavior of Bolted Joints:

Second Edition, Revised and Expanded, John H Bickford

71 High Vacuum Technology: A Practical Guide, Marsbed H Hablanian

72 Pressure Sensors: Selection and Application, Duane Tandeske

73 Zinc Handbook: Properties, Processing, and Use in Design,

Frank Porter

74 Thermal Fatigue of Metals, Andrzej Weronski and Tadeusz Hejwowski

75 Classical and Modern Mechanisms for Engineers and Inventors,

Preben W Jensen

76 Handbook of Electronic Package Design, edited by Michael Pecht

77 Shock-Wave and High-Strain-Rate Phenomena in Materials, edited by

Marc A Meyers, Lawrence E Murr, and Karl P Staudhammer

78 Industrial Refrigeration: Principles, Design and Applications,

P C Koelet

79 Applied Combustion, Eugene L Keating

80 Engine Oils and Automotive Lubrication, edited by Wilfried J Bartz

82 Fundamental Fluid Mechanics for the Practicing Engineer,

86 Vibrations of Shells and Plates: Second Edition, Revised

and Expanded, Werner Soedel

87 Steam Plant Calculations Manual: Second Edition, Revised

and Expanded, V Ganapathy

88 Industrial Noise Control: Fundamentals and Applications, Second Edition, Revised and Expanded, Lewis H Bell and Douglas H Bell

89 Finite Elements: Their Design and Performance, Richard H MacNeal

90 Mechanical Properties of Polymers and Composites: Second Edition, Revised and Expanded, Lawrence E Nielsen and Robert F Landel

91 Mechanical Wear Prediction and Prevention, Raymond G Bayer

92 Mechanical Power Transmission Components, edited by

David W South and Jon R Mancuso

93 Handbook of Turbomachinery, edited by Earl Logan, Jr.

94 Engineering Documentation Control Practices and Procedures,

Ray E Monahan

95 Refractory Linings Thermomechanical Design and Applications,

Charles A Schacht

96 Geometric Dimensioning and Tolerancing: Applications

and Techniques for Use in Design, Manufacturing, and Inspection,

James D Meadows

97 An Introduction to the Design and Behavior of Bolted Joints:

Third Edition, Revised and Expanded, John H Bickford

98 Shaft Alignment Handbook: Second Edition, Revised and Expanded,

John Piotrowski

99 Computer-Aided Design of Polymer-Matrix Composite Structures,

edited by Suong Van Hoa

100 Friction Science and Technology, Peter J Blau

101 Introduction to Plastics and Composites: Mechanical Properties and Engineering Applications, Edward Miller

102 Practical Fracture Mechanics in Design, Alexander Blake

103 Pump Characteristics and Applications, Michael W Volk

104 Optical Principles and Technology for Engineers, James E Stewart

105 Optimizing the Shape of Mechanical Elements and Structures,

A A Seireg and Jorge Rodriguez

106 Kinematics and Dynamics of Machinery, Vladimír Stejskal

and Michael Valásek

107 Shaft Seals for Dynamic Applications, Les Horve

108 Reliability-Based Mechanical Design, edited by Thomas A Cruse

109 Mechanical Fastening, Joining, and Assembly, James A Speck

111 High-Vacuum Technology: A Practical Guide, Second Edition,

Revised and Expanded, Marsbed H Hablanian

112 Geometric Dimensioning and Tolerancing: Workbook

and Answerbook, James D Meadows

113 Handbook of Materials Selection for Engineering Applications,

edited by G T Murray

114 Handbook of Thermoplastic Piping System Design, Thomas Sixsmith

and Reinhard Hanselka

115 Practical Guide to Finite Elements: A Solid Mechanics Approach,

Steven M Lepi

116 Applied Computational Fluid Dynamics, edited by Vijay K Garg

117 Fluid Sealing Technology, Heinz K Muller and Bernard S Nau

118 Friction and Lubrication in Mechanical Design, A A Seireg

119 Influence Functions and Matrices, Yuri A Melnikov

120 Mechanical Analysis of Electronic Packaging Systems,

Stephen A McKeown

121 Couplings and Joints: Design, Selection, and Application, Second Edition, Revised and Expanded, Jon R Mancuso

122 Thermodynamics: Processes and Applications, Earl Logan, Jr.

123 Gear Noise and Vibration, J Derek Smith

124 Practical Fluid Mechanics for Engineering Applications,

John J Bloomer

125 Handbook of Hydraulic Fluid Technology, edited by George E Totten

126 Heat Exchanger Design Handbook, T Kuppan

127 Designing for Product Sound Quality, Richard H Lyon

128 Probability Applications in Mechanical Design, Franklin E Fisher

and Joy R Fisher

129 Nickel Alloys, edited by Ulrich Heubner

130 Rotating Machinery Vibration: Problem Analysis and Troubleshooting,

Maurice L Adams, Jr

131 Formulas for Dynamic Analysis, Ronald L Huston and C Q Liu

132 Handbook of Machinery Dynamics, Lynn L Faulkner

and Earl Logan, Jr

133 Rapid Prototyping Technology: Selection and Application,

Kenneth G Cooper

134 Reciprocating Machinery Dynamics: Design and Analysis,

Abdulla S Rangwala

135 Maintenance Excellence: Optimizing Equipment Life-Cycle Decisions,

edited by John D Campbell and Andrew K S Jardine

136 Practical Guide to Industrial Boiler Systems, Ralph L Vandagriff

137 Lubrication Fundamentals: Second Edition, Revised and Expanded,

D M Pirro and A A Wessol

138 Mechanical Life Cycle Handbook: Good Environmental Design and Manufacturing, edited by Mahendra S Hundal

139 Micromachining of Engineering Materials, edited by

Joseph McGeough

140 Control Strategies for Dynamic Systems: Design and Implementation,

John H Lumkes, Jr

edited by Peter J Shull

143 Diesel Engine Engineering: Thermodynamics, Dynamics, Design, and Control, Andrei Makartchouk

144 Handbook of Machine Tool Analysis, Ioan D Marinescu,

Constantin Ispas, and Dan Boboc

145 Implementing Concurrent Engineering in Small Companies,

Susan Carlson Skalak

146 Practical Guide to the Packaging of Electronics: Thermal

and Mechanical Design and Analysis, Ali Jamnia

147 Bearing Design in Machinery: Engineering Tribology and Lubrication,

150 The CAD Guidebook: A Basic Manual for Understanding

and Improving Computer-Aided Design, Stephen J Schoonmaker

151 Industrial Noise Control and Acoustics, Randall F Barron

152 Mechanical Properties of Engineered Materials, Wolé Soboyejo

153 Reliability Verification, Testing, and Analysis in Engineering Design,

Gary S Wasserman

154 Fundamental Mechanics of Fluids: Third Edition, I G Currie

155 Intermediate Heat Transfer, Kau-Fui Vincent Wong

156 HVAC Water Chillers and Cooling Towers: Fundamentals, Application, and Operation, Herbert W Stanford III

157 Gear Noise and Vibration: Second Edition, Revised and Expanded,

J Derek Smith

158 Handbook of Turbomachinery: Second Edition, Revised

and Expanded, edited by Earl Logan, Jr and Ramendra Roy

159 Piping and Pipeline Engineering: Design, Construction, Maintenance, Integrity, and Repair, George A Antaki

160 Turbomachinery: Design and Theory, Rama S R Gorla

and Aijaz Ahmed Khan

161 Target Costing: Market-Driven Product Design, M Bradford Clifton,

Henry M B Bird, Robert E Albano, and Wesley P Townsend

162 Fluidized Bed Combustion, Simeon N Oka

163 Theory of Dimensioning: An Introduction to Parameterizing Geometric Models, Vijay Srinivasan

164 Handbook of Mechanical Alloy Design, edited by George E Totten,

Lin Xie, and Kiyoshi Funatani

165 Structural Analysis of Polymeric Composite Materials, Mark E Tuttle

166 Modeling and Simulation for Material Selection and Mechanical Design, edited by George E Totten, Lin Xie, and Kiyoshi Funatani

167 Handbook of Pneumatic Conveying Engineering, David Mills,

Mark G Jones, and Vijay K Agarwal

168 Clutches and Brakes: Design and Selection, Second Edition,

William C Orthwein

170 Handbook of Lead-Free Solder Technology for Microelectronic Assemblies, edited by Karl J Puttlitz and Kathleen A Stalter

171 Vehicle Stability, Dean Karnopp

172 Mechanical Wear Fundamentals and Testing: Second Edition,

Revised and Expanded, Raymond G Bayer

173 Liquid Pipeline Hydraulics, E Shashi Menon

174 Solid Fuels Combustion and Gasification, Marcio L de Souza-Santos

175 Mechanical Tolerance Stackup and Analysis, Bryan R Fischer

176 Engineering Design for Wear, Raymond G Bayer

177 Vibrations of Shells and Plates: Third Edition, Revised and Expanded,

Werner Soedel

178 Refractories Handbook, edited by Charles A Schacht

179 Practical Engineering Failure Analysis, Hani M Tawancy,

Anwar Ul-Hamid, and Nureddin M Abbas

180 Mechanical Alloying and Milling, C Suryanarayana

181 Mechanical Vibration: Analysis, Uncertainties, and Control, Second Edition, Revised and Expanded, Haym Benaroya

182 Design of Automatic Machinery, Stephen J Derby

183 Practical Fracture Mechanics in Design: Second Edition, Revised and Expanded, Arun Shukla

184 Practical Guide to Designed Experiments, Paul D Funkenbusch

185 Gigacycle Fatigue in Mechanical Practive, Claude Bathias

and Paul C Paris

186 Selection of Engineering Materials and Adhesives,

Lawrence W Fisher

187 Boundary Methods: Elements, Contours, and Nodes,

Subrata Mukherjee and Yu Xie Mukherjee

188 Rotordynamics, Agnieszka (Agnes) Muszn´yska

189 Pump Characteristics and Applications: Second Edition,

192 Micro Electro Mechanical System Design, James J Allen

193 Probability Models in Engineering and Science, Haym Benaroya

and Seon Han

194 Damage Mechanics, George Z Voyiadjis and Peter I Kattan

195 Standard Handbook of Chains: Chains for Power Transmission and Material Handling, Second Edition, American Chain Association

and John L Wright, Technical Consultant

196 Standards for Engineering Design and Manufacturing,

Wasim Ahmed Khan and Abdul Raouf S.I

197 Maintenance, Replacement, and Reliability: Theory and Applications,

Andrew K S Jardine and Albert H C Tsang

198 Finite Element Method: Applications in Solids, Structures, and Heat Transfer, Michael R Gosz

200 Fundamentals of Natural Gas Processing, Arthur J Kidnay

and William Parrish

201 Optimal Control of Induction Heating Processes, Edgar Rapoport

and Yulia Pleshivtseva

202 Practical Plant Failure Analysis: A Guide to Understanding Machinery Deterioration and Improving Equipment Reliability,

Neville W Sachs, P.E

203 Shaft Alignment Handbook, Third Edition, John Piotrowski

204 Advanced Vibration Analysis , S Graham Kelly

205 Principles of Composite Materials Mechanics, Second Edition,

Ronald F Gibson

206 Applied Combustion, Second Edition, Eugene L Keating

207 Introduction to the Design and Behavior of Bolted Joints,

Fourth Edition: Non-Gasketed Joints, John H Bickford

208 Analytical and Approximate Methods in Transport Phenomena,

Marcio L de Souza-Santos

209 Design and Optimization of Thermal Systems, Second Edition,

Yogesh Jaluria

CRC Press is an imprint of the

Taylor & Francis Group, an informa business

Boca Raton London New York

'HVLJQDQG2SWLPL]DWLRQ RI7KHUPDO6\VWHPV

6HFRQG(GLWLRQ

<RJHVK-DOXULD

CRC Press

Taylor & Francis Group

6000 Broken Sound Parkway NW, Suite 300

Boca Raton, FL 33487-2742

© 2008 by Taylor & Francis Group, LLC

CRC Press is an imprint of Taylor & Francis Group, an Informa business

No claim to original U.S Government works

Printed in the United States of America on acid-free paper

10 9 8 7 6 5 4 3 2 1

International Standard Book Number-13: 978-0-8493-3753-6 (Hardcover)

This book contains information obtained from authentic and highly regarded sources Reprinted material

is quoted with permission, and sources are indicated A wide variety of references are listed Reasonable efforts have been made to publish reliable data and information, but the author and the publisher cannot assume responsibility for the validity of all materials or for the consequences of their use

Except as permitted under U.S Copyright Law, no part of this book may be reprinted, reproduced, mitted, or utilized in any form by any electronic, mechanical, or other means, now known or hereafter invented, including photocopying, microfilming, and recording, or in any information storage or retrieval system, without written permission from the publishers.

trans-For permission to photocopy or use material electronically from this work, please access www.copyright com (http://www.copyright.com/) or contact the Copyright Clearance Center, Inc (CCC) 222 Rosewood Drive, Danvers, MA 01923, 978-750-8400 CCC is a not-for-profit organization that provides licenses and registration for a variety of users For organizations that have been granted a photocopy license by the CCC, a separate system of payment has been arranged.

Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are

used only for identification and explanation without intent to infringe.

Library of Congress Cataloging-in-Publication Data

Jaluria, Yogesh.

Design and optimization of thermal systems / Yogesh Jaluria 2nd ed.

p cm (Mechanical engineering)

Includes bibliographical references and index.

ISBN 978-0-8493-3753-6 (alk paper)

1 Heat engineering 2 Engineering design I Title II Series.

Chapter 1 Introduction 1

1.1 Engineering Design 2

1.1.1 Design Versus Analysis 2

1.1.2 Synthesis for Design 6

1.1.3 Selection Versus Design 7

1.2 Design as Part of Engineering Enterprise 9

1.2.1 Need or Opportunity 9

1.2.2 Evaluation and Market Analysis 10

1.2.3 Feasibility and Chances of Success 12

1.2.4 Engineering Design 14

1.2.5 Research and Development 15

1.2.6 Need for Optimization 16

1.2.7 Fabrication, Testing, and Production 18

1.3 Thermal Systems 19

1.3.1 Basic Characteristics 19

1.3.2 Analysis 22

1.3.3 Types and Examples 25

1.4 Outline and Scope of the Book 40

1.5 Summary 43

References 44

Chapter 2 Basic Considerations in Design 47

2.1 Formulation of the Design Problem 47

2.1.1 Requirements and Specifications 47

2.1.2 Given Quantities 50

2.1.3 Design Variables 51

2.1.4 Constraints or Limitations 53

2.1.5 Additional Considerations 55

2.2 Conceptual Design 58

2.2.1 Innovative Conceptual Design 58

2.2.2 Selection from Available Concepts 62

2.2.3 Modifications in the Design of Existing Systems 64

2.3 Steps in the Design Process 70

2.3.1 Physical System 72

2.3.2 Modeling 75

2.3.5 Optimal Design 83

2.3.6 Safety Features, Automation, and Control 86

2.3.7 Communicating the Design 90

2.3.8 Patents and Copyrights 92

2.4 Computer-Aided Design 97

2.4.1 Main Features 97

2.4.2 Computer-Aided Design of Thermal Systems 98

2.5 Material Selection 104

2.5.1 Different Materials 104

2.5.2 Material Properties and Characteristics for Thermal Systems 108

2.5.3 Selection and Substitution of Materials 110

2.6 Summary 113

References 115

Problems 116

Chapter 3 Modeling of Thermal Systems 125

3.1 Introduction 125

3.1.1 Importance of Modeling in Design 125

3.1.2 Basic Features of Modeling 125

3.2 Types of Models 128

3.2.1 Analog Models 129

3.2.2 Mathematical Models 130

3.2.3 Physical Models 130

3.2.4 Numerical Models 131

3.2.5 Interaction Between Models 133

3.2.6 Other Classifications 133

3.3 Mathematical Modeling 134

3.3.1 General Procedure 134

3.3.2 Final Model and Validation 160

3.4 Physical Modeling and Dimensional Analysis 165

3.4.1 Dimensional Analysis 166

3.4.2 Modeling and Similitude 176

3.4.3 Overall Physical Model 180

3.5 Curve Fitting 180

3.5.1 Exact Fit 181

3.5.2 Best Fit 183

3.6 Summary 194

References 196

Problems 197

4.1 Numerical Modeling 208

4.1.1 General Features 208

4.1.2 Development of a Numerical Model 210

4.1.3 Available Software 211

4.2 Solution Procedures 212

4.2.1 Linear Algebraic Systems 213

4.2.2 Nonlinear Algebraic Systems 220

4.2.3 Ordinary Differential Equations 227

4.2.4 Partial Differential Equations 238

4.3 Numerical Model for a System 247

4.3.1 Modeling of Individual Components 248

4.3.2 Merging of Different Models 251

4.3.3 Accuracy and Validation 252

4.4 System Simulation 253

4.4.1 Importance of Simulation 254

4.4.2 Different Classes 256

4.4.3 Flow of Information 259

4.5 Methods for Numerical Simulation 264

4.5.1 Steady Lumped Systems 264

4.5.2 Dynamic Simulation of Lumped Systems 272

4.5.3 Distributed Systems 278

4.5.4 Simulation of Large Systems 282

4.5.5 Numerical Simulation Versus Real System 283

4.6 Summary 284

References 285

Problems 286

Chapter 5 Acceptable Design of a Thermal System: A Synthesis of Different Design Steps 299

5.1 Introduction 299

5.2 Initial Design 300

5.3 Design Strategies 309

5.3.1 Commonly Used Design Approach 309

5.3.2 Other Strategies 309

5.3.3 Iterative Redesign Procedure 317

5.4 Design of Systems from Different Application Areas 322

5.4.1 Manufacturing Processes 323

5.4.2 Cooling of Electronic Equipment 329

5.4.3 Environmental Systems 336

5.4.4 Heat Transfer Equipment 342

5.4.5 Fluid Flow Systems 350

5.5 Additional Considerations for Large Practical Systems 362

5.6 Summary 373

References 374

Problems 375

Chapter 6 Economic Considerations 383

6.1 Introduction 383

6.2 Calculation of Interest 385

6.2.1 Simple Interest 385

6.2.2 Compound Interest 385

6.2.3 Continuous Compounding 387

6.2.4 Effective Interest Rate 388

6.3 Worth of Money as a Function of Time 390

6.3.1 Present Worth 390

6.3.2 Future Worth 391

6.3.3 Inflation 393

6.4 Series of Payments 396

6.4.1 Future Worth of Uniform Series of Amounts 396

6.4.2 Present Worth of Uniform Series of Amounts 397

6.4.3 Continuous Compounding in a Series of Amounts 399

6.4.4 Changing Amount in Series of Payments 400

6.4.5 Shift in Time 402

6.4.6 Different Frequencies 403

6.4.7 Changes in Schedule 403

6.5 Raising Capital 405

6.5.1 Bonds 406

6.5.2 Stocks 408

6.6 Taxes 408

6.6.1 Inclusion of Taxes 409

6.6.2 Depreciation 410

6.7 Economic Factor in Design 413

6.7.1 Cost Comparison 413

6.7.2 Rate of Return 417

6.8 Application to Thermal Systems 419

6.9 Summary 421

References 421

Problems 422

Chapter 7 Problem Formulation for Optimization 429

7.1 Introduction 429

7.1.1 Optimization in Design 429

7.1.2 Final Optimized Design 431

7.2.2 Constraints 434

7.2.3 Operating Conditions Versus Hardware 437

7.2.4 Mathematical Formulation 438

7.3 Optimization Methods 440

7.3.1 Calculus Methods 440

7.3.2 Search Methods 441

7.3.3 Linear and Dynamic Programming 442

7.3.4 Geometric Programming 444

7.3.5 Other Methods 444

7.4 Optimization of Thermal Systems 447

7.4.1 Important Considerations 447

7.4.2 Different Approaches 448

7.4.3 Different Types of Thermal Systems 449

7.4.4 Examples 451

7.4.5 Consideration of the Second Law of Thermodynamics 455

7.5 Practical Aspects in Optimal Design 457

7.5.1 Choice of Variables for Optimization 457

7.5.2 Sensitivity Analysis 459

7.5.3 Dependence on Objective Function: Trade-Offs 461

7.5.4 Multi-Objective Optimization 462

7.5.5 Part of Overall Design Strategy 464

7.5.6 Change of Concept or Model 465

7.6 Summary 466

References 467

Problems 468

Chapter 8 Lagrange Multipliers 473

8.1 Introduction to Calculus Methods 473

8.2 The Lagrange Multiplier Method 475

8.2.1 Basic Approach 475

8.2.2 Physical Interpretation 477

8.2.3 Significance of the Multipliers 485

8.3 Optimization of Unconstrained Problems 486

8.3.1 Use of Gradients for Optimization 487

8.3.2 Determination of Minimum or Maximum 487

8.3.3 Conversion of Constrained to Unconstrained Problem 489

8.4 Optimization of Constrained Problems 491

8.5 Applicability to Thermal Systems 494

8.5.1 Use of Curve Fitting 494

8.5.2 Examples 495

8.5.3 Inequality Constraints 499

8.6 Summary 503

References 504

Problems 505

Chapter 9 Search Methods 511

9.1 Basic Considerations 511

9.1.1 Importance of Search Methods 512

9.1.2 Types of Approaches 513

9.1.3 Application to Thermal Systems 514

9.2 Single-Variable Problem 515

9.2.1 Uniform Exhaustive Search 517

9.2.2 Dichotomous Search 519

9.2.3 Fibonacci Search 521

9.2.4 Golden Section and Other Search Methods 523

9.2.5 Comparison of Different Elimination Methods 524

9.3 Unconstrained Search with Multiple Variables 527

9.3.1 Lattice Search 529

9.3.2 Univariate Search 530

9.3.3 Steepest Ascent/Descent Method 532

9.4 Multivariable Constrained Optimization 537

9.4.1 Penalty Function Method 537

9.4.2 Search Along a Constraint 542

9.5 Examples of Thermal Systems 547

9.6 Summary 551

References 553

Problems 554

Chapter 10 Geometric, Linear, and Dynamic Programming and Other Methods for Optimization 559

10.1 Geometric Programming 559

10.1.1 Applicability 560

10.1.2 Unconstrained Optimization 561

10.1.3 Mathematical Proof 570

10.1.4 Constrained Optimization 573

10.1.5 Nonzero Degree of Difficulty 578

10.2 Linear Programming 579

10.3 Dynamic Programming 588

10.4 Other Methods 590

10.5 Summary 591

References 592

Problems 593

11.1 Knowledge-Based Systems 599

11.1.1 Introduction 600

11.1.2 Basic Components 602

11.1.3 Expert Knowledge 607

11.1.4 Design Methodology 609

11.1.5 Application to Thermal Systems 610

11.2 Additional Constraints 621

11.3 Professional Ethics 623

11.4 Sources of Information 625

11.5 An Overview of Design of Thermal Systems 628

11.6 Summary 631

References 632

Problems 633

Design Projects 635

Appendix A Computer Programs 639

Appendix B Material Properties 659

Appendix C Interest Tables 679

Appendix D Heat Transfer Correlations 687

Index 697

Design is an essential element in engineering education and practice In recentyears, there has been a growing emphasis on the design and optimization of sys-tems because of growing worldwide competition and the development of newprocesses and techniques Design has long been very important in undergraduatemechanical engineering curricula around the country However, the effort hadbeen largely directed at mechanical systems, dealing with areas such as transmis-sion, vibrations, robotics, and controls, and at components such as gears, cams,springs, and linkages

With the growth of thermal systems, such as those related to materials cessing, energy conversion, pollution, aerospace, and automobiles, the need todesign and optimize thermal systems has also grown In mechanical engineer-ing programs around the country, courses have been developed on the design

pro-of thermal systems These are pro-often elective courses, or, in many schools, suchcourses form the final capstone design course, often alternated with a designcourse on mechanical systems Invariably, optimization is an important element

in such courses because of the crucial need to optimize systems in practicalapplications

This book is written as a textbook at the senior undergraduate or the first-yeargraduate level It can also be used as a reference book for other thermal sciencescourses, such as those on heat transfer, fluid mechanics, and thermodynamics,and for courses in applied areas, such as power plants, environmental control ofbuildings, and solar energy systems It can be used for reference by practicingengineers as well Although the book is written for engineering education curri-cula in the United States, the material and treatment can easily be used in variouscountries around the world The book is largely written for mechanical engineers.However, the material is suitable for courses in other engineering disciplines,such as chemical, aerospace, industrial, and materials engineering

The book is directed at the design of thermal systems, employing examplesfrom diverse areas such as manufacturing, energy systems, cooling of electronicequipment, refrigeration, environmental problems, engines, and heat transfer equip-ment Many such examples and an introduction to design are given in Chapter 1.Then the conceptual design and formulation of the design problem are presented

in Chapter 2, along with the main constituents of design, including material tion The design process, as predominantly based on the mathematical modeling

selec-of the system and on the results obtained from numerical simulation, is presented

in the next three chapters Analytical results, if available, are valuable for ing the numerical model as well as for providing a fundamental basis for design

validat-The basic approach to the development of a suitable model is discussed inChapter 3 in detail since this forms the most crucial step in the design of a sys-tem Various approximations and idealizations that can be used for modeling arepresented, along with examples of mathematical modeling of practical systems.This is followed in Chapter 4 by detailed discussions of numerical modeling andsimulation, again linking these to the mathematical model and experimental data.These results then form the basis for creative design of thermal systems and forthe evaluation of the designs obtained.

The development of a workable, or acceptable, design, one which satisfiesthe requirements and constraints of the problem, is discussed as a synthesis of thedifferent design steps Several examples are given in Chapter 5 to illustrate theoverall procedure This is followed in Chapter 6 by a discussion of economicfactors in design since these often guide system design and optimization The for-mulation of the optimization problem is explained in Chapter 7 The presentation

on optimization includes several applicable methods such as calculus methods,search methods, and linear, dynamic, and geometric programming These topicsare covered in Chapter 8 through Chapter 10 Again, thermal systems found inseveral important and relevant areas are used as examples to illustrate the ideaspresented Solved examples and problems strengthen the presentation and allowthe important concepts to be assimilated by the readers Recent trends, such asknowledge-based design methodology, are included in Chapter 11 Additionalpractical considerations, such as economic, safety, and materials, are also dis-cussed at various stages of the presentation

Therefore, the book starts with the basic design concept and develops thematerial through modeling and simulation stages of the thermal process and sys-tem on to the creation of a workable design The iterative process that is often used

to obtain an acceptable design is presented This logically leads to optimizationprocedures and the improvement of the design to obtain the best possible solu-tion under the given constraints The book offers a systematic approach, explor-ing the various considerations that lead to a workable and, finally, to an optimaldesign; uses up-to-date examples and problems, and presents the most currentinformation and design tools available in this important field Examples rangefrom simple systems to large, complex practical systems Synthesis of the variousaspects that constitute design is discussed in detail A few relevant computer pro-grams are included to help with the numerical modeling and simulation Theseinclude programs on curve fitting, solution of algebraic systems, and solution ofsimple differential equations Quantitative information on materials, economics,and heat transfer correlations is also included The mathematical modeling ofsystems is a particularly important aspect of design, though it is often neglected.Modeling is presented with a wide range of physical examples and a discussion ofthe types of approximations that can be used to simplify the problem The inputsobtained from the model for an innovative and optimal design are outlined

appropriate methodology Readers are encouraged to use their own backgrounds,imaginations, and available literature for designing different types of systems.Since simple closed-form, analytical, solutions are rarely obtained in practicalthermal systems, clear and concise answers are not readily available in manycases A consideration of several practical systems makes this aspect of thermalsystem design clear.

The material included in this book has been used in courses for undergraduateseniors at Rutgers University and at the Indian Institute of Technology, Kanpur,India The topics, examples, and problems have, therefore, been largely tested in

a classroom environment Various design projects and examples emerged fromthese courses, and some of them are included in the text In keeping with thebasic design process, many of the problems are open-ended and a unique solution

is not obtained

SUPPLEMENT

A solutions manual, prepared by me in order to ensure the problem-solving odology is the same as that in the book, is available to text adopters This manualcontains possible solutions to most of the problems in this book (since many prob-lems are open-ended and thus do not have a unique solution)

meth-ACKNOWLEDGMENTS

Many colleagues, friends, and students have contributed in significant ways tothe development of this material and to my understanding of the design process

Of particular help have been the many discussions I have had with Professors

V Sernas and N.A Langrana of Rutgers University on the design of systems

My interactions with students over many years on design projects and on cal design problems have also provided important insights into the design pro-cess The comments of the manuscript reviewers and of Professor J R Lloyd

practi-of Michigan State University, the editor practi-of this series, have been very valuableand helpful in organizing and presenting the material I would like to take theopportunity to thank each of the manuscript reviewers personally The review-ers are Jamal Seyed-Yagoobi, Texas A&M University; Andrew V Tangborn,Northeastern University; Edwin Griggs, Tennessee Technological University;Bakhtier Farouk, Drexel University; Donald Fenton, Kansas State University;John R Lloyd, Consulting Editor, Michigan State University; Donald C Raney,The University of Alabama; Jeffrey Hodgson, The University of Tennessee,Knoxville; Louis C Burmeister, The University of Kansas; Edward Vendell,Utah State University; Edward Hensel, New Mexico State University; PrasannaKadaba, Georgia Institute of Technology The assistance provided by the staff ofMcGraw-Hill has also contributed very significantly to the book

to this work has been the unqualified support and encouragement of my wife,Anuradha, and the patience and understanding of our children, Pratik, Aseem,and Ankur Without their support, it would not have been possible for me tomeet the strong demands placed on my time by this book.

Yogesh Jaluria

The second edition of this book follows the basic principles, approaches, andtreatment presented in the first edition The focus is clearly on systems in whichthermodynamics, fluid flow, and thermal transport form the main considerations.However, the ideas, methodology, and pedagogy are applicable to a wide variety

of engineering systems The main thrust is to design and optimize systems based

on inputs from simulation and experimental data on materials and on componentsthat constitute the system A systematic approach is followed to finally obtain anoptimal design, starting with conceptual design and proceeding through mod-eling, simulation, and design evaluation to choose a feasible design Additionalaspects, such as system control, communicating the design, financial consider-ations, safety, and material selection, that arise in practical systems are also pre-sented A wide range of examples from many different applied areas, such asenergy, environment, heating, cooling, manufacturing, aerospace, and transpor-tation systems, are employed to explain the various elements involved in model-ing, simulation, and design Even though there are many significant differencesbetween such a diversity of systems, the basic approach is still very similar andcan be used for relatively simple systems with few components to large, com-plex systems with many components and subsystems A large number of solvedexamples and exercises are included to supplement the discussion and to illustratethe ideas presented in the text

The book is appropriate as a textbook for engineering senior undergraduate orfirst-year graduate level courses in design, as well as for capstone design coursestaught in most engineering curricula It is also appropriate as a reference book incourses at this level in heat transfer, fluid mechanics, thermodynamics, and otherrelated basic and applied areas in mechanical engineering and other engineeringdisciplines The book would also be useful as a reference for engineers working

on a wide range of problems in industry, national labs, and other organizations.Among the major differences from the first edition is a greater emphasis onthe use of MATLAB®instead of high-level programming languages like Fortran

or C, for numerical modeling and simulation of components and systems This is

in keeping with the current trend in engineering education where MATLAB hasemerged as the dominant environment for numerical solution of basic mathemati-cal equations Several Fortran programs in the first edition have been replaced bycorresponding MATLAB programs or commands The resulting simplification innumerical simulation is demonstrated through exercises and examples in MAT-LAB, which are included to strengthen the presentation Additional solved exam-ples and exercises on thermodynamic systems like heating, cooling, and powersystems have been included because of the relative ease of simulating the compo-nents as lumped and steady Other simple systems are included in the discussion,

examples are included in all the chapters, as well as additional projects at theend of the book Extra information is added at various places, as appropriate; forinstance, in materials and in optimization Much of the presentation has beenrevised and, in several cases, simplified and clarified to make it easier to follow.The presentation has also been updated to include recent advances in designand optimization Among the additional topics included are artificial-intelligence-based techniques like genetic algorithms, fuzzy logic, and artificial neural net-works Response surfaces and other optimization techniques are included in thediscussion, along with effective use of concurrent experimental and numericalinputs for design and optimization Multi-objective optimization is particularlyimportant for thermal systems, since more than one objective function is typicallyimportant in realistic systems, and a detailed treatment is included Other strate-gies to optimize the system are presented Additional references have been added

on these topics, as well as on the others that were covered in the first edition ous references have been updated The application of these ideas to the optimiza-tion of thermal systems is reiterated with examples of actual, practical systems.The material presented in this textbook is the outcome of many years ofteaching design of thermal systems, in elective courses and in capstone designcourses The inputs from many colleagues and former graduate and undergradu-ate students have been valuable in selecting the topics and the depth and breadth

Previ-of coverage Discussions with colleagues outside Rutgers University, particularly

at the conferences of the American Society of Mechanical Engineers, have beenimportant in understanding the instruction and concerns at other universities.Inputs from reviewers of the first edition were also useful in fine-tuning some

of the presentation The support and assistance provided by the editorial staff ofTaylor & Francis, particularly by Jessica Vakili, have been valuable in the devel-opment of the second edition Finally, I would like to acknowledge the encour-agement and support of my wife, Anuradha, and of our children, Ankur, Aseem,and Pratik, as well as Pratik’s wife, Leslie, and son, Vyan, for this effort It didtake me away from them for many hours and distracted me at other times Theirpatience and understanding is thus greatly appreciated

Yogesh Jaluria

Yogesh Jaluria, M.S., Ph.D., is currently Board of Governors Professor at

Rutgers, the State University of New Jersey, New Brunswick, and the chairman

of the Department of Mechanical and Aerospace Engineering He received hisB.S degree from the Indian Institute of Technology, Delhi, India, in 1970 Heobtained his M.S and Ph.D degrees in mechanical engineering from CornellUniversity

Jaluria has contributed more than 400 technical articles, including over 160 inarchival journals and 16 chapters in books He has two patents in materials pro-cessing and is the author/co-author of six books Jaluria received the 2003 RobertHenry Thurston Lecture Award from the American Society of MechanicalEngineers (ASME), and the 2002 Max Jakob Memorial Award for eminentachievement in the field of heat transfer from ASME and the American Institute

of Chemical Engineers (AIChE) In 2002, he was named Board of GovernorsProfessor of Mechanical and Aerospace Engineering at Rutgers University Hewas selected as the 2000 Freeman Scholar by the Fluids Engineering Division,ASME He received the 1999 Worcester Reed Warner Medal and the 1995 HeatTransfer Memorial Award for significant research contributions to the science ofheat transfer, both from ASME He also received the 1994 Distinguished AlumniAward from the Indian Institute of Technology, Delhi

Jaluria is a Fellow of ASME and a member of several other professionalsocieties He served as the chair of the Heat Transfer Division of ASME during

2002–2003 He is presently the editor of the ASME Journal of Heat Transfer.

Design is generally regarded as a creative process by which new methods, devices, and techniques are developed to solve new or existing problems Though many professions are concerned with creativity leading to new arrangements, struc-tures, or artifacts, design is an essential element in engineering education and practice Due to increasing worldwide competition and the need to develop new, improved, and more efficient processes and techniques, a growing emphasis is being placed on design Interest lies in producing new and higher quality products

at minimal cost, while satisfying increasing concerns regarding the tal impact and safety It is no longer adequate just to develop a system that per-forms the desired task to satisfy a recognized need of the society It is crucial to optimize the process so that a chosen quantity, known as the objective function,

environmen-is maximized or minimized Thus, for a given system, the output, profit, tivity, product quality, etc., may be maximized, or the cost per item, investment, energy input, etc., may be minimized

produc-The survival and growth of most industries today are strongly dependent on the design and optimization of the relevant systems With the advent of many new materials, such as composites and ceramics, and new manufacturing processes, several classical industries, such as the steel industry, have diminished in impor-tance in the recent years, while many new fields have emerged It is important

to keep abreast of changing trends in these areas and to use new techniques for product improvement and cost reduction Even in an expanding engineering area, such as consumer electronics, the prosperity of a given company is closely linked with the design and optimization of new processes and systems and optimiza-tion of existing ones Consequently, the subject of design, which had always been important, has become increasingly critical in today’s world and has also become closely coupled with optimization

In recent years, we have also seen a tremendous growth in the development and use of thermal systems in which fluid flow and transport of energy play a dominant role These systems arise in many diverse engineering fields such as those related to manufacturing, power generation, pollution, air conditioning, and aerospace and automobile engineering Therefore, it has become important to apply design and optimization methods that traditionally have been applied to mechanical systems, such as those involved with transmission, vibrations, con-trols, and robotics, to thermal systems and processes In this book, we shall focus

on thermal systems, considering examples from many important areas, ranging from classical and traditional fields like engines and heating/cooling to new and emerging fields like nanomaterials and fuel cells However, many of the basic concepts presented here are also applicable to other types of systems such as

those arising in different fields of engineering, for example, civil, chemical, trical, and industrial engineering.

elec-In this chapter, we shall first consider the main features of engineering design, its importance in the overall context of an engineering enterprise, and the need to optimize We will also examine design in relation to analysis, synthesis, selection

of equipment, and other important activities that support design This discussion will be followed by a consideration of systems, components, and subsystems The basic nature of thermal systems will be outlined, and examples of different types

of systems will be presented from many diverse and important areas

in terms of a new and different approach to the solution of an existing engineering problem that has been solved by other methods or a solution to a problem not solved before The process by which such new, different, or improved solutions are derived

and applied to engineering problems is termed design.

1.1.1 D ESIGN V ERSUS A NALYSIS

We are all quite familiar with the analysis of engineering problems using mation derived from basic areas such as statics, dynamics, thermodynamics, fluid mechanics, and heat transfer The problems considered are often relevant to these disciplines and little interaction between different disciplines is brought into play In addition, all the appropriate inputs needed for the problem are usually given and the results are generally unique and well defined, so that the solution to a given problem may be carried out to completion, yielding the final result that satisfies the various

infor-inputs and conditions provided Such problems may be termed as closed-ended.

The calculation of the velocity profile for developed, laminar fluid flow in a circular pipe to yield the well-known parabolic distribution shown in Figure 1.1(a)

is an example of analysis Similarly, the analysis of steady, one-dimensional heat conduction in a flat plate results in the linear temperature distribution shown in Figure 1.1(b) Textbooks on fluid mechanics and heat transfer, such as Fox and McDonald (2003) and Incropera and Dewitt (2001), respectively, present many

such analyses for a variety of physical circumstances Many courses are directed

at engineering analysis and students are taught various techniques to solve simple

as well as complicated problems in fundamental and applied areas Most students thus acquire the skills and expertise to analyze well-defined and well-posed prob-lems in different engineering disciplines

The design process, on the other hand, is open-ended, that is, the results are

not well known or well defined at the onset The inputs may also be vague or incomplete, making it necessary to seek additional information or to employ approximations and assumptions There is also usually considerable interaction between various disciplines, particularly between technical areas and those con-cerned with cost, safety, and the environment A unique solution is generally not obtained and one may have to choose from a range of acceptable solutions In addition, a solution that satisfies all the requirements may not be obtained and

it may be necessary to relax some of the requirements to obtain an acceptable

solution Therefore, trade-offs generally form a necessary part of design because

certain characteristics of the system may have to be given up in order to achieve some other goals such as greater cost effectiveness or smaller environmental

impact Individual or group judgment based on available information is needed to

decide on the final design

FIGURE 1.1 Analytical results for (a) developed fluid flow in a circular pipe and

(b) steady-state one-dimensional heat conduction in a flat plate.

Circular pipe

R

u o u

x

– )

A Few Examples

Consider the example of an electronic component located on a board and being cooled by the flow of air driven by a fan, as shown in Figure 1.2 The energy dissipated by the component is given If the temperature distributions in the com-ponent, the board, and other parts of the system are to be determined, analysis or numerical calculations may be used for the purpose Even though the numerical procedure for obtaining this information may be quite involved, the solution is unique for the given geometry, material properties, and dimensions Different methods of solution may be employed but the problem itself is well defined, with all the input quantities specified and with no variables left to be chosen arbitrarily There are no trade-offs or additional considerations to be included

Let us now consider the corresponding design problem of finding the

appro-priate materials, geometry, and dimensions so that the temperature T c in the

component remains below a certain value, Tmax, in order to ensure satisfactory performance of the electronic circuit This is clearly a much more involved problem There is no unique answer because many combinations of materials, dimensions, geometry, fan capacity, etc., may be chosen to satisfy the given

requirement T c < Tmax There is considerable freedom and flexibility in ing the different variables that characterize the system Such a problem is, thus, open-ended and many solutions may be obtained to satisfy the given need and constraints, if any, on cost, size, dimensions, etc It is also possible that a sat-isfactory solution cannot be found for the given conditions and an additional cooling method such as a heat pipe, which conveys the heat dissipated at a much higher rate by means of a phase change process, may have to be included, as shown by the dotted lines in Figure 1.2 Then the design process must consider the two cooling arrangements and determine the relevant characteristic param-eters for these cases Thus, different approaches, often known as conceptual designs, may be considered for satisfying the given requirements

choos-Fan

Forced air flow

Electronic component Circuit board

Heat pipe

FIGURE 1.2 An electronic component being cooled by forced convection and by a heat

pipe.

Another example that illustrates the difference between analysis and design

is that of a casting process, as sketched in Figure 1.3 Molten material is poured into a mold and allowed to solidify If the properties of the material undergoing solidification and of the various parts of the system, such as the mold wall and the insulation, are given along with the relevant dimensions, the initial temperature,

and the convective heat transfer coefficient h at the outer surface of the mold,

the problem may be solved by analysis or numerical computation to determine the temperature distributions in the solid material, liquid, and various parts

of the system, as well as the rate and total time of solidification for the casting (Flemings, 1974) The problem can often be simplified by using approximations such as constant material properties, negligible convective flow in the melt, uni-

form heat transfer coefficient h over the entire surface, etc But once the problem

is posed in terms of the governing equations and appropriate boundary tions, the results are generally well defined and unique

condi-We may now pose a corresponding design problem by allowing a choice of the materials and dimensions for the mold wall and insulation and of the cooling conditions at the outer surface, in order to reduce the solidification time below a desired value Tcast Then, many combinations of wall material and thickness, cool-ing parameters, insulation parameters, etc., are possible Again, there is no unique solution and, indeed, there is no guarantee that a solution will be found All that is given is the requirement regarding the solidification time and quantities that may

be varied to achieve a satisfactory design In other cases, the requirements may

be specified as limitations on the temperature gradients in the casting in order to improve the quality of the product Clearly, we are dealing with an open-ended problem without a unique solution

It is largely because of the open-ended nature of design problems that design

is often much more involved than analysis Consequently, while extensive mation is available in the literature on the analysis of various thermal processes and on the resulting effects of the governing variables, the corresponding design problems have received much less attention However, even though design and analysis are very different in their objectives and goals, analysis usually forms

infor-Insulation Mold Solid Melt Moving solid/melt interface

FIGURE 1.3 The casting process in an enclosed region.

the basis for the design process It is used to study the behavior of a given tem, choose the appropriate variables for the desired effects, and evaluate various designs, leading to satisfactory and optimized systems.

sys-1.1.2 S YNTHESIS FOR D ESIGN

Synthesis is another key element in the design process, since several components and their corresponding analyses are brought together to yield the characteristics

of the overall system Results from different areas have to be linked and sized in order to include all of the important concerns that arise in a practical system (Suh, 1990; Ertas and Jones, 1996; Dieter, 2000) We cannot consider only the heat transfer aspects in the casting problem while ignoring the strength of materials and manufacturing aspects Information from different types of mod-els, including experimental and numerical results, and from existing systems are incorporated into the design process The cost, properties, and characteristics of various materials that may be employed must also form part of the design effort, since material selection is a very important factor in obtaining an acceptable or optimal system Additional aspects, such as safety, legal, regulatory, and envi-ronmental considerations, are also synthesized in order to obtain a satisfactory design Figure 1.4 shows a sketch of a typical design process for a system, involv-ing both analysis and synthesis as part of the overall effort

synthe-Acceptable design obtained Yes

No Acceptable?

Analysis and evaluation Experimental

Inputs

FIGURE 1.4 Schematic of a typical design procedure.

1.1.3 S ELECTION V ERSUS D ESIGN

We are frequently faced with the task of selecting parts in order to assemble a system or a device that will perform a desired duty In several cases, the entire equipment may be selected from what is available on the market, for instance, a heat exchanger, a pump, or a compressor Even though selection is an important ingredient in engineering practice, it is quite different from designing a component

or device and it is important to distinguish between the two Selection largely involves determining the specifications of the item from the requirements for the given task Based on these specifications, a choice is made from the various types

of items available with different ratings or features Design, on the other hand, involves starting with a basic concept, modeling and evaluating different designs, and obtaining a final design that meets the given requirements and constraints The system may then be fabricated and tests carried out on a prototype before going into production Therefore, design is directed at creating a new process or system, whereas selection is concerned with choosing the right item for a given job.Selection and design are frequently employed together in the development of

a system, using selection for components that are easily available over the ranges

of interest Standard items such as valves, control sensors, heaters, flow meters, and storage tanks are usually selected from catalogs of available equipment Sim-ilarly, pumps, compressors, fans, and condensers may be selected, rather than designed, for a given application Obviously, design is involved in the develop-ment of these components as well; however, for a given system, the design of these individual components may be avoided in the interest of time, cost, and conve-nience For instance, a company that develops and manufactures heat exchangers would generally design different types of heat exchangers for different fluids and applications, achieving different ranges in heat transfer rate, area, effectiveness, flow rate, etc Different configurations such as counter-flow and parallel-flow heat exchangers, compact heat exchangers, shell-and-tube heat exchangers, etc., as shown in Figure 1.5, may be considered for a variety of applications These may then be designed to obtain desired parametric ranges of heat transfer rate, output temperature, size, etc (Kays and London, 1984) Design engineers working on another thermal system, such as air conditioning or indoor heating, may simply select the condenser, evaporator, or other types of heat exchangers needed, rather than design these

Selection is clearly a much less involved process, as compared to design The requirements and specifications of the desired component or equipment are matched with whatever is available If an item possessing the desired characteris-tics is not available, design is needed to obtain one that is acceptable for the given purpose Because selection is often used as part of the overall system design, the two terms are sometimes interchanged We are mainly concerned with the design

of thermal systems and, as such, selection of components needed for a system will be considered only as a step in the design process, particularly during the synthesis of the various parts

FIGURE 1.5 Common types of heat exchangers (a) Concentric pipe parallel-flow,

(b) concentric pipe counter-flow, (c) cross-flow with unmixed fluids, (d) fin-tube compact heat exchanger cores, (e) shell-and-tube (Adapted from Incropera, F.P and Dewitt, D.P., 1990.)

1.2 DESIGN AS PART OF ENGINEERING ENTERPRISE

Before proceeding to a discussion of the characteristics and types of thermal systems, it will be instructive to consider the position occupied by design and optimization in the overall scheme of an engineering undertaking The planning and execution of such an enterprise involve many aspects that are engineering based and several that are not, for example, economic and market considerations Engineering design is one of the key elements in the development of a product or

a system and is coupled with the other considerations to obtain a successful ture Let us follow a typical engineering undertaking from the initial recognition

ven-of a need for a particular item or process to its final implementation

1.2.1 N EED OR O PPORTUNITY

Defining a need or opportunity is always the first step in an engineering

undertak-ing because it provides the impetus to develop a product or system Need refers to

a specific requirement and implies that a suitable item is not available and must be developed for the desired purpose The need for a given item may be felt at vari-ous levels, ranging from the consumer and the retailer to the industry itself, and may involve developing a new system or modifying and improving existing ones

Opportunity is the recognition of a chance to develop a new product that may be

superior to existing ones or less expensive It may also be an item for which the market is expected to develop as it becomes available

Consumers’ need for a new or improved product is often discovered through surveys conducted by the sales division and through consumer interactions with salespersons In some cases, individual consumers and consumer groups may also provide information on their needs and requirements The problems or limitations

in existing products may become evident from such inputs, indicating the need for developing a new or improved item The development of the hard disk in personal computers arose mainly because of consumers’ need for larger data storage capac-ity Similarly, CD-ROM and memory sticks were introduced because of the need

to store and transfer data and information Anti-lock brakes, air bags, controlled fuel injection, and streamlining of the body have been introduced in automobiles in response to safety and efficiency needs The need for specific com-ponents or systems may also arise in auxiliary industrial units that are dependent on the main industry For instance, the development of larger and improved television systems, such as the high definition television, has generated demand for a range of electronic products and systems that will be met by other specialized industries.The opportunity to move into a new area, develop a new product or system, substantially increase the quality of an existing item, or significantly reduce the cost of an item can also form the starting point for an engineering undertaking This is particularly true of new materials because the substitution of materials in existing systems by new or improved materials could lead to substantial improve-ment in the system performance and/or reduction in cost The replacement of metal casings in electronic equipment by plastic or ceramic ones and of metal frames in sports equipment by composites represents such changes The personal

computer-computer is an interesting example of such an opportunity-based development

An opportunity was perceived by the industry, mainly by Apple Computers Inc., and adequate technical expertise was available to develop a personal computer This led to an expanding market and the use of the personal computer in a variety

of applications, ranging from word processing, information storage, and ing to instruction and data acquisition The video cassette recorder, fiber-optics cable, compact disc player, microwave oven, and the Apple iPod and iPhone represent new products that were developed in recent years with possible oppor-tunities and expanding markets in mind

account-The industry today is very dynamic and is always on the lookout for nities where the available technical know-how can be used effectively to develop new ideas, leading to new products and systems The research and development division of a given industrial concern is often the source of such opportunities because of its interest in new materials and techniques being developed in the academic, industrial, and research environments outside the firm However, a new idea may also arise from other divisions in the company based on their involve-ment with various processes and products

opportu-1.2.2 E VALUATION AND M ARKET A NALYSIS

An important consideration in the development of a new concept is its tion for economic viability, since profit is usually the main concern in engineer-ing undertakings Even if need and opportunity have indicated that a particular product or system will be useful and will have a secure market, it is necessary

evalua-to determine how big the market is, what price range it will bear, and what the possible expenses involved in taking the concept to completion are The sales and marketing division of the company could target typical consumers, who may

be individuals, organizations, or other industries The information regarding price, consumption level, desired characteristics of the product, and nature of the intended application could be gathered through surveys, mail, telephone or individual contact, interactions with product outlets and sales organizations, and inputs from consumer groups Earlier studies on similar products may also be used to provide the relevant information for evaluating the proposed venture For instance, many products have recently been reduced in size and weight because

of consumer demand These include camcorders, laptop computers, digital eras, and even cars In each case, a market analysis was carried out to ensure that the price and the demand were satisfactory to justify the time, money, and effort spent in developing these items Of course, in the case of cars, the need to reduce fuel consumption was one of the main motivations for size reduction

cam-Once information from various sources is obtained on the product being considered, the marketing division may carry out a detailed market analysis to determine the anticipated volume of sales and the effect of the price on the sales

As the price increases, the volume of sales is expected to decrease Consider the development of a new gas water heater for residential use The cost increases as the capacity of the tank is increased Similarly, a faster response to an increased

demand for hot water, though desirable, would require larger heaters, leading

to higher costs Better safety and durability features will also raise the price Clearly, additional features and higher quality make it attractive to various con-sumers and may open additional markets However, as the price continues to increase, the sales volume will generally decrease, partly because of less frequent replacement, resulting from improved quality, and partly due to loss in sales to less expensive versions Very selective models may have a small volume of sales but a large profit, or return, per unit Figure 1.6 shows typical sales volume versus price curves The curves are separated by differences in the expenditure involved

in marketing, advertising, and sales The profit per item is smaller at a given price

if the expense in advertising is increased However, it is expected that the total volume will increase due to better advertising, making the overall venture more profitable (Stoecker, 1989)

The evaluation of the enterprise must include all expenses that are expected

to be incurred Besides the cost of manufacture of the given item and the expense

of advertising and sales, the cost of designing and developing the system, from the initial concept to the prototype, must also be considered The cost must include both labor and the capital investment needed for equipment and supplies Considering all the relevant costs and the anticipated sales volume (employing economic concepts as outlined in Chapter 6), the given undertaking may be eval-uated to determine the profit or the percentage return on the investment If the return is too low, the process may be terminated at this stage Several new ideas and concepts are evaluated by typical industries, and many of these do not go much farther because of an expected small volume of sales or a large investment needed for development and manufacture In several cases, specialized compa-nies exist in order to fabricate custom-made or one-of-a-kind products at the spe-cific request of a client The price may be exorbitant in these cases, but only one

or two systems are made, providing a satisfactory return because of the high price rather than the large sales volume

Price

Sales, advertisement, and marketing costs

FIGURE 1.6 Typical variation of volume of sales with price.