Heat Transfer: A Practical Approach

HEAT TRANSFER A Practical Approach YUNUS A. CENGEL SECOND EDITION cen58933_fm.qxd 9/11/2002 10:56 AM Page vii CONTENTS Preface xviii Nomenclature xxvi CHAPTER TWO HEAT CONDUCTION EQUATION 61 2-1 CHAPTER ONE Steady versus Transient Heat Transfer 63 Multidimensional Heat Transfer 64 Heat Generation 66 BASICS OF HEAT TRANSFER 1 1-1 Thermodynamics and Heat Transfer 2 2-2 Application Areas of Heat Transfer 3 Historical Background 3 1-2 Engineering Heat Transfer 4 Heat and Other Forms of Energy 6 2-3 The First Law of Thermodynamics 11 Energy Balance for Closed Systems (Fixed Mass) 12 Energy Balance for Steady-Flow Systems 12 Surface Energy Balance 13 1-5 Heat Transfer Mechanisms 17 1-6 Conduction 17 2-4 Boundary and Initial Conditions 77 1 2 3 4 5 6 Thermal Conductivity 19 Thermal Diffusivity 23 2-5 1-7 Convection 25 1-8 Radiation 27 2-6 2-7 1-9 Simultaneous Heat Transfer Mechanisms 30 Specified Temperature Boundary Condition 78 Specified Heat Flux Boundary Condition 79 Convection Boundary Condition 81 Radiation Boundary Condition 82 Interface Boundary Conditions 83 Generalized Boundary Conditions 84 Solution of Steady One-Dimensional Heat Conduction Problems 86 Heat Generation in a Solid 97 Variable Thermal Conductivity, k(T) 104 Topic of Special Interest: A Brief Review of Differential Equations 107 Summary 111 References and Suggested Reading 112 Problems 113 1-10 Problem-Solving Technique 35 A Remark on Significant Digits 37 Engineering Software Packages 38 Engineering Equation Solver (EES) 39 Heat Transfer Tools (HTT) 39 Topic of Special Interest: Thermal Comfort 40 Summary 46 References and Suggested Reading 47 Problems 47 General Heat Conduction Equation 74 Rectangular Coordinates 74 Cylindrical Coordinates 75 Spherical Coordinates 76 Specific Heats of Gases, Liquids, and Solids 7 Energy Transfer 9 1-4 One-Dimensional Heat Conduction Equation 68 Heat Conduction Equation in a Large Plane Wall 68 Heat Conduction Equation in a Long Cylinder 69 Heat Conduction Equation in a Sphere 71 Combined One-Dimensional Heat Conduction Equation 72 Modeling in Heat Transfer 5 1-3 Introduction 62 CHAPTER THREE STEADY HEAT CONDUCTION 127 3-1 Steady Heat Conduction in Plane Walls 128 The Thermal Resistance Concept 129 vii cen58933_fm.qxd 9/11/2002 10:56 AM Page viii viii CONTENTS Thermal Resistance Network 131 Multilayer Plane Walls 133 3-2 3-3 3-4 Thermal Contact Resistance 138 Generalized Thermal Resistance Networks 143 Heat Conduction in Cylinders and Spheres 146 4 Complications 268 5 Human Nature 268 5-2 5-3 Boundary Conditions 274 Multilayered Cylinders and Spheres 148 3-5 3-6 Critical Radius of Insulation 153 Heat Transfer from Finned Surfaces 156 Fin Equation 157 Fin Efficiency 160 Fin Effectiveness 163 Proper Length of a Fin 165 3-7 5-4 5-5 FOUR TRANSIENT HEAT CONDUCTION 209 Lumped System Analysis 210 Criteria for Lumped System Analysis 211 Some Remarks on Heat Transfer in Lumped Systems 213 4-2 4-3 4-4 Transient Heat Conduction in Large Plane Walls, Long Cylinders, and Spheres with Spatial Effects 216 Transient Heat Conduction in Semi-Infinite Solids 228 Transient Heat Conduction in Multidimensional Systems 231 Topic of Special Interest: Refrigeration and Freezing of Foods 23