Fundamentals of THERMAL-FLUID SCIENCES

Transcription

1 Fundamentals of THERMAL-FLUID SCIENCES THIRD EDITION YUNUS A. CENGEL ROBERT H. TURNER Department of Mechanical JOHN M. CIMBALA Me Graw Hill Higher Education Boston Burr Ridge, IL Dubuque, IA Madison, Wl New York San Francisco St. Louis Bangkok Bogota Caracas Kuala Lumpur Lisbon London Madrid Mexico City Milan Montreal New Delhi Santiago Seoul Singapore Sydney Taipei Toronto

2 CONTENTS Preface xv Nomenclature xxiii ONE INTRODUCTION AND OVERVIEW Introduction to Thermal-Fluid Sciences 1-2 Thermodynamics and Energy Heat Transfer Fluid Mechanics Importance of Dimensions and Units * 1-6 Problem-Solving Technique 13 Summary 18 References and Suggested Readings 18 Problems 18 THREE ENERGY, ENERGY TRANSFER, AND GENERAL ENERGY ANALYSIS Introduction Forms of Energy Energy Transfer by Heat Energy Transfer by Work Mechanical Forms of Work The First Law of Thermodynamics Energy Conversion Efficiencies Energy and Environment 94 Summary 100 References and Suggested Readings 100 Problems 101 PART1 THERMODYNAMICS 21 TWO INTRODUCTION AND BASIC CONCEPTS 2-1 Systems and Control Volumes Properties of a System Density and Specific Gravity State and Equilibrium Processes and Cycles Temperature and the Zeroth Law of Thermodynamics Pressure Pressure Measurement Devices 39 Summary 47 * References and Suggested Readings 48 Problems FOUR PROPERTIES OF PURE SUBSTANCES Pure Substance 112 Phases of a Pure Substance 112 Phase-Change Processes of Pure Substances 113 Property Diagrams for Phase-Change Processes 118 Property Tables 126 The Ideal-Gas Equation of State 137 Compressibility Factor A Measure of Deviation from Ideal-Gas Behavior 139 Other Equations of State 144 Summary 149 References and Suggested Readings 150 Problems 150

3 x I Fundamentals of Thermal-Fluid Scitnces FIVE ENERGY ANALYSIS OF CLOSED SYSTEMS Moving Boundary Work Energy Balance for Closed Systems Specific Heats Internal Energy, Enthalpy, and Specific Heats of Ideal Gases Internal Energy, Enthalpy, and Specific Heats of Solids and Liquids 183 Summary 187 References and Suggested Readings 188 Problems 188 SIX MASS AND ENERGY ANALYSIS OF CONTROL VOLUMES Conservation of Mass Flow Work and the Energy of a Flowing Fluid Energy Analysis of Steady-Flow Systems Some Steady-Flow Engineering Devices Energy Analysis of Unsteady-Flow Processes 228 Summary 234 References and Suggested Readings 235 Problems The Thermodynamic Temperature Scale 7-10 The Carnot Heat Engine The Carnot Refrigerator and Heat Pump Summary 285 References and Suggested Readings 286 Problems 286 ENTROPY 297 EIGHT 8-1 Entropy The Increase of Entropy Principle Entropy Change of Pure Substances Isentropic Processes Property Diagrams Involving Entropy What is Entropy? The T ds Relations Entropy Change of Liquids and Solids The Entropy Change of Ideal Gases Reversible Steady-Flow Work Minimizing the Compressor Work Isentropic Efficiencies of Steady-Flow Devices Entropy Balance 343 Summary 354 References and Suggested Readings 355 Problems SEVEN THE SECOND LAW OF THERMODYNAMICS Introduction to the Second Law Thermal Energy Reservoirs Heat Engines Refrigerators and Heat F*umps Perpetual-Motion Machines Reversible and Irreversible Processes The Carnot Cycle The Carnot Principles 275 PART 2 FLUID MECHANICS 373 NINE INTRODUCTION TO FLUID MECHANICS The No-Slip Condition Classification of Fluid Flows A Brief History of Fluid Mechanics Vapor Pressure and Cavitation Compressibility and Speed of Sound 385

4 9-6 Viscosity Surface Tension and Capillary Effect 391 Summary 396 References and Suggested Readings 396 Problems 397 TEN FLUID STATICS Introduction Hydrostatic Forces on Submerged Plane Surfaces Hydrostatic Forces on Submerged Curved Surfaces Buoyancy and Stability 412 Summary 418 References and Suggested Readings 419 Problems 419 ELEVEN FLUID KINEMATICS Lagrangian and Eulerian Descriptions Flow Patterns and Flow Visualization Vorticity and Rotationality The Reynolds Transport Theorem 441 Summary 445 References and Suggested Readings 446 Problems 446 Contents THIRTEEN MOMENTUM ANALYSIS OF FLOW SYSTEMS Newton's Laws Choosing a Control Volume Forces Acting on a Control Volume The Linear Momentum Equation Review of Rotational Motion and Angular Momentum The Angular Momentum Equation 511 Summary 519 References and Suggested Readings Problems FOURTEEN INTERNAL FLOW Introduction Laminar and Turbulent Flows The Entrance Region Laminar Flow in Pipes Turbulent Flow in Pipes Minor Losses Piping Networks and Pump Selection 559 Summary 568 References and Suggested Readings 569 Problems 570 FIFTEEN EXTERNAL FLOW: DRAG AND LIFT 579 XI TWELVE BERNOULLI AND ENERGY EQUATIONS Mechanical Energy and Efficiency The Bernoulli Equation General Energy Equation Energy Analysis of Steady Flows 476 Summary 483 References and Suggested Readings 484 Problems Introduction Drag and Lift Friction and Pressure Drag Drag Coefficients of Common Geometries Parallel Flow Over Flat Plates Flow Over Cylinders and Spheres Lift 604 Summary 612 References and Suggested Readings 613 Problems 614

5 xii I Fundamentals of Thermal-Fluid Sciences PART 3 HEAT TRANSFER 623 SIXTEEN MECHANISMS OF HEAT TRANSFER Introduction Conduction Convection Radiation Simultaneous Heat Transfer Mechanisms 638 Summary 643 References and Suggested Readings 644 Problems 644 SEVENTEEN STEADY HEAT CONDUCTION «-3 17*-4 Steady Heat Conduction in Plane Walls 654 Thermal Contact Resistance 664 Generalized Thermal Resistance Networks 669 Heat Conduction in Cylinders and Spheres 672 Critical Radius of Insulation 678 Heat Transfer from Finned Surfaces 681 Heat Transfer in Common Configurations 696 Summary 701 References and Suggested Readings 703 Problems 703 EIGHTEEN TRANSIENT HEAT CONDUCTION Lumped System Analysis 724 Transient Heat Conduction in Large Plane Walls, Long Cylinders, and Spheres with Spatial Effects 730 Transient Heat Conduction in Semi-Infinite Solids 746 Transient Heat Conduction in Multidimensional Systems 754 Summary 762 References and Suggested Readings 763 Problems 764 NINETEEN FORCED CONVECTION Physical Mechanism of Convection Thermal Boundary Layer Parallel Flow Over Flat Plates Flow Across Cylinders and Spheres General Considerations for Pipe Flow General Thermal Analysis Laminar Flow in Tubes Turbulent Flow in Tubes 808 Summary 815 References and Suggested Readings 816 Problems 817 TWENTY NATURAL CONVECTION Physical Mechanism of Natural Convection Equation of Motion and the Grashof Number Natural Convection Over Surfaces Natural Convection from Finned Surfaces and PCBs Natural Convection Inside Enclosures 851 Summary 861 References and Suggested Readings 862 Problems 863 RADIATION HEAT TRANSFER 875 TWENTY-ONE 21-1 Introduction Thermal Radiation Blackbody Radiation Radiative Properties The View Factor Radiation Heat Transfer: Black Surfaces Radiation Heat Transfer: Diffuse, Gray Surfaces 909 Summary 922 References and Suggested Readings 924 Problems 924

6 TWENTY-TWO HEAT EXCHANGERS Types of Heat Exchangers The Overall Heat Transfer Coefficient Analysis of Heat Exchangers The Log Mean Temperature Difference Method The Effectiveness-NTU Method Selection of Heat Exchangers 968 Summary 971 References and Suggested Readings 972 Problems 973 APPENDIX 1 PROPERTY TABLES AND CHARTS (SI UNITS) 987 Table A-1 Molar mass, gas constant, and critical-point properties 988 Table A-2 Ideal-gas specific heats of various Table A-1 E common gases 989 Table A-3 Properties of common liquids, solids, Table A-2E and foods 992 Table A-4 Saturated water Temperature Table A-3E table 994 Table A-5 Saturated water Pressure table 996 Table A-4E Table A-6 Superheated water 998 Table A-7 Compressed liquid water 1002 Table A-5E Table A-8 Saturated ice-water vapor 1003 Table A-6E Figure A-9 T-s diagram for water 1004 Table A-7E Figure A-10 Mollier diagram for water 1005 Table A-8E Table A-11 Saturated refrigerant-134a Figure A-9E Temperature table 1006 Figure A-10E Table A-12 Saturated refrigerant-134a Table A-11E Pressure table 1008 Table A-13 Superheated refrigerant-134a 1009 Table A-12E Figure A-14 P-h diagram for refrigerant-134a 1011 Table A-15 Properties of saturated water 1012 Table A-13E Table A-16 Properties of saturated Figure A-14E refrigerant-134a 1013 Table A-15E Contents I xiii Ta b I e A-17 Properties of saturated ammonia 1014 Ta b I e A-18 Properties of saturated propane 1015 Table A-19 Properties of liquids 1016 Table A-20 Properties of liquid metals 1017 Ta b I e A-21 Ideal-gas properties of air 1018 Table A-22 Properties of air at 1 atm pressure 1020 Table A-23 Properties of gases at 1 atm pressure 1021 Table A-24 Properties of solid metals 1023 Table A-25 Properties of solid non-metals 1026 Table A-26 Emissivities of surfaces 1027 Figure A-27 The Moody Chart 1029 Figure A-28 Nelson-Obert generalized compressibility chart 1030 APPENDIX 2 PROPERTY TABLES AND CHARTS (ENGLISH UNITS) 1031 Molar mass, gas constant, and critical-point properties 1032 Ideal-gas specific heats of various common gases 1033 Properties of common liquids, solids, and foods 1036 Saturated water Temperature table 1038 Saturated water Pressure table 1040 Superheated water 1042 Compressed liquid water 1046 Saturated ice water vapor 1047 T-s diagram for water 1048 Mollier diagram for water 1049 Saturated refrigerant-134a Temperature table 1050 S aturated refrigerant-134a Pressure table 1051 Superheated refrigerant-134a 1052 P-h diagram for refrigerant-134a 1054 Properties of saturated water 1055

7 xiv I Fundamentals of Thermal-Fluid Sciences Ta b le A-16 E Properties of saturated refrigerant-134a 1056 Table A-17E Properties of saturated ammonia 1057 Table A-18E Properties of saturated propane 1058 Table A-19E Properties of liquids 1059 Table A-20E Properties of liquid metals 1060 Ta b I e A-21E Ideal-gas properties of air 1061 Table A-22E Properties of air at 1 atm pressure 1063 Table A-23E Properties of gases at 1 atm pressure 1064 Ta b I e A-24E Properties of solid metals 1066 Table A-25E Properties of solid non-metals 1068 Index 1069