engineering thermodynamics - springer978-94-010-9316-3/1.pdf · engineering thermodynamics si...
TRANSCRIPT
Engineering Thermodynamics
Engineering Thermodynamics
SI Edition
Dwight C. Look, Jr. Harry J. Sauer, Jr.
UNIVERSITY OF MISSOURI-ROLLA
51 Edition prepared by GRAHAM I. ALEXANDER
Liverpool Polytechnic
International
First published in the USA by PWS Publishers, 20 Park Plaza, Boston, Massachusetts 02116
© 1986 PWS Publishers, Wadsworth Inc., Belmont, California 94002 © 1988 SI edition Van Nostrand Reinhold (International) Co. Ltd
ISBN- \3: 978-0-278-00052-0 e-ISBN- \3: 978-94-010-9316-3 001: 10.1007/978-94-010-9316-3
All rights reserved. No part of this work covered by the copyright hereon may be reproduced or used in any form or by any means-graphic, electronic, or mechanical, including photocopying, recording, taping, or information storage or retrieval systemswithout the written permission of the publishers.
British Library Cataloguing in Publication Data Look, Dwight, C.
Engineering thermodynamics.-SI ed. I. Heat engineering. Thermodynamics I. Title II. Sauer, Harry J. /935-621.402' 1
Preface
Energy-its discovery, its availability, its use-concerns all of us in general and the engineers of today and tomorrow in particular. The study of thermodynamics-the science of energy-is a critical element in the education of all types of engineers. Engineering Thermodynamics provides a thorough introduction to the art and science of engineering thermodynamics. It describes in a straightforward fashion the basic tools necessary to obtain quantitative solutions to common engineering applications involving energy and its conversion, conservation, and transfer.
This book is directed toward sophomore, junior, and senior students who have studied elementary physics and calculus and who are majoring in mechanical engineering; it serves as a convenient reference for other engineering disciplines as well. The first part of the book is devoted to basic thermodynamic principles, essentially presented in the classic way; the second part applies these principles to many situations, including air conditioning and the interpretation of statistical phenomena.
Chapters 1 through 4 discuss the fundamentals and basic concepts of thermodynamics with emphasis on the properties of common liquids, vapors, and gases. Chapter 5 presents the first law of thermodynamics in its various operational forms. This is one of the most important chapters of the book. Chapters 6 and 7 deal with the elusive second law of thermodynamics and its restricting nature. Chapter 8 consists of examples of simple thermal systems using thermodynamics principles, and Chapter 9 introduces some of the complications of systems in use today. The quality of energy is the subject of Chapter 10. This subject is not new, but it is not emphasized sufficiently in most beginning courses. Chapter 11 is probably the most mathematical chapter in the book. It presents various relationships among properties and discusses Maxwell's relations and the criterion of equilibrium. Chapter 12 covers mixtures and psychrometrics and their relationship to environmental control. Reacting systems (combustion) are briefly covered in Chapter 13. Chapter 14 presents the engineering applications of
v
vi Preface
thermodynamics in heating and air conditioning, and Chapter 15 covers thermofluid mechanics.
Chapter 16, the last chapter of this book, is devoted to the statistical interpretation of thermodynamics. At first glance, it may seem somewhat unorthodox to present this topic in a predominately classical thermodynamics book. Nevertheless, we believe that this brief coverage should be made available to those who wish to examine statistical evidence that the results conform to the rules, laws, and definitions presented in classical thermodynamics.
The appendices are divided into three sections: A, B, and C. Appendices A-I to A-6 are tables of physical constants and properties; of particular importance are the abbreviated steam tables (in both SI and English units). Appendix B presents some historical notes about famous people who contributed to the science of thermodynamics. Appendix C comprises nomenclature and conversion tables.
SI units are used in conjunction with English units in this text. Our intent is to allow the student to become comfortable with both systems. In addition, the text promotes computer use for thermodynamic analysis, which is becoming increasingly common among today's engineers.
To truly understand thermodynamics and its applications, one must be able to efficiently solve related problems. For this reason, we have provided homework problems at the end of each chapter. The text also includes a large number of examples, which should be studied carefully. Our approach in this regard is based on what Confucius reportedly said:
I hear, and I forget ... I see, and I remember ... I do, and I understand
Acknowledgments
It is impossible to acknowledge all the people who have, in one way or another, contributed to this book. Occasionally, the sources of many good ideas, examples, problems, approaches, and techniques have long been forgotten. However, we trust that adequate recognition is given throughout the text to informational sources.
Special thanks go to Carl MacPhee, Director of Publications of the American Society of Heating, Refrigerating and Air-Conditioning Engineers, for permission to make extensive use of ASHRAE's developments in applied thermodynamics and psychrometrics. Moreover, we appreciate the efforts of the teachers and many students who assisted the development of this text and its classroom testing. Their suggestions and their encouragement contributed greatly to the completion of the book. Thank you. Also, we especially thank the following manuscript reviewers for their many helpful suggestions: O. Arnas, Louisiana State University; Peter Botros, South Dakota State University; Nicholas P. Cernansky, Drexel University; Mario Colaluca, Texas A&M University; George Craig, San Diego State University; Philip Gerhart, University of Evansville; Ramon Hosler, University of Central Florida; Peter E. Jenkins, Engine Corpora-
Preface vii
tion of America; P. E. Liley, Purdue University; Robert Lott, Vanderbilt University; Eugene L. Keating, United States Naval Academy; Eugene Martinez, Lamar University; Robert Peck, Arizona State University; Edward Perry, Memphis State University.
Preface to 51 Edition
D.C. Look, Jr. H.J. Sauer, Jr.
In this SI edition, much of the text remains unchanged, except the appendices which have, of course, been fully converted. A table of critical constants has also been added.
Obviously, the short section on units had to be completely rewritten, and the useful concept of 'unity brackets' has been introduced. Furthermore, wherever appropriate, the worked examples in the text now make use of unity bracket manipulations. Although SI units are used throughout, one or two non-SI terms have been retained in view of their hackneyed or established use. These include the familiar 'ton of refrigeration' and EER (energy efficiency ratio). Both these terms are widely used in industry and thus, although a little incongruous, it would seem unwise to exclude them; their definitions being fully described in the appropriate section of the text.
All the previous worked and unworked problems have been retained and converted fully to SI units. However, it must be pointed out that in very few cases have simple conversions been made. The majority of problems, particularly those involving steam or refrigerants, have been given new data. The solutions have been completely reworked using, where possible, data in the appendices. Teachers can thus be confident when extracting problems for class use from the wealth of unworked examples (averaging over 50 per chapter) at the end of each chapter.
The preparation of this SI edition has also afforded the opportunity to make any necessary corrections, although the character of the original book remains unaltered. Inevitably some errors will have escaped detection and notification of these together with, of course, any constructive criticism will always be greatly appreciated.
Acknowledgement of help received in the preparation of this edition is due to my colleagues, Mr C. J. Tate at Liverpool, for many helpful discussions, and Dr J. R. Nichols at UMIST, Manchester, for his many useful suggestions and provision of software to help convert the appendices. Furthermore due gratitude must go to John Wiley and Sons, Publishers, for their kind permission to reproduce some tables and charts in SI units. Finally I wish to thank my wife and family for their forebearance during my absent-minded presence, over the period of preparation of the manuscript, which of necessity involved a lot of work in a relatively short space of time.
G. I. Alexander School of Engineering,
Liverpool Polytechnic
Contents
1 Fundamental Concepts and Definitions 1
1-1 The Nature of Thermodynamics 1 Some History 2 Uses of Thermodynamics 3 System and Surroundings 3 Analysis and Problem Solving 7
1-2 Definition of Units 8 1-3 Properties 9
Specific Volume or Density 10 Pressure 11 Temperature and Temperature
Scales 13 Internal Energy 20 Enthalpy 20 Entropy 21
1-4 States 22 1-5 Processes 23
Reversible Process 23 Process Indicators 24 Irreversible Process 25 Polytropic Process 26
1-6 Point and Path Functions 28 1-7 Conversation of Mass 29 1-8 Chapter Summary 32 Problems 33
2 Physical Properties 37
2-1 Phases of a Pure Substance 37 2-2 Equilibrium of a Pure Substance 38
ix
2-3 Equilibrium Thermodynamic Properties: An Example 39
2-4 Thermodynamics Surfaces 41 Phase Diagrams 42 Other Useful Diagrams 42 Typical Values of Characteristic
Points 43 Table of Properties 45 Steam ,47 Closure on Steam 49 Refrigerant: R-12 51
2-5 Specific Heats and Latent Heat of Transformation 53
2-6 Chapter Summary 56 Problems 57
3 Gases 62 3-1 Ideal Gas 62
Equation of State 63 Properties of Ideal Gases 65
3-2 Alternate Approximate Equations of State 73
Clausius Gas 74 van der Waals Gas 74 Other Forms 74
3-3 Real Gases 77 Reduced Coordinates 81
3-4 Mathematical Preparation 85 Basic Operations and Definitions 85
X Contents
Coefficients of Thermal Expansion, Compressibility, and Isothermal Bulk Modulus 88
3-5 Fundamental Relations 91 3-6 Chapter Summary 96 Problems 97
4 Forms of Energy 4-1 Forms of Energy 10 1 4-2 Work 102 l:l-3 Closure on Work 110 4-4 Heat 112
101
4-5 Reversible Adiabatic Process 4-6 Heat Capacity 113 4-7 Stored (Possessed) Forms of
Energy 116 Thermal (Internal) Energy, U Potential Energy, PE 116 Kinetic Energy, KE 117 Chemical Energy, Ee 117 Nuclear Energy, EN 117
4-8 Chapter Summary 117 Problems 119
5 The First Law of Thermodynamics 121
5-1 The First Law of Thermodynamics 121
112
116
First Law for Closed Systems 121 Consequences of the First Law for
Closed Systems 129 Consequences of the First Law for
Open Systems 129 5-2 Guidelines for Thermodynamics, or
Energy, Analysis 143 5-3 Alternate Forms of u and h 143 Appendix for Chapter 5 148 5-4 Chapter Summary 151 Problems 153
6 Thermodynamic Systems and Cyclic Processes 159
6-1 Heat Engines and Thermal Efficiency 159
6-2 Heat Pumps and Refrigerators 161 6-3 Reservoirs 163
6-4 Processes and Cycles-Reversible and Irreversible 163
Reversible Processes 164 Causes of Irreversibility 164
6-5 The Carnot Cycle 164 Cycle 164 Efficiency 167
6-6 Chapter Summary 171 Problems 172
7 The Second Law of Thermodynamics 175
7-1 The Second Law of Classical Thermodynamics 175
7-2 Corollaries to the Second Law 7-3 The Second Law and Statistical
Thermodynamics 181 7 -4 The Physical Meaning of
Entropy 182 7-5 More on Corollaries A, B, and
C 183 7-6 More on Corollary D 184 7-7 More on Corollary E 186 7-8 More on Corollary F 188 7-9 Entropy: The Working
Definition 191
177
Second Law for Closed Systems 191 Entropy Used as a Coordinate 192 Relevant Thermodynamic
Relations 195 Computing Entropy Changes from
Measurable Properties 200 A Word about Irreversible
Processes 203 Principle of the Increase of
Entropy 203 Open System 207
7-10 Chapter Summary 212 Problems 215
8 Basic Systems and Cycles 223 8-1 Elements of Thermal Systems 223
Expansion or Compression Work in a Cylinder 226
The Porous Plug and the JouleThomson Coefficient 228
Turbines, Pumps, Compressors, and Fans 232
Heat Transfer Equipment (Heat Exchangers) 244
Nozzles and Diffusers 251 Throttling Devices (Valves, Orifices,
Capillary Tubes 254 Summary of Component
Operation 256 8-2 Rankine Cycle 257
The Cycle 261 Thermal Efficiency 263 Improvements in the Cycle 263
8-3 Air-Standard Cycles 268 Brayton Cycle 268 Otto Cycle 277 Diesel Cycle 281 Other Cycles 283
8-4 Refrigerator and Heat Pump Cycles 287
Vapor-Compression Cycle 289 Heat Pumps 292 Ammonia-Absorption Cycle 295
8-5 Additional Applications 295 8-6 Chapter Summary 297 Problems 299
9 Power Cycle Improvements and Innovations 308
9-1 Review of Basic Information 308 9-2 Improving the Rankine Cycle 308
Reheating 308 Regeneration 317
9-3 Improving the Brayton Cycle 323 Regeneration 323 Multistage Improvements 324 Two-Shaft Arrangements 330 Heat Recovery Systems 330 Brayton Cycle Systems with
Compressed Air Energy Storage (CAES) 330
9-4 Combined Steam and Gas Cycles (STAG, COGAS) 333
9-5 Cogeneration/Total Energy Systems (TES) 336
Prime Movers for Cogeneration 338 Modular Integrated Utility Systems
(MIUS) 339 Magnetohydrodynamics (MHD) 340 Waste Heat Recovery from
Engines 342
Contents xi
9-6 Nuclear Thermal Power Cycles 344 Fission Plants 345 Breeder Reactors 345 Fusion Plants 350
9-7 Solar Power Systems 351 Solar Thermal Power Systems 352 Photovoltaic Systems 354 Wind Energy 355 Ocean Thermal Energy Conversion
(OTEC) 357 Hydroelectric Power 358 Biomass Energy Systems 358
9-8 Geothermal Power Systems 358 Dry-Steam Systems 359 Hot-Water Systems 359 Hot-Rock Systems 361
9-9 Improving the Vapor Compression Cycle 361
9-10 Chapter Summary 362 Problems 363
10 Availability and Irreversibility
10-1 General Concepts 372 10-2 Available Part of Internal
Energy 375 10-3 Available Part of Kinetic and
Potential Energy 376 10-4 Available Part of How Work 376 10-5 Availability of Closed Systems 376 10-6 Availability in Steady How 376 10-7 Availability of Heat 377 10-8 Reversible Work 378 10-9 Irreversibility and Lost Work 379 10-10 Measures of Efficiency 388 10-11 Comments on Dead State-
Selection 394 10-12 Availability-Irreversibility Analysis of
Vapor-Compression Refrigeration 395
10-13 Availability-Irreversibility Analysis of Air Conditioning Systems 401
10-14 Summary 405 Problems 406
11 More Thermodynamic Relations 411
11-1 Maxwell's Relations 412 11-2 Property Relations 415
372
xii Contents
11-3 Characteristic Function 420 11-4 Changing Phase-Clapeyron
Equation 420 11-5 Equations of State 426 11-6 Developing Thermodynamic Property
Tables 427 Determination of Entropy 427 Determination of Internal Energy and
Enthalpy 429 11-7 Specific Development of Refrigerant
Property Values 429 11-8 Criterion for Equilibrium 432 11-9' Chapter Summary 434 Problems 435
12 Mixtures and Psychrometries 437 12-1 Mixtures 437
Ideal Gases 437 Real Gases 444 Closure 445
12-2 Psychrometrics 446 Basic Definitions 446 The Psychrometric Chart 453
12-3 Basic Air Conditioning Processes 462
Psychrometric Representations 462 Absorption of Space-Heat and
Moisture Gains 464 Heating or Cooling of Air 464 Cooling and Dehumidifying of
Air 464 Heating and Humidifying Air 465 Adiabatic Mixing of Two Streams of
Air 466 Adiabatic Mixing of Moist Air with
Injected Water 466 Moving Air 466 Approximate Equations Using
Volume How Rates 467 12-4 Chapter Summary 470 Problems 471
13 Elements of Combustion 481 13-1 Background 481
Fundamentals of Combustion 482 13-2 Fuels 483
Vapor Fuels 483 Liquid Fuels 483
Solid Fuels 485 13-3 Combustion Equations 486 13-4 Combustion Calculations 491
The Mol 491 Stoichiometry 492
13-5 Thermochemistry 496 First Law for Reacting Systems 497 Adiabatic Hame Temperature 505
13-6 Chemical Equilibrium and Dissociation 507
Reversible Reactions 507 Gibbs and Helmholtz Functions and
Equilibrium 508 Equilibrium Constant and the van't
Hoff Equation 509 13-7 Combustion Efficiency 518 13-8 Fuel! Air Cycle Approximation 519 13-9 Other Considerations with
Combustion Processes 523 Air Pollution 523 Corrosion and Acid Rain (Pollution
on Exterior Surfaces) 523 13-10 Chapter Summary 524 Problems 525
14 Refrigeration Systems and Heat Pumps 529
14-1 Vapor-Compression Cycle and Components 529
Heat Pumps 534 Annual Cycle Energy System
(ACES) 537 Compressors 539 Condensers 543 Evaporators 547 Expansion Devices 551
14-2 Absorption Refrigeration and Heat Pumps 553
14-3
14-4 14-5
Absorption Cycles 553 Lithium-Bromide-Water
Equipment 556 Aqua-Ammonia (Ammonia-Water)
Equipment 560 Absorption-Cycle Heat Pumps 563 Air-Cycle Refrigeration 567 Aircraft Cooling 569 Vortex Tube Refrigeration 574 Ejector Refrigeration (Hash
Cooling) 577
Automotive Applications 581 Solar-Powered Jet Refrigerator 582
14-6 Chapter Summary 584 Problems 584
15 Thermofluid Mechanics 592
15-1 Basic Concepts of Fluid Flow 592 Types of Fluids 593 Continuity Relation 594 Reynolds Number 594 Mach Number 594 Flow Regimes 594 Boundary Layers 595 Bernoulli Equation 596 Euler Equation 596 Nonisothermal Effects 597 Stagnation 597
15-2 Velocity of Sound 598 15-3 Isentropic Flow 600
Ideal Gases 602 15-4 Applications of Isentropic Flow 608 15-5 Constant Area Adiabatic Flow with
Friction 612 The Momentum Relation 613 Ideal Gases 617
15-6 Constant Area Flow with Heat Exchange 618
15-7 Shock VVaves 620 Ideal Gases 622
15-8 Propulsion Principles 624 Momentum Principles and
Thrust 624 Propulsion Devices 626
15-9 Turbomachinery 629 Turbines 629 Axial Flow Compressors 638
15-10 Chapter Summary 641 Appendix for Chapter 15 643 Problems 645
16 Introduction to Kinetic Theory and Statistical Thermodynamics 648
16-1 Kinetic Theory 649 Equipartition 653
16-2 Distribution of Particle Velocities 656
16-3 Microstate and Macrostate 663 16-4 Thermodynamic Probability 664
Contents xiii
Maxwell-Boltzmann Model 665 Bose-Einstein Model 665 Fermi-Dirac Model 666
16-5 Equilibrium Conditions 667 Maxwell-Boltzmann Model 667 Bose-Einstein Model 668 Fermi-Dirac Model 668
16-6 Relationship of the Three Types of Statistical Models 671
16-7 Most Probable Distribution Stability 672
16-8 Entropy and the Statistical Approach 673
16-9 Partition Function and Entropy 673 Maxwell-Boltzmann Entropy 674 Bose-Einstein Entropy 676 Fermi-Dirac Entropy 677
16-10 The Partition Function and Thermodynamic Properties 678
'16-11 Compilation of the Partition Functions 679
Heisenberg's Uncertainty Principle 679
Degeneracy in Phase Space 681 Particle Energy, £, 682
16-12 Monatomic Particles 683 16-13 Simple Oscillating Particles 686 16-14 Diatomic Particles 687 16-15 Closure on Specific Heats of Solids
An Improved Theory 689 16-16 Closure on Specific Heats of Gases
(Ideal Gas) 692 16-17 Specific Heat of Electrons in
Conductors 694 16-18 Photon "Gas" 698 16-19 Chapter Summary 702 Problems 705
Appendices 709
A-I Steam Tables 711 Table A-I-I Saturated Steam:
Temperature Table (SI) 712 Table A-I-2 Saturated Steam:
Pressure Table (SI) 716 Table A-I-3 Superheated Steam
(SI) 720 Table A-I-4 Thermodynamic
Property Calculations of Steam 726 A-2 Refrigerant-12 Tables 737
Table A-2-1 Saturated Refrigerant-12:
xiv Contents
Temperature Tables (SI) 738
Table A-2-2 Superheated Refrigerant-12 Table (SI) 740
A-3 Air Tables 744 Table A-3-1 Low-Density Air
(SI) 746 Tale A-3-2 Saturated Air:
Temperature Table (SI) 751 Table A-3-3 Saturated Air: Pressure
Table (SI) 753 Table A-3-4 Superheated Air
(SI) 754 A-4 Nitrogen Tables 756
Table A-4-1 Saturated Nitrogen (N2):
Temperature Table 756
Table A-4-2 Superheated Nitrogen 757
A-5 Critical Constants Table A-6 Approximate Values of c12 ' cv ,
and R 760 B More History 761 C Nomenclature and Conversion
Factors 767
Bibliography 771
Answers to Selected Problems
Index 777
773