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