Table Of Content

Engineering Thermodynamics Second Edition M. ACHUTHAN Director MES College of Engineering Kuttipuram, Kerala Formerly Professor of Mechanical Engineering Indian Institute of Technology Bombay New Delhi-110001 2009 ENGINEERING THERMODYNAMICS, 2nd ed. M. Achuthan © 2009 by PHI Learning Private Limited, New Delhi. All rights reserved. No part of this book may be reproduced in any form, by mimeograph or any other means, without permission in writing from the publisher. ISBN-978-81-203-3845-6 The export rights of this book are vested solely with the publisher. Fourth Printing (Second Edition) … … … October, 2009 Published by Asoke K. Ghosh, PHI Learning Private Limited, M-97, Connaught Circus, New Delhi-110001 and Printed by Rajkamal Electric Press, Plot No. 2, Phase IV, HSIDC, Kundli-131028, Sonepat, Haryana. Appendix F Contents Preface ix Chapter 1 What is Thermodynamics? 1–14 1.1 Introduction 1 1.2 Foundation of Thermodynamics 1 1.3 The Objective 3 1.4 Problem-solving 4 1.4.1 Numerical Calculations 5 1.4.2 Units 6 1.5 Some Systems 8 1.5.1 Internal Combustion (I.C.) Engine 8 1.5.2 Steam Turbine Power Plant 10 1.5.3 Heat Exchanger 11 1.5.4 Refrigerator 12 1.6 Conclusion 13 Review Questions 13 Chapter 2 Concepts of Thermodynamics 15–42 2.1 Introduction 15 2.2 Universally Primitive Concepts 15 2.2.1 System Description 15 2.2.2 System, Environment and Interactions 17 2.2.3 Classification of Systems 18 2.2.4 State and Properties 20 2.2.5 Thermodynamic Equilibrium 23 2.2.6 The Gibbs Phase Rule 24 2.2.7 Processes 24 iii iv Contents 2.3 Concepts from Properties of Matter 26 2.3.1 Empirical Temperature 27 2.3.2 Other Properties of Substances 30 2.4 Classical Thermodynamics 39 2.4.1 Models in Thermodynamics 39 2.4.2 Problems in Thermodynamics 40 2.5 Conclusion 40 Review Questions 41 Chapter 3 Work and Mechanical Energy 43–73 3.1 Introduction 43 3.2 Basic Concepts of Mechanics 43 3.2.1 Concepts from Geometry 43 3.2.2 Concepts from Kinematics 44 3.2.3 Concepts from Dynamics 44 3.3 Work 46 3.3.1 Different Modes of Work and Their Expressions 46 3.4 Evaluation of Work 52 3.4.1 Process Specification 52 3.5 Mechanical Energy 60 3.5.1 Kinetic Energy 60 3.5.2 Work–Energy Theorem 60 3.5.3 The Principle of Conservation of Energy 61 3.5.4 Conservative Force and Potential Energy 61 3.5.5 The Energy Equation 62 3.6 Expressions for Potential Energy 62 3.6.1 Gravitational Field 62 3.6.2 Electrostatic Field 63 3.6.3 Magnetic and Electromagnetic Fields 63 3.6.4 Total Energy 64 3.7 Adiabatic and Diathermal Walls 64 3.7.1 Adiabatic Wall 64 3.7.2 Diathermal (or Diathermic) Walls 65 3.7.3 Thermal Equilibrium and Heat 66 Review Questions 66 Exercises 67 Chapter 4 Temperature and Its Empirical Scales 74–84 4.1 Introduction 74 4.2 Thermal Equilibrium 75 4.3 Mathematical Development of Temperature 77 4.4 Empirical Temperature 78 Contents v 4.5 Ideal Gas Temperature 81 4.5.1 Experiments 81 4.5.2 Results and Their Interpretation 82 4.6 International Practical Temperature Scale 83 Review Questions 84 Chapter 5 The First Law of Thermodynamics 85–106 5.1 Introduction 85 5.2 Born–Carathéodory Form of the First Law 85 5.3 Characteristics of the First Law 87 5.4 Measurement of Heat 87 5.5 Characteristics of Work, Heat and Energy 89 5.6 Independent State Variables 93 5.7 Thermodynamic Models of Working Substances 93 5.8 The First Law for Cycles 94 5.9 Equilibrium 95 5.10 Examples 95 Review Questions 102 Exercises 103 Chapter 6 Energy (First Law) Equation for Flow Systems 107–133 6.1 Introduction 107 6.2 Reference Quantities 110 6.3 Simplification of Energy (First Law) Equation 111 6.4 Examples 113 Review Questions 125 Exercises 126 Chapter 7 The Second Law of Thermodynamics 134–169 7.1 Introduction 134 7.2 Preliminary Definitions 135 7.3 The Need of the Second Law 136 7.3.1 Equivalence of Work and Heat for Processes 136 7.3.2 Equivalence of Work and Heat for Cycles 136 7.4 Different Forms of the Second Law of Thermodynamics 137 7.4.1 The Kelvin–Planck Form 138 7.4.2 The Clausius Form of the Second Law 139 7.5 Use of the Second Law of Thermodynamics 141 7.6 Reversible and Irreversible Processes 142 7.7 The Carnot Theorem 144 7.8 Thermodynamic Scale of Temperature 145 7.9 Relation to Ideal Gas Temperature 147 7.10 Negative Absolute Temperatures 148 7.11 Entropy 148 7.11.1 Evaluation of Entropy Change during a Process 149 vi Contents 7.12 Clausius Inequality 150 7.12.1 The Principle of Increase of Entropy 151 7.12.2 Possible Processes 152 7.12.3 Possible Cyclic Devices 152 7.13 Adiabatic, Reversible and Isentropic Processes 153 7.14 Examples 154 7.15 Equilibrium 160 7.16 The Carathéodory Form of the Second Law 161 7.16.1 Accessible and Inaccessible States 161 7.17 The Second Law for Flow Systems 163 Review Questions 164 Exercises 165 Chapter 8 Auxiliary Functions 170–202 8.1 Introduction 170 8.2 Availability 171 8.2.1 Availability in Non-flow Processes 171 8.2.2 Availability in General Non-flow Processes 175 8.2.3 Availability in Flow Processes 176 8.2.4 Examples on Availability 177 8.3 Other Energy Functions 180 8.3.1 Internal Energy 181 8.3.2 Enthalpy 181 8.3.3 Gibbs Function 182 8.3.4 Helmholtz Function 182 8.3.5 Consequences 182 8.4 Property Relations 188 8.4.1 Maxwell Relations 191 8.4.2 Examples on Property Relations 191 8.5 Multicomponent Systems 193 Review Questions 196 Exercises 197 Chapter 9 Properties of Substances 203–247 9.1 Introduction 203 9.2 Data and Computational Procedure 203 9.2.1 Independent and Dependent Properties 203 9.2.2 Basic Data 204 9.2.3 Computational Procedure 206 9.3 Gases 210 9.3.1 Ideal Gas 210 9.3.2 Real Gases 214 9.3.3 Examples 223 Contents vii 9.4 Liquids 226 9.5 Mixture of Inert Ideal Gases 229 9.5.1 Psychrometry: Air-Water Vapour Mixtures 234 Review Questions 245 Exercises 245 Chapter 10 Thermodynamics of Combustion 248–301 10.1 Introduction 248 10.2 Major Energy Sources and Converters 248 10.3 Fuels 250 10.3.1 Coal 251 10.3.2 Liquid and Gaseous Fuels 252 10.4 Atmospheric Air 254 10.4.1 Interconversion of Mole and Mass Fractions 254 10.5 Combustion Process 258 10.6 Combustion Stoichiometry 261 10.6.1 Air Required for Combustion 263 10.6.2 Exhaust Gas Analysis 269 10.7 Reaction Equilibrium 276 10.7.1 Equilibrium Constant 276 10.7.2 Calculation of Equilibrium Composition 283 10.8 Heat Generated by Combustion 286 10.8.1 Heat of Formation 286 10.8.2 Heat of Reaction 289 10.8.3 The Calorific Value 291 10.9 Adiabatic Flame Temperature 294 Review Questions 297 Exercises 297 Chapter 11 Ideal Cycles 302–325 11.1 Introduction 302 11.2 Types of Cycles 303 11.3 Cycle Calculations 306 11.4 Cycle and Performance Parameters 309 11.4.1 Cycle Parameters 309 11.4.2 Performance Parameters 310 11.5 The Carnot Cycle 313 11.5.1 The Stirling and Ericsson Cycles 317 11.5.2 The Reversed Carnot Cycle 319 11.6 Ideal aAnd Real Cycles 322 Review Questions 322 Exercises 323 viii Contents Chapter 12 Internal Combustion (I.C.) Engine Cycles 326–344 12.1 Introduction 326 12.2 Operation of an I.C. Engine 327 12.2.1 Four-Stroke Engines 327 12.2.2 Two-Stroke Engines 328 12.3 Air-Standard Cycles 329 12.3.1 Air-Standard Otto Cycle 329 12.3.2 Air-Standard Diesel Cycle 331 12.4 Real Engines 332 12.4.1 Spark Ignition (S.I.) Engines 333 12.4.2 Compression Ignition (C.I.) Engines 335 12.4.3 The Air-Standard Dual Combustion Cycle 336 Review Questions 339 Exercises 339 Chapter 13 Brayton Cycle and Its Other Names 345–371 13.1 Introduction 345 13.2 The Brayton Cycle 346 13.2.1 Air-Standard Cycle 346 13.2.2 Basic Gas Turbine Plant 347 13.2.3 Modifications to the Basic Plant 353 13.3 Joule (Reversed Brayton) Cycle 356 13.4 The Rankine Cycle 357 13.4.1 The Basic Rankine Cycle 358 13.4.2 Modifications to the Basic Rankine Cycle 361 13.5 Vapour Compression Refrigeration Cycle— The Reversed Rankine Cycle 364 Review Questions 366 Exercises 367 Appendix A Additional Problems 373–390 Appendix B Explanatory Notes 391–409 Appendix C Problem-Solving 410–422 Appendix D Some Mathematical Principles 423–436 Appendix E Other Formulations of Thermodynamics 437–447 Appendix F Steam and R–12 Tables 448–485 Bibliography 487–488 Index 489–498 Appendix F Preface Why another book on thermodynamics? The answer to this question is simple. During every revamp of the thermodynamics course, a need is always felt for a textbook that logically and rigorously explains the subject from the first principles. Unfortunately, this need exists even today. Thermodynamics deals with energy which is a scalar quantity, while mechanics deals with forces and momenta which are vectors quantities. Hence, mathematically, thermodynamics is simpler than mechanics (even, classical (Newtonian) mechanics). In fact, all the equations of thermodynamics are algebraic and linear (mathematically, the simplest). Even then, thermodynamics is ‘judged’ to be ‘more difficult’ than mechanics. Since mechanics is taught first, it becomes ‘natural’. Thermodynamics is perceived to be more challenging as storage and flow of energy is basic to all natural processes and, therefore, the scope and variety of problems encountered become enormous. The main goal of this book is to help the reader develop ‘knowledge’ of thermodynamics. Knowledge is not something to be packed away in some corner of our brains, but what enters our being, colours our emotion, haunts our soul and is as close to us as life itself. It is over- mastering power which through the intellect moulds the whole personality, trains the emotion, and disciplines the will. Dr. S. RADHAKRISHNAN On the Plaque in Convocation Hall of IIT Bombay To provide the reader with a sound understanding of thermodynamics, the subject is developed from the first principles — clearly indicating what forms part of thermodynamics (i.e. showing what thermodynamics is and what it is not). Since this material was developed from courses offered to mechanical and electrical engineering students, equilibria (phase and reaction) are not elaborated. This material was also used as review for postgraduate students (with some additional topics, such as non-equilibrium thermodynamics, statistical mechanics, thermodynamics of combustion, direct energy conversion, which are not included here). A new Appendix containing problems from examinations of universities is added in the second edition. ix