Basic Engineering Thermodynamics A Venkatesh Professor Emeritus, Mechanical Engineering Department East West Institute of Technology, Bangalore, India (Formerly Professor of Mechanical Engineering, IIT Madras) ^ Universities Press
Constant Contents Chapter 1 Fundamental Concepts and Definitions 1 1.1 Introduction 1; 1.1.1 Thermodynamics 1; 1.1.2 Scope of Thermodynamics 1; 1.1.3 Microscopic and Macroscopic Thermodynamics 2; 1.1.4 Engineering Thermo dynamics 2; 1.2 System and Control Volume 3; 1.2.1 System 3; 1.2.2 Control Volume 3; 1.3 Dimensions and Units 4', 1.3.1 Primary Dimensions 4; 1.3.2 Derived Dimensions 4\ 1.3.3 Force 5; 1.4 Thermodynamic Properties 6; 1.4.1 Intensive Properties 7; 1.4.2 Extensive Properties 7; 1.4.3 Specific Properties 7; 1.4.4 Pressure 7; 1.4.5 Specific Volume 11; 1.4.6 Density 12; 1.4.7 Temperature 12; 1.5 State, Path and Process 13; 1.5.1 Thermodynamic State 13; 1.5.2 State Diagram 13; 1.5.3 State Point 13; 1.5.4 Path and Process 13; 1.5.5 Isolated System i^; 1.5.6 Adiabatic System 14; 1.5.7 Quasi-Static Process 14; 1.5.8 Non- Cyclic Process 14; 1.5.9' Cyclic Process 14; 1.6 Equilibrium i^; 1.6.1 Thermodynamic Equilibrium 14; 1.6.2 Mechanical Equilibrium 15; 1.6.3 Thermal Equilibrium 15; 1.6.4 Chemical Equilibrium 15; 1.7 Illustrative Problems 15; Problems #i Chapter 2 Work 28 2.1 Introduction 28; 2.2 Mechanics Definition of Work 28; 2.2.1 Power 29; 2.3 Thermodynamic Definition of Work 29; 2.3.1 Necessity 29; 2.3.2 Definition 50; 2.3.3 Sign Convention 30; 2.4 Displacement Work 33; 2.4.1 Quasi-Static Processes 33; 2.4.2 Evaluation of Displacement Work in Quasi-Static Processes 33; 2.4.3 Path and Point Functions 35; 2.5 Displacement Work in Resisted Processes Undergone by Systems of Uniform Pressure 36; 2.5.1 Constant Pressure Process 36; 2.5.2 Constant Volume Process 37; 2.5.3 Process p V 37; 2.5.4 Process pvn = Constant 38; 2.5.5 Piston Displacement Work 41', 2.6 Displacement Work in Unresisted Processes 44', 2.7 Other Modes of Work 44', 2.7.1 Shaft Work 44; 2.7.2 Electrical Work 46; 2.8 Illustrative Problems 4 7; Problems tfi Chapter 3 Temperature and Heat 70 3.1 Introduction 70; 3.2 Temperature 70; 3.2.1 Temperature Equilibrium 71; 3.2.2 Zeroth Law of Thermodynamics 71; 3.2.3 Significance of the Zeroth Law 72; 3.2.4 Unit of Temperature 72; 3.2.5 International Fixed Points 73; 3.3 Measurer ment of Temperature Thermometers 74; 3.3.1 Constant Volume Gas Thermometer 74; 3.3.2 Ideal Gas Temperature Scale 75; 3.3.3 Constant Pressure Gas Thernw> meter 77; 3.3.4 Mercury-in-Glass Thermometer 77 ; 3.3.5 Resistance Thermometer 78; 3.3.6 Thermocouple 79; 3.4 Heat 81; 3.4.1 Sign Convention 81; 3.4.2 Unit
viii Contents of Heat Transfer 82; 3.4.3 A Note of Caution on Heat Transfer 82; 3.5 Illustrative Problems 82; 3.6 Comparison between Work and Heat 85; Problems 86 Chapter 4 The First Law of Thermodynamics for Systems Pure Substances 90 4.1 Introduction 90; 4.2 Joule's Experiments 90; 4.2.1 Mechanical Equivalent of Heat 92; 4.2.2 Joule as the Unit of Heat Transfer 92; 4.3 Statement of the First Law of Thermodynamics 93; 4.4 Extension of the First Law of Thermodynamics to Non- Cyclic Processes ENERGY 94; 4.5 More about Energy 95; 4.5.1 Definition of Energy and Remarks 95; 4.5.2 Energy is a Property of the System 95; 4.5.3 The Nature of Energy 96; 4.6 Pure Substance 100; 4.6.1 Two-Property Rule for Pure Substances 101; 4.6.2 Energy of a Pure Substance 102; 4.6.3 Specific Heats of a Pure Substance 102; 4.7 Illustrative Problems 105; Problems 111 Chapter 5 First Law of Thermodynamics for Control Volumes 115 5.1 Introduction 115; 5.2 Extension of the First Law for a Control Volume 115; 5.3 Steady-State, Steady-Flow Energy Equation 118; 5.3.1 SS, SFEE based on Unit Mass 118; 5.3.2 SS, SFEE based on Unit Time 120; 5.3.3 SS, SFEE for Control Volumes with Multi-Streams 121; 5.3.4 Continuity Equation 123; 5.4 Application of SS, SFEE to some Specific Cases 124; 5.4.1 Adiabatic Throttling Process 124; 5.4.2 Turbines and Rotary Compressors 125; 5.4.3 Heat Transfer Equipment 126; 5.4.4 Heat Exchangers 127; 5.4.5 Nozzles and Diffusers 129; 5.5 Unsteady Flow 131; 5.6 Illustrative Problems 135; Problems 138 Chapter 6 Heat Engines The Second Law of Thermodynamics 144 6.1 Introduction 144', 6.2 Limitations of the First Law of Thermodynamics 144\ 6.3 A Steam Power Plant 146; 6.4 Closed-Cycle Gas Turbine Power Plant 149; 6.5 Refrigerator 150; 6.6 Heat Pump 152; 6.7 Heat Engine 155; 6.7.1 Direct Heat Engine 155; 6.7.2 Reversed Heat Engine 156; 6.7.3 Symbolic Representation of Heat Engines 156; 6.8 The Second Law of Thermodynamics 157; 6.8.1 The Kelvin Planck Statement of the Second Law 157; 6.8.2 The Clausius Statement of the Second Law of Thermodynamics 158; 6.8.3 Equivalence of the Kelvin Planck and Clausius Statements 159; 6.9 Key Points Discussed so Far 161; 6.10 Illustrative Problems 161; Problems 169 Chapter 7 Reversibility and the Thermodynamic Temperature Scale 171 7.1 Introduction 171; 7.2 Reversible Heat Engine 172; 7.2.1 Importance and Super iority of a Reversible Heat Engine 175; 7.3 Reversible Process 179; 7.3.1 Defini tion of a Reversible Process 179; 7.4 Irreversible Process 179; 7.4.1 Friction 180;
Contents ix 7.4.2 Unresisted Expansion 181; 7.4.3 Heat Transfer with Finite Temperature dif ference 181; 7.4.4 Combustion 182; 7.4.5 Mixing 182; 7.5 Carnot Heat Engine 182; 7.5.1 Remarks on Carnot's Engine 184; 7.6 Internal and External Reversibil ities 185; 7.7 Thermodynamic Temperature Scale 186; 7.7.1 The Concept 186; 7.7.2 Definition of the Thermodynamic Temperature Scale 189; 7.7.3 Unit of Thermo dynamic Temperature 189; 7.8 Illustrative Problems 192; Summary 199; Problems 200 Chapter 8 Entropy Available and Unavailable Energy 204 8.1 Introduction 204; 8.2 Some Important Statements on 204 ; 8.2.1 State ment 1: Clausius Inequality 205; 8.2.2 Statement 2 207; 8.2.3 Statement 3 208; 8.3 Entropy 209; 8.3.1 Remarks on Entropy 210; 8.3.2 Similarities between Energy and Entropy 210; 8.3.3 Entropy as a Coordinate 213; 8.3.4 Entropy as a Quanti tative test for Irreversibility 214; 8.3.5 Reversible and Irreversible Adiabatic Processes 216; 8.3.6 Principle of Increase of Entropy 219; 8.3.7 Entropy as a Quantitative Test of Irreversibility 219; 8.4 Evaluation of Entropy Change 220; 8.5 Carnot Cycle on the T-S Diagram 227; 8.6 Available and Unavailable Energy 228; 8.6.1 Relation between Increase in Unavailable Energy and Increase in Entropy 232; Summary 235; 8.7 Illustrative Problems 236; Problems 246 Chapter 9 Ideal Gas and Ideal Gas Mixtures 251 9.1 Introduction 251; 9.2 Ideal Gas 251; 9.2.1 Universal Gas Constant 252; 9.2.2 Internal Energy and Enthalpy of an Ideal Gas 253; 9.2.3 Specific Heats of an Ideal Gas 256; 9.2.4 Relation among Specific Heats and Gas Constant 256; 9.2.5 Perfect Gas and Semi-Perfect Gas 256; 9.3 Analysis of Some Reversible Processes 259; 9.3.1 Reversible Constant Pressure Process 259; 9.3.2 Reversible Constant Vol ume Process 260; 9.3.3 Reversible Hyperbolic Process 261; 9.3.4 Reversible Polytropic Process 262; 9.3.5 Diagrammatic Representation of Processes 265; 9.3.6 Relationship among p, V and T in a Reversible Polytropic Process 266; 9.3.7 Calculation of Entropy 269; 9.4 Ideal Gas Mixture 273; 9.4.1 Introduction 273; 9.5 Analysis of Gas Mix tures for their Composition 273; 9.5.1 Gravimetric Analysis 273; 9.5.2 Volumetric or Molar Analysis 274; 9.5.3 Dalton's Law of Additive Pressures 275; 9.5.4 Amagat's Law of Additive Volumes 276; 9.5.5 Mole-Fractions and Volume-Fractions 277; 9.5.6 Relation between Mass-Fraction and Mole-Fraction 277; 9.6 Properties of a Gaseous Mixture in terms of Properties of Individual Constituents 278; 9.6.1 Apparent Molar Mass (M) and Gas Constant (R) 278; 9.6.2 Specific Prop erties 281; 9.7 Properties of Gas Mixture Derived by Mixing Ideal Gases at Different Pressures and Temperatures 285; 9.7.1 Adiabatic Mixing of Gases Initially Existing in Separate Containers 285; 9.7.2 Non-Adiabatic Mixing 287; 9.7.3 Mixing of Gases in Steady Flow 289; 9.9 Illustrative Problems 291; Problems 310
X Contents Chapter 10 Properties of Pure Substance Water 319 10.1 Introduction 319; 10.2 Constant-Pressure Heating and Formation of Steam 320; 10.2.1 Triple Point 324; 10.2.2 Critical Point 324; 10.2.3 Enthalpy Change during Constant-Pressure Heating 324; 10.3 Frequently Used Terms and their Definitions 325; 10.4 Phase Change Diagrams 327; 10.4.1 p-v Diagram 327; 10.4.2 Mollier Diagram 331; 10.4.3 Dryness Fraction 332; 10.4.4 Evaluation of Other Properties in the Mixture Region 334; 10.4.5 Table of Properties for Water 334; 10.4.6 How to Fix the States in Different Phase Regions and Evaluate other Prop erties 349; 10.4.7 Experimental Determination of Dryness Fraction of Steam 356; 10.5 Analyses of Some Processes Undergone by Steam 359; 10.6 Illustrative Problems 364; Problems 387 Chapter 11 Real Gas 392 11.1 Introduction 392; 11.2 Real Gas Compressibility Factor 392; 11.3 Reduced Properties Law of Corresponding States 394; H-4 Generalized Compressibility Chart 397; 11.5 Other Equations of State 399; 11.5.1 van der Waals Equation of State 399; 11.5.2 Redlich and Kwong Equation of State 405; 11.5.3 Beattie-Bridgeman Equation 405; 11.5.4 Virial Equations of State 406; Problems 408 Chapter 12 Fuels and Combustion 410 12.1 Introduction 410; 12.2 Fuels 410; 12.2.1 Fuel Analysis 411; 12.3 Com bustion 413; 12.3.1 Complete Combustion 414', 12.3.2 Incomplete Combustion 414j 12.3.3 Stoichiometric Air 414', 12.3.4 Dry Air 415; 12.3.5 Estimation of Stoichiomet ric Air 415; 12.3.6 Excess Air 417; 12.3.7 % Theoretical Air 417; 12.4 Analysis of Combustion Products 419; 12.4.1 The Orsat Apparatus ^19; 12.4.2 Finding Actual Air using Orsat Analysis 421; 12.5 First Law of Thermodynam ics for a System Applied to Combustion 4%6; 12.5.1 U t Diagram for a Combustion Process 4^7; 12.5.2 Internal Energy of Reaction 429; 12.6 First Law of Thermody namics for a Control Volume Applied to Combustion 430; 12.6.1 H t Diagram for a Combustion Process 430; 12.6.2 Enthalpy of Reaction 431; 12.7 Relation between AH'pt and Af7^ 433; 12.7.1 Effect of Phase on AH' and AU' 434; 12.8 Enthalpy of Formation 436; 12.9 Adiabatic Combustion Temperature 439; 12.10 Calorific Value 442; 12.11 Illustrative Problems 443; Problems 455 Objective Type Questions Bibliography Index 458 481 483