Refrigeration and Air-Conditioning

962 Pages·2011·5.81 MB·English

by  C P Arora

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About the Author
C P Arora was formerly Professor, Department of
Mechanical Engineering, Indian Institute of Technology,
Delhi. He did his MS from the University of Illinois, USA,
under the TCM program and was the first to obtain a PhD
in engineering from the Indian Institute of Technology,
Delhi. He has guided 11 students in completing their PhD
theses. He has over 38 years of teaching experience and
has been a Visiting Faculty at the University of Leeds, UK,
and Visiting Professor at the University of Basrah, Iraq
and California State University Sacramento, USA.
Professor Arora is a life member and was the President (1979–80) of the Indian
Society of Mechanical Engineers. He was Chairman, NCST Panel of Refrigeration
and Air Conditioning (1974–86); Chairman, Organizing Committee, Fourth
National Symposium on Refrigeration and Air Conditioning (1975) and Editor of
the Journal of Thermal Engineering. He has also published a number of research
papers.
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C P Arora
Former Professor
Department of Mechanical Engineering
Indian Institute of Technology, New Delhi
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Cover: SDR
RQXYCDDFDDRAD
To
My Beloved Family
Sarla
Amitabh
Shubhra
Smita
and
Sangeeta
Contents
Preface xvii
List of Principal Symbols xxiii
Visual Preview xxvii
1. Introduction 1
1.1 A Brief History of Refrigeration 1
1.2 Systeme International d’Unites (SI Units) 4
1.3 Thermodynamic Systems, State, Properties, Processes,
Heat and Work 8
1.4 First Law of Thermodynamics 9
1.5 Second Law of Thermodynamics 11
1.6 Non-flow Processes 11
1.7 Steady-Flow Processes 12
1.8 Thermodynamic State of a Pure Substance 13
1.9 Heat Exchange Processes 16
1.10 Production of Low Temperatures 18
1.11 Saturation Pressure versus Saturation Temperature
Relationship 22
1.12 The Gaseous Phase: Equation of State 23
1.13 Clapeyron Equation 26
1.14 Property Relations 27
1.15 Thermodynamic Properties of Refrigerants 27
1.16 Modes of Heat Transfer 35
1.17 Laws of Heat Transfer 36
1.18 Electrical Analogy 39
1.19 Steady-State Conduction 42
1.20 Heat Transfer from Extended Surface 49
1.21 Unsteady-State Conduction 53
1.22 Forced Convection Correlations 54
1.23 Free Convection Correlations 55
1.24 Design of Heat Exchangers 55
1.25 Mass Transfer 57
1.26 Analogy between Momentum, Heat and Mass Transfer 58
References 60
Revision Exercises 61
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2. Refrigerating Machine and Reversed Carnot Cycle 64
2.1 Refrigerating Machines 64
2.2 A Refrigerating Machine—The Second Law Interpretation 64
2.3 Heat Engine, Heat Pump and Refrigerating Machine 67
2.4 Best Refrigeration Cycle: The Carnot Principle 71
2.5 Vapour as a Refrigerant in Reversed Carnot Cycle 80
2.6 Gas as a Refrigerant in Reversed Carnot Cycle 82
2.7 Limitations of Reversed Carnot Cycle 84
2.8 Actual Refrigeration Systems 85
Revision Exercises 86
3. Vapour Compression System 87
3.1 Modifications in Reversed Carnot Cycle with Vapour
as a Refrigerant 87
3.2 Vapour Compression Cycle 89
3.3 Vapour Compression System Calculations 91
3.4 Ewing’s Construction 99
3.5 Standard Rating Cycle and Effect of Operating Conditions 103
3.6 Actual Vapour Compression Cycle 114
3.7 Standard Rating Cycle for Domestic Refrigerators 118
3.8 Heat Pump 121
3.9 Second Law Efficiency of Vapour Compression Cycle 122
References 123
Revision Exercises 124
4. Refrigerants 128
4.1 A Survey of Refrigerants 128
4.2 Designation of Refrigerants 129
4.3 Comparative Study of Methane Derivatives in
Use Before the Year 2000 133
4.4 Comparative Study of Ethane Derivatives in Use
Before the Year 2000 134
4.5 Refrigerants in Use after the Year 2000 135
4.6 Selection of a Refrigerant 136
4.7 Thermodynamic Requirements 137
4.8 Chemical Requirements 147
4.9 Physical Requirements 150
4.10 Ozone Depletion Potential and Global
Warming Potential of CFC Refrigerants 153
4.11 Substitutes for CFC Refrigerants 154
4.12 Substitutes for CFC 12 157
4.13 Substitutes for CFC 11 169
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4.14 Substitutes for HCFC 22 170
4.15 Substitutes for CFC R 502 171
4.16 Atmospheric Gases as Substitutes for CFC Refrigerants 171
4.17 Using Mixed Refrigerants 174
4.18 Binary Mixtures 174
4.19 Classification of Mixtures 180
4.20 Evaluation of Thermodynamic Properties
of R 290/R 600a Mixtures 188
4.21 Azeotropic Mixtures 191
4.22 Use of Minimum and Maximum Boiling Azeotropes 193
4.23 Non-isothermal Refrigeration 195
4.24 Refrigerant Piping and Design 201
4.25 Lubricants in Refrigeration Systems 207
4.26 Secondary Refrigerants 208
References 210
Revision Exercises 212
5. Multipressure Systems 214
5.1 Introduction 214
5.2 Multistage or Compound Compression 214
5.3 Multi-Evaporator Systems 222
5.4 Cascade Systems 226
5.5 Solid Carbon Dioxide—Dry Ice 228
5.6 Manufacture of Solid Carbon Dioxide 228
5.7 System Practices for Multi-stage Systems 233
References 234
Revision Exercises 234
6. Refrigerant Compressors 236
6.1 Types of Compressors 236
6.2 Thermodynamic Processes During Compression 239
6.3 Volumetric Efficiency of Reciprocating Compressors 242
6.4 Effect of Clearance on Work 246
6.5 Principal Dimensions of a Reciprocating Compressor 247
6.6 Performance Characteristics of Reciprocating Compressors 248
6.7 Capacity Control of Reciprocating Compressors 253
6.8 Construction Features of Reciprocating Compressors 256
6.9 Rotary Compressors 256
6.10 Screw Compressors 257
6.11 Scroll Compressors 259
6.12 Centrifugal Compressors 260
6.13 Performance Characteristics of a Centrifugal Compressor 268
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6.14 Alternatives to R 11 (CFC 11) 274
6.15 Comparison of Performance of Reciprocating and
Centrifugal Compressors 281
References 282
Revision Exercises 283
7. Condensers 286
7.1 Heat Rejection Ratio 286
7.2 Types of Condensers 286
7.3 Heat Transfer in Condensers 288
7.4 Wilson’s Plot 300
References 301
Revision Exercises 302
8. Expansion Devices 303
8.1 Types of Expansion Devices 303
8.2 Automatic or Constant-Pressure Expansion Valve 303
8.3 Thermostatic-Expansion Valve 305
8.4 Capillary Tube and Its Sizing 311
References 317
Revision Exercises 317
9. Evaporators 319
9.1 Types of Evaporators 319
9.2 Heat Transfer in Evaporators 322
9.3 Extended Surface Evaporators 329
9.4 Augmentation of Boiling Heat Transfer 334
9.5 Pressure Drop in Evaporators 340
References 347
Revision Exercises 348
10. Complete Vapour Compression System 349
10.1 The Complete System 349
10.2 Graphical Method 349
10.3 Analytical Method 352
10.4 Newton–Raphson Method 355
10.5 Optimal Design of Evaporator 358
10.6 Installation, Service and Maintenance of
Vapour Compression Systems 359
References 365
Revision Exercises 366
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11. Gas Cycle Refrigeration 367
11.1 Limitations of Carnot Cycle with Gas as a Refrigerant 367
11.2 Reversed Brayton or Joule or Bell Coleman Cycle 367
11.3 Application to Aircraft Refrigeration 371
11.4 Ranque–Hilsch Tube 383
11.5 The Joule–Thomson Coefficient and Inversion Curve 385
11.6 Reversed Stirling Cycle 389
References 399
Revision Exercises 400
12. Vapour–Absorption System 402
12.1 Simple Vapour–Absorption System 402
12.2 Maximum Coefficient of Performance of a
Heat Operated Refrigerating Machine 403
12.3 Common Refrigerant-Absorbent Systems 405
12.4 Modifications to Simple Vapour-Absorption System 406
12.5 Actual Vapour-Absorption Cycle and its Representation
on Enthalpy-Composition Diagram 411
12.6 Representation of Vapour Absorption Cycle
1
on ln p – Diagram 419
T
12.7 Practical Single-effect Water–Lithium
Bromide Absorption Chiller 423
12.8 Double-effect H O – LiBr Absorption System 428
2 2
12.9 Electrolux Refrigerator 431
12.10 New Mixtures for Absorption System 432
References 434
Revision Exercises 435
13. Ejector-Compression System 437
13.1 Water as a Refrigerant 437
13.2 Steam Ejector System 438
13.3 Theoretical Analysis of the Steam Ejector 439
References 445
Revision Exercises 445
14. Properties of Moist Air 446
14.1 Brief History of Air Conditioning 446
14.2 Working Substance in Air Conditioning 447
14.3 Psychrometric Properties 452
14.4 Wet Bulb Temperature (WBT) 459