Refrigeration Systems and Applications

 
 
Wiley (Verlag)
  • 3. Auflage
  • |
  • erschienen am 23. März 2017
  • |
  • 752 Seiten
 
E-Book | ePUB mit Adobe-DRM | Systemvoraussetzungen
978-1-119-23078-6 (ISBN)
 
The definitive text/reference for students, researchers and practicing engineers
This book provides comprehensive coverage on refrigeration systems and applications, ranging from the fundamental principles of thermodynamics to food cooling applications for a wide range of sectoral utilizations. Energy and exergy analyses as well as performance assessments through energy and exergy efficiencies and energetic and exergetic coefficients of performance are explored, and numerous analysis techniques, models, correlations and procedures are introduced with examples and case studies. There are specific sections allocated to environmental impact assessment and sustainable development studies. Also featured are discussions of important recent developments in the field, including those stemming from the author's pioneering research.
Refrigeration is a uniquely positioned multi-disciplinary field encompassing mechanical, chemical, industrial and food engineering, as well as chemistry. Its wide-ranging applications mean that the industry plays a key role in national and international economies. And it continues to be an area of active research, much of it focusing on making the technology as environmentally friendly and sustainable as possible without compromising cost efficiency and effectiveness.
This substantially updated and revised edition of the classic text/reference now features two new chapters devoted to renewable-energy-based integrated refrigeration systems and environmental impact/sustainability assessment. All examples and chapter-end problems have been updated as have conversion factors and the thermophysical properties of an array of materials.
* Provides a solid foundation in the fundamental principles and the practical applications of refrigeration technologies
* Examines fundamental aspects of thermodynamics, refrigerants, as well as energy and exergy analyses and energy and exergy based performance assessment criteria and approaches
* Introduces environmental impact assessment methods and sustainability evaluation of refrigeration systems and applications
* Covers basic and advanced (and hence integrated) refrigeration cycles and systems, as well as a range of novel applications
* Discusses crucial industrial, technical and operational problems, as well as new performance improvement techniques and tools for better design and analysis
* Features clear explanations, numerous chapter-end problems and worked-out examples
Refrigeration Systems and Applications, Third Edition is an indispensable working resource for researchers and practitioners in the areas of Refrigeration and Air Conditioning. It is also an ideal textbook for graduate and senior undergraduate students in mechanical, chemical, biochemical, industrial and food engineering disciplines.
weitere Ausgaben werden ermittelt
Ibrahim Dincer, PhD, is a full professor of Mechanical Engineering in the Faculty of Engineering and Applied Science at UOIT and a leading authority in the area of sustainable energy systems, including refrigeration systems and applications. He is Vice President for Strategy in International Association for Hydrogen Energy (IAHE) and Vice-President for World Society of Sustainable Energy Technologies (WSSET). Renowned for his pioneering works in the area of sustainable energy technologies, Professor Dincer has authored and co-authored numerous books and book chapters, more than a thousand refereed journal and conference papers, and many technical reports. He has chaired many national and international conferences, symposia, workshops and technical meetings and has delivered more than 300 keynote and invited lectures. Professor Dincer is an active member of various international scientific organizations and societies, and serves as editor-in-chief, associate editor, regional editor, and editorial boardmember on various prestigious international journals. He is a recipient of several research, teaching and service awards, including the Premier's research excellence award in Ontario, Canada, in 2004. Professor Dincer has made innovative contributions to the understanding and development of sustainable energy technologies and their implementation. He has actively been working in the areas of hydrogen and fuel cell technologies, and his group has developed various novel technologies/methods, etc. Furthermore, he has been recognized by Thomson Reuters as one of the World's Most Influential Scientific Minds in Engineering in 2014, 2015 and 2016.
  • Cover
  • Title Page
  • Copyright
  • Contents
  • Preface
  • Acknowledgments
  • Chapter 1 General Aspects of Thermodynamics
  • 1.1 Introduction
  • 1.2 Dimensions and Units
  • 1.2.1 Systems of Units
  • 1.2.1.1 Mass
  • 1.2.1.2 Length
  • 1.2.1.3 Force
  • 1.2.1.4 Density and Specific Volume
  • 1.2.1.5 Mass Flow Rate and Volumetric Flow Rate
  • 1.2.1.6 Temperature
  • 1.2.1.7 Pressure
  • 1.3 Thermodynamics
  • 1.3.1 Thermodynamic Systems
  • 1.3.2 Thermodynamic Laws
  • 1.3.3 First Law of Thermodynamics
  • 1.3.4 Second Law of Thermodynamics
  • 1.3.4.1 Exergy and its Importance
  • 1.3.4.2 Reversibility and Irreversibility
  • 1.3.4.3 Reversible Work and Exergy Destruction
  • 1.3.5 Dincer's Six-step Approach
  • 1.3.6 Pure Substances
  • 1.3.6.1 State and Change of State
  • 1.3.6.2 Vapor States
  • 1.3.6.3 Sensible Heat, Latent Heat and Latent Heat of Fusion
  • 1.3.6.4 Specific Heat
  • 1.3.6.5 Specific Internal Energy
  • 1.3.6.6 Specific Enthalpy
  • 1.3.6.7 Specific Entropy
  • 1.3.6.8 Energy Change and Energy Transfer
  • 1.3.6.9 Flow Energy
  • 1.3.6.10 Heat Transfer
  • 1.3.6.11 Work
  • 1.3.6.12 Thermodynamic Tables
  • 1.4 Ideal and Real Gases
  • 1.5 Refrigerators and Heat Pumps
  • 1.5.1 The Carnot Refrigerators and Heat Pumps
  • 1.6 Psychrometrics
  • 1.6.1 Common Definitions in Psychrometrics
  • 1.6.2 Balance Equations for Air and Water Vapor Mixtures
  • 1.6.3 The Psychrometric Chart
  • 1.7 Concluding Remarks
  • Nomenclature
  • Study Problems
  • References
  • Chapter 2 Refrigerants
  • 2.1 Introduction
  • 2.2 Classification of Refrigerants
  • 2.2.1 Halocarbons
  • 2.2.2 Hydrocarbons
  • 2.2.3 Inorganic Compounds
  • 2.2.3.1 Ammonia (R-717)
  • 2.2.3.2 Carbon dioxide (R-744)
  • 2.2.3.3 Air (R-729)
  • 2.2.4 Azeotropic mixtures
  • 2.2.5 Nonazeotropic mixtures
  • 2.3 Prefixes and Decoding of Refrigerants
  • 2.3.1 Prefixes
  • 2.3.2 Decoding the Number
  • 2.3.3 Isomers
  • 2.4 Secondary Refrigerants
  • 2.5 Refrigerant-absorbent Combinations
  • 2.6 Stratospheric Ozone Layer
  • 2.6.1 Stratospheric Ozone Layer Depletion
  • 2.6.2 Ozone Depletion Potential
  • 2.6.3 Montreal Protocol
  • 2.7 Global Warming
  • 2.7.1 Global Warming Potential
  • 2.8 Clean Air Act
  • 2.8.1 Significant New Alternative Policies Program
  • 2.8.2 Classification of Substances
  • 2.9 Key Refrigerants
  • 2.9.1 R-134a
  • 2.9.2 R-123
  • 2.9.3 Nonazeotropic (Zeotropic) Mixtures
  • 2.9.4 Azeotropic Mixtures
  • 2.9.5 Ammonia (R-717)
  • 2.9.6 Propane (R-290)
  • 2.9.7 Carbon Dioxide (R-744)
  • 2.10 Selection of Refrigerants
  • 2.11 Thermophysical Properties of Refrigerants
  • 2.12 Lubricating Oils and their Effects
  • 2.13 Concluding Remarks
  • Study Problems
  • References
  • Chapter 3 Refrigeration System Components
  • 3.1 Introduction
  • 3.2 History of Refrigeration
  • 3.3 Main Refrigeration Systems
  • 3.4 Refrigeration System Components
  • 3.5 Compressors
  • 3.5.1 Hermetic Compressors
  • 3.5.2 Semi-hermetic Compressors
  • 3.5.3 Open Compressors
  • 3.5.4 Classification of Compressors
  • 3.5.5 Positive Displacement Compressors
  • 3.5.5.1 Reciprocating Compressors
  • 3.5.5.2 Rotary Compressors
  • 3.5.6 Dynamic Compressors
  • 3.5.6.1 Centrifugal Compressors
  • 3.5.6.2 Axial Compressors
  • 3.5.7 Thermodynamic Analysis of Compressor
  • 3.5.8 Compressor Capacity and Performance Assessment
  • 3.5.8.1 Compression Ratio
  • 3.5.8.2 Compressor Efficiency
  • 3.5.8.3 Compressor Capacity Control for Better Performance
  • 3.6 Condensers
  • 3.6.1 Water-cooled Condensers
  • 3.6.2 Air-cooled Condensers
  • 3.6.3 Evaporative Condensers
  • 3.6.4 Cooling Towers
  • 3.6.5 Thermodynamic Analysis of Condenser
  • 3.7 Evaporators
  • 3.7.1 Liquid Coolers
  • 3.7.2 Air and Gas Coolers
  • 3.7.3 Thermodynamic Analysis of Evaporator
  • 3.8 Throttling Devices
  • 3.8.1 Thermostatic Expansion Valves
  • 3.8.2 Constant Pressure Expansion Valves
  • 3.8.3 Float Valves
  • 3.8.4 Capillary Tubes
  • 3.8.5 Thermodynamic Analysis of Throttling Valve
  • 3.9 Auxiliary Devices
  • 3.9.1 Accumulators
  • 3.9.2 Receivers
  • 3.9.3 Oil Separators
  • 3.9.4 Strainers
  • 3.9.5 Dryers
  • 3.9.6 Check Valves
  • 3.9.7 Solenoid Valves
  • 3.9.8 Defrost Controllers
  • 3.10 Concluding Remarks
  • Nomenclature
  • Study Problems
  • References
  • Chapter 4 Refrigeration Cycles and Systems
  • 4.1 Introduction
  • 4.2 Vapor-compression Refrigeration Systems
  • 4.2.1 Evaporation
  • 4.2.2 Compression
  • 4.2.3 Condensation
  • 4.2.4 Expansion
  • 4.3 Energy Analysis of Vapor-compression Refrigeration Cycle
  • 4.4 Exergy Analysis of Vapor-compression Refrigeration Cycle
  • 4.5 Actual Vapor-compression Refrigeration Cycle
  • 4.5.1 Superheating and Subcooling
  • 4.5.1.1 Superheating
  • 4.5.1.2 Subcooling
  • 4.5.2 Defrosting
  • 4.5.3 Purging Air in Refrigeration Systems
  • 4.5.3.1 Air Purging Methods
  • 4.5.4 Twin Refrigeration System
  • 4.6 Air-standard Refrigeration Systems
  • 4.6.1 Energy and Exergy Analyses of a Basic Air-standard Refrigeration Cycle
  • 4.7 Absorption Refrigeration Systems
  • 4.7.1 Basic Absorption Refrigeration Systems
  • 4.7.2 Ammonia-water (NH3-H2O) Absorption Refrigeration Systems
  • 4.7.3 Energy Analysis of an Absorption Refrigeration System
  • 4.7.4 Three-fluid (Gas Diffusion) Absorption Refrigeration Systems
  • 4.7.5 Water-lithium Bromide (H2O-LiBr) Absorption Refrigeration Systems
  • 4.7.5.1 Single-effect Absorption Refrigeration Systems
  • 4.7.5.2 Double-effect Absorption Refrigeration Systems
  • 4.7.5.3 Crystallization
  • 4.7.6 Steam Ejector Recompression Absorption Refrigeration Systems
  • 4.7.7 Electrochemical Absorption Refrigeration Systems
  • 4.7.8 Absorption-augmented Refrigeration System
  • 4.7.9 Exergy Analysis of an Absorption Refrigeration System
  • 4.7.10 Performance Evaluation of an Absorption Refrigeration System
  • 4.8 Concluding Remarks
  • Nomenclature
  • Study Problems
  • References
  • Chapter 5 Advanced Refrigeration Cycles and Systems
  • 5.1 Introduction
  • 5.2 Multistage Refrigeration Cycles
  • 5.3 Cascade Refrigeration Systems
  • 5.3.1 Two-stage Cascade Systems
  • 5.3.2 Three-stage (Ternary) Cascade Refrigeration System
  • 5.4 Multi-effect Absorption Refrigeration Systems
  • 5.5 Steam-jet Refrigeration Systems
  • 5.6 Adsorption Refrigeration
  • 5.7 Stirling Cycle Refrigeration
  • 5.7.1 Performance Assessment
  • 5.8 Thermoelectric Refrigeration
  • 5.8.1 Performance Assessment of Thermoelectric Coolers
  • 5.9 Thermoacoustic Refrigeration
  • 5.10 Metal Hydride Refrigeration
  • 5.10.1 Operational Principles
  • 5.10.2 Regeneration Process
  • 5.10.3 Refrigeration Process
  • 5.11 Magnetic Refrigeration
  • 5.11.1 Magnetic Refrigeration Cycle
  • 5.11.2 Active Magnetic Regenerators
  • 5.12 Supermarket Refrigeration Practices
  • 5.12.1 Direct Expansion Systems
  • 5.12.2 Distributed Systems
  • 5.12.3 Secondary Loop Systems
  • 5.13 Concluding Remarks
  • Nomenclature
  • Study Problems
  • References
  • Chapter 6 Renewable Energy-based Integrated Refrigeration Systems
  • 6.1 Introduction
  • 6.2 Solar-powered Absorption Refrigeration Systems
  • 6.3 Solar-powered Vapor-compression Refrigeration Systems
  • 6.4 Wind-powered Vapor-compression Refrigeration Systems
  • 6.5 Hydropowered Vapor-compression Refrigeration Systems
  • 6.6 Geothermal-powered Vapor-compression Refrigeration Systems
  • 6.7 Ocean Thermal Energy Conversion Powered Vapor-compression Refrigeration Systems
  • 6.8 Biomass-powered Absorption Refrigeration Systems
  • 6.9 Concluding Remarks
  • Nomenclature
  • Study Problems
  • Reference
  • Chapter 7 Heat Pipes
  • 7.1 Introduction
  • 7.2 Heat Pipes
  • 7.2.1 Heat Pipe Use
  • 7.3 Heat Pipe Applications
  • 7.3.1 Heat Pipe Coolers
  • 7.3.2 Insulated Water Coolers
  • 7.3.3 Heat Exchanger Coolers
  • 7.4 Heat Pipes for Electronics Cooling
  • 7.5 Types of Heat Pipes
  • 7.5.1 Micro Heat Pipes
  • 7.5.2 Cryogenic Heat Pipes
  • 7.6 Heat Pipe Components
  • 7.6.1 Container
  • 7.6.2 Working Fluid
  • 7.6.3 Selection of Working Fluid
  • 7.6.4 Wick or Capillary Structure
  • 7.7 Operational Principles of Heat Pipes
  • 7.7.1 Heat Pipe Operating Predictions
  • 7.7.1.1 Gravity-aided Orientation
  • 7.7.1.2 Horizontal Orientation
  • 7.7.1.3 Against Gravity Orientation
  • 7.7.2 Heat Pipe Arrangement
  • 7.8 Heat Pipe Performance
  • 7.8.1 Effective Heat Pipe Thermal Resistance
  • 7.9 Design and Manufacture of Heat Pipes
  • 7.9.1 Thermal Conductivity of a Heat Pipe
  • 7.9.2 Common Heat Pipe Diameters and Lengths
  • 7.10 Heat-transfer Limitations
  • 7.11 Heat Pipes in Heating, Ventilating and Air Conditioning
  • 7.11.1 Dehumidifier Heat Pipes
  • 7.11.1.1 Working Principle
  • 7.11.1.2 Indoor Dehumidifier Heat Pipes
  • 7.11.2 Energy Recovery Heat Pipes
  • 7.12 Concluding Remarks
  • Nomenclature
  • Study Problems
  • References
  • Chapter 8 Food Refrigeration
  • 8.1 Introduction
  • 8.2 Food Deterioration
  • 8.3 Food Preservation
  • 8.4 Food Quality
  • 8.5 Food Precooling and Cooling
  • 8.6 Food Precooling Systems
  • 8.6.1 Energy Coefficient
  • 8.6.2 Hydrocooling
  • 8.6.2.1 Hydrocooling using Ice or Ice-slush Cooling
  • 8.6.2.2 Hydrocooling using Artificial Ice
  • 8.6.2.3 Hydrocooling using Natural Ice
  • 8.6.2.4 Hydrocooling using Natural Snow
  • 8.6.2.5 Hydrocooling using Compacted Snow
  • 8.6.3 Forced-air Cooling
  • 8.6.3.1 Methods of Forced-air Cooling
  • 8.6.3.2 Cold-wall-type Tunnel Forced-air Cooling
  • 8.6.3.3 Serpentine Cooling
  • 8.6.3.4 Single-pallet Forced-air Cooling
  • 8.6.3.5 Room Cooling (with Storage and Shipping)
  • 8.6.3.6 Ice-bank Forced-air Cooling System
  • 8.6.3.7 Forced-air Cooling with Winter Coldness
  • 8.6.3.8 Technical Details of Forced-air Cooling Systems
  • 8.6.3.9 Engineering/economic Model for Forced-air Cooling Systems
  • 8.6.4 Hydraircooling
  • 8.6.5 Vacuum Cooling
  • 8.6.6 Hydrovac Cooling
  • 8.6.7 Evaporative Cooling
  • 8.6.8 Ice Cooling
  • 8.7 Precooling of Milk
  • 8.8 Food Freezing
  • 8.9 Cool and Cold Storage
  • 8.9.1 Chilling Injury
  • 8.9.2 Optimum Storage Conditions
  • 8.9.2.1 Optimum Temperature
  • 8.9.2.2 Optimum Relative Humidity
  • 8.9.3 Technical Aspects of Cold Stores
  • 8.9.3.1 Shape and Size
  • 8.9.3.2 Construction Methods
  • 8.9.3.3 Insulation
  • 8.9.3.4 Vapor Barriers
  • 8.9.3.5 Floors
  • 8.9.3.6 Cold-air Distribution
  • 8.9.3.7 Defrosting
  • 8.9.3.8 Cold Store Planning
  • 8.9.3.9 Refrigeration
  • 8.9.4 Calculation of Cold Store Refrigeration Loads
  • 8.9.5 Energy-efficient Cold Store
  • 8.9.6 Photovoltaic-powered Cold Store
  • 8.10 Controlled Atmosphere Storage
  • 8.10.1 Controlled Atmosphere Storage Ripening and Waxing
  • 8.10.2 Container-controlled Atmospheres
  • 8.10.2.1 Controlled Modified Atmosphere Systems
  • 8.10.2.2 Modified Atmospheres in Containers
  • 8.10.2.3 Modified Atmospheres in Packaging
  • 8.10.2.4 Pressure Swing Absorption Systems
  • 8.10.2.5 Membrane Separation Systems
  • 8.10.3 Packaging
  • 8.10.4 Definitions
  • 8.10.5 Modified Atmosphere Packaging
  • 8.10.6 Modified Atmosphere Cooling
  • 8.11 Refrigerated Transport
  • 8.11.1 Reefer Technology
  • 8.11.1.1 Controlled-atmosphere Reefer Containers
  • 8.11.2 Quality Aspects of Products
  • 8.11.3 Effective Packaging for Quality
  • 8.11.4 Transport Storage
  • 8.11.5 Temperature Control
  • 8.11.5.1 Temperature Control and Monitoring
  • 8.11.5.2 Temperature Monitoring Systems
  • 8.11.6 Transportation Aspects
  • 8.11.7 Recommended Transit and Storage Procedures
  • 8.11.8 Developments in Refrigerated Transport
  • 8.11.8.1 Sea and Land Transport
  • 8.11.8.2 Air Transport
  • 8.12 Respiration (Heat Generation)
  • 8.12.1 Measurement of Respiratory Heat Generation
  • 8.13 Transpiration (Moisture Loss)
  • 8.13.1 Shrinkage
  • 8.14 Cooling Process Parameters
  • 8.14.1 Cooling Coefficient
  • 8.14.2 Lag Factor
  • 8.14.3 Half Cooling Time
  • 8.14.4 Seven-eighths Cooling Time
  • 8.15 Analysis of Cooling Process Parameters
  • 8.15.1 Lin et al.'s Model for Irregular Shapes
  • 8.16 Fourier-Reynolds Correlations
  • 8.16.1 Development of Fourier-Reynolds Correlations
  • 8.17 Cooling Heat-transfer Parameters
  • 8.17.1 Specific Heat
  • 8.17.1.1 Some Correlations for Specific Heat
  • 8.17.2 Thermal Conductivity
  • 8.17.2.1 Some Correlations for Thermal Conductivity
  • 8.17.3 Thermal Diffusivity
  • 8.17.4 Effective Heat-transfer Coefficients
  • 8.17.4.1 Smith et al.'s Model
  • 8.17.4.2 Ansari's Model
  • 8.17.4.3 Stewart et al.'s Model
  • 8.17.4.4 Dincer and Dost's Models
  • 8.17.4.5 Some Methods for Effective Heat-transfer Coefficients
  • 8.17.5 Modeling for Thermal Diffusivity and Heat-transfer Coefficient
  • 8.17.6 Effective Nusselt-Reynolds Correlations
  • 8.17.7 The Dincer Number
  • 8.18 Conclusions
  • Nomenclature
  • Study Problems
  • References
  • Chapter 9 Food Freezing
  • 9.1 Introduction
  • 9.2 Food Freezing Aspects
  • 9.2.1 Enzymatic Reactions
  • 9.2.2 Microbiological Activities
  • 9.3 Quick Freezing
  • 9.4 Enthalpy
  • 9.5 Crystallization
  • 9.6 Moisture Migration
  • 9.7 Weight Loss
  • 9.8 Blanching
  • 9.9 Packaging
  • 9.10 Quality of Frozen Foods
  • 9.10.1 Objective Tests
  • 9.10.2 Sensory Tests
  • 9.10.3 Tests on the Kinetics of Quality Loss
  • 9.11 Food Freezing Process
  • 9.11.1 Freezing of Fruits
  • 9.11.2 Freezing of Vegetables
  • 9.12 Freezing Point
  • 9.13 Freezing Rate
  • 9.14 Freezing Times
  • 9.14.1 Plank's Model
  • 9.14.2 Mellor's Model
  • 9.14.3 Pham's Model
  • 9.14.4 Cleland and Earle's Model
  • 9.14.5 Mannapperuma et al.'s Model
  • 9.15 Freezing Equipment
  • 9.15.1 Tunnel Freezers
  • 9.15.1.1 Packaged Tunnel Freezers
  • 9.15.1.2 Modular Tunnel Freezers
  • 9.15.1.3 Multipass Tunnel Freezers
  • 9.15.1.4 Contact Belt Tunnel Freezers
  • 9.15.1.5 Drag Thru Doly Freezers
  • 9.15.2 Spiral Freezers
  • 9.15.2.1 Packaged Spiral Freezers
  • 9.15.2.2 Site-built Spiral Freezers
  • 9.15.3 Plate (Tray) Freezers
  • 9.15.3.1 Packaged Tray Freezers
  • 9.15.4 Impingement Jet Freezers
  • 9.15.5 Cryogenic Freezers
  • 9.15.5.1 Immersing Cryogenic Freezers
  • 9.15.5.2 Tunnel Cryogenic Freezers
  • 9.15.6 Control in Freezers
  • 9.16 Ice Making
  • 9.16.1 Block Ice Manufacture
  • 9.16.2 Shell Ice Manufacture
  • 9.16.3 Flake Ice Manufacture
  • 9.16.4 Tube Ice Manufacture
  • 9.16.5 Plate Ice Manufacture
  • 9.16.6 Slush, Slurry or Binary Ice Manufacture
  • 9.17 Thawing
  • 9.18 Freeze-drying
  • 9.18.1 Operation Principles
  • 9.18.2 Freeze-drying Times
  • 9.18.3 Freeze-dryers
  • 9.18.3.1 Batch-type Freeze-dryers
  • 9.18.3.2 Continuous-type Freeze-dryers
  • 9.18.3.3 Microwave and Dielectric Freeze-dryers
  • 9.18.4 Atmospheric Freeze-drying
  • 9.19 Conclusions
  • Nomenclature
  • Study Problems
  • References
  • Chapter 10 Environmental Impact and Sustainability Assessment of Refrigeration Systems
  • 10.1 Introduction
  • 10.2 Environmental Concerns
  • 10.3 Energy and Environmental Impact
  • 10.4 Dincer's Six Pillars
  • 10.5 Dincer's 3S Concept
  • 10.6 System Greenization
  • 10.7 Sustainability
  • 10.8 Energy and Sustainability
  • 10.9 Exergy and Sustainability
  • 10.10 Concluding Remarks
  • Study Problems
  • References
  • Appendix A Conversion Factors
  • Appendix B Thermophysical Properties
  • Appendix C Food Refrigeration Data
  • Index
  • EULA

Chapter 1
General Aspects of Thermodynamics


1.1 Introduction


Refrigeration has a diverse nature and covers a large number of processes ranging from cooling to air conditioning and from food refrigeration to human comfort. Refrigeration as a whole, therefore, appears complicated due to the fact that thermodynamics, fluid mechanics, and heat transfer are always encountered in every refrigeration process or application. For a good understanding of the operation of refrigeration systems and applications, an extensive knowledge of such topics is indispensable.

When an engineer or an engineering student undertakes the analysis of a refrigeration system and/or its application, he or she should deal with several basic aspects first, depending upon the type of the problem being studied, that may be of thermodynamics, fluid mechanics, or heat transfer. In conjunction with this, there is a need to introduce several definitions and concepts before moving into refrigeration systems and applications in depth. Furthermore, the units are of importance in the analysis of such systems and applications. One should make sure that the units used are consistent to reach the correct result. This means that there are several introductory factors to be taken into consideration to avoid getting lost further on. While the information in some situations is limited, it is desirable that the reader comprehend these processes. Despite assuming that the reader, if he or she is a student, has completed necessary courses in thermodynamics, fluid mechanics, and heat transfer, there is still a need for him or her to review, and for those who are practicing refrigeration engineers, the need is much stronger to understand the physical phenomena and practical aspects, along with a knowledge of the basic laws, principles, governing equations, and related boundary conditions. In addition, this introductory chapter reviews the essentials of such principles, laws, etc., discusses the relationships between the aspects and provides some key examples for better understanding.

This chapter primarily focuses on general aspects of thermodynamics, ranging from dimensions and units to psychrometric processes, and specifically discusses systems of units, thermodynamic systems, thermodynamic laws, pure substances, ideal and real gases, refrigerators and heat pumps, Carmot cycles, and psychrometrics and its processes. We also introduce performance assessment criteria through energy and exergy efficiencies and energetic and exergetic coefficients of performance (COPs) by the thermodynamic laws. The chapter presents lots of examples to show how to utilize thermodynamic tools, particularly balance equations, for design, analysis, and assessment.

1.2 Dimensions and Units


In the area of refrigeration it is critical to employ dimensions and units correctly for analysis, design, and assessment. It is commonly accepted that any physical quantity can be characterized by dimensions. Their magnitudes are measured/recognized in units. There are numerous commonly accepted dimensions, namely mass (m), length (L), time (t), and temperature (T), which are treated as primary quantities. There are also several other quantities, such as force (F), pressure (P), velocity (V), energy (E), and exergy (Ex), which are treated as the derived dimensions. We discuss several of these in the following subsections.

1.2.1 Systems of Units


Units are accepted as the currency of science. There are two systems: the International System of Units (Le Système International d'Unitès), which is always referred to as SI units, and the English System of Units (the English Engineering System). SI units are the most widely used throughout the world, although the English System is utilized as the traditional system of North America. In this book, SI units are primarily employed. Appendix A contains some common conversions. The dimensions, such as mass, length, force, density, specific volume, mass flow rate, volumetric flow rate, temperature and pressure, are briefly described below.

1.2.1.1 Mass

Mass is defined as a quantity of matter forming a body of indefinite shape and size. The fundamental unit of mass is the kilogram (kg) in SI and its unit in the English System is the pound mass (lbm). The basic unit of time for both unit systems is the second (s). The following relationships exist between the two unit systems:

In thermodynamics the unit mole (mol) is commonly used and defined as a certain amount of substance containing all the components. The related equation is defined as

1.1

where if m and M are given in grams and gram/mol, we get n in mol. If the units are kilogram and kilogram/kilomol, n is in kilomol (kmol). For example, one mol of water, having a molecular weight of 18 (compared to 12 for carbon-12), has a mass of 0.018 kg and for one kmol it becomes 18 kg.

1.2.1.2 Length

The basic unit of length is the meter (m) in SI and the foot (ft) in the English System, which additionally includes the inch (in) in the English System and the centimeter (cm) in SI. Here are some interrelations:

1.2.1.3 Force

A force is a kind of action that brings a body to rest or changes the direction of motion (e.g., a push or a pull). The fundamental unit of force is the Newton (N):

The four aspects, that is, mass, time, length and force, are interrelated by Newton's second law of motion, which states that the force acting on a body is proportional to the mass and acceleration in the direction of the force, as given below:

1.2

Equation (1.2) shows the force required to accelerate a mass of one kilogram at a rate of one meter per square second as 1 N = 1 kg m/s2.

It is important to note the value of the earth's gravitational acceleration as 9.80665 m/s2 (generally taken as 9.81 m/s2) in the SI system and 32.174 ft/s2 in the English System, which indicates that a body falling freely toward the surface of the earth is subject to the action of gravity alone. Some common conversion factors are listed in Appendix in A.

1.2.1.4 Density and Specific Volume

Specific volume is defined as the volume per unit mass of a substance, usually expressed in cubic meters per kilogram (m3/kg) in the SI system and in cubic feet per pound (ft3/lb) in the English System. The density of a substance is defined as the mass per unit volume, and is therefore the inverse of the specific volume:

1.3

Its units are kg/m3 in the SI system and lbm/ft3 in the English System. Specific volume is also defined as the volume per unit mass, and density as the mass per unit volume, that is,

1.4 1.5

Both specific volume and density are intensive properties and affected by temperature and pressure. The related interconversions are

1.2.1.5 Mass Flow Rate and Volumetric Flow Rate

Mass flow rate is defined as the mass flowing per unit time (kg/s in the SI system and lb/s in the English System). Volumetric flow rates are given in m3/s in the SI system and ft3/s in the English System. The following expressions can be written for the flow rates in terms of mass, specific volume, and density:

1.6 1.7

1.2.1.6 Temperature

Temperature is an indication of the thermal energy stored in a substance. In other words, we can identify hotness and coldness with the concept of temperature. The temperature of a substance may be expressed in either relative or absolute units. The two most common temperature scales are Celsius (°C) and Fahrenheit (°F). Normally, the Celsius scale is used with the SI unit system and the Fahrenheit scale with the English System. There are also two more scales, the Kelvin scale (K) and the Rankine scale (R), which are sometimes employed in thermodynamic applications. The relations between these scales are summarized as follows:

1.8 1.9 1.10 1.11

Furthermore, the temperature differences result in

Here, Kelvin is a unit of temperature measurement: zero Kelvin (0 K) is the absolute zero and is equal to -273.15 °C. Both K and °C are equal increments of temperature. For instance, when the temperature of a product is decreased to -273.15 °C (or 0 K), known as absolute zero, the substance contains no heat energy and supposedly all molecular movement stops. The saturation temperature is the temperature of a liquid or vapor at saturation conditions.

Temperature can be measured in many ways by many devices. In general, the following devices are in common use:

  • Liquid-in-glass thermometers. It is known that in these thermometers the volume of the fluid expands when subjected to heat, thereby raising its temperature. It is important to note that in practice all thermometers, including mercury ones, only work over a certain range of temperature. For example, mercury becomes solid at -38.8 °C and its properties change dramatically.
  • Resistance thermometers. A resistance thermometer (or detector) is made of resistance wire wound on a suitable former. The wire used has to be of known, repeatable, electrical characteristics so that the relationship between the temperature and resistance value can be predicted precisely. The measured value of the resistance of the...

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