Chapter 1 Introduction .............................................. 1 1.1 Heat Pumping .................................................... 1 1.2 Overview of Current Products .................................... 4 1.2.1 Residential Air Conditioners and Heat Pumps ............... 4 1.2.2 Commercial Air-Conditioning Systems ....................... 5 1.2.3 Industrial Systems ........................................ 5 1.2.4 Refrigeration Systems ..................................... 5 1.3 History of Working Fluids ....................................... 6 1.4 Requirements for Working Fluids ................................. 9 1.5 Background of Environmental Concerns ........................... 10 1.5.1 Impact of Ozone Depletion ................................ 10 1.5.2 Impact of Global Warming ................................. 10 1.5.3 International Efforts on Environmental Protection ........ 11 1.5.4 Impact of Environmental Issues on U.S. Climate Control Industry ................................................. 11 1.5.5 Mixtures as R22 Replacements ............................. 11 References ......................................................... 12 Chapter 2 Properties of Working Fluids ............................. 17 2.1 Thermodynamic Diagrams of Pure and Mixed Refrigerants .......... 17 2.1.1 Temperature-Mass Fraction Diagram ....................... 18 2.1.2 Pressure-Temperature Diagram ............................ 24 2.1.3 Pressure-Enthalpy Diagram ............................... 27 2.1.4 Temperature-Entropy Diagram ............................. 42 2.1.5 Temperature-Enthalpy Diagram ............................ 43 2.1.6 Pressure-Mass Fraction Diagram .......................... 44 2.2 Analytical Treatment of Thermodynamic Properties ............... 47 2.2.1 Types of Substances in Internal Equilibrium ............. 47 2.2.2 Definitions of Concentration ............................ 48 2.2.3 Solubility .............................................. 48 2.2.4 Liquid Mixing Phenomena ................................. 49 2.2.5 Adiabatic Mixing of Binary Mixtures ..................... 53 2.2.6 Isothermal Mixing of Binary Mixtures .................... 55 2.2.7 Mixing of Binary Mixtures with Heat Exchange ............ 56 2.2.8 Specific Heat of Binary Mixtures ........................ 56 2.2.9 Latent Heat of Binary Mixtures .......................... 57 2.2.10 Critical Point of Binary Mixtures ....................... 58 2.3 Ternary and Multicomponent Mixtures ............................ 59 2.3.1 Thermodynamic Diagrams for Multicomponent Mixtures ...... 60 2.3.2 Flammability of Mixtures ................................ 61 2.3.3 Reasoning for Selecting Certain Mixtures ................ 61 References ......................................................... 63 Chapter 3 Vapor Compression Cycle Fundamentals ..................... 65 3.1 The Carnot Cycle .............................................. 65 3.2 Heat Pumps in the Context of Energy Conversion ................ 67 3.3 The Ideal Vapor Compression Cycle ............................. 69 3.3.1 Power and Capacity Calculations ......................... 72 3.4 Differences between the Carnot Cycle and Vapor Compression Cycle ......................................................... 73 3.5 Realistic Vapor Compression Cycles ............................ 77 3.6 Lorenz Cycle .................................................. 79 3.7 Vapor Compression Cycle with Zeotropic Mixtures in Thermodynamic Diagrams ........................................ 82 3.7.1 Pressure-Temperature Diagram ............................ 82 3.7.2 Pressure-Enthalpy Diagram ............................... 83 3.7.3 Temperature-Entropy Diagram ............................. 85 3.7.4 Temperature-Mass Fraction Diagram ....................... 86 3.8 The Matching of Temperature Glides ............................ 87 3.9 Methods for Comparing the Performance of Pure and Mixed Refrigerants .................................................. 90 3.10 Simulation of the Vapor Compression Cycle ..................... 93 3.10.1 Refrigeration Component Models ......................... 93 3.10.1.1 Heat Exchanger Model .......................... 93 3.10.1.2 Compressor Model ............................. 104 3.10.1.3 Expansion Device Model ....................... 106 3.10.1.4 Refrigerant Mixture Properties ............... 109 3.10.2 Cycle Models .......................................... 110 3.10.2.1 NIST Model: Cycle 7 and Cycle 11 ............. 110 3.10.2.2 Binary Mixture Performance Analysis .......... 112 3.10.2.3 Refrigerant Performance Comparison ........... 115 3.10.2.4 ORNL Model: BICYCLE and Mark V ............... 120 3.10.2.5 University of Maryland Model: HAC1 and HPCYCLE ...................................... 124 References ........................................................ 129 Chapter 4 Methods for Improving the Cycle Efficiency .............. 135 4.1 Measures of Incremental Efficiency Improvement ................ 135 4.2 The Suction Line to Liquid Line Heat Exchanger ................ 138 4.3 The Economizer ................................................ 142 4.4 The Expander .................................................. 145 4.5 The Three-Path Evaporator ..................................... 146 References ........................................................ 147 Chapter 5 Experimental Performance Measurements ................... 149 5.1 Laboratory Breadboard Tests ................................... 149 5.1.1 NIST Breadboard Heat Pump I ............................. 150 5.1.1.1 Test Facility ................................... 150 5.1.1.2 Capacity Measurements ........................... 150 5.1.1.3 Test Procedure .................................. 153 5.1.1.4 Heat Exchanger Variations ....................... 154 5.1.1.5 Linearity of the Enthalpy vs. Temperature Relationship .................................... 157 5.1.1.6 Liquid Precooling in Evaporator ................. 160 5.1.1.7 Discussion ...................................... 161 5.1.1.8 Conclusion ...................................... 162 5.1.2 NIST Breadboard Heat Pump II ............................ 163 5.1.2.1 Test Facility ................................... 163 5.1.2.2 Test Results of Test Apparatus II ............... 163 5.1.2.3 Conclusion ...................................... 170 5.1.3 ORNL Breadboard Heat Pump ............................... 170 5.1.3.1 Test Facility ................................... 170 5.1.3.2 R13B1/R152a Test ................................ 171 5.1.3.3 R143a/R124 Test ................................. 171 5.1.3.4 R143a/R124 and R32/R124 Test .................... 174 5.2 Actual System Tests Experience ................................ 177 5.2.1 Heat Pump Test at CEEE .................................. 177 5.2.1.1 Test Facility ................................... 177 5.2.1.2 Test Unit ....................................... 181 5.2.1.3 Refrigerants Investigated ....................... 182 5.2.1.4 Test Procedure .................................. 184 5.2.1.5 Test Results .................................... 185 5.2.1.6 Effects of Heat Exchanger Geometry on Mixture Performance ..................................... 190 5.2.2 Heat Pump Test at NIST .................................. 191 5.2.2.1 R13B1/R152a Test ................................ 195 5.2.2.2 R32/R134a Test .................................. 198 References ........................................................ 206 Chapter 6 Refrigerant Mixtures in Refrigeration Applications ...... 209 6.1 Single Evaporator Refrigeration Cycle ......................... 209 6.2 Dual Evaporator Refrigeration Cycle ........................... 212 6.3 Lorenz-Meutzner Cycle ......................................... 213 6.4 Modified Lorenz-Meutzner Cycle Refrigerator ................... 215 References ........................................................ 218 Chapter 7 Refrigerant Mixtures in Heat Pump Applications .......... 221 7.1 Capacity Control .............................................. 221 7.1.1 One Accumulator Cycle ................................... 222 7.1.2 Two Accumulators Cycle .................................. 223 7.1.3 Modified Two Accumulators Cycle ......................... 226 7.1.4 Three Accumulators Cycle ................................ 227 7.1.5 Cycle with Rectifier .................................... 227 7.1.6 Modified Cycle with Rectifier ........................... 228 7.1.7 Cycle with Rectifier-Accumulator ........................ 229 7.2 R22 Replacement ............................................... 230 7.2.1 Screen of Refrigerant Mixtures .......................... 230 7.2.2 Screen of HFC Refrigerant Mixtures ...................... 232 References ........................................................ 235 Chapter 8 Heat Transfer of Refrigerant Mixtures ................... 237 8.1 Nucleate Pool Boiling Heat Transfer Coefficients .............. 237 8.2 Flow Boiling Heat Transfer Coefficients ....................... 239 8.3 Correlations for Flow Boiling Heat Transfer ................... 245 8.3.1 Superposition Models .................................... 246 8.3.1.1 Chen Correlation ................................ 246 8.3.1.2 Bennett and Chen Correlation .................... 247 8.3.1.3 Gungor and Winterton Correlation ................ 248 8.3.1.4 Jung Correlation ................................ 248 8.3.2 Enhancement Models ...................................... 249 8.3.2.1 Shah Correlation ................................ 249 8.3.2.2 Schrock and Grossman Correlation ................ 250 8.3.2.3 Mishra Correlation .............................. 250 8.3.2.4 Sami Correlation ................................ 251 8.3.2.5 Shin Correlation ................................ 251 8.3.3 Asymptotic Models ....................................... 252 8.3.3.1 Liu and Winterton Correlation ................... 252 8.3.3.2 Wattelet Correlation ............................ 252 8.3.3.3 Bivens and Yokozeki Correlation ................. 253 8.3.4 Comparison of Correlations .............................. 254 8.4 Pressure Drop During Evaporation .............................. 254 8.4.1 Martinelli and Nelson Correlation ....................... 254 8.4.2 Singal Correlation ...................................... 257 8.4.3 Sami Correlation ........................................ 258 8.4.4 Jung and Radermacher Correlation ........................ 258 8.4.5 Souza and Pimenta Correlation ........................... 259 8.4.6 Other Studies ........................................... 259 8.5 Condensation Heat Transfer Coefficients ....................... 259 8.6 Correlations for Flow Condensation Heat Transfer .............. 264 8.6.1 Akers Correlation ....................................... 264 8.6.2 Traviss Correlation ..................................... 265 8.6.3 Shah Correlation ........................................ 265 8.6.4 Dobson Correlation ...................................... 266 8.6.5 Tandon Correlation ...................................... 266 8.6.6 Koyama Correlation ...................................... 267 8.6.7 Sami Correlation ........................................ 267 8.6.8 Sweeney Correlation ..................................... 267 8.6.9 Comparison of Correlations .............................. 268 8.7 Pressure Drop during Condensation ............................. 268 8.7.1 Koyama Correlation ...................................... 270 8.7.2 Sami Correlation ........................................ 272 8.7.3 Other Studies ........................................... 272 References ........................................................ 273 Chapter 9 Operational Issues ...................................... 279 9.1 Regulation .................................................... 279 9.1.1 Clean Air Act Amendments of 1990 ........................ 279 9.1.2 EPA Regulations ......................................... 279 9.2 Refrigerant Recovery .......................................... 280 9.3 Cycle Flushing ................................................ 281 9.4 Refrigerant Mixing ............................................ 282 9.5 Refrigerant Mass Fraction Measurement ......................... 283 9.6 Evacuating a System ........................................... 284 9.7 Refrigerant Charge ............................................ 285 9.8 Leak Checking ................................................. 287 9.9 Mass Fraction Shifts .......................................... 287 9.9.1 Mass Fraction Shift in the Cycle ........................ 289 9.9.2 Mass Fraction Shift Due to Leakage ...................... 294 9.9.3 Mass Fraction Shift during Container Transfers .......... 297 References ........................................................ 297 Index ............................................................. 299