Air conditioning engineering 5th

Preface to the Fifth Edition Preface to the First Edition Acknowledgement 1. The Need for Air Conditioning v vii viii 1.1 The meaning of air conditioning 1 1.2 Comfort conditioning 1 1.3 Industrial conditioning 2 2. Fundamental Properties of Air and Water Vapour Mixtures 3 2.1 The basis for rationalisation 3 2.2 The composition of dry air 3 2.3 Standards adopted 5 2.4 Boyle's law 6 2.5 Charles' law 7 2.6 The general gas law 9 2.7 Dalton's law of partial pressure 11 2.8 Saturation vapour pressure 12 2.9 The vapour pressure of steam in moist air 13 2.10 Moisture content and humidity ratio 16 2.11 Percentage saturation 18 2.12 Relative humidity 19 2.13 Dew point 20 2.14 Specific volume 21 2.15 Enthalpy: thermodynamic background 22 2.16 Enthalpy in practice 23 2.17 Wet-bulb temperature 25 2.18 Temperature of adiabatic saturation 28 2.19 Non-ideal behaviour 30 2.20 The triple point 33 3. The Psychrometry of Air Conditioning Processes 38 3.1 The psychrometric chart 38 3.2 Mixtures 39 3.3 Sensible heating and cooling 42 3.4 Dehumidification 44 3.5 Humidification 48 3.6 Water injection 52 3.7 Steam injection 54 x Contents 111 3.8 3.9 3.10 3.11 3.12 3.13 Cooling and dehumidification with reheat Pre-heat and humidification with reheat Mixing and adiabatic saturation with reheat The use of dry steam for humidification Supersaturation Dehumidification by sorption methods Comfort and Inside Design Conditions 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10 4.11 4.12 4.13 Metabolism and comfort Bodily mechanisms of heat transfer and thermostatic control Metabolic rates Clothing Environmental influences on comfort Other influences on comfort Fanger's comfort equation Synthetic comfort scales Measuring instruments Outdoor air requirements Indoor air quality The choice of inside design conditions Design temperatures and heat gains 5. Climate and Outside Design Conditions 11 5.1 Climate 5.2 Winds 5.3 Local winds 5.4 The formation of dew 5.5 Mist and fog 5.6 Rain 5.7 Diurnal temperature variation 5.8 Diurnal variation of humidity 5.9 Meteorological measurement 5.10 The seasonal change of outside psychrometric state 5.11 The choice of outside design conditions The Choice of Supply Design Conditions 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 Sensible heat removal The specific heat capacity of humid air Latent heat removal The slope of the room ratio line Heat gain arising from fan power Wasteful reheat The choice of a suitable supply state Warm air supply temperatures 57 62 66 68 70 71 80 80 81 82 83 85 88 89 90 92 93 94 96 97 104 104 105 106 107 107 109 109 110 112 115 115 120 120 123 124 126 132 133 136 141 7. Heat Gains from Solar and Other Sources 144 7.1 7.2 The composition of heat gains The physics of solar radiation 144 144 Contents xi 7.3 7.4 7.5 7.6 7.7 7.8 7.9 7.10 7.11 7.12 7.13 7.14 7.15 7.16 7.17 7.18 7.19 7.20 7.21 7.22 7.23 7.24 7.25 7.26 Sky radiation Definitions The declination of the sun The altitude of the sun The azimuth of the sun The intensity of direct radiation on a surface The numerical value of direct radiation External shading The geometry of shadows The transmission of solar radiation through glass The heat absorbed by glass Internal shading and double glazing Numerical values of scattered radiation Minor factors affecting solar gains Heat gain through walls Sol-air temperature Calculation of heat gain through a wall or roof Air conditioning load due to solar gain through glass Heat transfer to ducts Infiltration Electric lighting Occupants Power dissipation from motors Business machines 145 146 149 150 152 153 156 159 159 161 163 168 169 170 175 177 178 184 190 197 198 200 201 201 8. Cooling Load 216 8.1 8.2 8.3 8.4 8.5 8.6 8.7 8.8 8.9 8.10 8.11 8.12 Cooling load and heat gains Cooling load for a whole building Partial load Cooling load offset by reheat The use of by-passed air instead of reheat Face and by-pass dampers Cooling in sequence with heating Hot deck--cold deck systems Double duct cooling load The load on air-water systems Diversification of load Load diagrams 216 219 220 220 225 227 229 230 231 231 231 232 I The Fundamentals of Vapour Compression Refrigeration 241 9.1 9.2 9.3 9.4 9.5 9.6 9.7 9.8 9.9 The basis of vapour compression refrigeration Thermodynamics and refrigeration The refrigerating effect The work done in compression Heat rejected at the condenser Coefficient of performance Actual vapour-compression cycle Pressure-volume relations Volumetric efficiency 241 243 249 253 254 255 258 261 266 xii Contents 9.10 Thermosyphon cooling 9.11 Refrigerants 9.12 Ozone depletion effects 9.13 Global warming 9.14 Other methods of refrigeration 9.15 Safety 269 270 272 274 274 276 10. Air Cooler Coils 279 10.1 10.2 10.3 10.4 10.5 10.6 10.7 10.8 10.9 10.10 10.11 10.12 Distinction between cooler coils and air washers Cooler coil construction Parallel and contra-flow Contact factor Heat and mass transfer to cooler coils Sensible cooling Partial load operation The performance of a wild coil Sprayed cooler coils Free cooling Direct-expansion coils Air washers 279 280 284 286 289 294 298 300 301 303 304 304 11. The Rejection of Heat from Condensers and Cooling Towers 311 11.1 11.2 11.3 11.4 11.5 11.6 11.7 Methods of rejecting heat Types of cooling tower Theoretical considerations Evaporative condensers Air-cooled condensers Automatic control Practical considerations 311 313 315 317 318 319 321 12. Refrigeration Plant 326 12.1 12.2 12.3 12.4 12.5 12.6 12.7 12.8 12.9 The expansion valve The distributor Float valves Evaporators for liquid chilling Direct-expansion air cooler coils The reciprocating compressor The air-cooled condensing set Condensing set-evaporator match The control of direct-expansion cooler coils and condensing sets 12.10 The performance of water chillers 12.11 The screw compressor 12.12 The scroll compressor 12.13 Centrifugal compressors 12.14 The water-cooled condenser 12.15 Piping and accessories 12.16 Charging the system 326 330 331 331 333 336 339 340 341 343 349 352 352 358 359 361 Contents xiii 13. Automatic Controls 363 13.1 The principle of automatic control 13.2 Definitions 13.3 Measurement and lag 13.4 Measurement elements 13.5 Types of system 13.6 Methods of control 13.7 Simple two-position control 13.8 Timed two-position control 13.9 Floating action 13.10 Simple proportional control 13.11 Refined proportional control 13.12 Automatic valves 13.13 Automatic dampers 13.14 Application 13.15 Fluidics 13.16 Control by microprocessors and Building Management Systems (BMS and BEMS) 363 364 366 367 371 375 375 375 376 378 379 381 390 391 395 395 14. Vapour Absorption Refrigeration 399 14.1 14.2 14.3 14.4 14.5 Basic concepts Temperatures, pressures, heat quantities and flow rates for the lithium bromide-water cycle Coefficient of performance and cycle efficiency Practical considerations Other systems 399 400 404 406 409 15. Airflow in Ducts and Fan Performance 411 15.1 15.2 15.3 15.4 15.5 15.6 15.7 15.8 15.9 15.10 15.11 Viscous and turbulent flow Basic sizing Conversion from circular to rectangular section Energy changes in a duct system Velocity (dynamic) pressure The flow of air into a suction opening The coefficient of entry (CE) The discharge of air from a duct system Airflow through a simple duct system Airflow through transition pieces Airflow around bends 15.12 Airflow through supply branches 15.13 Flow through suction branches 15.14 Calculation of fan total and fan static pressure 15.15 The interaction of fan and system characteristic curves 15.16 The fan laws 15.17 Maximum fan speed 15.18 Margins 15.19 Power-volume and efficiency-volume characteristics 15.20 Fan testing 15.21 The performance of air handling units 411 415 418 420 422 423 423 425 426 427 433 436 437 438 443 445 447 447 448 452 453 xiv Contents 15.22 Methods of varying fan capacity in a duct system 15.23 The effect of opening and closing branch dampers 15.24 Fans in parallel and series 455 459 462 16. Ventilation and a Decay Equation 468 16.1 16.2 16.3 The need for ventilation The decay equation An application of the decay equation to changes of enthalpy 468 475 482 17. Filtration 488 17.1 Particle sizes 17.2 Particle behaviour and collection 17.3 Efficiency 17.4 Classification according to efficiency 17.5 Viscous filters 17.6 Dry filters 17.7 Electric filters 17.8 Wet filters 17.9 Centrifugal collectors 17.10 Adsorption filters 17.11 Safety 488 489 490 495 496 496 498 501 501 501 503 Index 507