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Cooling Systems

12a. Cooling Systems; Refrigerants; Condenser/Evaporator Compressive; Absorption; Evaporative; Chillers; Heat Sinks. Chapter 4 (Toa). Cooling Systems. HVAC 11a CNST 305 Environmental Systems 1 Dr. Berryman. Air Conditioning. Definition

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Cooling Systems

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  1. 12a Cooling Systems; Refrigerants; Condenser/Evaporator Compressive; Absorption; Evaporative; Chillers; Heat Sinks Chapter 4 (Toa) Cooling Systems HVAC 11a CNST 305 Environmental Systems 1 Dr. Berryman

  2. Air Conditioning • Definition • Process of treating air in an internal environment to establish and maintain required standard of temperature, humidity, cleanliness, and motion.

  3. Heat Transport Systems • Air • Water • Steam A/C Systems can use one…or a combination of transports

  4. Components - A/C System • Minimum Components

  5. Cooling Equipment • Common refrigeration systems Used for different applications and climates

  6. Compression Cycle • Fundamentals • Refrigerant characteristic • Boiling Point • Condensing Point • Saturation Point All three have the same numerical value

  7. Refrigerants • Refrigerant: R-123, R-22, R12 • Water: R-718 • Carbon Dioxide: R-744 • Ammonia: R-717

  8. 212°F [100°C] temperature pressure 14.7 psia [0.10MPa] Boiling Point of Water

  9. R-22 boils at -41.4°F [-40.8°C] Refrigerant R-22

  10. 121.5°F [49.7°C] temperature 41.2°F [5.1°C] 85 psia [0.59 MPa] 280 psia [1.93 MPa] pressure Boiling Point of R-22

  11. Effects of Pressure • Increase in pressure on a refrigerant • Results • Increased boiling, condensing, and saturation points • Decrease in pressure on a refrigerant • Increased boiling, condensing, and saturation points

  12. Refrigeration Cycle airflow liquid refrigerant(R-22) collects refrigerant vapor -41.4°F [-40.8°C]

  13. Refrigeration Cycle ? Closing the Cycle

  14. expansion device evaporator condenser compressor Refrigeration Cycle

  15. Evaporator A mixture of liquid and vapor refrigerant B refrigerant vapor air

  16. Compressor B C low-pressure refrigerant vapor from evaporator high-pressure refrigerant vapor to condenser

  17. Condenser C refrigerant vapor D liquid refrigerant outdoor air

  18. Expansion Device A mixture of liquid and vapor refrigerant D liquid refrigerant

  19. Basic Refrigeration System C discharge line condenser liquid line B compressor Direct expansion device (DX) A suction line D evaporator

  20. DX Packaged Unit

  21. SEER vs HSPF • SEER • Seasonal Energy Efficiency Ratio • Index of MPG for a/c • Number of BTU’s removed by 1 watt of electricity • Rating range from 8 – 14 SEER • Water cooled condensers can achieve higher (system w/ water tower) • HSPF for heat pumps • Heating Seasonal Performance Factor • BTU per watt

  22. Split System Cooling

  23. Heat Pump Reversible Refrigeration System

  24. COP • Coefficient of Performance (1-5) • Commercial Heating efficiency index • COP of 1 = 3,400 BTU/Kw • Strip heaters, toasters, water heaters, etc. • COP 2 • 3,400 BH electrical - 3,400 OA environment • TOTAL 6,800 BH • COP 3 • 3,400 BH electrical – 6,800 OA environment • TOTAL 10,200 BH • HSPF -Heating Seasonal Performance Factor • BTU per watt – Heating index for Residential • COP 2 = HSPF 6.8

  25. Air Source Heat Pump COP Heat Pump COP changes w/ source temperature

  26. Large A/C Equipment Air Handler Chiller Cooling Tower

  27. Air Handler Fan/Coil Unit

  28. Chiller - Compression • Reciprocating • Cylinder displacement • Scroll • Scroll displacement • Rotary Helical • Screw - type • Centrifugal • impellers Cut Away – Rotary Helical Chiller

  29. Water Towers • Central Plant • 500 – 30,000 GPM

  30. Chillers - Absorption condenser generator evaporator absorber

  31. Refrigerant • Distilled water • Stable • Nontoxic • Low cost • Readily available • Environmentally friendly • High latent heat of vaporization

  32. Boiling Point of Water 115°F [46.1°C] temperature 45°F [7.2°C] 1.5 psia [10.34 kPa] 0.15 psia [1.034 kPa] pressure

  33. Absorbent • Lithium Bromide (LiBr) • High affinity for water (refrigerant) • In solution, higher boiling point than water • Nontoxic

  34. Absorption Cycle Cooling Tower steam or hot water Boiler condenser High Pressure cooling water generator evaporator Air Handler chilled water Low Pressure heat exchanger absorber Cooling Tower

  35. Absorber refrigerant vapor absorber 100°F 0,15 psi intermediate solution absorber spray pump dilute solution cooling water concentrated solution From Cooling Tower To generator

  36. Generator steam or hot water refrigerant vapor generator concentrated solution dilute solution

  37. Condenser refrigerant vapor condenser 115°F 1.5 psi cooling water liquid refrigerant

  38. Evaporator refrigerant vapor 45°F 0,15 psi chilled water evaporator Air Handler liquid refrigerant absorber evaporator spray pump

  39. Expansion Device liquid refrigerant evaporator expansion device

  40. Heat Exchanger concentrated solution precools the concentrated solution heat exchanger dilute solution generator pump

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