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

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

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

Components - A/C System Minimum Components

Cooling Equipment Common refrigeration systems Used for different applications and climates

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

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

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

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

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

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

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

Refrigeration Cycle ? Closing the Cycle

Refrigeration Cycle compressor condenser expansiondevice evaporator

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

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

Condenser C D refrigerant vapor liquidrefrigerant outdoor air

Expansion Device A D liquidrefrigerant mixture of liquid and vapor refrigerant

Basic Refrigeration System compressor condenser evaporator Direct expansion device (DX) dischargeline suctionline liquidline A B C D

DX Packaged Unit

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

Split System Cooling

Heat Pump Reversible Refrigeration System

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

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

Large A/C Equipment Air HandlerChillerCooling Tower

Air Handler Fan/Coil Unit

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

Water Towers Central Plant 500 – 30,000 GPM

Chillers - Absorption condenser generator evaporator absorber

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

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

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

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

Absorber coolingwater refrigerantvapor concentratedsolution intermediatesolution absorber spray pump dilutesolution absorber 100°F 0,15 psi From Cooling Tower To generator

Generator steam or hot water dilutesolution refrigerantvapor concentratedsolution generator

Condenser coolingwater refrigerantvapor liquid refrigerant condenser 115°F 1.5 psi

Evaporator chilledwater evaporator spray pump refrigerantvapor liquid refrigerant absorber evaporator Air Handler 45°F 0,15 psi

Expansion Device liquid refrigerant expansiondevice evaporator

Heat Exchanger generator pump dilutesolution heatexchanger concentratedsolution precools the concentrated solution