Cooling SystemsHVAC 11a

CNST 305 Environmental Systems 1Dr. Berryman

12a Cooling 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 Waterte

mpe

ratu

rete

mpe

ratu

re

pressurepressure

212°F212°F[100°C][100°C]

14.7 psia14.7 psia[0.10MPa][0.10MPa]

Refrigerant R-22

-41.4°F-41.4°F[-40.8°C][-40.8°C]

R-22 boils atR-22 boils at

Boiling Point of R-22

41.2°F41.2°F[5.1°C][5.1°C]

85 psia85 psia[0.59 MPa][0.59 MPa]

121.5°F121.5°F[49.7°C][49.7°C]

280 psia280 psia[1.93 MPa][1.93 MPa]

tem

pera

ture

tem

pera

ture

pressurepressure

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 refrigerantliquid refrigerant(R-22)(R-22)

-41.4°F-41.4°F[-40.8°C][-40.8°C]

airflowairflow

collects collects refrigerantrefrigerant

vaporvapor

Refrigeration Cycle

??

Closing the Cycle

Refrigeration Cycle

compressorcompressor

condensercondenser

expansionexpansion

devicedeviceevaporatorevaporator

Evaporator

refrigerant refrigerant vaporvapor

mixture ofmixture of

liquid and vapor liquid and vapor refrigerantrefrigerant B

A

airair

Compressor

low-pressurelow-pressurerefrigerant vaporrefrigerant vaporfrom evaporatorfrom evaporator

CB

high-pressurehigh-pressurerefrigerant vaporrefrigerant vaporto condenserto condenser

Condenser

C

D

refrigerant refrigerant vaporvapor

liquidliquid

refrigerant refrigerant outdoor airoutdoor air

Expansion Device

A

Dliquidliquid

refrigerant refrigerant

mixture ofmixture of

liquid and vapor liquid and vapor refrigerantrefrigerant

Basic Refrigeration System

compressorcompressor

condensercondenser

evaporatorevaporator

Direct expansion Direct expansion device (DX)device (DX)

dischargedischarge

lineline

suctionsuction

lineline

liquidliquid

lineline

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 Handler Chiller Cooling 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

condensercondenser generatorgenerator

evaporatorevaporator

absorberabsorber

Refrigerant Distilled water

Stable Nontoxic Low cost Readily available Environmentally

friendly High latent heat of

vaporization

Boiling Point of Water

1.5 psia1.5 psia[10.34 kPa][10.34 kPa]

0.15 psia0.15 psia[1.034 kPa][1.034 kPa]

tem

pera

ture

tem

pera

ture

pressurepressure

45°F45°F[7.2°C][7.2°C]

115°F115°F[46.1°C][46.1°C]

Absorbent Lithium Bromide

(LiBr) High affinity for

water (refrigerant)

In solution, higher boiling point than water

Nontoxic

Absorption Cycle

condensercondenser

evaporatorevaporator

absorberabsorber

generatorgenerator

chilledwater

coolingwater

steam orhot water

heatheatexchangerexchanger

Air Handler

Cooling Tower

BoilerHigh Pressure

Low Pressure

Cooling Tower

Absorber

coolingcoolingwaterwater

refrigerantrefrigerantvaporvapor

concentratedconcentratedsolutionsolution

intermediateintermediatesolutionsolution absorberabsorber

spray pumpspray pumpdilutedilutesolutionsolution

absorberabsorber100°F 0,15 psi100°F 0,15 psi

From Cooling TowerTo To generatorgenerator

Generatorsteam orsteam orhot waterhot water

dilutedilutesolutionsolution

refrigerantrefrigerantvaporvapor

concentratedconcentratedsolutionsolution

generatorgenerator

Condenser

coolingcoolingwaterwater

refrigerantrefrigerantvaporvapor

liquid liquid refrigerantrefrigerant

condensercondenser115°F 1.5 psi115°F 1.5 psi

Evaporator

chilledchilledwaterwater

evaporatorevaporatorspray pumpspray pump

refrigerantrefrigerantvaporvapor

liquid liquid refrigerantrefrigerantabsorberabsorber

evaporatorevaporatorAir

Handler

45°F 0,15 psi45°F 0,15 psi

Expansion Deviceliquid liquid refrigerantrefrigerant

expansionexpansiondevicedevice

evaporatorevaporator

Heat Exchanger

generator pumpgenerator pump

dilutedilutesolutionsolution

heatheatexchangerexchanger

concentratedconcentratedsolutionsolution

precools the concentrated solution