Cooling Systems

1
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 oneor 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
Boiling Point of Water
9
Refrigerant R-22
10
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
-41.4F -40.8C
13
Refrigeration Cycle
?
Closing the Cycle
14
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 BTUs 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
115F 46.1C
temperature
45F 7.2C
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
100F 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
115F 1.5 psi
cooling water
liquid refrigerant
38
Evaporator
refrigerant vapor
45F 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