introduction to hvac -...
TRANSCRIPT
Introduction to HVAC
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
Agenda
▲ Psychrometrics ▲ Human Comfort ▲ Heat Transfer ▲ Refrigeration Cycle ▲ HVAC Terminology ▲ HVAC Systems
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
Psychrometrics
© American Standard Inc. 2000 Air Conditioning Clinic TRG-TRC002-EN
Introduction to HVAC
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
Properties of Air
▲ Dry-bulb temperature ▲ Wet-bulb temperature ▲ Dew-point temperature ▲ Relative humidity ▲ Enthalpy
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
Psychrometric Chart
Air Conditioning Clinic TRC001GB.PPT © American Standard Inc. 2003
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
Dry-Bulb Thermometer
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Wet-Bulb Thermometer
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Relative Humidity
Relative Humidity
Amount of moisture that a given amount of air is holding
= Amount of moisture that a given
amount of air can hold
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
Enthalpy (h):
▲ Definition: A measure of the total heat energy of an air mass in BTU per pound of dry air and associated moisture.
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
Human Comfort
© American Standard Inc. 2000 Air Conditioning Clinic TRG-TRC002-EN
Introduction to HVAC
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
Impact of Comfort
Why is air conditioning a “big deal”?
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
“Home” Economics Operating Costs
lights
laundry kitchen
misc
HVAC
HVAC electrical
plumbing site work
all other
Construction Costs
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
A comfortable indoor environment enhances:
Effects of Comfort
▲ Tenancy ▲ Productivity ▲ Health ▲ Profitability
Ahhh!
I’m quite cozy.
I’m fine.
It’s nice in here!
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
Factors Affecting Human Comfort
▲ Dry-bulb temperature ▲ Humidity ▲ Air movement ▲ Fresh air ▲ Clean air ▲ Noise level ▲ Adequate lighting ▲ Proper furniture and
work surfaces
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
Cooling Load Components roof
lights
equipment
floor
exterior wall
glass solar glass
conduction
infiltration people
partition wall
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
Heat Transfer
© American Standard Inc. 2000 Air Conditioning Clinic TRG-TRC002-EN
Introduction to HVAC
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
What is Refrigeration?
Refrigeration is the process of removing heat from one substance and transferring it to another substance.
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
Principles of Heat Transfer
▲ Heat energy cannot be destroyed
▲ Heat always flows from a higher temperature substance to a lower temperature substance
▲ Heat can be transferred from one substance to another
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
Methods of Heat Transfer
hot water conduction cool air
warm air
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
Measuring Heat Quantity
60°F 61°F 1 Btu
1 lb water
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
Refrigeration Cycle
© American Standard Inc. 2000 Air Conditioning Clinic TRG-TRC002-EN
Introduction to HVAC
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
Basic Refrigeration System
compressor
condenser
evaporator
expansion device
discharge line
suction line
liquid line
A
B
C
D
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
HVAC Terminology
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
HVAC Terminology
Topics of Discussion:
▲ CFM, ESP, TSP ▲ Enthalpy ▲ Sensible, Latent, Total Heat ▲ BTU, BTUH, MBH, Ton ▲ dB, dBA
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
HVAC Terminology
CFM:
▲ Definition: Cubic Feet per Minute
▲ Typical values: ➣ 1 cfm/square foot airflow ➣ 400 cfm/ton ➣ 20-cfm per person ventilation air
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
HVAC Terminology
ESP (External Static Pressure):
▲ Definition: External Static Pressure is the sum of the losses (both straight run frictional & dynamic fitting) that occur outside of the air handling system.
▲ Static Pressure in our industry has a unit of measure equivalent to inches water gauge. Typical values would be in the 1” to 3” range for ESP.
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
HVAC Terminology
TSP (Total Static Pressure):
▲ Definition: Total Static Pressure is the sum of the ESP and the SP losses of that occur in the air handling system itself. This is the actual SP that the Fan must develop.
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
HVAC Terminology
Sensible Heat:
▲ Definition: That heat when increased or decreased to a previously steady state environment, will increase or decrease the Dry Bulb temperature of that space.
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
HVAC Terminology
Latent Heat:
▲ Definition: That heat when increased or decreased to a previously steady state environment, will not change the Dry Bulb temperature of that space. It only effects the amount of moisture in the space.
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
HVAC Terminology
Total Heat:
▲ Definition: The sum of both the Sensible & Latent heat.
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
HVAC Terminology
BTU:
▲ Definition: The amount of heat necessary to raise one pound of water one deg F
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
HVAC Terminology
Ton:
▲ Definition: The rate of heat transfer necessary to melt 1-ton of ice at 32 deg F in 24 hours
= 2,000 lbs x 144 BTU/lb / 24 hrs = 288,000 BTU / 24 hrs = 12,000 BTU/hour or BTUH
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
HVAC Terminology
dB:
▲ Definition: A measurement used to describe the amplitude of Sound.
▲ A healthy young human ear can detect sound pressures in the range of: ➣ 20 millionths of a Pascal to ➣ 20 Pascals ➣ This range is too difficult to manage, so we put it
on a logarithmic scale ➣ Which works out to: 00-dB to 140-dB
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
HVAC Terminology
dBA:
▲ Definition: The ‘A’ weighting scale is used to better estimate how the human ear hears sound pressure.
▲ Some acoustical rules of thumb: ➣ 3-dB represents doubling of sound power ➣ 6-dB represents doubling of sound pressure ➣ 10-dB represents perceived doubling of sound to
human ear ➣ Average human can’t distinguish a difference less
than 3-dB
HVAC Systems
Introduction to HVAC
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
The Five System Loops
Airside
Chilled water
Refrigeration
Heat rejection
Controls
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
Airside Loop
supply air
sensible heat
moisture (latent heat)
return air
conditioned space
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
Airside Loop 95°F (35°C)
RA
OA EA
75°F (23.9°C)
80°F (26.7°C)
SA
MA
cooling coil
55°F (12.8°C)
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
Chilled-Water Cooling Coil
drain pan
warm, humid air
cool, dry air
condensate drain line
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Supply-Air Distribution System
VAV terminal
diffuser flexible duct sheet-metal supply duct
central air handler
outdoor-air inlet
return-air inlet
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Ceiling Plenum Return
roof
plenum return air
ceiling
supply air diffuser
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
42°F (5.6°C)
57°F (13.9°C)
55°F (12.8°C)
cooling coil
80°F (26.7°C)
evaporator
Chilled-Water Loop
control valve
pump
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
compressor
120°F (48.9°C)
38°F (3.3°C)
50°F (10°C)
42°F (5.6°C)
57°F (13.9°C)
55°F (12.8°C)
80°F (26.7°C)
evaporator
condenser 110°F
(43.3°C)
Refrigeration Loop
expansion device
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
Packaged Air-Cooled Chiller compressor
evaporator air-cooled condenser
expansion device
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
cooling tower
condenser
100°F (37.8°C)
85°F (29.4°C)
120°F (48.9°C)
38°F (3.3°C)
50°F (10°C)
42°F (5.6°C)
57°F (13.9°C)
55°F (12.8°C)
80°F (26.7°C)
110°F (43.3°C)
Heat-Rejection Loop (water-cooled) control valve
pump
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
compressor
cooling coil (evaporator)
expansion device
No Chilled-Water Loop (RTU/Split System)
air-cooled condenser
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
Controls Loop
building automation system system-level controller
Common HVAC System Types
Introduction to HVAC Systems
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
Single Zone, Constant Volume
cooling coil
RA EA
OA supply
fan
thermostat
SA
zone
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Multiple Zones, Variable Volume
RA EA
OA supply
fan
zone thermostat
zone
VAV box
SA cooling
coil
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
multiple zones, variable volume DX Rooftop VAV System
packaged DX rooftop air conditioner
system-level controller
VAV terminal, diffusers
supply return
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
multiple zones, variable volume Central Chilled-Water VAV System
cooling tower
system-level controller
VAV terminal, diffusers
hot-water boiler, pumps
water-cooled chiller
air handler
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
Four-Pipe Versus Two-Pipe System
Coils per terminal unit 2 1
Water distribution piping 2 sets 1 set
Heating and cooling either or both mutually simultaneously exclusive
Temperature control direct direct
Humidity control direct indirect (if heating coil downstream of cooling coil)
4-pipe 2-pipe
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004
Questions????
Introduction to HVAC
Air Conditioning Clinic TRG-TRC018-EN © American Standard Inc. 2004