J. Michael Carson P.E. Senior Mechanical Engineer Purdue University THE MODERN HVAC SYSTEM
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J. Michael Carson P.E.
Senior Mechanical Engineer
Purdue University
THE MODERN
HVAC SYSTEM
HVAC Systems
Btu Ton Heat Gain & Heat Loss Air Handling Unit Fan Air Distribution Preheat Coil Cooling Coil Reheat Coil
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Double Duct Diffuser Grille Register Constant Volume VAV DOAS Chilled Beam UFAD
HVAC Systems
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HVAC Systems
Carrier
Fahrenheit
Watt
Fulton
Galileo
Celsius
Physical Sciences have a long
history of discovery
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HVAC Systems
Their work is based on energy transfer
Leading to today’s HVAC Engineer
The energy they transfer is
HEAT 4
HVAC Systems
Heat is always moving
Flows from higher energy (something hot)
to lower energy (something cold) 5
HVAC Systems
1 BTU = 1 lb of water 1°F
How we measure heat in America
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BTU (BRITISH THERMAL UNIT)
HVAC Systems
QUIZ #1
Circle your answer
1 Btu/Hr
1 BTH
1 BTUH
If it takes one hour to heat 1 lb of water 1°F the heat transfer rate would be …
“A foolish consistency is the hobgoblin of little minds”
Being well read engineers understand Ralph Waldo Emerson
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HVAC Systems
“A foolish consistency is the hobgoblin of little minds”
This helps you understand the HVAC engineer
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QUIZ #1
HVAC Systems
QUIZ #2 What was a favorite treat
Washington and Jefferson
served summer visitors?
How could they eat ice cream in the summer of 1700’s?
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HVAC Systems
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ICE HARVESTING
HVAC Systems
1 Ton
When one ton of ice melts in one day
(24 hours) what do we call the heat
absorbed by that ice each hour?
QUIZ #3
1 Ton = 12,000 Btu/Hr 11
HVAC Systems
No
Is there such a thing as one ton of heat? QUIZ #4
Now what did Emerson say? 12
HVAC Systems
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THE BACKBONE OF HVAC DESIGN
What makes heat?
Lights
People
Equipment
Walls & Windows
Solar
How do we get rid of the heat?
HEAT GAIN & LOSS CALCULATION
HVAC Systems
Originally installed in special rooms
Fan, Cooling coil, Ductwork, Filters, Diffusers & grilles, Condensing unit, etc.
What did we do if we had multiple rooms?
1950s more people wanted AC
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AHU (AIR HANDLING UNIT)
HVAC Systems
ADVANTAGES
HOW WE REMOVED THE PROBLEMS
• Everybody gets AC
DISADVANTAGES
• Exterior appearance
• Maintenance
• Noise
• Floor space
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1950S MULTIPLE AHUS
HVAC Systems
1960 CENTRAL STATION AHU
ADVANTAGES
• Serves many rooms
DISADVANTAGES
• One zone
• No outside air • Noise is isolated
• Localized maintenance, few pieces of equipment
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HVAC Systems
1960 CENTRAL STATION AHU
ADVANTAGES
• Serves many rooms • Noise is isolated • Low maintenance
DISADVANTAGES
• One zone • Air can’t get back
to the AHU
• Fresh air
Energy Tips
1. No more OA than necessary
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HVAC Systems
1963 CENTRAL STATION AHU
Energy Tips
1. No more OA than necessary
2. Fan operation
ADVANTAGES
• Serves many rooms • Noise is isolated • Low maintenance • Fresh air • Pressure Control
DISADVANTAGES
• One zone • Cools in winter
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HVAC Systems
1965 AHU W/ ECONOMIZER
Energy Tips
1. No more OA than necessary
2. Fan operation
3. Economizer operation
4. Damper operation
ADVANTAGES
• Serves many rooms • Noise is isolated • Low maintenance • Fresh air • Pressure Control • Economizer
DISADVANTAGES
• One zone
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HVAC Systems
OIL EMBARGO!!
1966 DOUBLE DUCT
ADVANTAGES
• Serves many rooms • Noise is isolated • Low maintenance • Fresh air • Economizer • Room level control • Flexible
DISADVANTAGES
• Uses a lot of energy
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Energy Tips
1. No more OA than necessary
2. Fan operation
3. Economizer operation
4. Damper operation
5. Remove simultaneous
heating and cooling
HVAC Systems
1975 SHUT-OFF VAV
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ADVANTAGES
• Serves many rooms • Noise is isolated • Low maintenance • Fresh air • Pressure Control • Economizer • Saves Money
DISADVANTAGES
• Poor air quality • Poor humidity
control • Poor temperature
control
SICK BUILDING SYNDROME!!
HVAC Systems
1980S VAV WITH REHEAT
1990S VFD!!!!
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ADVANTAGES
• Serves many rooms • Noise is isolated • Low maintenance • Fresh air • Pressure Control • Economizer • Saves Money
DISADVANTAGES
• No good speed control (mechanical)
HOW DO THEY WORK?
HVAC Systems
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60 Hz
60 Hz
45 Hz
30 Hz VFD OPERATION
HVAC Systems
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60 Hz
60 Hz
45 Hz
30 Hz VFD OPERATION
HVAC Systems
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60 Hz
60 Hz
45 Hz
30 Hz VFD OPERATION
HVAC Systems
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60 Hz
60 Hz
45 Hz
30 Hz
HVAC Systems
1990S VAV REHEAT VFD
BEEN THE WORKHORSE FOR
20 YEARS
WHAT IS ON THE HORIZON?
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DOAS
HVAC Systems
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DOAS
HVAC Systems
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DOAS
HVAC Systems
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DOAS
ADVANTAGES
• Small AHU • Small ductwork • Less energy??
DISADVANTAGES
• FCUs or other room level system
OFFICES, DORMS, ETC.
CHILLED BEAMS
HVAC Systems
CHILLED BEAMS
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HOW DO THEY WORK?
HVAC Systems
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CHILLED BEAMS
HVAC Systems
CHILLED BEAMS
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HVAC Systems
UFAD 34
CHILLED BEAMS
ADVANTAGES
• Small AHU • Small ductwork
DISADVANTAGES
• Can take many chilled beams
• Careful temp control
HVAC Systems
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UFAD
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UFAD
HVAC Systems
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UFAD
ADVANTAGES
• Small AHU • Small ductwork • Less energy??
DISADVANTAGES
• Careful construction details
• Careful temp control
J. Michael Carson P.E.
Senior Mechanical Engineer
Purdue University
THE END OF THE
MODERN HVAC SYSTEM
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