Air-Conditioning Systems
Purpose of an air-conditioning system is to control indoor air parameters within required thermal comfort and indoor air quality. To achieve required indoor air parameters, the system: heat, cool, humidify, dehumidify and filter outdoor air.
HVAC Subsystems
See Figure on the next page:
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End Use
Consumes capacity to condition space air or air stream supplying space. Air-conditioning systems = air handling systems + ducts + air distribution devices
How to select an air-conditioning system?
• Performance requirements (loads, process)
• Capacity requirements (building types, loads)
• Spatial requirements (building types)
• First costs (location, size of HVAC, investment)
• Operating costs
• Reliability
• Flexibility
• Maintainability
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R. nm INC, PRODUCTION |
Classification in terms of system:
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Classification in terms of air supplied
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Classification in terms of load carried:
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-Q — W Qfw Air-water |
All-air
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Q — Q.-W |
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^ Q w |
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Ti |
RҐi |
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All-water |
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Q — Q.-W |
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^Qw |
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Ti |
N |
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Refrigerant |
Convert primary energy for heating/cooling. Energy sources:
• Coal
• Natural gas
• Fuel oil
• Biomass
Produce steam and electricity.
Heating production equipment:
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A packed fire-tube boiler, (iCourtesy of Federal Corp., Oklahoma City, OK) |
Cooling production equipment:
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Vapor compressor:
• Refrigerant
• Compressor
• Drive (usually electric motor)
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Components in a Vapor-Compression Refrigeration Cycle |
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Waiei-wetEd
Centrifugal chiller cutaway drawing (iCourtesy United Technology Cairier) |
Heat rejection:
• Disposes of heat from cooling process
• Cooling tower, evaporative condenser, air-cooled condenser
• “Sink” for waste heat: ambient dry bulb, ambient wet bulb, ground, surface water
• Trades offs between cost and COP
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Forced-draft cooling tower (Courtesy Marley Co.) |
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CLC CIR< |
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CLOSEO CIRCUIT |
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CLOSED-CIRCUIT HEAT EXCHANGE COIL |
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Moves capacity from production to use. Water and steam distribution:
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Air distribution: O
Centrifugal fan (iCourtesy of the Train Company, LaCrosse, WT)
Packed equipment Air-handling unit: O
Posted in Fundamentals of Heating. Ventilating, and Air-Conditioning