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HVAC Systems Overview. Agenda. Psychrometric questions? Larger ‘psycho’ chart Email address list Project teams formed… topics? Overview of HVAC systems, types. HVAC Systems Overview. External Factors Ambient temperature, humidity Solar radiation Wind. Equipment. Internal Factors - PowerPoint PPT Presentation
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Tom LawrenceUniversity of Georgia
HVAC Overview - # 2
Agenda
• Psychrometric questions?– Larger ‘psycho’ chart
• Email address list
• Project teams formed… topics?
• Overview of HVAC systems, types
Tom LawrenceUniversity of Georgia
HVAC Overview - # 3
HVAC Systems Overview
Equipment
External Factors• Ambient temperature, humidity• Solar radiation• Wind
Internal Factors• Occupants• Moisture gains• Acceptable environment (comfort, health and safety)• Internal air distribution
Tom LawrenceUniversity of Georgia
HVAC Overview - # 4
General Design Issues with HVAC
• Determine required indoor conditions – Temperature and humidity
levels
– Ventilation
• Determination of loads (cooling or heating)– Heat transmission through
building shell
– Heat gains from occupants
– Heat gains from lighting and equipment
– Ventilation and infiltration/exfiltration
• HVAC system type– Building size, # of subdivisions
– Local energy prices
– Local climate
– Initial cost versus life cycle cost
• Other considerations– Energy usage
– Indoor air quality
Tom LawrenceUniversity of Georgia
HVAC Overview - # 5
Type of Systems
• All air
• Water / air
• All water
• Centralized versus decentralized
Tom LawrenceUniversity of Georgia
HVAC Overview - # 6
Typical thermodynamic processes
Cooling and dehumidifying moist air
Evaporative cooling
Dry Bulb Temperature
Hu
mid
ity
Rat
io
(W)
AmbientNearly saturated supply,
Zone conditions,
Tom LawrenceUniversity of Georgia
HVAC Overview - # 7
Typical processes (Cont’d)
Heating
Ambient
Ambient, Zone conditions, Mixed zone/ambient, Heating to supply air,
Tom LawrenceUniversity of Georgia
HVAC Overview - # 8
Direct Expansion Air Conditioning
EVAP
Return Air
Outdoor Air
Mixed AirSupply Air
Outdoor AirCOND
Expansion Valve
Compressor
Tom LawrenceUniversity of Georgia
HVAC Overview - # 9
Common System Types
Central systems, Variable Air Volume (VAV)
Supply Fan
Return Fan
Ventilation Air
VAV SupplyExhaust Air
Conditioning Coils
Tom LawrenceUniversity of Georgia
HVAC Overview - # 10
Common System Types
Central systems, Dual Duct
Supply Fan
Return Fan
Ventilation Air
Mixing BoxesExhaust Air
Cooling Coil (Cold Deck)
Filters
Heating Coil (Hot Deck)
Tom LawrenceUniversity of Georgia
HVAC Overview - # 11
Common System Types
Fan Coil Units (Unit Ventilator)
Supply Fan
Ventilation Air
Cooling Coil
Filters
Return Air
Heating Coil Drain Pan
Supply Air
Tom LawrenceUniversity of Georgia
HVAC Overview - # 12
Common System Types
Packaged Unit (Rooftop or Sidewall)
Return AirSupply Air
Alternate Supply and Return Ductwork
Direct Expansion CoolingHeat Pump or Gas Fired Heating
Tom LawrenceUniversity of Georgia
HVAC Overview - # 13
Common System Types
Split-System
Return Air
Supply Air
Furnace
Evaporator
Condensing Unit
Refrigerant Lines
Tom LawrenceUniversity of Georgia
HVAC Overview - # 14
Chilled Water Systems
Cooling Tower
Chiller
Various System Loads (Coils)
Chilled Water System
Tom LawrenceUniversity of Georgia
HVAC Overview - # 15
Energy Recovery from Ventilation Air
• One common approach is enthalpy wheel
Exhaust
Intake
Cooling Mode
Return Air
Supply Air
Exhaust Air
Outdoor Air
Heating Mode
OA
Return AirSupply Air
Exhaust Air
Tom LawrenceUniversity of Georgia
HVAC Overview - # 16
Economizer Systems
Supply Air @ Mixed Conditions
Return Air
Recirculation Air
Exhaust Air
Outdoor Air
• Get ‘free cooling’ by using up to 100% outdoor air supply to room
• Controllers use enthalpy (T and H) or temperature only for control decision