Tom Lawrence

1
HVAC Systems Overview
2
Agenda

• Psychrometric questions?
• Larger psycho chart
• Email address list
• Project teams formed topics?
• Overview of HVAC systems, types

3
HVAC Systems Overview

• External Factors
• Ambient temperature, humidity
• Solar radiation
• Wind

Equipment

• Internal Factors
• Occupants
• Moisture gains
• Acceptable environment (comfort, health and
  safety)
• Internal air distribution

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

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Type of Systems

• All air
• Water / air
• All water
• Centralized versus decentralized

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Typical thermodynamic processes

• Cooling and dehumidifying moist air
• Evaporative cooling

Humidity Ratio (W)
?
?
Dry Bulb Temperature
Zone conditions, ?
?
?
Nearly saturated supply, ?
?
Ambient
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Typical processes (Contd)

• Heating

?
?
?
?
Ambient
Ambient, ? Zone conditions, ? Mixed zone/ambient,
? Heating to supply air,???
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Direct Expansion Air Conditioning
Outdoor Air
COND
Expansion Valve
Compressor
EVAP
Supply Air
Return Air
Mixed Air
Outdoor Air
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Common System Types

• Central systems, Variable Air Volume (VAV)

Return Fan
Exhaust Air
VAV Supply
Conditioning Coils
Ventilation Air
Supply Fan
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Common System Types

• Central systems, Dual Duct

Heating Coil (Hot Deck)
Exhaust Air
Return Fan
Mixing Boxes
Filters
Ventilation Air
Cooling Coil (Cold Deck)
Supply Fan
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Common System Types

• Fan Coil Units (Unit Ventilator)

Supply Air
Supply Fan
Cooling Coil
Heating Coil
Drain Pan
Filters
Ventilation Air
Return Air
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Common System Types

• Packaged Unit (Rooftop or Sidewall)

Direct Expansion Cooling Heat Pump or Gas Fired
Heating
Supply Air
Return Air
Alternate Supply and Return Ductwork
13
Common System Types

• Split-System

Return Air
Condensing Unit
Furnace
Evaporator
Refrigerant Lines
Supply Air
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Chilled Water Systems
Cooling Tower
Chiller
Chilled Water System
????
Various System Loads (Coils)
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Energy Recovery from Ventilation Air

• One common approach is enthalpy wheel

Exhaust
Intake
Outdoor Air
Exhaust Air
Cooling Mode
Supply Air
Return Air
Heating Mode
Supply Air
Return Air
OA
Exhaust Air
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Economizer Systems
Return Air
Exhaust Air
Recirculation Air
Supply Air _at_ Mixed Conditions
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

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Economizer Systems
?
?
?
Ambient
Ambient, ? Zone conditions, ? Mixed zone/ambient,
?
Mixed air conditions
Cooling provided to building