Objectives

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Objectives

• Psychometrics
• Examples in AHUs

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Humidification
hw Specific enthalpy of water added to
system hg Specific enthalpy of saturated water
vapor
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Evaporative Cooling (air washing)
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Air Washer

• Sprays liquid water into air stream
• Typically, air leaves system at lower temperature
  and higher humidity than it enters

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Air Washers/Evaporative Coolers

• Heat and mass transfer is mutually compensating
• Can evaluate based on temperature drop,
  humidification, or comparison to other energy
  exchangers

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Evaporative Cooler
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Cooling Tower

• Similar to an evaporative cooler, but the purpose
  is often to cool water
• Widely used for heat rejection in HVAC systems
• Also used to reject industrial process heat

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• Processes in AHU and buildings

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Systems Single-Zone Air Systems
Zone any space with a thermostat
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Air conditioning
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Reheat
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Recirculation