Objectives

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Objectives

• Finish with fans
• Learn about DOAS and VAV
• Project related topics

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Fan Performance
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Centrifugal fans
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Axial Fans
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VAV

• with no re-heaters
• with re-heaters
• with fan terminal unis

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VAV Example

• One system
• Multiple Spaces/Zones
• - VAV box for each space/zone

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VAV System Terms Equations(you can find them
in ASHRAE Standard 62)

• Fraction of minimum outdoor air in space/zone
  supply air
• Xi VOAi / VSAi
• Critical space
• Space with maximum Xi , Zmax(Xi)
• Fraction of outdoor air in system supply air
• X sum(VOA ) / sum(VSA)
• Required Fraction of outdoor air
• YX/(1X-Z)

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Example Solution
Space1 Space 2 Space 3 Space 4
VSA
VOA
Xi
X
Z
Y
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Other Issues Related to VAV

• Reheaters
• Fan control
• Minimum supply air
• Occupancy sensors

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DOAS System

• www.doas.psu.edu

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DOAS with multi-split systems
Fresh air?
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DOAS fresh air configurations
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DOAS fresh air configurations
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Issues Related to DOAS

• Split of sensible and latent load
• Selection of hydronic system
• Winter vs. summer operation
• Winter operation with DX systems (heat pump)

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Course Project