Objectives

1
Objectives

• Further discuss the Exam problems
• Learn how to design VAV systems
• Discuss the final project
• Cooling and heating Load calculation

2
VAV Example

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

http//www.trane.com/commercial/library/vol242/v24
b6.asp
3
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)

4
Example Solution
Space1 Space 2 Space 3 Space 4
VSA
VOA
Xi
X
Z
Y
5
Other Issues Related to VAV

• Fan control
• Minimum supply air
• Occupancy sensors

6
DOAS System

• www.doas.psu.edu

7
Project
Commercial building
Zone orientation
8
Project
Cooling and heating load for each zone and whole
building
Fresh air requirement based on number of
occupants
To provide acceptable IAQ in the building,
ventilation system supply minimal amount of
fresh air is in all spaces (except plenums)
that produce 0.2 ACH.
9
Cooling load calculation

• Mostly computer based
• Handouts for manual calculation
• http//www.ce.utexas.edu/prof/Novoselac/classes/AR
  E346N/Handouts/heatloss_table_2008.doc
• http//www.ce.utexas.edu/prof/Novoselac/classes/AR
  E346N/Handouts/ASHRAE_20Gains_Calculation_Tables.
  doc
• The most important issues