1. Objectives Discuss Rotary Heat Exchangers
In Psychometric Chart
Learn about Specifics of VAV and DOAS Systems
Start with Duct Design

2. Sensible and Enthalpy wheels

3. VAV Example One system Multiple Spaces/Zones
- VAV box for each space/zone

4. 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 , Z=max(Xi)
Fraction of outdoor air in system supply air
X = sum(VOA ) / sum(VSA)
Required Fraction of outdoor air:
Y=X/(1+X-Z)

5. Other Issues Related to VAV
Reheaters (sizing and control)
Fan control
Minimum supply air
Occupancy sensors

6. DOAS System

7. DOAS with multi-split systems
Fresh air?

8. DOAS fresh air configurations

9. DOAS fresh air configurations

10. 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)

11. Pressures Static pressure Velocity pressure
Total pressure – sum of the two above

12. Relationship Between Static and Total Pressure

13. Duct Design
Total and static pressure drops are proportional to square of velocity
Plot of pressure drop vs. volumetric flow rate (or velocity) is called system characteristic

14. System Characteristic

15. Electrical Resistance Analogy

16. Frictional Losses

17. Non-circular Ducts
Parallel concept to wetted perimeter

18. Dynamic losses Losses associated with Two methods
Changes in velocity
Obstructions
Bends
Fittings and transitions
Two methods
Equivalent length and loss coefficients

19. Loss Coefficients
ΔPt = CoPv,0

21. Example 18.7
Determine total pressure drop from 0 to 4

22. Conversion Between Methods

23. Reading asignement
Chapter 18
(including 18.4)