1. Objectives - Learn about fans and fan curves
- Solve examples related to duct design
- Learn about fans and fan curves

2. Frictional Losses

3. Non-circular Ducts
Parallel concept to wetted perimeter

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

5. Loss Coefficients
ΔPt = CoPv,0

7. Electrical Resistance Analogy

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

9. Conversion Between Methods
Se Example 18.8 and compare with 18.7

10. Fans Driving force to move air in buildings
Raise pressure and produce flow
Two main types:
Centrifugal
Axial

11. Relevant Fan Parameters
Total pressure rise
Static pressure rise
Power requirement
Efficiency
Note ηtot does not account for motor efficiency

12. Balance Point

13. Fan Performance

14. Centrifugal fans

17. Axial Fans

20. Fan Laws “Approximate relationships”
Given two aerodynamically similar fans, can extrapolate performance data
Be very careful

21. Question
How does fan power consumption vary with volumetric air flow rate?

22. Controlling Air Flow

23. Dampers

24. Effect on Fan Curve

25. VAV Operation

26. Summary of Air Distribution Systems
Select diffuser based on ADPI
Given a layout of duct system
Calculate total pressure drop
Identify fittings contributing most to pressure drop
Deal with non-circular ducts
Use fitting loss coefficient or equal length method
Select the fan based on fan and duct curve