Background Knowledge:

inWC (inches of water column): Pressure unit, frequently used in fans to represent small changes in pressure
What is static pressure?
- Relative pressure to ATM?
- fans produce positive static pressure
Air moving through a pipe (constant diameter) will have max air velocity at center and zero at pipe walls
Flow rate is calculated as : Q (flow rate) = A (cross-sectional area) x V (average velocity of the fluid)
- Avg velocity is 90% the max velocity of the velocity
Find Reynold's Number of the fluid:
- Needed to see if the flow is laminar or turbulent
  - If Re < 2000, laminar flow
  - If higher turbulent
Total Pressure: Static Pressure + Velocity Pressure
- Used to calculate mech efficiency
Bernoulli's principle of continuity:
- When air velocity increases, the static pressure decreases.
- When air velocity decreases, the static pressure increases.
Centrifugal fans with FC Blades (Forward Curved)

University of Waterloo Robotics Design Team > Centrifugal Blowers: > image2021-10-17_0-9-12.png

Vacuum Cleaners centrifugal fans usually have 6-8 blades
50 > CFM is needed to transport sand
- Have at least a safety factor of 1.5-2 to account for frictional pressure drops in the pipes.
In suspended flow of particles in air, the particle's velocity is 80% of that of average air velocity in horizontal pipeline
Material to air ratio, 2:1
Vacuum cleaners use diffusers
Performance of a typical vacuum cleaner
Motor and Drive Arrangements for centrifugal fans
One Big Disadvantage of FC Fans:
- Brake horsepower overloading during free delivery, hence oversize motor is used as a precaution.
Mitigate static pressure
Fan Laws?
Specific Speed and Specific Size?
Understand static pressure better