System Impedance
- Laminar vs. Turbulent
- Entrance/Exit losses
- Velocity Head
- Filtration
- Push vs. Pull
- Fan Obstruction
- System Resistance/Fan Curve
- Pressure Drop vs. Horsepower
Calculating Flow Through a Nozzle
Pressure vs. Suction – Advantages and Disadvantages
Pressure
- Promotes heat transfer but distribution may be poor
- Air Leakage is outward keeping out dust (if filtered at fan)
- Fan handles coolest air which is more dense so mass flow is greatest
- Fan runs cooler- longer life
- Fan motor heat dissipates into cooling air stream
Suction
- Air distribution is more even
- Air Leakage is into enclosure, contaminating with dust
- Fan sees warmer air, delivering less mass flow due to lower density
- Higher temperature can reduce fan life
- Fan motor heat is not dissipated into cooling air stream