· 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