Fans Flashcards
What is the primary function of a fan?
To move air, without compression
What are the three types of pressures created by fans?
Static, dynamic, and total pressure
What are the two most common types of fans?
Centrifugal, and Axial
What is static pressure?
Pressure exerted on the inside of the duct walls or piping when there is no air flow in the system
What is velocity pressure?
The pressure caused by moving air in the system.
(Think of a weather vane in a duct)
What are three blade types found in centrifugal fans?
Straight radial. Forward curved. Backwards inclined.
How are centrifugal fans classified?
By the shape and design of the impeller blades
How are axial fans classified?
By their design and duty
What are the three general types of axial fans?
Tube axial. Vane axial. Propeller.
What are the three types
Of mechanical draft?
Induced draft (fan between furnace and stack)
Forced draft (fan blowing through furnace into the stack)
Balanced draft (combination of ID and FD)
What is the most efficient fan blade?
Airfoil (plane wing) - capable of efficiencies of 85%
(However are very fragile)
Where are forward blade fans typically used?
Residential ventilation and HVAC applications
(They’re quiet)
(Limited to clean air)
What are some advantages radial fan blades?
Designed for high pressure services
Easier to maintain
Capable of handling high particulate matter (wood chips, dust, etc)
What are some common fan volume controls?
Louvres, dampers, shaft speed
