Mechanical Air Movement Flashcards
List two groups or classes of fans
Axial (propeller) fans
Centrifugal (radial) fans
List three types of axial-flow fans
Propeller fans
Tubeaxial fans
Vaneaxial fans
Can propeller fans handle large volumes of air
Yes, large volumes of air at a low static pressure
Can you connect ductwork to a tubeaxial fan?
Yes because they are designed for ducted applications
What is the difference between a tube axial fan and a vane axial fan
addition of guide vanes behind the wheel to improve efficiency by straightening the flow of air
What is another name for a centrifugal fan ?
Squirrel cage type fan
Provide the uses and application for a forward curved fan
Suitable for clean air heating, air conditions and ventilation applications
Provide the uses and application for a radial blade fan
Self cleaning and suitable for material transport such as, wood chips and grain systems. Used for heavy duty dust loads
What does CWBHD stand for
Clockwise Bottom Horizontal Discharge
How is the fan motor location determined
By facing the drive side of the fan and designating the positions by letters W,X,Y ,Z
Can the placement of fittings in relationship to the fan be critical
Yes, improper placement can result in excessive turbulence
How much straight duct is required after a fitting to achieve 100% effective duct length, for systems with an air flow of 2500 fpm or less
You need 2.5 times the duct diameter to achieve 100% effective length
What items would cause system resistance or pressure losses in an HVAC system
Pressure losses come from fittings, filters, coils, dampers etc.
List five pieces of information that can be found on a fan performance chart
Model, Shaft diameter, Maximum BHP , CFM, Outlet Velocity
What damper is installed in branch fittings
Splitter Damper
When would air extractors be used
Where there is not an adequate amount of room to mount a splitter damper to efficiently direct the correct amount of air down the branch line or diffuser takeoff
List three important functions of multi-blade dampers
To control and mix outside air with return air
To bypass heat transfer equipment
To control air quantities handled by the fan
Name two styles of multi-blade dampers
Parallel Blade
Opposed Blade
Describe fan total pressure
The sum total of a fan’s static pressure and its velocity pressures.
What fan blade is suitable for use in restaurants and places where moisture and dust is present in the air
Backward inclined blade
Which blade is the most quiet and efficient
Airfoil blade
Which fan blade is designed for material handeling and heavy duty dust loads
Radial blade
What type of fan is used to provide air curtains above doors
Cross flow fan
Which is fan is the MOST effecient
Vaneaxial fan
In which fan does air leave the impeller at right angles
Centrifugal fan
What are the advantages of forward curve blades compared to backward inclined blades
Quiet and more efficient than backward inclined blades
What class of fans are suitable for low volumes and pressures
Axial flow fans
Propeller fans can be directly mounted to a wall
T or F
True
In what two ways do centrifugal fans produce pressure
Centrifugal force and Kinetic energy
What do forward curve blades depend more on ?
Velocity pressure
Forward curved blades are common in wheel diameters up to 24”
T or f
True
What type of fan is used where low sound levels are critical
Mixed flow fan
How is rotation and discharge determined
Fan drive position
Define system resistance curve
Sum of pressure losses in the system
What type of damper is used in non- ducted applications
Nested inlet vane dampers
