What is air flow
The energy given to air by means of a fan in the form of pressure
3 types of Measuring airflow in ducts
Air flow is measured by manometer
1. Static Pressure
On the air duct wall
2. Velocity Pressure
what you can feel the
amount of air travelling
3. Total Pressure
Static pressure and velocity added together
Pressure convertions
Is narrowing of the duct to go thru walls or low clearing areas in ceiling.
Pressure stays the same and acts like the volute design
Hitting the narrow section it looses velocity pressure but gain static pressure and speeds up again after converging sectio
Centrifugal Fans
Same as centrifugal pump
Centrifugal fan classes
Class 1 - up to 0.94 Kpa
Class 2 - up to 1.7 Kpa
Class 3 - up to 3.2 Kpa
Class 4 - more than 3.2 Kpa
3 Types of centrifugal fans
1 Backward inclined
2 Forward inclined Curved blade
3 Backward inclined air f
Propeller Fan
Noisy
High air moving capacity
Low pressure fan
Used in pressure range of 0.03 to 0.06 Kpa
Tube Axial fan
Main use is in exhaust areas
Noisy
Produce pressures up to 0.06 to 0.07 Kpa
Spirals air into duct so friction is allot higher
Vane Axial Fans
Equipped with vanes behind the blade on fan housing
Vanes there to straighten the air flow coming from it.
Direct Drive Fans
Fan or blade is directly connected to the motor on a shaft
V-Belt Driven Fans
Using a pulley system there is a belt connected to motor pulley and to fan or blade pulley that turns the blade.
Alignment on these drives are more forgiving.
V-Belt gaurds
Should only be taken of for maintenance and once all parties working on the unit has locked the unit out.
Variable speed motor control
Very expensive
Variable Inlet Vane control
To control air spin on fan inlet
control the static pressure