Fans for Air Distribution System CHP 34

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