IPE Flashcards
FANS AND BLOWERS
Machine for applying power to a gaseous fluid, to increase its energy content. This energy enables movement or flow of the gas various degree of resistance.
Fan
Functions of Fan
a. Heating, ventilating, or air-conditioning of buildings.
b. Drying and cooling of materials and products.
c. Pneumatic conveying of materials
d. Dust collection, separation and exhaust.
e. Industrial process work
f. Mine and tunnel ventilation
g. Forced and induced draft of steam generation plants.
Two Major Parts
- Wheel or impeller
- Housing
The rotating member of the fan
Wheel or impeller
The stationary member of the fan. The housing is provided with an intake opening (inlet) and with the discharge opening (outlet)
Housing
True or False
The flow of air or gas is carried by the pressure differential
created by the energy transmitted to the gas by the rotating
wheel.
* If no resistance to flow exists, no inlet and outlet duct, the
fan provides the gas with velocity energy only, and no
compression or rarefaction occurs.
* When inlet and outlet duct is added, resistance is imposed and
partial compression occurs on the outlet side, whereas partial
rarefaction occurs on the inlet side.
* The extent of the resistance imposed at the discharge governs
the quantity of the gas delivered by the fan.
* The greatest volume is delivered under zero resistance or
“free delivery” conditions.
* At infinite resistance, volumetric delivery is zero,
corresponding to “blocked tight” or “static no delivery”
condition.
Fan Classes
Centrifugal Fan
Axial- Flow Fan
It consists of an impeller of the squirrel-cage type, operating within a scroll-type housing and including driving mechanism supports either for belt drive or direct connections. Gas enters the inlet in a direction substantially parallel with the impeller axis and turns through an angle of approximately 90, flowing radially through the wheel and issuing from the wheel periphery.
Centrifugal Fan
General Wheel Types of a Centrifugal Fan
- Straight-blade fan
- Forward-curved blade fan
- Backward curved blade fan
Have rotors of comparatively large diameter with a few (5 to 12) radial blades resembling paddle wheels. These fans operate comparatively at low speed. They are often used in exhaust work particularly where wastes are carried into the air stream.
Straight-blade fan
Usually of multi- blade (20-64) “siruco type”. The rotors are of smaller diameter, and they operate at higher speed than straight blade units.
Forward-curved blade fan
Are of the multi-blade (10-50)
type. Such fans have wide range of usefulness.
Backward curved blade fan
It has a wheel of the propeller or disk type, operating within
a mounting ring or cylindrical housing. Gas flow is essentially parallel to the wheel axis at both inlet and outlet.
Axial- Flow Fan
General Wheel Types of a Axial Flow Fan
Propeller fan
Tube-Axial fan
Vane-axial fan
It consists of a propeller or disk type wheel within a mounting ring or plate and including driving mechanism supports either for belt drive or direct connection.
Propeller fan
