What is a fan, Fan Information, How does a fan work, Air system fan

What is a fan speaks to fan information, how does a fan work and air system fan.

It is stated that the fan is the air moving component of the air distribution system. Fans may be a portion of a built-up system in which coils, filters, motors and drives are assembled at the job site.

It may be part of a packaged or self contained unit which is factory assembled complete with coils, filters, motors and drives and delivered to the job site. Here the duct work is attached to complete the air distribution system.

Fans are grouped in two general commercial fans categories:

  • Centrifugal, which the air flows radially through the impeller. These fans are classified according to wheel blading; forward curved, backward curved and radial (straight).

  • Axial flow, in which air flows axially through the impeller. These fans are classified as propeller (disc) tubeaxial and vane axial.

    When a duct system is needed in an air conditioning application, a tube axial or centrifugal fan may be used. Where there is no duct system and little resistance to air flow, a propeller fan can be applied. However, self contained equipment often use centrifugal fans for applications without duct work.

    Centrifugal Fan

    The centrifugal fan is used in most comfort applications because of it's wide range of quiet, efficient operation at comparatively high pressures.

    In addition, the centrifugal fan inlet can be easily attached to a system of large cross section while the discharge is easily connected to small ducts.

    Air flow can be varied to match air distribution system requirements by simple adjustments to the fan drive or control devices.

    Axial flow fans are excellent for large air volume applications where higher noise levels are of secondary concern. They are therefore often used for industrial air conditioning and ventilation.

    These high velocity fans require guide vanes to obtain the best efficiency when operating against pressures considered normal for centrifugal fans. However these fans may be used without guide vanes.


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