Axial or Centrifugal Fan?

In many applications the choice of axial or centrifugal fan is obvious, in others both types can be used. In the latter cases Howden engineers can assist the customer to come to the optimum choice for each application.

The main criteria to be assessed are:

Aerodynamics
Axial fans are more suited to supplying higher flows at lower pressures (high specific speed duties) whilst centrifugal fans are more suited to supplying lower flows at higher pressures (low specific speed duties).

Dust
Centrifugal fans are more resistant to erosion by gas-borne dust and can be fitted with substantial replaceable liners and/or hard surfacing.

High temperatures
Centrifugal fans can tolerate much higher temperatures, and temperature fluctuations than variable pitch axial fans

Flow control
At lower loads, the higher efficiency of a variable pitch axial fan cannot be matched by constant speed centrifugal fans.

Layout
The available space in an installation may be the determining factor on which type of fan to use, as axial and centrifugal fans have significantly different footprints.

Electrical supply
The higher inertia of a centrifugal fan will require a higher current to start the fan from rest, which may be a significant factor if there is a constraint in the electrical supply to the plant.

Acoustics
Both fan types tend to generate similar levels of noise for a given duty, with lower frequencies more dominant in the centrifugal fan, and mid-frequencies in the axial. Noise from a variable pitch axial fan will reduce at lower loads, whereas noise will increase from a constant speed centrifugal fan when inlet vanes or dampers are closed.  

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