Axial and centrifugal fans: the most important differences to know

3 February 2022by Andrea Rocco

In the relevant markets, the term 'industrial fan' does not have a clear definition and in this article we want to explain what industrial fans are, specifically axial and centrifugal models and their differences.

An axial fan is a fan in which the extracted air is forced to move parallel to the shaft around which the blades rotate. Centrifugal fans, on the other hand, extract air perpendicular to the fan inlet, and spin it towards the outlet due to deflection and centrifugal force. The impeller rotates, allowing air to enter the fan near the shaft and move perpendicularly from the shaft towards the opening in the fan casing.

Axial fans replace the centrifugal fan in certain fields of application from a functional point of view, operating at higher specific speeds with smaller diameters.

An axial fan, with the same flow rate and pressure, has the following differences to a centrifugal fan:

  • has a smaller impeller diameter
  • has a higher dynamic pressure
  • has a significantly higher operating speed
  • the peripheral speed is greater
  • has lower efficiency and therefore higher energy consumption
  • is much louder
  • is significantly smaller and lighter, and less expensive

The most significant data in this comparison are weight, operating speed and noise. The operating speed comparison shows that the same flow and pressure characteristics can be obtained from axial fans at higher operating and peripheral speeds than centrifugal fans. Since there is a limit to the stresses in the rotating bodies, and hence to their peripheral speeds, we can safely say that pressures of a certain magnitude are more easily obtained with centrifugal fans than with axial fans.

Axial fans are generally noisier and it is often the case that an axial fan requires the use of silencers to reduce noise, whereas a centrifugal fan would not.

But these negative aspects are countered by a lower weight, less space occupied, a lower cost and the parallelism of the two suction and discharge nozzles, which make it easy to fit into the system, where the axial fan becomes nothing more than a piece of pipe, while the centrifugal fan requires a more complex solution.

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