The difference is not simply shape. Axial and centrifugal fans move air differently, produce different pressure ranges and place different demands on the installation.
Axial fans are often a sensible choice for high airflow through a relatively open system. Centrifugal fans are usually better suited to longer duct runs, filters or process equipment with more resistance. There is plenty of overlap, so the final answer still comes from the fan curve and the required duty point.
Air path and installation
An axial fan moves air broadly parallel to the shaft. The arrangement is compact and works well for wall, roof, duct and equipment ventilation.
A centrifugal fan draws air into the centre of the impeller and discharges it in another direction through a casing or fan box. This arrangement gives designers more options for higher-pressure duct systems, but the outlet direction and service space need more coordination.
System resistance usually settles the argument
A short duct with a louvre may suit an axial fan. Add long ductwork, several bends, a filter, silencer or dust collector, and the pressure requirement rises quickly. A centrifugal fan may then be the practical choice.
Do not treat “axial means low pressure” and “centrifugal means high pressure” as universal rules. Individual series can overlap, and a poor installation can waste much of the available pressure.
Efficiency, noise and control
Compare efficiency and sound at the design point, not at a catalogue maximum. If the load changes, check the full VFD range. Very low speed may affect motor cooling, while operation outside the recommended curve range can increase noise or vibration.
Gas conditions can change the choice
Dust, corrosion, heat and sticky deposits affect impeller style, material, sealing and cleaning access. A clean-air HVAC selection should not be copied into an abrasive process-exhaust system simply because the airflow is similar.
Selection inputs
- Airflow and system resistance
- Duct layout and available space
- Gas temperature and composition
- Dust or corrosion risk
- Noise limit and control method
- Maintenance access and operating hours
See the T35 Axial Fan and 4-72 Centrifugal Fan for representative arrangements.
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