Air Blowers, Centrifugal Fans and Air Movers

Axial or centrifugal: airflow versus pressure

Axial fans, which push air straight through a propeller, move large volumes against little resistance and suit open rooms, cabinets and cooling through a wide opening. Centrifugal blowers throw air outward from a wheel and build far more pressure, which is what you need to push through filters, ducts, heatsinks and tight enclosures. Pick the type before the size.

Two figures describe performance: airflow, in CFM or cubic meters per hour, and static pressure, in inches of water or pascals. A fan that moves plenty of air in free space can deliver far less once it pushes against a filter or duct. Compare the fan curve if the maker gives one. Portable and wearable fans trade performance for convenience.

Voltage, current and speed: powering the blower

Supply voltage is the first filter. Small blowers and case fans run on 12 V or 24 V DC and list their current in amps, so the supply must deliver at least that. Larger blowers run on 120 V or 230 V AC, and some industrial models need 400 V. A 12 V blower on a 24 V supply can overspeed or burn out. Battery-powered portable fans list capacity in watt-hours.

Speed and noise go together. Noise rises quickly with rotational speed, so a larger fan turning slowly moves the same air more quietly than a small fast one. Bearing type affects life: ball bearings tolerate heat and any mounting angle, while sleeve bearings are usually quieter but wear sooner. Mounting hole spacing, frame size and airflow direction must match your enclosure.

Questions about Air Blowers, Centrifugal Fans and Air Movers

What do CFM and static pressure tell me?

CFM is the volume of air a fan moves in free air. Static pressure is how hard it can push against resistance such as a filter, duct or heatsink. For restricted airflow, pick a fan whose pressure rating suits the resistance, not just the one with the highest CFM.

Can I run a 12 V blower from a 24 V supply?

No. Running it at twice its rated voltage can overspeed the motor and burn it out. Use a matched 12 V supply, or a DC-DC converter that steps 24 V down to 12 V and can supply the blower's current.

How can I make a noisy blower quieter?

Noise comes from speed, turbulence and vibration. Reduce speed with a suitable controller, use a larger fan at lower RPM, add rubber mounts, and keep grilles and inlets unobstructed. Worn bearings also grind or whine and are best replaced.