Centrifugal vs Axial Fans

Most cooling towers use some type of fan to move air. The manufacturer can use a centrifugal (squirrel cage) type fan or an axial (propeller) type fan.

So, which is best? Well, both have advantages.

Centrifugal fans are capable of handling the pressure drop imposed by duct work when cooling towers are located indoors. The downside is they typically consume approximately 2x the horsepower of axial fans.

Axial fans are more efficient; Just don't use them with duct work.

Noise is another consideration. Centrifugal fans are inherently quieter than axial fans. This is especially noticeable with blow thru towers where the fan shafts are horizontal and the fans are clearly visible.

Blow thru centrifugal fans are better suited for winter operation; Blow thru axial fans are the worst. The increased energy cost can be a bargain when compared to the labor cost of deicing axial fans.

Both respond well to variable speed drives. The horsepower requirement relates to the cube of fan speed. Slowing a fan by just 10% will decrease the HP by 27%!

Axial fans can make a mess if they come apart during operation. They should be inspected periodically for loose fasteners and cracks. Vibration cutout switches help reduce the carnage of operational failure. Centrifugal fans, on the other hand, rarely cause damage upon failure and vibration cutout switches are pretty much a waste of money.

For additional information about selecting the right tower, see my web site: www.expertctr.com/ch_17.php

Don Davis

Expert Cooling Tower Repair, LLC