What fan should I choose …. Axial or centrifugal?

Axial or centrifugal? It’s often taken for granted that everyone knows what fan type to choose for given applications. However, it’s never a bad time to review some fundamental concepts. So, let’s take a moment and cover a few basic ideas.

Many of you have most likely been told a characteristic of centrifugal fans is that they have higher pressure and lower airflow capabilities than axial fans. However, axial fans have higher airflow and lower pressure capabilities. So, what can this mean in the type of fan for a given application?

First let’s consider whether the application is ducted or not.

For non-ducted applications a good solution would be an axial fan. Axial Fans can move a lot of air against very little working pressure. One should also be aware that a forward curved centrifugal fan may not work at all in a non-ducted application.  The forward curved centrifugal fan has what is termed a rising horsepower curve. That is, its horsepower increases with a decrease in pressure. In essence, the motor of a forward curved centrifugal fan can fail if operating against no resistance.

Now, let’s consider ducted applications. With ducting there will be resistance to airflow and this is measured in terms of pressure. The more ductwork, fittings, dampers, filters, etc., the higher the resistance to airflow will be, thus the higher the pressure. To overcome the higher pressure, a fan capable of producing airflow at the higher pressure is required. The ideal choice for this scenario is a centrifugal fan. There are different types of centrifugal fans to apply, however we will save that for another time.

There are lots of resources for fan selection available on the internet, and the AMCA (Air Movement and Control Association) publications Air Systems and Fans and Systems provide excellent fundamental information regarding fan operation.

While the above information may be simplistic, the hope is that it does provide some basic background of when to apply an axial versus a centrifugal fan. View our full line of Industrial fans.

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