Axial Fan: An axial fan produces a large flow rate (CFM) with relatively small pressure gain. They have a motor centered in the ductwork with blades attached radially. The progress of the air is straight through the impeller parallel to the shaft.

Centrifugal Fans: Often called “squirrel cage” fans, a centrifugal operates on the principle of “throwing” air away from the blade tips. The air is led through the inlet pipe to the center of the impeller, which forces it radially (making a right-angle turn) outward to the volute, from which it flows into the discharge pipe. A centrifugal fan has a comparatively smaller flow rate (CFM) with a larger pressure rise. The design of a centrifugal fan necessitates either riveted or welded blades. For centrifugal fans the pressure rise, and necessity of welded/riveted blades, means the likelihood of stress fractures and fan failures is increased.

The performance of either fan depends on the shape and speed (RPM) of the impeller – 3600 RPM is the standard speed for fans in the car wash industry.  Axial Fans typically require less motor HP due to aerodynamic design, making them more efficient.  For safety and effectiveness, it is important to note, the air delivery system must be tailored for each specific fan to be effective.

Every drying system relies on a combination of volume and pressure. Neither pressure alone nor volume alone can effectively move fluid. Almost every type of blower used in the car wash industry relies more on pressure than volume to dry a car. Aerodry has chosen to use a high-volume Axial fan.

A correctly installed air delivery system should provide complete vehicle coverage and adequate force to remove properly treated rinse water. Only a small amount of pressure is necessary to break surface tension on a clean car. The volume (CFM – cubic feet per minute) along with the “weight” of that CFM will effectively remove the water. This concept can be better understood using the following example:

Using an adjustable water nozzle, imagine washing debris from a driveway with a narrow, high-pressure stream. The narrow setting delivers water at a high pressure, but with limited volume, it’s a narrow path with limited movement of debris.

Adjusting the nozzle to create a wider path increases the volume (and thereby the “weight”) of water. Although the focused pressure is slightly decreased, the increased volume (or “weight) of the water along the wider path will effectively move debris forward.

Pressure blowers have a lower CFM (cubic feet per minute) air flow. This results in narrow surface contact requiring more blowers to dry effectively.

Pressure fans also create high pitched frequencies that make sound more difficult to control. This comes from choking air down to a tight space at the outlet.

Because there is limited “weight” behind the pressure, the force of the air flow quickly dissipates upon exit.

LEARN MORE about The Aerodry high-volume Axial Fan