STUTTGART CENTRIFUGAL FAN

Centrifugal fans, also known as "squirrel cage" or "utility" fans, have an entirely different design. Instead of passing straight through, the air makes a 90-degree-angle turn as it travels from the inlet to the outlet and is "thrown" from the blade tips.

Centrifugal fans have more mass farther from the axle, which requires more starting torque, but they're generally quieter than axial fans.

There are several arrangements of fan blades for centrifugal impellers. The highest-efficiency centrifugal fans use airfoil or backward-curved impeller blades (see Figure 2). Airfoil blades are curved backward and have an airfoil shape (similar to a cross section of an airplane wing), while backward-curved blades are of a single thickness of metal.

Straight radial fan blades are used mostly in industrial applications. The main advantage of radial blades is that they permit the passage of foreign objects in the air stream such as sawdust, metal filings, and other debris. They have no advantages for HVAC use, however, and should not be used for handling ventilation air in buildings.

Forward-curved fan blades have low efficiency and are typically used to move high volume against low pressure in applications such as window air conditioners and hotel unitary packages.

Figure 2: Centrifugal fan impeller blades


Source: Platts