Axial fans consist of a fan shaft with fan blades attached around the shaft. Air travels along the axis of the fan and is blown out. These fans are not as common in the residential and commercial HVAC and Refrigeration fields and are more common in industrial ventilation type situations. The different types of axial fans are defined by their
Propeller: Propeller type axial fans consist of a propeller fan in fan housing. This fan, similar to all axial type fans is only suitable for lower pressures.
Tube Axial: The tube axial fan consists of a propeller fan placed in a tube. This type of fan is more efficient than the propeller fan and can handle higher pressures.
Vane Axial: The vane axial fan is a variation on the tube axial fan in which inlet vanes are provided on the fan to straighten the air and to increase the efficiency of the fan.
Centrifugal fans consist of a fan wheel, with blades (impellers) along the circumference of the wheel. Air enters the center of the fan wheel and the centrifugal force due to the spinning of the fan wheel, causes the air to increase in speed and creates a suction pressure at the inlet of the fan wheel. The air then flows out the edges of the fan wheel and follows the fan housing out. These fans are the most common in the HVAC and Refrigeration field. The different types of centrifugal fans are defined by the shape of the fan wheel impellers, relative to the axis rotation.
Forward Curved: Forward curved centrifugal fans have fan blades that are angled forward in the direction of the fan rotation. These fans are commonly used for lower pressures and are the least efficient of these centrifugal fans.
Backward inclined: Backward inclined centrifugal fans have fan wheel impellers that are angled backwards relative to the fan rotation direction. These fans are more efficient than the forward curved fans and are more commonly used at higher pressure
Airfoil: Airfoil fans are defined by the airfoil type fan blades, they resemble jet engine blades. These fans are the most efficient and can handle high pressures.