Centrifugal Fans Named After Their Construction Or Design

Centrifugal fans displace air radially, thus diverting the direction of air by 90 degree. At a constant speed of fan, centrifugal fan will move constant volume of air and not constant mass of air. Hence it is called as constant volume fan. This can be achieved from centrifugal fans with different construction and design.

Forward curved fans
The impeller of the fan is fitted with blades curved forward in the direction of wheel rotation. Because of this forward curve, the fans are capable of accelerating air to a high velocity while rotating at a lower speed. They are less efficient than airfoil and backward inclined fans and have limited usage in industrial applications. Forward curved fans are ideal for low pressure applications such as domestic furnaces, ventilation and air conditioning systems.

Backward inclined fans
These are radial fans with backward curved blades that are flat and of single thickness. They can handle relatively medium to high volumes of airflow at high static pressures. These fans are typically known as “non-overloading” because the impeller has non-overloading characteristic and the changes in static pressure do not overload the motor. Backward inclined fans are slightly less efficient than airfoil fans and are used in high volume applications such as for heating, ventilation and air conditioning systems.

Double Inlet centrifugal fans
They are heavy duty fans and are customised for various industrial processes. They serve the purpose of providing large airflow in the industrial processes. It has two separate inlets and one common outlet. Inlet boxes are fitted with dampers to control the airflow.

Multistage centrifugal fans
Many industries have requirement of high pressure. The output is achieved by using two centrifugal fans in cascade. They have two impellers fitted on a single shaft. The airflow from first impeller is magnified by the second impeller. Chemical industry utilises multistage centrifugal fans for evaporation of chemical substances. It also finds application in other industries which require high pressures like cement, power plant and wood industry.

Radial blade fans
The impeller of radial blade fans consists of multiple equally spaced flat blades that are radial to the fan shaft. The wheel is paddle type and may or may not contain side rims. They are less efficient than other centrifugal fan types. They produce medium to high pressure and are well suited for material handling and in some moderate pressure industrial applications.

Airfoil blade fans
The blades of these fans contain airfoil blade shape which is hollow and backward-inclined. Their speciality is that they can handle large volume of air at low to moderate static pressure. They produce optimum efficiency and can handle large volumes of air in industrial applications, ventilation, air conditioning etc.

Radial tip fans
The blades of these fans are radial to the fan shaft but cupped in the direction of wheel rotation. They have compact design than airfoil and backward inclined fans and feature both clockwise and anti-clockwise rotation. Radial tip fans have moderate material handling capabilities in industrial processes but are more efficient than radial blade fans. They can handle wide variety of airstreams in industrial applications at moderate to high pressures. These fans are typically used for induced draft in boilers, in dust collection systems, and in other general ventilation applications.