Centrifugal fans, often called as blowers, are special type of industrial fans that are ideal for high pressure applications in several process industries and air pollution systems. Centrifugal fans increase the pressure of an incoming airstream by impellers, a series of blades mounted on a circular hub, which in turn accelerates air radially and alters the direction of the outward flowing air, usually by 90°. As centrifugal fans are constant volume devices that create steadier flow of air than axial fans, they are most widely used in various industrial processes such as in transporting air/gas and material handling.

1. Centrifugal Fans - Basic types and their
characteristics

2. Centrifugal fans, often called as blowers, are special type of industrial
fans that are ideal for high pressure applications in several process
industries and air pollution systems. Centrifugal fans increase the
pressure of an incoming airstream by impellers, a series of blades
mounted on a circular hub, which in turn accelerates air radially and alters
the direction of the outward flowing air, usually by 90°. As centrifugal fans
are constant volume devices that create steadier flow of air than axial
fans, they are most widely used in various industrial processes such as in
transporting air/gas and material handling.

3. Centrifugal fans are broadly divided into six basic types based on the
blade configuration. Each type of centrifugal fan has its own application
range and limited ability to perform in the industrial processes.
Some of the basic characteristics of centrifugal fan types are:

4. • Forward curved fans
> The forward curved centrifugal fans are also called as 'squirrel cage'
fans because the wheel type used in this fan is of squirrel cage wheel.
The impeller has forward blades which are relatively smaller, curved in
direction of wheel rotation.
> The delicate construction of the impeller, shaft, bearings, and housing
of forward curved fans limit its suitability in industrial applications. These
fans are ideal for low speed and low pressure applications such as in
domestic furnaces, central station units, packaged air conditioning etc.

5. • Backward inclined fans
> The backward inclined centrifugal fans offer three standard blade types
– flat single thickness, curved single thickness and curved airfoil. The
blades are generally heavier and larger than forward curved and move
away from the direction of wheel rotation. They produce relatively medium
to high airflow at static pressures.
> These fans produce highest operating speeds and are found to be more
efficient than the other types of centrifugal fans. The backward inclined
fans are typically used in low pressure, high volume applications such as
heating, ventilation and air conditioning systems.

6. • Radial blade fans
> Radial blade centrifugal fans also called as paddle wheel fans, consists
of an impeller with multiple equally spaced flat blades that are extending
perpendicular to the direction of wheel rotation. The wheel is a paddle
type wheel which may or may not contain side rims and the blades are
comparatively heavier, deeper and narrower than forward and backward
inclined blades.
> They produce medium to high pressure and moves relatively a higher
mass or volume of fluid. Radial blade types are well suited for material
handling and in some moderate pressure industrial applications.

7. • Airfoil blade fans
> Airfoil blade fans have hollow backward inclined blades that are
suitable to handle large volumes of clean air at low to moderate static
pressures. These fans produce optimum efficiency and run at greater
speed than the backward inclined fans.
> As they can handle large volumes of air, these fans are extensively
used in forced and induced draft fans that are suitable for broad
operating ranges in industrial applications, HVAC systems, air pollution
control, drying & filtration, and other industrial processes.

8. • Radial tip fans
> The blades of radial tip centrifugal fans have backward curved
configuration but cupped in the direction of the wheel rotation. The
velocity produced by the Radial tip fan is same as that of backward
inclined wheel to move the given mass or volume of air. These fans have
compact design than airfoil and backward curved fans and are ideal for
high-volume flow rate applications where the pressure requirement is
also relatively high.
> Radial tip fans have moderate material handling capabilities but are
more efficient than radial blade fans. They are generally used in dust
collection systems and general ventilation applications.

9. • Inline centrifugal fans
> The inline centrifugal fans have rugged construction with backward
inclined type wheels enclosed in a tube-axial casing. These are
medium duty fans with straight through airflow.
> When compared to radial inclined type fans the inline centrifugal fans
are less efficient and are used in low pressure air system requirements
like heating and ventilating.

10. Based on the specific requirements of airflow rate, volume, pressure
and efficiency, centrifugal fans of various types are designed to serve
the needs of diverse industrial applications.

11. Reitz India has set a benchmark to deliver high quality fans for heavy
duty industries which can work at precise operating conditions like high
temperatures and pressures. Reitz offer idealistic centrifugal fan and
centrifugal blower design that can be used in all large scale process
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