Difference between Fans, Blowers and Compressors

  • Introduction

Fans and blowers provide air for ventilation and industrial process requirements. Fans generate a pressure to move air (or gases) against a resistance caused by ducts, dampers, or other components in a fan system. The fan rotor receives energy from a rotating shaft and transmits it to the air.


Difference between Fans, Blowers and Compressors



Fans,  blowers and compressors are differentiated by the method used to move the air, and by the system pressure, they must operate against. As per American  Society of Mechanical Engineers (ASME) the specific ratio – the ratio of the discharge pressure over the suction pressure – is used for defining the fans, blowers, and compressors (see Table 5.1).


5.2 Fan Types

Table 5.1 Differences Between Fans, Blower And Compressor





Specific Ratio


Pressure rise (mmWg)




Up to 1.11






1.11 to 1.20


1136 – 2066




more than 1.20




Fan and blower selection depends on the volume flow rate, pressure, type of material handled, space limitations, and efficiency. Fan efficiencies differ from design to design and also by types. Typical ranges of fan efficiencies are given in Table 5.2.


Fans fall into two general categories: centrifugal flow and axial flow.


In centrifugal flow, airflow changes direction twice – once when entering and second when leaving (forward curved, backward curved or inclined, radial) (see Figure 5.1).


In axial flow, air enters and leaves the fan with no change in direction (propeller, tube axial, vane axial) (see below table).


Fan Efficiencies
Type of fan Peak Efficiency


Centrifugal Fan
Airfoil, backward curved/inclined 79-83
Modified radial 72-79
Radial 69-75
Pressure Blower 58-68
Forward curved 60-65
Axial fan
Vane axial 78-85
Tubeaxial 67-72
Propeller 45-50

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