Fan and blower selection

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)
In axial flow, air enters and leaves the fan with no change in direction (ppropeller, tubeaxial, vaneaxial )

TABLE 5.2 FAN EFFICIENCIES

Type of fan                                 Peak Efficiency Range

Centrifugal Fans

Airfoil, backward                                 79–83
curved/inclined
Modified radial                                    72–79
Radial                                                    69–75
Pressure blower                                     58–68
Forward curved                                    60–65
Axial fan
Vane axial                                                78–85
Tube axial                                               67–72
Propeller                                                45–50