A fan is a mechanical device for moving air or other gases. It uses the kinetic energy of the impellers to increase the volume and pressure of the air/gas stream which in turn moves them against the resistance caused by ducts, dampers and other components in a system.

Types of Fans

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 the table below.

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 (propeller, tubeaxial, vaneaxial).