There are three basic types of fans.
1) Propeller or axial fans which are used when you have high flow rates and low pressure requirements.
a) Axial fans come in many configurations like tube axial, vane axial, orifice fans, panel fans to name a few.
b) They all have a propeller in them and use aerodynamic lift to create flow and pressure.
c) Peak Eficiency Specific speed range 1.5 to 8 with a specific diameter range 1 to 2.5
2) Mixedflow fans which are used when you have a medium flow rate and pressure requirement.
a) Mixed flow fans have a axial inlet and outlet
b) They use a centrifugal force impeller to generate flow and pressure.
c) Peak Efficiency Specific Speed range 1 to 5 with a specific diameter range 1 to 3.5
d) Mixflow fans are often the most efficient configurtion
3) Blower or Centrifugal fans are used when you have a low flow rate and a high pressure requirement.
a) Centrifugal fans come in three different blade configurations. Forward curved blades, backwardly inclined blades, and radial blades.
b) They all use centrifugal force to generate flow and pressure.
c) Peak Efficiency Specific Speed range 0.5 to 4 with a specific diameter range 1.5 to 9
The best way to determine which fan/blower is best suited to your application is to calaulate the Specific Speed and Specific Diameter. Using this approach will insure you have the most efficient air moving device.
Any good fan engineering handbook should have the formulas and a curve showing Specific speed and diameter.
