I hope there is a simple answer to what is, I hope, a simple question.
When incorporating a fan in a Telcordia reliability prediction (General / Rotating Device / Other) there are three "types" available under issue 3: Blower Assembly, Equipment Fan and Fan Assembly. Under Issue 2 there were only two choices: Blower and Fan.
As I think I understand it a "Blower" is a centrifugal / snail / radial fan whereas "Fan" is an axial / propeller fan. Is there a more formal definition and does it depend on motor size or rotor speed? Also what differentiates an "Equipment Fan" from a "Fan Assembly"?
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.