Types of Drives
Centrifugal Fans vs Axial Fans
Centrifugal fans or blowers use one of seven types of wheels that are enclosed in a scroll shaped housing. The air enters the fan wheel through the housing inlet, turns 90 degrees and is accelerated radially and exits the fan housing.
Axial fans use a propeller, having two or more blades, to move air in an axial direction through a cylindrical housing or formed orifice panel.
The term “fan” is used to describe either a fan or blower. To make the proper fan selection, you must consider the following conditions the fan will be subjected to:
1.What is the air volume that will be required? This is rated in cubic feet of air per minute (CFM) or the metric equivalent, cubic meters per hour (M³/Hr).
2.What is the static pressure resistance through the complete system? This is rated in inches water gauge (in WG) or the metric equivalent, millimeters water gauge (mm WG).
Note: in WG or mm WG is the resistance to flow, or friction, caused by the air moving through a pipe or duct. Be sure to include other such as filters, dampers, heat ex-changers, etc.
3.What is the temperature of the air going through the fan?
4.What is the ambient air temperature outside the fan?
5.Will the air stream be clean, dry air? Will there be any corrosive substances in the air?
6.If the fan will be used to convey material, answer the following:
a. What is the material?
b. How much does the material weigh, in pounds per cubic foot?
c. How many pounds will you need to convey per minute or hour?
d. Is the material long and stringy or granular?
7.Will there be any moisture in the air stream?
8.What is the altitude where the fan will be operating?
9.Is anything going through the fan that could be explosive?
10.Does the location the fan will be operating in contain any explosive material, liquid or both?
