Dust Control Handbook for Industrial Minerals Mining and Processing

Fan TypesThere are two basic types of fans: axial-flow fans and centrifugal fans. There are also other fandesigns that use or combine the concepts of axial or centrifugal flow; these are axial-centrifugalfans and roof ventilators. Again, the selection of the fan type is based upon the requirements ofthe ventilation system design.Axial-Flow FansThe axial-flow fan category includes propeller fans, tubeaxial fans, vaneaxial fans, and two-stageaxial-flow fans. Axial flow fans move the air in a direction that is "axial" or parallel to the axisof rotation of the fan. Propeller fans are the most common type. They are generally mounted inthe wall of the building near a heat source to exhaust the hot air into the outside atmosphere(Figure 1.28). They can have different drive configurations, being either direct drive or beltdrive. The wall-mounted fans can also be constructed with shutters that close when the fan isturned off. Propeller fans are designed to move large volumes of air at low static pressures[Bleier 1998].Figure 1.28. Wall-mounted propeller fan.Tubeaxial fans are used for exhausting air from an inlet duct (Figure 1.29, left). They consist ofa fan with many blades in a cylindrical housing. The blades are generally shaped as an airfoil tohelp with air movement. The hub diameter can be 30 to 50 percent of the blade outside diameter[Bleier 1998]. The housing is connected to the inlet duct and also contains the motor support.These fans are used in conditions that require moderate static pressures (higher than thoserequired for propeller fans).Fundamentals of Dust Collection Systems 53