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34 TRG-TRC013-EN
notes
period two
Fan Types
The application range of the airfoil fan is from approximately 50 to 85 percent
wide-open airflow. This is a narrower application range than either the FC or BI
fan. The reason is that the airfoil fan surges at a greater percentage of
wide-open airflow, placing the surge line farther to the right on the fan curve.
Static efficiencies as high as 86 percent can be achieved with airfoil fans.
Because surge occurs at a higher airflow, the magnitude of the surge
characteristics of the airfoil fan is greater than that of the FC and flat-bladed BI
fans.
A variation of the airfoil fan is a plug (or plenum) fan. This type of fan consists
of an unhoused fan wheel with airfoil fan blades and an inlet cone. The fan
wheel pressurizes the plenum surrounding the fan, allowing the air to discharge
in multiple directions. This fan can save space by eliminating turns in the
ductwork and allowing multiple discharge ducts in different directions.
50%
50%
85%
85%
airflow
airflow
static pressure
static pressure
Airfoil Fan
application
application
range
range
static efficiency
static efficiency
80 to 86%
80 to 86%
Figure 51
Plug (or Plenum) Fan
fan wheel
fan wheel
inlet cone
inlet cone
plenum
plenum
Figure 52