Being able to read and understand a fan diagram is important to understanding how a fan will behave in a particular system.
The left vertical scale shows total pressure and the horizontal scale shows volume flow.
Plotted in the diagram are the system curve (brown) and fan curves (red, blue and one black).
The operating point is marked with the green lines that go out from the respective axis.
pt (Blue): Shows the total pressure increase from the fan at a certain volume flow
The total pressure is the sum of pst and pd2.
pst (Red): Shows the static pressure of the fan at a certain volume flow.
The static pressure is the sum of the external pressure demand in the system incl. all resistance and losses such as friction.
pd2 (Black): Shows the dynamic pressure of the fan at a certain volume flow.
The dynamic pressure is the kinetic energy in the volume flow.
System Curve (brown): Shows the system pressure drop for different volume flows
Operating point (Green): Shows the point where the system curve and the fan curve cross.
It is at this point that the fan will work.
The lower green line shows the operating point without dynamic losses.
In combination with the fan diagram, an impeller power diagram is shown:
This diagram shows the power required at a certain volume flow.
In the diagram, the operating point is marked with green lines in the same way as in the fan diagram and thus shows the power requirement we have at our operating point.
This data is the basis for choosing the right motor size.
