Effects of Fan Speed
The speed of the fan (RPM) can be determined by the initial selection of the fan or by a fan control signal. Changing the speed of the fan will affect the air volume, the air pressure, the power consumed, and the acoustic noise produced by the fan. These relationships are described by what are called the "fan affinity laws".
Fan Affinity Laws
The volume of air moved by the fan is proportional to the speed of the fan.
CFM α RPM
i.e. 3 x RPM produces 3 x CFM
The pressure of air from the fan is proportional to the square of the speed of the fan.
Air pressure α RPM2
i.e. 3 x RPM produces 9 x pressure