The Online Pump Magazine


Affinity Laws

The affinity laws lay down the relationship between hydraulic characteristics and rotational speed of centrifugal pumps.

Specific cases can use the general rule as follows:

1st Model Law
1. Affinity Law

2nd Model Law
2. Affinity Law

3rd Model Law
3. Affinity Law

Q = flow
H = head
P = power input
N = speed
The indices relate to the respective speed.

The affinity laws are applicable to frictionless, incompressible flows. They are to be viewed as empirically suitable for technical application.

Multi-speed functions of small and medium size pumps are realised by changing the motor windings configurations to achieve stepped speed variations.

Also see:
Pump H-Q Curve

Subject area PUMP CURVE