Suction coefficient
The suction coefficient (S) introduced by Pfleiderer – but no longer used – is a characteristic coefficient for the evaluation of the net positive suction head (NPSH) of a centrifugal pump's impeller.
S is defined as:
The suction coefficient for axial flow impellers is approx. 2.5 and for radial impellers approx. 3.0. Special designs can achieve much higher suction coefficients.
In accordance with international standards, the suction specific speed nss is used nowadays to describe the suction characteristics of centrifugal pumps.
