Available NPSH in turbine (Net Positive Suction Head)

Description

In a hydraulic circuit, net positive suction head (NPSH) may refer to one of two quantities in the analysis of cavitation:
1. The Available NPSH (NPSHA): a measure of how close the fluid at a given point is to boiling, and so to cavitation.
2. The Required NPSH (NPSHR): the head value at a specific point (e.g. the inlet of a pump) required to keep the fluid from cavitating.
NPSH is particularly relevant inside centrifugal pumps and turbines, which are parts of a hydraulic system that are most vulnerable to cavitation.
The calculation of NPSH in a reaction turbine is is based on the fact that the cavitation will first occur at the outlet of the impeller, at the entrance of the draft tube.

Related formulas

Variables

NPSHAvailable NPSH in a turbine (m)
p0Total pressure at the lower free surface (m-1*kg*s-2)
ρDensity of the fluid (kg/m3)
gStandard gravity
pvPressure of vapor (m-1*kg*s-2)
zeElevation of the tube entrance (m)
z0Elevation of the lower free surface (m)
hfTurbines minor losses (m)