EQ_pumpstation_npshr(): Calculate the required Net Positive Suction Head (NPSH) of a pumping system

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Calculate the required Net Positive Suction Head (NPSH) of a pumping system.

©WETpython, 2015

\begin{equation} NPSH_r = \frac{P_{atm}}{\gamma} - \frac{P_v}{\gamma} - (Z_e - Z_r) - f \times L_s - \sum K \times \frac{U^2}{2\times g} \end{equation} Where,

$\frac{P_{atm}}{\gamma}$, atmospheric pressure, m

$ \frac{P_v}{\gamma}$, vapour pressure at a certain temperature, m;

$ Z_e$, level of pump inlet, m;

$ Z_r$, uptake reservoir water level, m;

$ f \times L_s $, friction loss in suction pipe, m;

$\sum K \times \frac{U^2}{2\times g}$, sum of minor losses in suction pipe.

Module: Equiment

Function: EQ_pumpstation_npshr(zr1,ze,q,t,s,ds,ns,sumks,ls, patm)

Definition of variables:

zr1,upstream reservoir water level, m;
ze, level of the inlet of the pump, m;
q , pumped flow, m3/s;
t , water temperature, oC;
s, water salinity, g/kg;
ds, suction pipe diameter, m;
ns, suction pipe Manning coefficient, m;
sumks, sum of the minor losses K factor in suction pipe;
ls, suction pipe length, m.

Sample code:

from Equipment import *

zr1 = 20.0 #upstream reservoir water level, m
ze = 25.0 #donstream reservoir water level, m
q = 0.1 #pumped flow, m3/s
t = 25 # temperature, oC
s = 2.5 #water salinity, g/kg
ds = 0.3 #suction pipe diameter, m
ns = 0.013 # suction pipe Manning coefficient, m
sumks = 5.0 # sum of the minor losses K factor in suction pipe
ls = 10.0 # suction pipe length, m
patm = 101325 # local atmospheric pressure, Pa

npshr = EQ_pumpstation_npshr(zr1,ze,q,t,s,ds,ns,sumks,ls, patm)

print ("NPSHr:", npshr,"m")

Result:

NPSHr: 4.36776466992 m