Chapter 17 : Centrifugal and Axial-Flow Pumps

Example 17.1 Page No : 543

In [4]:
import math 
	
#Initialization of variables
Ns = 500.   #minimum practical specific speed
h = 900. 	#ft
Q = 1600. 	#gpm
	
#calculations
ne = Ns*h**(3./4) /math.sqrt(Q)
	
#Results
print "Minimum rotative speed  =  %d rpm"%(round(ne,-1))

#Initialization of variables
ne = 600. 
gpm = 1600.
Ns = 500.
Head = 900. 	#ft
	
#calculations
h = (ne*math.sqrt(gpm) /Ns)**(4./3)
n = Head/h
	
#Results
print "No. of stages  =  ",round(n,3)

Minimum rotative speed  =  2050 rpm
No. of stages  =   5.159

Example 17.2 Page No : 543

In [3]:
import math 
	
#Initialization of variables
ne = 600. 
gpm = 2000.
h = 150.
num = 2.
	
#calculations
ns = ne*math.sqrt(gpm) /h**(3./4)
gpm2 = num*gpm
h2 = num**2 *h
Ns = 2*ne*math.sqrt(gpm2) /h2**(3./4)
Ne2 = Ns*(h/2)**(3./4) /math.sqrt(gpm)
	
#Results
print "Specific speed in case1  =  %d "%(ns)
print "Flow rate in case 2  =  %d gpm"%(gpm2)
print " Head in case 2  =  %d ft"%(h2)
print " Specific speed in case 2  =  %d "%(Ns)
print " required operating speed in case 2  =  %.f rpm"%(Ne2)

Specific speed in case1  =  626 
Flow rate in case 2  =  4000 gpm
 Head in case 2  =  600 ft
 Specific speed in case 2  =  626 
 required operating speed in case 2  =  357 rpm

Example 17.3 Page No : 552

In [4]:
import math 
	
#Initialization of variables
ne = 600./2 
gpm = 1450.
h = 140.
NPSH = 10.4
	
#calculations
Ns = gpm*math.sqrt(ne) /h**(3./4)
sigmac = NPSH/h
zsmax = -3  	#ft
	
#Results
print "Sigma C for the pump  =  %.4f"%(sigmac)
print " Position of pump  =  %d ft"%(zsmax)

Sigma C for the pump  =  0.0743
 Position of pump  =  -3 ft

Example 17.4 Page No : 557

In [5]:
import math 
	
#Initialization of variables
ne = 600.
gpm = 84500.
h = 225.
f = 0.95
phie = 1.1
g = 32.2
	
#calculations
Ns = ne*math.sqrt(gpm) /h**(3./4)
u2 = phie*math.sqrt(2*g*h)
D = 153.2*phie*math.sqrt(h) /ne
D0 = 1.06*D*12 	#in
B = 0.155*D0*12 	#in
De = 0.6*D0
u0 = 1.06*u2
Vm2 = 0.15*u0
Area = 0.95*math.pi*D/144 *B
Q = Area*Vm2
	
#Results
print "Specific speed  = %d "%(round(Ns,-1))
print " Flow rate  =  %d cfs"%(Q)
print " Eye diameter  =  %.1f in"%(De)

# rounding off error

Specific speed  = 3000 
 Flow rate  =  183 cfs
 Eye diameter  =  32.2 in