PROBLEM 5:
Oil having a density of 833 kg/m 3 and a viscosity of 3.3 x 10 -3Pa.s is pumped from and open tank to a pressurized tank
held at 345 kPa gage. The oil is pumped from an inlet the side of the open tank through a line of commercial steel pipe
having an inside diameter of 0.07792 m at the rate of 3.494 x 10 -3 m3/s. The length of the straight pipe is 122 m, and
the pipe contains two elbows (90) and a globe valve half open. The level of the liquid in the open tank is 20 m above
the liquid level in the pressurized tank. The pump efficiency is 65% Calculate the kW power of the pump.
Given:
Lpipe = 122 m
Di = 0.07792 m [commercial steel type]
Q = 3.494 x 10-3 m3/s
( DL )
2 - 90 Standard Elbow Fittings
( DL )
Globe Valve half open
= 30
= 475
z = 20 m
65% pump efficiency
=
=
3.3 x 10 Pa s
833
kg
m3
P1 = 101.325 kPa
P2 = 101.325 + 345 kPa = 446.325 kPa
Find: Power (kW)
Solution:
N =
Dv
=
( 0.007792 m ) 0.732715082
m
kg
833 3
s
m
)(
3.3 x 10 Pa s
N , Pl> 4000,
B=
{ [(
A= 2.457 ln
L:
7
N
+ 0.27
16
) (
=
Turbulent Flow Regime, = 1
37530
14411.69747
16
) =4473164.191
16
1
0.9
37530
N
) =14411.69747
( D )
]} { [ (
= 2.457 ln
16
1
7
14411.697473
0.9
+0.27 ( 0.0006 )
Pipe = 122 m
90 Standard Elbow Fittings =
Globe valve half open =
= 161.3496 m
( DL )=( 30 )( 0.007792 m )=2.3376 m
( DL )=( 475 ) ( 0.007792m )=37.012 m
]}
=3.067762401 x 1019
m
=2070.708419
( DL )= 161.3496
0.007792 m
[( )
8
f F =2
N
12
1
12
( A+ B )
3
2
] [
8
=2
14411.69747
12
) + (3.067762401 x 10 + 4473164.191 )
19
3
2
1
12
=7.331237359 x 103
m
m 2
0.732715082
s2
s
L v2
J
=( 122 m)
+ 4 ( 7.331237359 x 103 ) ( 2070.7084193 )
=626.594
D 2 gc
kg
kg m
kg m
1
2 1
(1 )
2
Ns
Ns 2
W s = z
g
+4 f F
gc
626.594
J
1
x
=2.80785 kW
kg 0.65
(
(
9.81
)
)