Practice Problems on Pipe Flows
C. Wassgren, Purdue University
Page 1 of 23
Last Updated:
2010 Oct 15
pipe_02
A homeowner plans to pump water from a stream in their backyard to water their lawn.
A schematic of the pipe
system is shown in the figure.
Details of the system are given in the following table.
The design flow rate for the system is 2.5*10
-4
m
3
/s.
Item
Value
water density
1000 kg/m
3
water dynamic viscosity
1*10
-3
kg/(m.s)
inlet pipe length
2 m
inlet pipe diameter
2.5 cm
inlet pipe material
drawn tubing
hose length
two 15.25 m lengths
hose diameter
1.3 cm
hose roughness
smooth
pipe inlet loss coefficient
0.8
inlet pipe-to-pump coupling loss
coefficient
0.1
pump-to-hose coupling loss coefficient
0.2
hose-to-hose coupling loss coefficient
0.5
pressure drop across the sprinkler
210 kPa at 2.5*10
-4
m
3
/s flow rate
sprinkler nozzle exit diameter
4 mm
1.
What is the loss coefficient for the sprinkler at design conditions?
Base the sprinkler loss coefficient on the
velocity just upstream of the sprinkler.
K
sprinkler
= 118
2.
What is the friction factor for the hose?
hose
= 0.0244
3.
What is the velocity head, including the kinetic energy correction factor, at the sprinkler exit?
2
sprinkler
exit
20.2 m
2
V
g
For the next two questions, assume that the loss coefficient for the sprinkler is 100 and the friction factor for the
hose is 0.01.
4.
What is the total
minor
head loss in the system?
H
L
,minor
= 21.5 m
5.
What is the total
major
head loss in the system?
H
L
,major
= 10.4 m
For the next question, assume that the velocity head at the sprinkler exit, including the kinetic energy correction
factor, is 10 m and the total head loss is 10 m.
6.
What is the shaft head required to operate the system at the design flow rate?
H
S
= 55.1 m
For the next question, assume that the shaft head required to operate the system at the design flow rate is 100 m.
7.
What power must be supplied to the pump if the pump is 65% efficient?
into
pump
35 W
W
sprinkler
hose-to-hose coupling
pump
stream
re-entrant
pipe inlet
3 m
1 m
2 m of 2.5 cm
diameter drawn tubing
two 15.25 m lengths of 1.3
cm diameter garden hose
pump-to-hose coupling
inlet pipe-to-pump
coupling

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