# 978-0134292380 Chapter 5 Part 2

Document Type

Test Prep

Book Title

Fundamentals of Hydraulic Engineering Systems 5th Edition

Authors

A. Osman H. Akan, Ned H. C. Hwang, Robert J. Houghtalen

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49

6. As field engineer on a construction project, you need to pump water from a river (water

surface elevation of 382.5 meters) to a reservoir (water surface elevation 400 meters). The

pump available to you has the pump characteristics tabulated below. The pipeline will be 400

meters long, and you would like to use a 4-cm-diameter ductile iron pipe (f = 0.020). What

flow rate can be expected if minor losses are ignored.

Q

Hp

(m3/hr)

Pump(m)

52.2

4

51.3

8

49.5

12

46.8

16

43.1

25.4

49.5

49.5

12

46.8

3.33

89.1

16

43.1

4.44

7. As field engineer on a construction project, you need to pump water from a river (water

surface elevation of 362 meters) to a supply reservoir (water surface elevation 400 meters).

The available pump has the performance characteristics tabulated below. The discharge

pipeline is a 5-cm-diameter ductile iron pipe (f = 0.018) and is 400 meters long. You have

performed the calculations in the table below and you note that the likely flow rate is 8 m3/hr,

which is too low. To increase the flow rate, you may have access to an identical pump and

can hook it up in parallel to the existing pump, sending the increased flow through the same

pipeline. What is the flow rate that can be expected if minor losses are ignored?

Q

Hp

Q

V

hf

HSH

(m3/hr)

Pump(m)

(x10-3 m3/s)

(m/s)

(m)

(m)

0

51.6

0.00

0.00

0.0

38.0

4

1.11

40.4

47.5

2.22

1.13

9.4

47.4

12

40.8

3.33

1.70

59.2

16

30.1

4.44

2.26

75.4

50

84.9

123

16

30.1

32

8.88

4.53

151

8. Each of the three pipe flows is required in the branching pipe system depicted below. Fill in

the blanks of the solution table provided which eventually leads to the graphical solution.

The reservoir water elevations are: EA = 110 ft, EB = 120 ft, and EC = 140 ft.

Pipe Characteristics

Pipe

L (ft)

D (ft)

K

m

1

10000

2

0.0512

2

2

15000

2

0.0768

2

3

5000

2.5

0.0103

2

Q

Hp, ft

hf3

Net Hp*

HSH1

HSH2

(cfs)

(pump)

(ft)

(ft)

(ft)

(ft)

0.0

80.0

10.0

78.5

20.0

74.0

30.0

66.5

P

EA

EB

Hs1

EC

Hs2

Pipe 1

Pipe 2

Pipe 3

51

9. The branching pipeline shown below contains a pump and three pipes. The characteristics of

the pipes and pump are tabulated below. Pipes 1 and 2 contain partially closed valves. If a

flow of 10 cfs is required to flow into Reservoir B and 10 cfs into Reservoir C, determine the

head loss in each valve. The reservoir water elevations are: EA = 100 ft, EB = 128 ft, and EC =

131 ft.

Pipe Characteristics

Pipe

L (ft)

D (ft)

f

1

1000

1.5

0.02

2

1000

1.5

0.02

3

1000

1.5

0.02

Q

Hp

(cfs)

Pump (ft)

0

100

5

96

10

90

15

80

20

66

25

48

30

24

P

EA

EB

Hs1

EC

Hs2

Pipe 1

Pipe 2

Pipe 3

52

10. A pump is installed in a 400-ft-long, 1.0-ft-diameter (ductile-iron) pipeline to deliver water

(68°F) from a supply reservoir to an elevated tank. The design discharge is 4.0 ft3/sec. The

pump overcomes an elevation difference between the reservoir and the tank of 150 ft. The

suction line is 35 ft of the 400-ft length. Minor loss coefficients in the suction line add up to

3.7. If the pump is installed 3 to 10 ft above the supply reservoir (depending on fluctuations

in the water level), will the installation be susceptible to cavitation? The net positive suction

head of the pump is rated at 20 ft.

53

11. A pump is installed in a 100-m pipeline to raise water (20° C) from reservoir A with a water

surface elevation of 145m to reservoir B with a water surface elevation of 165m. The 80-cm-

diameter, concrete (rough) pipe has a design discharge of 2.06 m3/sec. The suction line is 15

m of the 100-m length with a square-edged entrance condition. If the pump has a cavitation

parameter of 0.10, determine the allowable height the pump can be placed above the supply

reservoir to avoid cavitation. Assume completely turbulent flow in the pipeline.

12. Two geometrically-similar, centrifugal pumps are operated at the same efficiency. Pump A

operates at 450 rpm, and delivers 2.4 m3/sec against a 22-m head. The scale model (pump B)

is one fourth the size with corresponding dimensions and operates at four times the speed.

What is the discharge of pump B when it is delivering water against the same head? If the

efficiency of pump A is 0.80, determine the power input required of pump B.

13. A pump with a specific speed based on unit discharge of 50 has an impeller diameter of 72

cm, an operational speed of 1720 rpm, and an efficiency of 80%. Determine the pump head

and shaft power required to operate the pump if the discharge is 12.7 m3/sec.

54

14. A pump is required to deliver 0.125 m3/sec of water (β0˚C) from reservoir A to reservoir B

(water surface elevations of 385.7m and 402.5m, respectively). The pipeline (avg. concrete)

is 300 m long with a diameter of 0.20 m and contains five bends (R/D = 6) and two gate

valves. Determine the appropriate pump from Figure 5.23 and 5.24 and the pump’s working

conditions. Assume complete turbulence.

15. A pump, whose characteristic curve

is depicted is placed in a 6-in. dia.

pipeline, 850 ft long (f = 0.020) to

raise water from one reservoir to

another. The water surface elevation

difference between the reservoirs

fluctuates from 136 ft to 58 ft based

on water demands. Determine the

water surface elevation difference

between the supply and receiving

reservoirs when the pump is

delivering flow rates of 400 gpm,

600 gpm, and 800 gpm.

43

For each Q, find Hp from the pump characteristic curve. Then substitute the Q and Hp

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