1 CIVE 401 - HYDRAULIC ENGINEERING – PART II HYDROMACHINERY Pierre Julien Colorado State University Problems with ♦ and ♦♦ are considered moderate and those with ♦♦♦ are the longest and/or most difficult. In 2021, you solve the odd-numbered problems with ☺ PUMPS ☺ 1. ♦ English Units - Determine the power required to pump 2.5 cfs at 68°F from the lower to upper reservoir. Assume that the friction factor is f = 0.015, and sketch the HGL and EGL. [Ans. H = 104 ft, P = 29.5 HP]
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CIVE 401 - HYDRAULIC ENGINEERING PART II HYDROMACHINERY
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CIVE 401 - HYDRAULIC ENGINEERING – PART II
HYDROMACHINERY
Pierre Julien
Colorado State University
Problems with ♦ and ♦♦ are considered moderate and those with ♦♦♦ are the longest and/or most difficult.
In 2021, you solve the odd-numbered problems with ☺
PUMPS
☺ 1. ♦ English Units - Determine the power required to pump 2.5 cfs at 68°F from the lower to
upper reservoir. Assume that the friction factor is f = 0.015, and sketch the HGL and EGL.
[Ans. H = 104 ft, P = 29.5 HP]
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2. ♦ SI Units -What power must be supplied by the pump if water (T = 20°C) is pumped through a
200 mm diameter steel pipe from the lower tank to the upper one at a rate of 0.314 cms? Draw the
EGL and HGL. [hint: find f from the Moody diagram].
[Ans. ℎ𝑝 = 108𝑚, 𝑃 = 445 𝐻𝑃]
☺ 3. ♦♦ SI Units - At a flow rate of 0.25 m3/s, and head losses such that fL/D = 3.5, determine the
power required at the pump and plot the EGL and HGL.
[Ans. ℎ𝑝 = 56 𝑓𝑡, ℎ𝑓 = 7.3 𝑓𝑡, P= 56 HP]
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4. ♦♦ English Units - For the pump curves #1 to #3 in the class notes, look at conditions near
maximum efficiency. Estimate the specific speed and locate each pump on the classification
charts.
[Ans: #2, 𝑁𝑠 = 2,800]
☺ 5. ♦ English Units - What type of pump at N = 1,500 rpm should be used for a discharge of 12
cfs and head of 25 ft?
[Ans: mixed flow pump]
6. ♦♦♦ For the pump below, you burned the motor and want to replace it with a faster motor. What
is the maximum head that can be generated if the speed is increased to 1500 rpm? Also determine
the increase in discharge at a given head for the same condition. Finally, would this increase or
decrease the potential for cavitation, or NPSH? [hint: look at the definition of constant values of CH
and CQ]
[Ans. 50% increase in Q, and V]
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☺ 7. ♦♦ English Units - For the system below and the pump curve given, assume f = 0.02, and
neglect other minor losses. Determine the head losses as a function of discharge and plot on the
performance on the diagram below. Determine the discharge and head at the pump when the pipe
diameter is 16 inches. What type of pump would you recommend? If the NPSH is 8’ for the 16”
line, what is the maximum elevation Xmax for this pump. Repeat with a pipe diameter of 24 in.
[Ans. ℎ𝑓 = 0.24𝑄2, and Xmax = 4.4 ft in the 16-inch line]
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8. ♦♦ SI Units - Find the discharge under the conditions shown and the given pump characteristics.
If the motor is located at an elevation of 23 m, which elevation (propeller or motor) should be
considered for the NPSH calculation?
[Ans. ℎ𝑓 = 18𝑄2, and H = 2.5 m]
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PROBLEMS 9 and 10 MUST BE SOLVED
☺ 9. ♦♦♦ English units - Optimization Problem
In the following set-up, the pump brings Q =
0.125m3/s of water to an elevation H = 120 ft above
sea level in a L = 2,500 ft long pipe. The pump is set
to run 16 hours per day.
Your company (JJ Engineering) is asked to design
the pipe diameter (single value) and pump size. Your supervisor Jan tells you to assume f = 0.02
and neglect minor losses. Determine the flow velocity for various pipe diameters of 8”, 10”, 12”, etc.
A) Jan asks you to estimate the cost for each alternative based on a 2014 table of the cost for
galvanized iron pipe and pumps. The cost of pipes is 2” (6$/ft), 3” (10$/ft), 4” (25$/ft), 6” (35$/ft), 8”