It is desired to design a pump-piping system to keep a 1-million-gallon capacity water tank filled.
The plan is to use a modified (in size and speed) version of the model A centrifugal pump. Provided
is the test data for a small model of this pump: D = 5:45 in, ω = 1760 rpm, tested with water at
20C:
|
Q, gal/min |
0 |
5 |
10 |
15 |
20 |
25 |
30 |
35 |
40 |
45 |
50 |
55 |
60 |
|
H, ft |
28 |
28 |
29 |
29 |
28 |
28 |
27 |
26 |
25 |
23 |
21 |
18 |
15 |
|
Efficiency, % |
0 |
13 |
25 |
35 |
44 |
48 |
51 |
53 |
54 |
55 |
53 |
50 |
45 |
where Q is the volumetric flow rate and h = Δp/ρg is the centrifugal pump “head.”
The tank is to be filled daily with groundwater at 10C from an aquifer, which is 0.8 mi from the
tank and 150 ft lower than the tank. Estimated daily water use is 1.5 million gal/day. Filling time
should not exceed 8 h per day. The piping system should have four “butterfly” valves with variable
openings, 10 90degree elbows, and galvanized-iron pipe of a size to be selected in the design. The design
should be economical both in capital costs and operating expense. Use the following cost estimates
for system components:
Pump and motor $3500 plus $1500 per inch of impeller size
Pump speed Between 900 and 1800 rpm
Valves $300 + $200 per inch of pipe size
Elbows $50 plus $50 per inch of pipe size
Pipes $1 per inch of diameter per foot of length
Electricity cost 10¢ per kilowatt-hour
Select the combination of pipe size, pump impeller size, and speed for this task (using the data
provided), that yields the lowest cost after 20 years of operation.
1. Introduction
2. Problem description – Describe the proposed problem and design objectives.
3. Design process – Present the logical steps and equations used to perform your analysis.
4. Design description – Give a detailed cost analysis of your design. Show what the effect of
impeller diameter, flow rate, and speed is on both overhead cost and operational costs.
5. Summary
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