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JWCL344_ch07_230-264.qxd 8/2/10 8:44 PM Page 252

252 Chapter 7 Water Distribution Systems: Modeling and Computer Applications

• On the Efficiency tab, select the Multiple Efficiency Points option for the pump effi-
ciency. In the Efficiency Points table, add the efficiency data from the problem statement.
• In the Motor section, enter 90% for the motor efficiency.
• Close the Pump Definition tool and the pump dialog.
• The Energy Cost tool is used to calculate energy costs. From the Analysis drop-down
menu, select Energy Costs or click the icon button in the toolbar.
• Click the icon button to open the Energy Pricing field dialog.
• Create a New label “Energy Pricing-1” to enter the electricity cost. Enter one line in the
cost table. The Time from Start is 0.000, and the Energy Price is $0.10/kWh. Close the
Energy Pricing dialog to return to the Energy Cost window.
• Set the scenario to Chlorine Analysis then select “Energy Pricing-1” in the Energy
Pricing field located on the “Pumps” tab, then click the Compute button.

Answer
On the left panel of the Energy Cost window, highlight the Chlorine Analysis line. On the right
panel, select the Summary tab. For the 7-day simulation, the following data were calculated:
Pump energy used 4,030 kWh
Volume pumped 21,220 m 3
Pump cost USD 403.00
Daily cost USD 58.60

EXAMPLE 7.4 PIPE SIZING USING DARWIN DESIGNER
WaterGEMS can help size pipes and prepare project cost estimates. In this example, the Darwin
Designer with the Minimum Cost function is demonstrated.
Problem Statement
Prepare a minimal cost estimate for the pipe materials and installation portion of the project in
Example 7.2. The system pipes should be sized using a demand multiplier of 3.4 (peak flow factor)
with a calculated pressure for each junction between 170 and 550 kPa. In addition, the system
should supply to an industry located at junction 9 an additional 1,500 L/min with a minimum pres-
sure of 275 kPa. Use the cost data shown in Table 7.7.
Table 7.7 Pipe Material and Cost for Example 7.4

Pipe Material and Cost
Material Diameter (mm) Cost ($/m)
Ductile Iron 75 40.32
Ductile Iron 150 56.64
Ductile Iron 200 79.36
Ductile Iron 250 114.72
Ductile Iron 300 156.16
Ductile Iron 350 201.92

Do not consider the cost of the reservoir, tank, pump, or pipes P-12 and P-13.