1-25 - BIE 5110/6110 Sprinkle & Trickle Irrigation...

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Unformatted text preview: BIE 5110/6110 Sprinkle & Trickle Irrigation Fall Semester, 2004 Assignment #2 (100 pts) Due: 29 Sep 04 Given: A solution for the economic selection of pipe sizes is needed. The solution is to be based on the following data: interest rate, i = 2.4% inflation rate, e = 0.1% useful system life, n = 22 years area irrigated, A = 58 ha gross annual depth, d = 890 mm/year maximum system capacity, Q = 210 lps motor efficiency, Em = 94% pump efficiency, Ep = 88% avg cost of electricity for pumping = 0.06104 $/kWh purchase cost of PVC pipe: Size (inches) 6 8 10 12 14 16 18 O.D. I.D. Wall Price (inches) (inches) (inch) ($/20 ft) 6.625 6.031 0.297 35.10 8.625 7.943 0.341 53.22 10.750 9.976 0.387 75.81 12.750 11.890 0.430 98.08 14.000 13.072 0.464 116.95 16.000 14.940 0.530 154.33 18.000 16.809 0.595 198.39 In the above table: “O.D.” is outside diameter; “I.D.” is inside diameter; and “Wall” is the pipe wall thickness Required: • • • • • • Determine the cutoff flow rate values for each adjacent pair of pipe sizes (you are not required to graph the pipe selection chart) The solution is to include the PVC pipe with nominal sizes 6, 8, 10, 12, 14, 16, and 18 inches, as shown above. You can use either the Hazen-Williams or Darcy-Weisbach equations. For PVC pipe, use a Hazen-Williams “roughness” factor of C = 150. Or, for Darcy-Weisbach, use the Blasius equation for smooth pipe. Assume that MAC is negligible. Solution: BIE 5110/6110 Economic Pipe Selection Method Assignment #2, Fall 2004 Given data: useful life: interest rate: 22 years 0.024 per year inflation: area: depth: capacity: 0.001 58 0.89 210 per year ha m/year lps Pipe purchase prices: Size (inches) 6 8 10 12 14 16 18 O.D. (inches) 6.625 8.625 10.750 12.750 14.000 16.000 18.000 I.D. (inches) 6.031 7.943 9.976 11.890 13.072 14.940 16.809 Capital Recovery Factor: CRF= Wall Price (inch) ($/20 ft) 0.297 35.10 0.341 53.22 0.387 75.81 0.430 98.08 0.464 116.95 0.530 154.33 0.595 198.39 0.0590 Uniform annual pipe cost: Size (inches) 6 8 10 12 14 16 18 UAC ($/20 ft/yr) ($/100 ft/yr) 2.07 10.36 3.14 15.71 4.48 22.38 5.79 28.95 6.90 34.52 9.11 45.56 11.71 58.56 Operating hours per year: Ot= 683 hrs/year Present annual energy cost: E= 50.38 $/kW /yr Equivalent annual energy cost: EAE= E'= 1.0096 50.87 $/kW /yr (MAC said to be negligible) motor efficiency: pump efficiency: electricity: Hazen-W illiams: 0.94 0.88 0.06104 $/kW h 150 C factor Difference in WHP between adjacent pipe sizes: Sizes (inches) 6 and 8 8 and 10 10 and 12 12 and 14 14 and 16 16 and 18 delta WHP kW/100 ft 0.10515 0.13109 0.12923 0.10950 0.21691 0.25567 Difference in J between adjacent pipe sizes: Sizes (inches) 6 and 8 8 and 10 10 and 12 12 and 14 14 and 16 16 and 18 delta J m/100 m 0.16756 0.20889 0.20593 0.17449 0.34566 0.40743 (note: m/100 m is equivalent to ft/100 ft) (however, must use 102 for lps or 3,960 for gpm) Threshold flow rate between adjacent pipe sizes: Sizes (inches) 6 and 8 8 and 10 10 and 12 12 and 14 14 and 16 16 and 18 Section flow rate lps gpm 11.2 177.4 27.4 434.3 53.8 852.8 99.1 1,570.0 160.0 2,535.6 260.9 4,134.8 (note: Hazen-Williams equation) ...
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