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 HazenWilliams or DarcyWeisbach equations.
For PVC pipe, use a HazenWilliams “roughness” factor of C = 150.
Or, for DarcyWeisbach, 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:
HazenW 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: HazenWilliams equation) ...
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This note was uploaded on 03/01/2012 for the course BIE 6110 taught by Professor Sprinkle during the Fall '03 term at Utah State University.
 Fall '03
 Sprinkle

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