1 / 153

Design Irrigation System II

Design Irrigation System II. Asher Azenkot. Local Head Losses. The local head loss due to a local disturbance in water flow is proportional to the head velocity. K - Coefficient. Hydraulic Valve Local Head Loss. Filter Local Head Loss. Metzer drip line.

jbrittany
Télécharger la présentation

Design Irrigation System II

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Design Irrigation System II Asher Azenkot

  2. Local Head Losses The local head loss due to a local disturbance in water flow is proportional to the head velocity. K - Coefficient

  3. Hydraulic Valve Local Head Loss

  4. Filter Local Head Loss

  5. Metzer drip line Water flow velocity reduced gradually along the lateral pipe

  6. Local head loss in “head connector” m m3/h

  7. Local head loss Flow rate Local head loss m

  8. Example: A 12" valve (K = 2.5) is installed in 1,250 meters long pipe (12” and C = 130). What is the total head loss due to the valve and the pipe when the water flow rate is = 100, 200 and 400 m3/h. The pipe cross section area is:

  9. Continue:

  10. Continue: If an 8" valve is replaced the 12", what will be the new total head loss?

  11. Lateral Pipes A lateral pipe is characterized by a continuous decline in water discharge along the pipe. The flow rate starts at Qu (m3/h) at the upstream end and ends up with a q1 (m3/h) downstream. (Lateral pipe is abide by: 1. A same size of pipe, 2. even distance between outlets, 3. a same outlet (sprinkler or emitter) flow rate. The calculation of the head loss is done in two steps: The head loss is calculated by assuming the pipe is plain The outcome is multiplied by the coefficient F Qu = n*q 3q 2q q D Sl 95 m

  12. Coefficient F 1. F1 to be used when the distance from the lateral inlet to the first outlet is Sl meters. 2. F2 to be used when the first outlet is near the lateral inlet. 3. F3 to be used when the distance from the lateral inlet to the first outlet is Sl/2 meters.

  13. Characteristics of a Lateral pipe • The sprinkler pressure along the lateral pipe decline faster along the first 40% of the length than afterwards (figure 2). • The sprinkler flow rate along the lateral pipe declines faster along the first 40% of the length (figure 1). • The location of the sprinkler (or emitter) with the average pressure and flow rate is 40% away from the lateral’s inlet. • Three quarter of the lateral head loss takes place along the first two fifth sections (40%).

  14. Fig. 1: Flow rate reduction in a plain pipe and in a lateral with sprinklers.

  15. Fig. 2: Head loss and percent of head loss

  16. Head loss Calculation Along lateral • Select a suitable sprinkler or emitter with a required Hs, qs and sl from a catalogue (figure 3). • The number of sprinklers (n) along the lateral is determined by (L/sl). • The discharge rate at the lateral inlet is determined by (Qu = n x qs ). • The lateral diameter (D) should comply with maximum head loss of 20%. • The head loss along a lateral (Qu, q, D and L) is computed by: • Assuming the lateral pipe is plain and. • The outcome is multiplied by F factor.

  17. Fig. 3 - Naan 233

  18. Head loss in drip lateral pipe • A modified Hazen-Williams head loss equation: HL= head loss along a lateral drip line L = lateral length (m) D = internal diameter (m) N = number of emitters q = average emitter flow rate (m3/h) C = Hazen-Williams coefficient (130 - 120 forpolyethylene pipe with ID < 16 mm) F = 0.37 for more than 20 emitters

  19. Hydro P.C. & Hydro P.C.N.D - 1.2* L/H MAXIMUM RECOMMENDED DRIPLINE LENGTH (m)PIPE DIAMETER -16/13.8 (OD/ID)

  20. Number Of Mamkad spinklers

  21. Mamkad mini-sprinkler nozzles

  22. Example: A flat field, 360 x 360 m, is irrigated with a hand moved aluminum lateral pipe (C = 140). The water source to the lateral pipe is from a sub-main, which crosses the center of the field. The selected sprinklers are Naan 233/92 with a nozzle size of 4.5 mm, pressure of 25 m (hs) and flow rate (qs) of 1.44 m3/hr. The space between the sprinklers is 12 meters apart, and the location of the first sprinkler is 6 meters away from lateral inlet. The riser height is 0.8 m and diameter of 3/4".

  23. Answer: lateral • 360 m • Submain The number of sprinklers on the lateral is The length of the lateral (l) is l = (14 sprinkler x 12 m apart) + 6 m = 174 meters

  24. Continue • The inlet flow rate of the lateral is • Qu = 15 (sprinklers) x 1.44 m3/h = 21.6 m3/h • The maximum allowed head loss (20%) throughout the field is For a plain 2" aluminum pipe - the hydraulic gradient out of Hazen Williams is: J = 188.9 ‰

  25. Continue: The head loss in a 2" (plain) aluminum pipe is as follows: The F factor for 15 sprinklers is F15 = 0.363 • For a 3" aluminum pipe - the hydraulic gradient out of a table or ruler is: J = 26.2‰

  26. Continue: The head loss in a 3" (plain) aluminum pipe is as follows: • The F factor for 15 sprinklers is F15 = 0.363 The difference 5 - 1.66 = 3.34 meters head loss which will be used as the head loss for the sub-main pipe.

  27. A Lateral Inlet Pressure P = ? 3q 2q D Sl Qu = n*q

  28. A Lateral Inlet Pressure The pressure head at the lateral inlet (hu) is determined by: hu - lateral inlet pressure head hs - pressure head of selected sprinkler hf - head loss along lateral riser–the length (height) of the riser - local head loss (incurred between laleral pipe and sprinkler)

  29. Local head loss Flow rate Local head loss m

  30. Example: Following the previous example, what is the inlet pressure? hf = 1.66 meters riser height = 0.8 meters hs = 25 meters

  31. Inlet pressure in case of a Lateral pipe Laid out on a Slop The inlet pressure of a lateral pipe which laid out along a slope is as follows: hu - the lateral inlet pressure hs - pressure head of selected sprinkler hf - head loss along lateral riser - riser height - adjustment for an upward slope - adjustment for an downward slope

  32. Example: Following the previous example, but this time with: a. 2% downward slope, or b. 2% upward slope. The difference elevation between the two ends is as follows: a. 2% downward slope

  33. Cont. The pressure by the last sprinkler is as follows: The head loss between lateral inlet and last sprinkler is:

  34. Cont. 27.12m 25.3m • 360 m Δhf=3.2m 20%=5m P=30.3m P=28.5m • Sub-main 28.5 – 25.3 m = 3.2 m is taken place along the sub-main pipe. Therefore, the pressure at the head of the field is 28.5 m.

  35. Continue: • b. 2% upward slope • The total head loss throughout the lateral pipe is: 5.14 meters are just the permitted 20% head loss. Therefore, nothing is left for the sub-main. In this case, pressure regulators should be installed in every lateral inlets or selecting a wider pipe.

  36. Maximum Permitted Head loss

  37. Distribution of water and pressure s

  38. “The 20% rule” In order to maintain up to 10% difference in flow rate between sprinklers or emitter within a sub-plot, then the pressure difference inside the plot should be less than 20%. or • Q - flow rate • C–coefficient, which depends on a nozzle type • A - cross section area of a nozzle • H - pressure head • X - exponent which depends on the flow pattern.

  39. Pressure Vs. Flow Pressure m Liter/hr

  40. O-tif Flow rate Vs. Pressure Brown 2lph Black 4lph Green 8lph Purple 16lph

  41. 3/8" Rondo Nozzles - Flow rate Vs. Pressure

  42. Supertif - flow rate Vs. Pressure

  43. Ram & Agriplas Flow rate Vs Pressure

  44. Flow rate Vs Pressure

  45. Temperature Vs CV (tapes drip-line)

  46. Example: What is the expected difference discharge between the two ends of a lateral sprinkler? When the hydraulic gradient along a lateral pipe is 20%. The flow rate of a sprinkler is as follows:

  47. Continue: Two identical sprinklers have a same coefficient: The difference in flow rate between the two ends is 10% (within 20% rule), once the exponent is 0.5.

More Related