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HYDRAULICS_2

HYDRAULICS_2. Design of Irrigation Systems by László Ormos . Total Head by Bernoulli’s Law. w here the relative elevation of the water ; the pressure head of the water; the water velocity head. Energy Head Loss in Pipes. The energy loss (head loss) in pipes due to water flow

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HYDRAULICS_2

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  1. HYDRAULICS_2 Design of Irrigation Systems by László Ormos

  2. Total Head by Bernoulli’s Law where the relative elevation of the water; the pressure head of the water; the water velocity head.

  3. Energy Head Loss in Pipes The energy loss (head loss) in pipes due to water flow (friction) is proportional to the length of pipe: , where J is the head loss in a pipe expressed by either % or ‰.

  4. Energy Head Loss in Pipes The head loss due to friction is found out by the Hazen Williams expression: where J is thehead loss expressed by ‰, Q is the flow rate expressed by m3/hr, v is the flow velocity by m/sec, D is the diameter of pipe expressed by mm, Cis thesmoothness of internal surface of pipe.

  5. QB D2=150mm L2=200m B(hB=196m) C(hC=180m) D1=250mm L1=900m QA A (hA=172m) Energy Head Loss in Pipes The layout of an irrigation system is the following: The flow rate of pump at A is QA=300m3/h at pA=6 bar pressure. The water flow rate out of B is QB=200m3/h. What are pressures at the points B and C?

  6. Energy Head Loss in Pipes For A-B: the head loss due to a friction for the D1=250mm pipe (C=130) and Q=300m3/h can be found out of tables or slide ruler. The hydraulic gradient is J=11‰. • The actual head loss due to a friction for L1=900m long pipe is: 2. The difference elevation between A to B is: • Water pressure at point B is:

  7. Energy Head Loss in Pipes For B-C: the head loss due to a friction for the D2=150mm pipe (C=130) and Q=100m3/h can be found out of tables or slide ruler. The hydraulic gradient is J=18‰. • The actual head loss due to a friction for L2=200m long pipe is: 5. The difference elevation between B to C is: • The water pressure at point C is:

  8. Energy Head Loss in Pipes The result can also be computed by Bernoulli’s law for B and C only as follows: • Water flow velocity in 250mm pipe is the following:

  9. Energy Head Loss in Pipes • Water flow velocity in 150mm pipe is the following:

  10. Energy Head Loss in Pipes • The difference head velocity is: • Water velocity heads are as follows:

  11. Energy Head Loss in Pipes • Water pressure at point C is: (since the difference velocity head hvhas been too small it can be neglected)

  12. C HC=180m LBC =2200m A HA=30m LAB =300m B(booster) Energy Head Loss in Pipes Given a 300 meters long pipe and its diameter is 250mm (C=130) which connects a cistern (A) at elevation of 30m to a booster (B) at a sea level, and from there to a cistern 2200m away at elevation of 180m. The booster pump generates 17bar pressure. What is the flow rate?

  13. Energy Head Loss in Pipes • The water pressure just before the booster is as follows: • The water pressure just after the booster is as follows: • For B-C section

  14. Energy Head Loss in Pipes • The total pipe length is • The head loss due to the friction is as follows: The water flow rate can be found out of tables or a slide ruler based on J=8[‰] and D=250[mm]. It is about250[m3/h].

  15. References Azenkot, A.(1998):”Design Irrigation System”. Ministry of Agricul- ture Extension Service (Irrigation Field service), MASHAV Israel Dr. Avidan, A.(1995):”Soil-Water-Plant Relationship”. Ministry of Agriculture Extension Service (Irrigation Field service),CINADCO, Ministry of Foreign Affairs, MASHAV, Israel Sapir, E.-Dr. E. Yagev (1995):”Drip Irrigation”. Ministry of Agricul- ture and Rural Development, CINADCO, Ministry of Foreign Affairs, MASHAV, Israel Sapir, E.-Dr. E. Yagev (2001):”Sprinkler Irrigation”. Ministry of - culture and Rural Development, CINADCO,Ministry of Foreign Affairs, MASHAV, Israel Eng. Nathan, R. (2002):”Fertilization Combined with Irrigation (Fertigation)”. Ministry of Agriculture and Rural Development, CINADCO,Ministry of Foreign Affairs, MASHAV, Israel

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