HYDRAULICS_2

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HYDRAULICS_2

• Design of Irrigation Systems
• by
• László Ormos

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Total Head by Bernoullis Law

• where
• the relative elevation of the water
• the pressure head of the water
• the water velocity head.

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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 .

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Energy Head Loss in Pipes

• The head loss due to friction is found out by the
  Hazen
• Williams expression
• where
• J is the head 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,
• C is the smoothness of internal surface of pipe.

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Energy Head Loss in Pipes

• The layout of an irrigation system is the
  following
• The flow rate of pump at A is QA300m3/h at pA6
  bar
• pressure. The water flow rate out of B is
  QB200m3/h.
• What are pressures at the points B and C?

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Energy Head Loss in Pipes

• For A-B the head loss due to a friction for the
  D1250mm
• pipe (C130) and Q300m3/h can be found out of
  tables or
• slide ruler. The hydraulic gradient is J11.
• The actual head loss due to a friction for
  L1900m long pipe is
• 2. The difference elevation between A to B is
• Water pressure at point B is

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Energy Head Loss in Pipes

• For B-C the head loss due to a friction for the
  D2150mm
• pipe (C130) and Q100m3/h can be found out of
  tables or
• slide ruler. The hydraulic gradient is J18.
• The actual head loss due to a friction for
  L2200m long pipe is
• 5. The difference elevation between B to C is
• The water pressure at point C is

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Energy Head Loss in Pipes

• The result can also be computed by Bernoullis
  law for B
• and C only as follows
• Water flow velocity in 250mm pipe is the
  following

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Energy Head Loss in Pipes

• Water flow velocity in 150mm pipe is the
  following

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Energy Head Loss in Pipes

• The difference head velocity is
• Water velocity heads are as follows

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Energy Head Loss in Pipes

• Water pressure at point C is
• (since the difference velocity head ?hv has been
  too small it can be neglected)

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Energy Head Loss in Pipes

• Given a 300 meters long pipe and its diameter is
  250mm
• (C130) 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?

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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

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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
• J8 and D250mm. It is about 250m3/h.

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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