HYDRAULICS_5 Design of Irrigation Systems by László Ormos
DESIGN OF MANIFOLD The manifold is a pipe with multiple outlets to the inlets of lateral pipes. The size of plot, the flow rate and the number of shifts in a complete irrigation cycle should be taken into consideration. An orchard is designed for irrigation with a solid set system. The manifold is laid in the center of the field. The whole plot is irrigated simultaneously. The flow rate of selected sprinklers is qs=0. 11 m 3/h at a pressure hs=2 bars. The space between the sprinklers along the laterals is es=6 m. Space between laterals is e. L=8 m. What are the diameters of pipes if the local head loss in the manifold and laterals is 10%?
DESIGN OF MANIFOLD manifold H=96 m B=96 m lateral The topography of field is the following:
DESIGN OF MANIFOLD Design of lateral 1. The maximum allowable pressure head variation is: 2. The number of sprinklers on every laterals is as follows: 3. The length of lateral is: 4. The total outlet of a lateral is:
DESIGN OF MANIFOLD For 16 mm PE lateral pipe 5. The hydraulic gradient when Q=0. 88 m 3/h and J 16=22% 6. 7. The head loss in the lateral pipe (including 10% local head loss) and coefficient F 6=0. 38, is: Since hf> h the pipe diameter has to be increased. The hydraulic gradient if diameter is 20 mm of PE which has J 20=6. 5% by Q=0. 88 m 3/h. is:
DESIGN OF MANIFOLD 8. The head loss in the lateral pipe (including 10% local head loss) and coefficient F 8=0. 38, is: Since hf< h the pipe diameter is good. 9. The inlet pressure in the lateral is: 10. The water pressure by the last sprinkler on the lateral is:
DESIGN OF MANIFOLD Design of manifold 11. The number of laterals is as follows: 12. The length of manifold is: 13. The total flow rate is as follows:
DESIGN OF MANIFOLD For 63 mm PE manifold pipe 14. The hydraulic gradient when Q=21. 12 m 3/h and J 63=7. 2% 15. The head loss in the manifold (including 10% local head loss) and coefficient F 24=0. 371, is: 16. The pressure by the manifold inlet is: 17. The pressure by the inlet of last lateral is:
DESIGN OF MANIFOLD 18. The minimum pressure in the entire system at the last sprinkler on the last lateral is as follows: 19. The pressure difference between the first and last sprinkler is: Since the pressure difference hf-l is lower than the allowable pressure head variation hmax, the system is good.
References Azenkot, A. (1998): ”Design Irrigation System”. Ministry of Agriculture 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 Agriculture 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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