Experiment No. 1
EFFECT OF NOZZLE SIZE ON WATER DISTRIBUTION
Object:-To investigate the effect of nozzle size on the radial distribution of water from a Rotary Sprinkler.
Apparatus:-Sprinkler Test Rig (Catch Assembly, Display Unit, Pump Set and Storage Tank) and Stop Watch.
Theory:-The sprinkler supply water in the form of spray, somewhat as in ordinary rain. A sprinkler with a correct pressure and correct nozzle size gives distribution of water correctly, because the breakup of a sprinkler jet is function of both pressure and nozzle size. Small nozzles give adequate break up at a lower pressure than larger nozzles.
When compared to good sprinkler system uniformity, a poor system will use more water to irrigate a given area. Improving the application uniformity of a sprinkler system can reduce the water supply necessary to irrigate a given area. This savings in water will lower pumping and operating costs.
The increase in CU from 70 to 90% would reduce the water requirement by 38.3% with such a savings 62% more land can be irrigated.
CU (%) | Water applied over entire area to get at-least 1” on 90% of the area | Water saved with CU > 70% | Greater area irrigated with CU > 70% |
90 | 1.19” | 38.3% | 62.0% |
80 | 1.47” | 23.8% | 31.3% |
70 | 1.93” | 00.0% | 00.0% |
Where,CU = Coefficient of Uniformity
= Mean value of readings (Sum of all the readings i.e. )
n = Number of readings
Fig. 1 Sprinkler unit
Fig. 2 Water Distribution Pattern from a Rotary Sprinkler
Fig. 3 Distribution Patterns at Different Pressures
Fig. 5 Typical Rotary Sprinklers
Experimental
Setup:-The rig is set up for normal use with the display tubes primed. Catch cans are positioned 1.0 m apart from each other. Ensure that the jet dispersal screw is removed. Operate the sprinkler at different pressure for each of the nozzle sizes available. Run each test for 10-15 minutes or until a reasonable height of water is acquired in the display tubes.
Note the height of water in display tubes, which shows the depth of water in each catch can.
Observations:-
Pressure = _______ bar;Riser height = ______ cm
Catch Can No. | Nozzle Size (mm) | |||||
d1 = | d2 = | d3 = | ||||
(mm) | (mm) | (mm) | (mm) | (mm) | (mm) | |
1 | ||||||
2 | ||||||
3 | ||||||
4 | ||||||
5 | ||||||
6 | ||||||
7 | ||||||
8 | ||||||
9 | ||||||
10 | ||||||
∑ | ||||||
mm | mm | mm. | ||||
CU | % | % | % | |||
Graph:-Depth of water is plotted against distance from the sprinkler for various nozzle sizes, as shown in the attached Figure.
[Attach the graph here]
Result:-Based on the value of Coefficient of Uniformity i.e. _______%, it is evident that the nozzle size of ___________ mm gives the best radial distribution of water within the wetting circle of the rotary sprinkler at the pressure of _________ kg/cm2 and height of _________ cm. Hence it is suitable for the field conditions.
Conclusion:-