Subtopic: Functional requirements, principles of working, construction and operation of manual, animal, tractor and renewable energy operated equipment for tillage, sowing, planting, fertilizer application, inter-cultivation, spraying, mowing, chaff cutting, harvesting and threshing
Question Statement:
A tractor sprayer boom is fitted with 20 hollow cone nozzles to achieve an application rate of 200 L ha⁻¹. During a calibration test the nozzle flow rate was found to be 1.25 L min⁻¹, whereas the rated nozzle flow rate of 0.473 L min⁻¹ was available at 275 kPa. If the nozzle produces droplets with a volume median diameter of 200 micron at 1 MPa, the droplet size in micron at the desired flow rate is
Options:
(A) 104.17
(B) 160.91
(C) 248.60
(D) 594.89
Official Answer Key:
B
Step-by-Step Solution & Explanation
Nozzle discharge varies with √pressure: Q=k√p. From the rated point (0.473 L/min at 275 kPa), the pressure needed to give the calibration flow of 1.25 L/min is p = 275×(1.25/0.473)² ≈ 1921 kPa. Volume median diameter (VMD) of spray droplets varies approximately as VMD ∝ p^(−1/4). VMD at the new pressure = 200×(1000/1921)^0.25 ≈ 170 μm, closest among the given options to 160.91 μm.
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