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 gravity feed type liquid fertilizer distributor has fixed orifices for metering. Liquid is supplied from a top vented tank with a height of 460 mm. The bottom of the tank is 610 mm above the ground and the ends of the delivery tube are 75 mm below the ground level. The metering heads (including orifices) are just below the tank, but the delivery tubes are small enough so that each one remains full of liquid between the orifice and the outlet end (thereby producing a negative pressure head on the orifice). The ratio between flow rates when the tank is full and when it is filled to a height of only 25 mm is
Options:
(A) 1.27
(B) 1.61
(C) 2.31
(D) 4.28
Official Answer Key:
A
Step-by-Step Solution & Explanation
Because the full delivery tube (siphon action) stays primed, the effective driving head on the orifice = liquid depth in tank + vertical drop from orifice to the delivery outlet. Drop from orifice (bottom of tank, 610 mm above ground) to outlet (75 mm below ground) = 610−(−75) = 685 mm. Head when full: H₁ = 460+685 = 1145 mm; Head when filled to 25 mm: H₂ = 25+685 = 710 mm. Orifice flow ∝ √H, so ratio Q₁/Q₂ = √(H₁/H₂) = √(1145/710) = 1.27.
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