GATE 2018 CE (CE2) – Question 59
A 1800 m³ flocculation tank is paddle-mixed at mean velocity gradient G = 100 s⁻¹. Water is at 30°C with dynamic viscosity $0.798\times10^{-3}$ N s/m². Theoretical mixing power, to two decimals, is ______ kW.
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Correct answer: 14.00 to 15.00
Explanation
From $G=\sqrt{P/(\mu V)}$, power is $P=\mu VG^2=(0.798\times10^{-3})(1800)(100^2)=14364$ W = 14.36 kW. This is dissipated theoretical power before drive-efficiency allowances.