GATE 2017 CE (CE2) – Question 59
A horizontal 100 mm diameter pipe carries 0.01 m³/s at Reynolds number 800. Take g = 9.81 m/s². Head loss per kilometre, to one decimal place, is ______ m.
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Correct answer: 65.0 to 69.0
Explanation
Velocity is $V=Q/A=0.01/[\pi(0.1)^2/4]=1.27324$ m/s. At Re = 800, Darcy friction factor is $f=64/800=0.08$. Thus $h_f=f(L/D)V^2/(2g)=0.08(1000/0.1)(1.27324)^2/(2\times9.81)=66.1$ m per kilometre.