Two long pipes in parallel are used to carry water between two reservoirs. The diameter of one pipe is twice that of the other. Both the pipes have the same value of friction factor. Neglect minor losses. What is the ratio of flow rates through the two pipes?

2.8

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5.6

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11.3

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Solution

The correct option is B 5.6
Two parallel pipes have same frictional losses

Also, $D_{1} = 2 D_{2}$
$h_{f 1} = h_{f 2}$

$\frac{f L Q_{1}^{2}}{12.1 D_{1}^{5}} = \frac{f L Q_{2}^{2}}{12.1 D_{2}^{5}}$

$∴ \frac{Q_{1}}{Q_{2}} = 2^{5 / 2} = 5.657$

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Two long pipes in parallel are used to carry water between two reservoirs. The diameter of one pipe is twice that of the other. Both the pipes have the same value of friction factor. Neglect minor losses. What is the ratio of flow rates through the two pipes?

The correct option is B 5.6Two parallel pipes have same frictional losses Also, D1=2D2 hf1=hf2 fLQ2112.1D51=fLQ2212.1D52 ∴ Q1Q2=25/2=5.657

The correct option is B 5.6
Two parallel pipes have same frictional losses

Also, $D_{1} = 2 D_{2}$
$h_{f 1} = h_{f 2}$

$\frac{f L Q_{1}^{2}}{12.1 D_{1}^{5}} = \frac{f L Q_{2}^{2}}{12.1 D_{2}^{5}}$

$∴ \frac{Q_{1}}{Q_{2}} = 2^{5 / 2} = 5.657$