Question

What is the value of friction factor, if the diameter of pipe is 50 cm and roughness height is 0.25 cm?

• A. 0.0003
• B. 0.003
• C. 0.01002
• D. 0.03035

Answer 1

The correct option is D 0.03035

$\text{Data given : Diameter of Pipe,}d=50\text{cm}=0.5\text{m}$
$\text{Roughness height,}K=0.25\text{cm}$

Friction factor for turbulent flow in rough pipe is given by

$\frac{1}{\sqrt{f}}=2\log \left(\frac{R}{K}\right)+1.74$

$\text{where}R=\text{Radius of Pipe}=\frac{d}{2}=25\text{cm}$

$K=\text{Roughness height}=0.25\text{cm}$

$\frac{1}{\sqrt{f}}=2\log \left(\frac{25}{0.25}\right)+1.74$

$=2\log \left(100\right)+1.74$

$=2\log (10{)}^2+1.74$

$=2\times 2\times 1+1.74=5.74$

$f={\left(\frac{1}{5.74}\right)}^2=0.03035$