Question

The pressure drop across an orifice is measured for a particular flow rate. If the flow rate is doubled, keeping all other parameters constant, the effect on the pressure drop across the orifice is.

• A. It will remain same
• B. It will also be doubled
• C. It will be halved
• D. It will increases by four times

Answer 1

The correct option is D It will increases by four times

In orifice meter the relation between flow rate (Q) and diffrential pressure $\left(\Delta P\right)$ is given by

$Q\propto \sqrt{\Delta P}$

$So,\frac{Q_1}{Q_2}=\sqrt{\frac{\Delta P_1}{\Delta P_2}}$

${\left(\frac{Q_1}{Q_2}\right)}^2=\frac{\Delta P_1}{\Delta P_2}$

$\Delta P_2=\Delta P_1{\left(\frac{Q_2}{Q_1}\right)}^2$

$\because$ $Q_2=2Q_1$

$\Delta P_2=\Delta P_1{\left(\frac{2Q_1}{Q_1}\right)}^2$

$\Delta P_2=4\Delta P_1$

Hence, pressure drop will increases by four times.