Orifice Flow Rate Calculator - Incompressible
The flow rate through an orifice plate can be determined by measuring the pressure difference between inlet and outlet. That is in this calculator implemented for sharp-edged orifice plates and incompressible flows in accordance with ISO 5167.
The mass flow rate is calculated using following:
\begin{align}
q_m = \frac{C}{\sqrt{1-\beta ^4}}\epsilon \frac{\pi }{4}d^2\sqrt{2\rho _1 \Delta p}
\end{align}
where C is the discharge coefficient. This takes into account the type of pressure tapping i.e. where the pressure is measured.
This calculator is only valid for incompressible flows.
Besides giving the mass flow rate the calculator also outputs the overall pressure loss of the orifice. This will be lower than what is measured at the tappings.
\begin{align}
\frac{\Delta p_{tot}}{\Delta p}=\frac{\sqrt{1-\beta ^4(1-C^2)}-C\beta ^2}{\sqrt{1-\beta ^4(1-C^2)}+C\beta ^2}
\end{align}
where β is the diameter ratio of the orifice diameter to pipe diameter d/D, Δptot is the overall pressure loss
and Δp is the measured pressure difference at the tappings.
Pressure tappings
Three types of standard pressure tappings are implemented in the calculator.
- Corner taps. The taps are placed just before and after the orifice plate e.g. with a special orifice carrier.
- D and D/2 taps also called radius taps. The pressure taps are placed one pipe diameter upstream and a half downstream of the orifice.
- Flange taps is installed 25.4mm (1 inch) upstream and downstream. Typically with a special flange.
