Calculation method
The measurement method involves installing the orifice plate into a pipeline that is completely filled with fluid. The orifice plate generates a static pressure difference between the upstream and downstream sides.
The mass flow rate \( q_m \) is calculated using the equation:
\[ q_m = C \cdot \varepsilon \cdot \frac{\pi}{4} \cdot d^2 \cdot \frac{ \sqrt{2 \cdot \Delta p \cdot \rho} }{ \sqrt{1 - \beta^4} } \]
The software also provides a simplified flow equation:
\[ q_m = C \cdot \sqrt{ \Delta P } \]
The simplified equation is intended for use with differential pressure transmitters, where it can be directly input. However, it may introduce errors in flow readings outside the nominal operating point.
The software provides precise orifice plate dimensions for manufacturing, along with the required pressure tap distances. Additionally, it specifies the minimum and maximum allowable pipe roughness values and calculates the exact discharge coefficient over the entire measurement range, allowing the user to apply the full flow equation accurately across the entire measurement span.
It also provides the minimum required straight pipe lengths upstream and downstream of the orifice. If the designer provides shorter lengths, the software calculates the resulting additional measurement error.