Reversed Orifice Plate Correction Study
An orifice plate is a plate with a hole in the center that is placed in a pipe in which a fluid flows. The fluid is forced to converge through the orifice. The shape of the orifice induces changes in velocity and pressure. The accidental reversal of an orifice plate can results in a significant mismeasurement. This can occur, for instance, during maintenance operations and a long time may have elapsed before being noticed. Computational Fluid Dynamics (CFD) is a method that can be used to simulate the pressure and velocity distribution.
The point of maximum convergence occurs shortly downstream of the physical orifice and this point is called vena contracta. By measuring the fluid pressure drop between the normal pipe section and the vena contracta, the volumetric and mass flow rates were obtained from Bernoulli’s equation. 3-D Geometry was created, meshed, and then simulated using CFD. Results for velocity distribution and pressure distribution for the different flows and installations as well as the discharge coefficient and the correlation between the pressures drop in the correct and reversed installation were analyzed.
A significant difference between the correct and reversed installation has been shown. The simulation results have been validated based on the existing measured data showing a difference of about 10.91%. When the orifice is reversed, the pressure drop is about 40% more important than in the correct installation for the normal flow. That shows how important can be the mismeasurement when this problem occurs.