Abstract
The present work concerns a numerical investigation of the effect of orifice meter diameters on the discharge coefficient for flow measurement purpose. The flow is subject to two disturbers namely a 90° double bend in perpendicular planes and a 50% closed valve. The turbulent flow is examined in conduit with an inner diameter of D=100mm. The diameter of orifice meters are respectively d=40, 50, 60, 70 and 75mm which done for β ratio d/D respectively the values of 0.4, 0.5, 0.6, 0.7 and 0.75. The orifice meters are located in conduit at different stations downstream the disturbers. The flow is examined with air at Reynolds number Re=2.5x105 . The software used for this simulation is CFD code Fluent with k-e like turbulence model. As a conclusion, the analysis of numerical results shows that when the diameter of the orifice meter increases the shifts deviation in the discharge coefficient increases this causes a great error in flow measurement. Contrary, when the diameter of the orifice meter decreases the shifts deviation in the discharge coefficient decreases and the errors in flow measurement is reduced. These results are the same with the two disturbers used separately in conduit.
Highlights
Orifice meters have been used for flow measurement for many years for process and fiscal proposes
Experiments were conducted to determine the relative change in the orifice meter discharge coefficient when subjected to non-standard approaching flow conditions as the 50% closed valve
Experiments were conducted to determine the relative change in the orifice meter discharge coefficient when subjected to non-standard approaching flow conditions as the 90° double bend in perpendicular planes
Summary
Orifice meters have been used for flow measurement for many years for process and fiscal proposes. The majority of the orifice meters must be calibrated This is done in fully developed pipe flow, axisymmetric pipe that is free from swirl and pulsation. Standards such as ISO5167 (2003) define a satisfactory flow. While high accuracy about 0.5% flow rate measurement is required, disturbances in the flow caused by valves, bends, and other component introduce errors of more than 3%. Given that most industrial installations include disturbers like bends, valves, expanders and reducers, which are sources of swirl, asymmetries and turbulence distortions, insuring that fully developed flow in terms of mean flow and turbulence structure approach the meter is difficult to achieve in practical situations. A flow meter needs to be presented with an axisymmetric, fully developed velocity profile with zero swirls. The investigation is conducted to show the effect of the two disturbers namely a 90° double bends in perpendicular planes and a 50% closed valve on the deviation of the discharge coefficient
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