A study of the Coriolis flowmeter as a reference instrument in multiphase flow
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The objective of this thesis was to investigate how a two-liquid mixture, and injected gas, affects the measurements of a Coriolis flowmeter. Furthermore it was of interest to investigate whether entrained gas could be detected, and to estimate the effect this has on the reference measurements in the CMR flow rig. A mathematical model of particle motion in an oscillating environment was used to simulate particle movement; The results were used to estimate the damping of the motion in the Coriolis flowmeter. Flow measurements, with and without injected gas, were carried out. Measurements of diesel/water mixtures were compared to the mathematical model, and uncertainty contributions were estimated. Based on measurements of high liquid flow rates, an estimate of the entrained gas quantity was made. The CMR flow rig behave as foreseen when changing the particle size and viscosity. The injected gas have significant impact on the damping. The uncertainty calculations show that measurements of diesel/water mixtures can be done without major uncertainty contributions. In the cases studied in this work, the uncertainty contribution is limited maximum -0.5%. The amount of entrained gas is probably less than ≈ 0:02% GVF and uncertainty contribution will in the studied cases be limited to a maximum of ≈ -0:01%. The contribution from a diesel/water mixture is small and CMR's uncertainty estimates are suffcient. The contribution from decoupling is so small that it is only of academic interest. The underlying conditions should however be studied more in detail. The measurements of entrained gas and its uncertainty contribution suggests that entrained gas does not affect the reference measurements in the flow rig.