No abstract

The electrical capacitance tomographic (ECT) approach is increasingly seen as attractive for measurement and control applications in the process industries. Recently, there is increased interest in using the tomographic details from ECT for comparing with and validating and tuning CFD models of multiphase flow. Collaboration with researchers working in the field of computational fluid dynamics (CFD) modeling of multiphase flows gives valuable information for both groups of researchers in the field of ECT and CFD. By studying the ECT tomograms of multiphase flows under carefully monitored inflow conditions of the different media and by obtaining the capacitance values, C(i, j, t) with i = 1…N, j = 1, 2,…N and i ≠ j obtained from ECT modules with N electrodes, it is shown how the interface heights in a pipe with stratified flow of oil and air can be fruitfully compared to the values of those obtained from ECT and gamma radiation meter (GRM) for improving CFD modeling. Monitored inflow conditions in this study are flow rates of air, water and oil into a pipe which can be positioned at varying inclinations to the horizontal, thus emulating the pipelines laid in subsea installations. It is found that ECT-based tomograms show most of the features seen in the GRM-based visualizations with nearly one-to-one correspondence to interface heights obtained from these two methods, albeit some anomalies at the pipe wall. However, there are some interesting features the ECT manages to capture: features which the GRM or the CFD modeling apparently do not show, possibly due to parameters not defined in the inputs to the CFD model or much slower response of the GRM. Results presented in this paper indicate that a combination of ECT and GRM and preferably with other modalities with enhanced data fusion and analysis combined with CFD modeling can help to improve the modeling, measurement and control of multiphase flow in the oil and gas industries and in the process industries in general.

The main objectives of this work is to produce detailed velocity profile measurements over a range of operating conditions of two phase gas/liquid flow with low liquid fractions in horizontal and inclined pipes. The experiments are performed in a 15 m long stainless steel pipe section with internal diameter 56 mm at room temperature and atmospheric outlet pressure. Exxsol D60 oil (viscosity 1.30 mPa s, density 793 kg/m 3), water (viscosity 0.89 mPa s, density 999 kg/m 3) and air (viscosity 0.018 mPa s, density 1.22 kg/m 3) are used as test fluids. The pipe inclination is changed in the range from 5° upward to 5° downward. The measurements are made at mixture velocity, 5 m/s for different inlet liquid fractions. The cross-sectional distribution of phase fractions is measured using a traversable single-beam gamma densitometer. The particle image velocimetry (PIV) is utilized in order to obtain non-invasive instantaneous velocity measurements of the flow field. Based on the instantaneous local velocities, mean velocities, root mean squared velocities and Reynolds stresses are calculated. The measured mean velocity and turbulence profiles show a strong dependency with pipe inclination. The present measurements show that PIV can be successfully used as a practical measurement technique for multiphase flow applications with potential to become even more powerful in the near future as digital camera technology progresses.

This paper presents detailed measurements on gas-liquid flows in horizontal and slightly inclined pipes. The mixture velocities, liquid fractions and pipe inclinations used in the experiments are in a range that is commonly used in transportation of unprocessed gas in offshore oil and gas industry. The experimental activities were performed using the multiphase flow loop at Telemark University College, Porsgrunn, Norway. The experiments were conducted in a 15 m long, 56 mm diameter, inclinable steel pipe using Exxsol D60 oil (density 793 kg/m3 and viscosity 1.3 mPa·s), water (density 999 kg/m3 and viscosity 0.89 mPa·s) and air (density 1.22 kg/m3 and viscosity 0.018 mPa·s) as test fluids. Mixture velocities of 5, 10 and 15 m/s, liquid fractions of 0.0010, 0.0025, 0.0050, 0.0075 and 0.0100 and pipe inclinations of -5°, -1°, 0, +1° and +5° from horizontal were investigated. The time-averaged crosssectional distributions of gas and liquid phases were measured using a singlebeam gamma densitometer. The characterization of flow patterns and identification of their boundaries were performed using high-speed videos, still pictures and live observations. Seven different flow patterns were identified for gas liquid flow in horizontal and slightly inclined pipes. The pressure drop and liquid hold-up measurements were also reported.