Evaluation of hot-film, dual optical and Pitot tube probes for liquid-liquid two-phase flow measurements

An experimental study of kerosene–water upward two-phaseflow in a vertical pipe was carried out using hot-film, dualoptical and Pitottubeprobes to measure the water, kerosene drops and mixture velocities. Experiments were conducted in a vertical pipe of 77.8 mm inner diameter at 4.2 m from the inlet (L/D=54). The tests were carried out for constant superficial water velocities of 0.29, 0.59 and 0.77 m/s (flow rates = 83, 167 and 220 l/min) and volume fractions of 4.2%, 9.2%, 18.6% and 28.2%. The Fluent 6.3.26 was used to model the single and two-phaseflow and to reproduce the results for the experimental study. Two methods were used to evaluate the accuracy of the probes for the measurement of the velocities of water, drops and mixture for two-phaseflow: (i) comparison of measured local velocities with predictions from the CFD simulation; (ii) comparison between the area-averaged velocities calculated from the integration of the local measurements of water, drops and mixture velocities and velocities calculated from flow meters’ measurements.

The results for single phaseflow measured using Pitottube and hot-filmprobe agree well with CFD predictions. In the case of two-phaseflow, the water and drops velocities were measured by hot-film and dualopticalprobes respectively. The latter was also used to measure the volume fraction. These three measured parameters were used to calculate the mixture velocity. The Pitottube was also used to measure the mixture velocity by applying the same principle used for single phaseflow velocity. Overall the mixture local velocity measured by Pitottube and that calculated from hot-film and dualopticalprobemeasurements agreed well with Fluent predictions. The discrepancy between the mixture area-averaged velocity and velocity calculated from flow meters was less than 10% except for one test case. It is concluded that the combined hot-film and optical approach can be used for water and drop velocity measurements with good accuracy for the flow conditions considered in this study. The Pitottube can also be used for the measurement of mixture velocities for conditions of mixture velocities greater than 0.4 m/s. The small discrepancy between the predictions and experimental data from the present study and literature demonstrated that both instrumentation and CFD simulations have the potential for two-phaseflow investigation and industrial applications.