MEASUREMENT OF THE FLOW RATE AND VOLUME VOID FRACTION OF GAS-LIQUID BUBBLE FLOW USING A VORTEX FLOW METER

Abstract

Measurement of flow rate and volume void fraction by means of a conventional meter plays an important role in the development of measurement techniques for multiphase flow parameters. Owing to its advantage in insensitivity to most physical properties of the fluid-like viscosity and density, a vortex flow meter was used to measure the flow rate and volume void fraction of gas-liquid bubble flows in this study. The performance of the vortex flow meter under such flow conditions was investigated. First, regular Karman vortex shedding was found in bubble flows with less than 30% volume void fraction, but its stability was influenced by the introduction of a gas-phase component. Second, the frequency of the bubble vortex shedding was approximately in linear proportion to the two-phase Reynolds number, whereas the volume void fraction had little impact on the frequency. Third, the amplitude of the bubble vortex signal could be expressed as a power function format. Moreover, when the volume void fraction was in the range 0–25.90% and Reynolds number between 9.47 × 104 and 20.44 × 104, the meter coefficient of the vortex flow meter was kept constant. Correlations between the vortex shedding characteristics and two-phase flow parameters were established based on mathematical modeling and experimental calibrations. Finally, the two-phase mixture flow rate and the volume void fraction were obtained from the proposed correlations. These findings provide a possibility of using only a single vortex flow meter to measure double parameters in gas-liquid bubble flows.