Two-phase flow structure assessment based on dynamic image analysis

Abstract

Two-phase flow regime is an important industrial process phenomenon. Pressure drops, volume fraction and flow pattern are the most significant parameters describing the flow hydrodynamics of the two-phase mixtures. Authors propose a qualitative and quantitative description of the two-phase fluid flow structure, provided by the dynamic image analysis method. Method is based on high-speed visualization, stereological techniques and videogrammetry with grey level analysis and cross-correlation of signals. The study was conducted on a rectangular, vertical channel, with air-water co-current upwards flow. Dimensions of the channel are 5 × 50 × 1200 mm. The gas phase flux is 0.01 dm3/h and 0.16 dm3/h. The liquid phase flux is set to 0.01 dm3/h. The measurements and calculations were based on the stereology techniques, the Zuber-Finley and Mishima-Hibiki drift-flux model, and the grey level of the image. Two-phase flow parameters such as the void fraction, interfacial surface, free distance between objects, number of objects, average object size, drift and distribution coefficient was determined. Parameters were obtained as a function of time. Comparison of the image analysis results with the drift-flux models was made. To summarize, developed dynamic image analysis, provides information suitable for the assessment and reconstruction of the two-phase flow structure, which can be used for automatic process control.