Imaging method for mass transport measurements in a two-phase bubbly flow of supercritical CO2 and viscous liquids in a static mixer

In this work, a simple optical measurement method for two-phase bubbly flow investigations was developed using backlight imaging and particle image velocimetry techniques. Besides information about bubble sizes, surface area and volumes, the mean dispersed phase mass flow rate and the mean dissolution of the dispersed phase in the continuous phase at the end of a static mixer were accurately estimated. The method was validated with air-in-glycerol and water-in-oil systems, and then proven with CO2-glycerol and CO2-PEG6000 dispersions under high pressure. A 30-element SMX4 plus static mixer with a nominal outer diameter of 4.8 mm was used for all mass transfer investigations. Measurements of the dispersed phase mass flow and the dissolution of the dispersed phase at the end of the mixer are reported with combined uncertainties of 8.1 % and 1.0 wt-%. The first experiments with CO2-glycerol and CO2-PEG6000 prove the applicability of this method for systems under high pressure.