Analisi sperimentale della dispersione di liquidi immiscibili in un reattore agitato tramite tecniche ottiche

The aim of this work is the local characterization of the dispersion of two immiscible liquids in a mechanically stirred tank of standard geometry. To this end, the turbulent flow field of the two phases was measured by Particle Image Velocimetry (PIV) and the Droplet size Distribution (DSD) was obtained by laser granulometry. The dispersion of diesel oil and of two silicone oils of different viscosity in water has been characterized at different agitation speeds, all corresponding to the complete dispersion of the droplets, using two different volume fractions of the dispersed phase, equal to 0.05% and 0.1 %. After the development of the experimental procedures for obtaining reliable measurements and the identification of the range of applicability of the two measurement techniques, the collected data were analyzed to identify the effect of the agitation conditions on the DSD. The measurements of the droplet average diameter were also used to understand the water and oil velocity measurements on a vertical plane of the stirred tank. By the measured flow fields, the influence of the dispersed phase on the mean and fluctuating velocity of the continuous phase is assessed and the influence of the physical properties and of the volumetric fraction of the dispersed phase on the stirred tank fluid dynamics as a function of the impeller speed is observed.