Prediction of air bubble dispersion in a viscous fluid in a twin-screw continuous mixer using FEM simulations of dispersive mixing

• Published in: Chemical engineering science 2012-12, Vol.84, p.303-314
• Main Authors: Vyakaranam, Kiran V., Kokini, Jozef L.
• Format: Article
• Language: English
• Subjects: 3D finite element method simulation; Applied sciences; Bubble break-up; Bubbles; Chemical engineering; Computer simulation; Density; Dispersive mixing; Exact sciences and technology; Finite element method; Mathematical analysis; Mathematical models; Mixers; Newtonian; Shear rate; Viscous flow
• ISSN: 0009-2509; 1873-4405
• DOI: 10.1016/j.ces.2012.07.014

Bubble break-up was studied during mixing of a viscous Newtonian fluid in a co-rotating twin screw continuous mixer using experimental observations and finite element method (FEM) simulation of dispersive mixing. Bubble break-up was greatest with two paddle element configurations that had no stagger and a reverse stagger respectively while a third configuration with a forward element stagger showed the least break-up. The decrease in bubble break-up was found to be due to the decrease in the elongation flow density and an increase in local forward flow in the forward angle stagger configuration. Maximum stable bubble diameters and effective shear rate for break-up calculated at different locations in the mixer using the fundamental capillary number theory for drop and bubble break-up correlated well with the measured local mean bubble sizes and the mean local shear rates calculated using FEM simulations of the flow. ▸ Dispersive mixing analysis in a twin screw continuous mixer using FEM simulations. ▸ Fundamental bubble breakup theories applied to the detailed flow analysis in a continuous mixing environment. ▸ Developing an effective flow strength/flow type conducive for bubble breakup in viscous continuous flow.