ANALYSIS OF POSITION AND ROTATION DIRECTION OF DOUBLE STIRRER ON CHAOTIC ADVECTION BEHAVIOR

Turbulent mixing can damage the material molecules because of turbulence. Whereas laminar mixing raises a problem when mixing is carried out on viscous liquids. The mixing mechanism using chaotic flow affects the mixing quality. The aim of the experiment was to determine the position and direction of the double stirrer chaotic mixer. The installation of a chaotic mixer uses a cylindrical tub and two different mixers consisting of a primary mixer (Pp) and a secondary mixer (Ps). Periodically rotate the container and stirrer. The center of the vessel and primary mixer are placed at the same coordinates. For ε=4 cm (Pp to Ps distance), there are three experiments, namely: vessel rotation and directional stirrer (P2S-a), vessel rotation and opposite stirrer (P2B-a), and vessel rotation, both primary and secondary stirrers are directional variations. (P2V-a). Eccentricity 7 cm, there are also three treatments as above: one direction (P2S-b), reverse direction (P2B-b), and variation of direction (P2V-b). The video camera recordings are processed digitally. Qualitative data show a pattern of behavior during mixing. Meanwhile, quantitative data is used to determine the level of mixing effectiveness. The results showed that the direction of rotation of the two cylinders had no effect on the effectiveness of chaotic mixing. Based on the number of initial droplets of dye, the treatment that experienced the fastest chaos was P2B-b, at n=2 and r=3.5303. The difference in the number of color droplets does not affect chaotic behavior. The highest mixing efficiency was generated by the lowest P2V-b mixing index value of 0.94. Simultaneously, the direction between the mixer and the container will provide maximum mixing efficiency. Isolated mixing areas (island) and areas of poor mixing occur because of one-way rotation and low eccentricity

Flow characteristics of the Rushton and pitched blade turbines in turbulent and laminar mixing

The velocity field and concentration distribution of three radial and axial impellers were studied in miscible liquid blending in a stirred tank reactor. To obtain a better insight into the applicability of each impeller system, the influence of velocity profiles on the generated concentration profiles was studied in detail for each impeller. Particle image velocimetry (PIV) and planar laser induced fluorescence (PLIF) methods were used as the measurement techniques. In the turbulent regime, the Rushton turbine provided a homogeneous concentration field throughout the reactor by generating high radial and axial velocities in the bottom and upper zones of the tank. Operation comparisons of the up and down-pumping pitched blade turbines illustrated that the up-pumping turbine had a better performance in overall because of producing high turbulence in the upper half of the reactor. In this region, the radial concentration profile approached the final homogenized value in a shorter time. In the laminar regime, all three impellers acted in a similar way and produced a radial flow throughout the reactor.

Laminar mixing of non-Newtonian fluids in static mixers: process intensification perspective

Static mixers are widely used in various industrial applications to intensify the laminar mixing of non-Newtonian fluids. Non-Newtonian fluids can be categorized into (1) time-independent, (2) time-dependent, and (3) viscoelastic fluids. Computational fluid dynamics studies on the laminar mixing of viscoelastic fluids are very limited due to the complexity in incorporating the multiple relaxation times and the associated stress tensor into the constitutive equations. This review paper provides recommendations for future research studies while summarizing the key research contributions in the field of non-Newtonian fluid mixing using static mixers. This review discusses the different experimental techniques employed such as electrical resistance tomography, magnetic resonance imaging, planar laser-induced fluorescence, and positron emission particle tracking. A comprehensive overview of the mixing fundamentals, fluid chaos, numerical characterization of fluid stretching, development of pressure drop correlations, and derivations of generalized Reynolds number is also provided in this review paper.