No abstract

No abstract

No abstract

No abstract

No abstract

Flow pattern of particles and their mixing performance in a Nauta blender were studied using the discrete element method. The model was validated by experimental data obtained in a convective conical screw blender and good agreement was obtained. Flow pattern of particles was studied through velocity profiles, granular temperature and streamlines of particles. Effects of sweeping rotation speed, primary rotation speed and impeller diameter on the mixing quality and mixing rate were studied. A vertical circulation pattern in the blender was observed due to the primary rotation of the impeller that produced a convective and layered flow. In this pattern, particles are lifted to the bed surface and then descend at the opposite side of the screw. On the other hand, the sweeping rotation of the impeller pushes the particles along the direction of sweeping which leads to a tangential flow of particles. Combination of primary and sweeping rotations of the impeller results in a three dimensional particle mixing. A semi-stagnant zone is also formed temporarily near the cone axis. It was found that increasing the primary rotation speed (from 5 to 10 rad/s) and impeller diameter

In this research, the volume of fluid (VOF) method is used to study the hydrodynamics of rotating packed beds (RPBs). The model is validated, and grid independence analyses are performed for cases with different operating conditions. The droplet size distribution is investigated to characterize the hydrodynamics of RPBs. Droplet size distributions are compared in two-dimensional and three-dimensional simulations, and it is demonstrated that two-dimensional simulations can provide an accurate prediction while significantly reducing the significant computational cost. Radial distributions of droplet diameter in the packing region are studied, and different trends are observed at different rotational speeds (fluctuating at ω = 250 rpm, increasing–constant at ω = 500 rpm, and decreasing at higher rotational speeds). These trends are explained using the breakup and coalescence of droplets during droplet–packing and droplet–droplet collisions. Breakup, coalescence, and deposition regimes of droplets depend on the Weber, Ohnesorge, and impact parameters. We observed that with increasing rotational speed, the average droplet diameter and its standard deviation decreased, while changing the liquid flow rate did not significantly affect the average droplet diameter. It is also observed that there is a critical rotational speed (depending on the bed configuration), beyond which the average droplet size does not decrease with increasing rotational speed.

No abstract