Chandana Ratnayake

CFD modeling of dilute phase pneumatic conveying in a horizontal pipe using Euler–Euler approach

ABSTRACT Computational fluid dynamics simulations were performed to investigate the behavior of dilute phase pneumatic conveying of plastic pellets in a horizontal circular pipe. The pellets are 200 µm in diameter and 1000 kg/m3 in density. A parametric study was performed to investigate the effects of turbulence model and model collision parameters on pressure drop, solid’s volume fraction and velocity profiles. Among model collision parameters, specularity coefficient has considerable effect on the pressure drop. Moreover, the results from simulations carried out for different solid loadings and velocities were compared with experimental data found in the literature. The air velocities range from 6 to 15 m/s and solids to air mass flow ratios range from 1 to 3. At higher air velocities, the pressure drops predicted by the standard k-omega turbulence model are higher than the pressure drops predicted by the standard k-epsilon model. In contrast, at lower gas velocities, the standard k-epsilon model predicts higher pressure drops compared to the standard k-omega turbulence model. However, no significant difference in solids and air velocity profiles is observed for the two different turbulence models.

Dependence of Granular Materials Homogenization on Geometrical Aspects in Commonly Used Mixers via DEM

The manipulation (transport, mixing, segregation etc.) with powders and granular materials can be crucial for the quality of a final product. Detailed description and analysis of granular flow phenomena from the first principles is therefore very valuable. Here, simulations of granular mixing and segregation via discrete element method (DEM) of two types of mixers are performed and compared with experimental measurements. In the horizontal rotating drum mixer segregation of spherical particles with different diameters is studied. Different steady states are observed and their stability in dependence on the period of rotation and on the size of the system is discussed. Effect of operating conditions on granular flow dynamics and process of homogenization in the industrial paddle mixer is also analyzed. Global flow patterns development can be observed in both experiments and simulations.

Changes of Dextrose Particles with Pneumatic Conveying: Analysis of Size and Shape

When conveying particulate materials, changes in size and shape of individual particles can be observed. These changes can have a great impact on the bulk powder and affect its flow properties in the pipeline. Changes can be wanted or unwanted depending on the whole process chain and final use of the powder. In this investigation, dextrose monohydrate particles were pneumatically conveyed repetitively in a pilot plant–scale rig, and the size and shape of the particles were characterized by a semiautomatic image analysis method. This characterization was done qualitatively by observing micrographs and quantitatively for each individual particle (a total of 16,120 dextrose crystals) by using two statistical diameters and two shape factors. The effect of the changes in shape and size of the particles on the mass flow rate in the system was studied. It was concluded that the mass flow rate of the pneumatic conveying tests was not affected considerably by the changes of the dextrose particles.