Experimental and numerical study on the orientation distribution of cylindrical particles in random packed beds

Cylindrical particles are widely employed in chemical engineering when a high surface area is necessary for process intensification. However, reliable information about the orientation of non-spherical particles in random packed beds is very scarce. Moreover, a potential effect of the orientation of cylindrical particles on fluid flow has not been examined yet in a real packing geometry. In this work, a new experimental approach has been applied to perform systematic studies of global and local orientation of cylindrical particles in random packed beds. Five different column-to-particle diameter D-c/D-p ratios were examined, ranging from 4 to 15.1. Orientation distribution was measured in the entire bed, with the bottom region excluded and in the core zone. Next, the experimental cases were reconstructed numerically with different packing densities. Finally, the effect of different orientation distributions of cylindrical particles, including full cylinders (FC) and Raschig rings (RR), on pressure drop (for identical bulk void fraction) in a selected packed bed configuration was examined numerically through computational fluid dynamics simulations. Reproducibility of particles' orientation distributions was found to be dependent on the number of particles per layer. A substantial effect of the column wall and its bottom on particles orientation was observed. The effect of orientation of FC on pressure drop was found to be moderate, however, in the case of RR, the maximum difference in pressure drop among investigated orientation distributions was as high as 400%.