Characteristics of droplets formed on the outer surface of the rotating packed bed

A rotating packed bed (RPB), as a device for mass transfer enhancement, can be divided into three main parts. An eye of a rotor, a packing, and an outer cavity. It has been reported that a contribution to the total mass transfer of the outer cavity can reach up to 30% of the whole device. Mass transfer is highly influenced by the droplet hydrodynamics and dimensions, hence the liquid dispersion from the outer surface of a metal foam packing was recorded with a high-speed camera. The recordings were analysed with an in-house MATLAB® code to determine the droplet dimensions, and with a PIVlab software to evaluate velocity fields. It has been found that the droplet dimensions and velocities were influenced primarily by a packing speed, as the higher packing speed resulted in a presence of the smaller droplets. Two peaks in histograms for the droplet diameters could be explained with a breakup theory of a liquid jet which breaks into large, mother, and small, satellite droplets. The droplet velocity corresponded to a peripheral velocity of the packing. A liquid flow rate influenced only the number of droplets dispersed from the packing. This work was supported by the joint Polish-Czech project: no. UMO-2020/39/I/ST8/01381 financed by the National Science Centre, Poland, and no. GA 21-45227L financed by the Czech Science Foundation.