Droplet size distributions in liquid–liquid semi-batch Taylor vortex flow

Abstract

Optical methods were used to measure droplet size distributions in a liquid–liquid Taylor vortex reactor oriented vertically along its main axis and operated in a semi-batch fashion with continuous feed of the dispersed phase and no feed or removal of the continuous liquid. The effects of two operational parameters on droplet size distributions were considered, including the inner cylinder angular velocity and the dispersed phase inlet flow rate. Both the mean droplet diameter and the droplet size distribution were found to depend upon the jet Reynolds number and were independent of cylinder rotation speed up to the largest azimuthal Reynolds number investigated (60 000). The droplet size distribution underwent a transition from a unimodal distribution at low cylinder rotation speeds to a bimodal distribution at intermediate speeds. At the largest rotation speeds considered, the bimodal distribution became right-skewed. These observations provide support for the hypothesis that the mean droplet size and size distribution are determined primarily by jet breakage dynamics at the tips of inlet nozzles. Furthermore, the mean droplet size data collected from two geometrically distinct reactors can be collapsed onto a universal curve by plotting the Weber number against the jet Reynolds number.