A Study of Mass Transfer from Large Oscillating Drops:2 Volumes

Abstract

A laboratory apparatus containing many novel features has been constructed for the study of the mass transfer rate from single oscillating drops ascending through water, where the overall transfer rate is controlled by diffusional resistance of solute in both phases. The transfer rate of acetone from toluene or n-heptane droplets to a saturated aqueous phase during counter-current operation was determined by the Messinger iodoform method (193). Photographic techniques were developed to record the frequency of droplet oscillation, area change, amplitude and vertical velocities with high speed cine photography. High concentrations of acetone were employed in the dispersed phase, i.e. up to 25% w/w because acetone has widely different effects on physical properties of the systems. This enabled an extensive examination to be made of different parameters on the mass transfer rate, frequency and amplitude of oscillation. A number of computer programms have been written to evaluate the actual instantaneous area of the droplet, its frequency and amplitude of oscillation and the mass transfer coefficients. Also the established methods for oscillating droplets, variance, mean and the general trend of the above parameters were calculated. In addition, empirical correlations were developed for the amplitude and the mass transfer coefficient. Studies under mass transfer condition showed that the velocity and the mass transfer rate were significantly different from those. predicted by hydrodynamic and molecular diffusion criteria. However, the discrepancies between observed and predicted values do not appear to be related to an easily measurable physical property...