Measurement of Drop Size Distribution in Concentrated Liquid-Liquid Dispersions - Video and Capillary Techniques

Distributions in a concentrated dispersion have been measured in a stirred vessel. With the capillary technique, with a wide distribution, even after extensive testing of different sized capillaries and entry conditions and of threshold levels, both ends of the distribution were cut off. Sampling time is a problem when studying fast transients, as is the amount of fluid withdrawn when investigating phase inversion. Provided pictures can be taken, the video technique allows droplets from 25 μm upwards at concentrations up to those which cause phase inversion, i.e. ∼70% by volume dispersed phase, to be observed. These observations can be made at the wall and, by means of a 7 mm diameter light pipe and similar sized optical fibre strobe, inside the vessel. With a framing rate of 50 per second, the technique gives, second-by-second, size distributions to any discretization and means to any base. The structure is also revealed; for example, droplets-in-drops and bubbles are distinguishable from drops