High-speed visualization of multiphase dispersions in a mixing tank

A high-speed video system was used for studying multiphase dispersions by image analysis. A high-speed video camera, coupled to a stereomicroscope was used to record the dispersion occurring in a mixing tank. A high intensity direct light probe submerged in the liquid was used for illumination. Sequences of 200 images (512 x 384 pixels) at rates up to 5130 frames/s (fps) and magnification up to 11 x were obtained and analyzed. A detailed observation of the mixing dynamics at a high video rate allowed visualizing how oil drops and air bubbles move and interact. Velocity of the objects could be calculated at different focal planes. Rotational movement and trajectories in different directions, depending on the physicochemical properties of the system could be observed and recorded. The implemented methods also allowed the recording of the deformation of complex drops and were useful to discern situations of inclusions of objects (i.e. bubbles inside oil drops) in multiphase dispersions under power inputs up to 0.50 kW/m(3). (C) 2008 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.