Measurements of the evolution of frazil ice particle size distributions

Abstract

A series of 27 experiments were carried out at three different turbulence intensities in the frazil ice production tank at the University of Alberta. The frazil particles produced were photographed in suspension throughout the duration of the supercooling process using a high-resolution digital camera. An acoustic Doppler velocimeter (ADV) was used to record vertical profiles of the velocities at three locations in the tank, and the velocity time series data were processed to determine the rate of dissipation of turbulent kinetic energy per unit mass. A computer algorithm was written to process the captured images to determine the particle sizes and compute the properties of the particle size distribution. The resulting data were used to study the evolution of the size distribution throughout the supercooling process. It was found that the number of individual particles in suspension peaked shortly after the maximum degree of supercooling had been reached, and at approximately the same time the mean and standard deviation of the particle diameter approached constant values. The overall mean particle diameter prior to the onset of particle flocculation was found to decrease with increasing values of the dissipation rate, and ranged from 0.94 to 0.66mm for dissipation rates of 24 to 336cm2/s3.