Formation of frazil ice: an experimental study on the crystallization of a supercooled melt

Frazil ice formation is the crystallization of ice out of supercooled water. Ice nucleation and heat transfer were investigated in a turbulence jar where turbulence was generated by a moving grid. The growing ice crystals were observed by means of a Schlieren system and the number of ice particles was counted on photographs. The increase of temperature in the jar allowed an evaluation of the latent heat of fusion produced by the growing ice crystals and, therefrom, of the ice mass. Flow velocities were measured with a LDA. No frazil ice was observed regardless of turbulence and foreign material unless the water was seeded with ice nuclei. The number of particles grew during the experiments. The growth rate increased with the degree of supercooling and the velocity of the grid. This suggests a multiplication process induced by secondary nucleation. The measured Nusselt number of the particles was around 10 and agrees with theoretical estimates in the literature.