Author(s): Andreas Muller; Darryl J. Calkins
Linked Author(s): Andreas Müller
Keywords: No Keywords
Abstract: Turbulence affects frazil ice formation in three ways: It prevents stratification and formation of surface ice, it is involved in production and transport of ice nuclei and it controls the transfer of the latent heat of fusion from the growing ice particle to the supercooled water. To study ice nucleation and heat transfer, an experiment was conceived which allowed frazil ice to be produced under controlled conditions. Turbulence was generated by a moving grid in a turbulence jar, where water could be cooled below the freezing point. Frazil was observed by means of a schlieren system and the number of ice particles was counted on photographs. No frazil ice, regardless of turbulence and foreign material, was observed unless the water was seeded with ice nuclei. The number of particles grew during the experiment; the growth rate increased with greater supercooling and higher velocity of the grid. This indicates a multiplication process induced by secondary nucleation. The heat transfer per particle normalized with supercooling and the size of the particles was constant in all experiments within the accuracy of measurement. From these observations, it can be concluded that the total ice production is predictable if the heat transfer per particle can be estimated from turbulence data and if the number of particles can be calculated. A nucleation theory is, however, not available and is regarded as the crucial question.
Year: 1978