Frazil Ice Formation,

Abstract

Abstract : Frazil ice forms in flowing or turbulent water that has become supercooled by heat transfer to overlying air. This report investigates the influences of turbulence and water temperature on frazil ice formation. The rate and the quantity of frazil ice formed in a specified volume of supercooled water increase with both increasing turbulence intensity and decreasing water temperature. The influence of turbulence intensity on the rate of frazil ice formation, however, is more pronounced for larger initial supercooling. The turbulence characteristics of a flow affect the rate of frazil ice formation by governing the temperature to which the flow can be supercooled, by influencing heat transfer from the frazil ice to surrounding water, and by promoting collision nucleation, particle and floc rupture and increasing the number of nucleation sites. Larger frazil ice particles form in water supercooled to lower temperatures. The particles usually were disks, with diameters several orders greater than their thickness. Particle size generally decreased with increasing turbulence intensity. This report develops an analytical model, in which the rate of frazil ice formation is related to temperature rise of a turbulent volume of water from the release of latent heat of fusion of liquid water to ice. Experiments conducted in a turbulence jar with a heated, vertically oscillating grid served both to guide and too calibrate the mathematical analytic model as well as to afford insights into frazil ice formation. The formation of frazil ice was studied for temperatures of supercooled water ranging from -0.9 deg to -0.05 deg C.