Refreeze-melt

Figure 13.13 Physical mechanisms of recrystallization of ice crystals in ice cream (40% total solids) studied on a microscope slide under controlled temperature conditions (1) Ostwald ripening —10,0 0.010°C (2) Isomass rounding -5.0 0,010°C (3) Accretion -5.0 0.010°C and (4) Melt-refreeze -7.0 1.00°C with lOmin cycles. (From Donhowe and Hartel 1996 with permission.)...

Donhowe and Hartel (1996) also compared recrystallization rates of ice crystals in ice cream at different amplitudes of temperature fluctuations. Above temperature fluctuations of 0.50 °C, significantly faster recrystallization occurred, as compared to constant temperature conditions. Recrystallization rates were about twice as fast with temperature fluctuations of 1.00°C compared to 0.010 °C. The shape of the crystals after recrystallization at fluctuating temperatures was more jagged and uneven, whereas recrystallization at constant temperature produced a rounding effect. This was evidence that melt-refreeze and accretion were the main mechanisms of recrystallization under fluctuating temperatures. 

All refluxed melt will refreeze if reflux supphed equals that computed by Eq. (22-8). When reflux supplied is greater than the minimum, jacket cooling in the refining zone or additional cooling in the recoveiy zone is required to maintain product recoveiy. Since high-... 

Will ice at a temperature of — 10°C melt if pressure is applied to it If so, will it refreeze if the pressure is increased even more Which modification would have to form ... 

Place the block of ice on the board and drape the wire across the top as shown in the drawing.The ice just beneath the wire will melt because of the pressure exerted by the wire. The melted ice above the wire then refreezes, trapping the downward-moving wire inside the ice. 

A weighted wire cuts through a block of ice. The ice melts under the high pressure of the wire, and then refreezes behind the wire. 

After the heating power is off , the melted layer refreezes. 

While the theory of a pulse de-icer (PETD) and that of a pulse brake (PETB) is essentially the same, the eventual result of a heating pulse on an ice/substrate interface is opposite in these two devices. While in PETD ice slides off the substrate using the melt as a lubricant, in PETB the thin melted layer almost instantly refreezes, thus gluing the slider to the ice. 

A tour of physical processes accessible in single-component water ice in experiments in a freezer ductile flow and deformation-induced melting and refreezing... 

Figure 3 SEM images of porous media admixed with frost after melting of the ice phase at and subsequent refreezing down to -196°C (frozen H2O dark grey background), a medium II containing quartz (Qz) and kaolinite (Ka). b medium III containing quartz (Qz) and montmorillonite (Mm).

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