A Stochastic Model of Crystallization in an Emulsion - Laboratoire de ...

7 Numerical Simulations
Let us start with a presentation of the experimental context and of the experimental observations
(cf. Dumas et al [6]) :
Several emulsions have been used. For example, Octadecane in water, glycerol and TWEEN 80
( P = 0, 50 ); water in motor oil ( P = 0, 25 and P = 0, 50),
where P indicates the mass fraction. The
experimental cell (see gure 1) is a vertical metallic tube closed by two isolated caps. This cylinder
contains a cage which supports 12 thermocouples. They are located regularly in a horizontal plane
D, at different radii, for r = 0 for the thermocouple (1) to r = 27, 5 mm for the number (12) .
Then, the thermocouple number (13) is located on the outer surface and the number (14) in the
bath, where the cell is immersed. This bath is cooled between 60 c and 40 c at a constant rate
( 5 c/h to 30 c/h).
Figure 1: Experimental cell
On gure 2, we can see the experimental temperature curves, of the different thermocouples,
versus time during the cooling (for water, hexadecane and octadecane emulsions). We observe,
at the beginning of the cooling, before any crystallization appears, a linear decreasing of the
temperature only due to the heat conduction inside the emulsion (the temperature for r = 0 being
always the highest). Crystallizations are detected when the curves deviate from linearity.
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