Three Dimensional Numerical Simulation of Temperature Field of Carrot Pre-Freezing Process During Freeze-drying
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Abstract:
Pre-freezing is a significant stage during freeze-drying of foods in which the freezing temperature must be under the eutectic point. In order to compensate the defects in terms of consuming time and materials as well as getting limited information for experimental temperature measurement, the mathematical model of freezing was established and three dimensional unsteady numerical simulation of temperature field and dynamic propulsion of freezing interface were analyzed using FLUENT 6.3 based on computational fluid dynamics. The simulation results indicated that the freezing interface gradually moved from bottom to surface of carrot as the time increased. Due to the natural convection of cold air surrounding carrot surface, the last solidification zone was slightly below the upper surface area. The solidification time was about 25 minutes for carrot with thickness of 10 mm. After 40 minutes, the internal temperature was -10 ℃ lower than the eutectic point temperature of carrot. Numerical simulation verified by experiments showed thatthe result was in good agreement with the experiment, and could be accurately prediction of the freezing process.
