基于COMSOL Multiphysics模型的瓶装液态食品巴氏灭菌过程的数值模拟研究

Numerical Simulation of Liquid Food Packed in Bottle Pasteurization Using COMSOL Multiphysics

以0.3%CMC溶液为研究对象,基于COMSOL Multiphysics软件建立二维传热模型模拟瓶装液态食品的巴氏灭菌过程。采用无线温度传感器对巴氏灭菌过程中瓶内温度的变化进行验证,发现模型预测的温度变化很好地拟合了所测温度的变化。在此基础上,用COMSOL Multiphysics软件模拟玻璃瓶内的温度分布、速度分布及致死率值。结果:玻璃瓶装液态食品巴氏灭菌过程中存在明显的自然对流现象,最慢加热区(SHZ)在受热过程中逐渐下移,最终位于距离瓶底部0.98 cm处。瓶中液体在加热开始时流动速度最快,达12.89 mm/s,随后逐渐减小,加热1 800 s后降为0.314 mm/s。杀菌结束后最低温度点与杀菌值最小点不在同一处,两点的致死率值变化差异很小。整个玻璃瓶内的最大、最小致死率值相差10.5 min,表明杀菌过程可能存在某些部位杀菌不足,而某些部位过杀菌的现象。

A two-dimensional heat transfer model was established to simulate thermal pasteurization process of model food （0.3% sodimn carboxy-methyl cellulose（CMC）solution） based on COMSOL Multiphysics in this paper. In this study, COMSOL Muhiphysics simulation of temperature predictions was validated with experimental measurements of the tempera- ture in the bottle filled with 0.3% CMC solution. The results show that temperature profiles obtained by COMSOL Multi- physics were in good agree-ment with experimentally determined values by wireless temperature recorder. After validation, further simulations were carried out for the temperature distribution, the velocity profile and pasteurization unit （PU） in the bottle. It has been shown that the action of natural convection forces the slowest heating zone （SHZ） to migrate to- wards the bottom of the bottle as expected, that is about 0.98 cm from the bottom at 1 800 s. The magnitude of the ve- locity was found to be 12.89 mm/s at 60 s, decreased gradually with 0.314 mm/s at 1 800 s. The location of minimum PU value was not in accordance with the SHZ with a little difference in the profile of PU value. The difference of PU value between maximum and minimum was 10.5 min, which indicates thermal pasteurization is uneven seriously.