马铃薯冻结过程中不同风速对相变界面的影响

Influence of phase change interface during freezing process of potato with different velocity of wind

相变界面的移动速度对冻结食品的品质有重要的影响。为探究不同风速对食品冻结过程中相变界面的影响,选择新鲜马铃薯为研究对象,结合马铃薯30^-40℃范围内的热物性,利用COMSOL模拟软件中的广义传热模型对马铃薯在不同工况速冻条件下的二维瞬态固体导热模型进行数值模拟。马铃薯模型为边长a=4 cm的正方形,T=-40℃,风速分别为u=1、2、4、8 m/s。然后进行了实验验证,分析了冻结过程中马铃薯在不同冻结风速下相变界面的移动规律。结合模拟结果与实验结果分析发现:相变界面在向中心的移动过程中速度逐渐增大。冷却空气温度为-40℃时,随着风速的增大,相变界面移动速率增大的幅度逐渐减小。无冷风时,背风侧相变界面的平均移动速率最快。冷风机风速大于4 m/s时,主迎风侧相变界面的平均移动速率大于背风侧相变界面的平均移动速率。风速越大,主迎风侧相变界面的平均移动速率越快。

The move speed of phase change interface has great influence on the quality of the frozen food. In order to study the impact of different wind speed on phase change interface during the food frozen process, this paper chosen the fresh potato as the study object, and combined the potato thermophysical properties in the range of 30--40℃, then used the generalized heat transfer model of COMSOL simulation software to do the numerical simulation on potato two-dimensional transient heat conduction in solids model under different working condition of frozen conditions, potato model is square with a length a=4 cm, T=-40℃, the speed of wind is 1 m/s, 2 m/s, 4 m/s and 8 m/s respectively. And analyzed the move rules of the potato phase change interface during frozen process of different wind speed. It can be discovered through combing the simulation result and experimental result that the phase change interface has gradually increased in the process of moving into the center. With the increasing wind speed, when the cooling air temperature is -40℃, the travel rate of phase change interface gradually decreases, while there is no cooling wind, the average travel speed of leeward side phase change interface is fastest. When the speed of cooling wind greater than 4 m/s, the average rate of the main windward side phase change interface is faster than the average rate of the leeward side phase change interface. And the greater the cooling wind speed, the greater the average rate of the main windward side phase change interface.