送风参数对马铃薯泥冷冻特性的影响

利用Fluent软件建立马铃薯泥三维鼓风冷冻数值模型,研究冷冻时间对送风温度和速度的敏感程度,分析不同位置马铃薯泥冷冻条件和冷冻时间的不均匀度随送风参数的变化规律。结果表明,送风温度的改变对冷冻时间的影响比送风速度大。送风温度不变,随着送风速度的增大,马铃薯泥周围风速的不均匀度逐渐增大,温度的不均匀度逐渐减小,冷冻时间的不均匀度和中心温度的不均匀度随送风速度的增加呈现先减小后增大的趋势,送风速度为6 m/s时,二者最小。同一送风速度条件下,送风温度越低,马铃薯泥周围温度的不均匀度越小,中心温度的不均匀度越大。经验证,模拟结果与实验结果吻合较好,冷冻时间相对误差为3.27%,温度的平均绝对误差为0.79 K,均方根误差为2.11K。

Influence of air supply parameters on the freezing process of mashed potatoes

In order to investigate the sensitivity of freezing time to air temperature and velocity, and analyze the variation of the freezing conditions and freezing time of mashed potatoes in different locations, a three-dimensional unsteady numerical model was established. According to the thermo-physical properties of mashed potatoes, the process of the temperature decreasing during freezing was simulated by Fluent. The unevenness of freezing conditions and time was obtained under different air velocity-inlet and temperature-inlet. The results showed that the change in the percentage of air temperature-inlet had a greater effect on freezing time than air velocity-inlet. With the increase of the air velocity-inlet, the unevenness of the air velocity around the mashed potatoes increased, and meanwhile the unevenness of the air temperature around the mashed potatoes decreased. The variation coefficient of temperature among mashed potatoes and the unevenness of freezing time firstly increased and then decreased with the increase of air velocity-inlet, and they were minimum when the air velocity-inlet was 6 m/s. Under the same air velocity-inlet, the in-homogeneity of the temperature around the mashed potatoes is inversely proportional to the air temperature-inlet. The experimental result showed that the simulation data was in good agreement with the experimental data. The relative error of freezing time was 3.27%, and the average absolute error of temperature was 0.79 K, with the root mean square error of 2.11 K. These results reviewed some characteristics of the freezing process of mashed potatoes without packages in an air blast freezer, which could provide a reference value for the optimization of the equipment and technologies for the freezing of foodstuffs.