食品真空冻干传热差异性研究

Study on Heat Transfer Difference of Vacuum Freeze-drying of Food

为优化食品冻干工艺,试验研究分析了不同冷冻干燥条件下的传热差异性以及相同条件下同一批次样品传热的不均一性.结果表明,在冻干过程中,随着冻干室压力的升高,有效传热系数呈线性增大,且使用不锈钢托盘冻干会使有效传热系数平均降低约28%;由于热辐射的作用,有效传热系数由冻干室边缘位置向中间位置逐渐减小,且随着压力的增大,其差异逐渐减小.

For the purpose of optimizing the freeze-drying technology of food,an experiment was conducted and an analysis was performed on the heat transfer difference under different drying conditions and the heat transfer heterogeneity of the same batch sample under the same drying condition.The results showed that the effective heat transfer coefficient almost increased linearly with the value of the freeze drying chamber pressure rising during the process of freeze-drying,and the use of stainless steel tray in freeze-drying would decrease the value of the effective heat transfer coefficient by about 28% on average.Due to the effect of the thermal radiation,the effective heat transfer coefficient is reduced gradually from the edge of the freeze-drying chamber to the middle position,and the increase in drying chamber pressure would lead a reduction in heat transfer difference.