溶液预冻方式与冰晶粒度分布之间的关系

Relationship between freezing methods of solution and ice grain size distribution

考虑到在真空冷冻干燥过程中,预冻阶段会通过影响冻结体冰晶粒度的分布最终对干燥过程的速率、能耗以及冻干产品品质产生重大影响,基于CFD软件对溶液在预冻过程中温度场变化的数值模拟结果,计算冻结后冰晶粒度,并研究控制搁板温度恒定、从常温匀速降温以及含养晶过程中恒温降这3种冻结方式对冰晶粒度分布的影响,分别得出各预冻参数(搁板温度、温降速率和养晶时间)与冰晶粒度分布参数(冰晶粒度平均值和标准差)之间的回归关系式,并且进行不确定度分析和显著性检验。研究结果表明:回归关系拟合优度和参数准确度较高,且多项式分布显著性水平达0.98以上,这对冻干曲线的优化有着一定的参考价值。

Considering that in the vacuum freeze drying process, the pre-freezing stage will affect the distribution of ice crystal size of frozen material, which will ultimately affect the drying rate, energy consumption and the quality of freezedried products, based on the numerical simulation results using CFD of the temperature field changing during the prefreezing process, the size of ice grain size after freezing was calculated, and three kinds of freezing methods, i. e., maintaining shelf constant low temperatures, controlling the shelf to cool from room temperature with constant rates and cooling at constant rate containing crystal growth process, were studied to research the effects on the size distribution of the ice crystals. The formula of the fitting relationship between prefreezing parameter which included the temperature of shelf, the rate of temperature drop, the crystallization time and grain size distribution parameters of ice which included average value and uniforming of ice crystal were obtained, and the uncertainty analysis and the significance test were carried out. The results show that the fitted goodness and parameter accuracy are high and the significance level of polynomial distribution is above 0.98, which has reference for the optimization of freeze-drying curve.