This paper analyzes primary vacuum freeze drying of poly-γ-glutamic acid (γ-PGA), a biomaterial, by considering the variation in tortuosity under different operating conditions. The results indicate that lower heating-plate temperatures and thinner sample thicknesses increase tortuosity, but the influence of heating-plate temperature on tortuosity is relatively small compared to that of sample thickness. A tortuosity model reflecting mass-transfer characteristics of the pore structure in a dried γ-PGA sample was derived, and the drying process was numerically analyzed via a moving-grid system and the finite-difference method. Numerical simulation results using the developed drying model matched well with the experimental results, with an error of less than 10 %. Decreasing heating-plate temperature or increasing sample thickness increases the time required to complete primary drying. In particular, increases in sample thickness result in greater changes in drying time than those in heating-plate temperature. The sample thickness range that resulted in the fastest drying rate was approximately 14–19 mm depending on heating-plate temperature. Lower heating-plate temperature resulted in smaller optimum sample thickness. The maximum drying rate in this study was observed at a heating-plate temperature of −5 °C and a sample thickness of 19 mm.

本文通过考虑不同操作条件下曲折度的变化，对生物材料聚γ-谷氨酸（γ-PGA）的初次真空冷冻干燥进行了分析。结果表明，较低的加热板温度和较薄的样品厚度会增加曲折度，但与样品厚度相比，加热板温度对曲折度的影响相对较小。得出了反映干燥γ-PGA样品中孔结构传质特性的曲折模型，并通过移动网格系统和有限差分法对干燥过程进行了数值分析。使用开发的干燥模型的数值模拟结果与实验结果非常吻合，误差小于10％。降低加热板温度或增加样品厚度会增加完成一次干燥所需的时间。特别地，样品厚度的增加导致干燥时间的变化大于加热板温度的变化。根据加热板温度的不同，导致最快干燥速度的样品厚度范围约为14-19 mm。较低的加热板温度导致较小的最佳样品厚度。在-5°C的加热板温度和19 mm的样品厚度下观察到本研究中的最大干燥速率。根据加热板温度的不同，导致最快干燥速度的样品厚度范围约为14-19 mm。较低的加热板温度导致较小的最佳样品厚度。在-5°C的加热板温度和19 mm的样品厚度下观察到本研究中的最大干燥速率。根据加热板温度的不同，导致最快干燥速度的样品厚度范围约为14-19 mm。较低的加热板温度导致较小的最佳样品厚度。在-5°C的加热板温度和19 mm的样品厚度下观察到本研究中的最大干燥速率。