| 摘要: |
| 本文采用无接触式称重法监测猪主动脉冷冻干燥过程，实时获取脱水速率，针对升华过程，通过采用准稳态传热模型结合脱水速率的变化来进行计算，获得升华温度、升华界面位移及传热量的变化规律。冻干参数分别设定为：预冻结温度-40 ℃、一次干燥-20 ℃、二次干燥10 ℃、冻干箱压力10 Pa。结果显示，样品的平均含水量为74.24%，其中自由水含量为71.96%。在一次干燥阶段，升华温度缓慢升高并最终接近搁板温度。随着传热温差的减小，传热量迅速下降，自由水移除速率减慢。冰晶的升华主要集中在血管内外壁处，其传热量占总升华热的70%~90%。随着传热量的减少，升华界面的移动速度减缓。在升华干燥前期传质阻力随干燥层厚度以恒定速率增长，而后期受传热的限制传质阻力增幅变大。 |
| 关键词: 冷冻干燥 传热传质 脱水速率 升华温度 传质阻力 |
| DOI： |
| 投稿时间：2020-07-13 修订日期：2020-08-18
|
| 基金项目:上海市动力工程多相流动与传热重点实验室基金项目（1N-15-301-101） |
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| Study on Heat and Mass Transfer of Vacuum Freeze-drying Process for Blood Vessels |
|
Gui Chao1,2, Tao Leren1,3, Zhang Yaqi1
|
| (1.School of Energy and Power Engineering, University of Shanghai for Science and Technology;2.School of Civil Engineering and Architecture, Xinxiang University;3.Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power and Engineering, University of Shanghai for Science and Technology) |
| Abstract: |
| In this study, the contactless weighting method was used to monitor the freeze-drying process of porcine aortas, and the dehydration rate was obtained in real time. For the sublimation drying process, the quasi-steady heat transfer model combined with the change in the dehydration rate could be used to calculate the change law of sublimation temperature, sublimation interface displacement, and heat transfer on each surface. The freeze-drying parameters were set as follows: the pre-freezing temperature was ?40 ℃, the primary drying temperature was ?20 ℃, the secondary drying temperature was 10 ℃, and the pressure of the freeze-drying chamber was 10 Pa. The study showed that the average moisture content of the sample was 74.24%, and the free water content was 71.96%. During the primary drying, the sublimation temperature increased slowly and eventually approached the shelf temperature. As the heat transfer temperature difference decreased, the heat transfer decreased rapidly, and the removal rate of free water decreased gradually. The sublimation of ice crystals was mainly concentrated in the inner and outer walls of the blood vessels, and its heat transfer accounted for 70%–90% of the total sublimation heat. With the decrease in heat transfer, the moving velocity of the sublimation interface decreased gradually. During the early stage of sublimation drying, the mass transfer resistance increased at a constant rate with the thickness of the dried layer, whereas during the later stage, the increasing rate of mass transfer resistance increased significantly with the restriction of the heat transfer. |
| Key words: freeze-drying heat and mass transfer dehydration rate sublimation temperature mass transfer resistance |
