| 摘要: |
| 为实现对冻干工艺的精准热控制，提高冻干产品品质，本文以香蕉为研究对象，利用稳态热流法研究了在真空环境下压强（10、30、50 Pa）和干燥温度（﹣20、﹣30 ℃）对香蕉切块整个冻干过程中有效传热系数的影响。借助微CT扫描，观察分析了香蕉内部的升华过程，深入探讨了冻干过程孔隙率和有效导热系数的关系。结果表明：当压强由10 Pa增至50 Pa，对应的有效导热系数由0.036 W/(m?K)增至0.072 W/(m?K)；升华干燥温度由﹣30 ℃增至﹣20 ℃，对应的有效导热系数由0.084 W/(m?K)降至0.058 W/(m?K)；微CT在冻干过程（30 Pa，﹣20 ℃）中，升华界面逐渐向切块中心移动，孔隙率由最初的0.059增至0.252，对应的有效导热系数由0.695 W/(m?K)减小至0.123 W/(m?K)。 |
| 关键词: 冷冻干燥 有效导热系数 真空度 孔隙率 |
| DOI： |
| 投稿时间：2017-11-22
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| 基金项目:国家自然科学基金(51576132)资助项目。 |
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| Experimental Study on Effective Thermal Conductivity of Banana during Freeze-drying Process |
|
Ding Baosen1,2, Xu Yi1, Liu Daoping2, Guo Baisong3
|
| (1.Institute of Refrigeration and Croygenics, University of Shanghai for Science and Technology;2.Institute of Biology Thermal Science & Thermal Science, University of Shanghai for Science and Technology;3.Shanghai Tofflon Sci & Tech Co., Ltd.) |
| Abstract: |
| The study took banana as the research object to achieve precise thermal control of freeze-drying process and improve the quality of freeze-dried products. Specifically, the effects of pressure (10, 30, 50 Pa) and freeze-drying temperature (﹣20, ﹣30 ℃) on effective thermal conductivity in the complete banana freeze-drying process were investigated based on the model of steady state heat flux. The sublimation process inside the banana was observed and analyzed by micro-CT scanning, and the relationship between porosity and effective thermal conductivity was also discussed. The results indicate that the effective thermal conductivity increases from 0.036 W/(m?K) to 0.072 W/(m?K) with the increase in the pressure from 10 Pa to 50 Pa. Additionally, the primary drying temperature increases from ﹣30 ℃ to ﹣20 ℃, and the corresponding effective thermal conductivity decreases from 0.084 W/(m?K) to 0.058 W/(m?K). During the freeze-drying process (30 Pa, ﹣20 ℃), the sublimation interface gradually moves to the center of the banana dice, the porosity increases from 0.059 to 0.252, and the corresponding effective thermal conductivity decreases from 0.695 W/(m?K) to 0.123 W/(m?K). |
| Key words: freeze-drying effective thermal conductivity vacuum porosity |
