冷冻干燥中升华过程界面的微CT观察及气固相变分析.pdfVIP

低温与超导 制冷技术 Cryo. Sup ercond. 第 35卷 　第 1期 R efrigeration Vol. 35　No. 1 冷冻干燥中升华过程界面的微 CT观察及气固相变分析 肖鑫 ,陶乐仁 ,徐振立 ,习德成 ,华泽钊 (上海理工大学低温生物医学技术研究所 , 上海 200093) 摘要 :采用微 CT扫描成像 、图像重构及灰度值分析技术对冷冻干燥中升华过程界面及气固相变进行实验观察与分析 。 采用高斯误差函数拟合 ,计算得到冰的平均灰度值为 154。在后续灰度值比价分析中 , 固体物料苹果本身的灰度值高于冰的 灰度值 ,从而可以分析冰晶的移动特性 。从直接扫描图像和重构图像 ,均可看到升华界面的移动是一个立体的移动 , 由它所 包裹的冻结区逐渐向物料几何中心收缩 。对比冻结物料和冻干物料的灰度值曲线 ,可见刚开始灰度值较低的冰区 ,在冻干结 束后变成灰度值相对较高的孔疏区。 关键词 :冷冻干燥 ;升华过程 ; CT;相变 M icro - C T ob serva tion on sublim a tion in terface and ana ly sis on ga s - solid pha se tran sform a tion of sublim a tion process dur ing freeze - dry ing X iao X in, Tao L eren, Xu Zhen li, X i D echeng, Hua Tsechao ( In stitute of Cryob iological and Cryom edical Techno logy, Un iversity of Shanghai for Science and Technology, Shanghai 200093, Ch ina) A b stract: In th is study, M icro - CT scann ing、im age recon struction and the techn ique of grey value analysis were u sed to analyze inter face and p hase tran sform ation during sub lim ation of freeze - drying. The m ean grey value of ice is 154 u sing simu lation of gau ss error func tion. In the follow ing contrastive analysis, the grey value of m aterial itself is h igher than the ice, so the moving characteristic of ice cou ld be analyzed. Not on ly from direct scann ing im ages bu t from recon struction im ages, we cou ld see that the movem ent of sub lim ation interface wa s a three - dim en sional move mode, it contracted to the cen tre of the m aterial. Comp aring frozen m aterial w ith freeze - dried app le, the ice are a w ith low grey value in the beginn ing becam e the loo se