【摘要】 采用微CT扫描仪的扫描成像,图像重构及灰度值分析技术对不同厚度苹果片冷冻干燥的升华过程进行实验观察,分析了界面的移动特性。结果表明,对于单面传导加热的升华干燥过程,物料升华不仅在顶面进行,与搁板接触的底面以及侧面也会有水蒸气逸出．厚物料在升华过程中有一个明显的球形冻结区,升华界面呈三维模式逐渐向物料几何中心收缩．无论物料厚薄,刚开始升华干燥速率比较快,随着干燥层的增厚,升华过程的热质阻力增大,升华速率减慢．更多还原

【Abstract】 In this study,to apple slices with different thickness,Micro-CT scanning、image recon- struction and the technique of grey value analysis were used to observe the sublimation process of freeze-drying and analyze it’s moving characteristic.The results show that,to the sublimation process with single surface’ heat conducting,the sublimation is not only in upper surface,but in under surface contacting with shelf and side surface.A spheral frozen area exists in thick samples during sublimation obviously,and the sublimation interface shows as a three-dimensional moving mode and contracts to the geometric centre of the sample.No matter the sample is thick or thin,sublimation rate is quick at first.Along with dried area thickening,resistance for heat and mass transfer increases,sublimation rate becomes slower.更多还原