基于扩散模型的片烟增湿过程动力学分析

Dynamic Analysis of Strips Humidifying Process Based on Diffusion Model

为了研究片烟加工过程的吸湿过程及水分迁移速率,利用烟草热湿特性在线分析装置采用动态法考察了温度(60～80℃)和相对湿度(60%～90%)对B2F片烟增湿过程特性的影响,并在假设:①片烟内部均匀分布且各向同性,初始温度分布均匀;②忽略热、质传递过程中的耦合作用及片烟内部的温度差;③不考虑片烟增湿过程中发生的变形和膨胀效果,片烟厚度以均值L=3×10-4m代替;④增湿过程符合Fick第二定律的基础上,建立了能够描述温湿度影响的增湿过程动力学模型,最后选择了6组试验对修正后的动力学模型进行了验证。结果表明:①在同一温度下,有效扩散系数De随着相对湿度的增大而减小;在相同的相对湿度时,De则随着温度的增大而增大;②修正的动力学模型可以描述B2F片烟在高温湿度环境中的增湿过程,验证实验值与模型计算值吻合较好,相关系数R2大于0.95。

In order to study the absorption of strips and the migration rate of moisture in strips during processing, B2F strips were studied dynamically under a temperature range of 60-80℃ and relative humidity range of 60%-90% by an online device on the presumptions that： 1 ） The test piece is homogeneous and of even initial temperature; 2） Coupling effect and temperature difference in the test piece are negligible during heat and mass transfer process; 3） The distortion and expansion effects of the test tobacco during humidifying are ignored, and the thickness of the test tobacco is represented by its mean, 3 × 10-4 m; 4） The humidifying process follows Fick＇ s second law, the dynamic model of humidifying process, which describes the effects of temperature and humidity, was established ; the model was modified and verified. The results showed that： 1 ） At the same temperature, effective diffusion coefficient De decreased with the increase of relative humidity; while D increased with the rise of temperature at the same relative humidity; 2） The modified model could