微波辅助提取淫羊藿饮片中淫羊藿苷的热质同向传递数值模拟

Numerical simulation on heat and mass co-transfer during microwave-assisted water extraction of icariin from epimedii leave

建立了微波辅助水提过程热质同向传递的数学模型,模型中既考虑了体系内部温度梯度对扩散系数De的影响,也考虑了物料的孔隙率ε随提取时间t的变化,从而使De成为体系内部平均温度和提取时间t的函数;以淫羊藿饮片中淫羊藿苷的提取为代表体系,对提取模型一维平板的抛物线偏微分方程采用隐式差分法求解,得出饮片内部温度和淫羊藿苷浓度随饮片的厚度和时间的分布情况,结果表明:微波辐射的结果使饮片内形成由内到外的温度梯度,与传质方向一致;用溶剂主体中淫羊藿苷的浓度验证了模型的有效性,模型的计算值与实验值吻合良好,二者最大误差不超过10%.为验证模型,本文还对传统提取过程进行了模拟,取得了较好的结果.

A mathematical model combining heat transfer with mass transfer of MAWE of icariin from Epimidium sagittatum leaves was developed. On one hand the model considered the effect of temperature gradient on effective diffusion coefficient De. On the other hand, the model took internal porosity ε as a function of extraction time t, which resulted in De changing with the change of the average temperature of system and the extraction time t. The implicit difference method was used to solve the 1 D parabolic PDE（partial differential equation）. Distribution plots of temperature of material and concentration of icariin changing with the thickness of material and the time of extraction was drawn. The result showed that the temperature gradient was from the internal of material to solvent after microwave irradiation, the direction of temperature gradient and that of mass transfer was concurrent. The effectiveness of the mathematical model was verified by the concentration of icariin in solvent. The solutions of mass transfer model agreed with the experimental data. The biggest relative deviation of icariin concentration in liquid was less than 10%. In order to verify the model proposed in this paper, the traditional extraction process was also simulated,and the result showed good agreement between solutions of the model and the experimental data.