Numerical simulation on heat and mass co-transfer during microwave-assisted water extraction of icariin from epimedii leave
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 D_e. On the other hand, the model took internal porosity e as a function of extraction time t, which resulted in D_e 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.