微波辅助萃取的微波吸收系数与吸收功率密度

微波吸收系数和吸收功率密度是反映微波辅助萃取效率的两个重要参量,前者代表了溶液对微波能的整体吸收比率,后者代表了溶液中某一点处微波能转化为热能的强度.文中根据微波在介质中的传播规律,导出了微波吸收系数与溶液复介电常数间的关系式;并以微波与物质相互作用的基本原理为基础,导出了微波吸收功率密度与物质复介电常数以及空间位置间的量化关系式.所得结论可为微波辅助萃取中溶剂的选择以及特定溶剂中微波频率的选择提供理论参考.

Absorption Coefficient and Absorption Power Density of Microwave in Microwave-Assisted Extraction

The absorption coefficient and absorption power density of microwave are two important physical quantities to estimate the efficiency of microwave-assisted extraction.The former demonstrates the total proportion of microwave energy absorbed by the solution,and the latter represents the conversion strength of thermal energy from microwave energy at any space point in the solution.In this paper,on the basis of the propagation law of microwave,an expression of absorption coefficient is derived as a function of solution permittivity.Then,according to the interaction between microwave and solution,an analytical expression of absorption power density is also derived,which is a function of the permittivity and the space coordinates.The two proposed expressions provide theoretical guidance for the selection of solvents in microwave-assisted extraction and the selection of microwave frequency in a specified solution.