微波干燥过程中氯化钠电磁特性数值模拟研究

Research on Electromagnetic Sensitivity Properties of Sodium Chloride during Microwave Drying

多模微波腔体是最为常见的加热腔体,然而在加热过程中待加热的物料常会表现出选择性加热的特点,这是由于微波加热的效果与物料的电磁特性参数密切相关。针对氯化钠在微波腔体中加热效果呈现出的差异性造成腔体内电磁场分布以及加热不均匀等问题,建立电磁热模型对氯化钠在加热过程中的电磁敏感性对温度变化的影响进行研究。通过时域有限差分法(Finite Difference Time Domain,FDTD)耦合求解电磁场及热场方程,对微波加热氯化钠的升温速率随着电磁特性参数以及氯化钠含水率变化的规律进行实时的仿真计算。结果表明:随着氯化钠相对介电常数的增大,其腔体内的电场分布越均匀,介质对电磁波的吸附作用越明显。随着氯化钠损耗角和含水率的增大,腔体内氯化钠的升温速率以及稳态温度增大。

The multimode resonant cavity is the most common heating cavity. The materials often show selective heating performance during the heating process due to the effect of microwave heating having a closely relationship with the parameters of electromagnetism. As the heating effect of sodium chloride in the microwave cavity results in electromagnetic distribution and uneven heating in the cavity, the electromagnetic-thermal field model is established to study the sensitivity of electromagnetic heating sodium chloride in the heating process. The electromagnetic field and thermal field equations are coupled by the method of finite difference time domain method(FDTD). The heating rate of microwave heating sodium chloride is simulated in real time with the electromagnetic characteristic parameters and the change of moisture content of sodium chloride. The results show that with the increase of relative dielectric constant of sodium chloride, the distribution of electric field in the cavity is more uniform and the absorption of electromagnetic wave by the medium is more obvious. With the increase of sodium chloride loss angle and moisture content, the temperature rise rate and the steady-state temperature of sodium chloride in the cavity increase.