Study On Numerical Simulation Of CaO-SiO₂ System Materials By Microwave Heating

By Microwave (MW) heating technique is meant to generate heat through coupling between MW and corresponding media i.e. to heat materials into the required temperature by dielectric loss. MW heating technique has the advantages of rapid heating, even heating, high-efficiency, easy to control, safety and environmental protection etc. In its actual application, there are always a few difficulties for temperature measurement of MW heating body, especially for solid materials, because temperature-measured sensor would inevitably interference on either MW electromagnetic field or temperature field, somehow. Therefore, it is meaningful to pursue temperature vs. time during heating, more exactly.In modern engineering MW electromagnetic field, various numerical computation methods play more and more important role, in which the Finite-Difference Time-Domain Method (FDTD method) , is a very effective numerical computation method that has been developing since mid-1960s. The core of FDTD method is how to convert the Maxwell differential equations into difference equations in order to solve electromagnetic field, numerically. So far, the FDTD method has found its applications in many scientific fields.In the experiments, the material samples in the CaO - SiO₂ system were heated with MW apprantus, which has 2450 MHz in freqency and 1kW in power. The temperature measurements of sample surface were carried out with a Model ULTIMAX-20 infrared pyrometer made in Japan. The temperature measurements of sample body are taken with a method of liquid caloric temperature-measurement. According to characters of MW heating, this temperature-measurement method is based on heat-transmission and energy conservation. This method is easy to operate and has more credible measurement results. The measurement results may be taken as comparison between theoretical computational results and experimental results.The keynotes of how to solve temperature of media heated along time heated are as follows. Firstly, a suitable form of heat-conduction differential equation is chosen. Then, the heat-conduction differential equation is converted into a series difference equations about temperature by putting the grid joint on the center of Yee cell mentioned above. In solving these difference equations, some definite conditions, including initial conditions and boundary conditions, are required to be determined. Besides, for guaranteeing numerical stability, there is a time internals. However, because this restriction is much looser than the requirements in FDTD method, this problem is solves naturally.In this thesis, the corresponding MW electric fields and temperature vs. time are computed by computing the Maxwell's differential equations and heat-conduction differential equation (Fourier differential equation) for a special material. The computation results are compared with experimental results in order to show the feasibility and reliability of numerical computation above models.