Abstract: This work has performed a numerical simulation of the temperature field during microwave heating of polyolefin-absorber mixture by means of a combined electric and thermal model. A finite difference time domain was used to model the electric field distribution within the cavity, while the finite difference method was used to calculate the temperature field distribution in different reactors. This study has focused only on the process from room temperature to 500 K for reducing heating time and energy consumption. This temperature range is a process with high energy consumption, difficult to control and great influence on the follow-up reaction. Temperature dependence of dielectric properties and thermal properties of heated materials are fully considered and simulated through an iterative process. The simulation results show that input power, the size and location of the heated materials, the position of the waveguide, and the kinds of microwave absorbers are important factors affecting the heating process. As a result, the uniform temperature distribution (the temperature difference T_d < 10 K) can be achieved by choosing the appropriate input power (500-2000 W), the appropriate proportion of microwave absorber (the volume ratio of SiC to HDPE is 30:70), and combining with the moving and rotating of the heated materials. The uniform temperature field obtained without mechanical stirring is very important for reducing energy consumption and subsequent reactions.

Key words: Microwave heating, Temperature field, Finite difference time domain, Finite difference method

摘要： This work has performed a numerical simulation of the temperature field during microwave heating of polyolefin-absorber mixture by means of a combined electric and thermal model. A finite difference time domain was used to model the electric field distribution within the cavity, while the finite difference method was used to calculate the temperature field distribution in different reactors. This study has focused only on the process from room temperature to 500 K for reducing heating time and energy consumption. This temperature range is a process with high energy consumption, difficult to control and great influence on the follow-up reaction. Temperature dependence of dielectric properties and thermal properties of heated materials are fully considered and simulated through an iterative process. The simulation results show that input power, the size and location of the heated materials, the position of the waveguide, and the kinds of microwave absorbers are important factors affecting the heating process. As a result, the uniform temperature distribution (the temperature difference T_d < 10 K) can be achieved by choosing the appropriate input power (500-2000 W), the appropriate proportion of microwave absorber (the volume ratio of SiC to HDPE is 30:70), and combining with the moving and rotating of the heated materials. The uniform temperature field obtained without mechanical stirring is very important for reducing energy consumption and subsequent reactions.

关键词: Microwave heating, Temperature field, Finite difference time domain, Finite difference method