Research On Multiphysics Of Solid-state Source Microwave Oven

During the decades since the invention of the microwave oven,the microwave heating technique has been applied to broad areas,ranging from the highly demanding physical and chemical process to commercial and industrial equipment which has been practiced by consumers.Despite the exciting developments in microwave heating,the dependence on magnetrons has not been changed.Because of the microwave oven driven by magnetron working at a single frequency,more resonant modes are not excited in the cavity,which causes a poor heating uniformity.However,the recent rapid growth of the semiconductor industry in development of high-power microwave source has opened a new promising avenue by full electronic control over the electromagnetic field towards improve the microwave heating performance.In this paper,the Multiphysics simulation method was applied to study the multifrequency microwave heating of solid-state microwave oven and the temperature stratification in liquid heated by microwave.And the contents are as followed:1.Depending on a solid-state microwave oven,a three-dimensional geometric model was built using the multi-physics simulation software COMSOL.And based on this geometric model,the related material parameters,boundary condition and optimal mesh size was analyzed.Then the coupled electromagnetic and heat transfer model was achieved to simulate microwave heating of multiple chicken blocks with temperaturedependent dielectric properties.2.The electromagnetic-thermal simulation model and MATLAB script program were combined to research multi-Frequency heating of solid-state source microwave oven.And the microwave heating was simulated with different frequency-shifted rates increasing process and decreasing process between 2.4GHz and 2.5GHz.The simulated temperature distribution was validated by comparing with experimental temperature profiles obtained through a thermal imaging camera at the end of microwave heating.Therefore,except the distribution of the electromagnetic field,the heat transfer characteristics of heated load has a significant impact on the final temperature distribution for multifrequency microwave heating.3.The results demonstrated the decreasing frequency rate was higher than the increasing frequency rate and the fixed frequency heating.And a specific frequencyshifted rate decreasing process between 2.4GHz and 2.5GHz was proposed in improving the heating performance.4.An electromagnetic-fluid heat transfer model and the traditional bottom heating model were built to study temperature stratification in liquid heated by microwave.Then the process of heating a cup of water was simulated with microwave and traditional electric heater respectively.The simulation results were basically consistent with the experimental data and the temperature difference exceeding 11?.Through the analysis of experiments and simulation results,it is concluded that the electric field intensity at the top of liquid heated by microwave was always higher than that at the bottom,which resulted in only transverse convection instead of bottom-up convection in electric heaters.This unconventional convection resulted in the stratification of upper and lower temperatures in liquid.