Study On Improvement Of Uniformity Of Microwave Heating Based On Multi-physics Calculation

Microwave heating has the advantages of selectivity,rapidity,energy saving,and easy control over traditional heating methods,it has become a hot research topic in industrial applications.However,there is uneven heating during microwave heating,and hot spots and thermal runaway occur when heating certain chemical reactions,resulting in burning of reactants or destruction of reaction generators,or even causing explosions,hindering the widespread application of microwave energy.Multi-physics calculation is a common numerical method for studying microwave heating process.The core problem is the realization of full coupling calculation of different physics.In this paper,the multi-physics coupling calculation of the microwave heating fluid process is carried out,and the calculation results are verified experimentally.These work will provide a theoretical basis for experimental research and industrial applications of microwave energy.The main content of this paper is as follows:(1)The electromagnetic field equations,heat transfer equations,and fluid flow equations are couplling calculated using the frequency domain-transient solution step.The transient physical quantities of the interaction process between the electromagnetic field and the temperature field are solved.(2)The continuity of each physical quantity on the interface of the media is ensured by using the continuity boundary conditions of the assembly geometry and the consistent pair,and the problem of missing domain is solved by using the moving mesh technology.A fully coupled computational model which can reflect the disturbance to electromagnetic field caused by the change of temperature and position of the object is established.(3)It is proposed to improve the uniformity of heating by stirring.Through simulation calculations and experimental verification,the effect of rotation on the uniformity of microwave heating fluid is studied.The method of stirring is then proposed.The effects of different paddle types and paddle positions on the uniformity of heating by stirring are considered for the first time.The two-shaft paddles and anchored agitator are compared,and the height of the paddles is also considered.By these efforts,the best stirring conditrion for improving heating uniformity is seeked.