The Research Of The Uniformity Of FEM-based RF Heating

The use of a new heating technology,which is called Radio-frequency heating,is increasingly arising.The energy generated by RF accelerated objects inside the polar molecule to high-speed movement,frictional heat produced thermal effects.This kind of heating possessed good penetration,which means heat internal and external parts of the object at the same time,reducing the heating time greatly and improving the heating efficiency.In addition,RF heating food neither produce soot,carbon monoxide and other harmful substances,or not to break the nutritional content of food at maximum extent,it truly be in line with the modern concept of healthy eating.According to a number of previous researches and practices,RF heating is a popular technology because of its superior characters such as excellent uniformity,no chemical pollution,high efficiency of sterilization pest control,and no damage to molecular structure of the original substance,compared to conventional heating and microwave heating.It can be seen that application of RF heating in agricultural commodities,food drying,and pest control will be prosperous.However,non-uniform heating is the fatal flaw in the development process of radio frequency(RF)heat treatments for pest control and other applications.Unsatisfied results caused by unappropriate operating parameters of RF heating process would lead to varying degrees of damage to exterior shape and interior quality of food.The main reason is that the presence of a variety of problem,including shapes and sizes of materials,dielectric characteristics,the relative position of the plate,the plate voltage,the plate structure of the system and so on.This paper describes how the RF heating works,the advantages and development process in the field of agricultural commodities and food.After in-depth study of RF heating mechanism,it seems that the main factors affected the uniformity of RF heating is the distribution of electromagnetic field and the dielectric properties of the material.On the basis of theoretical research,COMSOL Multiphysics based on the finite element method(Finite Element Method,FEM),is used to establish a set of electromagnetic-thermal coupling simulation modeling method,the parameters for RF heating uniformity was obtained through the simulation model.The main steps are followed:First of all,analyze the relevant parameters of RF heating and measuring methods of these parameters.In this article,wheat flour is chosen as a sample for its common and representation.The dielectric and thermal properties of the wheat flour were measured experimentally.Then,after established electromagnetic-thermal coupling model,COMSOL simulation was used to derived temperature profile.The experimental temperature profile was obtained from actual measurement of the sample.The simulation and experimental results were compared with each other to analysis error and verify the correctness of the model.Finally,use COMSOL Multiphysics software to make model simulationand and observe the dielectric constant and loss factor of RF heating uniformity.Change the shape of the material,the position and voltage of the plates,and observe the RF heating uniformity in order to obtain optimal system parameters.