Design Of Screw Conveying Mechanism And Material Temperature Measurement System For High Frequency Electric Heating Sterilization Equipment

With the growing of the food safety issues,improving the quality of food production has become increasingly important.In this paper,the high frequency electric heating sterilization equipment was used as the research object.Particle swarm optimization(PSO)algorithm solves the optimized spiral blade parameters which were checked by numerical analysis software based on the sterilization of spices.In order to realize the material fluidization treatment,the design of the board structure on the spiral blade was carried out.In order to determine the parameters of the heating power supply,the electromagnetic field and the temperature field simulation of the spiral blade were completed.Combining the actual temperature field image of the spiral blade,the rationality of the simulation model was verified and the model boundary conditions were corrected.In order to avoid the interference of electromagnetic fields,platinum resistance electromagnetic shielding was carred out.For the purpose of ensuring the quality of the material after sterilization,material temperature detection system was designed.The main research contents and results are as follows:(1)Design of screw conveying mechanism for the high frequency electric heating sterilization equipment.The parameters of the spiral blade were calculated and optimized by PSO algorithm,and these were verified by simulation experiment.According to the actual needs,the main parameters of the spiral blade were determined: diameter D is 500 mm,pitch S is 200 mm,thickness b is 8mm,and effective height h is 115 mm.In order to realize the material fluidization treatment,the design of the screwdriver on the board structure was carried out.(2)Heating power supply parameter determination.The electromagnetic field and the temperature field simulation of the spiral blade were completed by COMSOL numerical analysis software.According to the results,when the excitation frequency is 20 kHz,the current density distribution in the spiral blade is ideal.And the temperature distribution which is similar to the current density,from inner to outer of the spiral blades,shows a declining trend.Based on both theoretical analysis and virtual simulation results,when frequency is 20 kHz and voltage adjustable from 0 to 36 V,a power supply could be acceptable for the sterilization temperature requirement,which is from 90 to 150?.And the type of power supply is a high frequency inverter switching power supply.(3)Simulation model validation.The temperature field image of the spiral blade was collected by the FLIR A615 on-line thermal imager,and the temperature compensation model of the spiral blade temperature field was established.The collected images were analyzed by HALCON digital image processing software development package.The radial distribution temperature which was extracted from the spiral blades were taken a temperature compensation.After comparing with the simulation results,the problems of the boundary condition for the simulation model were found out.The corrected simulated temperature field images were obtained after modifying the boundary conditions of the simulation model.The correlation coefficient,between the simulated analog value and the real value,is 0.959.(4)Material temperature detection system design.As strong magnetic field is generated during the process of the high frequency electric heating,the accuracy of temperature of material's critical control point(CCP)measured by platinum resistor would be influenced,which entails electromagnetic shielding(EM shielding).Based on COMSOL simulation,our research was intended to design the shielding device.The relationships between the shielding effectiveness and the relative permeability,relative conductivity and thickness of different materials were analyzed.It was found that a 2mm thick Mn-Zn ferrite ? shield would be the proper shield for platinum resistor.The shielding effect of this device prototype was proved to be acceptable by experiment.According to the actual temperature measurement requirements,LabVIEW temperature collection program and the temperature detection system design were completed based on the FLEX-4015 thermal resistance acquisition module.