Simulation Of Continuous Drying Process For Germinated Brown Rice And Design Of Microwave Dryer

In order to improve the drying uniformity and ensure quality of germinated brown rice(GBR)in a continuous microwave dryer,according to the actual production needs of germinated brown rice,the size of the drying chamber for the continuous microwave dryer is determined to be 1220 mm ? 1220 mm ? 10000 mm.The electromagnetic field distribution in the drying chambers of different structures was simulated and analyzed by using HFSS electromagnetic simulation software.The SolidWorks Flow software was employed to study on distribution law of air flow in a dry chamber.The drying characteristics of germinated brown rice were investigated by bench test during microwave drying,and the simulation results were verified.Based on the above research results,the microwave dryer was optimized and designed.The main contents and conclusions are as follows:(1)The internal electromagnetic field in the drying chamber under different conditions(including load and load free,magnetron arrangement and side angle transition)was simulated and analyzed by using the developing a simulation model of microwave electromagnetic field.The vertical distribution of magnetron and vertical corner of drying chamber can contribute to improving the uniformity of material surface field distribution in the microwave drying process of GBR.The magnetron was evenly arranged in the upper part of the drying chamber,909 mm in the length direction of the drying chamber,and 406 mm in width direction.Therefore,when the structure and design of the microwave dryer are optimized,the configuration of the magnetron and the corner transition of the drying chamber are adopted.(2)A fluid simulation model for drying chamber of microwave dryer was established,and the airflow distribution in different drying chambers was simulated and analyzed.The results showed that the air duct is installed on the inlet air inlet of the microwave dryer and the air vent is added on the end face of the outlet,which can make the air flow more stable in the cavity.The stable wind speed area accounts for 45%,and the flow loss of the inlet gas can be reduced.The outlet is set at 320 mm from the top of the drying chamber,and the size is 800 mm ? 1220 mm ? 200 mm.The corner of the drying chamber avoids round transition,which can reduce the airflow vortex in the chamber and improve the efficiency of airflow utilization.(3)During microwave drying,proper ventilation in the drying chamber caused convection on the surface of GBR,which could improve the uneven distribution of the temperature distribution of the material surface caused by the uneven distribution of the electromagnetic field,and remove water vapor from the surface of the material to improve drying speed.But theburst rate also increased with the increase of ventilation rate,which affected the quality of GBR after drying.Considering the drying efficiency and dry quality,the reasonable ventilation speed for GBR microwave drying was in range of 0.2~0.5 m/s.(4)According to the results of simulation,drying experiment and design requirement(wet material handling capacity of 500 kg/h),a continuous microwave dryer was designed.The overall structure of the continuous microwave dryer was determined,and the structures and parameters of the main parts of the dryer were developed.Moreover,the arrangment of the magnetron and the structure parameters of the drying chamber were obtained with a control system.The microwave dryer has the continuity and automation of the drying process to improve the drying efficiency and the quality,which provide a reference for the design of the continous microwave dryer for the granular materials such as germinated brown rice.