Study On Heat And Mass Transfer Law Of Microwave Drying Of Rice And Optimization Of Control Method Of The Device

China has been one of the main rice planting regions with a long history since ancient times.With the advancement of agricultural modernization in China and the continuous progress of rice planting technology,the total yield of rice in China is still continuously increasing.Rice usually contains high moisture during harvest.If timely drying treatment is not carried out after harvest,rice with high moisture content is prone to problems such as spoilage,mold,and insect damage during storage,resulting in a significant reduction in the quality and commercial value of rice products.In addition,rice with high moisture content will undergo biochemical reactions to produce carbon dioxide and water during long-term storage,resulting in decreased quality and nutrient loss.Drying rice after harvest can effectively reduce the moisture content of the rice to a safe level,which helps to improve the storage stability of the rice and achieve long-term safe storage.The traditional drying methods for rice in China mainly include solar drying,wind drying,hot air drying,and other methods.They all use external heating to increase the temperature of the rice and accelerate the evaporation of water in the rice.By controlling the drying time and temperature,the moisture content of the rice can gradually decrease,ultimately reaching the standard of safe storage.Microwave drying is a modern food drying technology.Compared to traditional drying methods,microwave drying can directly heat the interior of rice.Its unique heat transfer method from the inside out makes microwave drying have many advantages such as faster drying speed,higher drying efficiency,and lower energy consumption.It is a very promising food drying technology.This article studies the mechanism of water transport in the microwave drying process of rice,validates the water transport model through simulation and experiments,and optimizes the structure of the microwave drying box and the control algorithm during the drying process.The specific content is as follows:(1)Equation and Numerical Simulation of Mass and Heat Transfer in Microwave Drying of RiceBased on the characteristics of water transfer during rice microwave drying,a water transfer equation using rice as a porous medium was established and its accuracy was verified.A simulation model for rice microwave heating was constructed,and the heat transfer process of rice microwave vacuum drying under different vacuum degrees was simulated.The changes in various parameters during the rice drying process were analyzed,The research results provide a theoretical basis for improving the efficiency of microwave drying of rice.(2)Experimental Study on Microwave Drying of Rice and Prediction of Moisture ContentDifferent microwave power,vacuum degree and heating time were selected to carry out the microwave vacuum drying experiment of rice.The traditional drying model and artificial neural network were used to fit the experimental data of rice microwave intermittent drying,and the fitting effects and accuracy of moisture content prediction of the two methods were compared.This provides a new method for real-time prediction of moisture content during the drying process.(3)Optimization of microwave drying equipmentBased on the microwave drying experiment and simulation analysis of rice drying,research is conducted on the structure and control algorithm of the microwave drying device.Simulation analysis was conducted on the influence of different microwave feed distribution modes of the cavity on the uniformity of the internal electric field in the drying device.Based on the simulation results,an optimization method was proposed to fit the existing control model of the rice drying device system.Two algorithms,PID control and fuzzy control,were used to optimize the device control mode,and the control effects of the two control modes were compared.