Fluid Flow and Heat-moisture Coupling Transfer in Rice Drying Process Based on Grain Stack Scale
Grain quality is greatly affected by drying conditions and dry mass loss during drying should be mini-mized.In this study,the discrete element method and computational fluid dynamics method were used to construct a grain pile composed of rice grain.Based on the principle of fluid-solid coupling heat and mass transfer,a heat and moisture transfer model was established.By controlling the drying temperature and initial moisture content of rice,the variation law of temperature and moisture content in rice pile during drying was discussed.The numerical solutions provide an insight into the fluid flow and coupled heat and humidity transfer inside the grain pile during drying,and the effects of temperature and humidity on drying are discussed.The results show that the non-uniform pore structure of grain pile and the gap on rice surface lead to complex airflow patterns,resulting in the formation of"ventilation dead zone".Temperature and humidity differences between different grain layers were observed throughout the drying process.Due to the effect of water diffusion coefficient,there are differences in water content inside and on the surface of rice.The heat and moisture in the grain pile are transferred from the bottom layer to the upper layer by the flow of heated air and the heat and moisture diffusion of the rice.At the same time,it is found that the curvature of the drying curve changes with the change of drying conditions,especially when the temperature reaches 60℃.This study can provide reference and theoretical basis for safe storage of grain.
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