基于DEM-CFD的粮堆气流阻力与传热特性模拟研究

DEM-CFD Simulation of Airflow Resistance and Heat Transfer Characteristics in Grain Bulk

谷物固定床干燥是测定通风过程中谷物温湿度变化、气流阻力规律的常用方法,在固定颗粒床中孔隙分布对粮堆气流阻力与传热特性影响明显。本研究采用离散单元法(DEM)模拟了大豆颗粒随机堆积的孔隙结构,并对堆积颗粒间的接触进行处理,利用DEM-CFD方法模拟了大豆固定床中的气流阻力与传热特性。结果表明:粮堆压力降与入口速度近似呈二次函数关系,与考虑壁面效应的Reichelt方程计算结果一致。固定床层内部速度与温度场分布不均匀,受床层孔隙率分布、入口风速影响较大,近壁面区域气流速度与降温速度均高于床层中心区域。

Grain fixed bed drying had been a universal method to evaluate the grain temperature and humidity changes and airflow resistance during the ventilation process at present. The porosity distribution in the fixed bed showed a significant effect on the airflow resistance and heat transfer characteristics of the grain bulk.In the present study, the discrete element method(DEM) was used to simulate the pore structure of the soybean kernel randomly stacked, and construct the contact between the stacked particles. The DEM-CFD method was used to simulate the airflow resistance and heat transfer characteristics in the soybean fixed bed drying.The result showed that the relationship between the pressure drop and the inlet velocity was approximately a quadratic function, consistent with the result of the Reichelt’s equation after considering the wall effect.The velocity and temperature field of the fixed bed were unevenly distributed, which was significantly affected by the porosity distribution of the bed and the inlet air velocity. The air velocity and temperature decrease in the area near the wall were faster than the central area of the bed.