Experimental And Simulation Study On Temperature And Humidity Distribution Of Grain In Circular Silo Under Automatic Classification

Circular silos are widely used in ports as transfer silos because of their advantages such as land saving,good sealing performance,easier for mechanized operation and fast turnover.Steel silos and reinforced concrete silos are in the majority in port silos all over the world.In the process of grain storage in steel silo,solar radiation on the vertical silo wall and the distribution of impurities in the grain bulk have great influence on the thermal environment of the silo.Compared with flat warehouses,the external-heat-caused temperature rise of the grain bulk in the vertical silo mainly comes from the vertical wall other than the roof.Due to the low thermal conductivity of grain,the grain bulk is easy to show a phenomenon of “hot skin and cold core” with the change of environment temperature.When the steel circular silos are arranged in multiple rows,the thermal environment in each silo in during the grain storage process is different because they are located in different positions in the silo group,that is,the solar radiation intensity on each silo is different.When the grain is loaded in the circular silo,impurities in the grain bulk gather automatically,resulting in the automatic classification of the grain bulk.The distribution of impurities under automatic classification is also an important factor affecting the thermal environment in the silo.For the circular silo,without some devices to guide and arrange the grain bulk,automatic classification cannot be avoided when grain is put into the warehouse.If a large amount of impurities gathered on the vertical wall of the silo,the thermal environment of grain bulk will be influenced under solar radiation in hot season.In this study,the steel grain silo storage experimental platform was built,and the grain bulk automatic classification experimental silo and non automatic classification silo were set up together.According to the different radiation intensity of the vertical silo wall in all directions,graphene infrared radiation film was used to conduct controllable and constant temperature heating on the silo wall.The experimental results indicate the cold center position and hot position of the bulk in the south corner and the middle of the south.The "cold center" area of the silo with automatic grading is larger,and the temperature distribution in the bulk is more uneven,which will increase the risk of condensation at the intersection between the cold and hot part of the bulk.Based on the experimental platform,a three-dimensional equal proportion mathematical model is established through ICEM CFD.The storage grain bulk is defined as porous media.The temperature of outside the silo wall and at the top of the silo are defined.By changing the porosity,thermal conductivity and other physical parameters of the porous media calculation domain at the side and center of the warehouse wall and the temperature outside the warehouse,multiple groups of calculation models are established and numerically solved in fluent.The effects of the distribution position of silos and the automatic classification of bulks in the silos were analyzed.The error between the simulation and experimental results is less than 15%.Finally,the hot part of the grain bulk of the circular silo greatly affected by the solar radiation in the group was determined,and a simulation under Zhengzhou typical meteorological conditions was carried out,which provided a reference for the subsequent experimental research for the radial ventilation and temperature control of circular silos.