Simulation Of Multi-field Coupling And Transfer Processes In Stored Grain Within Shallow Silo Reactor During Ventilation

It is estimated that world food production will be lost by about 10% to 30% after harvest[1],and different countries will have different proportions in different years.The reason for this huge loss is very complicated.Food will be lost during harvesting,drying,transportation,storage,processing and sales.Among them,the major loss in grain quantity and quality occurred in the storage process,and the temperature and moisture content had the greatest impact during the storage process.After experimental analysis,when the grain temperature is less than 15°C and the moisture content is in the range of 12% to 12.5%,it is most conducive to maintaining the activity of grain particles,and it can also reduce the growth of microorganisms and slow the growth of pests,thereby reducing the loss of grain storage.Therefore,as one of the world’s largest food industry countries,maintaining the security of food is particularly important.Based on the theory of heat and moisture transfer in porous media,the momentum equations,energy equations and moisture conservation equations of the grain-cone bottom silo and shallow silo in column coordinate system were obtained by coordinate transformation.The control of boundary conditions was also obtained.And the use of meshing technology to generate the nodes of the numerical calculation,using the finite difference method solution,and the time difference of the forward differential technology,discrete partial differential form of the equation,the difference equation.The control differential equations and boundary conditions in the computational domain are separated by using a central difference approximation of the spatial derivatives.Using alternating direction implicit methods,Thmoas algorithm and explicit methods to solve the heat and mass conservation equations.Secondly,the paper studied the changes of physical fields such as temperature,humidityand moisture inside the grain reactor during the ventilation process,and also considered the physical and biological factors affecting the biological field within the grain,including: heat capacity,heat conduction,absorption rate,diffusivity,germination rate,respiratory rate and pest succession.The internal thermal mass transfer process and biological characteristics of the grain piles in silos and shallow silos were explored.The influence of solar radiation and surrounding atmospheric environment on the internal grain piles of the silo was also considered.Based on the Fortran program,the solution process was programmed and solved using a computer.The result of the operation is processed by using the Origin software to obtain a distribution cloud map of each field.A test rig was set up in Luzhong Grain Storage,using the temperature and humidity sensors inside the grain piles to collect the temperature at the measurement points inside the grain piles during the period of ventilation.The moisture data was measured by a cartridge type moisture quick detector and compared with the simulation results.The maximum temperature error between the numerical simulation and the actual measurement is 2.0 ℃(13)The error between the simulated and measured data of moisture content is 0.5% at the maximum,and the error is relatively small.This verifies the mathematical model in the article and the accuracy and practicability of the program.Finally,the numerical simulation analysis of the cross ventilation duct,the annular ventilation duct,and the combined(cross-ring type)ventilation duct was conducted,and the ventilation effects of the three ventilation systems were compared.The study found that the combined ventilation system is more uniform than other systems,which is conducive to reducing the temperature and water in the grain pile,reducing the loss of dry matter,and slowing the growth rate of insect populations.Therefore,this system is more conducive to grain storage.Finally,the internal temperature and moisture of grain in the grain warehouse of Luzhong grain store were simulated during the ventilation period,and the internal pressure,temperature,moisture,dry matter loss,and seed activity distribution maps were obtained.It is a scientific and efficient method to predict the change of temperature,moisture content and humidity as well as the change of biological characteristics by using computer programming in the actual granary ventilation.The results of this study are of guiding significance for rational design of ventilation schemes,reducing losses in grain storage,savinggrain storage costs and improving economic benefits.At the same time,the research results are also conducive to the improvement of granary design.