Research On Heat And Humidity Coupling Characteristics Of Biomass Porous Media In Storage

The development of the country and the production and livelihood of people cannot be separated from food,so the safe storage of grain is very important.The grain stack itself is a small ecosystem,the survival and reproduction of all kinds of pests,molds and microbes are determined by the external environment outside the warehouse,the respiration of grain piles in the warehouse and the hygroscopic properties of the grain heap.When the external environment is too high and the humidity of the grain pile is too high,the respiration of the grain will accelerate,the temperature and humidity of the local area of the grain pile will rise,the pests and molds will multiply,the grain quality will go down.The temperature and humidity of grain can be reduced by ventilation,the law of grain temperature change and water migration in grain in the process of cooling and drying is studied in this paper.This paper combines theoretical analysis,numerical simulation and test verification to study the biomass porous media.The heat and humidity coupling process in the grain heap is explored in the process of ventilation,which considers the respiration process and has the hygroscopic moisture absorption characteristics of grain heap.The main contents are as follows.First,this paper introduced the research situation of grain storage transfer overseas,which is divided into two parts:the background of heat and mass transfer and heat transfer model,and the status of domestic research.The different research directions and methods at home and abroad are analyzed,and some theoretical basic knowledge of the storage of grain pile ventilation is introduced.Second,based on the theory of porous media heat and mass transfer,considering the breathing process and moisture absorption and desorption characteristics of grain heap,established the mathematical model of heat transfer and water transfer in the grain pile during the ventilation process.Third,on the one hand,taking the grain warehouse of a Provincial Grain Reserve Bank as the research object,a two-dimensional physical model is set up to simulate the horizontal ventilation mode,the average temperature data for the 12 days of ventilation is obtained.Shen Bangzao and others made experiments on the same conditions.The simulation data and test data are compared,the simulation temperature change trend and the test temperature change trend are consistent,and the accuracy of the model is verified,on the other hand,a three dimensional physical model is established for a national grain reserve warehouse.The vertical ventilation mode of the "U" air duct is simulated,and the data of the average temperature and the average humidity of the grain pile for 140 hours are obtained.Zhou Xinlong,Luo Xianan and others made experiments on the same condition,the simulation data and test data are compared.The changes of temperature and humidity are consistent with the experimental data,the accuracy of the model is further verified.Finally,the paper establishes a three-dimensional physical model and conducts CFD numerical simulation with the vertical ventilation of the "ten" type of tall buildings as the research object.This paper simulates the thermal and moisture coupling process of grain in different conditions,and obtains the temperature change and moisture migration cloud chart of grain pile under different working conditions,and explores the rule of heat and mass transfer under different working conditions of grain pile.