Study On Heat Transfer Mechanism Of Low-Temperature Grain Storage In Cold Areas

Food is the fundamental relationship to human survival,food security is crucial,high quality,high quality storage is also very important.Heilongjiang province is a big grain producing province,and the grain storage problem should be more attention to.General rice initial moisture content is high,need to dry to moisture content of 13.5%to safe storage,but some nutrients in the drying process will be lost due to high temperature,and rice suitable for processing moisture between 15%and 17%,in this interval processing performance,the rice rate is high,so can reduce the drying temperature,shorten the drying time or not drying,storage high moisture of rice.However,high moisture rice is not stable in the storage process,so storing high moisture rice at low temperature is an important means to achieve safe and high quality storage.The temperature of traditional low-temperature storage of rice and other grains is mostly above 0℃,and there are few studies on the storage of high water rice below 0℃ to inhibit its respiration.Therefore,this paper uses the horizontal ventilation in the early stage to cool the rice in stages,and the static sealed storage in the later stage until the external environment can directly cool the granary for ventilation,so as to realize the purpose of safe storage of high water rice at low temperature.Two important indicators to measure the safety of rice storage are the water and temperature inside the grain stack.This paper uses the method of combining experiment and simulation to study the distribution rules of temperature and humidity in the grain reactor in the phased cooling process and static storage process,verify the accuracy of the simulation,and analyze the cooling process of the grain reactor under different conditions in the tall barn.The main contents are as follows:Construct a physical model of horizontal ventilation and cooling for rice piles in tall houses,propose the theoretical basis of horizontal ventilation and phased cooling,construct a static storage model,discuss the temperature and humidity distribution and the transfer mechanism of water and heat,and determine the parameters of rice and wet air for the numerical simulation study of the phased cooling process and static sealed storage process.The experiment of ventilation process and static storage process of small grain reactor was carried out to explore the change law of temperature and humidity of different positions of grain reactor under different air inlet speed and different air supply temperature difference.Considering the rice heap as a porous medium,based on the theory of heat and water transfer of the porous medium,and considering the effect of rice particles and its respiration,the coupling mathematical model of rice in the ventilation process and static storage process is constructed.Comparing the simulated data with the experimental "data,the change trend of temperature and humidity is basically consistent,which verifies the correctness of the mathematical model.Combined with the freezing point and breathing curve of rice,choose the appropriate minimum ventilation temperature,using the simulation software of tall bungalow barn rice in different air temperature difference,different inlet air speed and under the condition of different air humidity,transverse ventilation phased cooling simulation,analysis of different moment the internal temperature and humidity distribution cloud figure.After the ventilation of the grain stack,the static sealed storage simulation is conducted to analyze the temperature field distribution of the grain stack before and after the static storage.It was found that the horizontal ventilation of the grain reactor in stages could effectively cool the high-moisture rice.During the static storage process,the internal temperature of the grain reactor increased slightly,but the temperature changed little,indicating that the low temperature can effectively inhibit the respiration of the high-moisture grain.In conclusion,it is possible to use transverse ventilation to cool down in stages for rice to inhibit its respiration,and then conduct static sealed storage to store high-moisture rice at low temperature.In addition,in the simulation process of tall barn,the cooling situation of rice grain heap under horizontal ventilation is analyzed,and the data of the phased cooling process is sorted out,which can guide and predict how to conduct the phased cooling of high-moisture rice in the physical storage in the future.