Study On The Coupling Law Of Heat-Wet-Force In Wheat Grain Bulk

Grain storage security is related to people's livelihood and national security.Temperature and moisture are important factors affecting safe grain storage.Grain porosity is a key parameter affecting temperature and moisture transfer in grain bulk.Due to the different heights of grain loading in the granary structure,the grain bulk are in a complex spatial stress state,and the porosity in different spatial locations is different,which directly affects the distribution of temperature and moisture inside the grain bulk and even affects the safety of grain storage.At present,there are few research results on the Heat-Wet-Force coupling of grain bulk,and the multi-field coupling theory is still not perfect.Therefore,the bulk wheat grain unit is taken as the research object in this paper.The effects of Heat-Wet-Force multi-field coupling law and temperature and humidity parameters on heat and moisture migration were studied experimentally.The main research contents are as follows.(1)Taking wheat as the research object,the wheat grain bulk was regarded as unsaturated porous medium,and the theoretical basis of Heat-Wet-Force in wheat grain bulk was analyzed.The frictional force on the wall affects the pore distribution of grain bulk,and then affects the temperature and humidity transfer of grain bulk.It is assumed that the main way of heat transfer during wheat storage is the convective heat transfer between the pores,the heat transfer between the micro-flow and the grain,and the convective heat transfer.The temperature gradient in the grain bulk will cause the moisture and moisture diffusion of the grain bulk.The convection of hot air in the grain bulk will cause the water in the grain bulk to stratify,and ignore the moisture diffusion of the grain in the grain bulk through the grain.(2)Based on the multi-field coupling theory and the law of heat and moisture migration of wheat grain bulk,a multi-field coupling experimental platform for bulk grain bulk was designed and constructed.And the stability test was carried out on different parts of the platform through experiments.The platform can effectively simulate the pressure field,temperature field and humidity field in the actual grain storage environment,and can accurately detect pressure,temperature and humidity.(3)Based on the multi-field coupling experimental platform of grain bulk,the experimental study on the Heat-Wet-Force coupling law of wheat grain bulk was carried out.The results show that the pressure and porosity of the wheat grain bulk,the temperature and humidity of different measuring points with the distance from the high temperature wall surface all satisfy the functional relationship.The greater the pressure on the grain storage,thesmaller the porosity in the grain bulk,and the slower the temperature transfer of the grain bulk.When the water on the wall of near-low temperature gathers to a certain extent,the water will migrate to the grain bulk.Influenced by the wall friction,the porosity of near-wall grain bulk is different from that of inside grain bulk,and the temperature and humidity transfer of mid-vertical grain bulk is different from that of near-wall grain bulk.(4)Experiments on the effects of temperature and humidity parameters on heat and moisture migration of wheat grain bulk.The results show that when the grain temperature is higher than the temperature control wall temperature,the high temperature region inside the grain bulk is continuously reduced in the ring shape under the temperature difference.Due to the difference in temperature difference between the grain bulk and the temperature-controlled wall,there is a difference in the migration rate of moisture from the interior of the grain bulk to the temperature-controlled wall,and a low-humidity zone is formed in the middle of the grain bulk.A small amount of moisture in the high-humidity grain bulk migrates to the high-temperature wall.