Temperature And Quality Of Rice In The Steel Silo By Simulated Solar Radiation

As a kind of fast construction,light weight and low cost granary,the steel silo is widely used in the field of grain storage.However,high heat transfer efficiency of the steel silo become fatal shortcomings of its application and development,and China's major grain producing areas in Jiangsu,Shandong,Hunan and other places,located in warm temperate and subtropicaLThe total solar irradiance of these places in summer is as high as 4900 W/m2,this is a serious challenge for the safe storage of steel silos.In order to study the variation of the temperature and quality of rice in the steel silo under the action of solar radiation,as well as the thermal insulation effect of anti radiation coated steel and double deck steel silos,in this paper,the constant radiation test,CFD simulation test and gradient radiationtest were carried out,the conclusions were as follows:1,The change trend of grain temperature in 5cm and 15cm grain layers was mainly related to the difference of temperature between grain layer and steel plate.The greater the temperature difference,the faster the warming trend,the change of grain temperature showed logarithmic trend.The smaller the temperature difference,the slower the warming trend,the change of grain temperature showed a linear increasing trend with smaller slope.In the stage of radiation,if the outside temperature was low,the phenomenon of grain temperature may decrease,the cooling rate was negatively correlated with the ambient temperature.The lower the temperature,the greater the cooling rate.2,25cm,35cm and 55cm grain layers in the constant radiation test and gradient radiation test grain temperature showed a rising trend slow,while 75cm grain layer temperature increased appeared obvious hysteresis.3,There was no significant difference between simulated and measured values,which confirmed that CFD could be used to predict the change of grain temperature in solar radiation test.After 72h radiation test,the YZ section of the three radiation conditions within the region of Y is 8?44cm,Z is 1?33cm,the local high temperature area with different area appeared.After the end of the 132h test,the temperature near the surface layer of the test steel plate is the highest,the cold core region appears near the wall that fecing the wall of the test plate.The size of cold core area is negatively correlated with the amount of radiation.4,The moisture content,fatty acid value,germination potential,germination rate,roughness rate and head rice rate of rice did not change before and after the constant radiation test.The worse the thermal insulation effect of the steel silo,the more obvious the decrease of rice moisture,the higher the fatty acid value of rice.5,Double layer steel warehouse and coated steel warehouse grain temperature increase was lower than single steel warehouse,and their average grain temperature growth rate was less than that of single layer steel silo.The results show the thermal insulation effect of double deck steel silo and coated steel sheet was better than that of single layer steel silo,and it was proved that the thermal insulation measures are necessary for steel silos.For double deck steel silos,the greater the distance between the plates,the better the insulation.Considering the cost of rice,coating and steel plate,it can bring economic benefits and reduce the loss of grain storage.In practical applicaton,the most economic measures should be taken according to the specific situation of the steel silo.6,Constant radiation test and gradient radiation test,the average growth rate of grain temperature per unit time was calculated with 24 h as a time node.It was found that the average growth rate equation of grain temperature was two yuan quadratic equation about time and grain thickness.The equation is V=a-bT-cS+dT2+cST-dST2,A,B,C,D are constants,V:heating rate(?/h);T:test time/h;S:grain thickness/m.As a result,the grain storage temperature affected by solar radiation is larger,and the appropriate heat insulation measures can reduce the loss of grain storage caused by the radiation heat effect,and bring economic effect.