钢筋混凝土浅圆仓中大豆粮堆温度场的研究

Temperature field of soybean grain pile in reinforced concrete shallow round silo

为研究大豆在机械通风过程中的温度变化,以华北地区内径为30 m、装粮高度为20 m的钢筋混凝土浅圆仓为研究对象,基于多孔介质传热传质理论,利用数值模拟软件COMSOL建立大豆储藏过程中粮堆内部温度变化的数值模型,利用此模型对机械通风过程浅圆仓大豆粮堆温度场进行了分析,并预测了不同初始粮温和装粮高度条件下仓内粮堆温度变化过程。结果表明:随着与风道距离的增加,粮层温度变化幅度由剧烈逐渐变得缓慢;粮堆热阻的存在导致热量在整个粮堆的传递过程表现出一定的迟滞性,从而使整个粮堆温度分布不均;初始粮温分别为12、14、16、18、20℃时,机械通风86 h后仓内粮温分别降至4.9、6.2、7.3、8.4℃和9.6℃,分别下降了59%、56%、54%、53%和52%,在相同边界条件下,初始温度较低的粮堆,粮温降幅较大;机械通风过程,不同装粮高度(18、19 m和20 m)的粮堆温度变化差异呈现先增大后减小的趋势,在机械通风19 h和110 h后,装粮高度相差1 m时,粮堆之间温差分别为0.1℃和0.6℃,在机械通风结束后,仓内粮堆温度分别为0.3、0.5℃和0.9℃,此时装粮高度相差1 m时,粮堆之间的温差为0.2~0.4℃。综上,所建立的模型可对多种初始边界条件的钢筋混凝土浅圆仓大豆粮堆温度场进行预测。

In order to study the temperature'change of soybean in the process of mechanical ventilation,a reinforced concrete shallow round silo with a inside diameter of 30 m and a grain loading height of 20 m in North China was taken as the research object,and based on the theory of heat and mass transfer in porous media,the numerical simulation software COMSOL was used to establish numerical model of temperature changes inside grain pile during soybean storage.The model was used to analyze the temperature field of soybean grain pile in shallow round silo in the process of mechanical ventilation,and the temperature change process of the grain pile under the conditions of different initial grain temperature and grain loading height were predicted.The results showed that the temperature of the grain layer changed from violent to slow with the increase of the distance from the air duct.The existence of the thermal resistance of the grain pile led to a certain hysteresis in the heat transfer process of the whole grain pile,so that the temperature distribution of the whole grain pile was uneven.When the initial grain temperature was 12,14,16,18,20℃,after 86 h of mechanical ventilation,the temperature of the grain piles in the silo dropped to 4.9,6.2,7.3,8.4℃and 9.6℃,and decreased by 59%,56%,54%,53%and 52%respectively.Under the same boundary conditions,the grain temperature with the lower initial temperature had a larger drop in grain temperature.During the mechanical ventilation process,the grain temperature change difference at different grain loading heights(18,19 m and 20 m)showed a trend of first increasing and then decreasing.After the mechanical ventilation for 19 h and 110 h,the temperature difference between the grain piles was 0.1℃and 0.6℃when the height difference between the grain loading was 1 m;after the mechanical ventilation,the temperatures of the grain piles in the silo were 0.3,0.5℃and 0.9℃respectively,and when the height difference of grain loading was 1 m,the temperature difference between the grain piles was 0.2-0.4 C.In conclusion,the established model can predict the temperature field of soybean grain pile in reinforced concrete shallow round silo with various initial boundary conditions.