小麦粮堆中热量传递特性研究

Study of heat transfer characteristics in wheat grain pile

采用人工加热的方法在小麦粮堆中形成明显的温度梯度,通过观察加热阶段和加热结束后粮堆内部的温度变化,探究小麦粮堆中热量传递特性。结果表明:加热过程整体粮温呈线性上升,距热源越近的位置温度上升速率越快,热量逐层传递,各层粮温变化成显著正相关,粮堆内部原"热皮冷芯"的现象被打破。全地板通风下不同横向距离处粮温变化不显著,不同纵向距离的粮温变化极显著(Ρ<0.01),热量平均传递速率约为0.087m/h。停止加热后平均粮温基本保持不变,但粮堆内部热量从高温区向低温区扩散,热量传递速率由(0.1~0.16)m/d逐渐降至(0.02~0.04)m/d并保持稳定。整个过程中中上层及上层粮温出现先下降再上升的趋势,表现出一定的滞后性。表面粮层受外界环境影响较大,变化较剧烈,同时粮堆水分变化不大,水分在温度梯度和热应力的作用下有向上扩散和渗透的趋势,但传递速率远小于热量的传递。

The heating experiment of wheat was operated in the test bin and pile formed a significant temperature gradient,by observing the change of temperature during the heating phase to explore heat transfer of stored grain pile.The results indicated that：The whole grain temperature rose linearly during the process of heating phase and the position which was near the heat source temperature rose faster.The process of heat transfer was layer by layer,each layer temperature changes had an significant positive correlation.The phenomenon that pile had hot serface and cold core was broken.Different lateral distances grain temperature did not change significantly by floor ventilation,but changed significantly in longitudinal distances（P〈0.01）,the average heat transfer rate was 0.087 m/h.Average grain temperature remained after stopping heating,but heat still transferred from the high temperature zone to the low temperature zone,the heat transfer rate decreased from（0.1-0.16） m/d to（0.02-0.04） m/d and retained stable.The upper and middle layer had a certain lag,temperature increased at first and then decreased.The grain surface temperature had a more dramatic changes influenced by the external environment.The mass change of the wheat pile was gentle,the mass transfer tended to spread and penetration up under the effect of temperature gradient and thermal stress,but the transfer rate was far less than the transfer of heat.