不同运行参数下平房仓粮堆表层控温系统的隔热性能试验

Thermal Insulation Performance Test of the Temperature Control System above Grain Bulk in a Single-storey Warehouse under Different Operating Conditions

该研究以粮食平房仓为研究对象,建立了粮堆控温试验系统,进行了不同工况下的隔热试验,研究在炎热气候下影响系统隔热效果的因素。结果表明:粮堆由外界传入热量引起的温升集中在装粮线以下10 cm的表层粮堆,粮堆表层控温系统可以有效减少外界突发高温对于表层粮温的影响,最优工况下,表层粮堆温度降低1.67℃。在送风温度、风速和层间高度诸因素中,系统送风温度对粮堆表层温升影响较大,而系统送风风速与层间高度影响较小。工程中可采取低风速、低风温的送风形式,使吨粮单位成本降低至5.6元,同时可减少能源消耗。由特征长度定义的努谢尔特数(Nu=hl/λ)表示了系统换热的强弱,无量纲过余温度Θ位于0.4~1时,Nu随Θ的增加而增加,变化范围为45~85。Nu受无量纲高度H影响不大,当H位于0.05~0.09之间时,Nu的变化范围仅为82~89。试验期间送风温度22℃,靠近系统上表面的仓内空气湿度与初始值相比下降13%,高于外界湿度5%,粮堆内部未发生结露情况。

A single-storey grain bulk warehouse was used as the research object,and a temperature control test system above the grain bulk was set up for a variety of thermal insulation experiments under different working conditions,to investigate the factors affecting the insulating effect of the system in hot climates.The results showed that the temperature rise of the grain bulk caused by external heat mainly occurred to the grains on the grain bulk surface 10 cm below the grain loading line.The surface temperature control system of grain bulk reduced effectively the impact of sudden high external temperature on the surface grain temperature.Under the optimal conditions,the surface temperature of the grain bulk was reduced by 1.67℃.Among the influencing factors such as inlet air temperature,inlet air speed,and interlayer height,the inlet air temperature exhibited a greater impact on the surface temperature rise of grain bulk,compared with inlet air speed and interlayer height.In the actual projects,low air speed and temperature were used to decrease the unit cost to 5.6 yuan/ton grain while reducing energy consumption.The Nusselt number(Nu=hl/λ)Nu was used to define the heat transfer performance of the system,with the dimensionless temperatureθin the range of 0.4~1.Nu increased(between 45 and 85)withΘ,but was not affected greatly by H(Nu in the range of 82~89 when H increased from 0.05 to 0.09).During the tests with an inlet air temperature of 22℃,the air humidity close to the upper surface of the system inside the warehouse was reduced by 13%compared to the initial value,which was 5%higher than the humidity outside,with no condensation occurring in the grain bulk.