仓储粮堆内部自然对流和热湿传递的数学分析及验证

本文基于仓储粮堆内部自然对流、热湿耦合传递的数学模型,采用数学分析的方法对模型中各个方程中的各项的物理意义和数量级大小进行了分析,探讨了仓储粮堆内部自然对流、热量传递和水分迁移过程的相互关系。提出了判断粮堆内部自然对流强弱的瑞利数及其影响因素,分析了仓型结构、粮种及仓外大气温度对粮堆内部自然对流、热量传递和水分迁移的影响,并通过数值模拟对数学分析结果进行了验证。结果表明,数学分析方法是分析仓储粮堆内部自然对流、热量传递和水分迁移过程的一种有效途径,数学分析的结果可以为仓型设计、储粮生态系统的模拟、仓储技术管理提供借鉴。

Approximate analysis and validation for natural convective heat and moisture transfer in grain bulk during sealedSstorage

Based on the theory of flow and heat mass transfer in porous medium, this paper established mathematical model of natural convection, heat and moisture transfer in grain storage. The relationship between natural convection, heat and moisture transfer processes and their influence factors were examined by the method of approximate analysis and numerical simulation. A condition for natural convection to influence the temperature and moisture is derived by an approximate analysis of the system and this condition is confirmed by detailed numerical solutions of the full equations. The analysis shows that for small cereal grains such as wheat, heat and moisture transfer is dominated by heat conduction and diffusion, but for larger particles the effect of convection is more important. The effect of natural convection is significant in stored bulk grain when the ratio of height to radii of bin or warehouse is larger. The moisture transfers that occur in storage have little effect on the average temperature of the stored bulk grain. However, heat conduction and natural convection dominates the moisture transport process. The temperature in stored bulk grain is affected by the ambient weather conditions. Respiration has an effect on temperature in stored bulk grain. The effect of natural convection is significant in stored bulk grain when the ratio of height to radii of bin or warehouse is larger.