具有吸湿和呼吸特征的仓储粮堆内部热湿耦合传递机理研究

Temperature and moisture are the two most important factors governing the safety of cereal grain during storage. In order to understand the law of temperature and moisture change in stored grain,it is essential to research the mechanism of heat transfer and moisture migration in bulk storage grain under different climatic conditions.. Most of the previous research of moisture migration and heat transfer used thin layer drying model.Unlike grain drying,moisture migration occurs in a closed grain silos with a restricted circulation of air.Therefore,the intergranular air is generally in thermodynamic equilibrium with the adjacent grain.The respiring and hygroscopic nature of cereal grain in combination with natural convection developed by the temperature gradient due to seasonal variations in ambient temperature, play a key role in the moisture migration and heat transfer process in stored grain. The heat of adsorption/desorption,the non-linear nature of sorption isotherm, heat and moisture generation due to respiration are some of the factors,which make the moisture migration and heat transfer problems coupled and nonlinear. . The overall goal of our research is to reveal the mechanism of coupled heat and moisture transfer in respiring and hygroscopic stored grain by means of theoretical analysis, numerical simulation and experimental investigation.Major emphases of this work will be on:. 1.Developing a innovative experimental method of moisture adsorption/desorption of cereal grain which is not static but dynamic method,and investigating the thermal properties of adsorption/desorption of grain by means of the dynamic method, and revealing the nature of moisture diffusion and the correlation of heat transfer and moisture migration.. 2.Based on the theory of cereal grain respiration, developing experimental systems for the measurement of respiring heat and moisture, and analysing the effect of grain respiration on heat and moisture transfer processes.. 3.Developing a mathematical model and its numerical simulation of heat and moisture transfer in respiring and hygroscopic grain by incorporating the sorption isotherm directly in it and reflecting the effect of temperature gradients and grain respiration on moisture migration and heat transfer through the source term.. 4.Conducting experimental observation on the change of temperature and moisture in grain storage bin under the certain climatic conditions,and testing the validity of the numerical model with the experimental results,and applying the model to predict patterns of moisture and temperature resulting from moisture migration and heat transfer under winter and summer storage conditions.

本项目从局地气候条件、谷物吸湿/解吸湿和呼吸作用对仓储粮堆内部热湿传递过程的影响入手，通过理论分析、数值模拟和实验研究，着重考察由于气温季节性变化而产生温度梯度时具有吸湿/解吸湿和呼吸特征的仓储粮堆内部热湿耦合传递机理。本研究突破传统谷物静态水分吸附/解吸附实验方法，拟采用动态水分吸附/解吸附实验探究谷物吸湿/解吸湿热力学特性、热湿效应和湿热效应，建立粮堆内部热湿耦合关系；并基于谷物呼吸理论发展粮食呼吸实验研究方法，探究粮食呼吸强度、呼吸热和释放水分对粮堆内部热湿传递过程的影响规律。根据多孔介质局部热质平衡原理和宏观体积平均方法建立具有复杂热源和湿源的深层粮堆内部热湿耦合传递的数学模型，通过数值模拟和实验观测研究，分析仓外不同气候条件下粮堆中温度和水分的动态变化规律，揭示粮堆内部热湿耦合传递机理。研究内容体现多孔介质传热传质与谷物科学的交叉，研究成果有望为粮食储藏的科学管理提供理论依据。

储粮生态系统中，粮仓内部的温度和湿度是储粮中害虫、霉菌等生物生存和发展的重要条件，是粮食发热、霉变的主要影响因素。探索局地气候条件下粮堆内部的热湿耦合传递机理，分析仓储粮堆内部温度和水分变化规律，是控调储粮生态系统状态、保证粮食安全储存的理论基础。.本研究从局地气候条件、谷物吸湿/解吸湿和呼吸作用对仓储粮堆内部热湿传递过程的影响入手，通过理论分析、数值模拟和实验研究，揭示了由于气温季节性变化时具有吸湿/解吸湿和呼吸特征的仓储粮堆内部热湿耦合传递机理，获得了局地气候下仓储粮堆内部温度和水分的变化规律，为防止粮食储藏过程中的发热霉变奠定了基础。.通过谷物动态水分吸附/解吸附实验，获得了谷物吸湿/解吸湿热力学特性及粮堆内部热湿耦合关系；基于多孔介质局部热平衡原理和宏观体积平均方法建立并验证了具有复杂热源和湿源的深层粮堆内部热湿耦合传递的数学模型；通过数值模拟和实验观测研究，分析了仓外不同气候条件下仓储粮堆中温度和水分的动态变化规律。基于仓储粮堆热湿耦合传递规律的分析，提出了预防储粮结露、发热霉变的技术方案。.已发表论文30篇，已录用待发表论文3篇，参加6场国际国内学术会议，进行了2次国际学术访问和合作研究。