基于孔隙尺度的辐射-自然对流耦合传热下高温球床堆有效导热系数研究

High temperature gas cooled pebble bed reactor (HTGR) is one of the advanced fourth generation nuclear reactors. The effective thermal conductivity of HTGR represents the macroscopic heat transfer ability. Because of the lack of pore-scale study, the understanding of inner relation of local pore-scale heat transfer characteristics and the effective thermal conductivity in high temperature pebble beds is obviously insufficient. Especially the effects of combined heat transfer of radiation and natural convection on the effective thermal conductivity is poorly studied. This research adopts the combined methods of numerical simulation, theoretical analysis and experimental research to investigate the effective thermal conductivity of high temperature pebble bed under combined heat transfer of radiation and natural convection. Based on the pore-scale numerical method, the effects of geometry, boundary conditions and physical properties are systematically analyzed to explore the coupled heat transfer mechanism of radiation and natural convection in high temperature pebble bed. Genetic programming and genetic algorithm are employed to establish the highly precise effective thermal conductivity correlations based on the numerical results. Experimental test is carried out to verify the numerical and theoretical results. The research results can provide theoretical guidance for safety design of HTGR, and are of academic significance to construct the theoretical system of heat and mass transfer in packed porous medium.

高温气冷球床堆是国际上先进的第四代核反应堆，其有效导热系数表征了球床堆芯的宏观传热能力。由于缺乏孔隙尺度层面的研究，高温球床堆局部孔隙传热特性与有效导热系数的内在联系认识还存在明显不足，尤其是孔隙内辐射-自然对流耦合传热对有效导热系数的影响规律研究相对较少。本项目拟采用数值模拟、理论分析和实验研究相结合的方法，针对辐射-自然对流耦合传热下高温球床堆有效导热系数进行研究。采用孔隙尺度的数值方法，系统分析几何结构、边界条件和物性等参数对高温球床堆辐射-自然对流耦合传热特性的影响规律，探索高温球床堆孔隙内辐射-自然对流耦合传热机理；在孔隙尺度模拟数据的基础上，采用遗传规划和遗传算法建立预测精度高的有效导热系数关联式，同时开展实验对数值模拟和理论分析的结果进行验证。研究结果不仅可以为高温气冷球床堆的安全设计提供理论指导，而且对构建颗粒堆积多孔介质热质传递理论体系具有重要学术意义。

高温气冷球床堆是国际上先进的第四代核反应堆，其有效导热系数表征了球床堆芯的宏观传热能力。由于缺乏孔隙尺度层面的研究，高温球床堆局部孔隙传热特性与有效导热系数的内在联系认识还存在明显不足，尤其是孔隙内辐射-自然对流耦合传热对有效导热系数的影响规律研究相对较少。本项目采用孔隙尺度的数值计算和实验测量方法，分析了高温球床堆辐射-自然对流耦合传热特性，阐释了辐射-自然对流耦合传热下球床堆有效导热系数的分布特性；揭示了辐射和自然对流对球床堆近壁面区域有效导热系数的影响规律，评价和改进了高温球床堆有效导热系数关联式，获得了预测精度高和可定量分析的有效导热系数关联式。研究结果为高温气冷球床堆的安全设计提供了理论支撑，也丰富了颗粒堆积多孔介质热质传递理论体系。.本项目实施以来，本项目发表SCI/EI论文7篇。项目负责人依托本项目前期研究成果申请了国家博士后面上资助项目1项，重庆市博士后特别资助项目1项。