高温球床壁面区域有效导热系数模型优化  

Optimization of Wall-region Effective Thermal Conductivity Model for High Temperature Pebble Bed

作　　者：步珊珊 陈波 杨光超 陈德奇[1] 马在勇 张卢腾 BU Shanshan;CHEN Bo;YANG Guangchao;CHEN Deqi;MA Zaiyong;ZHANG Luteng(Key Laboratory of Low-grade Energy Utilization Technologies&System,Chongqing University,Chongqing 400044,China;China Nuclear Power Technology Research Institute Co.,Ltd.,Shenzhen 518000,China)

机构地区：[1]重庆大学低品位能源利用技术及系统教育部重点实验室,重庆400044 [2]中广核研究院有限公司,广东深圳518000

出　　处：《原子能科学技术》2022年第8期1626-1632,共7页Atomic Energy Science and Technology

基　　金：国家自然科学基金青年科学基金(51606016);中国博士后科学基金(2016M602650);重庆市博士后特别资助项目(Xm2016024)。

摘　　要：有效导热系数用来表征高温气冷球床堆堆芯综合传热能力,提高球床有效导热系数的预测精度对于高温气冷球床堆的热工设计和安全分析十分重要。为了优化球床壁面区域有效导热系数模型,本文针对无序石墨球床有效导热系数开展数值研究,分析了无序堆积球床主体区域、近壁面区域以及壁面区域有效导热系数的分布特性。结果表明:壁面区域有效导热系数相对于主体区域和近壁面区域显著降低,其平均降幅约为22%。因此引入了修正系数C_(w)对ZBS模型在壁面区域进行优化,对于球床主体区域及近壁面区域修正系数C_(w)=1,对于壁面区域,修正系数C_(w)=0.78。通过与前期无序球床实验数据和南非HTTU实验数据的对比,验证了优化后的ZBS模型能较好地预测球床壁面区域有效导热系数。The pebble bed effective thermal conductivity represents the overall heat transfer capability of the high temperature pebble bed reactor.Improving the precision of the effective thermal conductivity model is very important to the thermal design and safety analysis of the high temperature pebble bed reactor.In order to optimize the effective thermal conductivity model of the pebble bed near the wall region,the three-dimensional and steady heat transfers combining the conduction and radiation in the random pebble beds were numerically solved.The random packing pebble bed was generated based on the discrete element method.The porosity distribution,the coordination number and the contact angle of the random pebble bed were varified by the correlations.The surface-to-surface radiation model was adopted to calculate the radiation heat transfer in the pebble bed.The spatial distribution of local effective thermal conductivity was carefully analyzed.Based on the effective thermal conductivity distributions,the largest gradient occurs at the wall region within a distance about 1 d_(p) away from the wall,becasue the local solid fraction in the wall region varies rapidly.The bulk region can be defined in the range of 4 d_(p)-11 d_(p),in which the local effective thermal conductivities varies mainly due to the temperature.It was found that the wall-region effective thermal conductivity is significantly lower by about 22%than the effective thermal conductivity in the bulk region and the near-wall region.The reason is that the local solid fraction is low,which would weaken the conduction heat transfer as well as the radiation heat transfer.The previous improved ZBS model has a good prediction ability in the bulk region and the near wall region of the pebble bed,but needs to be further improved in the wall region.Therefore,the correction coefficient C_(w)is introduced to the previous improved ZBS model to better predict the effective thermal conductivity in the wall region.The correction coefficient C_(w)=1 for the bulk region

关 键 词：球床堆 有效导热系数 ZBS模型 壁面区域 

分 类 号：TL331[核科学技术—核技术及应用]