摘要
有效扩散系数是描述石墨内部扩散传质的重要参数,传统经验公式中的单一平均孔径假设无法反映石墨内部复杂的孔隙孔径分布规律及其对扩散的影响,现有核级石墨的有效扩散系数计算公式与实验结果相差较大。考虑到受Knudsen扩散影响,并根据核级石墨微观孔隙孔径分布规律及扩散理论将孔径范围分为两类,从而对有效扩散系数计算公式进行了修正。采用压汞仪对IG110核级石墨未氧化及不同温度下等温氧化样品进行了孔径分析,采用本文修正公式计算了有效扩散系数并与实验测量结果进行了比较。同时对失重率、温度和压力对有效扩散系数的影响进行了讨论。结果发现,修正公式计算结果与核级石墨扩散系数的实验结果相符,提高了核级石墨有效扩散系数的计算精度。有效扩散系数随失重率的增加而升高,失重率低于20%时增长明显。有效扩散系数与温度呈0.528次方关系,与压力大致呈-0.33次方关系。
The effective diffusion coefficient is an important parameter describing the diffusive mass transfer inside graphite.The single average pore size assumption can not reflect the complex pore size distribution and mass transfer in graphite,and the existing formulas for calculating effective diffusion coefficient of nuclear graphite differ greatly from experimental results.Considering the influence of Knudsen diffusion,the pore size range of nuclear graphite was divided into two categories according to the micropore size distribution characteristics and diffusion theory,and the formula of effective diffusion coefficient was modified.Then the pore size analyses of unoxidized and isothermal oxidized IG110 nuclear graphite samples at different temperatures were carried out by mercury intrusion meter.The effective diffusion coefficient was calculated using the modified formula and compared with experimental results.The influence of weight loss rate,temperature and pressure on the effective diffusion coefficient was discussed.The calculated results using the modified effective diffusion coefficient formula are consistent with the experimental results.The calculation accuracy is improved.The effective diffusion coefficient increases with the weight loss rate,and increases more significantly when the weight loss rate is lower than 20%.The effective diffusion coefficient is proportional to 0.528 power of temperature,while it is proportional to approximately-0.33 power of pressure.
作者
鲁伟
李晓伟
吴莘馨
孙立斌
LU Wei;LI Xiaowei;WU Xinxin;SUN Libin(Institute of Nuclear and New Energy Technology,Collaborative Innovation Centerfor Advanced Nuclear Energy Technology,Key Laboratory of Advanced Reactor Engineering andSafety of Ministry of Education,Tsinghua University,Beijing 100084,China)
出处
《原子能科学技术》
EI
CAS
CSCD
北大核心
2019年第6期1078-1084,共7页
Atomic Energy Science and Technology
基金
国家自然科学基金资助项目(51576103)
国家科技重大专项资助项目(ZX06901)
关键词
核级石墨
有效扩散系数
微孔
孔径分布
nuclear graphite
effective diffusion coefficient
micropore
pore size distribution
