【作者】 张锐；

【导师】 马在勇；

【作者基本信息】 重庆大学 ， 工程（动力工程）（专业学位）， 2022， 硕士

【摘要】 棒束通道为核反应堆堆芯燃料组件的常见结构,其开式的通道单元(子通道)间存在横向的质量、动量及能量交换,棒束通道间横流及湍流交混效应是这些交换的关键机制,而反应堆棒束通道中的定位格架则对这些交换起到显著的强化作用。通常认为,不管是否存在格架,横流及湍流交混效应均为构建棒束通道子通道分析方法的基础要素,现有相关研究指出对于横流及湍流交混效应的研究有助于提高反应堆堆芯的临界热流密度(CHF)。鉴于此,本文基于实验和分析对棒束子通道间的横流及湍流交混特性开展了研究,相关研究结果对于提升棒束通道传热流动特性的理解,提高核反应堆系统的安全性和经济性都具有重要意义。借助一种可以测量微小压差的倒U型压力计完成了单相及两相工况下格架棒束子通道间的横流效应实验。通过分析实验结果,得到了单相及两相工况下棒束通道间横流效应的作用规律。单相工况下:横流阻力系数随着雷诺数的增大而减小,随横流流速与主流流速之比增大而减小;两相工况下:横流阻力系数随横流流速与主流流速之比增大而减小,界面摩擦因子随气相横流雷诺数的增大而减小。通过最小二乘法分别拟合得到了横流阻力系数与雷诺数、横流阻力系数与横流流速及主流流速之比、界面摩擦因子与气相横流雷诺数之间的实验关联式,相关系数均大于0.939,所得的关联式与实验结果符合良好。使用质量平衡法完成了单相工况下带格架棒束子通道间湍流交混效应的实验研究,示踪剂为酸性橙溶液,使用L6S紫外可见光分光光度计对酸性橙溶液的浓度进行测量。通过分析示踪剂浓度沿程变化情况,得到了湍流交混系数沿实验段轴向变化规律以及有效湍流交混系数。分析实验数据发现,随雷诺数的增大,无量纲湍流交混率增大但湍流交混系数基本不变,由此得出了湍流交混系数不随热工参数变化的结论;拟合得到了带格架以及不带格架工况下,无量纲湍流交混率随雷诺数变化的实验关联式;对比带格架棒束子通道实验数据,发现格架有助于增大棒束通道的湍流交混系数。开展了CFD数值模拟对带格架棒束子通道间的单相湍流交混效应进行了研究。使用实验结果对数值模拟结果进行了验证,带格架及不带格架工况下数值模拟结果与实验值均吻合良好。借助数值模拟分析了格架下游通道内温度的变化情况,得到了搅混翼格架对于横流及湍流交混效应的综合作用结果。更多还原

【Abstract】 The rod bundle channel is a common structure of the nuclear reactor core fuel assembly.There are lateral mass,momentum and energy exchanges between the open channel units(sub-channels),and the cross-flow and turbulent mixing effect between the rod bundle sub channels are the key mechanisms of these exchanges while the spacer grids in the reactor rod bundle sub channels significantly enhance these exchanges.It is generally believed that,regardless of whether there is a spacer grid or not,the cross-flow and turbulent mixing effects are the basic elements for the construction of the sub-channel analysis method of the rod bundle channel,and the relevant studies have pointed out that the study of the cross-flow and turbulence mixing effects can help improve the critical heat flow(CHF)of the reactor core.In view of this,the cross-flow and turbulent mixing characteristics between the rod bundle sub-channels were studied by experiments and analysis.The research results were useful for improving the understanding of the heat transfer flow characteristics of the rod bundle channel and improving the safety and economy of the nuclear reactor system.With the help of an inverted U-shaped manometer capable of measuring tiny pressure differences,the cross-flow experiments between the sub-channels of the rod bundle under single-phase and two-phase conditions were completed.By analyzing the experimental results,the law of cross-flow effect between rod bundle channels under single-phase and two-phase conditions was obtained.Under the single-phase condition:the cross-flow resistance coefficient decreased with the increase of Reynolds number,and the increase of the ratio of the cross-flow velocity to the main flow velocity;under the two-phase condition: the cross-flow resistance coefficient decreased with the ratio of the cross-flow velocity to the main flow velocity.The interface friction factor decreased with the increase of the gas-phase cross-flow Reynolds number.The experimental correlations between the cross-flow resistance coefficient and the Reynolds number,the ratio of the cross-flow resistance coefficient to the cross-flow velocity and the main flow velocity,and the interface friction factor and the gas-phase cross-flow Reynolds number were obtained by the least squares method,and the correlation coefficients were all greater than 0.939.The correlation formula was in good agreement with the experimental results.The experimental study of the turbulent mixing effect between sub-channels of beams with spacer grid rods was completed by mass balance method.The tracer was acid orange solution,and the concentration of acid orange solution was measured by L6 S UV-Vis spectrophotometer.By analyzing the variation of the tracer concentration along the process,the variation law of the turbulent mixing coefficient along the axis of the experimental section and the effective turbulent mixing coefficient were obtained.Analyzing the experimental data,it was found that with the increase of Reynolds number,the dimensionless turbulent mixing rate increased but the turbulent mixing coefficient was basically unchanged,so it was concluded that the turbulent mixing coefficient did not change with the thermal parameters;the experimental correlations of the variation of the turbulent mixing rate with the Reynolds number were obtained;Comparing the experimental data of the sub-channels of rod bundles with spacer grid,it was found that the spacer grid help to enhance the turbulent mixing coefficient of the rod bundle channels.The single-phase turbulent mixing effect between sub-channels of spacer grid rod bundles was studied by means of CFD numerical simulation.The numerical simulation results were verified by the experimental values,and the numerical simulation results with or without spacer grid were in good agreement with the experimental data.The change of temperature in the downstream channel of the spacer grid was analyzed and the cross-flow and turbulent mixing effect under the working condition with spacer grid has been obtained by means of numerical simulation.更多还原