Present work reports numerical understanding of interfacial dynamics during co-flow of vapor and liquid phases of water inside a typical Boiling Water Reactor (BWR), consisting of a nuclear fuel rod bundle assembly of 7 pins in a circular array. Two representative spacings between rods in a circular array are used to carry out the simulation. In literature, flow boiling in a nuclear reactor is dealt with mechanistic models or averaged equations. Hence, in the present study using the Volume of Fluid (VOF) based multiphase model, a detailed numerical understanding of breaking and making in interfaces during flow boiling in BWR is targeted. Our work will portray near realistic vapor bubble and liquid flow dynamics in rod bundle scenario. Constant wall heat flux for fuel rod and uniform velocity of the liquid at the inlet patch is applied as a boundary condition. The saturation properties of water are taken at 30 bar pressure. Flow boiling stages involving bubble nucleation, growth, merging, local dry-out, rewetting with liquid patches, and complete dry-out are illustrated. The dry-out phenomenon with no liquid presence is numerically observed with phase fraction contours at various axial cut-sections. The quantification of the liquid phase fraction at different axial planes is plotted over time, emphasizing the progressive dry-out mechanism. A comparison of liquid-vapor distribution for inner and outer rods reveals that the inner rod's dry-out occurs sooner than that of the outer rod. The heat transfer coefficient to identify the heat dissipation capacity of each case is also reported.

目前的工作报告了对典型沸水反应堆 (BWR) 内水汽相和液相共流过程中界面动力学的数值理解，该反应堆由圆形阵列中的 7 根核燃料棒束组件组成。圆形阵列中杆之间的两个代表性间距用于进行模拟。在文献中，核反应堆中的流动沸腾是通过机械模型或平均方程来处理的。因此，在目前使用基于流体体积 (VOF) 的多相模型的研究中，目标是对 BWR 流动沸腾过程中界面的破裂和形成进行详细的数值理解。我们的工作将描绘棒束场景中接近真实的蒸汽气泡和液体流动动力学。燃料棒的恒定壁热通量和入口处液体的均匀速度被用作边界条件。水的饱和特性是在 30 巴压力下进行的。流动沸腾阶段包括气泡成核、生长、合并、局部干燥、液体补丁再润湿和完全干燥。没有液体存在的干燥现象在不同轴向截面处的相分数轮廓进行数值观察。随着时间的推移绘制了不同轴平面上液相分数的量化，强调了逐渐变干的机制。内杆和外杆的液-气分布比较表明，内杆的干涸发生得比外杆快。