Abstract The work presents validation of the TRAC/RELAP Advanced Computational Engine (TRACE) code for natural circulation two-phase flow in a vertical annulus. Natural circulation experiments were recently conducted for a vertical internally heated annulus at the Multiphase Thermo-Fluid Dynamics Laboratory at the University of Illinois. The experimental matrix consists of 107 experiments with system pressure in the range of 145 to 950 kPa and heat flux up to 275 kW/m2. Void fraction, gas velocity, and interfacial area concentration were measured in five axial locations along the test section with six measurements of bulk liquid temperature and pressure. To validate the capability of the TRACE code under natural circulation flow conditions, a complete model of the experimental facility was created and validated using forced convection and single-phase natural circulation data. Sensitivity and uncertainty quantification were performed. The sensitivity to important simulation parameters was studied using Sobol’s variance decomposition and the Morris screening method. The sensitivity of boundary conditions on void fraction measurement was investigated. The sensitivity study has shown significant differences in model sensitivity between different experimental conditions. With heat flux being the most influential parameter for high-pressure cases without flashing and pressure, temperature and heat flux have a combined strong effect in the case of low-pressure experiments when flashing occurs. Additionally, higher uncertainty in void fraction prediction was observed for experimental conditions at low pressure with flashing.

中文翻译：

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使用 TRACE 代码对两相自然循环流进行验证和不确定性量化

摘要 这项工作提出了对垂直环空自然循环两相流的 TRAC/RELAP 高级计算引擎 (TRACE) 代码的验证。最近在伊利诺伊大学的多相热流体动力学实验室对垂直内部加热环进行了自然循环实验。实验矩阵由 107 个实验组成，系统压力范围为 145 至 950 kPa，热通量高达 275 kW/m2。在沿测试部分的五个轴向位置测量空隙率、气体速度和界面面积浓度，并测量了六次整体液体温度和压力。为了验证 TRACE 代码在自然循环流动条件下的能力，使用强制对流和单相自然循环数据创建并验证了实验设施的完整模型。进行了灵敏度和不确定性量化。使用 Sobol 的方差分解和 Morris 筛选方法研究了对重要模拟参数的敏感性。研究了边界条件对空隙率测量的敏感性。敏感性研究表明，不同实验条件之间的模型敏感性存在显着差异。由于热通量是没有闪蒸和压力的高压情况下最有影响的参数，温度和热通量在出现闪蒸的低压实验中具有很强的综合影响。此外，