Large Eddy Simulation Study on Forced Convection Heat Transfer to Water at Supercritical Pressure in a Trapezoid Annulus
Large Eddy Simulation Study on Forced Convection Heat Transfer to Water at Supercritical Pressure in a Trapezoid Annulus
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DOI：
10.1115/1.4038161
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发表时间：
2018
影响因子：
0.4
通讯作者：
M. M. Amin-M.;Y. Duan;S. He
中科院分区：
文献类型：
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作者：
M. M. Amin-M.;Y. Duan;S. He
现在众所周知，在有限通道中超临界压力下向流体的传热表现出复杂的行为。这是由于压力和温度的变化导致热物理性质的强烈变化。为了提高所设计的超临界水冷堆（SCWR）的可靠性和效率，了解燃料组件中的超临界流体流动非常重要。这里报告的研究重新考虑了由封闭内杆的梯形通道组成的简化几何形状，以模拟燃料组件的三角形布置。采用大涡模拟（LES）和壁适应局部涡粘性（WALE）模型来模拟通道内的强制对流。工作流体采用25 MPa超临界水。基于水力直径和体积速度的雷诺数为 10,540，而来自内杆壁的热通量在 10 kW/m 至 75 kW/m 之间变化。由于流道横截面的不均匀性，观察到存在大的不稳定流动结构。利用瞬时速度、谱分析和相关分析来分析流动结构的特征及其对局部传热的影响。宽间隙中的旋流结构比窄间隙中的旋流结构弱得多。如此大的流动结构的行为受到属性的强烈空间和时间变化的影响。当温度分布遵循Tb<Tpc<Tw时，由于大流动结构而导致的混合参数，包括间隙中的混合系数和有效混合速度，也受到显着影响。 [DOI：10.1115/1.4038161]
It is now well known that heat transfer to fluid at supercritical pressure in a confined channel shows complex behaviors. This is due to the strong variations of the thermal–physical properties resulting from the changes of pressure and temperature. To improve the reliability and efficiency of the supercritical water-cooled reactors (SCWRs) to be designed, the understanding of supercritical fluid flow in the fuel assemblies is very important. The study reported here reconsiders a simplified geometry made of a trapezoid channel enclosing an inner rod to simulate the triangular arrangement of a fuel assembly. Large eddy simulation (LES) with the wall adapting local eddy viscosity (WALE) model is used to simulate the forced convection flow in the channel. Supercritical water at 25 MPa is used as the working fluid. The Reynolds number of flow based on the hydraulic diameter and the bulk velocity is 10,540, while the heat flux from the inner rod wall has been varied from 10 kW/m to 75 kW/m. Large unsteady flow structures are observed to be present due to the nonuniformity of the cross section of the flow channel. The characteristics of the flow structures and their effect on the local heat transfer are analyzed using instantaneous velocities, spectrum analysis, and correlation analysis. The swinging flow structures in the wide gap are much weaker than those in the narrow gap. The behaviors of such large flow structures are influenced by the strong spatial and temporal variations of the properties. When the temperature distribution follows Tb< Tpc< Tw, the mixing parameters due to the large flow structures, including mixing coefficient and effective mixing velocity in the gap, are also significantly influenced. [DOI: 10.1115/1.4038161]