Study of Coherent Structures of Turbulence in Flows with Wall Heat Flux in Supercritical Fluids

所提出的用于具有改进的热效率和减小的尺寸的发电厂的先进设计包括具有超临界工作流体的配置，例如利用超临界水作为用于核芯的冷却剂的核反应堆和在闭合循环配置中利用超临界工作流体的布雷顿循环。这种先进电厂的成功取决于我们准确预测电厂某些部件中传热速率的能力。有实验证据表明，对于某些组合的热通量和质量通量在超临界流体流动的加热通道，测得的强制对流传热率显着偏离现有的相关性，是基于单相亚临界流体的预测。拟议的研究旨在提高我们的基本理解的作用，流动湍流在这些观察到的变化的传热速率。该研究利用直接数值模拟-在没有任何湍流运动假设的情况下求解流体动力学控制方程-在计算机集群上进行，并辅以超临界制冷剂（R134 a）和超临界水的实验测量。该研究包括已知影响剪切层湍流的参数的系统变化，例如流向压力梯度和流动雷诺数。

Proposed advanced designs for power-generation plants with improved thermal efficiency and reduced size include configurations with supercritical working fluids, such as nuclear reactors utilizing supercritical water as the coolant for the nuclear core and Brayton cycles utilizing supercritical working fluids in a closed-cycle configuration. The success of such advanced power plants is dependent on our ability to accurately predict the rate of heat transfer in certain components of the power plant. There is experimental evidence that for certain combinations of heat and mass fluxes in supercritical fluid flows in heated channels, the measured rate of forced-convection heat transfer notably deviates from those predicted by existing correlations that are based on single-phase subcritical fluids. The proposed study aims to improve our fundamental understanding of the role of flow turbulence in these observed variations in the heat-transfer rate. The study makes use of direct numerical simulations - solution of the governing equations of fluid dynamics without any assumptions on turbulence motion - on clusters of computers supplemented by experimental measurements in a supercritical refrigerant (R134a) and supercritical water. The study includes systematic variations in parameters known to affect shear-layer turbulence, such as streamwise pressure gradient and flow Reynolds number.