直接数值模拟方法研究超临界水传热特性及机理

Supercritical water cooled reactor using supercritical water as a coolant. Supercritical water suffers dramatic changes in physical properties, which leads to abnormal heat transfer behavior different from heat transfer characteristics at subcritical pressures. There are many researches on heat transfer characteristics of supercritical water. However, the heat transfer mechanism of abnormal behavior is not yet clear. Due to lack of suitable turbulence models, computational fluid dynamics cannot reflect the ture convective heat transfer in supercritical water, while it is very difficult to carry out experiments and only get little information. Direct numerical simulation (DNS) does not employ any turbulence model, directly solving the three-dimensional Navier-Stokes equations. Theoretically DNS can get accurate results. This project uses high-precision numerical schemes, combining hybrid MPI and OpenMP programming model to develop high performance parallel direct numerical simulation program DNS_SC , which is suitable for the dramatic changes in the physical properties at supercritical pressure. Using the DNS_SC, the heat transfer characteristics in supercritical water in a vertical tube will be studied. By analyzing the results of direct numerical simulation, heat transfer mechanism will be studied from the perspective of the turbulence. The results of this project will be helpful to supercritical water cooled reactor designs.

超临界水冷堆采用超临界水作为冷却剂， 物性变化剧烈， 会出现异常传热行为,其对流传热特性与亚临界压力流体差异较大。当前对其传热特性的研究较多,但对异常传热行为发生机理尚未清楚,计算流体力学方法缺少合适的湍流模型，不能真实的反映超临界水对流传热特性,而实验开展难度较大且获取信息少。直接数值模拟方法（DNS）未引入任何湍流模型，直接求解三维 Navier-Stokes 方程，理论上可得到精确的结果。本项目采用高精度的数值离散格式,结合 MPI 和 OpenMP 的混合编程模式,研制了适用于超临界压力下物性剧烈变化的高并行性能的直接数值模拟程序 DNS_SC。基于 DNS_SC 研究了超临界水在竖直圆管中的传热特性。通过分析直接数值模拟结果，从湍流的角度对传热机理进行了研究。该项目的研究结果对超临界水冷堆的设计具有重要的参考意义。