垂直内螺纹管内超临界水的二次流特性

Secondary flow of supercritical water in internal ribbed tube under high temperature conditions

运用计算流体力学方法,采用SSG雷诺应力模型对高温条件下垂直内螺纹管中超临界水的二次流特性进行了研究。研究发现:内螺纹的导流作用在垂直于主流的方向产生了很强的二次流场,主流焓的变化对二次流场的基本结构影响很小。内螺纹管周向和径向上的传热系数分布不均,超临界水在螺纹顶部区域的传热效果远好于螺纹底部。在螺纹顶部表面形成的单个旋涡产生一个压力相对较低的区域,传热增强。在大比热区,由于流体热物性急剧变化,传热的不均性更加显著。螺纹底部壁面是内螺纹管周向传热的薄弱位置,其内部结构的优化应重点集中在该区域。

The secondary flow of supercritical water in a vertical internal ribbed tube was studied under high temperature conditionsusing SSG Reynoldsstress model. It was found that a strong secondary flow is formed due to the guidance of internal rib and the variation of bulk enthalpy has little influence on the main structure of the secondary flow. The local flow and heat transfer in the circumferential and radial directions of the tube is not uniform. The average heat transfer near the top surface of the rib is much better than that near the substrate surface. The individual vortex formed on the top surface of the rib creates a relatively low pressure region and augments the heat transfer. The heat transfer heterogeneity is more pronounced in the great specific heat region （GSHR） due to the drastically changed physical properties. Since the substrate is the weak point of the heat transfer, the optimization of the tube internal structure is suggested to focus on this region.