蒸汽发生器热工特性非轴对称分布数值模拟

Numerical simulation on the non-axisymmetric distribution of thermal characteristics in a steam generator

为了研究高温气冷堆蒸汽发生器热工水力参数非轴对称分布特性,以阿贡国家实验室蒸汽发生器为原型,结合其结构特点及工作过程建立单根螺旋管物理模型,模拟蒸汽发生器螺旋管内二回路流体的流动、单相对流换热及相变换热过程。计算结果表明:高温气冷堆蒸汽发生器的壁温、流速等关键参数均呈非轴对称分布,且单相区和相变区关键参数沿管截面周向分布趋势完全相反。单相区由于离心力作用螺旋管外侧水的流速大,换热剧烈,壁温低;进入相变区后由于汽液两相受浮升力与离心力的双重作用蒸汽聚集在螺旋管内侧,气泡扰动强化换热,壁温低。

Taking the high-temperature gas-cooled reactor（ HTGR） steam generator（ SG） at Argonne National Laboratory（ ANL） as the prototype,in combination with the structural characteristics and working process of the SG,a physical model of single helically coiled tube was made. The processes of flow,single phase convective heat transfer and boiling phase change heat transfer of secondary loop fluid in a helically coiled tube were simulated to investigate the non-axisymmetric distribution of thermal-hydraulic characteristics in a HTGR steam generator. The results show that the distribution of key parameters around the circumference of a HTGR steam generator,such as wall temperature and velocity,is nonaxisymmetric; besides,in the single-phase area,the circumferential distribution of key parameters along the cross section of tube is completely opposite to that in the two-phase area. The velocity is greater,heat transfer is more intense and wall temperature is lower along the outside of helically coiled tubes in the single-phase area due to centrifugal force.Steam gathers along the inside of the helically coiled tube due to the dual role of buoyancy lift and centrifugal force in the two vapor-liquid phases after having entered the two-phase flow area. Heat transfer is enhanced because of bubble disturbance,and therefore wall temperature is lower at this location.