超临界水冷堆类三角形子通道流动传热特性研究

基于类三角形子通道超临界水的传热试验，建立了超临界水冷堆三角形子通道物理模型。采用雷诺应力湍流模型SSG，在压力为23～28 MPa、质量流速为700～1300 kg/(m²?s)、热流密度为200～1000 kW/m²参数范围内，对棒径8 mm、栅距比为1.4的子通道内超临界水流动与传热特性进行了数值研究。分析了系统参数对流动和传热特性的影响，对比了不同焓区的二次流特性。结果表明：采用SSG模型对超临界水冷堆三角形子通道内流动传热的CFD模拟结果与试验数据较吻合。质量流速越高，传热能力越强；子通道换热系数峰值随压力的提高而减小；热负荷越高，内壁温度越高；在大比热容区换热系数峰值随热流密度的增大而明显减小，传热存在恶化趋势。超临界区子通道内在与主流垂直方向形成了明显的二次流，存在6个对称的漩涡，二次流速最大值出现在子通道窄缝区间隙。通道内不同焓区二次流结构相似，但二次流强度随焓的提高而增大。

Investigation on Flow and Heat Transfer Characteristics of Supercritical Water in Sub-channel with Triangular Distribution of SCWR

The physical model of the sub-channel within a triangular rod bundle,of which the rod diameter is 8 mm and the pitch-to-diameter ratio is 1.4,was built to numerically investigate the flow and heat transfer characteristics of supercritical water in the sub-channels of supercritical water-cooled reactor.The numerical investigation was performed within the range of pressure from 23 to 28 MPa,mass fluxes from 700 to 1 300 kg/(m2 ·s),and heat fluxes from 200 to 1 000 kW/m2 .By using the Reynolds stress turbulence model SSG,the effects of mass flux,pressure and heat flux on the flow and heat transfer characteristics were analyzed in detail,as well as the secondary flow characteristics in different enthalpy regions.The results show that the numerical results agree well with experimental results.The higher the mass flux is,the better the heat transfer performs.In the pseudo-critical enthalpy region,the peak of heat transfer coefficient decreases greatly with the increase of pressure and heat flux.The high heat flux induces high inner wall temperature and might cause the heat transfer deterioration. The obvious secondary flow is found in the direction perpendicular to the main flow,and six symmetrical vortices are formed in the cross section of sub-channel.The velocity of the secondary flow reaches a peak near the narrow gap.Although the structures of the secondary flow are similar in different enthalpy regions,the secondary flow velocity increases with bulk enthalpy.