三角形螺旋夹套内流体的湍流流动及换热模拟

对三角形螺旋夹套内流体的湍流流动及换热性能进行了模拟，得到了充分发展条件下恒定热流加热时釜内湍流流体的速度场，分析了雷诺数(Re)和无量纲曲率(k) 对流体阻力和换热性能的影响，并由模拟数据拟合出平均阻力系数及平均努赛尔数的关联式. 结果表明，湍流流动中，夹套内流体的二次流动为稳定的二涡结构，随雷诺数增大，二次流强度和湍动能均增强. 由于离心力的作用，外壁面的阻力系数远大于内壁面. 换热面上局部努塞尔数的峰值出现在靠近二次涡中心位置的换热壁面处，换热面中心处的局部努塞尔数约为峰值的85%. 随Re和k增大，峰值处的局部努塞尔数值增大最明显，流体的平均努塞尔数及阻力系数均增大. 在所模拟的范围内，三角形螺旋夹套的效率因子E>3.7，且随Re和k增大，E逐渐增大.

Simulation on Turbulent Flow and Heat Transfer in the Triangular Helical Jacket

Turbulent flow and heat transfer in the triangular helical jacket were simulated. The velocity field of fully developed turbulent flow with constant heat flux on heated wall was obtained. The effects of dimensionless curvature ratio (k) and Reynolds number (Re) on the characteristics of flow resistance and heat transfer were analyzed. The mean flow friction factor and mean Nusselt number were correlated based on the simulated data. The results indicate that the structure of secondary flow has two steady vortexes. Both the secondary flow intensity and turbulent kinetic energy are enhanced with increasing of Re. Due to the centrifugal force, the mean friction factor on the outer wall is far greater than that on the inner wall. The peaks of local Nusselt number (Nulocal) are located at the inner heated wall near the centers of secondary vortices. With the increase of Re and k, two peaks of Nulocal increase significantly, the mean Nusselt number of the inner heated wall and the coefficient of resistance increase as well. In the simulated range, the efficiency factor increases with the increase of Re and k, ranging from 3.7 to 4.2.