三分螺旋折流板换热器内二次流分布与强化传热关系分析

通过对倾斜角35°首尾相连的三分螺旋折流板换热器的数值模拟，展示了其壳侧通道内流体在典型切面上的流场和流线分布，以及典型切面上典型直线的流动和换热参数分布，并与性能测试结果进行了对比。结果表明，数值模拟结果与实验结果是吻合的。螺旋折流板形成的近似螺旋通道，使换热器壳侧流体受离心力和向心力共同作用形成了迪恩涡二次流，且在每个螺旋周期内都存在；二次流增强了主流区域流体与靠近壁面流体的掺混，使得壳侧典型切面上中心线和折流板外缘直线的轴向速度较大；除主流中心区域外，壳侧流体在二次流的作用下具有均匀的湍流动能；二次流所在区域内，壳侧同心柱面内典型直线上换热系数相差不大，但由于二次流能使其附近区域传热面上的流体得到不断卷吸掺混，由此强化传热。

Analysis of the relationship between distribution of secondary flow and enhancement of heat transfer in shell-side channel of trisection helical baffled heat exchangers

Using the numerical simulation of end to end tube-and-shell heat exchangers with trisection helical baffles with 35°inclined angle, this research demonstrated the distribution of the flow field and streamline on the typical sections of fluid in the shell side channel, as well as the distribution of flow and heat transfer parameters of typical straight lines on the typical sections. The results showed that the approximate spiral channel composed by helical baffles impelled the Dean vortex secondary flow formed by the combined effect of centrifugal and centripetal force, and the Dean vortex secondary flow existed in each spiral cycle. the secondary flow enhanced the mixing of fluid in mainstream region and fluid near the wall, resulting a larger axial velocity of the centerline and the outer edge straight line on the typical sections. Other than the mainstream center region, the shell side fluid had uniform turbulent kinetic energy in the role of secondary flow. The heat transfer coefficient on the concentric cylindrical surface differed little in the secondary flow region，however, heat transfer can be enhanced due to the fact that the secondary flow was continuously entraining the fluid of the adjacent areas.