三分螺旋折流板换热器壳侧二次流的寻踪

Tracing of secondary flow in shell side of trisection helix heat exchanger

对倾斜角20°有34根管子的周向重叠三分螺旋折流板换热器进行了数值模拟研究,通过在三分螺旋折流板换热器壳侧通道内偏心纵向切面和横切面以及六边形纵向切面上速度矢量流场和压力云图的叠加展示,不仅呈现了壳侧总体螺旋速度的周向分量的轨迹,而且从所呈现的轴向和径向速度分量揭示了二次流和相邻折流板V型缺口处逆向泄漏的踪迹。研究结果表明:流体在螺旋通道内在离心力作用下呈现向外扩张的流动趋势,然后在外围高、中心低的压力分布作用下沿着靠近折流板附近的流速较低的区域向心流动返回轴中心,形成单涡型迪恩二次流;二次流增强了流体的掺混,从而有利于强化传热。

A helix tube-and-shell heat exchanger with 20° tilt angle circumferential overlap trisection helical baffles was numerically analyzed.The flow fields were demonstrated of superimposed velocity vector charts and pressure nephograms on the slices of eccentric longitudinal,transverse,and hexagonal longitudinal in the shell side of the heat exchanger.The results present the trajectory of not only the overall spiral flow azimuth velocity component,but also the axial and radial velocity components that reveals the secondary flow as well as the reverse leakage flow at the V-notches of adjacent baffles.The results show that the shell side fluid expands outward under the centrifugal force in the spiral channel,and then it returns from the periphery to the center under the radial deferential pressure,thus the single vortex type Dean vortex secondary flow is formed in each baffle pitch cycle.The secondary flow enhances the mixing of the fluid at deferent regions,thus contributing to the enhancement of heat transfer.