三角形螺旋流道层流流动及换热特性模拟

摘要

Laminar flow and heat transfer characteristics of triangle helical ducts with right-angled isosceles triangle cross section was investigated numerically with CFD software.The velocity fields and temperature fields of fully developed laminar flow were obtained.The local Nusselt number Nuloc along the heated wall and the effects of the structure parameters of the helical duct on the characteristics of laminar flow and heat tansfer were analyzed respectively.The results indicate that the steady flow structure of secondary flow on the cross section perpendicular to helix is with two vortexes in laminar flow conditions.Affected by the secondary flow,Nuloc along the heated wall is not uniform.There are two peaks on the heated wall near the centers of the two vortexes.As Reynolds number and dimension one curvature increase,two peaks of the Nuloc significantly increase and the poor position near the centre of the heated wall enlarges.The mean Nusselt number increases with the increasing of Reynolds number or the dimension one curvature,while the friction factor increases as well.%应用CFD软件研究了直角三角形螺旋流道内层流流体的流动及换热特性,得到了充分发展条件下流体的速度场及温度场,分析了换热壁面局部努塞尔数Nuloc的分布及流道结构对三角形螺旋流道内流体流动及换热的影响.结果表明:层流状态内,流体在流道横截面上产生的二次涡为稳定的两涡结构；受二次流的影响,换热壁面上各点的努塞尔数并不一致,其峰值出现在靠近二次涡中心位置的换热壁面处.增大雷诺数及量纲一曲率,使得局部努塞尔数峰值明显增大,且会使换热面中心弱传热区增大.平均努塞尔数随着雷诺数或曲率的增大而增大,但相应的阻力系数也会随之增加.