组合涡发生器强化螺旋通道换热的数值研究

Numerical study on heat transfer enhancement in helical ducts with combinational vortex generators

旨在研究B形翼和柱形涡发生器组合后强化矩形螺旋通道内流体换热的特性。采用CFD模拟的方法分析了量纲一曲率κ、B形翼攻角α对螺旋通道内流体流动和换热的影响,并利用综合强化因子G表征组合涡发生器的综合强化效果。结果表明:B形翼改变了柱后二次流的结构,在柱后截面的中心区域形成一对方向相反的附加涡,减小了柱后尾迹区的尺寸,增大了柱后流体的温度梯度,强化了传热;在所研究范围内,α增大,组合涡发生器强化传热效果先增大后减小,在攻角α=40°—45°时强化传热效果最优;α一定,κ值越小,组合涡发生器的强化效果越好,相对于只有柱时,其Nu提高了56.45%—69.08%,G提高了24%—37%。

Heat transfer characteristics in the rectangular helical ducts with B winglet-type and cylinder-type vortex generators were investigated.The effects of the dimension one curvature(κ)and the attack angle of B-type winglet(α)on turbulent flow and heat transfer in rectangular helical channels were researched numerically used CFD method,and the comprehensive strengthening effects on account of the comprehensive factor(G)were analyzed.The results show that B-type winglet changes the sturcture of secondary flow,and a couple of additional vortices in opposite rotation directions appear at the back of cylinder.The region of the wake is decreased,the temperature gradient of the fluid in the wake region is increased and heat transfer enhancement occurs.In the studied range,the enhanced heat transfer performance of combinational vortex generators is increased first and then decreased asαincreases.Whenα=40°-45°,the effect of enhanced heat transfer is optimum.For constantα,the smaller the value ofκ,the better feature of heat transfer with B-type winglet.Nu and G of the helical duct with combinational vortex generators increases 56.45%-69.08%and 24%-37%respectively compared to the case with only cylinder-type vortex generators.