Abstract: The CFD software was employed to study the fluid flow characteristics and heat transfer enhancement in the helical coiled channel under the action of jet. The cross-section of the helical channel was circular and the dimensionless curvature and pitch of the helical channel were 0.061 and 0.121, respectively. The simulated results were in good agreement with the existing experimental data. The structure of composite vortices and its evolution process in the channel have been discussed. The effect of jet action on heat transfer enhancement was investigated in the range of incident angle ?=π/6–π/3 and jet velocity ratio ?j=3–6. The results show that in the initial stage of jet in the helical channel, the secondary vortices induced by centrifugal force were completely suppressed by impact of the jet. And another pair of vortices named as jet induced vortices emerged under the impact and entrainment of the jet, wherein the rotating direction was opposite to that of the vortices induced by the centrifugal force. With the flow development, the structure of the jet induced vortices changed from two vortices into one vortex, and then, gradually dissipated and disappeared. The heat transfer of fluid near the inner wall of helical channel was significantly enhanced by the jet action. As ? decreased or ?j value increased, the heat transfer enhancement effect was increased. In the studied range of ?j≥4, without considering the jet flow rate increase, the comprehensive heat transfer enhancement factor JF1 was between 1.26 and 1.67, while when the jet flow rate increase was considered, JF2 was in the range of 1.008~1.19.

Key words: helical channel, impinging jet, flow characteristics, enhanced heat transfer, secondary flow

摘要： 采用CFD软件模拟了射流作用下圆形截面螺旋通道内流体的流动及强化传热特性，模拟结果与实验结果吻合较好。研究了无量纲曲率?=0.061、无量纲螺距?=0.121的螺旋通道内复合涡旋结构及其演变过程，考察了射流入射角度?=π/6~π/3、射流速比?j=3~6时射流对螺旋通道换热的强化效果。结果表明，射流的初始阶段，射流的冲击作用抑制了单一螺旋通道内的离心二次涡旋，生成一对与其旋转方向相反的射流诱导涡旋，随流动发展，射流诱导涡旋先由两涡演变为单涡结构而后逐渐耗散消失。射流作用显著强化了螺旋通道内侧壁面附近流体的换热，随着?减小或?j增大，强化传热效果增强。?j≥4时，不考虑射流流量增加时综合强化传热因子JF1=1.26~1.67，考虑射流流量增加时JF2=1.008~1.19。

关键词: 螺旋通道, 冲击射流, 流动特性, 强化传热, 二次流