不同射流速比对螺旋管内流体传热性能的影响

Effect of Different Jet Velocity Ratio on Heat Transfer Performance of Fuid in Spiral Pipe

为了探究射流对螺旋管内流体传热性能的影响规律,采用数值模拟方法研究了无量纲曲率δ=0.0701、无量纲螺距τ=0.143的螺旋管在不同射流速比(ε=1~6)条件下强化传热的效果。研究结果表明:当射流速比ε>2时,射流流体可穿透螺旋管主流流体冲击到螺旋管外侧壁面,大幅度提高螺旋管外侧壁面的换热能力。在雷诺数Re=19000~26000的条件下,随着ε的增大,螺旋管壁面平均努赛尔数Nu_(m)增大,流动阻力f减小,与单一螺旋管(未加入射流)相比,ε>2时螺旋管的Nu_(m)增大幅度较为显著,当ε=6时Nu_(m)最大,与单一螺旋管相比Nu_(m)提升了25%;螺旋管截面周向努赛尔数Nuc和射流管安装位置处的轴向局部努赛尔数Nua均随着ε增大而增大,且射流在螺旋管内起强化传热作用的距离也随ε增大而增大,当ε>2时,强化传热的螺旋角度距离可达到60°以上;随着ε增大,综合传热性能评价因子PEC增大,且PEC均大于1(PEC=1.03~1.42),PEC的平均值是单一螺旋管的1.23倍,在所研究的范围内,当ε>2时PEC的增大幅度较为明显,当ε=6时PEC最大,具有良好的综合强化换热效果。

In order to investigate the effect of jet on the heat transfer performance of a spiral pipe,the heat transfer enhancement effect of a spiral pipe with dimensionless curvatureδ=0.0701 and dimensionless pitchτ=0.143 under different jet speed ratios(ε=1~6)was studied by numerical simulation.The results showed that when the jet velocity ratio was greater than 2,the jet fluid could penetrate the main flow and impact the outer wall of the spiral tube,and improve the heat transfer capacity of the outer wall of the spiral pipe.When Reynolds number Re=19000~26000,with the increase ofε,the average Nuer number Nu_(m)of spiral pipe wall increased and the flow resistance f decreased.Compared with the single spiral pipe(without efflux),whenε>2,Nu_(m)increased significantly.Whenε=6,Nu_(m)increased by 25%compared with the single spiral pipe.The circumferential Nusselt number Nuc and the axial local Nusselt number Nua of the helical pipe cross section increased with the increase ofε,and the distance of heat transfer enhancement by the jet in the helical pipe also increased with the increase ofε.Whenε>2,the helical angle distance of heat transfer enhancement could reach more than 60°.With the increase ofε,the comprehensive heat transfer performance evaluation factor PEC increased,and PEC was greater than 1(PEC=1.03~1.42),the average value of PEC was 1.23 times that of single spiral pipe.In the range of study,the increase of PEC was more obvious whenε>2,and the maximum PEC was whenε=6,which had good comprehensive enhanced heat transfer effect.