射流入射角度对螺旋管传热性能的影响

Effect of the jet incidence angle on the heat transfer performance of a spiral pipe

为了揭示射流入射角度对螺旋管内流体传热性能的影响规律,通过数值模拟方法对无量纲曲率δ=0.0701、无量纲螺距τ=0.143的螺旋管在不同射流入射角度(α=30°~150°)下的强化传热性能进行研究。结果表明,射流的加入显著强化了螺旋管内流体的换热,在射流速比ε=4和雷诺数Re=19000~26000范围内,随着射流入射角度的增大,螺旋管壁面的平均努赛尔数Nu_(m)、周向局部努赛尔数Nu_(c)(螺旋角θ=4.5π截面)及流动阻力系数f均随之增大;当α=150°时,与单一螺旋管(未加入射流)相比,加入射流后Nu_(m)提升了13.7%以上,Nu_(c)提升了70%。在所研究的Re和ε范围内,强化传热综合性能评价因子(PEC)随着α增大而减小,但PEC均大于1(1.08~1.65);当α=30°时,在研究范围内PEC达到最大,其平均值为1.62,是单一螺旋管的1.62倍,表明此时的螺旋管具有良好的综合强化换热效果。

In order to reveal the influence of the jet incidence angle on the fluid heat transfer performance in a spiral pipe,the heat transfer enhancement performance of a spiral pipe with dimensionless curvatureδ=0.0701 and dimensionless pitchτ=0.143 at different jet incidence angles(α=30°-150°)has been studied by numerical simulation.The results showed that the heat transfer of a fluid in the spiral pipe was enhanced by adding the jet.The average Nusselt number Nu_(m),the section circumferential local Nusselt number Nu_(c)(the axial cross-sectional positionθ=4.5πalong the spiral)and the flow resistance coefficient f increase with the increase of jet incidence angleαin the range of jet velocity ratioε=4 and Reynolds number Re=19000-26000.Whenα=150°,Nu_(m) and Nu_(c)increased by more than 13.7%and 70%,respectively,compared with a single spiral pipe(without a jet).The comprehensive heat transfer performance evaluation factor(PEC)decreased with increasingα,but the PEC was always greater than 1(F_(PEC)=1.08-1.65).Whenα=30°,the PEC reached its maximum value,and its average value was 1.62.This value is 1.62 times the PEC of a single spiral tube,indicating that incorporating a jet in the spiral tube resulted in a good overall enhancement of the heat exchange effect.