Study On The Influence Of The Shape And Installation Position Of The Jet Vortex Generator On The Heat Transfer Performance Of The Enhanced Helical Channel

As an active heat transfer enhancement technology,jet has been widely used in industrial processes such as chemical industry,energy power and electronics due to its high heat transfer efficiency and easy control.The jet vortex generator is installed in the helical channel to generate the jet longitudinal vortex,which can improve the characteristics of the secondary flow field and realize the heat transfer enhancement of the fluid in a certain area of the helical channel.In order to further improve the heat transfer enhancement effect of the jet vortex generator on the helical channel,the inlet section shape and installation position of the jet vortex generator are improved,and the experiments and numerical simulation methods are used to study.Based on the same mass flow Q_m,the effects of jet angleαand jet mass flow ratioε_jm on flow resistance and convective heat transfer performance were investigated.Considering the increase in power consumption of the jet pump,a new index for evaluating the active heat transfer enhancement method,the thermal power coefficient ratio,is proposed for the first time,and the comprehensive heat transfer performance of the jet enhanced helical channel is analyzed.An experimental device for enhancing the heat transfer of the helical channel by jets was established,and the ratiosΔof the major and minor axes of the elliptical jet inlet section were 0.39,0.51,1,1.96,and 2.56,respectively,to the fluid in the circular section of the helical channel by experimental and numerical simulation methods.The numerical simulation results are in good agreement with the experimental results.The results show that the smaller theΔvalue,the stronger the composite secondary vortex strength under the influence of the jet,the more significant the enhancement effect of convective heat transfer,and the better the comprehensive enhancement effect of heat transfer.WhenΔ≤1,the jet significantly enhances the heat transfer of the fluid near the inner sidewall of the channel,whenΔ>1,the jet effect only enhances the heat transfer effect of the fluid near the outer sidewall due to the weakened impact on the inner sidewall.Within the research range,compared with a single helical channel at the same mass flow rate,whenΔ=0.39,the average local convective heat transfer coefficient(h_local)_m increased by up to 167%.In the given research range,the smaller theΔ,the better the comprehensive enhanced heat transfer effect,and the thermal power coefficient ratio hpc is between 1.28 and 1.38.The numerical simulation method was used to compare and study the heat transfer enhancement effect of the jet on the helical channel when the jet vortex generators were installed inside and outside the helical channel respectively.The jet mass flow ratioε_jm is between 0.1 and 1.5,and the jet angleαis between 30°and 80°.The research results show that when a jet is added to the outer side wall,a pair of jet-induced vortices with opposite directions to the centrifugal vortex will be generated in the channel,and the two pairs of vortices will inhibit each other.the strength and range of the secondary vortex.With the increase of the mass flow ratioε_jm or the decrease of the jet angleαthe convective heat transfer capacity of the fluid in the helical channel under the action of the jet on the inner and outer sidewalls increases,but the flow resistance also increases.However,the larger the jet mass flow ratioε_jm,the larger the external power consumption consumed.Under the same conditions,the overall heat transfer enhancement effect is better than that of the outer wall jet due to the smaller total power consumption under the inner side wall jet.With the increase ofαandε_jm,hpc shows a trend of first increasing and then decreasing.Within the research range,when the jet parameters areε_jm=0.5,α=60°,the comprehensive heat transfer enhancement effect is the best,at this time,the hpc values of the inner and outer sidewall jets are 1.39 and 1.32,respectively.