Study On Fluid Flow And Heat Transfer Characteristics In A Channel Formed By Circular Tube Bank Fins Punched With Curved Delta-Winglet Vortex Generators

Tube-fin heat exchanger is widely used in petrochemical industry,aerospace,vehicle,power machinery,cryogenic refrigeration and other fields.The finned structure of tube-finned heat exchanger is the main factor affecting the performance of heat exchanger,Stamping vortex generator is a popular heat transfer enhancement method on the fin surface of heat exchanger.Therefore,it is great significant for fin modification and optimization to improve the overall performance of heat exchanger.The horseshoe vortex induced by the rib side of the tubular fin heat exchanger is of limited strength,In order to improve the heat transfer performance of tube-fin heat exchangers,a triangular curved vortex generator is installed around the tube to improve the secondary flow intensity in the ribbed passage.This paper selects a typical heat transfer unit as computing area,with the method of area division of grid,adopt the method of numerical calculation of dislocation loop rear triangle finned surface vortex generator within the channel performance is analyzed,including dislocation loop in triangle finned surface vortex generator channel secondary flow characteristics and heat transfer characteristics.The effects of the circumferential position parametersβ₁and the radial position parameters D_VG1of the triangular curved vortex generator on the secondary flow characteristics and heat transfer performance were analyzed by using the dimensionless parameter Se to quantify the secondary flow intensity in the channel.The results show that a part of the fluid flows into the triangular vortex generator in front of the tube and vortexes are generated.The other part of the fluid flows to the curved vortex generator behind the tube and under the induced action of the vortex generator behind the tube,the fluid boundary layer is destroyed,the separation of the boundary layer is delayed,the horseshoe vortex behind the tube is reduced and secondary flows are generated,so as to improve the heat transfer performance around the tube.The numerical results show that with the increase of Re,the flow velocity increases and more secondary flows are induced by flushing the triangle surface vortex generator.At the same time,the stamping triangle surface vortex generator can effectively improve the wake area behind the tube.The greater the circumferential position parameters of the triangular vortex generator with a curved surface on the tube,the better the local heat transfer performance around the tube and the better the overall heat transfer performance of the heat exchanger.The larger the radial position parameters of the triangular vortex generator,the better the overall heat transfer performance of the heat exchanger,but the worse the local heat transfer performance around the tube.The circumferential triangular vortex generator greatly improves the local secondary flow and heat transfer performance around the circular tube of the heat exchanger.Based on the results of this study,the correlation between the mean Nussel number（Nu_m）and Se is also fitted to obtain the relationship between the vortex characteristics and heat transfer characteristics of the fin channel.