Numerical Study Of Heat Transfer Characteristics In Convergent Ribbed Square Channels

Ribbed channel cooling is widely used in turbine blade internal passage cooling and other fields.Such as solar air heaters,heat exchangers,etc.For advanced gas turbine blades,internal cooling mainly involves a serpentine flow path in the middle of the blade.Different types of fins are cast on the two opposite walls of the cooling channel to achieve the purpose of enhancing heat transfer.Exploring the mechanism of heat transfer enhancement under different structures and finding the optimal heat dissipation structure has always been the focus of research.In this paper,the heat transfer characteristics of convergent ribbed square channels are studied by numerical calculation.The focus is on the analysis of convergent channels with straight ribs,inclined ribs,V-down ribs and V-up ribs.By changing the structural parameters such as relative rib spacing,relative rib height,rib inclination angle,V-ribbed angle,and channel taper angle,the mechanism of heat transfer enhancement was studied.In addition,the effects of different types of ribs on the average longitudinal vorticity intensity Se_s and longitudinal vortex intensity Se of the cross section were studied in the background of secondary flow intensity.The result is as follows:（1）From the comprehensive analysis of heat transfer strength and longitudinal vortex strength,V-up ribs are superior to other types of ribs for the integrated heat transfer of convergent ribbed square channels.（2）For the convergent square channel with straight ribs,as the relative rib pitch and relative rib height increase,the heat transfer and the friction coefficient increase gradually.（3）For the convergent square channels with diagonal ribs,the diagonal ribs suppress the attenuation of longitudinal vortices and enhance heat transfer.When the relative rib pitch is12.5,the longitudinal vortex intensity is the largest.Compared with other inclination angles,the longitudinal vortex intensity Se and Nu/Nu₀ generated at 45°are the largest and the comprehensive heat transfer characteristics are the best when inclination angle is 30°at the pump operating rate.（4）For the convergent square channels with V-down ribs and V-up ribs,the values of Se_s,Se,Nu/Nu₀,and f/f₀ are the largest when the angle is 45°.When the relative rib pitch increases,the influence range of longitudinal vortices expands but the decay rate is fast.（5）The greater the convergent angle,the faster the resistance increases due to the fluid being accelerated along the flow direction.However,the heat transfer has not improved much,so the larger the convergent angle,the worse the overall heat transfer performance.（6）In the ribbed convergent square channel,there is mutual interference between the longitudinal vortices generated by the ribs.In addition,the average longitudinal vortex intensity Se of the cross section increases with the increase of Re_m.（7）The average Nusselt number Nu increases as the longitudinal vorticity Se.In addition to straight ribs,there is a linear relationship between the longitudinal vortex strength Se and Nu in the convergent channels with diagonal ribs,V-down ribs,and V-up ribs and the maximum errors are 20%,15%and 5%,respectively.