冲孔对三角小翼平翅片流动换热特性的影响

Effects of punched holes on flow and heat transfer characteristics of the plain fin with delta winglets

利用三维数值模拟的方法,研究了在平翅片上冲压三角小翼时留有的三角孔洞及其位置对翅片流动换热特性的影响.结果表明:迎流面冲孔处形成向下的流动,该流动对主流纵向涡影响很小;背流面冲孔处形成向上流动,该流动冲刷主流纵向涡,使每个三角小翼下游形成旋转方向相反的两个涡旋.迎流面冲孔对三角小翼翅片的换热性能影响很小,背流面冲孔使三角小翼翅片的换热性能下降,努谢尔数降低了1.0%~5.0%,迎流面和背流面冲孔均使三角小翼翅片的流动阻力减小.三角小翼的布置提高了翅片的综合换热性能,采用冲压方式加工三角小翼时,冲孔在小翼迎流面较优.

3D numerical simulations are performed to investigate the flow and heat transfer characteristics of the plain fin with the delta winglets punched out from the fin.The effects of the punched holes and their position on the fluid flow and heat transfer are numerically studied.Results show that a downwash flow is formed in the hole punched at the upwind position of the delta winglet,which has little influence on the longitudinal vortices in the main flow.An upwash flow is formed in the hole punched at the downwind position of the delta winglet,the upwash flow scours the main flow,and then a counter-rotating pair of vortices is generated behind each delta winglet.The upwind punched holes have little effect on the heat transfer of the plain fin with delta winglets,while the heat transfer of the plain fin with delta winglets is deteriorated by the downwind punched holes,the Nusselt number is decreased by 1.0% ~ 5.0%.The upwind and downwind punched holes both lower the flow resistance of the plain fin with delta winglets.The application of the delta winglets improves the heat transfer performance of the plain fin,and the upwind punched holes are better for the punched winglets on the plain fin.