Numerical investigations on effects of seven drag reduction components in elbow and T-junction close-coupled pipes

摘要

Close-coupled pipes can be applied to a number of HVAC systems. This paper discusses the local drag reduction achieved by components placed in elbow and T-junction close-coupled pipes. The components are necessary to reduce or even eliminate vortices produced by turning flow patterns. It includes a numerical study of drag reduction effects of seven components with different shapes. The shear stress transport (SST) k-ω turbulence model is applied. The local pressure loss coefficients and the drag reduction rate are introduced to compare drag reduction effects. The results show that the drag reduction components studied in this paper all have varying degrees of an effect for most of the cases. Also, the drag reduction effect of components was influenced by the specific flow cases. Therefore, the selection of a suitable shape for the drag reduction component should consider the flow pattern. Practical application: This paper has studied the local drag reduction achieved by components placed in elbow and T-junction close-coupled pipes, which can be used in the building industry. In order to find the suitable component shapes, we designed seven kinds of drag reduction components. The designs came from drag reduction technologies used in different applications such as commercial, high performance automobiles and aerofoil designs.