Rib이 설치된 파이프에서의 유동 및 열전달에 관한 수치모사

초록

In the present study, Large Eddy Simulation (LES) of turbulent heat transfer in circular ribbed-pipe flow was performed in order to study the effects of periodically-mounted square ribs on flow and heat transfer enhancement. The ribs are implemented within a cylindrical coordinate system by using an immersed boundary method, and dynamic subgrid-scale models are used to model Reynolds stresses and turbulent heat flux terms. A constant heat flux is imposed on the pipe wall. The Reynolds number (Re) based on the bulk velocity and pipe diameter is 24,000, and Prandtl number (Pr) is 0.71. The blockage ratio is fixed with 0.125, while the pitch ratio based on the rib interval and rib height is varied with 2, 4, 6, 8, 10, and 18. Since the pitch ratio is the key parameter that can change flow topology and turbulence characteristics, we focus on its effect on the flow and temperature fields. Local heat transfer distributions between the ribs were obtained. Friction factor and mean heat transfer enhancement factor were calculated from the mean flow and temperature fields and compared to the previous correlations. Furthermore, simple correlations for the friction factor and the mean heat transfer coefficient were developed for the present blockage ratio. Our LES results shed light on a complete understanding of the heat-transfer mechanisms in turbulent ribbed-pipe flow which has numerous applications in engineering.