Effect of rotation on forced turbulent flow and heat transfer in a ribbed U-duct

The paper presents a method and simulation results for turbulent airflow and heat transfer in a U-shaped square duct with straight sections and with two ribbed opposite sides. For a flow with Reynolds number of 6·10⁴ and Prandtl number of 2.5, the numerical solution method was validated by comparing the simulated and experimental data on local heat and mass transfer in geometrically identical U-ducts; the ribs inclined to the duct axis by 45 and 60 deg. For one of these ducts with the rib inclination angle of 45 deg (at the same Reynolds number and Prandtl number of 0.71), the flow patterns and heat transfer were calculated for a stationary state and for a mode with rotation (with the rotation parameter values of 0.1 and 0.25). The rotation axis is perpendicular to the duct axis and parallel to the duct bending plane. The numerical data for the U-shaped duct are compared with the data for a fully developed (periodic) flow and heat transfer for a straight duct with ribbing. It is shown that for a U-duct, the effect of rotation has a positive influence on heat transfer enhancement.