Turbulent heat transfer enhancement in an axially rotating pipe fitted with kenics segment mixer

Abstract

This study reports heat transfer in an axially rotating pipe fitted with Kenics segment mixer. Numerical simulations were processed with the commercial finite volume Computational Fluid Dynamics (CFD) code, ANSYS Fluent 19.2. The rotating domain was modeled with the single rotating reference frame scheme. Natural convection was considered in the numerical procedure. Computations were carried out for axial Reynolds numbers between 5000 and 25,000 ​at different rotation rates. Rotation rate (N) is the ratio of the rotational Reynolds number to the axial Reynolds number. Predictions revealed that the Kenics segment mixer significantly improved the heat transfer of the rotating pipe. This remarkable augmentation in heat transfer was attributed to additional swirl flow created by the inserted tape. By using the Kenics segment mixer with twist ratio of 1.75, the Nusselt number of the plain rotating pipe was augmented by 92–66% at N ​= ​1, 74-55% at N ​= ​3, and 60-44% at N ​= ​5. Reduction in Nusselt number augmentation as the rotating speed of the pipe increased indicated that swirl flows induced by the Kenics segment mixer was more dominant at lower rotation rates.