Obed Y.W. Abotsi^1,, J.P. Kizito¹

This paper addresses heat transfer enhancement in an axially rotating pipe under constant wall heat flux condition. Numerical simulations were processed using the Reynolds Average Navier-Stoke (RANS) solver of ANSYS Fluent 19.2. The realizable k-ε turbulence model was used to provide closure to the RANS equations. Buoyancy effects (β∆T) and gravity (g) were considered in the numerical analysis. Parametric runs were made for axial Reynolds numbers between 10000 and 30000 (10000 ≤ Re_a ≤ 30000) at various rotation rates (0 ≤ N ≤ 3) using water as the working fluid. CFD results showed that increasing the rotation rate (N) augmented the Nusselt number. Nusselt number augmentation was associated to increase in the strength of secondary flow. The influence of twisted tape insert on the thermal performance of the rotating pipe was also investigated. Twisted tape produced additional swirl to further enhance the heat transfer rate. The intensity of swirl created by the inserted tape depended on the twist ratio. Three different twist ratios (P/W) of 3, 5 and 7 (P is the pitch and W is the width of the tape) were examined. Simulation results revealed that decreasing the twist ratio of the tape augmented the heat transfer rate.

secondary flow, heat transfer, rotation rate, Nusselt number, twist ratio