Numerical study on heat transfer enhancement using twisted tape with trapezoidal ribs in an internal flow

Abstract The enhancement of the heat transfer rate in the heat exchanger is imperative for decreasing the overall cost of its operation. A popular way to increase the performance of these heat exchangers is by use of plain twisted tape, twisted tape with perforation, twisted tape with peripheral cuts, helical inserts, etc. In this paper, a novel twisted tape with trapezoidal ribs has been introduced and numerical investigation has been carried out. The proposed insert created a swirl motion and increased the turbulence intensity in fluid flow in the tube. The CFD simulation has been performed in the turbulent flow regimes with Reynolds number varying from 4000 to 12000. The inclination of ribs has been varied from 30° to 60° and their effects on heat transfer characteristics have been extensively studied. The highest Nusselt number and friction factor are observed with a slant angle of 60° but the thermal performance factor is found highest with a slant angle of 30°. The results are in good agreement with Promvonge model. It is found that the main cause for augmented heat transfer rate observed in twisted tape with trapezoidal ribs is due to higher turbulence intensity induced by trapezoidal ribs.