Numerical investigation of heat transfer and fluid flow of water through a circular tube induced with divers' tape inserts

•Heat transfer and flow characteristic of water through different tube designs are analysed numerically.•Disturbance of boundary layer by twisted tape generates an enhancement of heat transfer.•Thermo-hydraulic performance of the flow system is affected by the shape of cut on the twisted tape.•The tube with alternate-axis triangular cut twisted tape has the best performance with a thermal performance factor of 1.43.•Nusselt number of the novel correlation agrees with that of the established correlation with a variation of 2.21%. An investigation was carried out to analyse numerically heat transfer and flow characteristics of water through a circular tube induced with different twisted tapes. The aim is to know which of the tube designs gives the best performance when compared with a plain tube. Turbulent flow was considered, the walls of the tubes were under uniform wall heat flux, Reynolds number was between 5000 and 20,000, and RNG κ-ε model was selected for the simulations. The shape of cuts on the tapes has effects on the performance of the induced tubes. The tube fitted with alternate-axis triangular cut twisted tape has the best performance as its Nusselt number and friction factor are 1.63–2.18 and 2.60–3.15 times, respectively, that of the tube fitted with plain twisted tape while its thermal performance factor is 1.35–1.43 times that of the tube with plain twisted tape. New correlations were developed for the Nusselt number and friction factors, and reveal that the Nusselt number obtained from the new correlation agrees well with the correlation proposed by Thianpong et al. with a discrepancy of 2.21%. For the friction factor, the discrepancy is 3.01%.