Numerical analysis of heat transfer and turbulent flow friction in a tube equipped with perforated double conical rings

Abstract A numerical analysis was performed to investigate the properties of heat transfer and flow of fluid movement in a tube fitted with perforated double conical rings (PDCRs). This research numerically investigates the PDCR’s impact on the thermal performance factor (PEC), Nusselt number (Nu), and friction coefficient (f). The perforated double conical rings (PDCRs) used have varied numbers of slots ( n = 0, 2, 4, and 6) and perforated holes ( N = 4, 8, and 10), as well as varied pitch ratios (PR = 4, 6, and 12). The analysis is performed under turbulent flow conditions at various Reynolds numbers (Re) (4000 ≤ Re ≤ 18,000), employing the SST k-ω turbulence model, with air as the working fluid. The PDCRs improved flow mixing across the core and near-wall regions and significantly increased the turbulent intensity within the tube. PDCRs efficiently break down the thermal boundary layer by generating high-intensity turbulence close to the tube walls, thereby improving convective heat transfer. This disturbance promoted improved chaotic mixing between the near-wall and core regions, hence increasing heat exchange efficiency. Additionally, the jet formations generated by the PDCRs near the core region played a vital role in enhancing mixing between the tube wall and the central flow, thus contributing to improved overall thermal performance. The outcomes suggested that PDCRs could enhance the heat transfer rate by up to approximately 187% relative to a plain tube. The highest thermal performance factor, approximately 0.978, was achieved at PR = 6, with 8 holes and 4 slots, at a Reynolds number of 14,000 within the examined range.