Parametric study on turbulent heat transfer and flow characteristics in a circular tube fitted with louvered strip inserts

In the present work, characteristics of heat transfer, flow resistance, and overall thermo-hydraulic performance of turbulent airflow in a circular tube fitted with louvered strip inserts were investigated through numerical simulation. Our main attention was paid to the effects of the slant angle and pitch of the turbulators. The results show that the Nusselt number is augmented by 2.75–4.05 times (Nu = 108.71–423.87) as that of the smooth tube. The value of performance evaluation criterion (PEC) lies in the range of 1.60–2.05, which demonstrates that the louvered strip insert has a very good overall thermo-hydraulic performance. Moreover, the computational results indicate that larger slant angle and small pitch can effectively enhance the heat transfer rate, but also increase the flow resistance. Furthermore, it is noted that the Nusselt number and friction factor are more sensitive to the slant angle than the inserts pitch. Comparatively steady and good overall thermo-hydraulic performance can be obtained at a moderate slant angle together with a small pitch. All these data show that the louvered strip is a promising tube insert which would be widely used in heat transfer enhancement of turbulent flow.