A computational study of heat transfer analysis for a circular tube with conical ring turbulators

One of the techniques used for heat transfer enhancement is inserting conical rings inside the tube to act as turbulators. In the present work, the performance of these conical inserts is investigated numerically. Air is used as the working fluid with Reynolds number (Re) range of 6000-25000. Conical ring inserts were applied through three configurations of; convergent conical rings (CR), convergent divergent conical rings (CDR) and divergent conical rings (DR). Each arrangement with diameter ratios of (d/D = 0.3, 0.4, 0.5, 0.6, and 0.7) and pitch ratios of (PR = 2, 3, and 4) were employed. Both Nu and f increased with the decrease in the conical ring d/D and PR. The average Nu obtained from using (CR), (CDR) and (DR) arrays were found to be 330%, 419% and 765% more than Nu of the plain tube, respectively. The best enhancement tube efficiency was found to be 1.291 for the divergent ring with d/D = 0.4 and PR = 2 for Re of 6000. The entropy generation increased with the increase in Re for all the conical ring cases. Also, entropy generation increased with the decrease in the d/D. A new correlation was proposed for Nu, f and the enhancement tube efficiency with variable parameters and compared with published experimental data from the literature.