CFD investigation was carried out to study the heat transfer characteristics of air flow inside a circular tube with a fully decaying, partially decaying and partly swirl flow. Four combinations of tube with twisted-tape inserts, half-length upstream twisted tape condition (HLUTT), half-length downstream twisted tape condition (HLDTT), full-length twisted tape (FLTT), inlet twisted tape (ILTT) are considered along with plain tube (PT) for comparison.. Three different twist parameter, ? = 0.14, 0.27, and 0.38, for twisted tape configuration have been studied for the above four configurations. 3D numerical simulation was performed for an analysis of heat transfer and fluid flow for turbulent regime. The results of CFD investigations of heat transfer, and friction characteristics are presented for the FLTT, HLUTT, HLDTT and the ILTT along with a velocity and temperature profiles analysis in comparison with the PT case. Keywords: HLUTT, HLDTT and FLTT, enhancement, Tape inserts, partially decaying swirl flow
