Numerical investigation of heat exchanger enhanced with different peripherally-cut twisted tapes by using nanofluids

This study numerically investigates heat transfer augmentation using CuO nanofluids flowing in a circular tube equipped with the alternation of clockwise and counterclockwise twisted tape inserts under constant heat flux in laminar flow conditions. The simulation experiments were carried out on the twisted tape with three types of edge notches (triangle-cut, semicircle-cut and rectangle-cut) under laminar flow (400 <= Re <= 1800) conditions and compared with Plain twisted tapes. The Nusselt number, friction factors and performance evaluation criteria of different twisted tapes were obtained for various Reynolds numbers. The results revealed that the Nusselt number increases with the increase of Reynolds number while the friction factor shows an opposite trend for all cases. The Nu number increases 389.9% by using clockwise and counterclockwise twisted tape instead of plain tube at Re =1800. Circular tubes equipped with all types of inserts have higher heat transfer performance than plain tube. The presence of the notch interferes with the disturbance of the twisted tape to the fluid, so that leads to the reduction of the heat transfer enhancement performance of tape. The comprehensive 0evaluation decreases with the increase of notch area. It is also found that the application of nanofluids can improve the heat transfer performance. The maximum value of the thermal performance 2.27 is achieved by using alternation of clockwise and counterclockwise twisted tape and 1.2% CuO nanofluids at Re =1800.