Heat Transfer Enhancement in a Heat Exchanger Tube Using Twisted Tapes with Circular and Hexagonal Perforations

Improving heat transfer is crucial for enhancing energy efficiency and reducing operational costs in thermal systems. This study is motivated by the need to develop compact and cost-effective heat exchangers through the use of passive enhancement techniques. In particular, twisted tape inserts have gained significant attention due to their ability to intensify fluid mixing and disrupt thermal boundary layers. The aim of this study is to numerically investigate the thermal and hydraulic performance of a circular pipe equipped with three types of inserts: plain twisted tape (TT), circular-perforated twisted tape (CPTT), and hexa-perforated twisted tape (HPTT). Using ANSYS Fluent and the finite volume method, simulations were performed under constant heat flux for Reynolds numbers ranging from 5000 to 20000. The results show that all twisted tape configurations considerably improve heat transfer compared to a plain tube, with Nusselt number enhancements of up to 62.37% for TT, 65.85% for CPTT, and 76.27% for HPTT. These enhancements are accompanied by increased friction factors of 150.68%, 154.31%, and 176.05%, respectively. The highest performance evaluation criterion (PEC) of 1.25 was achieved by the CPTT, indicating its optimal thermal-hydraulic balance. The findings of this study are relevant to the design and optimization of heat exchangers in various industrial applications, including solar thermal systems, chemical processing, and HVAC systems.