###### Abstract  
This article reports the effect of twisted tapes with continuous V-ribs on the thermal performance index characteristics of a heat exchanger tube. Numerical and experimental studies were conducted to investigate the influence of V-rib attack angles (\(\beta\) = 15\({}^{\circ}\), 30\({}^{\circ}\), and 45\({}^{\circ}\)) in forward and backward arrangements. This investigation employed 0.9 mm thick, continuous V-rib twisted tapes (CVRTs) made from aluminum sheets formed with a twist ratio of \(y/w\) = 4.0. The experimental results indicated that a continuous V-rib twisted tape (CVRT) was more effective in heat transfer improvement than a typical twisted tape (TT). This was due to swirl and longitudinal vortex flows that helped increase flow mixing and reduce boundary layer thickness. Decreased V-rib attack angles (\(\beta\)) led to greater heat transfer enhancement, pressure drop, and thermal performance index values due to the greater turbulent mixing of fluid. The numerical result revealed that a continuous V-rib twisted tape created strong longitudinal vortex flow, especially with higher attack angles. The Turbulent Kinetic Energy (TKE) and core fluid temperature increased with the insertion of CVRTs. Local Nusselt numbers also remained relatively high for heat exchanger tubes with CVRTs. The experimental study illustrated that a tube with a CVRT installed augmented heat transfer. In the experimentally studied cases, a backward arrangement had more heat transfer, a greater friction factor, and a better thermal performance index. Compared to a plain tube, a tube with CVRT installed, having \(\beta\) = 15\({}^{\circ}\), 30\({}^{\circ}\), and 45\({}^{\circ}\), showed 76.8, 71.6, and 66.2% improved heat transfer, respectively. CVRTs with these three \(\beta\)-values, respectively, exhibited higher thermal performance than a TT. Among the investigated CVRTs, the backward-arranged tape with \(\beta\) = 15\({}^{\circ}\) offered the maximum thermal performance index, 1.13 at \(Re\) = 6000. The results are congruent with the simulation outcomes, hence supporting the CFD analysis. continuous V-rib twisted tape; heat transfer; swirling flow; twisted tape 202515561202556120255612025561202556120255612025561202556120255612025561202556120256120255612 fundamental component in heat transfer systems, directly influences system efficiency [1; 2]. The global energy consumption in industries is expected to increase by 40% by the year 2040 [3]. Augmenting heat thermal performance has become a crucial strategy for reducing energy consumption and operating costs. Increasingly, researchers are investigating active and passive approaches to improve heat transfer and enhance thermal performance. Among the heat transfer enhancements, those that utilize inserted devices have significantly enhanced the performance of conventional heat exchangers. Researchers frequently employ twisted tapes to improve the performance of heat exchange tubes because of their reliability, uncomplicated design, and ease of installation. The use of twisted tapes has two opposing effects: a disadvantageous pressure drop and an advantageous heat transfer augmentation [4; 5]. These phenomena are caused by (1) intensification of turbulence and disruption of the boundary layer region, (2) an enlarged heat transfer region, and (3) creation of swirling flows [6; 7; 8]. Researchers have systematically optimized heat exchangers with twisted tape insert augmentation through three-dimensional parametric studies. These include modifying tape geometry (e.g., twist ratio, edge curvature), configuration or multiple tape configurations (e.g., co/counter-swirl arrangements), and working fluid selection (e.g., nanofluids, phase-change slurries). [PERSON] et al. [2] examined the thermohydraulic performance behaviors of AIN-Al\({}_{2}\)O\({}_{3}\)/water hybrid nanofluids with twisted tapes mounted in a tube. Twisted tapes with various twist pitches were selected. The Reynolds numbers ranged from 800 to 2000.