Thermohydraulic and entropy generation analysis of variable-width tape inserts in heat exchangers

The implementation of variable-width twisted tape (VBTT) inserts in heat exchangers is a widely used method for enhancing heat transfer rate and thermal performance. Accordingly, the present study aims to investigate heat transfer, friction factor, and the thermo-hydraulic performance index (TPI) using a 3D numerical simulation approach. The working parameters are varied, namely, the varying widths ( b = 16, 18, and 20 mm) and the Reynolds number ( Re ) range of 6000–16,000, to simulate under a turbulent regime with water as the working fluid. The results show that the heat transfer and friction factors increase by 29.05%–85.64% and 134.28%–271.93%, respectively. The 20 mm tape yields the best performance index results, with a value of 1.27 at a low Re of 6000. By using the second law of thermodynamics, thermal entropy generation, friction entropy generation, total entropy generation and Bejan number ranging from 0.045–0.125, 0.008–0.142, 0.053–0.267 and 0.84–0.46, respectively, for all Re . This performance is attributed to variable-width tape-induced secondary swirl flow, which disrupts the near-wall boundary layer, augments convection and moderates pressure penalties under cube-root weighting in TPI. The mathematical correlations exhibit a maximum deviation of ±8.32% and ±9.84% for the Nusselt number and friction factor, respectively. The results from this study could serve as a valuable resource for engineers and researchers involved in modern heat exchanger design.