Effect of twisted tape with rotating vane angles on performance of double-pipe heat exchanger

This study investigates the influence of primary swirl induced by a twisted tape (TT) and secondary swirl generated by rotating vanes on the performance of a double-pipe heat exchanger. A novel aspect of this work is the detailed examination of varying vane angles (15°, 30°, 45°, and 60°), a parameter rarely explored in prior studies, to optimize thermal performance. Experiments were conducted using water as the working fluid across a Reynolds number range of 5500 to 10,000. Results reveal significant heat transfer enhancements, with improvements of up to 102.54% for a vane angle of 60° compared to TT alone. However, the performance evaluation criterion of 1.49 identifies 30° as the optimal vane angle, balancing enhanced heat transfer and acceptable friction losses. Regression analysis confirms the strong correlation between vane angle, Nusselt number (R² = 0.9865), and friction factor (R² = 0.9993). Experimental validation demonstrates excellent agreement between correlation predictions and measured values within ±10%. This study offers valuable insights into optimizing passive heat transfer enhancement techniques.