Enhancing heat transfer performance in a double tube heat exchanger: Experimental study with twisted and helical tapes

Efficient energy exchange is vital for designing compact and effective heat exchangers. This study investigates various twist ratios for tape inserts and exterior helical tape in a counterflow setup using water as the working fluid. Reynolds numbers are varied on both sides of the heat exchanger. The analysis reveals that incorporating twisted tape inserts inside the pipe, along with helical tape on the exterior, significantly enhances thermal characteristics. Compared to a plain pipe heat exchanger, Nusselt numbers increase by 219 %-315 % for the pipe with twisted tape inserts and helical tape. Friction factors are also higher, ranging from 4.4 to 8.7 times for pipe inserts with twist ratios of 6.77, 4.51, and 3.38. An empirical relationship between Nusselt number and friction factor is derived from experimental data, demonstrating remarkable agreement with predicted values. A maximum thermal performance factor (TPF) of 3.06 is achieved, emphasizing the critical role of twist ratios in optimizing heat transfer efficiency while minimizing energy consumption. These findings provide valuable insights for designing energy -efficient heat exchangers with enhanced heat transfer rates.