Investigating the effect of perforated helical fins on the hydrothermal performance of a double pipe heat exchanger

The current research aims to improve the performance of the counter-flow heat exchanger for a double tube heat exchanger numerically and experimentally in the Reynolds number range between 2000 and 4000. To maximize heat transfer of the heat exchanger under study, a passive method of enhancement of heat transfer was used by using helical fins perforated on the annular side with different diameters of 3, 5, and 7 mm. These fins act as vortex flow devices, creating turbulent conditions for the boundary layers of the fluid, thus increasing the heat transfer coefficient. The numerical results of the current study have been obtained by using the ANSYS Fluent 2022 program. The results show a good agreement between the numerical and experimental findings of the traditional model of the current study and the results of previous studies. Furthermore, the findings showed that the comparison between the numerical and experimental results of the optimum model is identical. Moreover, it was found that the best model among the new models is when a 20 mm pitch is combined with a 10 mm spiral height and a 5 mm hole diameter. In addition, the friction factor of the best model decreases by 20.046%, the overall heat transfer coefficient increases by 67.915%, and the Nusselt number increases by 63.954% compared to the conventional model. The highest value in thermal performance for the best model is 1.855% compared to the conventional model.