Investigating the Performance and Thermal Characteristics of Turbulent Flow in a Heat Exchanger Tube with Gridded Oval Slant Inserts

The present study numerically investigated the modified oval turbulator effect and its gridding with a 25-degree slant angle in the turbulent flow inside the heat exchanger tube to achieve optimal performance. A review of past research indicates that grid turbulators have been employed infrequently. This issue inspired the authors of this article to implement this new concept and layout. The innovative geometry of this turbulator prevents a high-pressure drop and improves heat transfer. To this end, three grid values ( G = 9, 16, and 25) in pitch ratio PR = 2 are considered to study their influence on thermal characteristics, pressure drop, and thermal performance, respectively. The present study employs the finite volume method and the k-ε: RNG model for numerical solutions in Re = 5000–18000. The results indicated that the Nusselt number for the oval inserts with G = 25, 16, and 9 grids increased by 85.9, 73.2, and 55.6%, respectively, compared to the smooth tube. Furthermore, the thermal performance of gridding with G = 25 and 16 was 1.16 and 1.09 times higher than that of gridding with G = 9, respectively. The highest thermal performance coefficient for the gridded oval was 25% higher than the typical oval ring at Re = 5000. The findings demonstrated that recirculation flows through the turbulator holes and the thermal boundary layer disruption are the physical causes of enhanced heat transfer. In addition, the maximum η of 1.4 was recorded for turbulators at PR = 2 and G = 25.