Numerical study of turbulent flow inside heat exchangers using perforated louvered strip inserts

Numerical simulations have been performed to analyze the turbulent flow characteristics and thermal performance of fluid flows inside heat exchangers fitted with novel perforated louvered strip inserts with different slant angles. The (RNG) k-epsilon is employed for the numerical simulations with the Reynolds number in the range of 5000-14,000. The results demonstrate that the recirculation flow through the holes of perforated louvered strips significantly improves the Nusselt number and thermal enhancement factor compared to the louvered strips without holes. Better fluid mixing between the tube walls and core region is the main physical reason for heat transfer augmentation. The recirculation flow through the holes of the perforated louvered strips significantly intensifies the flow disturbance and thus, the turbulent kinetic energy values near the holes increases. The effects of double mounted louvered strips on the axial velocity and turbulent kinetic energy are also investigated. The results show that the average Nusselt numbers for the cases of double perforated louvered strip with theta = 15 degrees and 25 degrees are 30.1% and 45.84%, respectively, higher than single perforated louvered strip with the same slant angles. The maximum thermal enhancement factor of 1.84 can be obtained by employing double perforated louvered strip with theta = 25 degrees at Re=14,000. (C) 2019 Elsevier Ltd. All rights reserved.