Al2O3–Cu hybrid nanofluid flow and heat transfer characteristics in the duct with various triangular rib configurations

This study examines the turbulent heat transfer characteristics of Al₂O₃–Cu hybrid nanofluids in circular ducts with triangular rib configurations. Numerical simulations were conducted for a 25 cm long, -cm high duct with walls maintained at 313 K. Hybrid nanofluids enter at 298 K, with triangular ribs on the internal surface at three attack angles (45°, 60°, and 90°) spaced 20 mm apart. Al2O₃–Cu/H₂O hybrid nanofluids at concentrations of 0.1–2 vol.% were investigated for Reynolds numbers between 20,000 and 60,000. The study aimed to determine the optimal rib configuration and nanofluid concentration for enhancing heat transfer while minimizing friction losses. Key findings include: (1) the 60° rib configuration produced the highest local heat transfer coefficient, with the maximum occurring at the rib centers. (2) Increasing nanofluid concentration and Reynolds number enhanced heat transfer but reduced skin friction. (3) The optimal performance was achieved with 2 vol.% Al₂O₃–Cu at Re = 60,000. (4) Velocity contours revealed larger recirculation zones for 60° ribs compared to 45° and 90° configurations. (5) Turbulent kinetic energy was highest for 60° ribs, contributing to enhanced thermal performance. These findings have implications for improving the efficiency of heat exchangers, cooling systems, and other thermal management applications.