Synergistic enhancement of convective heat transfer using bio-inspired half-petal ribs and engineered nanofluids

This study numerically investigates turbulent forced convection in a rectangular channel fitted with novel bio-inspired half-petal ribs and cooled by water-based nanofluids. The impact of rib pitch ratio (P/e = 5–20), Reynolds number (4000–16000), nanoparticle type (Al₂O₃, CuO, MgO, TiO₂, and SiO₂), volume fraction (0–3%), and nanoparticle diameter (30–60 nm) on thermo-hydraulic performance are examined in term of Nusselt number, friction factor, and performance evaluation criterion (PEC). The flow and heat transfer fields are solved using the finite volume method in ANSYS Fluent, utilizing the standard k − ϵ turbulence model with enhanced wall treatment. The results show that the half-petal ribs intensify flow separation, recirculation, and vortex formation, leading to a substantial heat transfer enhancement compared with the smooth channel. The optimal thermal performance is achieved at the minimal pitch ratio (P/e = 5), resulting in Nusselt values that are 2.94 times greater than those of a smooth channel. Additional performance enhancement was attained with the introduction of nanofluids, with SiO₂-water demonstrating the highest significant Nusselt number increase of 9.89% at a 3% volume fraction. The optimal rib design (P/e = 5) combined with a 3% SiO₂-water nanofluid of 30 nm particles attains the maximum PEC of 1.815 atRe = 4000, thereby separating thermal enhancement from the rise in proportional flow resistance. The integrated method illustrates that meticulously designed surface roughness and the selection of nanofluids can successfully dissociate heat transfer enhancement from corresponding increases in flow resistance, presenting a feasible solution for advanced thermal management systems.