Optimization of thermal resistance and thermal deformation in high heat-load zone of blast furnace cooling staves

Blast furnace longevity is critically limited by the degradation of cooling staves in high heat-load zones, where excessive thermal deformation and inefficient heat dissipation accelerate structural failure. Proper temperature control of these staves is essential to mitigate such issues. The total thermal resistance from furnace gas to the environment consists of fixed and optimizable components. While the fixed thermal resistance is inherent to the furnace design, the optimizable convective resistance between working fluids and tube walls remains a key target for improvement, as conventional cooling methods (e.g., water in smooth tubes) struggle to balance heat extraction efficiency with mechanical durability under extreme thermal loads. Here, numerical simulations investigate the thermal performance of four configurations: water, CuO/water nanofluid, and Al2O3/water nanofluid in smooth or internally-ribbed tubes. Compared to the baseline (water in smooth tubes), the synergistic combination of 5 vol% Al2O3/water nanofluid and internally-ribbed tubes reduced optimizable thermal resistance by 72.03% and maximum thermal deformation by 17.58%, while increasing the heat transfer coefficient by 169.11%. These improvements stem from two mechanisms: (1) rib-induced asymmetrical vortices and swirling flows that disrupt thermal boundary layers and enhance fluid mixing, and (2) nanoparticle-driven conductive pathways that augment heat transfer via liquid-nanoparticle interactions. The results demonstrate a promising strategy to address the longstanding challenge of cooling stave degradation in blast furnaces, directly linking reduced thermal resistance to lower wall temperatures and suppressed deformation-critical factors for extending furnace lifespan.