Effect of Laminar Flow of Non-Newtonian Nanofluid in a Horizontal Backward-Facing Step Channel

This study presents a numerical investigation of the hydrothermal performance of non-Newtonian nanofluids in a two-dimensional backward-facing step (BFS) channel. The effects of power-law index (n), nanoparticle volume fraction (φ = 0–4.5%), and nanoparticle type (Al2O3, TiO2, CuO, and Cu) were examined using CMC/water as the pseudoplastic base fluid. The analysis focused on velocity distribution, velocity gradients, and both local and average Nusselt numbers. The results indicate that shear-thinning behaviour (n < 1) enhances flow development and heat transfer compared to Newtonian fluids. Increasing nanoparticle concentration improved both local and average Nusselt numbers, with Al2O3/CMC nanofluid consistently exhibiting the highest performance due to its superior thermal conductivity. The findings demonstrate that the combined effects of non-Newtonian rheology and nanoparticle addition substantially augment convective heat transfer, offering useful insights for the design of efficient heat exchange systems.