A CFD Study And Comparison Of Different Nanoparticles-Water Combinations Flow And Conjugate Heat Transfer Performance In A 3-D Rectangular Duct

Abstract

In this study, a three-dimensional numerical investigation is performed to evaluate the conjugate heat transfer performance of nanoparticles–water mixtures in a rectangular duct under steady, laminar flow conditions. The working fluids include Al₂O₃–water, CuO–water, and TiO₂–water, treated as homogeneous single-phase media with effective thermophysical properties determined by nanoparticle concentration. A constant heat flux is applied to the heated duct walls, while no-slip conditions are imposed at all fluid–solid boundaries. The governing equations for continuity, momentum, and energy are solved using a finite-volume based CFD approach to obtain detailed hydrodynamic and thermal characteristics. The analysis emphasizes the variation of velocity profiles, friction factor, overall heat transfer coefficient, and local Nusselt number. Simulations are conducted over a range of Reynolds numbers and nanoparticle volume fractions to capture the combined effects of flow intensity and particle loading. Results reveal that nanofluid suspensions significantly enhance convective heat transfer relative to the base fluid, with both the overall heat transfer coefficient and Nusselt number increasing with nanoparticle concentration. Higher Reynolds numbers further strengthen convective transport, confirming the synergistic role of inertia and nanoparticle dispersion. Among the nanofluids studied, Al₂O₃–water demonstrates the most balanced thermal enhancement, while CuO–water and TiO₂–water show comparatively lower but still notable improvements. The computational predictions were validated against available velocity data, ensuring model reliability. Overall, the comparative analysis confirms that nanoparticle–water mixtures can substantially enhance heat transfer in confined ducts, although optimization between thermal benefits and hydrodynamic penalties is essential. The findings provide valuable insight into nanofluid selection for advanced thermal system design.