Investigation of Various Cooling Nanofluids in a Partially Heated Horizontal Circular Tube

Enhancement of cooling performance of heat transfer fluids can contribute to downsizing of thermal systems. Analysis of thermal behavior of four cooling water based nanofluids (CuO, Al2O3, ZnO and SiO2) in a circular duct is carried. Modeling of heat transfer and fluid flow is based on 3D non-linear differential elliptical equations and finite volume method approach. The Brownian motion is considered in modeling of the nanofluid behavior. A code is developed based on SIMPLER and TDMA algorithms. Hydrodynamic and thermal fields are examined for nanoparticles volume fractions range 0% ≤ Φ ≤ 4% and spherical nanoparticles mean diameter in the range 27 nm ≤ dnp ≤ 78 nm. Results show that the local and circumferentially average Nusselt number increases with increasing the nanoparticles volume fraction and decreases with the nanoparticles size. The maximum local Nu is observed at the bottom of the duct. SiO2–water nanofluid shows the best thermal performance as well as the strongest secondary flow. Increasing the nanoparticles volume fraction increases the secondary flow strength. Using 4 vol.% nanoparticles of 27 nm mean diameter improves Nu by 12%, 7%, 5%, and 3.7% for SiO2, Al2O3, ZnO, CuO, respectively, when compared to the cooling performance of water alone.