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Nano materials have made a revelation in all fields of engineering and technology. Materials of size less than 100 nm are termed as nano materials. The excellent properties of nano materials have attracted the scientists and engineers more towards nano technology. Solid nano particles dispersed in the base fluids such as water or ethylene glycol are called nanofluids, especially used to increase the heat transfer capability of base fluids. In this work we have synthesized Al2O3-Cu nano composite powder in a thermo chemical route that involves the preparation of precursor powder from metal nitrates and hydrogen reduction technique. Two different proportions of precursors were used to obtain the nano composites of two different proportions. The prepared powder was characterised using XRD, SEM and EDS. Water based hybrid nanofluids were prepared and their stability have been studied for different volume concentrations.

A study on fully developed turbulent convective heat transfer and pressure drop characteristics of Al2O3-Cu/water hybrid nanofluid flowing through a uniformly heated circular tube is presented in this paper. For this, Al2O3-Cu nanocomposite powder was synthesized in a thermo chemical route using hydrogen reduction technique and dispersed the hybrid nano powder in deionised water to form a stable hybrid nanofluid of 0.1% volume concentration. The prepared powder was characterized by X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM) to confirm the chemical composition, determine the particle size and study the surface morphology. Stability of the nanofluid was ensured by pH and zeta potential measurements. The average heat transfer enhancement for Al2O3-Cu/water hybrid nanofluid is 8.02% when compared to pure water. The experimental results also showed that 0.1% Al2O3-Cu/water hybrid nanofluids have slightly higher friction factor compared to 0.1% Al2O3/water nanofluid. The empirical correlations proposed for Nusselt number and friction factor were well agreed with the experimental data.

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