The Effect of Nanoparticle Concentration on Thermo-physical Properties of Alumina-nitrate Nanofluid

The objective of this study was to determine how Al2O3 nanoparticle concentration affected the specific heat, heat of fusion, melting point, thermal diffusivity and thermal conductivity of Alumina-Nitrate nanofluids. Al2O3 nanoparticles were dispersed in a eutectic of sodium nitrate and potassium nitrate (60:40 for mole fraction) to create nanofluids using a hot plate evaporation method and an air dryer method. The nominal Al2O3 (alumina) mass fraction was between 0 and 2%, and was determined as the ratio of the mass of Al2O3 nanoparticles to the total mass of the nanofluid. After the preparation of the nanofluids, Neutron Activation Analysis (NAA) was used to measure the actual Al2O3 mass fraction in the nanofluids. The specific heat, heat of fusion, and melting point were measured with a Modulated Differential Scanning Calorimeter (MDSC). The thermal diffusivity and thermal conductivity were measured with Laser Flash Analysis (LFA). The MDSC results showed that the addition of Al2O3 nanoparticles enhanced the specific heat of the nanofluids synthesize from both methods. There was a parabolic relation between the specific heat and the Al2O3 mass fraction for the nanofluids synthesized from the hot plate evaporation method, with a maximum 31% enhancement at 0.78% Al2O3 mass fraction. The nanofluids synthesized from the air dryer method also resulted in enhanced specific heats which were higher at the same Al2O3 mass fraction than those of the nanofluids synthesized from the hot plate evaporation method. It was not determined why this enhancement occurred. The results also showed that the introduction of Al2O3 nanoparticles had no significant effect on the heat of fusion and melting point of the nanofluids synthesized from either method. The LFA results showed that adding Al2O3 nanoparticles decreased the thermal diffusivity and the thermal conductivity of the nitrate eutectic