Experimental investigations and theoretical determination of thermal conductivity and viscosity of Al2O3/water nanofluid

Experimental investigations and theoretical determination of effective thermal conductivity and viscosity of Al2O3/H2O nanofluid are reported in this paper. The nanofluid was prepared by synthesizing Al2O3 nanoparticles using microwave assisted chemical precipitation method, and then dispersing them in distilled water using a sonicator. Al2O3/water nanofluid with a nominal diameter of 43 nm at different volume concentrations (0.33-5%) at room temperature were used for the investigation. The thermal conductivity and viscosity of nanofluids are measured and it is found that the viscosity increase is substantially higher than the increase in thermal conductivity. Both the thermal conductivity and viscosity of nanofluids increase with the nanoparticle volume concentration. Theoretical models are developed to predict thermal conductivity and viscosity of nanofluids without resorting to the well established Maxwell and Einstein models, respectively. The proposed models show reasonably good agreement with our experimental results. (C) 2009 Elsevier Inc. All rights reserved.