Nanofluids are colloidal solutions of nanometer sized particles in a base fluid. They exhibit enhanced thermal conductivity and viscosity compared to the base fluid from which they are prepared. The variation of thermal conductivity and viscosity of ethylene glycol based alumina and copper oxide nanofluids with respect to particle volume concentration and temperature were investigated. The increase in thermal conductivity values were slightly greater than the prediction of Hamilton Crosser model and the effective viscosity of nanofluids were much higher than the values predicted by Einstein-Batchelor model. No consistent trend was observed for temperature dependence of relative effective viscosity of nanofluids. The stability of nanofluids increased with increase in viscosity of the base fluid and decreased with increasing particle volume concentration. These results are helpful in extending the use of nanofluids to various fields such as industrial cooling and lubrication.
Keywords: cooling; nanofluids; thermal conductivity; viscosity; stability