Experimental study on thermal conductivity and viscosity of water-based nanofluids

Thermal conductivity and viscosity of deionized water-based TiO 2, SiO2, and Al2O3 nanofluids were investigated for various volume fractions of nanoparticles content and at different temperatures. A 3? technique was developed for measuring thermal conductivity of nanofluids. The theory and the experimental setup of the 3? measuring system is explained; a conductive wire is used as both heater and sensor in this system. At first, the system is calibrated using water with known thermophysical properties. Measured results showed that the effective thermal conductivity of nanofluids increases as the concentration of the particles increases but not anomalously as indicated in the majority of the literature and this enhancement is very close to the Hamilton-Crosser model; also this increase is independent of the temperature. The effective viscosities of these nanofluids increase by the increasing particle concentration and decrease with an increase in temperature, and cannot be predicted by the Einstein model. © 2010 Begell House, Inc