Measuring the Temperature-Dependent Thermal Conductivity and Viscosity of Silver-Water Nanofluids

This paper presents the measurement of the temperature dependent property such as the thermal conductivity and viscosity of silver nanoparticles suspended in water as nanofluids. The experiments were carried out over the temperatures ranging from 50°C to 90°C with 0.4%, 0.8%, and 1.2% volume concentrations. A transient hot-wire apparatus is used for measuring the thermal conductivity of nanofluids whereas the Cannon-Fenske viscometer is used to measure the viscosity of nanofluids. The results showed that the measured viscosity and thermal conductivity of nanofluids increased as the particle concentrations increased and are higher than the values of the base liquids. The minimum enhancement of 35% for 0.4 vol% and a maximum enhancement of 115% for 1.2 vol% concentration are observed at an average temperature of 70°C when compared with pure water for the same temperature. Furthermore, thermal conductivity of nanofluids increased with increasing nanofluid temperatures and, conversely, the viscosity of nanofluids decreased with increasing temperature of nanofluids. It was also observed that there exists a strong temperature effect on the thermal conductivity enhancement of nanofluids and the non-applicability of the Hamilton-Crosser model at elevated temperature with low volume fraction of pure metal nanoparticles.