Measurement of the Thermal Conductivity of Silicon Dioxide Nanofluid and Development of Correlations

Abstract

Experimental investigations were carried out for the determination of thermal conductivity of silicon dioxide (SiO2) nanoparticles dispersed in 60% ethylene glycol and 40% water by mass. Experiments conducted in a temperature range of 20 °C to 90 °C and for several particle volumetric concentrations up to 10% showed that the ratio of thermal conductivity of nanofluid to that of the base fluid increased with an increase in temperature and volumetric concentration. As an example, as much as a 20% enhancement in thermal conductivity was evidenced for a particle volumetric concentration of 10% at 87 °C. Comparison of experimental results of this nonmetallic nanoparticles suspension with the well-known model developed by Hamilton and Crosser for microparticles suspensions, exhibits that this model underpredicts the thermal conductivity of nanofluids. Therefore, a new correlation has been derived following recent models developed for metallic nanoparticles suspensions, which is a combination of the Hamilton–Crosser model plus a term due to the Brownian motion. This new correlation expresses the thermal conductivity of silicon dioxide nanofluid as a function of temperature, volumetric concentration and the properties of the base fluid and the nanoparticles.