Thermal conductivity of Al2O3/water nanofluids

Nanofluids, fluids with suspended nanoparticles, are of interest as a novel material for improving heat transfer efficiency. The conventional theory of two-component mixtures cannot explain the large enhancement of thermal conductivity of nanofluids. It is to be expected that the thermal conductivity of nanofluids is related with many factors, such as that effect of surfactants, dispersion of particles, convection or Brownian motion of nanoparticles, etc. but the mechanism is not known. Thermal conductivity of Al2O3 nanofluids is studied in this work and compared with that of Fe nanofluids. To study the effect of pH of the base fluid on thermal conductivity, we measured the thermal conductivity of Al2O3 nanofluids with different pH values. Al2O3 nanoparticles were dispersed in water of pH values such as 7.0, 9.65 and 10.94. Nanoparticles have a tendency to form clusters, due to van der Waals interaction resulting in reduction of thermal conductivity. It is understood from the variation of thermal conductivity as the pH value of base fluids varies that the pH of base fluids affects clustering of nanoparticles.