Effects of Macroparameters on the Thickness of an Interfacial Nanolayer of Al2O3- and TiO2-Water-Based Nanofluids

In this paper, thicknesses of interfacial nanolayers of alumina-deionized water (DW) and titanium dioxide-deionized water (DW) nanofluids are studied. Thermal conductivities of both nanofluids were measured in a temperature range of 298 to 353 K at particle volume ratios of 0.2 to 1.5% by experiments. A theoretical model considered both the effects of the interfacial nanolayer and Brownian motion is developed for thermal conductivity. A relational expression between nanolayer thickness and bulk temperature and volume fraction of particles of nanofluids is derived from the theoretical model. With the experimental data of thermal conductivity, changes of nanolayer thickness with nanofluids macroscopic properties (bulk temperature and particle volume ratio) are obtained. The present results show that nanolayer thickness increases with fluid temperature almost linearly and decreases with particle volume fraction in a power law. Based on the present results, simple formulas of interfacial nanolayer thickness as a function of fluid temperature and particle volume fraction are proposed for both water-based nanofluids.