Experimental Validation of Analytical Predictions for the “Deviant” Density of Oleo-Nanofluids Based on the nanoFin Effect

Abstract

Experimental validation of the analytical predictions for the “deviant” density enhancement of nanofluids is presented in this study. Experimental measurements of density were complemented by transmission electron microscopy (TEM) of these nanofluid samples. The analytical model predicts the effective density of the nanofluid as a function of the mass fractions and densities of the nanoparticle, the base solvent, and the “compressed phase” of the solvent encapsulating the nanoparticle. In this study, casein is used as the nanoparticle candidate at a mass fraction of 1% and paraffin oil (which is essentially a phase change material (PCM)) is used as the neat solvent (base fluid). The experimental measurements demonstrate anomalous enhancement of the density of the oleo-nanofluids, which is 7% in excess of the value predicted by the conventional mixing rule (with a measurement uncertainty less than 1.2%). The formation of a compressed phase within the nanofluid domain is responsible for the “surplus” density (deviant density) of the oleo-nanofluid. The predicted values are found to closely match the actual dimensions of the nanostructures measured in the TEM images, hence conclusively validating the numerical model for estimating the magnitude of the deviant density contributed by the compressed phase. This also confirms the presence of a compressed phase (which is a consequence of the “nanoFin effect”), that was investigated and validated in this study. This surplus densification in hydrocarbons (such as PCM and oil-based nanofluids) makes them potentially attractive candidates as radiation shielding materials (e.g., for deep space exploration applications).