Thermo-physical properties of engineered dispersions of nano-sand in propylene glycol

Stable sand–propylene glycol nanofluids were formulated by dispersing sand nanoparticles (20–25 nm) produced by stirred bead milling, in propylene glycol through extended probe ultrasonication. The viscosity of sand–propylene nanofluids decreases with nanoparticle concentration (0–2 vol%) and temperature (29–140 °C). In the well-dispersed nano-sand–propylene glycol dispersion, interactions between nanoparticles and propylene glycol through nanoparticles’ surface led to disturbance of hydrogen bonding network of propylene glycol. This is manifested as reduction in viscosity of dispersion in comparison to pure propylene glycol. For instance, the viscosity of 2 vol% nanofluid was found to be 46% lower than that of pure propylene glycol at 29 °C. The study of influence of nanoparticle concentration and temperature (10–50 °C) on thermal conductivity reveals linear increase of thermal conductivity with nanoparticle concentration. Higher thermal conductivity enhancement at lower temperatures (46.2% for 2 vol% nanofluid at 10 °C) reveals the role of ordered liquid layers toward thermal conductivity enhancement in well-dispersed nano-sand–propylene glycol dispersion.