A formulation strategy for preparation of ZnO–Propylene glycol–water nanofluids with improved transport properties

Experiments were carried out on the influence of nanoparticle–liquid interactions on transport properties (viscosity and thermal conductivity) of ZnO–Propylene glycol–water nanofluids. Our experiments show that the preparation of ZnO–Propylene glycol–water nanofluid through addition of water to well-dispersed ZnO–Propylene glycol dispersion results in decreased viscosity and increased thermal conductivity, in comparison to that of propylene glycol–water mixture, due to favourable nanoparticle–liquid interaction. Such nanofluids are stable even without addition of any stabilizing agent. The study of influence of nanoparticle concentration (⩽2vol%) and temperature (15–50°C) on thermal conductivity reveal higher thermal conductivity enhancements at lower temperatures. This could be attributed to layering of propylene glycol molecules on surface of ZnO nanoparticles. The presence of liquid layers was ascertained through thermal analysis and infrared spectroscopy.