Thermophysical and natural convection characteristics of ethylene glycol and water mixture based ZnO nanofluids

Stabilized nanofluids have been prepared by dispersing dry ZnO nanoparticles in different base fluids including 75:25, 85:15 and 95:5 (by volume) of ethylene glycol (EG) and deionized water (DW) mixtures. Thermal conductivity and viscosity experiments have been conducted at temperatures between 15 degrees C and 55 degrees C with mass fraction of nanoparticle of 5.25%. What's more, natural convection characteristics of EG/DW based ZnO nanofluids were also investigated. The thermal conductivity of nanofluid with more DW is bigger because the network of direct and tight connection in spatial structures between atoms expedites heat transfer between nanoparticles, and it increases with increasing the temperature as expected. Meanwhile, the viscosity of nanofluid increases with increasing the concentration of EG. When the temperature increases, the intermolecular distance becomes larger, which leads to the decrease of the viscosity. Natural convection experiment shows that the presence of nanoparticles deteriorates the natural convective heat transfer under present condition. (C) 2015 Elsevier Ltd. All rights reserved.