Thermal conductivity enhancement of ZnO nanofluid using a one-step physical method

In the present work, an ethylene-glycol (EG) based nanofluid containing ZnO nanoparticles was prepared by a one-step physical method known as pulsed-wire evaporation (PWE). The structural properties of the ZnO nanoparticles were studied by X-ray diffraction method and high-resolution transmission electron microscopy. The thermal conductivity of the EG-based ZnO nanofluid at a higher concentration exhibited temperature-dependency due to the clustering and aggregation of nanoparticles in the fluid. Moreover, the experimentally measured value of the thermal conductivity was higher than the theoretically calculated value based on the Hamilton-Crosser model. From an analysis of the rheological behavior, it was found that all of the nanofluids showed Newtonian behavior. The viscosity increment did not show temperature-dependency, and its value increased with the ZnO volume fraction at a fixed temperature.