Thermophysical properties of TiO2-PVA/water nanofluids

Nanofluid, as an innovative cooling fluid, is a colloidal suspension with superior potential for enhancing the heat transfer performance of conventional fluids, however stability and durability are challenges for industrial applications. In attempts to investigate thermophysical properties (thermal conductivity and viscosity), many studies have been conducted, however no consensus has yet been reached. Thus, this work aims to investigate, experimentally, these properties including stability, by applying the technique of surface modification. The anatase structure of the titanium dioxide nanoparticle was synthesized by the hydrolysis of titanium isopropoxide. The surface modification of the nanoparticles was accomplished by treatment with PVA polymer (polyvinyl alcohol), with the aim of improving the stability of the nanofluids. The modified nanoparticles were used for the preparation of nanofluids with different volume percent loadings of nanoparticles in water ranging from 0.00125% to 0.1%. SEM, TEM, Raman, FTIR and XRD were used for the characterization of nanoparticles. Sedimentation photo capturing was applied to visualize the stability of the prepared nanofluids. A transient hot bridge (THB) apparatus was used for measuring the thermal conductivity of the nanofluids whereas the rotational viscometer was used to measure the viscosity of the nanofluids. Data were collected at temperatures ranging from 20 degrees C to 50 degrees C. The results showed that the measured viscosity and thermal conductivity of the nanofluids increased as the particle concentrations increased and were higher than the values of the base fluids. The results thus suggest that use of the surface modification technique has a significant effect on the stability of TiO2 nanoparticles. (C) 2017 Elsevier Ltd. All rights reserved.