Stability and thermophysical measurements of TiO2 (anatase) nanofluids with different surfactants

In the present work, TiO2 (anatase) water-based nanofluids have been synthesized and the effects of temperature (20-60 °C) and solid volume fraction (0.1%-1.0%) on its thermophysical properties (thermal conductivity, viscosity, and surface tension) have been investigated. Various surfactants such as CTAB, SDS, SDBS and acetic acid have been tried to stabilize the nanofluids, when CTAB and SDS are found to provide stable suspensions. Transmission electronic microscopy (TEM), dynamic light scattering (DLS), and zeta potential techniques have been used to characterize the particle size, distribution and stability of the nanofluids, respectively. The experimental results quantify the increment in thermal conductivity of the nanofluid samples with the increase in particle volume fraction and rise of temperature. The maximum enhancement in thermal conductivity, 5.8% over that of the base fluid, is observed for the SDS-surfacted nanofluid at 1% volume fraction and temperature of 60 °C. Nanofluid viscosity has also been measured for the entire range of solid volume fraction and temperature, when it is found to increase with solid volume fraction and decrease with temperature. Surface tension of the nanofluids decreases with the increase in solid volume fraction and temperature.