Effect of Surfactant on Stability, Thermal Conductivity, and Viscosity of Aluminium Oxide–methanol Nanofluids for Heat Transfer Applications

Nanofluids, suspension of nanoparticles, perform better in heat transfer applications due to their excellent thermal properties over conventional heat-transfer fluids. In this study, the stability of Aluminium Oxide (Al2O3) methanol nanofluids and their thermophysical properties (thermal conductivity (TC), viscosity, and density) are experimentally investigated. Various surfactants and nanoparticles were suspended into methanol and sonicated to stabilise the suspension at different weight fractions (0.05-0.15 wt%) of the nanoparticles and surfactants. The stability was analysed for the same ratios of different wt.% of nanoparticles and surfactants as a function of time. All the experiments were carried out at a temperature of 298 degrees K. Nanofluids characterisation, zeta potential and physical observations revealed 0.10 wt% of Al2O3-methanol with cationic surfactant cetyltrimethylammonium bromide (CTAB) surfactant nanofluids were stable for more than 180 days (6 months). The experimental results found that the TC, viscosity, and density of Al2O3-methanol nanofluids were all an increasing function of wt.% of nanoparticles. The addition of surfactant into the Al2O3-methanol nanofluids slightly affects the TC, viscosity, and density. The maximum enhancement of TC with surfactant was found to be 13.7% which was 1.4% lower than without surfactant of Al2O3-methanol nanofluids. However, the Al2O3-methanol nanofluids were more stable and had enhanced thermal properties such as (TC, viscosity, and density) over the base fluid. Therefore, the results encourage using these nanofluids in heat transfer applications.