Effect of surface modification on the thermophysical properties of ethylene glycol dispersed with Al₂O₃ nanoparticles for solar thermal applications

This study focuses on investigating the effects of surface modification on the stability and thermal conductivity of ethylene glycol dispersed with aluminium oxide (Al 2 O 3 ) nanoparticles. Aluminium oxide (Al 2 O 3 ) nanoparticles were dispersed in ethylene glycol after surface modification with the surfactant Cetrimonium bromide (CTAB) at concentrations of 1, 0.5, 0.25 and 0.125 mass percent. The thermal conductivity and dynamic viscosity at various concentrations were evaluated in the temperature range from 20°C to 170°C, in contrast to prior studies in which the properties were determined in the range from 20°C to 60°C. The stability of the suspension dispersed with CTAB proved to be excellent, and the nanofluids remained stable for one month due to its excellent electrostatic interaction with the surface of Al 2 O 3 nanoparticles. The addition of Al 2 O 3 nanoparticles to ethylene glycol led to a significant improvement in thermal conductivity, which is between 15% and 25%. The influence of the surfactant is clear from the results, and it shows that CTAB is the most suitable surfactant for metal oxide nanoparticles. The experimental data are compared with the data available in the literature in the temperature range from 30°C to 60°C and are found to be in good agreement.