Bahman Rahmatinejad - Phd student, Department of Biosystem Mechanical engineering, Bonab Branch, Islamic Azad University, Bonab, Iran.
Mahdi Abbasgholipour - Assistant Professor, Department of Biosystem Mechanical engineering, Bonab Branch, Islamic Azad University, Bonab, Iran.
Behzad Mohammadi Alasti - Assistant Professor, Department of Biosystem Mechanical engineering, Bonab Branch, Islamic Azad University, Bonab, Iran.

The thermophysical properties and thermal performance of water- and ethylene-glycol-based nanofluids containing  and CuO nanoparticles were examined. Nanofluids were prepared at four concentrations (۱- ۴ vol%) using an electric mixer and magnetic stirrer, and the thermophysical properties were measured. Surfactants were used to improve stability. The transient hot-wire method (KD۲-Pro device), Dynamic Light Scattering (DLS), and Ostwald viscometer (ASTM D۴۴۵-۰۶) were used to measure the resulting thermal conductivity coefficient, nanoparticle diameter, and nanofluid viscosity, respectively. The experiments were carried out in the ۲۰ to ۵۰ °C temperature range. Adding ۱ wt% sodium dodecyl sulfate (SDS) to the CuO–water and the same amount of sodium dodecylbenzene sulfonate (SDBS) to the –water nanofluid were found to stabilize them for ۲۰ and ۲۲ days, respectively. Increasing the nanoparticle volume fraction, raising the temperature, and reducing nanoparticle diameter were found to increase the thermal conductivity coefficient. The density also increases with the nanoparticle volume fraction in the base fluid increasing. Moreover, at the same volume fraction, the CuO–water nanofluid had a higher density than –water. Better base fluid thermal properties amplify the effect on the nanofluid's thermal conductivity coefficient. The actual thermal conductivity coefficient was determined by comparing model predictions of the coefficient.

Al۲O۳, CuO, Nanofluids, nanoparticles, Thermal conductivity coefficient