Rheological characteristics and thermal studies of EG based Cu:ZnO hybrid nanofluids for enhanced heat transfer efficiency

The present work describes an experimental investigation of Cu-doped ZnO–EG hybrid nanofluids for better viscous nature and thermal efficiency in cooling systems. The initial phase involves synthesizing copper (Cu) doped zinc oxide (ZnO) nanoparticles using chemical precipitation method. The structural and morphological properties of these nanoparticles are determined using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Thermo-physical measurements are conducted to analyze the viscosity and thermal conductivity of Cu-doped ZnO nanofluids based on ethylene glycol (EG) at varying particle concentrations (ranging from 0.01 wt% to 0.08 wt%) with various temperature ranges of 298 K to 328 K. The observed rheological properties showed that the viscosity of tested Cu-doped ZnO-EG nanofluids exhibited non-Newtonian shear-thinning behavior due to the alignment of nanoparticle agglomerates with increasing shear rate. Similarly, the thermal properties of the prepared Cu:ZnO-EG nanofluids are examined, demonstrating a smooth increase in thermal conductivity with changes in particle concentration and temperature. The thermal conductivity ratio of the nanofluids suggests that the newly developed hybrid nanofluids exhibit superior heat transfer characteristics.