LAUSR

Abstract In the present work, we investigate the effect of nanoparticle crystallite size and shape on the thermal, rheological and optical properties of low-cost copper oxide nanofluid. Nanofluids are prepared by suspending 0.3% volume of nanoparticles in the 70:30 ethylene glycol:distilled water mixture using ultrasonic vibration, and followed by the microwave irradiation. Our results indicate that the zeta potential values of the nanofluids decrease as nanoparticle anisotropy or aspect ratio increases, zeta potential values decreases. Moreover, the increase in the thermal conductivity of the nanofluids is maximum for the nanofluids prepared using nanorods having the highest aspect ratio of 5.84. The rheology data of the CuO nanofluids with different shapes of nanoparticles at a particle volume fraction of 0.3% indicates that the nanofluids predominantly show Newtonian behaviour, exemplified by the shear rate independent viscosity. Moreover, the rheological behaviour is observed to depend on crystallite size and the nanoparticles shape as marked by an increase in the viscosity which follows the order, spherical