Effect of Nanoparticles Size and Concentration on Thermal and Rheological Properties of AL 2 O 3 -Water Nanofluids

Abstract -An experimental study was conducted to investigate the thermal and rheological properties of various suspensions of AL 2 O 3 in deionized water. Tests were carried out using nanoparticles with average diameters of 5 and 50 nm for suspensions concentration ranging from 0 to 40% by mass. Tests reveal that alumina nanofluids thermal conductivity increases with the increase in operating temperature and in suspensions concentration, but decreases with the increase in nanoparticles diameter. Also, fluids with 5 nm particles exhibit non-Newtonian characteristics of shear thinning fluids. This behaviour intensifies as the suspensions concentration increases. However, fluids with 50 nm particles behave as shear thickening fluids. This behaviour does not seem to be altered by the increase in suspensions concentration. Tests also reveal that alumina nanofluids viscosity increases with the increase in the suspensions concentration. For fluids with 5 nm particles, viscosity is shown to increase with the increase in the operating temperature, but for fluids with 50 nm particles it is shown to decrease with the increase in temperature