Effective thermal conductivities and viscosities of water-based nanofluids containing Al2O3 with low concentration

We experimentally investigated effective thermal conductivities and viscosities of water-based nanofluids containing Al
₂
O
₃
(Al
₂
O
₃
-nanofluids) with low concentration from vol. 0.01% to 0.3%. Without surfactant, Al
₂
O
₃
-nanofluids are manufactured by two-step method which is widely used. To examine suspension and dispersion characteristics of Al
₂
O
₃
-nanofluids, zeta potential as well as transmission electron micrograph of Al
₂
O
₃
nanoparticles is observed. The effective viscosities of Al
₂
O
₃
-nanofluids according to the temperature are measured by a viscometer of oscillating type. The transient hot wire method is used in this study to measure the effective thermal conductivities of Al
₂
O
₃
-nanofluids. Based on the results the maximum increase of effective viscosities of Al
₂
O
₃
-nanofluids is up to 2.9% while the maximum enhancement of effective thermal conductivities is up to 1.44%.