Experimental studies on thermal and rheological properties of Al2O3-ethylene glycol nanofluid

An experimental investigation has been carried out to study the thermal and rheological characteristics of ethylene glycol appended with Al2O3 nanoparticles. The effect of temperature, volume fraction, particle size, pH and surfactant are studied. The samples of nanofluid are prepared using two step method. The volume fraction is varied from 0.1 to 1% and pH from 2 to 11. The nanofluid has higher thermal conductivity and viscosity compared to the base fluid. The thermal conductivity can be enhanced further by adjusting the pH of the base fluid. Non-ionic surfactant PVP shows better effects than anionic surfactants like SDBS and GA. Our studies indicate that unlike other nanofluids the thermal conductivity of this nanofluid decreases as the particle size decreases below about 50 nm. In the ranges of volume fraction and temperature investigated, highest thermal conductivity ratio obtained is 1.38 (at 1% volume fraction and temperature 50°C). The corresponding viscosity ratio is 1.25. Unlike pure fluid, nanofluid shows shear thinning behaviour at low temperature and shear rates. At higher volume fractions this nanofluid has little potential for use as a coolant in comparison with the base liquid.