Experimental investigation of free connective heat transfer augmentation using transformer oil-Al2O3 nanofluid

Abstract

There is a definite need to improve the heat transfer capability of the transformer oil as it plays a vital role in the life span of transformers. As the thermal conductivity of the transformer oil is very less compared to the conventional liquids and those liquids cannot be used as dielectric liquids as they do not possess electrical insulation properties. It is very much essential to improve the thermal conductivity of the transformer oil in any manner in order to augment the “heat transfer or thermal management performance” of the transformer oil. Dispersion of metallic or metallic oxide nanoparticles into the base fluid in a systematic way is a proven method to enhance the thermal properties for various practical heat transfer applications like forced convection, boiling, refrigeration, solar and electronic cooling. In this study, alumina nanoparticles are dispersed in transformer oil to synthesize stable, homogenous transformer oil – Al2O3 nanofluid and to investigate the free convection “coefficient of heat transfer performance” along a vertical slender cylinder submerged in the liquid. Experiments are conducted using the transformer oil - Al2O3 nanofluid at different particle loadings or fractions starting from 0.05 % to 0.6 %. It is learnt that the highest “coefficient of heat transfer performance” occurs at 0.1 Vol% among all the volume fractions. It has been acknowledged that the “coefficient of heat transfer” is got better up to 0.1 % particle loading and then decreased with additional accumulation of nanoparticles.