Thermal conductivity of a heat transfer fluid plays a significant role in
improving the heat transfer performance of a heat exchanger. In this work,
experiments were performed in a natural convection heat transfer apparatus
by mixing homogenized Al2O3 nanoparticles in a base fluid of water-ethylene
glycol mixtures. The effects of heat input, nanoparticle volume content in
the base fluid, and ethylene-glycol volume content in the base fluid on
thermal conductivity of the nanofluid were analyzed. Based on results
obtained by MINITAB? design software (factorial design matrix), 16
experimental runs were performed with the lower and higher levels of input
factors. The levels for heat input were 10 and 100 W; for nanoparticle
volume content in the base fluid 0.1 and 1 vol.% and for the base fluid
composition 30 and 50 vol.% of ethylene glycol in water. From the obtained
experimental results, a Pareto chart, normal probability plot, contour plot
and surface plot were drawn. Based on the results, a new correlation was
proposed, and predictions were compared with the experimental results. From
the study, the maximum thermal conductivity value 0.49 W m-1 K-1 was
observed at a nanoparticle volume content in the base fluid of 1.0 vol.%,
ethylene glycol volume content in the base fluid of 30 vol.% and heat input
of 100 W.