Thermal conductivity analysis of Al2O3/water-ethylene glycol nanofluid by using factorial design of experiments in a natural convection heat transfer apparatus

Abstract

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.