Experimental investigation on the correlation between nano-fluid characteristics and thermal properties of Al2O3 nano-particles dispersed in ethylene glycol–water mixture

• Published in: International journal of heat and mass transfer Vol. 94; pp. 262 - 268
• Main Authors: Xu, Jinghai, Bandyopadhyay, Krisanu, Jung, Dohoy
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.03.2016
• Subjects: Al2O3 nano-particle; Ethylene glycol–water mixture; Nano-fluids; Thermal properties; Zeta potential; Thermal properties; Al2O3 nano-particle; Nano-fluids; Ethylene glycol–water mixture; Zeta potential
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2015.11.056

•Multiple correlations between nano-fluid characteristics and thermal properties.•Nano-fluid benefit was maximized through the proper nano-fluid preparation.•Al2O3 nanoparticle showed a high thermal conductivity enhancement in ethylene glycol–distilled water mixture. This paper presents a multi-parameter investigation of Al2O3 nano-particles dispersed in distilled water, ethylene glycol and ethylene glycol–distilled water mixture (50/50vol.%). The nano-fluid samples were prepared with ultrasonic processing with particle concentration up to 9wt.%. Samples were characterized by transmission electron microscope imaging, particle surface charge (zeta potential), particle aggregate size, light absorbance and pH. The thermal conductivity and viscosity of the nano-fluid samples were measured. 10.9% enhancement in thermal conductivity was observed in ethylene glycol–distilled water mixture based nano-fluid with 5wt.% Al2O3 nano-particle loading. The results show multiple-perspective correlations between nano-fluid characteristics and thermal properties. The findings are summarized as follows. Combined effect of base fluid viscosity and particle surface charge determines the degree of nano-particle aggregation. Higher enhancement in thermal conductivity is observed with moderate particle aggregation, while either light or heavy aggregation lowers the enhancement. The ethylene glycol–water mixture based nano-fluids show overall higher thermal conductivity enhancement than the distilled water and ethylene glycol based nano-fluids. The degradation of nano-fluid thermal conductivity enhancement over time is found to be related to the gravity-driven particle sedimentation. Nano-fluids containing larger particle aggregates show higher viscosity augmentation. However, the extent of viscosity augmentation is not proportional to the extent of particle aggregation.