Comparison of Thermo-Physical and Tribological Characteristics of Nanolubricant

This paper presents the comparison of characterization and investigation on viscosity, thermal conductivity and friction coefficient of Silicon carbide (Sic), Silicon nitride (Si₃N₄) and Magnesium oxide (MgO) nanolubricants for refrigeration applications. The characterization of nanoparticles was done by SEM, XRD and EDS tests. Nanopolyolester oil samples were prepared by two-step method for different volume concentrations of 0.15, 0.3, 0.45 and 0.6%. Viscosity of the nanolubricants was measured for different volume concentration and at various temperatures. The experimental results found that the viscosity and thermal conductivity of the Si₃N₄ nanolubricant is higher than the other nanolubricants. Also it is found that the coefficient of friction of Si₃N₄ nano lubricant is lower than the other nanolubricants. The viscosity of the Si₃N₄ nanolubricant has been enhanced by 41.6, 33.9, 31.2, and 37.1% at 0.6% volume concentration for 20, 30, 40, and 50 °C with respect to polyolester (POE) oil. The result displayed that the thermal conductivity of Si₃N₄ nanolubricant was enhanced by 42.4, 46, 45.6, & 41.4% corresponding to 0.15, 0.3, 0.45 and 0.6% volume concentration with respect to pure POE oil. This paper also emphasis on the comparison of tribological behavior of the nanolubricant and pure POE oil. It is found that the coefficient of friction was reduced by 1.3 times lower at optimal concentration of 0.6%. These conclusions suggest that Si₃N₄ nanoparticle as additives in the base POE oil can improve the lubrication and thermal properties of base lubricant and can be used for the refrigeration application.