Effect of SiO2 nanoparticles on the heat transfer characteristics of refrigerant and tribological behaviour of lubricant

Abstract

Scientists and researchers are enthusiastically utilizing novel technologies that can substantially reduce energy consumption in diverse thermal systems. The foremost aim of the present investigation is to exploit the potential of nanoparticles on the enhancement of heat transfer characteristics of refrigerant and tribological capabilities of lubricant. Experimental investigations on the forced convection heat transfer characteristics of R134a/SiO2 nanorefrigerant (R134a + SiO2-polyalkylene glycol nanolubricant) are carried out. The effect of particle concentration, heat flux, mass flux, and vapour quality are investigated. The friction reduction and anti-wear properties of the nanolubricant are evaluated using four-ball tribo-tester. The results reveal that the presence of nanoparticles in the refrigerant significantly enhances the heat transfer coefficient of refrigerant and the tribological behaviour of lubricant. The maximum increase in heat transfer coefficient is 163.2% corresponding to a particle concentration of 0.4%. The presence of nanoparticles in refrigerant results in a marginal increase in pressure drop. However, the penalty in pressure drop is insignificant compared to the enhancement in heat transfer. Excellent friction reduction and anti-wear performance are also manifested by the nanolubricant. The maximum reduction in the friction coefficient is 37.76% and that of wear scar diameter is 40.83%. Considering the heat transfer and tribological characteristics, the optimum value of the particle volume fraction is 0.4%. SiO2-PAG nanolubricant can be considered as a potential energy-saving alternative to refrigerant compressor oils.