Environmental protection and performance enhancement of hydrocarbon compressor based vapour compression refrigeration system using dry powder SiO2 nanoparticles: an experimental analysis

The present research explores the dispersion of SiO₂ nanoparticles in compressor lubricant, polyolester (POE) oil for performance enhancement of vapour compression refrigeration system (VCRS). The contribution of SiO₂ nanoparticles based nanolubricant was examined for eco-friendly hydrocarbon (HC) refrigerant R600a, retrofitted to hydrofluorocarbon (HFC) compressor based VCRS and also in HC compressor, in governing the performance of VCRS. Wear characteristics improved by the nanolubricants were assessed through pin-on-disc wear testing, using the pins extracted from the actual compressor piston used in VCRS. As compared to POE oil, the average specific wear rate (SWR) and coefficient of friction (COF) of nanolubricant were reduced by about 20% and 29%, respectively. Enhanced average viscosity and average thermal conductivity were observed (35–95 °C), with maximum increases of about 13% at 65 °C and 45% at 95 °C, respectively, in comparison to those of POE oil. Field emission scanning electron microscopy (FE-SEM) was utilized to analyze the morphology of SiO₂ nanoparticles, while Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analyzed their crystal structure. The Zeta potential tests for the prepared nanolubricant were conducted to ensure its long-term stability. An HC compressor based VCRS shows better performance including average refrigeration effect, average power consumption by compressor, and the average coefficient of performance (COP) of 29%, 7%, and 39%, respectively compared to the base lubricant filled retrofitted system. Hence the findings of the present research provide novel perspectives on the potential benefits of incorporating SiO₂ nanoparticles and an HC compressor to improve the VCRS performance.