Performance evaluation of a domestic vapor compression refrigeration system using periwinkle-shell-derived CaO-rich nano-lubricant in mineral oil

This study presents a novel approach to improving the performance of domestic vapor compression refrigeration systems (VCRS) through a bio-synthesized nano-lubricant derived from periwinkle shells, a biodegradable waste material. Periwinkle-shell-derived CaO-rich nanoparticles (PSD–CaO nanoparticles) were synthesized via a sustainable method Al2(SO4)3 as a precursor, marking the first application of PSD–CaO nanoparticles in refrigeration. Although bulk composition shows significant SiO2 inherited from the shell matrix, the active nanomaterial consists of crystalline CaO domains responsible for the observed performance enhancement. Experimental evaluation showed that at 0.1 M concentration, the 0.036 wt.% CaO-rich nanoparticle + mineral oil (M.O.) blend achieved the lowest energy consumption (0.3832 kWh) and power consumption, attributed to enhanced thermal conductivity and reduced friction. Conversely, pure M.O. outperformed nano-lubricant blends at 0.3 M concentration, where nanoparticle agglomeration increased viscosity and reduced lubrication efficiency. At 0.1 M, the 0.06 wt.% CaO-rich nanoparticle + M.O. achieved the lowest pressure ratio, indicating optimal lubrication. Cooling capacity was highest at 0.05 wt.% CaO-rich nanoparticle + M.O. (0.3 M) and 0.08 wt.% CaO-rich nanoparticle + M.O. (0.1 M). The coefficient of performance (COP) peaked at 0.05 wt.% (0.3 M) and 0.024 wt.% (0.1 M), underscoring the importance of nanoparticle dispersion in maximizing thermal efficiency. However, none of the tested configurations met the ISO requirement for pull-down to –12 °C, highlighting limitations in deep cooling capability. The key novelty lies in the eco-friendly synthesis of CaO-rich nanoparticles from waste periwinkle shells, demonstrating a pathway toward waste valorization and energy efficiency. Aligned with Sustainable Development Goals (SDGs) 11.6 and 13.3, this research shows the potential of bio-derived nano-lubricants to enhance VCRS performance, with optimal nanoparticle concentration being central to sustainable refrigeration design.