Experimental investigation of Fe₃O₄ nano-oil and outdoor temperature effects on a 5-ton R22 vapor compression chiller...

Nanofluids have demonstrated significant potential to improve the efficiency of heat transfer systems, particularly in refrigeration applications. This study experimentally investigates the effects of Fe₃O₄ nanoparticles (0.15% mass fraction) dispersed in POE RL32-3MAF compressor oil on the performance of a 5-ton R22 vapor compression chiller, alongside the impact of outdoor temperature variations (33-39 °C). System parameters were monitored at four critical points in the refrigeration cycle (evaporator outlet, compressor outlet, condenser outlet, and expansion valve outlet) under both nanofluid-enhanced and base oil conditions. Key findings reveal that the nanolubricant enhances cooling capacity by 5% and improves the coefficient of performance (COP) by 2% on average, despite a marginal 3% increase in compressor power consumption. Outdoor temperature exhibited a pronounced influence, with each 2 °C rise reducing COP by approximately 10%. Furthermore, the compressor's electrical input power consistently exceeded its thermodynamic power by 10%, with the discrepancy intensifying at higher ambient temperatures. These results highlight the dual role of nanolubricants in boosting system efficiency while mitigating performance degradation under thermal load variations.