Synthesis, characterization, and performance evaluation of Al2O3 nanoparticles in HFE7000 refrigerant for domestic refrigeration

Nanorefrigerants, which consist of base refrigerant enhanced with nanoscale particles, represent a promising advancement in thermal management systems. This study reports the successful synthesis, characterization, and experimental evaluation of a novel Al 2 O 3 /HFE-7000 nanorefrigerant intended for domestic refrigeration applications. Aluminum oxide (Al 2 O 3 ) nanoparticles were synthesised via a citrate sol-gel method, followed by calcination at 800 °C, and characterised using Powder X-ray Diffraction (PXRD), Field Emission Scanning (FESEM), High Resolution Transmission Electron Microscopy (HRTEM), Energy-Dispersive X-ray Spectroscopy (EDX), and Brunauer-Emmett-Teller (BET) analyses. The nanoparticles exhibited high crystallinity, spherical morphology, an average size of ∼22.5 nm, and a surface area of 26.2 m 2 /g with mesoporous structure. The nanorefrigerant was prepared by dispersing Al 2 O 3 nanoparticles in HFE-7000 using ultra sonication and magnetic stirring, aided by Tween-80 surfactant to ensure long-term dispersion stability. Five different nanoparticle concentrations (0.02%–1.5% wt) were tested. A custom-engineered vapour compression refrigeration system (VCRS) test rig was deployed to evaluate the thermophysical performance across five temperature conditions. Key findings revealed that the addition of Al 2 O 3 significantly enhanced the Coefficient of Performance (COP), improved subcooling, and reduced the discharge pressure and compression ratio—without compromising system stability. The optimal concentration range was identified as 1.2–1.4 wt%, beyond which increases in viscosity and potential nanoparticle agglomeration could offset thermal benefits. These results highlight the potential of Al 2 O 3 /HFE-7000 nanorefrigerants as high-efficiency, environmentally friendly alternatives for domestic cooling applications.