Nanolubricants in refrigeration systems: a state-of-the-art review and latest developments

摘要

Nanolubricants, dispersions of nanometer-scale particles in a conventional lubricant, have been one of the main subjects of recent studies aimed at increasing energy efficiency and durability of refrigeration systems. This work presents a state-of-the-art review of nanolubricants applied to refrigeration systems. Papers found in the literature were classified by the nature of the nanoparticle, namely: metals, metallic and non-metallic oxides, carbon allotropes and composites. Major mechanisms involved in the intensification of energy parameters are discussed. They are mainly related to heat transfer enhancement and to reduction of the system energy consumption. The former is due to the improvement of the thermophysical properties of the refrigerant/nanolubricant mixture, and the latter, to better tribological properties as a result of nanoparticles, acting as a lubricant additive. The experimental data collected from the literature showed a great dispersion of results, even though a tendency to improve the performance of refrigeration systems was observed. Likewise, the most challenging efforts toward the sustainable use of nanolubricants in these systems are also discussed.