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This paper identifies the dynamic viscosity and the thermal conductivity three nanofluids (NFs) mineral oil base ISO 32, used in domestic refrigeration compressors, additivated respectively by nanoparticles (NPs) of carbon nanotubes (NTC), niobium oxide (Nb2O5) and Indian (In). After analyzing the thermo-physical properties, investigates the stability (NFs) by specific methods and then is compared the tribological performance of the most stable sample by high frequency reciprocating rig. The results demonstrated that the dynamic viscosity has insignificant change, the thermal conductivity has significant gain with respect to the pure oil and that (NFs) of (NTC) and (In) have good and reasonable stability respectively, while the compounds additivated with (NPs) of (Nb2O5) are unstable and are not viable for use in thermal systems. The (NFs) of(NTC) when compared with the pure oil showed higher lubricant film thickness, lower coefficient of friction and lower average wear. [ABSTRACT FROM AUTHOR]

The refrigerants being used in vapor compression processes have specific thermodynamic properties, which are decisive for the performance of the compressor of the system. The Montreal and the Kyoto protocols initiated a discussion of alternative refrigerants, which lead to new requirements of the compressor. The reliability of reciprocal compressors has become a leading field for compressor research. One of the main tools in the reliability field is accelerated degradation/life testing (ADT or ALT). These tests are designed to provide life estimates or to define lower bounds of product/parts reliability at shortened time periods. The objective of this paper is to discuss the literature on accelerated life testing of reciprocating hermetic compressors, focusing on the wear of mechanical components. Several test methodologies are discussed as well as the procedures used to wear quantification. It is noted that there are numerous test methodologies. This fact can be attributed to the lack of standardization updated. Most authors have been focused the tests development to assess the scuffing occurrence in components. The evaluation of wear (qualitative and quantitative) is carried through optical microscopy techniques, scanning electron microscopy, surface roughness, physical-chemical analysis of the oil and electric power consumption. Test methodologies are presented based on critical analysis of the existing literature and the current scenario of refrigerants and lubricants development. [ABSTRACT FROM AUTHOR]