Análise termo-reológica de nanolubrificantes para compressores de refrigeração aditivados com nanotubos de carbono

Abstract

Nanofluids (Nfs) are made by adding a small volume of nanoparticles (NPs) to conventional fluids which have applications in different segments of engineering. In this work, we have done an experimental analysis of the rheological and tribological behavior of (NFs) carbon nanotube with multiple walls (NTCPM) in lubricating oils used in hermetic compressors of commercial refrigeration. Initially, the study was carried out in mineral oils type ISO 68, and later the base fluid used was the poliolester synthetic oil (POE). The undertaken analysis to the POE oil was divided into two steps: firstly the goal was to choose the most effective rheologically volume fraction. Thus, four samples of NFs in fraction of 0.3, 0.4, 0.5 and 0.6 g/l were prepared, through the processes of sonication and stirring rotation, during 24 hours at every step. When comparing the performance of each sample with the POE pure oil, the sample with 0.4 g/l of NTCPM has shown to have a better thermodynamic performance, and after being tested in high frequency lubricity bench, it showed better tribological results than the conventional lubricant. After defining the volume fraction, new extra seven samples of the NF in study were prepared. At this time we have changed only their sonication time, although the same period of time, which was previously used for the stirring rotating process has been kept. The mechanical stability of the seven samples was analyzed over a period of 90 days, through the Particle Sizing and Zeta potential tests, which indicated a sonication time influence on mechanical stability of nanolubricating. It also showed that the best track time to develop this process is between 14 and 17 hours.