Experimental study on thermal and tribological performance of diamond nanolubricants applied to a refrigeration system using R32

In order to support the drop-in procedure of high global warming potential (GWP) refrigerants, this work deals with an experimental investigation of the use of nanolubricants based on polyol ester (POE) synthetic refrigeration oil containing synthetic diamond nanoparticles at two different mass fractions, 0.1% and 0.5%. The nanolubricants were tested in a vapor compression refrigeration system operating with the R32 refrigerant as substitute for R410A. The two-step method was used for the synthesis of the diamond nanolubricants, and an experimental setup was developed to study the influence of the nanolubricants on the performance of the refrigeration system. Additionally, linearly reciprocating sliding wear tests were performed in order to evaluate the performance of the diamond nanoparticles as lubricant additive under starving lubrication conditions. The addition of diamond nanoparticles with 0.1% and 0.5% mass fraction (%m/m) resulted in maximum reductions in friction and wear of similar to 4% and similar to 30%, respectively. Finally, with the use of diamond nanoparticles the coefficient of performance and the cooling capacity increased by 0.5 and 5.0%, respectively, and the discharge temperature of the compressor was slightly reduced. (C) 2020 Elsevier Ltd. All rights reserved.