Miscibility and stability of synthetic lubricants with HFC refrigerants

Abstract

AbstractThe phase‐out of CFC production and further regulations on HCFC are required because of their association with the depletion of stratospheric ozone. HFCs and their mixtures have evolved as long‐term replacements for CFCs and HCFCs. For air conditioning and refrigeration systems, new synthetic lubricants having miscibility with HFC refrigerants, similar to that of mineral oils with CFCs, have been developed. Data on the miscibility ofR‐32/125 and R‐125/143a with polyol ester lubricants are presented in this paper. In the temperature range of interest (−40°C to 60°C), we observed the upper immiscible region, lower immiscible region, as well as the coalescence of the two regions, for polyol ester lubricants with these HFC refrigerant mixtures. HFC‐143a is least miscible among the three pure HFC refrigerants. The stability of R‐32/125 and R‐125/143a with dry polyol ester lubricants is very good at 204° C. With high moisture content, hydrolysis of the lubricant occurs at high temperatures. The onset of significant hydrolysis of lubricant (B) takes place between 175°C and 200°C. Care must be exercised to maintain the dryness of polyol ester lubricants and refrigeration systems to prevent this occurring.