Material compatibility of HVAC&R system materials with low GWP refrigerants.

When assessing the suitability of next generation refrigerants for use with current HVAC&R system materials, two areas of concern need to be thoroughly investigated and understood: 1) compatibility of the system materials when in contact with the fluids, and 2) chemical stability of the fluids when exposed to system materials. This paper summarizes material compatibility evaluations of unsaturated hydrofluorocarbon (HFO) refrigerants, and HFO refrigerants blended with R32, that were conducted to better understand equipment reliability risks associated with the use of next generation low global warming potential (GWP) refrigerant candidates. Material compatibility exposures were conducted in Parr pressure vessels with R1234yf, R1234ze(E), and a three refrigerant composite blend of R1234yf, R1234ze(E), and R32 (33% by weight of each), with nine types of elastomers, three gaskets, five polymers, and ten different motor materials. Exposures were conducted in 100% refrigerant, 50% refrigerant:50% lubricant, and 100% lubricant to encompass the range of refrigerant and lubricant compositions that may be present in different areas of operating systems. Two different lubricants, a polyol ester (POE) and a polyvinyl ether (PVE), were evaluated in the study. In total, each of the materials was exposed to twelve different conditions. Results of laboratory measurements of the physical property changes of exposed elastomeric and polymeric materials, and hermetic compressor motor materials, are presented in this paper. In addition, potential system reliability implications of these results, based on a risk-based ranking approach, are reported.