Refrigerants, Lubricants, Low GWP, Miscibility, Performance
Refrigerants used in various air conditioning and refrigeration industries are going through changes today and continued changes into the near future. These changes are being driven by environmental and energy efficiency regulations and could result in the use of refrigerants that require the investigation of new lubricants. One such change is the use of refrigerants that carry a lower global warming potential (GWP) value then current refrigerants used in the market. Some of these refrigerants present certain challenges over current refrigerants such as changes in flammability requirements, higher pressures or stability of the refrigerant in system operation. These refrigerants and the changes they represent may require different lubricants in order to maintain system optimization ensuring that energy efficiency and reliable requirements are met. The interaction between the refrigerant and the lubricant in any air conditioning or refrigeration system is a vital piece of information that is required to make certain optimal performance is achieved. The lubricant in a system is crucial to operation and needs to adequately lubricate the moving components in a system and return to the compressor when circulated. These conditions can drastically be affected by the refrigerant and lubricant interaction with improper choices resulting in consequences from lowering the overall performance to complete failure. This paper will look at some of the current and proposed low GWP refrigerants and their interaction with various lubricants. Evaluations will be made and certain properties will be presented that are essential to system operation. Of particular interest will be the refrigerant solubility factor of low GWP refrigerant candidates that can affect system performance and reliability; the stability of newer low GWP refrigerant candidates that maintain comparable current refrigerant system requirements; the miscibility of low GWP refrigerants with lubricants that can affect oil circulation; and how chemistry changes to various lubricants can help increase energy efficiency in systems operated with low GWP refrigerants. The information in this paper and the presentation will be a timely look at current and future needs for lubricants for various refrigerants that will help manufacturers in the air conditioning and refrigerant industry to evaluate the choices that need to be made in order to maintain the required system performance.