lubricant, oil, R-1234ze(E), efficiency, R-32
This paper will highlight case studies of physical and chemical interactions between refrigerants, lubricants, and components in HVACR systems from recent evaluations of new low GWP refrigerants, and will emphasize the value of including lubricants as an integral component of technology and product development roadmaps. Refrigerant/lubricant mixture properties, such as miscibility, solubility, and viscosity, are critical to understand to meet design, operation, and reliability goals of HVACR equipment. In this paper, we will discuss miscibility and solubility challenges of specific new refrigerants, and review how these challenges have been addressed using advanced capabilities and deep understanding. Working viscosity is one of the most important factors to understand for optimal compressor efficiency and reliability, and is typically determined through Pressure/Viscosity/Temperature (PVT) measurements and corresponding models. We will compare working viscosities of current and new refrigerants, and discuss other factors to consider when defining lubrication requirements for alternative refrigerants. Relative to incumbent refrigerants, some of the new low GWP refrigerants will have fundamental differences in their chemical stability, or will be exposed to more demanding application conditions such as higher discharge temperature - both of which may contribute to reliablity concerns. We will review some of these considerations and provide examples of lubricant selection and formulation approaches to mitigate potential reliability issues. This paper will highlight examples of physical and chemical interactions that should be considered early in the development of product applications for new low GWP refrigerants, and will illustrate the benefits that optimized lubricants may have on the performance, efficiency, and reliability of equipment.