Evaluation of Lubricant Properties and Refrigerant Interaction

Lubricant selection for compressors used in the HVAC&R industry is typically tied to the refrigerant and subsequent properties understood to be desirable for effective system operation. Over the years refrigerants have changed, and with each change there has been a need for the reevaluation of the interaction with lubricants. In some cases, the existing lubricants can be utilized, however, in others, a there has been the need for new lubricants to be developed. Unfortunately, engineers have typically not challenged what constitutes good and have proceeded with outdated values for “good” or “desirable” properties of the lubricant-refrigerant mixture. Or, in some cases, the values have been tightened, not because the system or the industry required it, but rather because the refrigerants with their lubricants have become so “good” that there was not a way to distinguish between offerings. To differentiate products, engineers increased the severity of the tests and tightened the test result specification and that resulted in breaking what is the necessary properties for design. With the introduction of the lower GWP, unsaturated hydrofluorocarbon products (HFOs), hydrocarbons and CO2, the opportunity exists to assess potential changes to lubricant chemistries that still allow for acceptable use in air conditioning and refrigeration applications to offset the inherent instability of the refrigerant molecules, so we must return to an evaluation of what does the system require for durable, efficient operation. This paper will look at what current parameters are valued for a refrigeration lubricant, how these parameters are measured and why they are important. A focus will be put on looking at what is needed to be successful with next generation low GWP refrigerants and some examples of lubricant candidates for various low GWP refrigerants. Studies will be shown that investigate how we make evaluations and how some of the current approaches need to be revisited

Compatibility of R1234yf and R134a and Lubricants used in Automotive Compressors

Understanding the compatibility of system materials with R1234yf, R1234zeE and R134a is critical to long term operation of air conditioning and refrigeration systems. Today\u27s regulatory climate of reporting and eliminating system leaks leaves very little margin of error when approving elastomeric materials to seal internal and external connections over the lifetime of the system. Thermoplastics and polymeric O-ring materials have been tested in accelerated conditions to determine volume change, strength change, extraction of plasticizers or dyes, and compatibility of the lubricant and refrigerant. Results and conclusions are presented in graphical and tabular format along with conclusions on polymeric types are suited continued development as long term system sealing and functional life

Carbon Dioxide-Lubricant Two-Phase Flow Patterns in Small Horizontal Wetted Wall Channels: The Effects of Refrigerant/lubricant Thermophysical Properties

163 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2009.This research developed measurement capabilities for measuring the solubility, miscibility, liquid density, liquid viscosity, and interfacial tension of lubricant-refrigerant mixtures. For the first time, interfacial tension measurements for refrigerant-lubricant mixtures over the range of concentrations from neat lubricant to pure refrigerant have been measured and published. The research has also lead to the development of a new prediction and modeling method for liquid viscosity and extends the historic lubricant only mixing rules to systems of lubricants with dissolved liquefied gases. A high-speed, high-pressure (< 100 bar, 1500 psia) video system has been constructed to capture the two-phase flow patterns of CO2 flows near the critical point with and without coexisting lubricant inside 0.5 mm tubes. A new flow map based on the thermophysical properties of the flowing fluid has been developed to account for the viscous and interfacial tensions effects on two-phase flows in channels below the criteria for interfacial tension affected flows.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

Carbon Dioxide-Lubricant Two-Phase Flow Patterns in Small Horizontal Wetted Wall Channels: The Effects of Refrigerant/lubricant Thermophysical Properties

163 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2009.This research developed measurement capabilities for measuring the solubility, miscibility, liquid density, liquid viscosity, and interfacial tension of lubricant-refrigerant mixtures. For the first time, interfacial tension measurements for refrigerant-lubricant mixtures over the range of concentrations from neat lubricant to pure refrigerant have been measured and published. The research has also lead to the development of a new prediction and modeling method for liquid viscosity and extends the historic lubricant only mixing rules to systems of lubricants with dissolved liquefied gases. A high-speed, high-pressure (< 100 bar, 1500 psia) video system has been constructed to capture the two-phase flow patterns of CO2 flows near the critical point with and without coexisting lubricant inside 0.5 mm tubes. A new flow map based on the thermophysical properties of the flowing fluid has been developed to account for the viscous and interfacial tensions effects on two-phase flows in channels below the criteria for interfacial tension affected flows.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD