Patent ID: 8322149

Claim:
A method for selecting a refrigerant and lubricant for a vapor-compression refrigeration device system comprising: a. determining a lower operating temperature range of a vapor-compression refrigeration device; b. determining an upper operating temperature range of the vapor-compression refrigeration device; and c. selecting a refrigerant comprising at least one C 2 to C 5 fluoroalkene at a first concentration and selecting a lubricant comprising at least one polyol ester, polyalkylene glycol, or polyalkylene glycol ester at a second concentration to produce a fluid system having a refrigerant-rich phase and a lubricant-rich phase at a first temperature within said lower operating temperature range and at a second temperature within said upper operating temperature range provided that said second temperature is higher than said first temperature, wherein the refrigerant-rich phase is denser relative to the lubricant-rich phase at said first temperature and wherein the lubricant-rich phase is denser relative to the refrigerant-rich phase at said second temperature, provided that the relative difference in densities between the two phases is less than 20% at said first temperature and less than 20% at said second temperature.