An experimental evaluation of the miscibility characteristics of ten different non-CFC refrigerants with fourteen different lubricants

Miscibility data are needed to determine the suitability of refrigerant/lubricant combinations for use in a refrigeration system. Refrigeration systems require a miscible refrigerant/lubricant mixture for proper compressor lubrication, for proper lubricant return to the compressor, and for maximum heat transfer performance in the evaporator. Thermodynamic analysis of binary mixtures provides methods for determining the miscibility characteristics of refrigerant/lubricant mixtures, but experimental solubility data (pressure-temperature-composition) must first be obtained. Therefore, miscibility data are more conveniently obtained from direct experimental evaluation as was performed in this study;A new method for rapidly obtaining refrigerant/lubricant miscibility data has been developed. The test facility, experimental procedures, and results for this new method are described. Miscibility data have been obtained for a variety of non-CFC refrigerants and their potential lubricants. Ten (10) different refrigerants and fourteen (14) different lubricants were investigated. The refrigerants include R-22, R-32, R-123, R-124, R-125, R-134, R-134a, R-142b, R-143a, and R-152a. The lubricants consist of mineral oils, alkylbenzenes, polyglycols, and polyol esters with varying viscosities. The miscibility tests were performed in a test facility consisting of a series of miniature test cells submerged in a constant temperature bath. The bath temperature can be precisely controlled over a temperature range of -50°C to 90°C (-58°F to 194°F). The test cells are constructed to allow for complete visibility of refrigerant/lubricant mixtures under all test conditions. Experiments were performed using refrigerant concentrations of 10, 20, 35, 50, 65, 80, 90, and 95%. Each of the refrigerants tested are completely miscible with at least one of the lubricants, with the exception of R-143a, which exhibits partial miscibility with each of the lubricants.