A TRIBOLOGICAL STUDY OF REFRIGERATION OILS UNDER HFC-134A ENVIRONMENT

HFC-134a is a potential alternative material for CFC-12, which deplete s the ozone layer. However, problems arise when used together with con ventional refrigeration oils due to the extreme polarities of HFC-134a . FAG (polyalkylene glycol) and esters are tested with HFC-134a. This investigation enhances the testing method by taking the compressor's e nvironment into account. Miscibility and material compatibility are pr oved with sealed glass tests. A testing environment charged with refri gerant gas more closely simulates the conditions of a compressor. The conventional refrigeration oils (mineral oils, alkylbenzene, PAO (poly alpha olefin)) tested here are immiscible with HFC-134a. However the F AG and ester oils are miscible with HFC-134a. The friction coefficient of the PAG/HFC-134a system is similar to that of the mineral oil/CFC- 12 system at operating conditions. Ester oils are preferable at the st art and stop condition in the lubricity aspect. FAG shows good lubrici ty in conditions of extreme contact pressure. Consequently, this test provides reliable results on compressor lubricity and material compati bility of refrigeration oils with HFC-134a. It suggests a methodologic al way for the proper selection of refrigeration oils that may improve the durability and performance of a compressor. (C) 1998 Elsevier Sci ence Ltd.