This paper discusses the choice and implementation of bearings for oil-free compressors where the system refrigerant is used as the lubricant in externally pressurised and hybrid bearings. The problems of oil contamination in heat pump applications is described followed by methods to produce genuine oil-free hermetic systems. Alternative bearing choices are described for high and low speed applications. Theoretical and experimental results are presented showing the effects of turbulence in the bearing clearance and pockets of externally pressurised thrust and journal bearings for a co-rotating scroll compressor operating with r134a. The paper concludes that design methods are now available to enable the incorporation refrigerant lubricated bearings in hermetic oil-free compressors.
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