The formation of sufficiently thick lubricant films at die highly stressed contacts within a rolling bearing is a prerequisite for reliable operation. These films are a function of the lubricant's physical parameters: viscosity, η and pressure-viscosity coefficient, α. In the screw compressor bearing application, either or both parameters may be adversely affected by the presence of refrigerant. Experimental measurements of η and α are presented for oil-rich solutions of R22 and a naphthenic oil and of R134a and ester oils. These measurements, obtained with a rotating cylinder viscometer, are supported by measurements of film thickness on an optical disc test rig and of effective lubricant viscosity on a dynamic bearing test rig.
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