Elastohydrodynamic lubrication and lubricant rheology in refrigeration compressors

Sammanfattning: The introductory chapter gives a general description of the lubrication of rolling element bearings in refrigeration compressors and rheological properties of oil-refrigerant mixtures. The influence of refrigerants on the viscosity, pressure-viscosity coefficient and film forming ability in a EHD-contact is described. A method is described for measuring the viscosity of oil-refrigerant mixtures measured using optical interferometry film thickness. The effect of pressured natural gas on the viscosity of polyalkyleneglycols was measured ar pressures up to 10 MPa. Viscosity and pressure-viscosity coefficient was measured on different polyolesters mixed with refrigerant R- 134a. Optical film thickness measurements was used to compare film forming ability of polyolesters with different structure. Lubrication limits and wear of rolling element bearings operating in a refrigerant atmosphere was studied. A new method of supplying lubricants to refrigeration compressor using controlled superheat of the lubricant mixture is suggested.