To be able to measure the actual film thickness in a bearing contact lubricated with oil-refrigerant mixtures, a test rig has been designed where the film thickness can be measured by optical interferometry. By calculating backward from the measured film thickness, it is possible to calculate the effective viscosity. The test rig was used to measure the effective viscosity of a polyol ester together with R134a as a function of temperature and pressure. Includes comparisons between viscosity calculated from measured film thickness and viscosity measured with an oscillating bob viscometer. The apparatus was also used for investigating the effect on film thickness of flow rate and sudden changes in pressure.

KEYWORDS: viscosity, refrigerants, oils, heat transfer fluids, mixtures, steady state, measuring, thickness, testing, interferometry, fluid flow, flow rate, pressure difference.