Lubricity evaluation of oil–refrigerant mixtures with R134a and R290

•We proposed new method of lubricity evaluation of oil–refrigerant mixtures.•We used block-on-ring tester with linear contact under semi-submerged conditions.•Lubricity of different oil–refrigerant mixtures were evaluated.•We investigated POE/R134a and MO/R290 mixtures (three different oils for each group).•Significant differences of lubricity of substitute oils were shown.

The article presents an assessment method of lubricity properties of oils for refrigeration compressors in a mixture with a refrigerant. The assessment has been based on sample wear volume in the block-on-ring node under the conditions similar to the operation of the compressor following an extensive standstill.The authors assessed the lubricity properties of the following mixtures POE/R134a and MO/R290 (three different oils for each group).In all the analyzed cases it was found that the sample wear after the tests in the oil–refrigerant mixture is significantly (2–32 times) higher than for the oil itself. The test results also showed significant differences in the lubricity properties of oils, which are substitutes in operating conditions. Therefore, the only valid method of assessing lubricity properties of oils for refrigerating compressors are studies on the mixtures of these oils with a refrigerant in the conditions similar to the real operation.