Tribological properties of sliding elements in refrigerant compressors lubricated by low-GWP refrigerant/oil mixtures.

In response to global regulation of high global warming potential (GWP) refrigerants, the application of lower GWP refrigerants to air conditioning equipment has been strongly accelerated. Toward the adoption of new refrigerant alternatives, evaluations of tribological properties of sliding elements in compressors are essential because the physical properties of refrigerant oil mixed with the refrigerant strongly affect the seizure resistance of the compressors. Here, we selected several refrigerants including hydrofluoroolefin (HFO) as candidates for a low-GWP refrigerant applicable to refrigerant compressors. We measured the viscosity of lubricating oil mixed with the liquid refrigerant. We also performed seizure resistance tests in refrigerant oil with low concentration in the liquid refrigerant to evaluate seizure resistance under the condition that the liquid refrigerant is returned to the compressor.