Observation of Circulation of Immiscible Mineral Lubricant Oil in an Air-Conditioning Machine Charged with HFC Refrigerant

By installing HFC134a on the air-conditioning machine designed for HCFC22, it was proved that a more efficient heat pump system could be operated without changing mineral lubricant oil. The circulation mechanism of mineral oil with HFC134a was investigated in comparison with that of HCFC22. It was shown by the flow visualization that the mineral oil was not solved in condensed HFC134a, but droplets of mineral oil were transported with condensed HFC134a at the outlet of condenser. The circulation of mineral oil with HFC134a was also confirmed by extracting the working fluid from the tubing of the air-conditioning machine under operation.