Using Density to Calculate the Oil Circulation Ratio of a PAG Oil in R134a

Automotive air-conditioning systems employ a refrigerant as the working fluid; however, a portion of oil is discharged from the compressor as part of the compression process and also circulates through the system. This small amount of parasitic fluid needs to be determined for proper design of heat exchange equipment and connection piping. It is desired to be able to measure the small concentrations of oil circulating as a component of the working fluid online in real time. The oil in circulation as a fraction of the total fluid flow rate is termed the oil circulation rate or oil circulation ratio (OCR). A method for determining the OCR online with a coriolis type density meter is discussed.