This paper presents an experimental study and a model for the oil retention and flow pattern of an R32/PVE 68 mixture in compressor suction lines. The test conditions involved a saturation temperature of 7.5 ℃ and a superheat degree of 12 ℃. The refrigerant mass flux and nominal oil mass fraction (OMFno) were varied within the ranges of 90–230 kg/(m2·s) and 0%–5%

respectively. The test samples were two smooth copper pipes with horizontal and vertical flow orientations with an inner diameter of 10.7 mm. A high-speed camera was used to record the flow pattern. The results showed that when the mass flux was from 90 to 120 kg/(m2·s) and the flow pattern was a stratified wavy flow

the amount of oil retention decreased with an increase in mass flux; in other cases

the amount of oil retention increased with an increase in mass flux. When the oil mass fraction was 1% and the mass flux reached 160 kg/(m2·s)

the flow pattern changed to a wavy annular flow and gradually developed into an annular flow. The double-circle model based on the flow pattern was used to predict the oil retention in the suction line. The results showed a mean absolute deviation of 9.35%

and 87.83% of the data were within ±20% error. To further verify the applicability of the model

291 data points were collected from five open literature

achieving a mean absolute deviation of 12.90% and a maximum absolute deviation of 65.77%

which proves that the model can accurately predict the oil retention in the suction line.