A numerical study on the oil retention of R410A and PVE oil mixture in multi heat pump system

Predicting an amount of discharged oil from a compressor is necessary to charge the compressor with proper amount of oil. The amount of discharged oil can be predicted by calculating the oil retention amount in each component of a heat pump system. This study suggests a method for calculating the oil retention amount in a heat pump system. In addition, flow pattern of refrigerant and oil mixture in horizontal gas line of refrigerant was ascertained by flow visualization. The oil retention amounts in each component of multi heat pump system were calculated with respect to mass flux of refrigerant, Oil circulation ratio (OCR), length of horizontal and vertical lines. Oil retention amounts in horizontal and vertical gas lines of refrigerant were significant. To validate the model for gas lines of refrigerant, comparison between predicted and experimental oil retention amounts was conducted, and mean absolute percentage error was 15.0%.