The Research Unit will tackle the issue of lacking fundamentals for oil-refrigerant multiphase flows in gaps with moving boundaries. Experts from fluid mechanics (Project Area A) and thermophysical property research (Project Area B) will team up to provide a validated calculation model for multiphase surge and gap flows of such strongly asymmetric mixtures in rotary positive displacement compressors (RPDC) for the first time. The state-of-the-art of methods for simplified simulation of these types of flow in RPDC (A1), the fundamental knowledge in the fields of optical flow measurements (A2) and high-resolution numerical gas-liquid flow simulations (A3) as well as the accurate measurement (B1, B3) and modeling (B2, B4) of thermophysical properties of strongly asymmetric mixtures will be advanced.