Coordination Funds

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The main objective of the Research Unit FOR 5595 is to develop a valid calculation model for multiphase surge and gap flows for oil-refrigerant mixtures in rotary positive displacement compressors (RPDC) based on novel microscopic and macroscopic approaches for experiments and simulations. A crucial prerequisite for this model development is the knowledge of the occurring flow patterns (e.g., bubbly, surge, mist flow), which depend significantly on the thermophysical properties of the fluid mixtures and operating boundary conditions. The small gap heights (< 0.3 mm) in connection with moving gap boundaries make a combined experimental and numerical flow analysis necessary. On the generic experimental model of a rotating body in a cylindrical glass housing, a new laser-optical framework for the spatially and temporally resolved measurement of the two-phase surge and gap flow is tested and compared with high-resolution flow simulations. Based on this, a calculation model for multiphase flow in narrow gaps with moving boundaries is developed. The oil-refrigerant mixtures used exhibit a strongly asymmetric mixing behavior. For such mixtures, the relevant thermophysical properties are measured systematically and accurately for the first time and are transferred into precise equations of state and transport property models. The structure of the models is designed to be transferable to other strongly asymmetric mixtures. Moreover, in order to apply the models in flow simulation, attention is paid to acceptable computational speed. The new models for the thermophysical properties of the fluid mixtures together with the new calculation approaches for the multiphase surge and gap flows will enable an improved design of efficient RPDC for oil-refrigerant mixtures in the future and, thus, contribute to the reduction of the consumption of resources.