Oil-injected rotary type positive displacement compressors (RPDC) like twin-screw machines are mainly used for the compression of refrigerants in HVAC (Heating, Ventilation and Air Conditioning) systems. The efficiency of such machines is largely determined by the inevitable two-phase surge and gap flows in these types of compressors. Therefore, it is all the more remarkable that the calculation of these flows is still a challenge today. This is due to both the complexity of simulating the two-phase flow in the narrow gaps with moving boundaries as well as the lack of accurate models for the thermophysical properties of the highly asymmetric fluid mixtures of oil and refrigerant. Against this background, the proposed Research Unit provides a unique opportunity for coordinated, interdisciplinary efforts to address this knowledge gap, with seven project partners complementing each other’s capabilities. The three subprojects of group A deal with the development of new analysis and calculation methods for the two-phase gap flows while the four subprojects of group B cover the determination and modeling of the thermophysical properties of the oil-refrigerant mixtures.
Within this consortium, subproject B2 is concerned with the modeling of the phase behavior of oil-refrigerant mixtures and will investigate existing and develop new modeling approaches for strongly asymmetric mixtures. The aim is to provide a model that on the one hand is capable of describing the best available measurements within the experimental uncertainty and on the other hand can be flexibly and readily extended, if a model for an oil or a refrigerant is required, for which no multiparameter (reference) equation of state (EOS) is available. Within the Research Unit, this Subproject is closely linked to the other Subprojects as further detailed in the work program. Subprojects A1 (Brümmer), A3 (Schröder), B3 (Fröba), and B4 (Thol) need the thermophysical property models that will be developed in this Subproject as input to their own models and experimental works. Subproject B1 (Richter) will provide the experimental vapor-liquid equilibria (VLE) and solubility data as well as experimental densities, which will be needed for the development and validation of the models developed in this Subproject. Subproject A2 (Kriegseis) will provide data for validation of the developed models.