Dew-Point Densities of Fluid Mixtures - New Approaches for Measurement and Modeling

• Applicant: Professor Dr.-Ing. Markus Richter
• Subject Area: Technical Thermodynamics
• Term: from 2015 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 269357610

The aim of the proposed research project is to develop new experimental techniques for the accurate measurement of dew-point densities of fluid mixtures, which overcome difficulties in currently existing techniques. This includes the quantification of sorption effects, thus, significantly reducing uncertainties. A new theory will be forged, which will combine, for the first time, the well-established fields of thermodynamic property measurement and sorption phenomena. Furthermore, the measured data will be used to establish multiparameter fundamental equations of state, whereby new ideas regarding the fitting strategy will be examined.The investigation of the phase behavior of fluid mixtures is a major focus of thermophysical property research. To make the outcome of this research applicable for science and industry, for example in the fields of natural gas processing and carbon capture and storage, property models accurately describing the phase boundary between liquid and vapor are required. The most important prerequisite for the development of such models are accurate experimental data, however, there are gaps and deficiencies in the presently existing data sets. For the development of equations of state, which are able to describe the phase equilibrium of mixtures, mainly VLE (vapor-liquid equilibrium) data are used. Nevertheless, only very few VLE data consider the saturated liquid and saturated vapor densities. But it is exactly these kinds of data that provide complete experimental information on the VLE state, which would be absolutely required to advance the state of the art of the existing equations of state.Accurate saturated liquid densities of fluid mixtures were measured at NIST in the 1980s, and at Ruhr-University a new and highly accurate experimental apparatus is available by now specifically designed to measure this type of data. In contrast, accurate data for fluid mixture dew-point densities virtually never exist.Experimental approaches to measure the full set of VLE properties of fluid mixtures including the saturated liquid and saturated vapor densities are very scarce. The most significant source of uncertainty of so-called analytic measurement approaches is sampling the phases for composition analysis because substantial problems occur (e.g., changing the composition and disturbing the equilibrium). Additionally, the density measurement techniques are not sufficiently accurate for gaseous states. Hence, a synthetic approach, which means the composition of the sample is accurately known, in combination with an accurate density measurement technique is required. In this context, recent studies have shown that exactly knowing the composition is not sufficient when sorption effects and capillary condensation are not considered. These disturbing effects distort the measured density and, therefore, they need to be understood and taken into account.

• DFG Programme: Independent Junior Research Groups
• Major Instrumentation: Magnetic Suspension Balance
• Instrumentation Group: 8930 Spezielle Waagen (ferngesteuert, registrierend)