Dew Density of Fluid Mixtures – Linking Experiment and Molecular Simulation (DFG research grant)

The aim of the research project is to precisely determine the dew points of fluid mixtures. Since precision density measurements near the dew point are affected by sorption effects and capillary condensation, a methodology is being developed that combines highly accurate gravimetric density measurements with molecular dynamics simulations (MDS).

This methodology will contribute to a complete and accurate description of the dew line of mixtures (including pressure, temperature, composition, and density) with unprecedented quality. Based on this, the state of the art of existing equations of state that can describe the phase equilibrium of mixtures can be advanced.

Precise knowledge of the phase behavior of mixtures is of fundamental importance for many scientific and technical tasks, e.g., in the field of natural gas transport and CO2 capture and utilization. This is why corresponding equations of state are needed, the development of which is based primarily on accurate experimental vapor-liquid equilibrium (VLE) data. However, these data rarely include boiling and dew densities, even though it is precisely these densities that are needed to fully describe the phase equilibrium. While accurate measurements of the boiling density of fluid mixtures are possible, disruptive surface phenomena (adsorption and capillary condensation) must be understood and taken into account when accurately measuring dew densities. For this reason, the applicant's Emmy Noether Group developed and established a corresponding gravimetric precision density measurement technique.

Despite this measurement technique, it is not possible to measure dew density directly, and even the most accurate measurements currently available do not provide precise information about the location of the “true” dew point. MDS can provide a better understanding at the atomic level and thus make a significant contribution to the interpretation of the measurement results. In addition, MDS is expected to assist in the development of correction models for density measurement near the dew line.