Improved semi-empirical correlations for the evaporation and condensation of zeotropic mixtures

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The aim of this project is to develop improved model approaches for the prediction of heat transfer during the evaporation and condensation of fluid mixtures. To this end, rapid test apparatuses were designed and set up in an ongoing project, with which mixture-specific parameters can be provided for the proposed calculation equations. In the applied follow-up project, the procedure is to be deepened by means of further fluid mixtures in the rapid test apparatuses and the model approaches are thus to be further developed. The rapid test apparatuses at both locations are based on the same experimental concept. The investigations on the boiling behavior of zeotropic mixtures are carried out at the Chair of Technical Thermodynamics and Transport Processes of the University of Bayreuth (Brüggemann working group), the investigations on the condensation behavior at the Institute of Thermodynamics of the Leibniz University of Hannover (Kabelac working group). Extensions of the model approaches from currently binary fluid mixtures to ternary mixtures are planned as well as constructive optimizations of the experimental apparatuses. Binary and ternary combinations of ethanol and the siloxanes hexamethyldisiloxane (MM) and octamethytrisiloxane (MDM) will be investigated. The latter exhibit advantageous properties as working fluids in ORC processes as well as in high temperature heat pumps. The addition of ethanol can potentially enable higher transferred heat fluxes due to the significantly larger enthalpy of vaporization.