abstract
The decarbonization of industrial heat supply is a key component of the energy transition, as heat generation accounts for a substantial share of global energy consumption and energy-related CO2 emissions. In particular, the recovery of industrial waste heat offers significant potential for improving energy efficiency and reducing the reliance on fossil fuels. For high-temperature applications, the vapor compression heat pump with a solution circuit represents a promising technology. By employing a binary working fluid instead of a pure substance, the additional degree of freedom provided by the fluid composition enables flexible adjustment of the phase-change behavior to the requirements of the thermodynamic cycle. Consequently, the selection of suitable working fluid mixtures is crucial for both the efficiency and technical feasibility of the system. At the same time, regulatory developments, particularly the planned phase-out of partially or fully fluorinated working fluids, increasingly restrict the range of viable mixture components to natural substances. In this context, a methodology was developed for the identification, thermodynamic calculation and simulation of natural working fluid mixtures for application in vapor compression heat pumps with solution circuits. Firstly, a database containing 324 pure substances was established and four industrial application scenarios were defined. These include the integration of thermal processes with cooling applications, heat supply to district heating networks, steam generation and the provision of industrial process heat. A filtering algorithm was developed to identify promising purecomponent combinations based on substance- and mixture-specific selection criteria. Subsequently, thermodynamic mixture data was calculated for selected mixtures and used for cycle simulations. The proposed methodology enabled the identification of several suitable working fluid mixtures for the defined application scenarios and revealed key influences of mixture behavior on cycle performance. It therefore provides a systematic framework for the identification and evaluation of natural working fluid mixtures and supports their future application in high-temperature vapor compression heat pumps with solution circuits.