Validated thermodynamic model of a R-744 heat pump using Dymola

Heat pumps are widely recognized as a key technology for addressing global warming by replacing fossil fuel-based heating systems, thereby significantly reducing carbon emissions. However, current heat pump technologies often rely on refrigerants with high environmental impact or may exhibit reduced performance under certain operating conditions, potentially leading to increased electricity consumption that offsets their decarbonization benefits. Among natural refrigerants, CO2 (R-744) is non-toxic, has good thermodynamic properties, a low Global Warming Potential (GWP), is free from PFAS-related concerns, and is cost-effective. To assess its potential, simulation tools capable of dynamic analysis are increasingly being used to better predict system behavior under real operating conditions. In this study, a thermodynamic model of a water-to-water heat pump for space heating was developed using Dymola software in the Modelica environment. The model was validated against experimental data. The validation focused on key components of the heat pump, including the gas cooler, evaporator, and compressor. Once validated, the model provides a solid foundation for analyzing system behavior under variable operating conditions and for supporting future dynamic performance assessments. The ultimate goal of the project is to extend this approach to CO2/Propane mixtures, in order to investigate their dynamic behavior in heat pump systems.