Equations of State (EOS) are semi-empirical models used to calculate the physical and transport properties of fluids, required in the design of the components in a practical system. In order to have a reliable EOS, accurate experimental fluid data is required. However, in the near-critical region, especially for newer fluids, only limited experimental data is available. In recent years, operation in this region is gaining in interest for low-temperature heat recovery applications (which can convert geothermal, solar and waste heat into electricity or useful heat). Therefore, in previous years, an experimental setup, called a flow calorimeter, has been built (see figure) in order to extend the experimental database of isobaric specific heat capacities of newer refrigerants with a low Global Warming Potential (GWP), specifically in the near-critical region. This setup has been calibrated and initial data has been collected, however, a much more vast database is required, on several refrigerants, to develop sound EOS.