Dynamic Modeling Methodology for Near Isothermal Compressor

Compressors are the vital component of the vapor compression systems and account for the majority of energy consumption. Developing appropriate controllers or optimizing compressor design can significantly reduce the carbon emissions. The isothermal compressor combines the compressor chamber and gas cooler, using the liquid piston to compress the working fluid for nearisothermal compression. This methodology can reach up to 30% energy saving compared to the traditional isentropic compression work. This paper leverages the CEEE Modelica Library (CML) to demonstrate a detailed isothermal compressor model that captures the nearisothermal compression process of transcritical carbon dioxide (CO2) cycle. The model uses the real experimental data as the boundary conditions, and the relevant component-level experimental validation was carried out by using a prototype with 1-ton nominal capacity. The results proved the accuracy of the dynamic model (7.5% relative error for chamber pressure and 0.74 K deviation for chamber temperature), and provide a guideline for designing the isothermal compressor chamber. Finally, the modeling for the isothermal compression cycle is ongoing and the field is still in its infancy.