Patch-based Thermodynamic Property Models for the Subcritical Region

Model-based design approaches for vapor-compression cycles depend heavily upon refrigerant property representations that are fast, accurate, and consistent. We describe an approach based upon B-spline interpolants that describes properties such as density, temperature, and specific entropy as the intersection of multiple surfaces, which are referred to as ”patches.” When combined with a transformation of thermodynamic coordinates, this approach can calculate the density over a domain with a maximum absolute percentage error less than ×1P− and a speedup over REFPROP of greater than 100x