Refrigerant property calculation has a significant impact on the computational performance of vapor compression cycle simulations. This paper summarizes a Modelica implementation of Spline-Based Table Look-Up Method (SBTL) for fast calculation of refrigerant properties. External C functions are used for faster spline evaluation and inversion. Significant improvement in computation speed was observed without sacrificing accuracy. An SBTL property model of R134a is first validated against a highly accurate Helmholtz energy equation of state (EOS) model. Then the new model was tested rigorously from single function calls, to heat exchanger test bench, to system models of the vapor compression cycle in Modelon's Air Conditioning Library. Finally, an SBTL property model of R1234yf was used in a drive cycle simulation and a shutdown-startup test of two complex air conditioning system models developed at the Ford Motor Company. These system models are running more than twice the speed of the ones using Helmholtz energy EOS.

Refrigerant property calculation has a significant impact on the computational performance of vapor compression cycle simulations. In a previous publication, the authors have described the Modelica implementation of a Spline-Based Table Look-Up Method (SBTL) for fast calculation of refrigerant properties. This implementation demonstrated significant improvement in computational speed for a range of complex air conditioning system models. This paper describes further development of the SBTL method to allow the generation of analytic Jacobians. The new implementation with analytic Jacobian capability is tested on a range of air conditioning system models and demonstrates significant further improvement of computational speed when compared to the original SBTL model.