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Release Notes for Air Conditioning Library 1.17

AirConditioning Library 1.17 is part of Modelon’s 2018.2 release. New versions of Modelon’s libraries are sold and distributed directly from Modelon, as well as approved resellers.

With version 1.17, the Air Conditioning Library has seen major improvements in simulation performance, both with respect to speed and robustness.

Highlights of this release include new table-based implementations of R1234yf and R134a that reduce simulation time of cycle models with approx. 40% and efficient transport properties of the high-accuracy R1234yf medium, increasing the simulation speed by approx. 20% for a complex drive-cycle. There are also improvements in medium properties at the phase boundary and in the Chen evaporation correlation which increase simulation robustness.

New features

  • Fast table-based implementations of R1234yf and R134a are added to the library. Table-based media can be used as an alternative to the default high-accuracy Helmholtz based media when simulation speed is prioritized. Note: The table based media models included in this release should be treated as beta versions. The table data was generated using the Short Helmholtz Equation properties (Span 2000) for R1234a and the reference properties for R1234yf. Currently, these are compatible with C compilers only. They are not compatible with GCC compilers.

Enhancements

  • New transport property correlations are added to the R1234yf and R1234yf_smooth medium packages. They replace the previous correlations, which were based on an Extended Corresponding State approach and considered less accurate and robust. The newly implemented correlations from the open literature are:
    • Richard A.Perkins and Marcia L.Huber : Measurement and Correlation of the Thermal Conductivity of 2,3,3,3-Tetrafluoroprop-1-ene (R1234yf) and trans-1,3,3, 3-Tetrafluoropropene (R1234ze(E)). J. Chem. Eng. Data, 56:4868–4874, 2011
    • Marcia L.Huber and Marc J.Assael : Correlations for the Viscosity of 2,3,3,3-Tetrafluoroprop-1-ene (R1234yf) and trans-1,3,3,3-Tetrafluoropropene (R1234ze(E)). Int J Refrig. 2016 Nov; 71: 39–45
  • Since the performance of the new transport properties is considered far superior to the previously implemented solution, they are added to the R1234yf medium packages without providing automatic conversion to the old behavior for existing user models. If you wish to use the previous transport property packages, choose the corresponding deprecated packages. They will however be removed at some point in a future release.
  • Smoothing of density derivatives at the phase boundary was improved for the property packages R1234yf_smooth and R134a_smooth, such that potential robustness issues are avoided.
  • Refrigerant side gaps in the solid material between layers are now correctly taken into account in the computation of the component mass. The gap is specified by the user with an additional parameter. Deviations to previous versions are expected for the thermal capacity of multi-layer flattube heat exchangers if a gap larger than zero is chosen. Steady-state results are not affected in that case except for the solid weight of the component.
  • The numerical robustness of the Chen evaporation heat transfer model is improved. The correlation handles low flow better numerically, which improves the convergence rate of non-linear equation systems.
  • Pressure initialization in heat exchangers with headers could previously easily lead to reversed initial flow rates in the component. The consistent propagation of start values from the component top level now eliminates this pitfall.

Conversion of user libraries

No conversion of user libraries is required.

Requirements

AirConditioning Library 1.17 is based on ThermoFluidPro Library 1.17, Modelica Standard Library 3.2.2. and UserInteraction 0.64.

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