VCL Version 5.0

Vapor Cycle Library 5.0 is part of Modelon's 2026.1 release. New versions of Modelon's libraries are sold and distributed directly from Modelon, as well as approved resellers.

Version 5.0 contains the changes described below.

New features

  • SBTL based Isobutane media is added to Media.TableBasedProperties.SBTL sub-package
  • The two-phase capillary flow channel now has the option to initialize to a given pressure and steam quality (X_out), in addition to the combination of pressure and temperature/enthalpy.

Improvements

  • Changes for improved simulation performance and robustness of two-phase fluids:
    • The wall sub-component in heat exchangers now has two temperature states per segment, reducing or removing the need for iterative solving of convection models. The previously used, single temperature state per segment can be brought back if needed by setting the "surfaceState" parameter on the wall sub-component to false.
    • All heat transfer correlations for two-phase fluids now have the option to filter or "relax" the heat transfer coefficients, which can improve simulation performance for transient scenarios. This option can be enabled either for single components by setting the useRelaxation parameter on the "Advanced" tab of correlation parameters, or for all components in a system by including the Modelon.ThermoFluid.Settings_TF component and enabling the useRelaxation parameter there. When enabled, the time constant of heat transfer coefficients can be determined by the parameter "tau". Values in the range of 1 to 10 seconds are recommended.
    • Minor changes to equations in the two-phase flow channel component that reduce risk of simulation slow-down. These changes only affect the transient behavior, not steady-state results.
  • In the parameter record for specifying the initial fluid state for two-phase fluids in all heat exchanger components, the following parameters have been renamed:
    • saturated_in was renamed to give_quality_in
    • saturated_out was renamed to give_quality_out
  • The specific heat capacity of the soldered wall in CapillarySuctionLine is improved by taking weighted average of the specifc heat capacity values of capillary tube, suction line and soldering material.
  • The minimum allowed thickness of pressure vessels in component under VaporCycle.Experiments.HydrogenStorage.TankSizing has been changed. The ASME Boiler and Pressure Vessel Code prescribes a minimum allowed thickness of 1.5 mm for any pressure vessel, however the model previously applied the safety factor to this limit. That is not neccessary. Previously this lower limit was not possible to change, but now it is a parameter of the "layer1" sub-component in tank models for sizing. Simulation results of existing user models will change due to this change, if the resulting pressure vessel thickness was previously limited to the sf * 1.5 mm lower limit. The lower default limit is now 1.5 mm. To reproduce previous results exactly, set the "layer1.t_u" parameter to sf * 1.5 mm.
  • SimpleTXV has been enhanced to provide greater control over the initialization of the integrator output of the internal LimPI controller, improving start-up behavior and physical consistency.
  • Improved handling of compressor startup from zero speed.
  • To maintain consistency across the library, all components have been updated to use MoistAirIce as the default medium instead of MoistAir. This change applies to HeatExchangers, FlowModifiers, sensors, and source components. The list of components with modified default media is provided below.
    • CrossFlow , HeatPumpCircuitBase , CompressorWithOutletCooler , LiquefactionSystem , MultiStageCompressor_AirCooled , RefrigerationCircuitBase
    • SetAirFlowRate , SetAirTemperature , PlateOnTube
    • RollBond , Sawtooth , Skin , WireAndTube
    • AirTemperature , AirFlowSource , AirPressureSource

    Note: This update may cause failures in some user models, showing errors such as: 

            Error in flattened model:
        Connected variables with modified quantity attribute must have the same quantity:
        'airOut_evap.port[1].m_flow' has quantity 'MassFlowRate.Moist air simple'
        This is likely caused by mismatching media packages in the connected components.

    If required, users can change the default medium back to MoistAir in their system models.

Bug fixes

  • Illegal modifiers from the following components has been fixed.
    1. TwoPhaseAir.CrossFlow_Sizing
    2. TwoPhaseLiquid.Dynamic_Sizing
    3. TwoPhaseTwoPhase.Dynamic_Sizing

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