Version 4.2

Modelon Library 4.2 is part of Modelon’s 2023.1 release.

New Features


  • Single phase - two phase adapter. Added an adapter that allows converting a fluid representation from two-phase to single phase. This is useful if a subsystem where the fluid appear in both liquid and vapor phase needs to be connected to another subsystem where the same fluid appear only as liquid or gas. This subsystem can then use a simplified medium representation and the adapter be used to connect the two subsystems. Examples of adapter use are avaiable in this package.
  • Added a TwoPhaseTank component that allows modelling a two-phase fluid in a volume, where both liquid and vapor phases are present and not in thermodynamic equilibrium. An example using this component is HeatedSteamStorage.



  • All temperature, pressure and density functions are now smoothed. As a result of this, both the first and second order derivatives are defined.


  • Multiple corrections that remove warnings from compilation logs. No results are affected by these changes.
  • Improved convergence in some cases when solving density & temperature from pressure and specific enthalpy in media based on Helmholtz equation of state.
  • Added asserts to abort the property evaluation if two-phase fluid (SBTL & Helmholtz equation of state) properties are evaluated outside the medium validity range. Previously this typically resulted in follow-up errors later in the property evaluation, but now gives clearer error message in case simulating out of the valid range. Practically most evaluations out of range are caused by iterative solvers looking for a solution to a non-linear system. In this case the assert will primarily result in the solver adjusting the step and the error is not printed to the log. This improved robustnes and performance of models with such non-linear systems.
  • Improved convergence in some cases when computing fluid properties from density and temperature for SBTL media.
  • Added analytical derivative functions for the bubble & dew enthalpy & density functions for two-phase media using Helmholtz equation of state. This reduces the need for numerical Jacobian for models using these media.
  • In simplified transport properties for liquids, assert against calls at 0 K temperature. This could happen during solving of non-linear systems, and assert on the input is usually more efficiently handled by the solver compared to other means of handling function calls far outside the validity range.

Minor Improvements

  • For DataAccess.JSON, parson, the third-party software for parsing json, has been updated to 1.5.0.
  • For DataAccess.XML, pugixml, the third-party software for parsing xml, has been updated to 1.13.
  • The model Modelon.Utilities.Limits.RealLimitFault now includes the option to generate events or not for the warning action (default is no event) and to display the time of the event.
  • In Modelon.ThermoFluid.Volumes.SubComponents.LumpedPhaseSeparator, the variable level now has a start-attribute derived from initialization parameters.
  • Corrected non-standardized annotations in Modelon.ThermoFluid.

Minor Changes

  • The blocks in Sources.RandomNumbers have all been renamed to begin with an uppercase letter.
  • The Icon.Constants class has been removed and any references to it should be converted to use Icons.ConstantsPackage. This should have been done automatically when converting to MBL 4.0, otherwise a manual conversion will be required.
  • The material property record Modelon.ThermoFluid.Solids.ConstantProperties.SolidMaterial is now non-partial, to allow parameter instances of it.

Fixed issues

  • Fixed bug in Modelon.Mechanics.Rotational3D.Shaft that caused non-zero flange angle initialization with universal joints and relaxing one of the fork rotations using the relax_joint_angle parameter.
  • Fixed a typo in the correlation constants for nucleate boiling. Added fluid dependent coefficient for fluids other than water in EvaporationKandlikar. Modified information to indicate default correlation for use with water.

Conversion of User Libraries

User libraries will automatically be converted from version 4.1. These conversions are made using the included conversion script: Modelon/Resources/Scripts/Convert_to_4.2.mos.