VCL Version 2.12

Vapor Cycle Library 2.12 is part of Modelon's 2024.1 release. New versions of Modelon's libraries are sold and distributed directly from Modelon, as well as approved resellers.

Version 2.12 contains the changes described below.

Build 1 (2024-02-14)

New features

  • All heat exchangers can now use temperature-dependent heat capacity and thermal conductivity for the solid wall. The "WallMaterial" parameter with constant properties remains for backwards-compatibility, and by default the properties specified there are used. To use temperature-dependent heat capacity and thermal conductivity, the new MaterialModel option need to be set to something other than the default which is constant properties. A table-based model is available, as well as cryogenic temperature models for different materials. When a MaterialModel is selected, parameters belonging to the selected model must also be set, for example tabulated properties versus temperature or coefficients for specific materials at low tempratures.
  • Added Summary and Initialization component views to see relevant variables and parameters on stickies. (Known limitation: Instantiating multiple components that extend from the same class, which has the component views defined, will not have their component views appear.)
  • Added conditional thermal mass and heat loss model to displacement compressor template VaporCycle.Compressors.Templates.VariableDisplacementCompressor with the default setting as false for backwards-compatibility.
  • Convection and wall thermal models were added to the Modelon base library (see release notes) for cryogenic and standard temperature applications. To show some of its possible uses, a new cryogenic tank filling example with horizontal tank geometry was added here, and a variant of the vertical tank filling example utilizing predictive heat transfer correllations from literature was added here.
  • Added new types of heat exchangers: sawtooth wire on tube heat exchanger and skin heat exchanger.


  • The air flow model of the heat exchanger VaporCycle.HeatExchangers.TwoPhaseAir.CrossFlow was improved for a more robust and accurate result in presence of moisture. In general the result differences are expected to be small, but to achieve results exactly as previous library versions, the Advanced tab parameter cp_arithmetic_mean can be set to true.
  • Added two further entries to the enumeration sizingParametrization used to prescribe different combinations of parameters to define the size and shape of hydrogen tank during sizing. These entries are also supported by the corresponding tank sizing models as illustrated in this experiment.
  • Changed default setting for condenseMoisture to true, to reduce risk of running a case with condensing air but neglecting the phenomenon in components VaporCycle.HeatExchangers.TwoPhaseAir.CrossFlow & VaporCycle.HeatExchangers.TwoPhaseAir.Examples.Evaporator.
  • In the package TankSizing (previously CryogenicH2) the hydrogen tank sizing models been upgraded to allow for the geometries of the end caps to be replaceable, and therefore more inline with the dynamic hydrogen tank models. The documentation and parametrization options have also been improved.
  • New accurate dormancy table used in class Cryogenic for hydrogen over a large range of densities between 5 and 80 kg/m3 which eliminates any noise previously visible for higher values of p_filling.
  • The lookup tables for R410a SBTL medium have been regenerated to cover a larger range.

Fixed issues

  • Improved the low Reynolds number behavior of the heat transfer correlation SinglePhaseGnielinski. Due to equations used by the correlation, the Nusselt number would swing inaccurately at Re < 1000, causing numerical problems. In the range 1000 < Re < 1200, Nu is now smoothly limited to be > 1, and staying there all the way down to Re = 0.
  • Ensured consistent use of the safety factor in all layers during the sizing of cryogenic hydrogen tanks, including the outer layer of vacuum insulated tanks.
  • In the heat exchanger component VaporCycle.HeatExchangers.TwoPhaseTwoPhase.CounterFlow, the selected WallMaterial properties were not propagated down to the wall sub-component and thereby not used. This has been fixed.
  • In the component VaporCycle.HeatExchangers.TwoPhaseAir.Examples.FlatTubeCondenser, the thermal resistance of the wall was uniformly distributed to the heat exchanger segments. Now the number of flat tubes per segment is taken into account, so a segment with more flat tubes will have increased thermal conductance due to more walls conducting heat.
  • Fixed a bug to ensure the overall heat transfer coefficient is used in the convective thermal conductance computation in the heat transfer correlation of WireAndTubeHX. This could cause a change in heat transfer rate.