VCL Version 6.0

Vapor Cycle Library 6.0 is part of Modelon's 2026.2 release. New versions of Modelon's libraries are sold and distributed directly from Modelon, as well as approved resellers.

Version 6.0 contains the changes described below.

New features

The dynamic cryogenic hydrogen storage tanks gained three capabilities from the underlying Modelon Base Library two-phase volume, which together widen the range of storage duty cycles that can be simulated.

These are changes to the dynamic tank volume only. The steady-state sizing models under VaporCycle.Experiments.HydrogenStorage.TankSizing are built on a separate framework that does not use that volume or the tank shape models, and are unaffected by everything described below, including the conversion note at the end.

  • Tanks whose fluid volume changes while the model runs. The tank shape dimensions are now time-varying inputs, so the enclosed volume, wall surfaces and tank height follow them during simulation. A mechanically imposed change of the stored volume - a deforming or bellows-type tank, or a prescribed movement of the upper fluid boundary - can be modelled directly rather than approximated by an imposed pressure. VerticalCylinderFlatEnds adds variableFluidHeight and the input L_fluid for the case of a moving upper boundary: the discretized wall stays on the physical tank length and its thermal history remains continuous as the fluid boundary sweeps across wall segments, while segments above the fluid exchange no heat with it. Supplying constant dimensions reproduces the previous behaviour exactly.
  • Complete disappearance of a phase. The non-equilibrium volume no longer becomes singular when the vapor or the liquid volume reaches zero, so a tank can be boiled dry, drawn down to exhaustion, or filled liquid-full without the simulation failing. Both ports hand over between phases rather than drawing from a phase that is no longer there: a vapor port at the top changes over from vapor to liquid as the liquid surface reaches it, and a liquid outlet at the bottom changes over from liquid to vapor as the liquid runs out, with the outlet enthalpy moving continuously between the two values. This makes usable-inventory and run-dry studies possible. The regularization is confined to a narrow band around the vanishing phase and leaves established results unchanged.
  • Compression through the critical pressure. The two-phase description is faded out as the pressure approaches critical and the two bulks are merged thermally with a user-settable time constant, representing the thermoacoustic effect that equalizes temperature very rapidly near the critical point. A tank can now be driven out of the two-phase dome, through the critical pressure into the supercritical region, held there, and expanded back down into the dome with the phase split re-establishing itself continuously on re-entry. The pool boiling correlation is faded into single-phase convection over the same band, so boiling heat transfer no longer has to be switched off by hand for a supercritical excursion.
  • The tank templates can expose thermal connectors on the inner wall surface, mirroring the existing outer-surface connectors, for attaching user-supplied boiling or convection correlations and additional wall-side phenomena. All relevant bulk and saturation properties, including the full thermodynamic state records of both bulks, are public on the volume, so an external correlation can be written against it without modifying the library.
  • Three new examples under VaporCycle.Experiments.HydrogenStorage demonstrate the above: CryoCompressedDormancy (a sealed cryo-compressed vessel self-pressurizing across the critical pressure and relieving back into the dome), NoVentFillToLiquidFull (a sealed fill continued until the ullage collapses) and LiquidExtractionToExhaustion (a liquid draw continued past the point where the liquid runs out).

Improvements

  • The hydrogen transport property functions in VaporCycle.Media.TransportProperties.Hydrogen were reformulated algebraically to remove an exponential overflow in the excess thermal conductivity term. Results are unchanged within the validity range; function evaluation failures at low temperature and high density are gone.
  • Property calls on the Helmholtz media evaluated from pressure and temperature now converge close to and at the critical point, where the previous iteration could diverge. This is what makes boiling and convection correlations usable on a tank approaching the critical pressure.
  • More robust steady-state initialization of VaporCycle.Tanks.SuctionAccumulator, LiquidReceiver and PhaseSeparator. The outlet flow resistance density now has a guess derived from the outlet state implied by the starting point (liquid level and outlet quality in the two-phase region, the starting enthalpy otherwise) instead of 1 kg/m3, which could make the initialization fail. The derived start values (saturation properties, quality, relative level and outlet density) are available as final parameters for other components to read.

Bug fixes

  • Fixed a typo in the package name VaporCycle.BaseClasses.HeatTransfer.TwoPhase.ReducedGeomtery, which has been renamed to ReducedGeometry.
  • Fixed a typo in the class name VaporCycle.Experiments.RefrigerationSystem.RefrigerationSystenInit, which has been renamed to RefrigerationSystemInit.

Back to top