AixLib.Fluid.Storage.ExpansionVessel

# .AixLib.Fluid.Storage.ExpansionVessel

Expansion vessel with fixed pressure

## Information

This is a model of a pressure expansion vessel. The vessel has a constant pressure that is equal to the value of the parameter `p_start`. The model takes into account the energy and mass balance of the medium. It has no heat exchange with the ambient.

The expansion vessel needs to be used in closed loops that contain water to set a reference pressure and, for liquids where the density is modeled as a function of temperature, to allow for the thermal expansion of the liquid.

Note that alternatively, the model AixLib.Fluid.Sources.Boundary_pT may be used to set a reference pressure. The main difference between these two models is that in this model, there is an energy and mass balance for the volume. In contrast, for AixLib.Fluid.Sources.Boundary_pT, any mass flow rate that flows out of the model will be at a user-specified temperature. Therefore, AixLib.Fluid.Sources.Boundary_pT leads to smaller systems of equations, which may result in faster simulation.

## Revisions

- May 11, 2022, by Michael Wetter:
  Removed nonused parameter `p`.
  This is for IBPSA, #1614.
- May 29, 2014, by Michael Wetter:
  Removed undesirable annotation `Evaluate=true`.
- March 25, 2014 by Michael Wetter:
  Revised the model to use a constant pressure rather than a constant volume of water and gas. This leads to a simpler model.
- August 1, 2013 by Michael Wetter:
  Updated model to use new connector `mWat_flow`.
- February 7, 2012 by Michael Wetter:
  Revised due to changes in conservation equations in `AixLib.Fluid.Interfaces`.
- September 16, 2011 by Michael Wetter:
  Set `m(stateSelect=StateSelect.always)`, since setting the `stateSelect` attribute leads to smaller systems of equations.
- July 26, 2011 by Michael Wetter:
  Revised model to use new declarations from AixLib.Fluid.Interfaces.LumpedVolumeDeclarations.
- May 25, 2011 by Michael Wetter:
  Revised model due to a change in the fluid volume model.
- Nov. 4, 2009 by Michael Wetter:
  First implementation.

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