Holdup ClassesΒΆ

The IDAES process modeling framework is built around the concept of Holdup Blocks. A Holdup Block represents a single volume of material over which a set of material, energy and pressure balances can be applied.

Whilst each unit model is different, the material, energy and momentum balances all have a similar form with the main difference being the terms which appear in the balances. This allows the Holdup blocks to automatically generate the balance equations based on a set of instructions provided by the user, saving the user from the need to write the equations themselves. This section of the IDAES documentation goes through the different types of Holdup blocks available in the IDAES core framework the equations they create.

The IDAES framework contains three types of Holdup blocks for different applications; Holdup0D, Holdup1D and HoldupStatic.

  • Holdup0D is the most common type of Holdup block, and represents a single well mixed volume of fluid with a single inlet flow and a single outlet flow. This type of Holdup block is uesfull for representing most simple unit operations.
  • Holdup1D is useful for holdup volumes with variations in one spatial domain, such as plug flow reactors or flow in pipes.
  • HoldupStatic is useful for certain special cases where the material volume has either no through flow (dead zones) or units with negligible volume (e.g. ideal mixers and splitters). More details on potential uses of HoldupStatic are given below.

Holdup blocks are not intended to be used outside of an IDAES UnitModel. Most significantly, the Holdup block expects certain components to be present in the parent model, and will raise Exceptions if these are not present.