Single Control Volume Initializer

The Single Control Volume Initializer is a hierarchical Initializer suitable for any unit model that involves a single control volume (either 0- or 1-dimensional control volume). This Initializer is the default for all unit models in IDAES unless the unit model overloads this with a different option.

This routine applies a hierarchical approach to initialize the StateBlock(s) within the model followed by calling a solver to converge the full model. The following steps are used to initialize the model:

  1. Determine if the control volume is 0- or 1-dimensional.

    1. For 0-D control volumes, initialize the inlet StateBlock using the appropriate Initializer followed by the outlet StateBlock. The outlet StateBlock may be initialized using an Initializer or by copying the state of the inlet StateBlock.

    2. For 1-D control volumes, initialize the indexed StateBlock using the appropriate Initializer.

  2. If present, initialize the ReactionBlock using the appropriate Initializer.

  3. Call user-specified solver to converge the full model.

This Initializer also supports plug-ins to the main model (sub-models which are attached to the main model after construction, such as costing calculations). If plug-ins are present, they are initialized according to the default sequence which is as follows:

  1. After fixing the degrees of freedom by before initializing the main model, iterate through model.initialization_order and call SubmodelInitializer.plugin_prepare for all plug-ins found.

  2. Iterate through model.initialization_order again and either call the main model initialization routine or SubmodelInitializer.plugin_initialize` as appropriate.

  3. Call user specified solver to converge the full model with all plug-ins.

  4. iterate through model.initialization_order in reverse and either call SubmodelInitializer.plugin_finalize for all plug-ins.

Users can specify Initializers for each sub-model (StateBlocks and plug-ins); if users do not specify an Initializer for a sub-model then the routine will default to either i) the default Initializer specified when the main model Initializer was instantiated or ii) the default Initializer for the sub-model (specified in submodel.default_initializer).

SingleControlVolumeUnitInitializer Class

class idaes.core.initialization.general_hierarchical.SingleControlVolumeUnitInitializer(**kwargs)[source]

This is a general purpose Initializer object for unit models which have a single Control Volume named ‘control_volume’.

For details of the initialization routine, please see the documentation.

constraint_tolerance

Tolerance for checking constraint convergence

output_level

Set output level for logging messages

solver

Solver to use for initialization

solver_options

Dict of options to pass to solver

default_submodel_initializer

Default Initializer object to use for sub-models. Only used if no Initializer defined in submodel_initializers.

always_estimate_states

Whether initialization routine should estimate values for state variables that already have values. Note that if set to True, this will overwrite any initial guesses provided.

initialize(model, initial_guesses=None, json_file=None, output_level=None, exclude_unused_vars=False)

Execute full initialization routine.

Parameters

  • model (Block) – Pyomo model to be initialized.

  • initial_guesses (Optional[dict]) – dict of initial guesses to load.

  • json_file (Optional[str]) – file name of json file to load initial guesses from as str.

  • output_level – (optional) output level to use during initialization run (overrides global setting).

  • exclude_unused_vars (bool) – whether to ignore unused variables when doing post-initialization checks.

Note - can only provide one of initial_guesses or json_file.

Returns

InitializationStatus Enum

Parameters
precheck(model)

Check for satisfied degrees of freedom before running initialization.

Parameters

model (Block) – Pyomo Block to fix states on.

Returns

None

Raises

InitializationError if Degrees of Freedom do not equal 0. –