control_volume0d.py

#################################################################################
# The Institute for the Design of Advanced Energy Systems Integrated Platform
# Framework (IDAES IP) was produced under the DOE Institute for the
# Design of Advanced Energy Systems (IDAES).
#
# Copyright (c) 2018-2026 by the software owners: The Regents of the
# University of California, through Lawrence Berkeley National Laboratory,
# National Technology & Engineering Solutions of Sandia, LLC, Carnegie Mellon
# University, West Virginia University Research Corporation, et al.
# All rights reserved.  Please see the files COPYRIGHT.md and LICENSE.md
# for full copyright and license information.
#################################################################################
"""
Base class for control volumes.
"""

# TODO: Missing docstrings
# pylint: disable=missing-function-docstring

# We use some private attributes here to hide these from the user
# pylint: disable=protected-access

__author__ = "Andrew Lee, Douglas Allan"

# Import Pyomo libraries
from pyomo.environ import Constraint, Reals, units as pyunits, Var, value
from pyomo.common.collections import ComponentMap
from pyomo.dae import DerivativeVar
from pyomo.common.deprecation import deprecation_warning

# Import IDAES cores
from idaes.core import (
    declare_process_block_class,
    ControlVolumeBlockData,
    FlowDirection,
    MaterialFlowBasis,
    MaterialBalanceType,
)
from idaes.core.util.exceptions import (
    BalanceTypeNotSupportedError,
    BurntToast,
    ConfigurationError,
    PropertyNotSupportedError,
)
from idaes.core.util.tables import create_stream_table_dataframe
from idaes.core.util import scaling as iscale
import idaes.logger as idaeslog
from idaes.core.base.control_volume_base import ControlVolumeScalerBase

from idaes.core.scaling import DefaultScalingRecommendation

_log = idaeslog.getLogger(__name__)

# TODO : Custom terms in material balances, other types of material balances
# TODO : Improve flexibility for get_material_flow_terms and associated


class ControlVolume0DScaler(ControlVolumeScalerBase):
    """
    Scaler object for the ControlVolume0D
    """

    DEFAULT_SCALING_FACTORS = {
        # We could scale volume by magnitude if it were being fixed
        # by the user, but we often have the volume given by an
        # equality constraint involving geometry in the parent
        # unit model.
        "volume": DefaultScalingRecommendation.userInputRequired,
        "phase_fraction": 10,  # May have already been created by property package
    }

    def _get_reference_state_block(self, model):
        """
        This method gives the parent class ControlVolumeScalerBase
        methods a state block with the same index as the material
        and energy balances to get scaling information from
        """
        return model.properties_out

    def variable_scaling_routine(
        self, model, overwrite: bool = False, submodel_scalers: ComponentMap = None
    ):
        """
        Routine to apply scaling factors to variables in model.

        Derived classes must overload this method.

        Args:
            model: model to be scaled
            overwrite: whether to overwrite existing scaling factors
            submodel_scalers: ComponentMap of Scalers to use for sub-models

        Returns:
            None
        """
        self.call_submodel_scaler_method(
            submodel=model.properties_in,
            submodel_scalers=submodel_scalers,
            method="variable_scaling_routine",
            overwrite=overwrite,
        )
        self.propagate_state_scaling(
            target_state=model.properties_out,
            source_state=model.properties_in,
            overwrite=overwrite,
        )
        self.call_submodel_scaler_method(
            submodel=model.properties_out,
            submodel_scalers=submodel_scalers,
            method="variable_scaling_routine",
            overwrite=overwrite,
        )
        if hasattr(model, "volume"):
            for v in model.volume.values():
                self.scale_variable_by_default(v, overwrite=overwrite)
        if hasattr(model, "phase_fraction"):
            for v in model.phase_fraction.values():
                self.scale_variable_by_default(v, overwrite=overwrite)

        super().variable_scaling_routine(
            model, overwrite=overwrite, submodel_scalers=submodel_scalers
        )

    def constraint_scaling_routine(
        self, model, overwrite: bool = False, submodel_scalers: ComponentMap = None
    ):
        """
        Routine to apply scaling factors to constraints in model.

        Derived classes must overload this method.

        Args:
            model: model to be scaled
            overwrite: whether to overwrite existing scaling factors
            submodel_scalers: ComponentMap of Scalers to use for sub-models

        Returns:
            None
        """
        for props in [model.properties_in, model.properties_out]:
            self.call_submodel_scaler_method(
                submodel=props,
                submodel_scalers=submodel_scalers,
                method="constraint_scaling_routine",
                overwrite=overwrite,
            )

        super().constraint_scaling_routine(
            model, overwrite=overwrite, submodel_scalers=submodel_scalers
        )


@declare_process_block_class(
    "ControlVolume0DBlock",
    doc="""
    ControlVolume0DBlock is a specialized Pyomo block for IDAES non-discretized
    control volume blocks, and contains instances of ControlVolume0DBlockData.

    ControlVolume0DBlock should be used for any control volume with a defined
    volume and distinct inlets and outlets which does not require spatial
    discretization. This encompasses most basic unit models used in process
    modeling.""",
)
class ControlVolume0DBlockData(ControlVolumeBlockData):
    """
    0-Dimensional (Non-Discretized) ControlVolume Class

    This class forms the core of all non-discretized IDAES models. It provides
    methods to build property and reaction blocks, and add mass, energy and
    momentum balances. The form of the terms used in these constraints is
    specified in the chosen property package.
    """

    default_scaler = ControlVolume0DScaler

    def add_geometry(self):
        """
        Method to create volume Var in ControlVolume.

        Args:
            None

        Returns:
            None
        """
        units = self.config.property_package.get_metadata().get_derived_units

        self.volume = Var(
            self.flowsheet().time,
            initialize=1.0,
            doc="Volume of material in control volume",
            units=units("volume"),
        )

    def add_state_blocks(
        self, information_flow=FlowDirection.forward, has_phase_equilibrium=None
    ):
        """
        This method constructs the inlet and outlet state blocks for the
        control volume.

        Args:
            information_flow: a FlowDirection Enum indicating whether
                information flows from inlet-to-outlet or outlet-to-inlet
            has_phase_equilibrium: indicates whether equilibrium calculations
                will be required in state blocks
            package_arguments: dict-like object of arguments to be passed to
                state blocks as construction arguments

        Returns:
            None
        """
        if has_phase_equilibrium is None:
            raise ConfigurationError(
                "{} add_state_blocks method was not provided with a "
                "has_phase_equilibrium argument.".format(self.name)
            )
        elif has_phase_equilibrium not in [True, False]:
            raise ConfigurationError(
                "{} add_state_blocks method was provided with an invalid "
                "has_phase_equilibrium argument. Must be True or False".format(
                    self.name
                )
            )

        tmp_dict = dict(**self.config.property_package_args)
        tmp_dict["has_phase_equilibrium"] = has_phase_equilibrium
        # tmp_dict["parameters"] = self.config.property_package

        if information_flow == FlowDirection.forward:
            tmp_dict["defined_state"] = True
        elif information_flow == FlowDirection.backward:
            tmp_dict["defined_state"] = False
        else:
            raise ConfigurationError(
                "{} invalid value for information_flow argument. "
                "Valid values are FlowDirection.forward and "
                "FlowDirection.backward".format(self.name)
            )

        self.properties_in = self.config.property_package.build_state_block(
            self.flowsheet().time, doc="Material properties at inlet", **tmp_dict
        )

        # Reverse defined_state
        tmp_dict_2 = dict(**tmp_dict)
        tmp_dict_2["defined_state"] = not tmp_dict["defined_state"]

        self.properties_out = self.config.property_package.build_state_block(
            self.flowsheet().time, doc="Material properties at outlet", **tmp_dict_2
        )

    def add_reaction_blocks(self, has_equilibrium=None):
        """
        This method constructs the reaction block for the control volume.

        Args:
            has_equilibrium: indicates whether equilibrium calculations
                will be required in reaction block
            package_arguments: dict-like object of arguments to be passed to
                reaction block as construction arguments

        Returns:
            None
        """
        if has_equilibrium is None:
            raise ConfigurationError(
                "{} add_reaction_blocks method was not provided with a "
                "has_equilibrium argument.".format(self.name)
            )
        elif has_equilibrium not in [True, False]:
            raise ConfigurationError(
                "{} add_reaction_blocks method was provided with an "
                "invalid has_equilibrium argument. Must be True or False".format(
                    self.name
                )
            )

        tmp_dict = dict(**self.config.reaction_package_args)
        tmp_dict["state_block"] = self.properties_out
        tmp_dict["has_equilibrium"] = has_equilibrium

        self.reactions = self.config.reaction_package.build_reaction_block(
            self.flowsheet().time,
            doc="Reaction properties in control volume",
            **tmp_dict,
        )

    def _add_material_balance_common(
        self,
        balance_type,
        has_rate_reactions,
        has_equilibrium_reactions,
        has_phase_equilibrium,
        has_mass_transfer,
        custom_molar_term,
        custom_mass_term,
    ):
        # Get dynamic and holdup flags from config block
        dynamic = self.config.dynamic
        has_holdup = self.config.has_holdup

        component_list = self.properties_in.component_list
        phase_list = self.properties_in.phase_list
        pc_set = self.properties_in.phase_component_set

        # Check that reaction block exists if required
        rblock = None
        if has_rate_reactions or has_equilibrium_reactions:
            try:
                rblock = self.reactions
            except AttributeError:
                raise ConfigurationError(
                    "{} does not contain a Reaction Block, but material "
                    "balances have been set to contain reaction terms. "
                    "Please construct a reaction block before adding "
                    "balance equations.".format(self.name)
                )

        if has_equilibrium_reactions:
            # Check that reaction block is set to calculate equilibrium
            for t in self.flowsheet().time:
                if self.reactions[t].config.has_equilibrium is False:
                    raise ConfigurationError(
                        "{} material balance was set to include "
                        "equilibrium reactions, however the associated "
                        "ReactionBlock was not set to include equilibrium "
                        "constraints (has_equilibrium_reactions=False). "
                        "Please correct your configuration arguments.".format(self.name)
                    )

        if has_phase_equilibrium:
            # First, check that phase equilibrium makes sense
            if len(self.config.property_package.phase_list) < 2:
                msg = (
                    "Property package has only one phase; control volume cannot include phase "
                    "equilibrium terms. Some property packages support phase equilibrium "
                    "implicitly in which case additional terms are not necessary. "
                    "You should set has_phase_equilibrium=False."
                )
                deprecation_warning(
                    msg=msg, logger=_log, version="2.0.0", remove_in="2.14.0"
                )
                has_phase_equilibrium = False
            else:
                # Check that state blocks are set to calculate equilibrium
                for t in self.flowsheet().time:
                    if not self.properties_out[t].config.has_phase_equilibrium:
                        raise ConfigurationError(
                            "{} material balance was set to include phase "
                            "equilibrium, however the associated outlet "
                            "StateBlock was not set to include equilibrium "
                            "constraints (has_phase_equilibrium=False). Please"
                            " correct your configuration arguments.".format(self.name)
                        )
                    if not self.properties_in[t].config.has_phase_equilibrium:
                        raise ConfigurationError(
                            "{} material balance was set to include phase "
                            "equilibrium, however the associated inlet "
                            "StateBlock was not set to include equilibrium "
                            "constraints (has_phase_equilibrium=False). Please"
                            " correct your configuration arguments.".format(self.name)
                        )

        # Get units from property package
        units = self.config.property_package.get_metadata().get_derived_units

        if (
            self.properties_in[self.flowsheet().time.first()].get_material_flow_basis()
            == MaterialFlowBasis.molar
        ):
            flow_units = units("flow_mole")
        elif (
            self.properties_in[self.flowsheet().time.first()].get_material_flow_basis()
            == MaterialFlowBasis.mass
        ):
            flow_units = units("flow_mass")
        else:
            flow_units = None

        # Get units for accumulation term if required
        acc_units = None
        if self.config.dynamic:
            f_time_units = self.flowsheet().time_units
            if (f_time_units is None) ^ (units("time") is None):
                raise ConfigurationError(
                    "{} incompatible time unit specification between "
                    "flowsheet and property package. Either both must use "
                    "units, or neither.".format(self.name)
                )

            if f_time_units is None:
                acc_units = None
            elif (
                self.properties_in[
                    self.flowsheet().time.first()
                ].get_material_flow_basis()
                == MaterialFlowBasis.molar
            ):
                acc_units = units("amount") / f_time_units
            elif (
                self.properties_in[
                    self.flowsheet().time.first()
                ].get_material_flow_basis()
                == MaterialFlowBasis.mass
            ):
                acc_units = units("mass") / f_time_units
            else:
                acc_units = None

        # Check if reaction package exists, and get units
        if hasattr(self.config, "reaction_package"):
            if self.config.reaction_package is not None:
                if (
                    self.reactions[
                        self.flowsheet().time.first()
                    ].get_reaction_rate_basis()
                    == MaterialFlowBasis.molar
                ):
                    rxn_flow_units = units("flow_mole")
                elif (
                    self.reactions[
                        self.flowsheet().time.first()
                    ].get_reaction_rate_basis()
                    == MaterialFlowBasis.mass
                ):
                    rxn_flow_units = units("flow_mass")
                else:  # reaction basis not defined
                    rxn_flow_units = None
            else:  # reaction package is NoneType object
                rxn_flow_units = None
        else:  # reaction package not defined
            rxn_flow_units = None

        # Test for components that must exist prior to calling this method
        if has_holdup:
            if not hasattr(self, "volume"):
                raise ConfigurationError(
                    "{} control volume must have volume defined to have "
                    "holdup and/or rate reaction terms. Please call the "
                    "add_geometry method before adding balance equations.".format(
                        self.name
                    )
                )

        # Material holdup and accumulation
        if has_holdup:
            if (
                self.properties_in[
                    self.flowsheet().time.first()
                ].get_material_flow_basis()
                == MaterialFlowBasis.mass
            ):
                holdup_units = units("mass")
            elif (
                self.properties_in[
                    self.flowsheet().time.first()
                ].get_material_flow_basis()
                == MaterialFlowBasis.molar
            ):
                holdup_units = units("amount")
            else:
                holdup_units = None

            self.material_holdup = Var(
                self.flowsheet().time,
                pc_set,
                domain=Reals,
                initialize=1.0,
                doc="Material holdup in control volume",
                units=holdup_units,
            )
        if dynamic:
            self.material_accumulation = DerivativeVar(
                self.material_holdup,
                wrt=self.flowsheet().time,
                doc="Material accumulation in control volume",
                units=acc_units,
            )

        # Create material balance terms as required
        # Kinetic reaction generation
        if has_rate_reactions:
            if not hasattr(self.config.reaction_package, "rate_reaction_idx"):
                raise PropertyNotSupportedError(
                    "{} Reaction package does not contain a list of rate "
                    "reactions (rate_reaction_idx), thus does not support "
                    "rate-based reactions.".format(self.name)
                )
            self.rate_reaction_generation = Var(
                self.flowsheet().time,
                pc_set,
                domain=Reals,
                initialize=0.0,
                doc="Amount of component generated in unit by kinetic reactions",
                units=rxn_flow_units,
            )  # use reaction package flow basis

        # Equilibrium reaction generation
        if has_equilibrium_reactions:
            if not hasattr(self.config.reaction_package, "equilibrium_reaction_idx"):
                raise PropertyNotSupportedError(
                    "{} Reaction package does not contain a list of "
                    "equilibrium reactions (equilibrium_reaction_idx), thus "
                    "does not support equilibrium-based reactions.".format(self.name)
                )
            self.equilibrium_reaction_generation = Var(
                self.flowsheet().time,
                pc_set,
                domain=Reals,
                initialize=0.0,
                doc="Amount of component generated in control volume "
                "by equilibrium reactions",
                units=rxn_flow_units,
            )  # use reaction package flow basis

        # Inherent reaction generation
        if self.properties_out.include_inherent_reactions:
            if not hasattr(self.config.property_package, "inherent_reaction_idx"):
                raise PropertyNotSupportedError(
                    "{} Property package does not contain a list of "
                    "inherent reactions (inherent_reaction_idx), but "
                    "include_inherent_reactions is True.".format(self.name)
                )
            self.inherent_reaction_generation = Var(
                self.flowsheet().time,
                pc_set,
                domain=Reals,
                initialize=0.0,
                doc="Amount of component generated in control volume "
                "by inherent reactions",
                units=flow_units,
            )  # use property package flow basis

        # Phase equilibrium generation
        if has_phase_equilibrium and balance_type == MaterialBalanceType.componentPhase:
            if not hasattr(self.config.property_package, "phase_equilibrium_idx"):
                raise PropertyNotSupportedError(
                    "{} Property package does not contain a list of phase "
                    "equilibrium reactions (phase_equilibrium_idx), thus does "
                    "not support phase equilibrium.".format(self.name)
                )
            self.phase_equilibrium_generation = Var(
                self.flowsheet().time,
                self.config.property_package.phase_equilibrium_idx,
                domain=Reals,
                initialize=0.0,
                doc="Amount of generation in control volume by phase equilibria",
                units=flow_units,
            )  # use property package flow basis

        # Material transfer term
        if has_mass_transfer:
            self.mass_transfer_term = Var(
                self.flowsheet().time,
                pc_set,
                domain=Reals,
                initialize=0.0,
                doc="Component material transfer into unit",
                units=flow_units,
            )

        # Create rules to substitute material balance terms
        # Accumulation term
        def accumulation_term(b, t, p, j):
            return (
                pyunits.convert(b.material_accumulation[t, p, j], to_units=flow_units)
                if dynamic
                else 0
            )

        def phase_equilibrium_term(b, t, p, j):
            sd = {}
            for r in b.config.property_package.phase_equilibrium_idx:
                if b.config.property_package.phase_equilibrium_list[r][0] == j:
                    if b.config.property_package.phase_equilibrium_list[r][1][0] == p:
                        sd[r] = 1
                    elif b.config.property_package.phase_equilibrium_list[r][1][1] == p:
                        sd[r] = -1
                    else:
                        sd[r] = 0
                else:
                    sd[r] = 0

            return sum(
                b.phase_equilibrium_generation[t, r] * sd[r]
                for r in b.config.property_package.phase_equilibrium_idx
            )

        # TODO: Need to set material_holdup = 0 for non-present component-phase
        # pairs. Not ideal, but needed to close DoF. Is there a better way?

        # Material Holdup
        if has_holdup:
            if not hasattr(self, "phase_fraction"):
                self._add_phase_fractions()

            @self.Constraint(
                self.flowsheet().time, pc_set, doc="Material holdup calculations"
            )
            def material_holdup_calculation(b, t, p, j):
                if (p, j) in pc_set:
                    return b.material_holdup[t, p, j] == (
                        b.volume[t]
                        * self.phase_fraction[t, p]
                        * b.properties_out[t].get_material_density_terms(p, j)
                    )

        if has_rate_reactions:
            # Add extents of reaction and stoichiometric constraints
            self.rate_reaction_extent = Var(
                self.flowsheet().time,
                self.config.reaction_package.rate_reaction_idx,
                domain=Reals,
                initialize=0.0,
                doc="Extent of kinetic reactions",
                units=rxn_flow_units,
            )  # use reaction package flow basis

            @self.Constraint(
                self.flowsheet().time,
                pc_set,
                doc="Kinetic reaction stoichiometry constraint",
            )
            def rate_reaction_stoichiometry_constraint(b, t, p, j):
                if (p, j) in pc_set:
                    rparam = rblock[t].params
                    return b.rate_reaction_generation[t, p, j] == (
                        sum(
                            rparam.rate_reaction_stoichiometry[r, p, j]
                            * b.rate_reaction_extent[t, r]
                            for r in b.config.reaction_package.rate_reaction_idx
                        )
                    )
                else:
                    return Constraint.Skip

        if has_equilibrium_reactions:
            # Add extents of reaction and stoichiometric constraints
            self.equilibrium_reaction_extent = Var(
                self.flowsheet().time,
                self.config.reaction_package.equilibrium_reaction_idx,
                domain=Reals,
                initialize=0.0,
                doc="Extent of equilibrium reactions",
                units=rxn_flow_units,
            )  # use reaction package flow basis

            @self.Constraint(
                self.flowsheet().time, pc_set, doc="Equilibrium reaction stoichiometry"
            )
            def equilibrium_reaction_stoichiometry_constraint(b, t, p, j):
                if (p, j) in pc_set:
                    return b.equilibrium_reaction_generation[t, p, j] == (
                        sum(
                            rblock[t].params.equilibrium_reaction_stoichiometry[r, p, j]
                            * b.equilibrium_reaction_extent[t, r]
                            for r in b.config.reaction_package.equilibrium_reaction_idx
                        )
                    )
                else:
                    return Constraint.Skip

        if self.properties_out.include_inherent_reactions:
            # Add extents of reaction and stoichiometric constraints
            self.inherent_reaction_extent = Var(
                self.flowsheet().time,
                self.config.property_package.inherent_reaction_idx,
                domain=Reals,
                initialize=0.0,
                doc="Extent of inherent reactions",
                units=flow_units,
            )  # use property package flow basis

            @self.Constraint(
                self.flowsheet().time, pc_set, doc="Inherent reaction stoichiometry"
            )
            def inherent_reaction_stoichiometry_constraint(b, t, p, j):
                if (p, j) in pc_set:
                    return b.inherent_reaction_generation[t, p, j] == (
                        sum(
                            b.properties_out[t].params.inherent_reaction_stoichiometry[
                                r, p, j
                            ]
                            * b.inherent_reaction_extent[t, r]
                            for r in b.config.property_package.inherent_reaction_idx
                        )
                    )
                else:
                    return Constraint.Skip

        # Add custom terms and material balances
        if balance_type == MaterialBalanceType.componentPhase:

            def user_term_mol(b, t, p, j):
                flow_basis = b.properties_out[t].get_material_flow_basis()
                if flow_basis == MaterialFlowBasis.molar:
                    return custom_molar_term(t, p, j)
                elif flow_basis == MaterialFlowBasis.mass:
                    try:
                        return (
                            custom_molar_term(t, p, j) * b.properties_out[t].mw_comp[j]
                        )
                    except AttributeError:
                        raise PropertyNotSupportedError(
                            "{} property package does not support "
                            "molecular weight (mw), which is required for "
                            "using custom terms in material balances.".format(self.name)
                        )
                else:
                    raise ConfigurationError(
                        "{} contained a custom_molar_term argument, but "
                        "the property package used an undefined basis "
                        "(MaterialFlowBasis.other). Custom terms can "
                        "only be used when the property package declares "
                        "a molar or mass flow basis.".format(self.name)
                    )

            def user_term_mass(b, t, p, j):
                flow_basis = b.properties_out[t].get_material_flow_basis()
                if flow_basis == MaterialFlowBasis.mass:
                    return custom_mass_term(t, p, j)
                elif flow_basis == MaterialFlowBasis.molar:
                    try:
                        return (
                            custom_mass_term(t, p, j) / b.properties_out[t].mw_comp[j]
                        )
                    except AttributeError:
                        raise PropertyNotSupportedError(
                            "{} property package does not support "
                            "molecular weight (mw), which is required for "
                            "using custom terms in material balances.".format(self.name)
                        )
                else:
                    raise ConfigurationError(
                        "{} contained a custom_mass_term argument, but "
                        "the property package used an undefined basis "
                        "(MaterialFlowBasis.other). Custom terms can "
                        "only be used when the property package declares "
                        "a molar or mass flow basis.".format(self.name)
                    )

            @self.Constraint(self.flowsheet().time, pc_set, doc="Material balances")
            def material_balances(b, t, p, j):
                if (p, j) in pc_set:
                    rhs = b.properties_in[t].get_material_flow_terms(
                        p, j
                    ) - b.properties_out[t].get_material_flow_terms(p, j)

                    if has_rate_reactions:
                        rhs += b.rate_reaction_generation[t, p, j] * b._rxn_rate_conv(
                            t, j
                        )

                    if has_equilibrium_reactions:
                        rhs += b.equilibrium_reaction_generation[t, p, j]

                    if b.properties_out.include_inherent_reactions:
                        rhs += b.inherent_reaction_generation[t, p, j]

                    if (
                        has_phase_equilibrium
                        and balance_type == MaterialBalanceType.componentPhase
                    ):
                        rhs += phase_equilibrium_term(b, t, p, j)

                    if has_mass_transfer:
                        rhs += b.mass_transfer_term[t, p, j]

                    if custom_molar_term is not None:
                        rhs += user_term_mol(b, t, p, j)

                    if custom_mass_term is not None:
                        rhs += user_term_mass(b, t, p, j)

                    return accumulation_term(b, t, p, j) == rhs

                else:
                    return Constraint.Skip

        elif balance_type == MaterialBalanceType.componentTotal:

            def user_term_mol(b, t, j):
                flow_basis = b.properties_out[t].get_material_flow_basis()
                if flow_basis == MaterialFlowBasis.molar:
                    return custom_molar_term(t, j)
                elif flow_basis == MaterialFlowBasis.mass:
                    try:
                        return custom_molar_term(t, j) * b.properties_out[t].mw_comp[j]
                    except AttributeError:
                        raise PropertyNotSupportedError(
                            "{} property package does not support "
                            "molecular weight (mw), which is required for "
                            "using custom terms in material balances.".format(self.name)
                        )
                else:
                    raise ConfigurationError(
                        "{} contained a custom_molar_term argument, but "
                        "the property package used an undefined basis "
                        "(MaterialFlowBasis.other). Custom terms can "
                        "only be used when the property package declares "
                        "a molar or mass flow basis.".format(self.name)
                    )

            def user_term_mass(b, t, j):
                flow_basis = b.properties_out[t].get_material_flow_basis()
                if flow_basis == MaterialFlowBasis.mass:
                    return custom_mass_term(t, j)
                elif flow_basis == MaterialFlowBasis.molar:
                    try:
                        return custom_mass_term(t, j) / b.properties_out[t].mw_comp[j]
                    except AttributeError:
                        raise PropertyNotSupportedError(
                            "{} property package does not support "
                            "molecular weight (mw), which is required for "
                            "using custom terms in material balances.".format(self.name)
                        )
                else:
                    raise ConfigurationError(
                        "{} contained a custom_mass_term argument, but "
                        "the property package used an undefined basis "
                        "(MaterialFlowBasis.other). Custom terms can "
                        "only be used when the property package declares "
                        "a molar or mass flow basis.".format(self.name)
                    )

            @self.Constraint(
                self.flowsheet().time, component_list, doc="Material balances"
            )
            def material_balances(b, t, j):
                cplist = []
                for p in phase_list:
                    if (p, j) in pc_set:
                        cplist.append(p)

                rhs = sum(
                    b.properties_in[t].get_material_flow_terms(p, j) for p in cplist
                ) - sum(
                    b.properties_out[t].get_material_flow_terms(p, j) for p in cplist
                )

                if has_rate_reactions:
                    rhs += sum(
                        b.rate_reaction_generation[t, p, j] for p in cplist
                    ) * b._rxn_rate_conv(t, j)

                if has_equilibrium_reactions:
                    rhs += sum(
                        b.equilibrium_reaction_generation[t, p, j] for p in cplist
                    )

                if b.properties_out.include_inherent_reactions:
                    rhs += sum(b.inherent_reaction_generation[t, p, j] for p in cplist)

                if has_mass_transfer:
                    rhs += sum(b.mass_transfer_term[t, p, j] for p in cplist)

                if custom_molar_term is not None:
                    rhs += user_term_mol(b, t, j)

                if custom_mass_term is not None:
                    rhs += user_term_mass(b, t, j)

                return sum(accumulation_term(b, t, p, j) for p in cplist) == rhs

        else:
            raise BurntToast()

        return self.material_balances

    def add_phase_component_balances(
        self,
        has_rate_reactions=False,
        has_equilibrium_reactions=False,
        has_phase_equilibrium=False,
        has_mass_transfer=False,
        custom_molar_term=None,
        custom_mass_term=None,
    ):
        """
        This method constructs a set of 0D material balances indexed by time,
        phase and component.

        Args:
            has_rate_reactions: whether default generation terms for rate
                reactions should be included in material balances
            has_equilibrium_reactions: whether generation terms should for
                chemical equilibrium reactions should be included in
                material balances
            has_phase_equilibrium: whether generation terms should for phase
                equilibrium behaviour should be included in material
                balances
            has_mass_transfer: whether generic mass transfer terms should be
                included in material balances
            custom_molar_term: a Pyomo Expression representing custom terms to
                be included in material balances on a molar basis.
                Expression must be indexed by time, phase list and component list
            custom_mass_term: a Pyomo Expression representing custom terms to
                be included in material balances on a mass basis.
                Expression must be indexed by time, phase list and component list

        Returns:
            Constraint object representing material balances
        """
        self._add_material_balance_common(
            balance_type=MaterialBalanceType.componentPhase,
            has_rate_reactions=has_rate_reactions,
            has_equilibrium_reactions=has_equilibrium_reactions,
            has_phase_equilibrium=has_phase_equilibrium,
            has_mass_transfer=has_mass_transfer,
            custom_molar_term=custom_molar_term,
            custom_mass_term=custom_mass_term,
        )

        return self.material_balances

    def add_total_component_balances(
        self,
        has_rate_reactions=False,
        has_equilibrium_reactions=False,
        has_phase_equilibrium=False,
        has_mass_transfer=False,
        custom_molar_term=None,
        custom_mass_term=None,
    ):
        """
        This method constructs a set of 0D material balances indexed by time
        and component.

        Args:
            has_rate_reactions: whether default generation terms for rate
                reactions should be included in material balances
            has_equilibrium_reactions: whether generation terms should for
                chemical equilibrium reactions should be included in
                material balances
            has_phase_equilibrium: whether generation terms should for phase
                equilibrium behaviour should be included in material balances
            has_mass_transfer: whether generic mass transfer terms should be
                included in material balances
            custom_molar_term: a Pyomo Expression representing custom terms to
                be included in material balances on a molar basis.
                Expression must be indexed by time, phase list and component list
            custom_mass_term: a Pyomo Expression representing custom terms to
                be included in material balances on a mass basis.
                Expression must be indexed by time, phase list and component list

        Returns:
            Constraint object representing material balances
        """
        self._add_material_balance_common(
            balance_type=MaterialBalanceType.componentTotal,
            has_rate_reactions=has_rate_reactions,
            has_equilibrium_reactions=has_equilibrium_reactions,
            has_phase_equilibrium=has_phase_equilibrium,
            has_mass_transfer=has_mass_transfer,
            custom_molar_term=custom_molar_term,
            custom_mass_term=custom_mass_term,
        )

        return self.material_balances

    def add_total_element_balances(
        self,
        has_rate_reactions=False,
        has_equilibrium_reactions=False,
        has_phase_equilibrium=False,
        has_mass_transfer=False,
        custom_elemental_term=None,
    ):
        """
        This method constructs a set of 0D element balances indexed by time.

        Args:
            has_rate_reactions: whether default generation terms for rate
                reactions should be included in material balances
            has_equilibrium_reactions: whether generation terms should for
                chemical equilibrium reactions should be included in
                material balances
            has_phase_equilibrium: whether generation terms should for phase
                equilibrium behaviour should be included in material
                balances
            has_mass_transfer: whether generic mass transfer terms should be
                included in material balances
            custom_elemental_term: a Pyomo Expression representing custom
                terms to be included in material balances on a molar
                elemental basis. Expression must be indexed by time and
                element list

        Returns:
            Constraint object representing material balances
        """
        # Get dynamic and holdup flags from config block
        dynamic = self.config.dynamic
        has_holdup = self.config.has_holdup

        component_list = self.properties_in.component_list
        phase_list = self.properties_in.phase_list
        phase_component_set = self.properties_in.phase_component_set

        # Check that property package supports element balances
        if not hasattr(self.config.property_package, "element_list"):
            raise PropertyNotSupportedError(
                "{} property package provided does not contain a list of "
                "elements (element_list), and thus does not support "
                "elemental material balances. Please choose another type "
                "of material balance or a property package which supports "
                "elemental balances."
            )
        # Check for valid arguments to write total elemental balance
        if has_rate_reactions:
            raise ConfigurationError(
                "{} add_total_element_balances method provided with "
                "argument has_rate_reactions = True. Total element "
                "balances do not support rate based reactions, "
                "please correct your configuration arguments".format(self.name)
            )

        if has_equilibrium_reactions:
            raise ConfigurationError(
                "{} add_total_element_balances method provided with "
                "argument has_equilibrium_reactions = True. Total element "
                "balances do not support equilibrium based reactions, "
                "please correct your configuration arguments".format(self.name)
            )

        if has_phase_equilibrium:
            raise ConfigurationError(
                "{} add_total_element_balances method provided with "
                "argument has_phase_equilibrium = True. Total element "
                "balances do not support equilibrium based reactions, "
                "please correct your configuration arguments".format(self.name)
            )

        # Test for components that must exist prior to calling this method
        if has_holdup:
            if not hasattr(self, "volume"):
                raise ConfigurationError(
                    "{} control volume must have volume defined to have "
                    "holdup terms. Please call the "
                    "add_geometry method before adding balance equations.".format(
                        self.name
                    )
                )

        # Get units from property package
        units = self.config.property_package.get_metadata().get_derived_units

        # Get units for accumulation term if required
        acc_units = None
        if self.config.dynamic:
            f_time_units = self.flowsheet().time_units
            if (f_time_units is None) ^ (units("time") is None):
                raise ConfigurationError(
                    "{} incompatible time unit specification between "
                    "flowsheet and property package. Either both must use "
                    "units, or neither.".format(self.name)
                )

            if f_time_units is None:
                acc_units = None
            else:
                acc_units = units("amount") / f_time_units

        # Identify linearly dependent elements
        # It is possible for there to be linearly dependent element balances
        # e.g. if a single species is the only source of two different elements
        linearly_dependent = []

        # Get a representative time point
        rtime = self.flowsheet().time.first()

        # For each component in the material, search for elements which are
        # unique to it
        for i in component_list:
            unique_elements = []
            for e in self.config.property_package.element_list:
                if self.properties_out[rtime].params.element_comp[i][e] != 0:
                    # Assume unique until shown otherwise
                    unique = True

                    for j in component_list:
                        if j == i:
                            continue

                        # If element appears in any other component, not unique
                        if self.properties_out[rtime].params.element_comp[j][e] != 0:
                            unique = False

                    if unique:
                        unique_elements.append(e)

            # If more than 1 unique element, they are linearly dependent
            if len(unique_elements) > 1:
                # Add all but the first to the list of linearly dependent
                linearly_dependent.extend(unique_elements[1:])

        # Set indexing set for element balances
        if len(linearly_dependent) == 0:
            # No linearly depednet equations, so use full element list
            e_index = self.config.property_package.element_list
        else:
            # Otherwise, use only non-dependent elements, and log a message
            _log.info_low(
                "{} detected linearly dependent element balance "
                "equations. Element balances will NOT be written "
                "for the following elements: {}".format(self.name, linearly_dependent)
            )
            e_index = self.config.property_package.element_list - linearly_dependent

        # Add Material Balance terms
        if has_holdup:
            self.element_holdup = Var(
                self.flowsheet().time,
                self.config.property_package.element_list,
                domain=Reals,
                initialize=1.0,
                doc="Elemental holdup in control volume",
                units=units("amount"),
            )

        if dynamic:
            self.element_accumulation = DerivativeVar(
                self.element_holdup,
                wrt=self.flowsheet().time,
                doc="Elemental accumulation in control volume",
                units=acc_units,
            )

        # Method to convert mass flow basis to mole flow basis
        def conv_factor(b, t, j):
            flow_basis = b.properties_out[t].get_material_flow_basis()
            if flow_basis == MaterialFlowBasis.molar:
                return 1
            elif flow_basis == MaterialFlowBasis.mass:
                return 1 / b.properties_out[t].mw_comp[j]
            else:
                raise BalanceTypeNotSupportedError(
                    "{} property package MaterialFlowBasis == 'other'. Cannot "
                    "automatically generate elemental balances.".format(self.name)
                )

        @self.Expression(
            self.flowsheet().time,
            phase_list,
            self.config.property_package.element_list,
            doc="Inlet elemental flow terms",
        )
        def elemental_flow_in(b, t, p, e):
            return sum(
                conv_factor(b, t, j)
                * b.properties_in[t].get_material_flow_terms(p, j)
                * b.properties_out[t].params.element_comp[j][e]
                for j in component_list
            )

        @self.Expression(
            self.flowsheet().time,
            phase_list,
            self.config.property_package.element_list,
            doc="Outlet elemental flow terms",
        )
        def elemental_flow_out(b, t, p, e):
            return sum(
                conv_factor(b, t, j)
                * b.properties_out[t].get_material_flow_terms(p, j)
                * b.properties_out[t].params.element_comp[j][e]
                for j in component_list
            )

        # Create material balance terms as needed
        if has_mass_transfer:
            self.elemental_mass_transfer_term = Var(
                self.flowsheet().time,
                e_index,
                domain=Reals,
                initialize=0.0,
                doc="Element material transfer into unit",
                units=units("flow_mole"),
            )

        # Create rules to substitute material balance terms
        # Accumulation term
        def accumulation_term(b, t, e):
            return (
                pyunits.convert(
                    b.element_accumulation[t, e], to_units=units("flow_mole")
                )
                if dynamic
                else 0
            )

        # Element balances
        @self.Constraint(
            self.flowsheet().time, e_index, doc="Elemental material balances"
        )
        def element_balances(b, t, e):
            rhs = sum(b.elemental_flow_in[t, p, e] for p in phase_list) - sum(
                b.elemental_flow_out[t, p, e] for p in phase_list
            )

            if has_mass_transfer:
                rhs += b.elemental_mass_transfer_term[t, e]

            if custom_elemental_term is not None:
                rhs += custom_elemental_term(t, e)

            return accumulation_term(b, t, e) == rhs

        # Elemental Holdup
        if has_holdup:
            if not hasattr(self, "phase_fraction"):
                self._add_phase_fractions()

            @self.Constraint(
                self.flowsheet().time,
                self.config.property_package.element_list,
                doc="Elemental holdup calculation",
            )
            def elemental_holdup_calculation(b, t, e):
                return b.element_holdup[t, e] == (
                    b.volume[t]
                    * sum(
                        conv_factor(b, t, j)
                        * b.phase_fraction[t, p]
                        * b.properties_out[t].get_material_density_terms(p, j)
                        * b.properties_out[t].params.element_comp[j][e]
                        for p, j in phase_component_set
                    )
                )

        return self.element_balances

    def add_total_material_balances(self, *args, **kwargs):
        """Not Supported"""
        raise BalanceTypeNotSupportedError(
            "{} OD control volumes do not support "
            "add_total_material_balances (yet).".format(self.name)
        )

    def add_total_enthalpy_balances(
        self,
        has_heat_of_reaction=False,
        has_heat_transfer=False,
        has_work_transfer=False,
        has_enthalpy_transfer=False,
        custom_term=None,
    ):
        """
        This method constructs a set of 0D enthalpy balances indexed by time
        and phase.

        Args:
            has_heat_of_reaction: whether terms for heat of reaction should
                be included in enthalpy balance
            has_heat_transfer: whether terms for heat transfer should be
                included in enthalpy balances
            has_work_transfer: whether terms for work transfer should be
                included in enthalpy balances
            has_enthalpy_transfer: whether terms for enthalpy transfer due to
                mass transfer should be included in enthalpy balance. This
                should generally be the same as the has_mass_transfer
                argument in the material balance methods
            custom_term: a Python method which returns Pyomo expressions representing
                custom terms to be included in enthalpy balances.
                Method should accept time and phase list as arguments.

        Returns:
            Constraint object representing enthalpy balances
        """
        # Get dynamic and holdup flags from config block
        dynamic = self.config.dynamic
        has_holdup = self.config.has_holdup

        phase_list = self.properties_in.phase_list

        # Test for components that must exist prior to calling this method
        if has_holdup:
            if not hasattr(self, "volume"):
                raise ConfigurationError(
                    "{} control volume must have volume defined to have "
                    "holdup terms. Please call the "
                    "add_geometry method before adding balance equations.".format(
                        self.name
                    )
                )
        if has_heat_of_reaction:
            if not (
                hasattr(self, "rate_reaction_extent")
                or hasattr(self, "equilibrium_reaction_extent")
            ):
                raise ConfigurationError(
                    "{} extent of reaction terms must exist in order to "
                    "have heat of reaction terms. Please ensure that "
                    "add_material_balance (or equivalent) is called before"
                    " adding energy balances.".format(self.name)
                )

        # Get units from property package
        units = self.config.property_package.get_metadata().get_derived_units

        # Get units for accumulation term if required
        acc_units = None
        if self.config.dynamic:
            f_time_units = self.flowsheet().time_units
            if (f_time_units is None) ^ (units("time") is None):
                raise ConfigurationError(
                    "{} incompatible time unit specification between "
                    "flowsheet and property package. Either both must use "
                    "units, or neither.".format(self.name)
                )

            if f_time_units is None:
                acc_units = None
            else:
                acc_units = units("energy") / f_time_units

        # Create variables
        if has_holdup:
            self.energy_holdup = Var(
                self.flowsheet().time,
                phase_list,
                domain=Reals,
                initialize=1.0,
                doc="Energy holdup in control volume",
                units=units("energy"),
            )

        if dynamic is True:
            self.energy_accumulation = DerivativeVar(
                self.energy_holdup,
                wrt=self.flowsheet().time,
                doc="Energy accumulation in control volume",
                units=acc_units,
            )

        # Create energy balance terms as needed
        # Heat transfer term
        if has_heat_transfer:
            self.heat = Var(
                self.flowsheet().time,
                domain=Reals,
                initialize=0.0,
                doc="Heat transferred into control volume",
                units=units("power"),
            )

        # Work transfer
        if has_work_transfer:
            self.work = Var(
                self.flowsheet().time,
                domain=Reals,
                initialize=0.0,
                doc="Work transferred into control volume",
                units=units("power"),
            )

        # Enthalpy transfer
        if has_enthalpy_transfer:
            self.enthalpy_transfer = Var(
                self.flowsheet().time,
                domain=Reals,
                initialize=0.0,
                doc="Enthalpy transferred into control volume due to mass transfer",
                units=units("power"),
            )

        # Heat of Reaction
        if has_heat_of_reaction:

            @self.Expression(self.flowsheet().time, doc="Heat of reaction term")
            def heat_of_reaction(b, t):
                if hasattr(self, "rate_reaction_extent"):
                    rate_heat = -sum(
                        b.rate_reaction_extent[t, r] * b.reactions[t].dh_rxn[r]
                        for r in self.config.reaction_package.rate_reaction_idx
                    )
                else:
                    rate_heat = 0

                if hasattr(self, "equilibrium_reaction_extent"):
                    equil_heat = -sum(
                        b.equilibrium_reaction_extent[t, e] * b.reactions[t].dh_rxn[e]
                        for e in self.config.reaction_package.equilibrium_reaction_idx
                    )
                else:
                    equil_heat = 0

                return rate_heat + equil_heat

        # Create rules to substitute energy balance terms
        # Accumulation term
        def accumulation_term(b, t, p):
            return (
                pyunits.convert(b.energy_accumulation[t, p], to_units=units("power"))
                if dynamic
                else 0
            )

        # Energy balance equation
        @self.Constraint(self.flowsheet().time, doc="Energy balances")
        def enthalpy_balances(b, t):
            rhs = sum(
                b.properties_in[t].get_enthalpy_flow_terms(p) for p in phase_list
            ) - sum(b.properties_out[t].get_enthalpy_flow_terms(p) for p in phase_list)

            if has_heat_transfer:
                rhs += b.heat[t]

            if has_work_transfer:
                rhs += b.work[t]

            if has_enthalpy_transfer:
                rhs += b.enthalpy_transfer[t]

            if has_heat_of_reaction:
                rhs += b.heat_of_reaction[t]

            if custom_term is not None:
                rhs += custom_term(t)

            return sum(accumulation_term(b, t, p) for p in phase_list) == rhs

        # Energy Holdup
        if has_holdup:
            if not hasattr(self, "phase_fraction"):
                self._add_phase_fractions()

            @self.Constraint(
                self.flowsheet().time, phase_list, doc="Enthalpy holdup constraint"
            )
            def energy_holdup_calculation(b, t, p):
                return b.energy_holdup[t, p] == (
                    b.volume[t]
                    * self.phase_fraction[t, p]
                    * b.properties_out[t].get_energy_density_terms(p)
                )

        return self.enthalpy_balances

    def add_phase_enthalpy_balances(self, *args, **kwargs):
        """Not Supported"""
        raise BalanceTypeNotSupportedError(
            "{} OD control volumes do not support "
            "add_phase_enthalpy_balances.".format(self.name)
        )

    def add_phase_energy_balances(self, *args, **kwargs):
        """Not Supported"""
        raise BalanceTypeNotSupportedError(
            "{} OD control volumes do not support "
            "add_phase_energy_balances.".format(self.name)
        )

    def add_total_energy_balances(self, *args, **kwargs):
        """Not Supported"""
        raise BalanceTypeNotSupportedError(
            "{} OD control volumes do not support "
            "add_total_energy_balances.".format(self.name)
        )

    def add_isothermal_constraint(self, *args, **kwargs):
        """
        Requires ExtendedControlVolume0D
        """
        raise BalanceTypeNotSupportedError(
            f"{self.name} ControlVolume0D does not support isothermal energy balances. "
            "Please consider using ExtendedControlVolume0D in your model if you require "
            "support for isothermal balances."
        )

    def add_total_pressure_balances(self, has_pressure_change=False, custom_term=None):
        """
        This method constructs a set of 0D pressure balances indexed by time.

        Args:
            has_pressure_change - whether terms for pressure change should be
                    included in enthalpy balances
            custom_term - a Python method which returns Pyomo expressions representing
                    custom terms to be included in enthalpy balances.
                    Method should accept time as an arguments.

        Returns:
            Constraint object representing pressure balances
        """
        # Get units from property package
        units = self.config.property_package.get_metadata().get_derived_units

        # Add Momentum Balance Variables as necessary
        if has_pressure_change:
            self.deltaP = Var(
                self.flowsheet().time,
                domain=Reals,
                initialize=0.0,
                doc="Pressure difference across unit",
                units=units("pressure"),
            )

        # Momentum balance equation
        @self.Constraint(self.flowsheet().time, doc="Momentum balance")
        def pressure_balance(b, t):
            rhs = b.properties_in[t].pressure - b.properties_out[t].pressure

            if has_pressure_change:
                rhs += b.deltaP[t]

            if custom_term is not None:
                rhs += custom_term(t)

            return 0 == rhs

        return self.pressure_balance

    def add_phase_pressure_balances(self, *args, **kwargs):
        """Not Supported"""
        raise BalanceTypeNotSupportedError(
            "{} OD control volumes do not support "
            "add_phase_pressure_balances.".format(self.name)
        )

    def add_phase_momentum_balances(self, *args, **kwargs):
        """Not Supported"""
        raise BalanceTypeNotSupportedError(
            "{} OD control volumes do not support "
            "add_phase_momentum_balances.".format(self.name)
        )

    def add_total_momentum_balances(self, *args, **kwargs):
        """Not Supported"""
        raise BalanceTypeNotSupportedError(
            "{} OD control volumes do not support "
            "add_total_momentum_balances.".format(self.name)
        )

    def model_check(blk):
        """
        This method executes the model_check methods on the associated state
        blocks (if they exist). This method is generally called by a unit model
        as part of the unit's model_check method.

        Args:
            None

        Returns:
            None
        """
        # Try property block model check
        for t in blk.flowsheet().time:
            try:
                blk.properties_in[t].model_check()
            except AttributeError:
                _log.warning(
                    "{} ControlVolume inlet property block has no "
                    "model checks. To correct this, add a model_check"
                    " method to the associated StateBlock class.".format(blk.name)
                )
            try:
                blk.properties_out[t].model_check()
            except AttributeError:
                _log.warning(
                    "{} ControlVolume outlet property block has no "
                    "model checks. To correct this, add a "
                    "model_check method to the associated "
                    "StateBlock class.".format(blk.name)
                )

            try:
                blk.reactions[t].model_check()
            except AttributeError:
                _log.warning(
                    "{} ControlVolume outlet reaction block has no "
                    "model check. To correct this, add a "
                    "model_check method to the associated "
                    "ReactionBlock class.".format(blk.name)
                )

    def estimate_outlet_state(self, always_estimate=False):
        for t in self.flowsheet().time:
            self._estimate_next_state(
                self.properties_in[t],
                self.properties_out[t],
                index=t,
                always_estimate=always_estimate,
            )

    def initialize(
        blk,
        state_args=None,
        outlvl=idaeslog.NOTSET,
        optarg=None,
        solver=None,
        hold_state=True,
    ):
        """
        Initialization routine for 0D control volume.

        Keyword Arguments:
            state_args : a dict of arguments to be passed to the property
                         package(s) to provide an initial state for
                         initialization (see documentation of the specific
                         property package) (default = {}).
            outlvl : sets output log level of initialization routine
            optarg : solver options dictionary object (default=None, use
                     default solver options)
            solver : str indicating which solver to use during
                     initialization (default = None)
            hold_state : flag indicating whether the initialization routine
                     should unfix any state variables fixed during
                     initialization, **default** - True. **Valid values:**
                     **True** - states variables are not unfixed, and a dict of
                     returned containing flags for which states were fixed
                     during initialization, **False** - state variables are
                     unfixed after initialization by calling the release_state
                     method.

        Returns:
            If hold_states is True, returns a dict containing flags for which
            states were fixed during initialization.
        """
        # Get inlet state if not provided
        init_log = idaeslog.getInitLogger(blk.name, outlvl, tag="control_volume")

        # Initialize state blocks
        in_flags = blk.properties_in.initialize(
            outlvl=outlvl,
            optarg=optarg,
            solver=solver,
            hold_state=hold_state,
            state_args=state_args,
        )

        if state_args is None:
            # If no initial guesses provided, estimate values for states
            blk.estimate_outlet_state(always_estimate=True)

        out_flags = blk.properties_out.initialize(
            outlvl=outlvl,
            optarg=optarg,
            solver=solver,
            hold_state=True,
            state_args=state_args,
        )
        try:
            # TODO: setting state_vars_fixed may not work for heterogeneous
            # systems where a second control volume is involved, as we cannot
            # assume those state vars are also fixed. For now, heterogeneous
            # reactions should ignore the state_vars_fixed argument and always
            # check their state_vars.
            blk.reactions.initialize(
                outlvl=outlvl,
                optarg=optarg,
                solver=solver,
                state_vars_fixed=True,
            )
        except AttributeError:
            pass

        # Unfix outlet properties
        blk.properties_out.release_state(
            flags=out_flags,
            outlvl=outlvl,
        )
        init_log.info("Initialization Complete")
        return in_flags

    def release_state(blk, flags, outlvl=idaeslog.NOTSET):
        """
        Method to release state variables fixed during initialization.

        Keyword Arguments:
            flags : dict containing information of which state variables
                    were fixed during initialization, and should now be
                    unfixed. This dict is returned by initialize if
                    hold_state = True.
            outlvl : sets output level of logging

        Returns:
            None
        """
        blk.properties_in.release_state(flags, outlvl=outlvl)

    def _add_phase_fractions(self):
        """
        This method constructs the phase_fraction variables for the control
        volume, and the associated constraint on the sum of phase_fractions
        == 1. For systems with only one phase, phase_fraction is created as a
        Pyomo Expression with a value of 1.

        Args:
            None

        Returns:
            None
        """
        phase_list = self.properties_in.phase_list
        if len(phase_list) > 1:
            self.phase_fraction = Var(
                self.flowsheet().time,
                phase_list,
                initialize=1 / len(phase_list),
                doc="Volume fraction of holdup by phase",
            )

            @self.Constraint(self.flowsheet().time, doc="Sum of phase fractions == 1")
            def sum_of_phase_fractions(self, t):
                return 1 == sum(self.phase_fraction[t, p] for p in phase_list)

        else:

            @self.Expression(
                self.flowsheet().time,
                phase_list,
                doc="Volume fraction of holdup by phase",
            )
            def phase_fraction(self, t, p):
                return 1

    def _rxn_rate_conv(b, t, j):
        """
        Wrapper method for the _rxn_rate_conv method to hide the x argument
        required for 1D control volumes.
        """
        # Call the method in control_volume_base with x=None
        return super()._rxn_rate_conv(t, None, j)

    def _get_performance_contents(self, time_point=0):
        """
        Collect all CV variables which are present to report.
        """
        var_dict = {}
        expr_dict = {}
        param_dict = {}

        phase_component_set = self.properties_in.phase_component_set
        phase_list = self.properties_in.phase_list

        time_only_vars = {
            "volume": "Volume",
            "heat": "Heat Transfer",
            "work": "Work Transfer",
            "deltaP": "Pressure Change",
        }

        for v, n in time_only_vars.items():
            try:
                var_dict[n] = getattr(self, v)[time_point]
            except AttributeError:
                pass

        p_vars = {
            "phase_fraction": "Phase Fraction",
            "energy_holdup": "Energy Holdup",
            "energy_accumulation": "Energy Accumulation",
        }

        for v, n in p_vars.items():
            try:
                var_obj = getattr(self, v)
                for p in phase_list:
                    var_dict[f"{n} [{p}]"] = var_obj[time_point, p]
            except AttributeError:
                pass

        pc_vars = {
            "material_holdup": "Material Holdup",
            "material_accumulation": "Material Accumulation",
            "rate_reaction_generation": "Rate Reaction Generation",
            "equilibrium_reaction_generation": "Equilibrium Reaction Generation",
            "mass_transfer_term": "Mass Transfer Term",
        }

        for v, n in pc_vars.items():
            try:
                var_obj = getattr(self, v)
                for p, j in phase_component_set:
                    var_dict[f"{n} [{p}, {j}]"] = var_obj[time_point, p, j]
            except AttributeError:
                pass

        if hasattr(self, "rate_reaction_extent"):
            for r in self.config.reaction_package.rate_reaction_idx:
                var_dict[f"Rate Reaction Extent [{r}]"] = self.rate_reaction_extent[
                    time_point, r
                ]
        if hasattr(self, "equilibrium_reaction_extent"):
            for r in self.config.reaction_package.equilibrium_reaction_idx:
                var_dict[f"Equilibrium Reaction Extent [{r}]"] = (
                    self.equilibrium_reaction_extent[time_point, r]
                )
        if hasattr(self, "phase_equilibrium_generation"):
            for r in self.config.property_package.phase_equilibrium_idx:
                var_dict[f"Phase Equilibrium Generation [{r}]"] = (
                    self.phase_equilibrium_generation[time_point, r]
                )

        e_vars = {
            "element_holdup": "Elemental Holdup",
            "element_accumulation": "Elemental Accumulation",
            "elemental_mass_transfer_term": "Elemental Transfer Term",
        }

        for v, n in e_vars.items():
            try:
                var_obj = getattr(self, v)
                for e in self.config.property_package.element_list:
                    var_dict[f"{n} [{e}]"] = var_obj[time_point, e]
            except AttributeError:
                pass

        time_only_exprs = {"heat_of_reaction": "Heat of Reaction Term"}

        for e, n in time_only_exprs.items():
            try:
                expr_dict[n] = getattr(self, e)[time_point]
            except AttributeError:
                pass

        e_exprs = {
            "elemental_flow_in": "Element Flow In",
            "elemental_flow_out": "Element Flow Out",
        }

        for o, n in e_exprs.items():
            try:
                expr_obj = getattr(self, o)
                for p in phase_list:
                    for e in self.config.property_package.element_list:
                        expr_dict[f"{n} [{p}, {e}]"] = expr_obj[time_point, p, e]
            except AttributeError:
                pass

        params = {}

        for p, n in params.items():
            try:
                param_dict[n] = getattr(self, p)
            except AttributeError:
                pass

        return {"vars": var_dict, "exprs": expr_dict, "params": param_dict}

    def _get_stream_table_contents(self, time_point=0):
        """
        Assume unit has standard configuration of 1 inlet and 1 outlet.

        Developers should overload this as appropriate.
        """
        try:
            return create_stream_table_dataframe(
                {"In": self.properties_in, "Out": self.properties_out},
                time_point=time_point,
            )
        except AttributeError:
            return (
                f"Unit model {self.name} does not have the standard Port "
                f"names (inet and outlet). Please contact the unit model "
                f"developer to develop a unit specific stream table."
            )

    def calculate_scaling_factors(self):
        super().calculate_scaling_factors()
        # If the parent component of an indexed component has a scale factor,
        # but some of the data objects don't, propagate the indexed component
        # scale factor to the missing scaling factors.
        iscale.propagate_indexed_component_scaling_factors(self)

        phase_list = self.properties_in.phase_list
        phase_component_set = self.properties_in.phase_component_set

        # Set scaling for geometry variables
        if hasattr(self, "volume"):
            for t, v in self.volume.items():
                if iscale.get_scaling_factor(v) is None:
                    sf = iscale.get_scaling_factor(
                        self.volume, default=1e-2, warning=True
                    )
                    iscale.set_scaling_factor(v, sf)

        if hasattr(self, "phase_fraction"):
            for v in self.phase_fraction.values():
                if iscale.get_scaling_factor(v) is None:
                    # phase fraction typically between 0.1 and 1
                    iscale.set_scaling_factor(v, 10)

        # Set scaling factors for common material balance variables
        if hasattr(self, "material_holdup"):
            for (t, p, j), v in self.material_holdup.items():
                if iscale.get_scaling_factor(v) is None:
                    sf = iscale.get_scaling_factor(self.volume[t])
                    sf *= iscale.get_scaling_factor(self.phase_fraction[t, p])
                    sf *= iscale.get_scaling_factor(
                        self.properties_out[t].get_material_density_terms(p, j),
                        default=1,
                        warning=True,
                    )
                    iscale.set_scaling_factor(v, sf)

        if hasattr(self, "material_accumulation"):
            for (t, p, j), v in self.material_accumulation.items():
                if iscale.get_scaling_factor(v) is None:
                    sf = iscale.get_scaling_factor(
                        self.properties_out[t].get_material_flow_terms(p, j),
                        default=1,
                        warning=True,
                    )
                    iscale.set_scaling_factor(v, sf)

        # Control Volume has no way of knowing how best to scale
        # reaction extents - this is something only the unit model can provide
        # This also applies to the phase_equilibrium_generation term.

        if hasattr(self, "rate_reaction_generation"):
            for (t, p, j), v in self.rate_reaction_generation.items():
                if iscale.get_scaling_factor(v) is None:
                    sf = iscale.min_scaling_factor(self.rate_reaction_extent[t, :])
                    iscale.set_scaling_factor(v, sf)

        if hasattr(self, "equilibrium_reaction_generation"):
            for (t, p, j), v in self.equilibrium_reaction_generation.items():
                if iscale.get_scaling_factor(v) is None:
                    sf = iscale.min_scaling_factor(
                        self.equilibrium_reaction_extent[t, ...]
                    )
                    iscale.set_scaling_factor(v, sf)

        if hasattr(self, "inherent_reaction_generation"):
            for (t, p, j), v in self.inherent_reaction_generation.items():
                if iscale.get_scaling_factor(v) is None:
                    sf = iscale.min_scaling_factor(
                        self.inherent_reaction_extent[t, ...]
                    )
                    iscale.set_scaling_factor(v, sf)

        if hasattr(self, "mass_transfer_term"):
            for (t, p, j), v in self.mass_transfer_term.items():
                if iscale.get_scaling_factor(v) is None:
                    sf = iscale.get_scaling_factor(
                        self.properties_out[t].get_material_flow_terms(p, j),
                        default=1,
                        warning=True,
                    )
                    iscale.set_scaling_factor(v, sf)

        # Set scaling factors for element balance variables
        if hasattr(self, "elemental_flow_out"):
            for (t, p, e), v in self.elemental_flow_out.items():
                flow_basis = self.properties_out[t].get_material_flow_basis()

                sf = iscale.min_scaling_factor(
                    [
                        self.properties_out[t].get_material_density_terms(p, j)
                        for (p, j) in phase_component_set
                    ],
                    default=1,
                    warning=True,
                )
                if flow_basis == MaterialFlowBasis.molar:
                    sf *= 1
                elif flow_basis == MaterialFlowBasis.mass:
                    # MW scaling factor is the inverse of its value
                    sf *= value(self.properties_out[t].mw_comp[j])

                iscale.set_scaling_factor(v, sf)
                iscale.set_scaling_factor(self.elemental_flow_in[t, p, e], sf)

        if hasattr(self, "element_holdup"):
            for (t, e), v in self.element_holdup.items():
                flow_basis = self.properties_out[t].get_material_flow_basis()
                sf_list = []
                for p, j in phase_component_set:
                    if flow_basis == MaterialFlowBasis.molar:
                        sf = 1
                    elif flow_basis == MaterialFlowBasis.mass:
                        # MW scaling factor is the inverse of its value
                        sf = value(self.properties_out[t].mw_comp[j])
                    sf *= iscale.get_scaling_factor(self.phase_fraction[t, p])
                    sf *= iscale.get_scaling_factor(
                        self.properties_out[t].get_material_density_terms(p, j),
                        default=1,
                        warning=True,
                    )
                    sf *= value(self.properties_out[t].params.element_comp[j][e]) ** -1
                    sf_list.append(sf)
                sf_h = min(sf_list) * iscale.get_scaling_factor(self.volume[t])
                iscale.set_scaling_factor(v, sf_h)

        if hasattr(self, "element_accumulation"):
            for (t, e), v in self.element_accumulation.items():
                if iscale.get_scaling_factor(v) is None:
                    sf = iscale.min_scaling_factor(
                        self.elemental_flow_out[t, ...], default=1, warning=True
                    )
                    iscale.set_scaling_factor(v, sf)

        if hasattr(self, "elemental_mass_transfer_term"):
            for (t, e), v in self.elemental_mass_transfer_term.items():
                # minimum scaling factor for elemental_flow terms
                sf_list = []
                flow_basis = self.properties_out[t].get_material_flow_basis()
                if iscale.get_scaling_factor(v) is None:
                    sf = iscale.min_scaling_factor(
                        self.elemental_flow_out[t, ...], default=1, warning=True
                    )
                    iscale.set_scaling_factor(v, sf)

        # Set scaling factors for enthalpy balance variables
        if hasattr(self, "energy_holdup"):
            for (t, p), v in self.energy_holdup.items():
                if iscale.get_scaling_factor(v) is None:
                    sf = iscale.get_scaling_factor(self.volume[t])
                    sf *= iscale.get_scaling_factor(self.phase_fraction[t, p])
                    sf *= iscale.get_scaling_factor(
                        self.properties_out[t].get_energy_density_terms(p),
                        default=1,
                        warning=True,
                    )
                    iscale.set_scaling_factor(v, sf)

        if hasattr(self, "energy_accumulation"):
            for (t, p), v in self.energy_accumulation.items():
                if iscale.get_scaling_factor(v) is None:
                    sf = iscale.get_scaling_factor(
                        self.properties_out[t].get_enthalpy_flow_terms(p),
                        default=1,
                        warning=True,
                    )
                    iscale.set_scaling_factor(v, sf)

        if hasattr(self, "heat"):
            for v in self.heat.values():
                if iscale.get_scaling_factor(v) is None:
                    sf = iscale.get_scaling_factor(
                        self.heat, default=1e-6, warning=True
                    )
                    iscale.set_scaling_factor(v, sf)

        if hasattr(self, "work"):
            for v in self.work.values():
                if iscale.get_scaling_factor(v) is None:
                    sf = iscale.get_scaling_factor(
                        self.work, default=1e-6, warning=True
                    )
                    iscale.set_scaling_factor(v, sf)

        if hasattr(self, "enthalpy_transfer"):
            for t, v in self.enthalpy_transfer.items():
                if iscale.get_scaling_factor(v) is None:
                    sf = iscale.min_scaling_factor(
                        [
                            self.properties_out[t].get_enthalpy_flow_terms(p)
                            for p in phase_list
                        ]
                    )
                    iscale.set_scaling_factor(v, sf)

        # Set scaling for momentum balance variables
        if hasattr(self, "deltaP"):
            for t, v in self.deltaP.items():
                if iscale.get_scaling_factor(v) is None:
                    sf = 10 * iscale.get_scaling_factor(
                        self.properties_in[t].pressure, default=1, warning=True
                    )
                    iscale.set_scaling_factor(v, sf)

        # Transform constraints in order of appearance
        if hasattr(self, "material_holdup_calculation"):
            for (t, p, j), c in self.material_holdup_calculation.items():
                sf = iscale.get_scaling_factor(self.material_holdup[t, p, j])
                iscale.constraint_scaling_transform(c, sf, overwrite=False)

        if hasattr(self, "rate_reaction_stoichiometry_constraint"):
            for (t, p, j), c in self.rate_reaction_stoichiometry_constraint.items():
                sf = iscale.get_scaling_factor(self.rate_reaction_generation[t, p, j])
                iscale.constraint_scaling_transform(c, sf, overwrite=False)

        if hasattr(self, "equilibrium_reaction_stoichiometry_constraint"):
            for (
                t,
                p,
                j,
            ), c in self.equilibrium_reaction_stoichiometry_constraint.items():
                sf = iscale.get_scaling_factor(
                    self.equilibrium_reaction_generation[t, p, j]
                )
                iscale.constraint_scaling_transform(c, sf, overwrite=False)

        if hasattr(self, "inherent_reaction_stoichiometry_constraint"):
            for (t, p, j), c in self.inherent_reaction_stoichiometry_constraint.items():
                sf = iscale.get_scaling_factor(
                    self.inherent_reaction_generation[t, p, j]
                )
                iscale.constraint_scaling_transform(c, sf, overwrite=False)

        if hasattr(self, "material_balances"):
            mb_type = self._constructed_material_balance_type
            if mb_type == MaterialBalanceType.componentPhase:
                for (t, p, j), c in self.material_balances.items():
                    sf = iscale.get_scaling_factor(
                        self.properties_in[t].get_material_flow_terms(p, j),
                        default=1,
                        warning=True,
                    )
                    iscale.constraint_scaling_transform(c, sf, overwrite=False)
            elif mb_type == MaterialBalanceType.componentTotal:
                for (t, j), c in self.material_balances.items():
                    sf = iscale.min_scaling_factor(
                        [
                            self.properties_in[t].get_material_flow_terms(p, j)
                            for p in phase_list
                            if (p, j) in phase_component_set
                        ]
                    )
                    iscale.constraint_scaling_transform(c, sf, overwrite=False)
            else:
                # There are some other material balance types but they create
                # constraints with different names.
                _log.warning(f"Unknown material balance type {mb_type}")

        if hasattr(self, "element_balances"):
            for (t, e), c in self.element_balances.items():
                sf = iscale.min_scaling_factor(
                    [self.elemental_flow_out[t, p, e] for p in phase_list]
                )
                iscale.constraint_scaling_transform(c, sf, overwrite=False)

        if hasattr(self, "elemental_holdup_calculation"):
            for (t, e), c in self.elemental_holdup_calculation.items():
                sf = iscale.get_scaling_factor(self.element_holdup[t, e])
                iscale.constraint_scaling_transform(c, sf, overwrite=False)

        if hasattr(self, "enthalpy_balances"):
            for t, c in self.enthalpy_balances.items():
                sf = iscale.min_scaling_factor(
                    [
                        self.properties_in[t].get_enthalpy_flow_terms(p)
                        for p in phase_list
                    ],
                    hint="enthalpy_flow_terms",
                )
                if hasattr(self, "work"):
                    sf = min(
                        sf,
                        iscale.get_scaling_factor(
                            self.work[t], default=1, warning=True
                        ),
                    )
                if hasattr(self, "heat"):
                    sf = min(
                        sf,
                        iscale.get_scaling_factor(
                            self.heat[t], default=1, warning=True
                        ),
                    )
                iscale.constraint_scaling_transform(c, sf, overwrite=False)

        if hasattr(self, "energy_holdup_calculation"):
            for (t, p), c in self.energy_holdup_calculation.items():
                sf = iscale.get_scaling_factor(self.energy_holdup[t, p])
                iscale.constraint_scaling_transform(c, sf, overwrite=False)

        if hasattr(self, "pressure_balance"):
            for t, c in self.pressure_balance.items():
                sf = iscale.get_scaling_factor(
                    self.properties_in[t].pressure, default=1, warning=True
                )
                iscale.constraint_scaling_transform(c, sf, overwrite=False)

        if hasattr(self, "sum_of_phase_fractions"):
            for t, c in self.sum_of_phase_fractions.items():
                sf = iscale.min_scaling_factor(
                    [self.phase_fraction[t, p] for p in phase_list]
                )
                iscale.constraint_scaling_transform(c, sf, overwrite=False)

        # Scaling for discretization equations
        if hasattr(self, "material_accumulation_disc_eq"):
            for (t, p, j), c in self.material_accumulation_disc_eq.items():
                sf = iscale.get_scaling_factor(self.material_accumulation[t, p, j])
                iscale.constraint_scaling_transform(c, sf, overwrite=False)

        if hasattr(self, "energy_accumulation_disc_eq"):
            for (t, p), c in self.energy_accumulation_disc_eq.items():
                sf = iscale.get_scaling_factor(self.energy_accumulation[t, p])
                iscale.constraint_scaling_transform(c, sf, overwrite=False)

        if hasattr(self, "element_accumulation_disc_eq"):
            for (t, e), c in self.element_accumulation_disc_eq.items():
                sf = iscale.get_scaling_factor(self.element_accumulation[t, e])
                iscale.constraint_scaling_transform(c, sf, overwrite=False)