Add support for isothermal conditions in control volumes.

docs/reference_guides/core/control_volume_0d.rst

@@ -282,3 +282,31 @@ A single pressure balance is written for the entire mixture.
 .. math:: 0 = s_{pressure} \times P_{in, t} - s_{pressure} \times P_{out, t} + s_{pressure} \times \Delta P_t + s_{pressure} \times \Delta P_{custom, t}
 
 The :math:`\Delta P_{custom, t}` term allows the user to provide custom terms  which will be added into the pressure balance.
+
+
+Extended 0D Control Volume Class
+--------------------------------
+
+The ExtendedControlVolume0DBlock block builds upon ControlVolume0DBlock by adding some new balance options. It is envisioned that this will
+merge with ControlVolume0DBlock, however to ensure backward compatibility these additions have been kept separate until unit models can
+be updated to restrict (or allow) these new options if necessary. The core functionality is the same as for ControlVolume0DBlock, with the
+addition of one extra energy balance type; isothermal.
+
+.. module:: idaes.core.base.extended_control_volume0d
+
+.. autoclass:: ExtendedControlVolume0DBlock
+    :members:
+
+.. autoclass:: ExtendedControlVolume0DBlockData
+    :members:
+
+add_isothermal_constraint
+^^^^^^^^^^^^^^^^^^^^^^^^^
+
+A constraint equating temperature at the inlet and outlet of the control volume is written.
+
+**Constraints**
+
+`enthalpy_balances(t)`:
+
+.. math:: T_{in, t} == T_{out, t}

docs/reference_guides/core/control_volume_1d.rst

@@ -311,3 +311,33 @@ The :math:`\Delta P_{custom, t, x}` term allows the user to provide custom terms
 `pressure_linking_constraint(t, x)`:
 
 This constraint is an internal constraint used to link the pressure terms in the StateBlocks into a single indexed variable. This is required as Pyomo.DAE requires a single indexed variable to create the associated DerivativeVars and their numerical expansions.
+
+
+Extended 1D Control Volume Class
+--------------------------------
+
+The ExtendedControlVolume1DBlock block builds upon ControlVolume1DBlock by adding some new balance options. It is envisioned that this will
+merge with ControlVolume1DBlock, however to ensure backward compatibility these additions have been kept separate until unit models can
+be updated to restrict (or allow) these new options if necessary. The core functionality is the same as for ControlVolume1DBlock, with the
+addition of one extra energy balance type; isothermal.
+
+.. module:: idaes.core.base.extended_control_volume1d
+
+.. autoclass:: ExtendedControlVolume1DBlock
+    :members:
+
+.. autoclass:: ExtendedControlVolume1DBlockData
+    :members:
+
+add_isothermal_constraint
+^^^^^^^^^^^^^^^^^^^^^^^^^
+
+A constraint equating temperature along the length domain of the control volume is written.
+
+**Constraints**
+
+`enthalpy_balances(t)`:
+
+.. math:: T_{t, x-1} == T_{t, x}
+
+This constraint is skipped at the inlet to the control volume.

idaes/core/__init__.py

@@ -33,6 +33,8 @@
 )
 from .base.control_volume0d import ControlVolume0DBlock
 from .base.control_volume1d import ControlVolume1DBlock, DistributedVars
+from .base.extended_control_volume0d import ExtendedControlVolume0DBlock
+from .base.extended_control_volume1d import ExtendedControlVolume1DBlock
 from .base.phases import (
     Phase,
     LiquidPhase,

idaes/core/base/control_volume0d.py

@@ -1352,6 +1352,16 @@ def add_total_energy_balances(self, *args, **kwargs):
             "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.

idaes/core/base/control_volume1d.py

@@ -1737,6 +1737,16 @@ def add_total_energy_balances(self, *args, **kwargs):
             "add_total_energy_balances.".format(self.name)
         )
 
+    def add_isothermal_constraint(self, *args, **kwargs):
+        """
+        Requires ExtendedControlVolume1D
+        """
+        raise BalanceTypeNotSupportedError(
+            f"{self.name} ControlVolume1D does not support isothermal energy balances. "
+            "Please consider using ExtendedControlVolume1D 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 1D pressure balances indexed by time.

idaes/core/base/control_volume_base.py

@@ -71,6 +71,7 @@ class EnergyBalanceType(Enum):
     enthalpyTotal = 2
     energyPhase = 3
     energyTotal = 4
+    isothermal = 5
 
 
 # Enumerate options for momentum balances
@@ -618,6 +619,8 @@ def add_energy_balances(self, balance_type=EnergyBalanceType.useDefault, **kwarg
             eb = self.add_total_energy_balances(**kwargs)
         elif balance_type == EnergyBalanceType.energyPhase:
             eb = self.add_phase_energy_balances(**kwargs)
+        elif balance_type == EnergyBalanceType.isothermal:
+            eb = self.add_isothermal_constraint(**kwargs)
         else:
             raise ConfigurationError(
                 "{} invalid balance_type for add_energy_balances."
@@ -843,6 +846,18 @@ def add_total_energy_balances(self, *args, **kwargs):
             "developer of the ControlVolume class you are using.".format(self.name)
         )
 
+    def add_isothermal_constraint(self, *args, **kwargs):
+        """
+        Method for adding an isothermal constraint to the control volume.
+
+        See specific control volume documentation for details.
+        """
+        raise NotImplementedError(
+            f"{self.name} control volume class has not implemented a method for "
+            "add_isothermal_constraint. Please contact the "
+            "developer of the ControlVolume class you are using."
+        )
+
     def add_phase_pressure_balances(self, *args, **kwargs):
         """
         Method for adding pressure balances indexed by

idaes/core/base/extended_control_volume0d.py

@@ -0,0 +1,106 @@
+#################################################################################
+# 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) 2018-2024 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.
+#################################################################################
+"""
+0D Control Volume class with support for isothermal energy balance.
+"""
+
+__author__ = "Andrew Lee"
+
+# Import IDAES cores
+from idaes.core.base.control_volume0d import ControlVolume0DBlockData
+from idaes.core import declare_process_block_class
+from idaes.core.util.exceptions import ConfigurationError
+
+import idaes.logger as idaeslog
+
+_log = idaeslog.getLogger(__name__)
+
+
+@declare_process_block_class(
+    "ExtendedControlVolume0DBlock",
+    doc="""
+    ExtendedControlVolume0DBlock is an extension of the ControlVolume0D
+    block with support for isothermal conditions in place of a formal
+    energy balance.""",
+)
+class ExtendedControlVolume0DBlockData(ControlVolume0DBlockData):
+    """
+    Extended 0-Dimensional (Non-Discretized) ControlVolume Class
+
+    This class extends the existing ControlVolume0DBlockData class
+    with support for isothermal energy balances.
+    """
+
+    def add_isothermal_constraint(
+        self,
+        has_heat_of_reaction=False,
+        has_heat_transfer=False,
+        has_work_transfer=False,
+        has_enthalpy_transfer=False,
+        custom_term=None,
+    ):
+        """
+        This method constructs an isothermal constraint for the control volume.
+
+        Arguments are supported for compatibility with other forms but must be False
+        or None otherwise an Exception is raised.
+
+        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
+        """
+        if has_heat_transfer:
+            raise ConfigurationError(
+                f"{self.name}: isothermal energy balance option requires that has_heat_transfer is False. "
+                "If you are trying to solve for heat duty to achieve isothermal operation, please use "
+                "a full energy balance and add a constraint to equate inlet and outlet temperatures."
+            )
+        if has_work_transfer:
+            raise ConfigurationError(
+                f"{self.name}: isothermal energy balance option requires that has_work_transfer is False. "
+                "If you are trying to solve for work under isothermal operation, please use "
+                "a full energy balance and add a constraint to equate inlet and outlet temperatures."
+            )
+        if has_enthalpy_transfer:
+            raise ConfigurationError(
+                f"{self.name}: isothermal energy balance option does not support enthalpy transfer."
+            )
+        if has_heat_of_reaction:
+            raise ConfigurationError(
+                f"{self.name}: isothermal energy balance option requires that has_heat_of_reaction is False. "
+                "If you are trying to solve for heat duty to achieve isothermal operation, please use "
+                "a full energy balance and add a constraint to equate inlet and outlet temperatures."
+            )
+        if custom_term is not None:
+            raise ConfigurationError(
+                f"{self.name}: isothermal energy balance option does not support custom terms."
+            )
+
+        # Add isothermal constraint
+        @self.Constraint(self.flowsheet().time, doc="Energy balances")
+        def enthalpy_balances(b, t):
+            return b.properties_in[t].temperature == b.properties_out[t].temperature

idaes/core/base/extended_control_volume1d.py

@@ -0,0 +1,117 @@
+#################################################################################
+# 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) 2018-2024 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.
+#################################################################################
+"""
+1D Control Volume class with support for isothermal energy balance.
+"""
+
+__author__ = "Andrew Lee"
+
+# Import Pyomo libraries
+from pyomo.environ import Constraint
+
+# Import IDAES cores
+from idaes.core.base.control_volume1d import ControlVolume1DBlockData
+from idaes.core import declare_process_block_class
+from idaes.core.util.exceptions import ConfigurationError
+
+import idaes.logger as idaeslog
+
+_log = idaeslog.getLogger(__name__)
+
+
+@declare_process_block_class(
+    "ExtendedControlVolume1DBlock",
+    doc="""
+    ExtendedControlVolume1DBlock is an extension of the ControlVolume1D
+    block with support for isothermal conditions in place of a formal
+    energy balance.""",
+)
+class ExtendedControlVolume1DBlockData(ControlVolume1DBlockData):
+    """
+    Extended 1-Dimensional ControlVolume Class
+
+    This class extends the existing ControlVolume1DBlockData class
+    with support for isothermal energy balances.
+    """
+
+    def add_isothermal_constraint(
+        self,
+        has_heat_of_reaction=False,
+        has_heat_transfer=False,
+        has_work_transfer=False,
+        has_enthalpy_transfer=False,
+        custom_term=None,
+    ):
+        """
+        This method constructs an isothermal constraint for the control volume.
+
+        Arguments are supported for compatibility with other forms but must be False
+        or None otherwise an Exception is raised.
+
+        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
+        """
+        if has_heat_transfer:
+            raise ConfigurationError(
+                f"{self.name}: isothermal energy balance option requires that has_heat_transfer is False. "
+                "If you are trying to solve for heat duty to achieve isothermal operation, please use "
+                "a full energy balance and add a constraint to equate inlet and outlet temperatures."
+            )
+        if has_work_transfer:
+            raise ConfigurationError(
+                f"{self.name}: isothermal energy balance option requires that has_work_transfer is False. "
+                "If you are trying to solve for work under isothermal operation, please use "
+                "a full energy balance and add a constraint to equate inlet and outlet temperatures."
+            )
+        if has_enthalpy_transfer:
+            raise ConfigurationError(
+                f"{self.name}: isothermal energy balance option does not support enthalpy transfer. "
+            )
+        if has_heat_of_reaction:
+            raise ConfigurationError(
+                f"{self.name}: isothermal energy balance option requires that has_heat_of_reaction is False. "
+                "If you are trying to solve for heat duty to achieve isothermal operation, please use "
+                "a full energy balance and add a constraint to equate inlet and outlet temperatures."
+            )
+        if custom_term is not None:
+            raise ConfigurationError(
+                f"{self.name}: isothermal energy balance option does not support custom terms. "
+            )
+
+        # Add isothermal constraint
+        @self.Constraint(
+            self.flowsheet().time, self.length_domain, doc="Energy balances"
+        )
+        def enthalpy_balances(b, t, x):
+            if x == b.length_domain.first():
+                return Constraint.Skip
+
+            return (
+                b.properties[t, b.length_domain.prev(x)].temperature
+                == b.properties[t, x].temperature
+            )

idaes/core/base/tests/test_control_volume_0d.py

@@ -2280,6 +2280,20 @@ def test_add_total_energy_balances():
         m.fs.cv.add_total_energy_balances()
 
 
+@pytest.mark.unit
+def test_add_isothermal_energy_balances():
+    m = ConcreteModel()
+    m.fs = Flowsheet(dynamic=False)
+    m.fs.pp = PhysicalParameterTestBlock()
+
+    m.fs.cv = ControlVolume0DBlock(property_package=m.fs.pp)
+
+    m.fs.cv.add_state_blocks(has_phase_equilibrium=True)
+
+    with pytest.raises(BalanceTypeNotSupportedError):
+        m.fs.cv.add_isothermal_constraint()
+
+
 # -----------------------------------------------------------------------------
 # Test add total pressure balances
 @pytest.mark.unit