diff --git a/docs/technical_reference/unit_models/osmotically_assisted_reverse_osmosis_0D.rst b/docs/technical_reference/unit_models/osmotically_assisted_reverse_osmosis_0D.rst
index 7db9756d88..5b57b90321 100644
--- a/docs/technical_reference/unit_models/osmotically_assisted_reverse_osmosis_0D.rst
+++ b/docs/technical_reference/unit_models/osmotically_assisted_reverse_osmosis_0D.rst
@@ -4,6 +4,7 @@ This osmotically assisted reverse osmosis (OARO) unit model
    * is 0-dimensional
    * supports a single liquid phase only
    * supports steady-state only
+   * supports flat-sheet and spiral-wound module designs
    * is based on the solution-diffusion model and film theory
    * assumes isothermal conditions
    * assumes the feed-side flows in the forward direction
@@ -177,7 +178,8 @@ Equations
    "Reynolds number",":math:`Re = \frac{\rho v_f d_h}{\mu}`"
    "Hydraulic diameter",":math:`d_h = \frac{4\epsilon_{sp}}{2/h_{ch} + (1-\epsilon_{sp})8/h_{ch}}`"
    "Cross-sectional area",":math:`A_c = h_{ch}W\epsilon_{sp}`"
-   "Membrane area",":math:`A_m = LW`"
+   "Membrane area (flat-plate)",":math:`A_m = LW`"
+   "Membrane area (spiral-wound)",":math:`A_m = 2LW`"
    "Pressure drop",":math:`ΔP = (\frac{ΔP}{Δx})_{avg}L`"
    "Feed-channel velocity",":math:`v_f = Q_f/A_c`"
    "Friction factor",":math:`f = 0.42+\frac{189.3}{Re}`"
diff --git a/docs/technical_reference/unit_models/osmotically_assisted_reverse_osmosis_1D.rst b/docs/technical_reference/unit_models/osmotically_assisted_reverse_osmosis_1D.rst
index e6f6d24b5b..b2c3ebdeff 100644
--- a/docs/technical_reference/unit_models/osmotically_assisted_reverse_osmosis_1D.rst
+++ b/docs/technical_reference/unit_models/osmotically_assisted_reverse_osmosis_1D.rst
@@ -4,6 +4,7 @@ This osmotically assisted reverse osmosis (OARO) unit model
    * is 1-dimensional
    * supports a single liquid phase only
    * supports steady-state only
+   * supports flat-sheet and spiral-wound module designs
    * is based on the solution-diffusion model and film theory
    * assumes isothermal conditions
    * assumes the feed-side flows in the forward direction
diff --git a/docs/technical_reference/unit_models/reverse_osmosis_0D.rst b/docs/technical_reference/unit_models/reverse_osmosis_0D.rst
index 01cc0be768..1f8a6328b8 100644
--- a/docs/technical_reference/unit_models/reverse_osmosis_0D.rst
+++ b/docs/technical_reference/unit_models/reverse_osmosis_0D.rst
@@ -4,6 +4,7 @@ This reverse osmosis (RO) unit model
    * is 0-dimensional
    * supports a single liquid phase only
    * supports steady-state only
+   * supports flat-sheet and spiral-wound module designs
    * is based on the solution-diffusion model and film theory
    * assumes isothermal conditions
 
@@ -159,7 +160,8 @@ Equations
    "Reynolds number",":math:`Re = \frac{\rho v_f d_h}{\mu}`"
    "Hydraulic diameter",":math:`d_h = \frac{4\epsilon_{sp}}{2/h_{ch} + (1-\epsilon_{sp})8/h_{ch}}`"
    "Cross-sectional area",":math:`A_c = h_{ch}W\epsilon_{sp}`"
-   "Membrane area",":math:`A_m = LW`"
+   "Membrane area (flat-plate)",":math:`A_m = LW`"
+   "Membrane area (spiral-wound)",":math:`A_m = 2LW`"
    "Pressure drop",":math:`ΔP = (\frac{ΔP}{Δx})_{avg}L`"
    "Feed-channel velocity",":math:`v_f = Q_f/A_c`"
    "Friction factor",":math:`f = 0.42+\frac{189.3}{Re}`"
diff --git a/docs/technical_reference/unit_models/reverse_osmosis_1D.rst b/docs/technical_reference/unit_models/reverse_osmosis_1D.rst
index b0c7f34bfb..49a1396fff 100644
--- a/docs/technical_reference/unit_models/reverse_osmosis_1D.rst
+++ b/docs/technical_reference/unit_models/reverse_osmosis_1D.rst
@@ -4,6 +4,7 @@ This reverse osmosis (RO) unit model
    * is 1-dimensional
    * supports a single liquid phase only
    * supports steady-state only
+   * supports flat-sheet and spiral-wound module designs
    * is based on the solution-diffusion model and film theory
    * assumes isothermal conditions
 
diff --git a/watertap/core/membrane_channel_base.py b/watertap/core/membrane_channel_base.py
index 665932953c..70db4ecfa4 100644
--- a/watertap/core/membrane_channel_base.py
+++ b/watertap/core/membrane_channel_base.py
@@ -71,6 +71,16 @@ class TransportModel(Enum):
     SKK = auto()
 
 
+class ModuleType(Enum):
+    """
+    flat_sheet: flat-sheet module configuration
+    spiral_wound: spiral-wound module configuration
+    """
+
+    flat_sheet = auto()
+    spiral_wound = auto()
+
+
 class PressureChangeType(Enum):
     """
     fixed_per_stage: pressure drop across membrane channel is a user-specified value
@@ -85,12 +95,11 @@ class PressureChangeType(Enum):
 
 class FrictionFactor(Enum):
     """
-    flat_sheet: Darcy's friction factor correlation by Guillen & Hoek
-    spiral_wound: Darcy's friction factor correlation by Schock & Miquel, 1987
+    default_by_module_type: Will revert FrictionFactor to either the Darcy's friction factor correlation
+    by Guillen & Hoek (flat-plate) or by Schock & Miquel (spiral-wound)
     """
 
-    flat_sheet = auto()
-    spiral_wound = auto()
+    default_by_module_type = auto()
 
 
 CONFIG_Template = ConfigDict()
@@ -261,6 +270,24 @@ class FrictionFactor(Enum):
     ),
 )
 
+CONFIG_Template.declare(
+    "module_type",
+    ConfigValue(
+        default=ModuleType.flat_sheet,
+        domain=In(ModuleType),
+        description="Membrane geometry for flat-sheet or spiral-wound",
+        doc="""
+        Options to account for geometry differences between flat sheet and spiral wound membranes.
+
+        **default** - ``ModuleType.flat_sheet``
+
+        "``ModuleType.flat_sheet``", "Module type option for flat-sheet membrane modules"
+        "``ModuleType.spiral_wound``", "Module type option for spiral-wound membrane modules, this option accounts for how membranes in spiral-wound modules are folded which reduces the channel width by half"
+
+        """,
+    ),
+)
+
 CONFIG_Template.declare(
     "has_pressure_change",
     ConfigValue(
@@ -303,19 +330,18 @@ class FrictionFactor(Enum):
 CONFIG_Template.declare(
     "friction_factor",
     ConfigValue(
-        default=FrictionFactor.flat_sheet,
+        default=FrictionFactor.default_by_module_type,
         domain=In(FrictionFactor),
         description="Darcy friction factor correlation",
         doc="""
         Options to account for friction factor correlations.
 
-        **default** - ``FrictionFactor.flat_sheet`` 
+        **default** - ``FrictionFactor.default_by_module_type`` 
 
     .. csv-table::
         :header: "Configuration Options", "Description"
 
-        "``FrictionFactor.flat_sheet``", "Friction factor correlation for flat-sheet membrane modules"
-        "``FrictionFactor.spiral_wound``", "Friction factor correlation for spiral-wound membranes"
+        "``FrictionFactor.default_by_module_type``", "Friction factor correlation that is specific to the supported membrane modules type"
     """,
     ),
 )
@@ -358,7 +384,8 @@ def add_total_pressure_balances(
         has_pressure_change=True,
         pressure_change_type=PressureChangeType.calculated,
         custom_term=None,
-        friction_factor=FrictionFactor.flat_sheet,
+        module_type=ModuleType.flat_sheet,
+        friction_factor=FrictionFactor.default_by_module_type,
     ):
         super().add_total_pressure_balances(
             has_pressure_change=has_pressure_change, custom_term=custom_term
@@ -378,7 +405,9 @@ def eq_equal_pressure_interface(b, t, x):
             self._add_pressure_change(pressure_change_type=pressure_change_type)
 
         if pressure_change_type == PressureChangeType.calculated:
-            self._add_calculated_pressure_change(friction_factor=friction_factor)
+            self._add_calculated_pressure_change(
+                module_type=module_type, friction_factor=friction_factor
+            )
 
     def add_interface_isothermal_conditions(self):
 
@@ -710,7 +739,9 @@ def _add_interface_stateblock(self, has_phase_equilibrium=None):
         )
 
     def _add_calculated_pressure_change(
-        self, friction_factor=FrictionFactor.flat_sheet
+        self,
+        module_type=ModuleType.flat_sheet,
+        friction_factor=FrictionFactor.default_by_module_type,
     ):
         self._add_calculated_pressure_change_mass_transfer_components()
 
@@ -749,32 +780,35 @@ def eq_velocity(b, t, x):
             return b.velocity[t, x] * b.area == b.properties[t, x].flow_vol_phase["Liq"]
 
         ## ==========================================================================
-        # Darcy friction factor based on eq. S27 in SI for Cost Optimization of Osmotically Assisted Reverse Osmosis
-        if friction_factor == FrictionFactor.flat_sheet:
-
-            @self.Constraint(
-                self.flowsheet().config.time,
-                self.length_domain,
-                doc="Darcy friction factor constraint for flat sheet membranes",
-            )
-            def eq_friction_factor(b, t, x):
-                return (b.friction_factor_darcy[t, x] - 0.42) * b.N_Re[t, x] == 189.3
-
-        # Darcy friction factor based on eq. 24 in Mass transfer and pressure loss in spiral wound modules (Schock & Miquel, 1987)
-        elif friction_factor == FrictionFactor.spiral_wound:
-
-            @self.Constraint(
-                self.flowsheet().config.time,
-                self.length_domain,
-                doc="Darcy friction factor constraint for spiral-wound membranes",
-            )
-            def eq_friction_factor(b, t, x):
-                return b.friction_factor_darcy[t, x] == 6.23 * b.N_Re[t, x] ** -0.3
+        if friction_factor == FrictionFactor.default_by_module_type:
+            # Darcy friction factor based on eq. S27 in SI for Cost Optimization of Osmotically Assisted Reverse Osmosis
+            if module_type == ModuleType.flat_sheet:
+
+                @self.Constraint(
+                    self.flowsheet().config.time,
+                    self.length_domain,
+                    doc="Darcy friction factor constraint for flat sheet membranes",
+                )
+                def eq_friction_factor(b, t, x):
+                    return (b.friction_factor_darcy[t, x] - 0.42) * b.N_Re[
+                        t, x
+                    ] == 189.3
+
+            # Darcy friction factor based on eq. 24 in Mass transfer and pressure loss in spiral wound modules (Schock & Miquel, 1987)
+            elif module_type == ModuleType.spiral_wound:
+
+                @self.Constraint(
+                    self.flowsheet().config.time,
+                    self.length_domain,
+                    doc="Darcy friction factor constraint for spiral-wound membranes",
+                )
+                def eq_friction_factor(b, t, x):
+                    return b.friction_factor_darcy[t, x] == 6.23 * b.N_Re[t, x] ** -0.3
 
+            else:
+                raise ConfigurationError(f"Unrecognized module_type type {module_type}")
         else:
-            raise ConfigurationError(
-                f"Unrecognized friction_factor type {friction_factor}"
-            )
+            pass
 
         ## ==========================================================================
         # Pressure change per unit length due to friction
@@ -1021,11 +1055,3 @@ def validate_membrane_config_args(unit):
                 unit.config.concentration_polarization_type,
             )
         )
-
-    if (
-        unit.config.pressure_change_type != PressureChangeType.calculated
-        and unit.config.friction_factor != unit.config.get("friction_factor")._default
-    ):
-        raise ConfigurationError(
-            "\nChanging the 'friction_factor' will have no effect if the 'pressure_change_type' is not `PressureChangeType.calculated`"
-        )
diff --git a/watertap/unit_models/osmotically_assisted_reverse_osmosis_1D.py b/watertap/unit_models/osmotically_assisted_reverse_osmosis_1D.py
index 8d89266e54..ce42c2d784 100644
--- a/watertap/unit_models/osmotically_assisted_reverse_osmosis_1D.py
+++ b/watertap/unit_models/osmotically_assisted_reverse_osmosis_1D.py
@@ -208,8 +208,8 @@ def eq_connect_mass_transfer(b, t, x, p, j):
         )
         def eq_permeate_production(b, t, x, p, j):
             return (
-                -b.feed_side.mass_transfer_term[t, x, p, j]
-                == b.width * b.flux_mass_phase_comp[t, x, p, j]
+                -b.feed_side.mass_transfer_term[t, x, p, j] * b.length
+                == b.flux_mass_phase_comp[t, x, p, j] * b.area
             )
 
     def calculate_scaling_factors(self):
diff --git a/watertap/unit_models/osmotically_assisted_reverse_osmosis_base.py b/watertap/unit_models/osmotically_assisted_reverse_osmosis_base.py
index 2f6891f7b8..748346f46f 100644
--- a/watertap/unit_models/osmotically_assisted_reverse_osmosis_base.py
+++ b/watertap/unit_models/osmotically_assisted_reverse_osmosis_base.py
@@ -36,6 +36,7 @@
     validate_membrane_config_args,
     ConcentrationPolarizationType,
     TransportModel,
+    ModuleType,
 )
 
 from watertap.core import InitializationMixin
@@ -116,6 +117,7 @@ def build(self):
             balance_type=self.config.momentum_balance_type,
             pressure_change_type=self.config.pressure_change_type,
             has_pressure_change=self.config.has_pressure_change,
+            module_type=self.config.module_type,
             friction_factor=self.config.friction_factor,
         )
 
@@ -153,6 +155,7 @@ def build(self):
             balance_type=self.config.momentum_balance_type,
             pressure_change_type=self.config.pressure_change_type,
             has_pressure_change=self.config.has_pressure_change,
+            module_type=self.config.module_type,
             friction_factor=self.config.friction_factor,
         )
 
@@ -341,15 +344,24 @@ def _add_area(self, include_constraint=True):
 
         if include_constraint:
             if not hasattr(self, "eq_area"):
-                # Membrane area equation
-                @self.Constraint(doc="Total Membrane area")
-                def eq_area(b):
-                    return b.area == b.length * b.width
-
-            else:
-                raise ValueError(
-                    "include_constraint was set to True inside of _add_area(), but area constraint already exists."
-                )
+                if self.config.module_type == ModuleType.flat_sheet:
+                    # Membrane area equation for flat plate membranes
+                    @self.Constraint(doc="Total Membrane area")
+                    def eq_area(b):
+                        return b.area == b.length * b.width
+
+                elif self.config.module_type == ModuleType.spiral_wound:
+                    # Membrane area equation
+                    @self.Constraint(doc="Total Membrane area")
+                    def eq_area(b):
+                        return b.area == b.length * 2 * b.width
+
+                else:
+                    raise ConfigurationError(
+                        "Unsupported membrane module type: {}".format(
+                            self.config.module_type
+                        )
+                    )
 
     def _add_flux_balance(self):
 
diff --git a/watertap/unit_models/reverse_osmosis_1D.py b/watertap/unit_models/reverse_osmosis_1D.py
index 5ba3e1167d..3840f173a3 100644
--- a/watertap/unit_models/reverse_osmosis_1D.py
+++ b/watertap/unit_models/reverse_osmosis_1D.py
@@ -188,8 +188,8 @@ def eq_connect_mass_transfer(b, t, x, p, j):
         )
         def eq_mass_flux_equal_mass_transfer(b, t, x, p, j):
             return (
-                b.flux_mass_phase_comp[t, x, p, j] * b.width
-                == -b.feed_side.mass_transfer_term[t, x, p, j]
+                b.flux_mass_phase_comp[t, x, p, j] * b.area
+                == -b.feed_side.mass_transfer_term[t, x, p, j] * b.length
             )
 
         # ==========================================================================
diff --git a/watertap/unit_models/reverse_osmosis_base.py b/watertap/unit_models/reverse_osmosis_base.py
index 896631291c..20d795a1d8 100644
--- a/watertap/unit_models/reverse_osmosis_base.py
+++ b/watertap/unit_models/reverse_osmosis_base.py
@@ -36,6 +36,7 @@
     validate_membrane_config_args,
     ConcentrationPolarizationType,
     TransportModel,
+    ModuleType,
 )
 from watertap.costing.unit_models.reverse_osmosis import cost_reverse_osmosis
 
@@ -100,7 +101,6 @@ def build(self):
             balance_type=self.config.momentum_balance_type,
             pressure_change_type=self.config.pressure_change_type,
             has_pressure_change=self.config.has_pressure_change,
-            friction_factor=self.config.friction_factor,
         )
 
         self.feed_side.add_control_volume_isothermal_conditions()
@@ -287,10 +287,24 @@ def _add_area(self, include_constraint=True):
         )
 
         if include_constraint:
-            # Membrane area equation
-            @self.Constraint(doc="Total Membrane area")
-            def eq_area(b):
-                return b.area == b.length * b.width
+            if self.config.module_type == ModuleType.flat_sheet:
+                # Membrane area equation for flat plate membranes
+                @self.Constraint(doc="Total Membrane area")
+                def eq_area(b):
+                    return b.area == b.length * b.width
+
+            elif self.config.module_type == ModuleType.spiral_wound:
+                # Membrane area equation
+                @self.Constraint(doc="Total Membrane area")
+                def eq_area(b):
+                    return b.area == b.length * 2 * b.width
+
+            else:
+                raise ConfigurationError(
+                    "Unsupported membrane module type: {}".format(
+                        self.config.module_type
+                    )
+                )
 
     def _add_flux_balance(self):
 
diff --git a/watertap/unit_models/tests/test_osmotically_assisted_reverse_osmosis_0D.py b/watertap/unit_models/tests/test_osmotically_assisted_reverse_osmosis_0D.py
index 762ceb2ee0..7c02b72ea9 100644
--- a/watertap/unit_models/tests/test_osmotically_assisted_reverse_osmosis_0D.py
+++ b/watertap/unit_models/tests/test_osmotically_assisted_reverse_osmosis_0D.py
@@ -20,7 +20,7 @@
 from watertap.unit_models.osmotically_assisted_reverse_osmosis_0D import (
     OsmoticallyAssistedReverseOsmosis0D,
 )
-from watertap.unit_models.reverse_osmosis_base import TransportModel
+from watertap.unit_models.reverse_osmosis_base import TransportModel, ModuleType
 import watertap.property_models.NaCl_prop_pack as props
 from watertap.core.solvers import get_solver
 from idaes.core.util.scaling import (
@@ -31,7 +31,6 @@
     ConcentrationPolarizationType,
     MassTransferCoefficient,
     PressureChangeType,
-    FrictionFactor,
 )
 
 from watertap.unit_models.tests.unit_test_harness import UnitTestHarness
@@ -806,7 +805,7 @@ def configure(self):
         return m
 
 
-def build_friction_factor_spiral_wound():
+def build_module_type_spiral_wound():
     """Testing 0D-OARO with FrictionFactor.spiral_wound option."""
     m = ConcreteModel()
     m.fs = FlowsheetBlock(dynamic=False)
@@ -819,7 +818,7 @@ def build_friction_factor_spiral_wound():
         concentration_polarization_type=ConcentrationPolarizationType.calculated,
         mass_transfer_coefficient=MassTransferCoefficient.calculated,
         pressure_change_type=PressureChangeType.calculated,
-        friction_factor=FrictionFactor.spiral_wound,
+        module_type=ModuleType.spiral_wound,
     )
 
     # fully specify system
@@ -879,55 +878,55 @@ class TestOsmoticallyAssistedReverseOsmosis_friction_factor_spiral_wound(
     UnitTestHarness
 ):
     def configure(self):
-        m = build_friction_factor_spiral_wound()
+        m = build_module_type_spiral_wound()
 
-        self.unit_solutions[m.fs.unit.feed_side.deltaP[0]] = -0.3019e5
-        self.unit_solutions[m.fs.unit.permeate_side.deltaP[0]] = -2.4123e5
-        self.unit_solutions[m.fs.unit.feed_side.deltaP[0] / m.fs.unit.length] = -3940.35
+        self.unit_solutions[m.fs.unit.feed_side.deltaP[0]] = -0.1516e5
+        self.unit_solutions[m.fs.unit.permeate_side.deltaP[0]] = -1.199e5
+        self.unit_solutions[m.fs.unit.feed_side.deltaP[0] / m.fs.unit.length] = -3958.30
         self.unit_solutions[m.fs.unit.permeate_side.deltaP[0] / m.fs.unit.length] = (
-            -31488.754
+            -31318.596
         )
         self.unit_solutions[m.fs.unit.feed_side.N_Re[0, 0.0]] = 145.197
         self.unit_solutions[m.fs.unit.feed_side.velocity[0, 0.0]] = 0.1
-        self.unit_solutions[m.fs.unit.feed_side.N_Re[0, 1.0]] = 110.973
-        self.unit_solutions[m.fs.unit.feed_side.velocity[0, 1.0]] = 0.0774
-        self.unit_solutions[m.fs.unit.permeate_side.N_Re[0, 0.0]] = 154.231
-        self.unit_solutions[m.fs.unit.permeate_side.velocity[0, 0.0]] = 0.2040
+        self.unit_solutions[m.fs.unit.feed_side.N_Re[0, 1.0]] = 111.787
+        self.unit_solutions[m.fs.unit.feed_side.velocity[0, 1.0]] = 0.0779
+        self.unit_solutions[m.fs.unit.permeate_side.N_Re[0, 0.0]] = 153.410
+        self.unit_solutions[m.fs.unit.permeate_side.velocity[0, 0.0]] = 0.2029
         self.unit_solutions[m.fs.unit.permeate_side.N_Re[0, 1.0]] = 119.793
         self.unit_solutions[m.fs.unit.permeate_side.velocity[0, 1.0]] = 0.1588
         self.unit_solutions[m.fs.unit.flux_mass_phase_comp_avg[0, "Liq", "H2O"]] = (
-            4.407e-3
+            4.301e-3
         )
         self.unit_solutions[m.fs.unit.flux_mass_phase_comp_avg[0, "Liq", "NaCl"]] = (
-            5.881e-7
+            5.837e-7
         )
         self.unit_solutions[
             m.fs.unit.feed_side.properties_interface[0, 0.0].conc_mass_phase_comp[
                 "Liq", "NaCl"
             ]
-        ] = 43.978
+        ] = 43.505
         self.unit_solutions[
             m.fs.unit.feed_side.properties_out[0].conc_mass_phase_comp["Liq", "NaCl"]
-        ] = 46.152
+        ] = 45.833
         self.unit_solutions[
             m.fs.unit.feed_side.properties_interface[0, 1.0].conc_mass_phase_comp[
                 "Liq", "NaCl"
             ]
-        ] = 51.466
+        ] = 51.292
         self.unit_solutions[
             m.fs.unit.permeate_side.properties_interface[0, 1.0].conc_mass_phase_comp[
                 "Liq", "NaCl"
             ]
-        ] = 3.520
+        ] = 3.445
         self.unit_solutions[
             m.fs.unit.permeate_side.properties_interface[0, 0.0].conc_mass_phase_comp[
                 "Liq", "NaCl"
             ]
-        ] = 1.443
+        ] = 1.547
         self.unit_solutions[
             m.fs.unit.permeate_side.properties_out[0].conc_mass_phase_comp[
                 "Liq", "NaCl"
             ]
-        ] = 5.007
+        ] = 5.033
 
         return m
diff --git a/watertap/unit_models/tests/test_osmotically_assisted_reverse_osmosis_1D.py b/watertap/unit_models/tests/test_osmotically_assisted_reverse_osmosis_1D.py
index 17fa705e1a..3fe0d3a850 100644
--- a/watertap/unit_models/tests/test_osmotically_assisted_reverse_osmosis_1D.py
+++ b/watertap/unit_models/tests/test_osmotically_assisted_reverse_osmosis_1D.py
@@ -22,7 +22,7 @@
 from watertap.unit_models.osmotically_assisted_reverse_osmosis_1D import (
     OsmoticallyAssistedReverseOsmosis1D,
 )
-from watertap.unit_models.reverse_osmosis_base import TransportModel
+from watertap.unit_models.reverse_osmosis_base import TransportModel, ModuleType
 import watertap.property_models.NaCl_prop_pack as props
 
 from watertap.core.solvers import get_solver
@@ -613,7 +613,7 @@ def configure(self):
             m.fs.unit.permeate_side.properties_interface[
                 0, x_interface_in
             ].conc_mass_phase_comp["Liq", "NaCl"]
-        ] = 45.111
+        ] = 45.1565
         self.unit_solutions[
             m.fs.unit.permeate_side.properties_interface[0, 1.0].conc_mass_phase_comp[
                 "Liq", "NaCl"
@@ -1003,6 +1003,145 @@ def configure(self):
         return m
 
 
+def build_Pdrop_spiral_wound_calculation():
+    """Testing 1D-OARO with PressureChangeType.calculated option."""
+    m = ConcreteModel()
+    m.fs = FlowsheetBlock(dynamic=False)
+
+    m.fs.properties = props.NaClParameterBlock()
+
+    m.fs.unit = OsmoticallyAssistedReverseOsmosis1D(
+        property_package=m.fs.properties,
+        has_pressure_change=True,
+        concentration_polarization_type=ConcentrationPolarizationType.calculated,
+        mass_transfer_coefficient=MassTransferCoefficient.calculated,
+        pressure_change_type=PressureChangeType.calculated,
+        module_type=ModuleType.spiral_wound,
+    )
+    # fully specify system
+    feed_flow_mass = 5 / 18
+    feed_mass_frac_NaCl = 0.075
+    feed_pressure = 65e5
+    feed_temperature = 273.15 + 25
+    membrane_area = 70
+    length = 35
+    A = 1e-12
+    B = 7.7e-8
+
+    feed_mass_frac_H2O = 1 - feed_mass_frac_NaCl
+    m.fs.unit.feed_inlet.flow_mass_phase_comp[0, "Liq", "NaCl"].fix(
+        feed_flow_mass * feed_mass_frac_NaCl
+    )
+    m.fs.unit.feed_inlet.flow_mass_phase_comp[0, "Liq", "H2O"].fix(
+        feed_flow_mass * feed_mass_frac_H2O
+    )
+    m.fs.unit.feed_inlet.pressure[0].fix(feed_pressure)
+    m.fs.unit.feed_inlet.temperature[0].fix(feed_temperature)
+
+    permeate_flow_mass = 0.33 * feed_flow_mass
+    permeate_mass_frac_NaCl = 0.1
+    permeate_mass_frac_H2O = 1 - permeate_mass_frac_NaCl
+    m.fs.unit.permeate_inlet.flow_mass_phase_comp[0, "Liq", "H2O"].fix(
+        permeate_flow_mass * permeate_mass_frac_H2O
+    )
+    m.fs.unit.permeate_inlet.flow_mass_phase_comp[0, "Liq", "NaCl"].fix(
+        permeate_flow_mass * permeate_mass_frac_NaCl
+    )
+    m.fs.unit.permeate_inlet.pressure[0].fix(5e5)
+    m.fs.unit.permeate_inlet.temperature[0].fix(feed_temperature)
+
+    m.fs.unit.area.fix(membrane_area)
+    m.fs.unit.length.fix(length)
+    m.fs.unit.A_comp.fix(A)
+    m.fs.unit.B_comp.fix(B)
+    m.fs.unit.structural_parameter.fix(1200e-6)
+
+    m.fs.unit.permeate_side.channel_height.fix(0.002)
+    m.fs.unit.permeate_side.spacer_porosity.fix(0.97)
+    m.fs.unit.feed_side.channel_height.fix(0.002)
+    m.fs.unit.feed_side.spacer_porosity.fix(0.97)
+
+    # scaling
+    m.fs.properties.set_default_scaling(
+        "flow_mass_phase_comp", 1e1, index=("Liq", "H2O")
+    )
+    m.fs.properties.set_default_scaling(
+        "flow_mass_phase_comp", 1e3, index=("Liq", "NaCl")
+    )
+    calculate_scaling_factors(m)
+
+    return m
+
+
+class TestOsmoticallyAssistedReverseOsmosis_Pdrop_spiral_wound_calculation(
+    UnitTestHarness
+):
+    def configure(self):
+        m = build_Pdrop_spiral_wound_calculation()
+
+        self.unit_solutions[m.fs.unit.feed_side.N_Re[0, 0.0]] = 434.64
+        self.unit_solutions[m.fs.unit.feed_side.velocity[0, 0.0]] = 0.1361
+        self.unit_solutions[m.fs.unit.feed_side.N_Re[0, 1.0]] = 317.794
+        self.unit_solutions[m.fs.unit.feed_side.velocity[0, 1.0]] = 0.1021
+        self.unit_solutions[m.fs.unit.permeate_side.N_Re[0, 0.0]] = 254.272
+        self.unit_solutions[m.fs.unit.permeate_side.velocity[0, 0.0]] = 0.07824
+        self.unit_solutions[m.fs.unit.permeate_side.N_Re[0, 1.0]] = 136.979
+        self.unit_solutions[m.fs.unit.permeate_side.velocity[0, 1.0]] = 0.04413
+
+        self.unit_solutions[m.fs.unit.feed_side.deltaP_stage[0]] = -77476.0524412
+        self.unit_solutions[m.fs.unit.permeate_side.deltaP_stage[0]] = -24177.6101955
+
+        self.unit_solutions[m.fs.unit.flux_mass_phase_comp_avg[0, "Liq", "H2O"]] = (
+            9.419628912e-04
+        )
+        self.unit_solutions[m.fs.unit.flux_mass_phase_comp_avg[0, "Liq", "NaCl"]] = (
+            4.38572890e-06
+        )
+        self.unit_solutions[
+            m.fs.unit.feed_outlet.flow_mass_phase_comp[0, "Liq", "H2O"]
+        ] = 0.1910
+        self.unit_solutions[
+            m.fs.unit.feed_outlet.flow_mass_phase_comp[0, "Liq", "NaCl"]
+        ] = 0.02052
+
+        self.unit_solutions[
+            m.fs.unit.feed_side.properties[0, 0].conc_mass_phase_comp["Liq", "NaCl"]
+        ] = 78.878
+
+        x_interface_in = m.fs.unit.length_domain.at(2)
+        self.unit_solutions[
+            m.fs.unit.feed_side.properties_interface[
+                0, x_interface_in
+            ].conc_mass_phase_comp["Liq", "NaCl"]
+        ] = 85.616
+        self.unit_solutions[
+            m.fs.unit.feed_side.properties[0, 1].conc_mass_phase_comp["Liq", "NaCl"]
+        ] = 103.670
+        self.unit_solutions[
+            m.fs.unit.feed_side.properties_interface[0, 1].conc_mass_phase_comp[
+                "Liq", "NaCl"
+            ]
+        ] = 108.735
+        self.unit_solutions[
+            m.fs.unit.permeate_side.properties[0, 1].conc_mass_phase_comp["Liq", "NaCl"]
+        ] = 107.06
+        self.unit_solutions[
+            m.fs.unit.permeate_side.properties_interface[0, 1].conc_mass_phase_comp[
+                "Liq", "NaCl"
+            ]
+        ] = 53.136
+        self.unit_solutions[
+            m.fs.unit.permeate_side.properties[0, 0].conc_mass_phase_comp["Liq", "NaCl"]
+        ] = 62.415
+        self.unit_solutions[
+            m.fs.unit.permeate_side.properties_interface[
+                0, x_interface_in
+            ].conc_mass_phase_comp["Liq", "NaCl"]
+        ] = 28.036
+
+        return m
+
+
 class TestOsmoticallyAssistedReverseOsmosis_water_recovery:
     water_recovery_list = [0.15, 0.2, 0.3, 0.4, 0.5, 0.55]
 
diff --git a/watertap/unit_models/tests/test_reverse_osmosis_0D.py b/watertap/unit_models/tests/test_reverse_osmosis_0D.py
index d9b97d7041..48d89d5477 100644
--- a/watertap/unit_models/tests/test_reverse_osmosis_0D.py
+++ b/watertap/unit_models/tests/test_reverse_osmosis_0D.py
@@ -24,14 +24,12 @@
     PressureChangeType,
 )
 
-from watertap.unit_models.reverse_osmosis_base import TransportModel
+from watertap.unit_models.reverse_osmosis_base import TransportModel, ModuleType
 
 import watertap.property_models.NaCl_prop_pack as props
 
 from watertap.unit_models.tests.unit_test_harness import UnitTestHarness
 
-from watertap.core import FrictionFactor
-
 # -----------------------------------------------------------------------------
 # Get default solver for testing
 solver = get_solver()
@@ -554,7 +552,7 @@ def build_friction_factor_spiral_wound():
         concentration_polarization_type=ConcentrationPolarizationType.calculated,
         mass_transfer_coefficient=MassTransferCoefficient.calculated,
         pressure_change_type=PressureChangeType.calculated,
-        friction_factor=FrictionFactor.spiral_wound,
+        module_type=ModuleType.spiral_wound,
     )
 
     # fully specify system
@@ -598,35 +596,35 @@ class TestReverseOsmosis0D_friction_factor_spiral_wound(UnitTestHarness):
     def configure(self):
         m = build_friction_factor_spiral_wound()
 
-        self.unit_solutions[m.fs.unit.deltaP[0]] = -1.801003299e5
-        self.unit_solutions[m.fs.unit.feed_side.N_Re[0, 0]] = 395.840743
-        self.unit_solutions[m.fs.unit.feed_side.velocity[0, 0]] = 0.2360863
-        self.unit_solutions[m.fs.unit.feed_side.N_Re[0, 1]] = 191.3192807
-        self.unit_solutions[m.fs.unit.feed_side.velocity[0, 1]] = 0.1188201
+        self.unit_solutions[m.fs.unit.deltaP[0]] = -4.68073933e5
+        self.unit_solutions[m.fs.unit.feed_side.N_Re[0, 0]] = 791.6814859
+        self.unit_solutions[m.fs.unit.feed_side.velocity[0, 0]] = 0.472172596
+        self.unit_solutions[m.fs.unit.feed_side.N_Re[0, 1]] = 374.5383911
+        self.unit_solutions[m.fs.unit.feed_side.velocity[0, 1]] = 0.2329687
         self.unit_solutions[m.fs.unit.flux_mass_phase_comp_avg[0, "Liq", "H2O"]] = (
-            0.00708203
+            0.0072232991
         )
         self.unit_solutions[m.fs.unit.flux_mass_phase_comp_avg[0, "Liq", "NaCl"]] = (
-            2.18590835e-6
+            2.11255771e-6
         )
         self.unit_solutions[
             m.fs.unit.mixed_permeate[0].flow_mass_phase_comp["Liq", "H2O"]
-        ] = 0.13455865
+        ] = 0.13724268
         self.unit_solutions[
             m.fs.unit.mixed_permeate[0].flow_mass_phase_comp["Liq", "NaCl"]
-        ] = 4.15322586e-5
+        ] = 4.01385965e-5
         self.unit_solutions[
             m.fs.unit.feed_side.properties_interface[0, 0].conc_mass_phase_comp[
                 "Liq", "NaCl"
             ]
-        ] = 50.075075
+        ] = 47.435640
         self.unit_solutions[
             m.fs.unit.feed_side.properties_out[0].conc_mass_phase_comp["Liq", "NaCl"]
-        ] = 70.73118
+        ] = 72.1598903
         self.unit_solutions[
             m.fs.unit.feed_side.properties_interface[0, 1].conc_mass_phase_comp[
                 "Liq", "NaCl"
             ]
-        ] = 76.211017
+        ] = 75.1415897247
 
         return m
diff --git a/watertap/unit_models/tests/test_reverse_osmosis_1D.py b/watertap/unit_models/tests/test_reverse_osmosis_1D.py
index 88053602ae..0b4896a107 100644
--- a/watertap/unit_models/tests/test_reverse_osmosis_1D.py
+++ b/watertap/unit_models/tests/test_reverse_osmosis_1D.py
@@ -17,15 +17,12 @@
 
 import idaes.core.util.scaling as iscale
 
-from watertap.unit_models.reverse_osmosis_base import TransportModel
+from watertap.unit_models.reverse_osmosis_base import TransportModel, ModuleType
 
 import watertap.property_models.NaCl_prop_pack as props
 
 from watertap.unit_models.tests.unit_test_harness import UnitTestHarness
 
-from watertap.core import FrictionFactor
-
-
 from watertap.unit_models.reverse_osmosis_1D import (
     ReverseOsmosis1D,
     ConcentrationPolarizationType,
@@ -33,7 +30,6 @@
     PressureChangeType,
 )
 
-
 # -----------------------------------------------------------------------------
 # Get default solver for testing
 solver = get_solver()
@@ -575,7 +571,7 @@ def build_friction_factor_spiral_wound():
         concentration_polarization_type=ConcentrationPolarizationType.calculated,
         mass_transfer_coefficient=MassTransferCoefficient.calculated,
         pressure_change_type=PressureChangeType.calculated,
-        friction_factor=FrictionFactor.spiral_wound,
+        module_type=ModuleType.spiral_wound,
         transformation_scheme="BACKWARD",
         transformation_method="dae.finite_difference",
         finite_elements=3,
@@ -628,22 +624,22 @@ def configure(self):
 
         self.unit_solutions[
             m.fs.unit.flux_mass_phase_comp[0, x_interface_in, "Liq", "H2O"]
-        ] = 0.00590823
+        ] = 0.00593246
         self.unit_solutions[
             m.fs.unit.flux_mass_phase_comp[0, x_interface_in, "Liq", "NaCl"]
-        ] = 1.494063e-6
+        ] = 1.4481768e-6
         self.unit_solutions[m.fs.unit.flux_mass_phase_comp[0, 1, "Liq", "H2O"]] = (
-            0.00474506
+            0.0041822435
         )
         self.unit_solutions[m.fs.unit.flux_mass_phase_comp[0, 1, "Liq", "NaCl"]] = (
-            1.559319e-6
+            1.491610924e-6
         )
         self.unit_solutions[
             m.fs.unit.mixed_permeate[0].flow_mass_phase_comp["Liq", "H2O"]
-        ] = 0.1010762
+        ] = 0.095819393
         self.unit_solutions[
             m.fs.unit.mixed_permeate[0].flow_mass_phase_comp["Liq", "NaCl"]
-        ] = 2.9015866e-5
+        ] = 2.794556261e-5
 
         return m