add TVC model

docs/technical_reference/unit_models/index.rst

@@ -32,6 +32,7 @@ Unit Models
    pump
    reverse_osmosis_0D
    reverse_osmosis_1D
+   steam_ejector
    stoichiometric_reactor
    thickener
    translators/index

docs/technical_reference/unit_models/steam_ejector.rst

@@ -0,0 +1,69 @@
+Steam Jet Ejector
+================================
+This Steam Jet Ejector unit model:
+   * Simulates the performance of a steam jet ejector for thermal vapor compression.
+   * Uses semi-empirical correlations for entrainment ratio, PCF, and TCF based on El-Dessouky (1997).
+   * Operates in steady-state only.
+   * Assumes the discharge mixture pressure equals its saturation pressure.
+
+.. index::
+   pair: watertap.unit_models.steam_ejector;steam_ejector
+
+.. currentmodule:: watertap.unit_models.steam_ejector
+
+Degrees of Freedom
+-------------------
+In addition to the inlet state variables (i.e., temperature, pressure, and component flowrates for motive steam and entrained vapor), the Steam Ejector model has at least 1 degrees of freedom that must be fixed for the unit to be fully specified. Typically, the following variables are fixed:
+
+    * Entrainment ratio
+    * Compression ratio
+
+Model Structure
+------------------
+This Steam Ejector model consists of state blocks for the properties of the motive steam inlet, entrained vapor inlet, and discharge mixture. It incorporates semi-empirical equations to model key performance parameters.
+
+Equations
+---------
+.. csv-table::
+   :header: "Description", "Equation"
+
+   "Pressure Correction Factor", ":math:`PCF = 3 \times 10^{-7} P_m^2 - 0.0009 P_m + 1.6101`"
+   "Temperature Correction Factor", ":math:`TCF = 2 \times 10^{-8} T_{ev}^2 - 0.0006 T_{ev} + 1.0047`"
+   "Entrainment Ratio Model", ":math:`Ra \times TCF = 0.296 \frac{P_s^{1.19}}{P_{ev}^{1.04}} \left(\frac{P_m}{P_{ev}}\right)^{0.015} PCF`"
+   "Entrainment Ratio Definition", ":math:`Ra = \frac{\dot{m}_{motive}}{\dot{m}_{entrained}}`"
+   "Compression Ratio", ":math:`CR = \frac{P_s}{P_{ev}}`"
+
+Variables
+----------
+.. csv-table::
+   :header: "Description", "Symbol", "Variable Name", "Units", "Bounds"
+
+   "Entrainment Ratio", ":math:`Ra`", "entrainment_ratio", "Dimensionless", "<4"
+   "Compression Ratio", ":math:`CR`", "compression_ratio", "Dimensionless", ">1.89"
+   "Pressure Correction Factor", ":math:`PCF`", "PCF", "Dimensionless", "-"
+   "Temperature Correction Factor", ":math:`TCF`", "TCF", "Dimensionless", "-"
+   "Motive Steam Pressure", ":math:`P_m`", "properties_motive_steam[0].pressure", "kPa", "[100, 3500]"
+   "Entrained Vapor Pressure", ":math:`P_{ev}`", "properties_entrained_vapor[0].pressure", "kPa", "-"
+   "Discharge Mixture Pressure", ":math:`P_s`", "properties_discharge_mix[0].pressure", "kPa", "-"
+
+Sets
+----
+.. csv-table::
+   :header: "Description", "Symbol", "Indices"
+
+   "Time", ":math:`t`", "[0]"
+   "Inlet/Outlet", ":math:`x`", "['in', 'out']"
+   "Phases", ":math:`p`", "['Liq', 'Vap']"
+   "Components", ":math:`j`", "['H2O']"
+
+Performance Metrics
+--------------------
+.. csv-table::
+   :header: "Metric", "Equation"
+
+   "Entrainment Ratio", ":math:`Ra = \frac{\dot{m}_{motive}}{\dot{m}_{entrained}}`"
+   "Compression Ratio", ":math:`CR = \frac{P_s}{P_{ev}}`"
+
+Class Documentation
+-------------------
+* :mod:`watertap.unit_models.steam_ejector`

watertap/costing/unit_models/steam_ejector.py

@@ -0,0 +1,79 @@
+import pyomo.environ as pyo
+from ..util import register_costing_parameter_block, make_capital_cost_var
+
+
+def build_steam_ejector_cost_param_block(blk):
+    """
+    Build the costing parameter block for the steam ejector.
+    """
+    blk.base_cost = pyo.Var(
+        initialize=1949,
+        doc="Base cost coefficient for steam ejector",
+        units=pyo.units.USD_2020,
+    )
+    blk.cost_exponent = pyo.Var(
+        initialize=0.3,
+        doc="Cost scaling exponent",
+        units=pyo.units.dimensionless,
+    )
+
+    blk.steam_cost = pyo.Var(
+        initialize=0.008,
+        units=pyo.units.USD_2018 / pyo.units.kg,
+        doc="Steam cost per kg",
+    )
+
+    blk.parent_block().register_flow_type("steam", blk.steam_cost)
+
+
+@register_costing_parameter_block(
+    build_rule=build_steam_ejector_cost_param_block,
+    parameter_block_name="steam_ejector",
+)
+def cost_steam_ejector(blk, cost_steam_flow=False):
+    """
+    Thermo Compressor (Steam Ejector) Costing Method.
+
+    Capital cost is calculated using the equation:
+        Capital Cost (USD) = 1949 × (S + EV)^0.3  (Gabriel 2015, Desalination)
+    where:
+        S  = Motive steam flow rate (kg/h)
+        EV = Entrained vapor flow rate (kg/h)
+
+    """
+
+    make_capital_cost_var(blk)
+    blk.costing_package.add_cost_factor(blk, "TIC")
+
+    S = pyo.units.convert(
+        blk.unit_model.properties_motive_steam[0.0].flow_mass_phase_comp["Vap", "H2O"],
+        to_units=pyo.units.kg / pyo.units.hour,
+    )
+
+    EV = pyo.units.convert(
+        blk.unit_model.properties_entrained_vapor[0.0].flow_mass_phase_comp[
+            "Vap", "H2O"
+        ],
+        to_units=pyo.units.kg / pyo.units.hour,
+    )
+
+    blk.capital_cost_constraint = pyo.Constraint(
+        expr=blk.capital_cost
+        == blk.cost_factor
+        * pyo.units.convert(
+            blk.costing_package.steam_ejector.base_cost
+            * (S + EV) ** blk.costing_package.steam_ejector.cost_exponent,
+            to_units=blk.costing_package.base_currency,
+        )
+    )
+
+    if cost_steam_flow:
+        blk.costing_package.cost_flow(
+            pyo.units.convert(
+                blk.unit_model.properties_motive_steam[0.0].flow_mass_phase_comp[
+                    "Vap", "H2O"
+                ],
+                to_units=pyo.units.kg / pyo.units.s,
+            ),
+            "steam",
+        )