Simple OD Nanofiltration model

docs/technical_reference/unit_models/index.rst

@@ -26,6 +26,7 @@ Unit Models
    membrane_distillation_1D
    mvc
    nanofiltration_ZO
+   nanofiltration_0D
    nanofiltration_dspmde_0D
    osmotically_assisted_reverse_osmosis_0D
    osmotically_assisted_reverse_osmosis_1D

docs/technical_reference/unit_models/nanofiltration_0D.rst

@@ -0,0 +1,70 @@
+Nanofiltration (0D)
+====================
+This nanofiltration (NF) unit model is suitable for non-predictive case studies where the user wishes to specify, constant rejection fractions
+whilst preserving electroneutrality in the permeate stream (optional). A single recovery fraction is assumed for all solvents, whilst
+individual rejection fractions can be set for all solutes, with the exception of one ion specified for maintaining
+electroneutrality. Solutes are assigned default rejection value by grouping them into either two categories, passing and excluded, with
+default rejection values for each category. Solutes are categorised using either a user-provided list of species which freely pass the
+membrane, or by assuming all neutral and monovalent species pass the membrane.
+
+Retentate pressure is assumed to be related to feed pressure with an optional pressure drop whilst permeate pressure is assumed to be
+a degree of freedom, and temperature equality is assumed. Temperature and pressure constraints can be removed with configuration arguments.
+
+This model assumes supports a single liquid phase only and assumes steady-state.
+
+.. index::
+   pair: watertap.unit_models.nanofiltration_0D;nanofiltration_0D
+
+.. currentmodule:: watertap.unit_models.nanofiltration_0D
+
+Degrees of Freedom
+------------------
+The ``Nanofiltration0D`` model has the following degrees of freedom
+
+   * inlet state
+   * permeate pressure
+   * solvent recovery fraction (``solvent_recovery``)
+   * solute rejection fractions (``rekection_comp``) for all solutes EXCEPT the one identified as the electroneutrality species.
+
+The following additional degrees of freedom  may exist depending on configuration options
+
+   * retentate pressure drop (``deltaP``)
+
+Model Structure
+---------------
+The Nanofiltration0D model consists of three state blocks (``properties_in``, ``properties_retentate`` and ``properties_permeate``).
+
+.. _NF0D_variables:
+
+Variables
+---------
+
+.. csv-table::
+   :header: "Description", "Symbol", "Variable Name", "Index", "Units"
+
+   "Solvent recovery", ":math:`Q_{solvent}`", "solvent_recovery", None, ":math:`\text{dimensionless}`"
+   "Solute rejection", ":math:`R_j`", "rejection_comp", [j], ":math:`\text{dimensionless}`"
+   "Retentate pressure drop", ":math:`\deltaP`", "deltaP", [t], ":math:`\text{pressure}`"
+
+.. _NF0D_equations:
+
+Equations
+---------
+
+Here :math:`F` represents component flowrate and :math:`Z_j` is the charge on species j.
+
+.. csv-table::
+   :header: "Description", "Equation"
+
+   "Component material balances", ":math:`F_{in, j} = F_{retentate, j} + F_{permeate, j}`"
+   "Solvent recovery",":math:`Q_{solvent} \times F_{in, j} = F_{permeate_j}`"
+   "Solute rejection",":math:`R_j = 1 - \frac{C_{permeate, j}}{C_{feed_j}}`"
+   "Permeate electroneutrality",":math:`0 = F_{permeate, j} \times Z_{j}`"
+   "Retentate pressure balance",":math:`P_{in} = P_{retentate} - \deltaP`"
+   "Retentate temperature equality", ":math:`T_{in} = T_{retentate}`"
+   "Permeate temperature equality", ":math:`T_{in} = T_{permeate}`"
+
+Class Documentation
+-------------------
+
+* :mod:`watertap.unit_models.nanofiltration_0D`