Reverse Osmosis (1D)
- This reverse osmosis (RO) unit model
is 1-dimensional
supports a single liquid phase only
supports steady-state only
is based on the solution-diffusion model and film theory
assumes isothermal conditions
Degrees of Freedom
Aside from the inlet feed state variables (i.e. temperature, pressure, component flowrates), the RO model has at least 4 degrees of freedom that should be fixed for the unit to be fully specified.
- Typically, the following variables are fixed, in addition to state variables at the inlet:
membrane water permeability, A
membrane salt permeability, B
permeate outlet pressure
membrane area or length or width
Note
This section is pending since the 1D-RO model is currently under development.
Model Structure
This RO model consists of 1 ControlVolume1DBlock for the feed-side (feed_side.properties[t, x]), a StateBlock indexed by time and space for the permeate-side (permeate_side[t, x]), and a StateBlock for the final permeate at the outlet (permeate_out).
Sets
Description |
Symbol |
Indices |
---|---|---|
Time |
\(t\) |
[0] |
Space |
\(x\) |
Normalized ContinuousSet [0 … 1] discretized by number of finite elements |
Phases |
\(p\) |
[‘Liq’] |
Components |
\(j\) |
[‘H2O’, ‘NaCl’]* |
*Solute depends on the imported property model; example shown here is for the NaCl property model.
Note
Everything below this section is pending since the 1D-RO model is currently under development.
Variables
Refer to the Variables section in the 0DRO model.
Equations
Refer to the Equations section in the 0DRO model.
Class Documentation
- class watertap.unit_models.reverse_osmosis_1D.ReverseOsmosis1D(*args, **kwds)
- Parameters
rule (function) – A rule function or None. Default rule calls build().
concrete (bool) – If True, make this a toplevel model. Default - False.
ctype (class) – Pyomo ctype of the block. Default - pyomo.environ.Block
default (dict) –
Default ProcessBlockData config
- Keys
- dynamic
Indicates whether this model will be dynamic or not. default = False. Membrane units do not yet support dynamic behavior.
- has_holdup
Indicates whether holdup terms should be constructed or not. default - False. Membrane units do not have defined volume, thus this must be False.
- property_package
Property parameter object used to define property calculations, default - useDefault. Valid values: { useDefault - use default package from parent model or flowsheet, PhysicalParameterObject - a PhysicalParameterBlock object.}
- property_package_args
A ConfigBlock with arguments to be passed to a property block(s) and used when constructing these. default - None. Valid values: { see property package for documentation.}
- material_balance_type
Indicates what type of mass balance should be constructed, default - MaterialBalanceType.useDefault. Valid values: { MaterialBalanceType.useDefault - refer to property package for default balance type **MaterialBalanceType.none - exclude material balances, MaterialBalanceType.componentPhase - use phase component balances, MaterialBalanceType.componentTotal - use total component balances, MaterialBalanceType.elementTotal - use total element balances, MaterialBalanceType.total - use total material balance.}
- energy_balance_type
Indicates what type of energy balance should be constructed. default - EnergyBalanceType.useDefault. Valid values: { EnergyBalanceType.useDefault - refer to property package for default balance type **EnergyBalanceType.none - exclude energy balances, EnergyBalanceType.enthalpyTotal - single enthalpy balance for material, EnergyBalanceType.enthalpyPhase - enthalpy balances for each phase, EnergyBalanceType.energyTotal - single energy balance for material, EnergyBalanceType.energyPhase - energy balances for each phase.}
- momentum_balance_type
Indicates what type of momentum balance should be constructed, default - MomentumBalanceType.pressureTotal. Valid values: { MomentumBalanceType.none - exclude momentum balances, MomentumBalanceType.pressureTotal - single pressure balance for material, MomentumBalanceType.pressurePhase - pressure balances for each phase, MomentumBalanceType.momentumTotal - single momentum balance for material, MomentumBalanceType.momentumPhase - momentum balances for each phase.}
- concentration_polarization_type
Options to account for concentration polarization.
default -
ConcentrationPolarizationType.calculated
Configuration Options
Description
ConcentrationPolarizationType.none
Simplifying assumption to ignore concentration polarization
ConcentrationPolarizationType.fixed
Specify an estimated value for the concentration polarization modulus
ConcentrationPolarizationType.calculated
Allow model to perform calculation of membrane-interface concentration
- mass_transfer_coefficient
Options to account for mass transfer coefficient.
default -
MassTransferCoefficient.calculated
Configuration Options
Description
MassTransferCoefficient.none
Mass transfer coefficient not used in calculations
MassTransferCoefficient.fixed
Specify an estimated value for the mass transfer coefficient in the feed channel
MassTransferCoefficient.calculated
Allow model to perform calculation of mass transfer coefficient
- has_pressure_change
Indicates whether terms for pressure change should be constructed, default - False. Valid values: { True - include pressure change terms, False - exclude pressure change terms.}
- pressure_change_type
Indicates what type of pressure change calculation will be made. To use any of the
pressure_change_type
options to account for pressure drop, the configuration keywordhas_pressure_change
must also be set toTrue
. Also, if a value is specified for pressure change, it should be negative to represent pressure drop.default -
PressureChangeType.fixed_per_stage
Configuration Options
Description
PressureChangeType.fixed_per_stage
Specify an estimated value for pressure drop across the membrane feed channel
PressureChangeType.fixed_per_unit_length
Specify an estimated value for pressure drop per unit length across the membrane feed channel
PressureChangeType.calculated
Allow model to perform calculation of pressure drop across the membrane feed channel
- area_definition
Argument defining whether area variable should be spatially variant or not. default - DistributedVars.uniform. Valid values: { DistributedVars.uniform - area does not vary across spatial domain, DistributedVars.variant - area can vary over the domain and is indexed by time and space.}
- transformation_method
Discretization method to use for DAE transformation. See Pyomo documentation for supported transformations.
- transformation_scheme
Discretization scheme to use when transforming domain. See Pyomo documentation for supported schemes.
- finite_elements
Number of finite elements to use when discretizing length domain (default=20)
- collocation_points
Number of collocation points to use per finite element when discretizing length domain (default=5)
- has_full_reporting
Level of reporting results. default - False. Valid values: { False - include minimal reporting of results, True - report additional properties of interest that aren’t constructed by the unit model by default. Also, report averaged expression values
initialize (dict) – ProcessBlockData config for individual elements. Keys are BlockData indexes and values are dictionaries described under the “default” argument above.
idx_map (function) – Function to take the index of a BlockData element and return the index in the initialize dict from which to read arguments. This can be provided to overide the default behavior of matching the BlockData index exactly to the index in initialize.
- Returns
(ReverseOsmosis1D) New instance
- class watertap.unit_models.reverse_osmosis_1D.ReverseOsmosis1DData(component)[source]
Standard 1D Reverse Osmosis Unit Model Class.
- build()[source]
Build 1D RO model (pre-DAE transformation).
- Parameters
None –
- Returns
None
- initialize(feed_side_args=None, permeate_side_args=None, permeate_block_args=None, outlvl=0, solver=None, optarg=None, fail_on_warning=False, ignore_dof=False)[source]
Initialization routine for 1D-RO unit.
- Keyword Arguments
feed_side_args – a dict of arguments to be passed to the property package(s) of the feed_side to provide an initial state for initialization (see documentation of the specific property package)
permeate_side_args – a dict of arguments to be passed to the property package(s) of the permeate_side to provide an initial state for initialization (see documentation of the specific property package)
permeate_block_args – a dict of arguments to be passed to the property package(s) of the final permeate StateBlock to provide an initial state for initialization (see documentation of the specific property package)
outlvl – sets output level of initialization routine
solver – str indicating which solver to use during initialization (default = None, use default solver)
optarg – solver options dictionary object (default=None, use default solver options)
fail_on_warning – boolean argument to fail or only produce warning upon unsuccessful solve (default=False)
ignore_dof – boolean argument to ignore when DOF != 0 (default=False)
- Returns
None