How to setup a simple RO model
The example below shows how to setup and initialize a simple RO unit model.
from pyomo.environ import ConcreteModel
from idaes.core import FlowsheetBlock
from idaes.core.util.scaling import calculate_scaling_factors
from watertap.property_models.NaCl_prop_pack import NaClParameterBlock
from watertap.unit_models.reverse_osmosis_0D import ReverseOsmosis0D
from watertap.unit_models.reverse_osmosis_0D import ConcentrationPolarizationType
from watertap.unit_models.reverse_osmosis_0D import MassTransferCoefficient
# Create a concrete model, flowsheet, and NaCl property parameter block.
m = ConcreteModel()
m.fs = FlowsheetBlock(dynamic=False)
m.fs.properties = NaClParameterBlock()
# Add an RO unit to the flowsheet.
m.fs.unit = ReverseOsmosis0D(
property_package=m.fs.properties,
concentration_polarization_type=ConcentrationPolarizationType.none,
mass_transfer_coefficient=MassTransferCoefficient.none,
has_pressure_change=False)
# Specify system variables.
m.fs.unit.inlet.flow_mass_phase_comp[0, 'Liq', 'NaCl'].fix(0.035) # mass flow rate of NaCl (kg/s)
m.fs.unit.inlet.flow_mass_phase_comp[0, 'Liq', 'H2O'].fix(0.965) # mass flow rate of water (kg/s)
m.fs.unit.inlet.pressure[0].fix(50e5) # feed pressure (Pa)
m.fs.unit.inlet.temperature[0].fix(298.15) # feed temperature (K)
m.fs.unit.area.fix(50) # membrane area (m^2)
m.fs.unit.A_comp.fix(4.2e-12) # membrane water permeability (m/Pa/s)
m.fs.unit.B_comp.fix(3.5e-8) # membrane salt permeability (m/s)
m.fs.unit.permeate.pressure[0].fix(101325) # permeate pressure (Pa)
# Set scaling factors for component mass flowrates.
m.fs.properties.set_default_scaling('flow_mass_phase_comp', 1, index=('Liq', 'H2O'))
m.fs.properties.set_default_scaling('flow_mass_phase_comp', 1e2, index=('Liq', 'NaCl'))
# Calculate scaling factors.
calculate_scaling_factors(m)
# Initialize the model.
m.fs.unit.initialize()