How to use a property model
The example below shows how to use a property model and display outputs for a state block. Property models allow users to model the chemical and physical properties of simple systems without the use of unit models.
# Import concrete model from Pyomo
from pyomo.environ import ConcreteModel
# Import flowsheet block from IDAES core
from idaes.core import FlowsheetBlock
# Import solver from IDAES core
from idaes.core.solvers import get_solver
# Import NaCl property model
import watertap.property_models.NaCl_prop_pack as props
# Import utility tool for calculating scaling factors
import idaes.core.util.scaling as iscale
# Create a concrete model, flowsheet, and NaCl property parameter block.
m = ConcreteModel()
m.fs = FlowsheetBlock(dynamic=False)
m.fs.properties = props.NaClParameterBlock()
# Build the state block and specify a time (0 = steady state).
m.fs.state_block = m.fs.properties.build_state_block([0], default={})
# Fully specify the system.
feed_flow_mass = 1
feed_mass_frac_NaCl = 0.035
feed_mass_frac_H2O = 1 - feed_mass_frac_NaCl
feed_pressure = 50e5
feed_temperature = 298.15
m.fs.state_block[0].flow_mass_phase_comp['Liq', 'NaCl'].fix(feed_flow_mass * feed_mass_frac_NaCl)
m.fs.state_block[0].flow_mass_phase_comp['Liq', 'H2O'].fix(feed_flow_mass * feed_mass_frac_H2O)
m.fs.state_block[0].pressure.fix(feed_pressure)
m.fs.state_block[0].temperature.fix(feed_temperature)
# Set scaling factors for component mass flowrates (variable * scaling factor should be between 0.01 and 100).
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'))
iscale.calculate_scaling_factors(m.fs)
# "Touch" build-on-demand variables so that they are created. If these are not touched before running the solver, the output would only display their initial values, not their actual values.
m.fs.state_block[0].dens_mass_phase['Liq']
m.fs.state_block[0].conc_mass_phase_comp['Liq', 'NaCl']
m.fs.state_block[0].flow_vol_phase['Liq']
m.fs.state_block[0].molality_phase_comp['Liq', 'NaCl']
m.fs.state_block[0].visc_d_phase['Liq']
m.fs.state_block[0].diffus_phase_comp['Liq', 'NaCl']
m.fs.state_block[0].enth_mass_phase['Liq']
m.fs.state_block[0].pressure_osm_phase['Liq']
# Create the solver object.
solver = get_solver()
# Solve the model and display the output.
solver.solve(m, tee=False)
m.fs.state_block[0].display()
A portion of the displayed output is shown below.
Block fs.state_block[0]
Variables:
flow_mass_phase_comp : Mass flow rate
Size=2, Index=fs.state_block[0].flow_mass_phase_comp_index, Units=kg/s
Key : Lower : Value : Upper : Fixed : Stale : Domain
('Liq', 'H2O') : 0.0 : 0.965 : None : True : True : NonNegativeReals
('Liq', 'NaCl') : 0.0 : 0.035 : None : True : True : NonNegativeReals
temperature : State temperature
Size=1, Index=None, Units=K
Key : Lower : Value : Upper : Fixed : Stale : Domain
None : 273.15 : 298.15 : 373.15 : True : True : NonNegativeReals
...