Defining Property Packages¶
Contents
Introduction¶
In order to create and use a property package using the IDAES Generic Property Package Framework, users must provide a definition for the material they wish to model. The framework supports two approaches for defining the property package, which are described below, both of which are equivalent in practice.
Property Parameters¶
Thermophysical property models all depend upon a set of parameters to describe the fundamental behavior of the system. For the purposes of the Generic Property Framework, these parameters are grouped into three types:
- Component-specific parameters - these are parameters that are specific to a given chemical species, and are defined in the parameter_data argument for each component and stored in the associated Component block. Examples of these parameters include those used to calculate the ideal, pure component properties.
- Phase-specific parameters - these are parameters that are specific to a given phase, and are defined in the parameter_data argument for each phase and stored in the associated Phase block. These types of parameters are relatively uncommon.
- Package-wide parameters - these are parameters that are not necessarily confined to a single phase or species, and are defined in the parameter_data argument of the overall property package and stored in the main Physical Parameter block. Examples of these types of parameters include binary interaction parameters, which involve multiple species and can be used in multiple phases.
Config Dictionary¶
The most common way to use the Generic Property Package Framework is to create an instance of the GenericParameterBlock component and provide it with a dictionary of configuration arguments, as shown below:
m = ConcreteModel()
m.fs = FlowsheetBlock()
m.fs.properties = GenericParameterBlock(default=config_dict)
Users need to populate config_dict with the desired options for their system as described in the other parts of this documentation. An example of a configuration dictionary for a benzene-toluene VLE system is shown below. For details on each configuration option, please see the relevant documentation.
config_dict = {
"components": {
'benzene': {
"dens_mol_liq_comp": Perrys,
"enth_mol_liq_comp": Perrys,
"enth_mol_ig_comp": RPP,
"pressure_sat_comp": RPP,
"phase_equilibrium_form": {("Vap", "Liq"): fugacity},
"parameter_data": {
"mw": 78.1136E-3, # [1]
"pressure_crit": 48.9e5, # [1]
"temperature_crit": 562.2, # [1]
"dens_mol_liq_comp_coeff": {'1': 1.0162*1e3, # [2] pg. 2-98
'2': 0.2655,
'3': 562.16,
'4': 0.28212},
"cp_mol_ig_comp_coeff": {'A': -3.392E1, # [1]
'B': 4.739E-1,
'C': -3.017E-4,
'D': 7.130E-8},
"cp_mol_liq_comp_coeff": {'1': 1.29E2, # [2]
'2': -1.7E-1,
'3': 6.48E-4,
'4': 0,
'5': 0},
"enth_mol_form_liq_comp_ref": 49.0e3, # [3]
"enth_mol_form_vap_comp_ref": 82.9e3, # [3]
"pressure_sat_comp_coeff": {'A': -6.98273, # [1]
'B': 1.33213,
'C': -2.62863,
'D': -3.33399}}},
'toluene': {
"dens_mol_liq_comp": Perrys,
"enth_mol_liq_comp": Perrys,
"enth_mol_ig_comp": RPP,
"pressure_sat_comp": RPP,
"phase_equilibrium_form": {("Vap", "Liq"): fugacity},
"parameter_data": {
"mw": 92.1405E-3, # [1]
"pressure_crit": 41e5, # [1]
"temperature_crit": 591.8, # [1]
"dens_mol_liq_comp_coeff": {'1': 0.8488*1e3, # [2] pg. 2-98
'2': 0.26655,
'3': 591.8,
'4': 0.2878},
"cp_mol_ig_comp_coeff": {'A': -2.435E1,
'B': 5.125E-1,
'C': -2.765E-4,
'D': 4.911E-8},
"cp_mol_liq_comp_coeff": {'1': 1.40E2, # [2]
'2': -1.52E-1,
'3': 6.95E-4,
'4': 0,
'5': 0},
"enth_mol_form_liq_comp_ref": 12.0e3, # [3]
"enth_mol_form_vap_comp_ref": 50.1e3, # [3]
"pressure_sat_comp_coeff": {'A': -7.28607, # [1]
'B': 1.38091,
'C': -2.83433,
'D': -2.79168}}}},
"phases": {'Liq': {"type": LiquidPhase,
"equation_of_state": ideal},
'Vap': {"type": VaporPhase,
"equation_of_state": ideal}},
"state_definition": FcPh,
"state_bounds": {"flow_mol_comp": (0, 1000),
"temperature": (273.15, 450),
"pressure": (5e4, 1e6),
"enth_mol": (1e4, 2e5)},
"pressure_ref": 1e5,
"temperature_ref": 300,
"phases_in_equilibrium": [("Vap", "Liq")],
"phase_equilibrium_formulation": {("Vap", "Liq"): smooth_VLE},
"temperature_bubble": bubble_temp_ideal,
"temperature_dew": dew_temp_ideal,
"pressure_bubble": bubble_press_ideal,
"pressure_dew": dew_press_ideal}
Data Sources:
- The Properties of Gases and Liquids (1987), 4th edition, Chemical Engineering Series - Robert C. Reid
- Perry’s Chemical Engineers’ Handbook 7th Ed. (converted to J/mol.K, mol/m^3)
- Engineering Toolbox, https://www.engineeringtoolbox.com, Retrieved 1st December, 2019
Class Definition¶
Alternatively, the IDAES Generic Property Package Framework supports defining classes derived from the IDAES GenericParameterData with methods for defining configuration options and parameters.
Users can define two methods which are called automatically when an instance of the property package is created:
- configure, which defines the users selection of sub-models, and
- parameters, which defines the parameters necessary for the selected property methods.
A basic outline of a user defined Property Parameter Block is shown below.
@declare_process_block_class("UserParameterBlock")
class UserParameterData(GenericParameterData):
def configure(self):
# Set configuration options
self.config.option_1 = value
def parameters(self):
# Define parameters
self.param_1 = Var(index_set, initialize=value)
Users should populate the configure and parameters methods as discussed below.
Configure¶
The ‘configure` method is used to assign values to the configuration arguments, using the format self.config.option_name = value.
Parameters¶
The parameters method is used to construct all the parameters associated with the property calculations and to specify values for these. The list of necessary parameters is based on the configuration options and the selected methods. Each method lists their necessary parameters in their documentation. Users need only define those parameters required by the options they have chosen.