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International Association of the Properties of Water and Steam IAPWS-95

pair: idaes.generic_models.properties.iapws95; Iapws95StateBlock

idaes.generic_models.properties.iapws95

Accurate and thermodynamically consistent steam properties are provided for the IDAES framework by implementing the International Association for the Properties of Water and Steam's "Revised Release on the IAPWS Formulation 1995 for the Thermodynamic Properties of Ordinary Water Substance for General and Scientific Use." <iapws-2016> Non-analytic terms designed to improve accuracy very near the critical point were omitted, because they cause a singularity at the critical point, a feature which is undesirable in optimization problems. The IDAES implementation provides features which make the water and steam property calculations amenable to rigorous mathematical optimization.

Please see the general Helmholtz documentation <technical_specs/model_libraries/generic/property_models/helmholtz:Pure Component Helmholtz EoS> for more information.

Example

The Heater unit model example <technical_specs/model_libraries/generic/unit_models/heater:Example>, provides a simple example for using water properties.

from idaes.generic_models.properties import iapws95 import pyomo.environ as pe # Pyomo environment from idaes.core import FlowsheetBlock, MaterialBalanceType from idaes.generic_models.unit_models import Heater

# Create an empty flowsheet and steam property parameter block. model = pe.ConcreteModel() model.fs = FlowsheetBlock(default={"dynamic": False}) model.fs.properties = iapws95.Iapws95ParameterBlock(default={ "phase_presentation":iapws95.PhaseType.LG, "state_vars":iapws95.StateVars.PH})

# Add a Heater model to the flowsheet. model.fs.heater = Heater(default={ "property_package": model.fs.properties, "material_balance_type": MaterialBalanceType.componentTotal})

# Setup the heater model by fixing the inputs and heat duty model.fs.heater.inlet[:].enth_mol.fix(4000) model.fs.heater.inlet[:].flow_mol.fix(100) model.fs.heater.inlet[:].pressure.fix(101325) model.fs.heater.heat_duty[:].fix(100*20000)

# Initialize the model. model.fs.heater.initialize()

Since all properties except the state variables are Pyomo Expressions in the water properties module, after solving the problem any property can be calculated in any state block. Continuing from the heater example, to get the viscosity of both phases, the lines below could be added.

mu_l = pe.value(model.fs.heater.control_volume.properties_out[0].visc_d_phase["Liq"]) mu_v = pe.value(model.fs.heater.control_volume.properties_out[0].visc_d_phase["Vap"])

For more information about how StateBlocks and PropertyParameterBlocks work see the StateBlock documentation <technical_specs/core/physical_property_class:Physical Property Package Classes>.

Expressions

The IAPWS-95 property package contains the standard expressions described in the general Helmholtz documentation <technical_specs/model_libraries/generic/property_models/helmholtz:Pure Component Helmholtz EoS>, but it also defines expressions for transport properties.

Expression Description
therm_cond_phase[phase] Thermal conductivity of phase (W/K/m)
visc_d_phase[phase] Viscosity of phase (Pa/s)
visc_k_phase[phase] Kinimatic viscosity of phase (m2/s)

Convenience Functions

htpx

Iapws95StateBlock Class

Iapws95StateBlock

Iapws95StateBlockData Class

Iapws95StateBlockData

Iapws95ParameterBlock Class

Iapws95ParameterBlock

Iapws95ParameterBlockData Class

Iapws95ParameterBlockData

References

International Association for the Properties of Water and Steam (2016). IAPWS R6-95 (2016), "Revised Release on the IAPWS Formulation 1995 for the Properties of Ordinary Water Substance for General Scientific Use," URL: http://iapws.org/relguide/IAPWS95-2016.pdf

Wagner, W., A. Pruss (2002). "The IAPWS Formulation 1995 for the Thermodynamic Properties of Ordinary Water Substance for General and Scientific Use." J. Phys. Chem. Ref. Data, 31, 387-535.

Wagner, W. et al. (2000). "The IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam," ASME J. Eng. Gas Turbines and Power, 122, 150-182.

Akasaka, R. (2008). "A Reliable and Useful Method to Determine the Saturation State from Helmholtz Energy Equations of State." Journal of Thermal Science and Technology, 3(3), 442-451.

International Association for the Properties of Water and Steam (2011). IAPWS R15-11, "Release on the IAPWS Formulation 2011 for the Thermal Conductivity of Ordinary Water Substance," URL: http://iapws.org/relguide/ThCond.pdf.

International Association for the Properties of Water and Steam (2008). IAPWS R12-08, "Release on the IAPWS Formulation 2008 for the Viscosity of Ordinary Water Substance," URL: http://iapws.org/relguide/visc.pdf.