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Water Property Package

This package implements property relationships for pure water.

This water property package:
  • supports only H2O
  • supports liquid and vapor phases
  • is formulated on a mass basis
  • does not support dynamics
  • pressure-dependency of specific enthalpy is incorporated

Sets

Description Symbol Indices
Components j ['H2O']
Phases p ['Liq', 'Vap']

State variables

Description Symbol Variable Index Units
Component mass flowrate M_j flow_mass_phase_comp [p, j] \text{kg/s}
Temperature T temperature None \text{K}
Pressure P pressure None \text{Pa}

Properties

Description Symbol Variable Index Units
Mass density of pure water \rho dens_mass_phase [p] \text{kg/}\text{m}^3
Phase volumetric flowrate Q_p flow_vol_phase [p] \text{m}^3\text{/s}
Volumetric flowrate Q flow_vol None \text{m}^3\text{/s}
Specific enthalpy \widehat{H} enth_mass_phase [p] \text{J/kg}
Enthalpy flow H enth_flow_phase [p] \text{J/s}
Saturation pressure P_v pressure_sat None \text{Pa}
Specific heat capacity c_p cp_mass_phase [p] \text{J/kg/K}
Latent heat of vaporization h_{vap} dh_vap_mass None \text{J/kg}
Component mole flowrate N_j flow_mol_phase_comp [p, j] \text{mole/s}
Component mole fraction y_j mole_frac_phase_comp [p, j] \text{dimensionless}

Relationships

Description Equation
Component mass fraction x_j = \frac{M_j}{\sum_{j} M_j}
Mass density of liquid Equation 8 in Sharqawy et al. (2010)
Mass density of vapor* \rho = \frac{Pm}{nRT}
Volumetric flowrate Q = \frac{\sum_{j} M_j}{\rho}
Mass concentration C_j = x_j \cdotp \rho
Specific enthalpy of liquid Equations 25-27 in Nayar et al. (2016)
Specific enthalpy of vapor Equations 25-27 in Nayar et al. (2016) + h_{vap}
Enthalpy flow H = \sum_{j} M_j \cdotp \widehat{H}
Component mole flowrate N_j = \frac{M_j}{MW_j}
Component mole fraction y_j = \frac{N_j}{\sum_{j} N_j}
Saturation pressure Equation 6 in Nayar et al. (2016)
Specific heat capacity of liquid Equation 9 in Sharqawy et al. (2010)
Specific heat capacity of vapor Shomate equation from NIST WebBook
Latent heat of vaporization Equations 37 and 55 in Sharqawy et al. (2010)

* Derived from the ideal gas law

Scaling

This water property package includes support for scaling, such as providing default or calculating scaling factors for almost all variables. The only variables that do not have scaling factors are the component mass flowrate and the user will receive a warning if these are not set.

The user can specify the scaling factors for component mass flowrates with the following:

.. testsetup::

   from pyomo.environ import ConcreteModel
   from idaes.core import FlowsheetBlock


# relevant imports
import watertap.property_models.water_prop_pack as props
from idaes.core.util.scaling import calculate_scaling_factors

# relevant assignments
m = ConcreteModel()
m.fs = FlowsheetBlock(dynamic=False)
m.fs.properties = props.WaterParameterBlock()

# set scaling for component mass flowrate
m.fs.properties.set_default_scaling('flow_mass_phase_comp', 1, index=('Liq','H2O'))

# calculate scaling factors
calculate_scaling_factors(m.fs)

The default scaling factors are as follows:

  • 1e-2 for temperature
  • 1e-5 for pressure
  • 1e-3 for liquid mass density
  • 1 for vapor mass density
  • 1e-5 for the liquid specific enthalpy
  • 1e-6 for the vapor specific enthalpy
  • 1e-5 for saturation pressure
  • 1e-3 for the liquid specific heat capacity
  • 1e-3 for the vapor specific heat capacity
  • 1e-6 for latent heat of vaporization

Scaling factors for other variables can be calculated based on their relationships with the user-supplied or default scaling factors.

References

K.G. Nayar, M.H. Sharqawy, L.D. Banchik, and J.H. Lienhard V, "Thermophysical properties of seawater: A review and new correlations that include pressure dependence,"Desalination, Vol.390, pp.1 - 24, 2016. https://doi.org/10.1016/j.desal.2016.02.024

M.H. Sharqawy, J.H.L. V, S.M. Zubair, Thermophysical properties of seawater: a review of existing correlations and data, Desalination and Water Treatment. 16 (2010) 354–380. https://doi.org/10.5004/dwt.2010.1079. (2017 corrections provided at http://web.mit.edu/seawater)

F.J. Millero, R. Feistel, D.G. Wright, T.J. McDougall, The composition of Standard Seawater and the definition of the Reference-Composition Salinity Scale, Deep-Sea Research Part I. 55 (2008) 50–72. https://doi.org/10.1016/j.dsr.2007.10.001.

T.V. Bartholomew, M.S. Mauter, Computational framework for modeling membrane processes without process and solution property simplifications, Journal of Membrane Science. 573 (2019) 682–693. https://doi.org/10.1016/j.memsci.2018.11.067.

Water Gas Phase Thermochemistry Data, National Institute of Standards and Technology, 2021, https://webbook.nist.gov/cgi/cbook.cgi?ID=C7732185&Mask=1#Thermo-Gas.