packageSteam

Information

This medium package models water vapor (pure steam, region 2, quality=1).

Thermodynamic properties are calculated primarily in terms of pressure and temperature. For thermodynamic property functions, the IAPWS-IF97 formulations are adapted, and approximate relationships are provided for commonly used functions to improve computational efficiency and provide backward compatability.

Detailed functions from Modelica.Media.Water.WaterIF97_R2pT are generally used, except for IBPSA.Media.Steam.specificEnthalpy and IBPSA.Media.Steam.specificEntropy (both "forward" functions), as well as their "backward" inverse functions IBPSA.Media.Steam.temperature_ph and IBPSA.Media.Steam.temperature_ps, which are numerically consistent with the forward functions. The following modifications were made relative to the Modelica.Media.Water.WaterIF97_R2pT medium package:

1. Analytic expressions for the derivatives are provided for all thermodynamic property functions.
2. The implementation is generally simpler in order to increase the likelihood of more efficient simulations.

Limitations

• The valid temperature range is 100°C ≤ T ≤ 160°C, and the valid pressure range is 100 kPa ≤ p ≤ 550 kPa.
• When phase change is required, this model is to be used in combination with IBPSA.Media.Water for the liquid phase (quality=0). Please note that the maximum temperature for liquid water is T_max=130°C. This is suitable for real-world condensate return and boiler feedwater systems, which are typically vented to the atmosphere with steam contained via steam traps (thus, T_max=100°C for the condensate or feedwater in properly functioning systems).

Applications

This model is intended for first generation district heating systems and other steam heating processes involving low and medium pressure steam.

References

W. Wagner et al., “The IAPWS industrial formulation 1997 for the thermodynamic properties of water and steam,” J. Eng. Gas Turbines Power, vol. 122, no. 1, pp. 150–180, 2000.

Parameters

Contents

Name	Description
ThermodynamicState	Thermodynamic state variables
BaseProperties	Base properties (p, d, T, h, u, R, MM) of water
density	Returns density
dynamicViscosity	Return dynamic viscosity
molarMass	Return the molar mass of the medium
pressure	Return pressure
saturationPressure	Return saturation pressure of condensing fluid
saturationTemperature	Return saturation temperature
specificEnthalpy	Returns specific enthalpy
specificEntropy	Return specific entropy
specificInternalEnergy	Return specific internal energy
specificHeatCapacityCp	Specific heat capacity at constant pressure
specificHeatCapacityCv	Specific heat capacity at constant volume
specificGibbsEnergy	Specific Gibbs energy
specificHelmholtzEnergy	Specific Helmholtz energy
setState_dTX	Return the thermodynamic state as function of d and T
setState_pTX	Return the thermodynamic state as function of p and T
setState_phX	Return the thermodynamic state as function of p and h
setState_psX	Return the thermodynamic state as function of p and s
temperature	Return temperature
thermalConductivity	Return thermal conductivity
density_derh_p	Density derivative by specific enthalpy
density_derp_h	Density derivative by pressure
isentropicExponent	Return isentropic exponent
isothermalCompressibility	Isothermal compressibility of water
isobaricExpansionCoefficient	Isobaric expansion coefficient of water
isentropicEnthalpy	Isentropic enthalpy
GasPropertiesprotected	Coefficient data record for properties of perfect gases
g2protected	Gibbs function for region 2: g(p,T)
temperature_phprotected	Return temperature from p and h, inverse function of h(p,T)
temperature_psprotected	Return temperature from p and s, inverse function of s(p,T)
rho_pTprotected	Density as function of temperature and pressure
pressure_dTprotected	Computes pressure as a function of density and temperature

Revisions

• April 13, 2021, by Kathryn Hinkelman:
  Changed pressure from constant to variable and reduced applicable pressure-temperature range to improve accuracy of polynomial approximations.
• October 30, 2020, by Kathryn Hinkelman:
  Complete new reimplementation to eliminate numerical inefficiencies and improve accuracy of property function calculations.