.BuildingSystems.Media.Steam

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 BuildingSystems.Media.Steam.specificEnthalpy and BuildingSystems.Media.Steam.specificEntropy (both "forward" functions), as well as their "backward" inverse functions BuildingSystems.Media.Steam.temperature_ph and BuildingSystems.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 BuildingSystems.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.

Kathryn Hinkelman, Saranya Anbarasu, Michael Wetter, Antoine Gautier, Wangda Zuo. 2022. “A Fast and Accurate Modeling Approach for Water and Steam Thermodynamics with Practical Applications in District Heating System Simulation,” Energy, 254(A), pp. 124227. 10.1016/j.energy.2022.124227

Kathryn Hinkelman, Saranya Anbarasu, Michael Wetter, Antoine Gautier, Baptiste Ravache, Wangda Zuo 2022. “Towards Open-Source Modelica Models For Steam-Based District Heating Systems.” Proc. of the 1st International Workshop On Open Source Modelling And Simulation Of Energy Systems (OSMSES 2022), Aachen, German, April 4-5, 2022. 10.1109/OSMSES54027.2022.9769121

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

Revisions

• September 29, 2023, by Kathryn Hinkelman:
  Added publication references.
• March 10, 2023, by Saranya Anbarasu:
  Changed the variable type definition of pHat and THat from absolute to Modelica.Units.SI.PressureDifference and Modelica.Units.SI.TemperatureDifference to prevent min/max assertion errors during initilization.
• May 9, 2022, by David Blum:
  In function rho_pT, created and used new function extending Modelica.Media.Water.IF97_Utilities.BaseIF97.Basic.g2 with an annotation smoothOrder=2. This is to specifically pass on the smoothOrder=2 annotion placed on rho_pT to the g2 function.
• 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.