AixLib.Media.Steam

# .AixLib.Media.Steam

Package with model for pure steam water vapor

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

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