.Modelica.Media.Water.IF97_Utilities

Information

Package description

This package provides high accuracy physical properties for water according to the IAPWS/IF97 standard. It has been part of the ThermoFluid Modelica library and been extended, reorganized and documented to become part of the Modelica Standard library.

An important feature that distinguishes this implementation of the IF97 steam property standard is that this implementation has been explicitly designed to work well in dynamic simulations. Computational performance has been of high importance. This means that there often exist several ways to get the same result from different functions if one of the functions is called often but can be optimized for that purpose.

The original documentation of the IAPWS/IF97 steam properties can freely be distributed with computer implementations, so for curious minds the complete standard documentation is provided with the Modelica properties library. The following documents are included (in directory Modelica/Resources/Documentation/Media/Water/IF97documentation):

• IF97.pdf The standards document for the main part of the IF97.
• Back3.pdf The backwards equations for region 3.
• crits.pdf The critical point data.
• meltsub.pdf The melting- and sublimation line formulation (in IF97_Utilities.BaseIF97.IceBoundaries)
• surf.pdf The surface tension standard definition
• thcond.pdf The thermal conductivity standard definition
• visc.pdf The viscosity standard definition

Package contents

• Package BaseIF97 contains the implementation of the IAPWS-IF97 as described in IF97.pdf. The explicit backwards equations for region 3 from Back3.pdf are implemented as initial values for an inverse iteration of the exact function in IF97 for the input pairs (p,h) and (p,s). The low-level functions in BaseIF97 are not needed for standard simulation usage, but can be useful for experts and some special purposes.
• Function water_ph returns all properties needed for a dynamic control volume model and properties of general interest using pressure p and specific entropy enthalpy h as dynamic states in the record ThermoProperties_ph.
• Function water_ps returns all properties needed for a dynamic control volume model and properties of general interest using pressure p and specific entropy s as dynamic states in the record ThermoProperties_ps.
• Function water_dT returns all properties needed for a dynamic control volume model and properties of general interest using density d and temperature T as dynamic states in the record ThermoProperties_dT.
• Function water_pT returns all properties needed for a dynamic control volume model and properties of general interest using pressure p and temperature T as dynamic states in the record ThermoProperties_pT. Due to the coupling of pressure and temperature in the two-phase region, this model can obviously only be used for one-phase models or models treating both phases independently.
• Function hl_p computes the liquid specific enthalpy as a function of pressure. For overcritical pressures, the critical specific enthalpy is returned
• Function hv_p computes the vapour specific enthalpy as a function of pressure. For overcritical pressures, the critical specific enthalpy is returned
• Function sl_p computes the liquid specific entropy as a function of pressure. For overcritical pressures, the critical specific entropy is returned
• Function sv_p computes the vapour specific entropy as a function of pressure. For overcritical pressures, the critical specific entropy is returned
• Function rhol_T computes the liquid density as a function of temperature. For overcritical temperatures, the critical density is returned
• Function rhol_T computes the vapour density as a function of temperature. For overcritical temperatures, the critical density is returned
• Function dynamicViscosity computes the dynamic viscosity as a function of density and temperature.
• Function thermalConductivity computes the thermal conductivity as a function of density, temperature and pressure. Important note: Obviously only two of the three inputs are really needed, but using three inputs speeds up the computation and the three variables are known in most models anyways. The inputs d,T and p have to be consistent.
• Function surfaceTension computes the surface tension between vapour and liquid water as a function of temperature.
• Function isentropicEnthalpy computes the specific enthalpy h(p,s,phase) in all regions. The phase input is needed due to discontinuous derivatives at the phase boundary.
• Function dynamicIsentropicEnthalpy computes the specific enthalpy h(p,s,,dguess,Tguess,phase) in all regions. The phase input is needed due to discontinuous derivatives at the phase boundary. Tguess and dguess are initial guess values for the density and temperature consistent with p and s. This function should be preferred in dynamic simulations where good guesses are often available.

Version Info and Revision history

• First implemented: July, 2000 by Hubertus Tummescheit for the ThermoFluid Library with help from Jonas Eborn and Falko Jens Wagner
• Code reorganization, enhanced documentation, additional functions: December, 2002 by Hubertus Tummescheit and moved to Modelica properties library.

Contents

Revisions

Intermediate release notes during development

Currently the Events/noEvents switch is only implemented for p-h states. Only after testing that implementation, it will be extended to dT.