.AixLib.DataBase.Media.Refrigerants.ThermodynamicStatePropertiesBaseDataDefinition

Information

This record is a base data definition for fitting coefficients of the thermodynamic state properties depending on two independent state variables. These thermodynamic state properties are given as fitted formulas in order to reduce the overall computing time of the refrigerant model. Therefore, the fitting approach is based on "Fast_Propane" model developed by Sangi et al..

Sangi et al. used the following fitting approaches, which are also implemented within AixLib.Media.Refrigerants.Interfaces.TemplateHybridTwoPhaseMediumRecord:

"Formulas for calculating thermodynamic properties" cellspacing="0" cellpadding="3" border="1" width="80%" style= "border-collapse:collapse;">

Temperature_ph

First Input

First input required to calculate temperature by pressure and specific enthalpy

Second Input

Second input required to calculate temperature by pressure and specific enthalpy

Temperature_ps

First Input

First input required to calculate temperature by pressure and specific entropy

Second Input

Second input required to calculate temperature by pressure and specific entropy

Density_pT

First Input

First input required to calculate density by pressure and temperature

Second Input

Second input required to calculate density by pressure and temperature

Functional approach

Functional approach of calculating supercooled and superheated region

As it can be seen, the fitted formulas consist basically of the coefficient ci as well as of the parameters Meani and Stdi. These coefficients are the fitting coefficients and must be obtained during a fitting procedure. While the fitting procedure, the formulas presented above are fitted to external data (e.g. obtained from measurements or external media libraries) and the fitting coefficients are determined.

Assumptions and limitations

The fitting procedure is performed for a predefined range of the external data that is given in terms of, for example, temperature and pressure. As a consequence, the fitting coefficients are also just valid within the predefined range of external data.

References

Sangi, Roozbeh; Jahangiri, Pooyan; Klasing, Freerk; Streblow, Rita; Müller, Dirk (2014): A Medium Model for the Refrigerant Propane for Fast and Accurate Dynamic Simulations. In: The 10th International Modelica Conference. Lund, Sweden, March 10-12, 2014: Linköping University Electronic Press (Linköping Electronic Conference Proceedings), S. 1271–1275

Revisions

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