.MultiPhaseMixture.Information.Limitations.Tool

Information

Tool issues

Following limitations have been observed for different tools:

Not possible to calculate iteration start values from a property model. (Dymola 2016)

This limitation is severe if a model contains iteration variables that are not equal to a model’s start value parameters. If the specific enthalpy is an iteration variable it should be calculated from the given start value parameters as illustrated in the code below:

parameter  SpecificEnthalpy h_start (fixed=false)  annotation(Evaluate=true);
SpecificEnthalpy h(start=h_start);
Medium.MultiPhaseProperties
    flash_init(Z=Z_start,p=p_start,T=T_start,
    presentPhases=presentPhases,
   presentPhasesStatus=presentPhasesStatus,
    init(p=p_start, x=fill(Z_start, Medium.nP)),
    inputs=MultiPhaseMixture.Interfaces.Inputs.pTX)
initial equation 
  h_start=flash.h;
Not possible to calculate structural parameters from a function using an external object. (Dymola 2016)

This limitation requires that the user manually specify the number of phases and compounds in the property declaration.

presentPhaseIndex can't be an Integer (Dymola 2016)

presentPhaseIndex in MultiPhaseMixture.Templates.ExternalTwoPhaseMixture.Auxilary.Properties was changed to a real variable due to Dymola has currently an limitation of tearing with integers. I.e. before it did not work to calculate a property by iteration due to it choosed to use presentPhaseIndex as an iteration variable which was an integer = translation error in Dymola.


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