[Bug] Heat Exchanger does not use property overridden properties internally

[magnuscarlsen]

When modelling a HX where one stream has enthalpy calculated with property override, the out enthalpy is not correctly calculated. This can be observed when the massflow * (enthalpy difference) is not the same in the hot and cold streams. To double check I have made a cooler heater model to the same out temperature and this gives the same heat transfer values as the heater, but still the same enthaply values out of the "hot hx" or the cooler.

The solution inspector for the HX indicate that internally the enthalpy ends up at value that is close to the "unoverriden" value, and not the overriden value that is then presented in the material stream following the HX. I think the problem is that the HX is not using the overrides in its interanal iterations, but use the original unoverriden values. (I think it calculates the overriden values, as the calculation time is 100 times longer).

See attached dwsim file. (the hot stream has property overrides, the cold one does not). Property overrides are needed for salinities above 12%.
In this case the last line in the HX property inspector shows 144 kJ/kg, the enthalpy directly following the HX is 133ish kJ/kg.

EnergyOutWithHeaterCooler.zip

[DanWBR]

@magnuscarlsen I'll take a look

[DanWBR]

hmmm this will require huge changes...

[DanWBR]

@magnuscarlsen there is a specific enthalpy calculation override procedure that can help you with your case. Check the "Peng Robinson EOS Fugacity and Enthalpy Override" sample. You use a global script to override the routine that runs as soon as the flowsheet is opened.