PCDmanager Mixture Compound

[nrgeng]

(Q1) How to specify molecular weight for a mixture: (1) use molar proportional average MW or (2) add both MWs together? PCDmanager uses Method 2. Is there a problem using an average MW of 142.321 (Method 1) vs UNIFAC MW of 296.234 (Method 2)? Will this affect property estimates using UNIFAC? Molar to mass conversion? How to resolve?

(Q2) The <Component> panel calculates a Method 2 MW and gives a red-flagged preferred data check on the Formula. Can this flag be cleared or should it just be ignored?

(Q3) After configuring UNIFAC, the UNIFAC LLE and ASOG panels are automatically populated, but with the wrong functional groups. This occurs after clicking the <Generate all missing data from UNIFAC> Button.

[hkooijman]

(Q1) Currently, the UNIFAC method can not be used when a compound is actually a mixture, since (a) the method was intended to describe one molecule and (b) this would require us to extend the implementation to be able to use fractional group definitions. Best way to approach this when you only have two compounds is to set each up as a pure compound and then in the simulation mix them to the right composition.

(Q2) Please describe the concrete example with all details you are trying to do as to enable/ease trouble-shooting.

(Q3) <Generate missing data from UNIFAC> should not alter the UNIFAC group definition itself. Therefore please decribe/upload the exact steps in full detail that leads you to this problem

[nrgeng]

[hkooijman]

Q3: OK, this is a bit more clear, but the issue could be whether you save as pct or as txt file, and how you then open it again (as pct or txt). Still many possibilities and you need to be precise so that I can reproduce. This also means you better share the exact data entered or send me the pct or txt file you generated... I have exported and re-imported components from the standard chemsep pcd library and this worked fine.

Q4: again, w/o being precise with the component in question, I can not say whether there are or are not methods to estimate properties, for this is too generic to give an accurate answer.