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mnori1-Visitor
1-Visitor
October 9, 2015
Solved

Solving Cubic EOS


Is possible by using a MathCAD function to solve cubic EOS with Cardano's Formula ? Is the Polyroot function based on numerical method ? What is polyroot default tollerance?

AlvaroDíazAnswer
12-Amethyst
October 13, 2015

Hi Massimiliano. You can try to translate into mathcad this:  http://www.egr.msu.edu/~lira/computer/EXCEL/PREOS.XLS

There also equate fugacitys to find the VLE points (with solver in excel, that's is stress.). I also use PR in mathcad, but using polyroots I have enough good numeric approximation, and (for me) don't needs Cardano formula.

Regards.

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8 replies

ValeryOchkov24-Ruby IV
24-Ruby IV
October 9, 2015

May be so:

Card.png

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    StuartBruff23-Emerald V
    23-Emerald V
    October 9, 2015

    Massimiliano Nori wrote:


    Is possible by using a MathCAD function to solve cubic EOS with Cardano's Formula ? Is the Polyroot function based on numerical method ? What is polyroot default tollerance?

    What's the problem you're trying to solve and why do you want Cardano's formula (method?) specifically? 

    If you're concerned about numerics then, as Valery showed, the symbolic processor will handle cubics.  Here's Prime's solution to the canonical cubic example ..

    Stuart

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      mnori1-VisitorAuthor
      1-Visitor
      October 12, 2015


      I would like to apply this method as alternative to Polyroot for calculating "Andrews bell" for the vapour-liquid equilibrium of elemental mercury. The volumetric cubic equation ( e.g. Peng-Robinson ) is coupled with the isofugacity condition.

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      AlvaroDíaz12-AmethystAnswer
      12-Amethyst
      October 13, 2015

      Hi Massimiliano. You can try to translate into mathcad this:  http://www.egr.msu.edu/~lira/computer/EXCEL/PREOS.XLS

      There also equate fugacitys to find the VLE points (with solver in excel, that's is stress.). I also use PR in mathcad, but using polyroots I have enough good numeric approximation, and (for me) don't needs Cardano formula.

      Regards.

      Translate
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