Skip to main content
M
mnori1-Visitor
1-Visitor
November 16, 2015
Question

Numerical issues with Symbolic Derivative Operators

  • November 16, 2015
  • 1 reply
  • 7874 views

In order to apply the classical Van der Walls Critical Isotherm Conditions to a  Carnahan-Staling based EOS, I make use of the derivative operators within a solve block.  I found discrepancy between the derivative evaluated by using the symbolic derivative and the expanded derivative ( calculated symbolically ). Furthermore the solve block does not converge with the symbolic derivatives, while it does ( "better" ) with the expanded derivative.

1 reply

R
RichardJ19-Tanzanite
19-Tanzanite
November 16, 2015

Please post a worksheet showing the problem. It's not possible to give you any kind of answer without a worksheet.

M
mnori1-VisitorAuthor
1-Visitor
November 17, 2015

In the attached worksheet, after the EOS contributions definitions, you could find the isotherm critical conditions non linear system: 1) Non linear system for only dispersion forces EOS using the symbolic derivative; 2) Non linear system including the EOS association contribution ( Wertheim's theory derived ) by using the explicit derivative 3) Non linear system including the EOS association contribution by using the symbolic derivative.

In the second attachment , you could find for instance the procedure for fitting the EOS parameters ( here the explicit derivatives calculated  even written a bit differently) for the pure compounds.

in the third attachment, similar procedure for not associating compounds.

S
StuartBruff23-Emerald V
23-Emerald V
November 17, 2015

Massimiliano Nori wrote:

In the attached worksheet, after the EOS contributions definitions, you could find the isotherm critical conditions non linear system: 1) Non linear system for only dispersion forces EOS using the symbolic derivative; 2) Non linear system including the EOS association contribution ( Wertheim's theory derived ) by using the explicit derivative 3) Non linear system including the EOS association contribution by using the symbolic derivative.

In the second attachment , you could find for instance the procedure for fitting the EOS parameters ( here the explicit derivatives calculated  even written a bit differently) for the pure compounds.

in the third attachment, similar procedure for not associating compounds.

Good Morning, Massimiliano

I've just had a look at Benzene.xmcd and there is an undefined variable error where it tries to access an element of the variable Benzene.  Where is Benzene defined - I can't see it in the worksheet?

Stuart

Terms & ConditionsCookie settingsAccessibility statement