AE solver with bounded values for variables.

From: kheder (kheder_at_insa-rouen.fr)
Date: 03/18/05 

Date: Fri, 18 Mar 2005 18:44:11 +0100

Hi,

I'm using the nleq2 code to solve a system G(Y) =0 of algebraic equations
(see http://www.zib.de/Numerik/numsoft/CodeLib/codes/nleq2/) . The G(Y) = 0
is resulting from the modelling of a distillation column. Thus some
components Y(i) represents molar fraction variables (MFV) in the column and
their values must be always in [0, 1]. When a MFV is negative the program
will stop because some procedures (bubble and dew temperatures .) will face
illogical operations (like division by zero) or divergence.

The problem I face is in the way that nleq2 changing the Y(i) values during
its iterations. All guess values which I use to initiate the resolution are
good (MFV are inside [0, 1]), but when nleq2 begins its iterations, it
starts to change some MFV into negative values and then the resolution is
stopped.

My problem could be solved if I could find an algebraic equations (non
linear) solver witch accepts to consider some variables to vary inside
defined boundaries.

I hope you can help me.

Thanks

PS.

I have to use a numerical Jacobian matrix.