Stability Testing

[qingqi-code]

Dear Ali,

I am very grateful to study PVTtool. Here I have a question. When I run code of the 'testcase2':

% test case
% liquid-two-phase phase transition
clc; clear;
% Define the components and load pure physsical properties
[component, comp_flag] = addComponents({'CH4', 'C2H6', 'C4H10', ...
'C6H14', 'C10H22', 'C15H32'});
% Define the thermodynamic models
T0 = 300; % [K]
p0 = 100e5; % [Pa]
thermo1 = addThermo();
thermo1.EOS = @PREOS;
mixture1 = addMixture(component, T0, p0);
% Define flash options
options.accuracy = 1e-7;
options.iteration = 100;
% Negative flash
[vapor_y, liquid_x, vapor_frac] = ...
        vleflashnegative(mixture1, thermo1, options)
%mixture1.temperature=T_range(i);
[liquid_z, vapor_z, fugacity, HR] = PREOS(mixture1, thermo1)    

[s1, sl, sv] = stabilityTest(mixture1, thermo1)

I found that the result is:

vapor_y =

    0.8653    0.1097    0.0198    0.0048    0.0004    0.0000


liquid_x =

    0.4053    0.1472    0.1165    0.1114    0.1099    0.1097


vapor_frac =

   -0.5188


liquid_z =

    0.5924


vapor_z =

    0.5924


fugacity =

    1.9419    0.3795    0.0352    0.0037    0.0001    0.0000


HR =

  -3.0503e+04


s1 =

     1     1


sl =

    0.9910


sv =

    1.0000

The problem is

s1 =

     1     1

that means it converged to trivial solution. If so, the system is single-phase but the simulation gives
me two phase data. I think this code did not implement stability analysis to flash calculation directly.
If it is problem, I would be happy to help modify this model.

Thank you so much.

[simulkade]

Hi @qingqi-code
apologies for the late reply. You are right; i have not incorporated the stability test in the flash calculation function. I've been looking for some time to pay some attentions to this package, which is becoming more and more hard to find :-)
You are more than welcome to make changes and improve the code.