Main.VLEWilson History

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March 25, 2013, at 10:33 AM by 69.169.188.188 -
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Attach:download.jpg [[Attach:txy_ebulliometer_files.zip | Download APM Python and MATLAB Files]]
March 25, 2013, at 10:32 AM by 69.169.188.188 -
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-> Attach:ebulliometer_results.png
March 25, 2013, at 10:31 AM by 69.169.188.188 -
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January 11, 2013, at 07:21 AM by 69.169.188.188 -
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December 26, 2012, at 09:09 PM by 69.169.188.188 -
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Using data from an ebulliometer, determine parameters for the Wilson activity coefficient model using the measured data for an ethanol-cyclohexane mixture at ambient pressure.  Use the results to determine whether there is:
to:
Using data from an [[http://en.wikipedia.org/wiki/Ebulliometer | ebulliometer]], determine parameters for the Wilson activity coefficient model using the measured data for an ethanol-cyclohexane mixture at ambient pressure.  Use the results to determine whether there is:
December 26, 2012, at 08:57 PM by 69.169.188.188 -
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Attach:thermo_wilson1.png Attach:thermo_wilson2.png
December 26, 2012, at 08:56 PM by 69.169.188.188 -
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Attach:thermo_molar_volume.png
December 26, 2012, at 08:52 PM by 69.169.188.188 -
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Attach:thermo_wilson3.png
December 26, 2012, at 08:51 PM by 69.169.188.188 -
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where ''y'_1_'''is the vapor mole fraction, ''P'' is the pressure, ''x'_1_''' is the liquid mole fraction, ''gamma'_1_''' is the activity coefficient that is different than 1.0 for non-ideal mixtures, and ''P'^sat^''_1_''' is the pure component vapor pressure. The same equation also applies to component 2 in the mixture with the corresponding equation with subscript 2.
to:
where ''y'_1_'''is the vapor mole fraction, ''P'' is the pressure, ''x'_1_''' is the liquid mole fraction, ''gamma'_1_''' is the activity coefficient that is different than 1.0 for non-ideal mixtures, and ''P'_1_''^sat^''' is the pure component vapor pressure. The same equation also applies to component 2 in the mixture with the corresponding equation with subscript 2.
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There are correlations for ''P'^sat^''_1_''' for many common pure components from BYU's DIPPR database. In this case ''P'^sat^''_1_''' is a function of temperature according to
to:
There are correlations for ''P'^sat^''_1_''' and density (''rho'') for many common pure components from BYU's DIPPR database. In this case ''P'_1_''^sat^''' is a function of temperature according to
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and density ''rho'' or molar volume ''v'' is also a function of temperature according to

Attach:thermo_density.png
December 26, 2012, at 08:47 PM by 69.169.188.188 -
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(:title Estimate Thermodynamic Parameters from Data:)
(:keywords VLE, wilson equation, nonlinear, optimization, engineering optimization, dynamic estimation, interior point, active set, differential, algebraic, modeling language, university course:)
(:description Case study on data reconciliation for thermodynamic properties using optimization techniques in engineering:)

!!!! Case Study on Thermodynamic Parameter Estimation

Using data from an ebulliometer, determine parameters for the Wilson activity coefficient model using the measured data for an ethanol-cyclohexane mixture at ambient pressure.  Use the results to determine whether there is:

* An [[http://en.wikipedia.org/wiki/Azeotrope | azeotrope]] in the system and, if so, at what composition
* The values of the [[http://en.wikipedia.org/wiki/Activity_coefficient | activity coefficients]] at the infinitely dilute compositions
** gamma'_1_' at x'_1_'=0
** gamma'_2_' at x'_1_'=1

The liquid and vapor compositions of this binary mixture are related by the following thermodynamic relationships

Attach:thermo_teenage_law.png

where ''y'_1_'''is the vapor mole fraction, ''P'' is the pressure, ''x'_1_''' is the liquid mole fraction, ''gamma'_1_''' is the activity coefficient that is different than 1.0 for non-ideal mixtures, and ''P'^sat^''_1_''' is the pure component vapor pressure. The same equation also applies to component 2 in the mixture with the corresponding equation with subscript 2.

The Wilson equation is used to predict the activity coefficients ''gamma'_2_''' and ''gamma'_2_''' over the range of liquid compositions.

Attach:thermo_wilson1.png

Attach:thermo_wilson2.png

There are correlations for ''P'^sat^''_1_''' for many common pure components from BYU's DIPPR database. In this case ''P'^sat^''_1_''' is a function of temperature according to

Attach:thermo_vapor_pressure.png

The number of degrees of freedom in a multi-component and multi-phase system is given by DOF = 2 + #Components - #Phases. In this case, there are two phases (liquid and vapor) and two components (ethanol and cyclohexane). This leads to two degrees of freedom that must be specified. In this case, we can chose to fix two of the four measured values for this system with either ''x'_1_''', ''y'_1_''', ''P'', or ''T''. It is recommended to fix the values of ''x'_1_''' and ''P'' as shown in the tutorial below.

!!!! Background on Parameter Estimation

A common application of optimization is to estimate parameters from experimental data. One of the most common forms of parameter estimation is the least squares objective with (model-measurement)^2 summed over all of the data points. The optimization problem is subject to the model equations that relate the model parameters or exogenous inputs to the predicted measurements. The model predictions are connected by common parameters that are adjusted to minimize the sum of squared errors.

!!!! Tutorial on Parameter Estimation

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