Reaction parameters that can be selected include: rate constants, equilibrium constants, activation energies (forward and reverse), reaction heats and reaction orders. Reaction parameters set on the process sheet (and not overridden on the Scenarios sheet) apply to all Scenarios.
Scenario parameters set on the process sheet have the same values in all Scenarios.
Scenario parameters that can be selected include any reaction parameters set on the Scenarios sheet.
Build your parameter list in the Select parameters to be fitted window using the Add and Remove buttons.
New in Scale-up Suite 2, you can take advantage of a new default setting with automatic parameter elimination. This will try to fit all of the parameters you select and then mark the ones that cannot be fitted to your data as either 'No sensitivity' or 'Low sensitivity'. It will also remove insensitive parameters from model fitting statistics and reports. More details are available in this KB article.
The parameters that may be fitted include reaction kinetics (usually defined on the process tab in an Excel model), scenario inputs / factors / parameters and all reaction and scenario parameters. The parameter list that is shown in the interface is set by the dropdown menu below the Add/Remove buttons.
In models where HPLC area or area percent data are used, relative response factors may also be fitted. There is also a checkbox to fit the logarithm of a parameter value; this may enhance convergence when dealing with a broad range of parameter values.
Each parameter you add to be fitted requires an initial (guessed) value and constraints on what the value is allowed to be.
About scenario parameters
Selecting which parameters to fit
The choice of parameters to be fitted will depend strongly on the goals and development stage of the project and the data available. For example, if one isothermal experiment was done, activation energies cannot be fitted since this requires data at more than one (and preferably several) temperatures.
The most common parameters to be fitted will be the rate constants and activation energies. Normally reaction heats and reaction orders are either known or can be estimated. Non-integer reaction orders indicate missing reactions from the reaction scheme and fitting of these is not usually recommended.
Show me more on the workflow of fitting kinetics.
Fitting the same scenario parameters in multiple scenarios
When fitting scenario parameters, data from only one Scenario should in general be selected, since normally, a different scenario parameter value is required for each Scenario. For example, when fitting heat transfer coefficients (UA values) for three different operating conditions in a vessel:
- Give each experiment a separate scenario and put the appropriate heat/cool data in a corresponding data sheet.
- Run three fits, selecting only one scenario at a time and running until a fit is achieved.
- When all three separate fits have been completed, Update the model.
- The model will then contain three different UA values (one for each Scenario).
- If you run all the Scenarios in Simulator you will see that each value has been fitted correctly.
Show me more on fitting workflows.