On opening a Scenario in Simulator the main chart will appear. This contains:

• A chart title. This is the title of the Scenario you set in Excel.
• Experimental data for the Scenario that was included on the data sheet in Excel. The data appear as points on the chart.
• Imposed profiles for parameters that were set on the data sheet. These appear as points and lines on the chart.
• The y-axis is automatically scaled so that all data and initial values in the model will fit on the chart.
• The x-axis will show the time of the simulation in units that were set on the data sheet.
• The legend of the chart will show all the data series being plotted plus those variables you set to be plotted on the process sheet.

Check that the experimental data and imposed profiles for the Scenario appear on the chart. as you intended. You can use the y-axis controls to re-scale the chart and rollover on points to check their values.

• Open Reactions and check that the chemistry in the model is as expected.
• Open Parameters and check that the initial values for the Scenario are as expected.
• Open Phases to check the model has initialized as expected. For example, check that the volumes, temperatures and compositions of the phases in the model are as intended.
• If any errors are found in the model set up it is recommended that these are corrected in Excel before proceeding further with simulation work.

One of the main problems inherent with automated parameter fitting is that the algorithm can sometimes find what is called a 'local minimum'. A local minimum can give the wrong values of fitted parameters and it will appear to new users as though 'fitting doesn't work'.

As a user you want to find the 'global minimum', i.e. the actual kinetic parameters for your process. To give yourself the best chance of being successful, it is recommended (and often essential) that a degree of manual fitting is undertaken in Simulator using the Reactions and Parameters windows. This will provide the fitting algorithm better initial estimates of the parameters you want fitted. More on manual fitting.

In process modeling you are often required to make estimates for parameter values. Testing whether the result of a simulation is strongly dependent, weakly dependent or even independent of a parameter's value can be useful in determining the sensitivity of the process and the accuracy to which a parameter's value needs to be known to give reliable results. You can do quick sensitivity tests in Simulator using Set Reactions and Set Parameters. Useful background on the importance of sensitivity analysis is given in the following publication: Good Practice Guidelines, "The Use of Computers by Chemical Engineers", IChemE Computer Aided Process Engineering (CAPE) Subject Group, UK, July 1999.