COMSOL 6.4 - Global Definitions — Parameters and Variables

Global Definitions — Parameters and Variables

Next, you will load the model parameters from a text file. Alternatively, you could have created the parameters in the Parameter window directly. The file includes inlet temperature, shell pressure, reactor pressure, and so on. You will also import variable definitions from a variable text file. This could also have been defined manually.

The location of a file is based on the installation. For example, if the installation is on your hard drive, the file path might be similar to C:\Program Files\COMSOL\COMSOL64\applications\.

1

In the Model Builder window, under Global Definitions

, click Parameters 1

2

In the Settings window for Parameters 1

, locate the Parameters section.

3

Click Load from File

4

Browse to the model’s Application Libraries folder and double-click the file membrane_hda_parameters.txt.

Add variable definitions from a text file.

1

In the Model Builder window, under Component 1 (comp1) right-click Definitions

and choose Variables

2

Click the Load from File

3

Browse to the model’s Application Libraries folder and double-click the file membrane_hda_variables.txt.

The defined thermal function hF_mixture is used in the variable definition for the heat source Q_mem. The variables to be defined in Reaction Engineering interface are also used in some expressions. For example, in the orange-colored expression, re.F_C6H6 specifies the molar flow rate of benzene, which will be defined later in the Reaction Engineering interface. The reason for this variable expression being orange is that it includes expressions that are not yet defined. Once these expressions are defined in the Reaction Engineering interface, the orange color will disappear, unless there are errors in the units. The orange color signifies that COMSOL Multiphysics cannot get a consistent unit for an expression or that there is an undefined parameter or variable in an expression.