Thermodynamics
Start by adding a Thermodynamic System, which will be used to compute the transport and thermodynamic properties of the coolant.
1
In the Model Builder window, right-click  Global Definitions and choose Thermodynamics >  Thermodynamic System. This opens the Thermodynamic System Wizard. In the first step, select the phases in the system. You can choose among the following systems:
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Gas
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Liquid
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Vapor-liquid
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Vapor-liquid-liquid
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Liquid-liquid
2
In the Select System window, choose Vapor-liquid from the list. In this case a two-phase system is needed to study the phase envelope of the coolant mixture. When solving for the heat transfer in the test apparatus, the mixture will be assumed to remain in the liquid phase.
3
Click  Next in the window toolbar to proceed to the next step of the wizard.
4
In the Select Species window, locate the Species list and type ethylene glycol in the Species filter field. While typing, the available species are dynamically updated in the list below.
5
Select ethylene glycol (107-21-1, C2H6O2) in the list of available species and click  Add Selected to add it to the Selected species list.
6
Perform the same steps (step 4 and 5) to add water, namely:
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Type water in the Species filter field.
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Select water (7732-18-5, H2O) in the list of available species.
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Click  Add selected.
7
Click  Next in the window toolbar to proceed to the last step of the Thermodynamic System Wizard. Here you select the models used to compute thermodynamic and transport properties.
8
In the Select Thermodynamic Model window, choose UNIFAC VLE from the list. Then check the Advanced options checkbox and set Liquid volume to Ideal mixing. Complete the wizard by clicking  Finish in the window toolbar.
This adds a Thermodynamic System node under  Thermodynamics in the Model Builder window. The default label (name) of the system is Vapor-Liquid System 1, indicating the phases in the system.
For more information on how to choose the thermodynamic model see Selecting the Right Thermodynamic Model in the Chemical Reaction Engineering Module User’s Guide.