Global Definitions
For water vapor we will use an ideal gas model, for liquid water we will use the IAPWS model.
Thermodynamic System for Water Vapor
1
In the Model Builder window, right-click Global Definitions and choose Thermodynamics > Thermodynamic System.
2
Click Next in the window toolbar.
3
In the Species list, select water (7732-18-5, H2O).
4
Click  Add Selected.
5
Click Next in the window toolbar.
6
From the Gas phase model list, choose Ideal gas.
7
Click Finish in the window toolbar.
8
In the Model Builder window, under Global Definitions > Thermodynamics right-click Gas System 1 (pp1) and choose Generate Material.
9
Click Next in the window toolbar three times (until you come to the Define Material window).
10
From the Component list, choose Global, and then click Finish.
Thermodynamic System For Liquid Water
1
In the Model Builder window, under Global Definitions right-click Thermodynamics and choose Thermodynamic System.
2
From the drop down list, choose Vapor–liquid.
3
Click Next in the window toolbar.
4
In the Species list, select water (7732-18-5, H2O).
5
Click  Add Selected.
6
Click Next in the window toolbar, and then Finish.
Properties of water
Some of the boundary conditions need physical properties of water. These can be generated from the Thermodynamic system.
1
In the Model Builder window, under Global Definitions > Thermodynamics right-click Vapor–liquid System 1 (pp2) and choose Species Property.
2
From the Amount base unit list, choose kg.
3
From the list, click  Add Selected, for each of:
-
Heat of vaporization (J/kg)
-
Ln vapor pressure, Pa
4
Click Next in the window toolbar.
5
Choose Liquid, and click Next.
6
Click  Add All, and click Next.
7
Click Finish in the window toolbar.
Vapor pressure of water
For convenience, a helper function is set up, allowing access to the vapor pressure of water from the generated function (which returns the natural logarithm of the vapor pressure measured in Pascal).
1
In the Home toolbar, click  Functions and choose Global > Analytic.
2
In the Settings window for Analytic, type Vapor pressure of water in the Label text field.
3
In the Function name text field, type pH2O.
4
Locate the Definition section. In the Expression text field, type exp(LnVaporPressure_water22(T)).
5
Locate the Units section. In the Function text field, type Pa.
6
In the table for arguments, locate the input for T, type K.
7
Locate the Plot Parameters section. In the table, enter the following settings:
Argument
Lower limit
Upper limit
T
273.15
373.15
8
Optionally, click Plot to inspect the vapor pressure curve.
Liquid Water Material
1
Right-click Vapor–liquid System 1 (pp2) and choose Generate Material.
2
From the list, choose Liquid, and click Next in the window toolbar, three times.
3
Click Finish.
Fluid in wick
Two cases will be investigated: a dry wick and a saturated wick. A material switch is added so that later interfaces can refer to this switch, which can either refer to vapor or liquid. Its state will be controlled from the Study nodes.
1
In the Model Builder window right-click Global Definitions > Materials and choose Material Switch .
2
In the Settings window for Material Switch, type Fluid in wick in the Label text field.
3
In the Model Builder window, right-click Gas: water 1 (pp1mat1) and choose Copy.
4
In the Model Builder window, right-click Fluid in wick (sw1) and choose Paste Material.
5
In the Model Builder window, right-click Liquid: water 1 (pp2mat1) and choose Copy.
6
In the Model Builder window, right-click Fluid in wick (sw1) and choose Paste Material.