Using TEC Materials

To Assign a TEC Material Device

Open the Material quick edit dialog. There are several methods:
- Left click on the part, and click the Edit icon on the context toolbar.
- Right click on the part, and click Edit...
- Right click on the part name under the Materials branch of the Design Study bar, and click Edit....
- Click Edit in the Materials context panel.
Select one or more parts. PCBs should be modeled as three dimensional volumes having the same physical size and shape as the actual PCB. No internal layers should be modeled within the PCB.
Select the database from the Material DB Name menu.
Select Thermoelectric Component from the Type menu.
Select the material from the Name menu.
Select the TEC surface, which is the surface where the target temperature is maintained. Activate the pop-out by clicking in the right-side column of the Cold Side Surface field. Click on the sensing surface of the device. (Surfaces co-planar to the sensing surface will be selected as well.)
Click Apply.

To Create a TEC Material Device

A few sample TEC material devices are included in the Default database. To modify any of these parameters, use the Material Editor to copy the original into a custom database, and modify the copy.

Note: TEC devices must be modeled in CAD using their correct physical dimensions.

The dimensions of Sample 1 are: 25 mm x 25 mm x 4 mm high
The dimensions ofSample 2 are: 40 mm x 40 mm x 4.1 mm high

To open the Material Editor, click Material Editor on the Materials context panel.
Click the List button.
Right click on a custom database, and select New material. Select Thermoelectric Comp.. Specify a Name.
Click the property button that is to be defined: 1. Define the TEC Geometry

This is the Geometry Factor (G), the units of G, and the number of couples contained within the device. G is the ratio of a pin cross-sectional area to the couple height.
1. Click the TEC Geometry button.
2. Enter the units of the Geometry Factor.
3. Enter the value of G.
4. Enter the Number of Couples.
5. Click Apply to save the value.
2. Define the Control Method

This defines the mode of operation of the TEC device. The default choice is "Tcold", which defines the TEC device to have a cooling effect with a target cold temperature.
1. Click the Control Method button.
2. Select the control method:
  - TCold: target cold temperature. The TEC device removes heat from the user-defined TEC surface to maintain this temperature. This is the control method for cooling a device.
  - THot: target hot temperature. The TEC device adds heat to the user-defined TEC surface to maintain the temperature. This is the control method for heating a device.
  - Voltage: Use if only the Voltage going to the TEC device is controlled.
  - Current: Use if only the current going to the TEC device is controlled.
  - Power: Use if the power going to the TEC device is controlled.
3. Click Apply to save the value.
3. (Optional Step) Define Material Parameter Coefficients

Seebeck Coefficient, Electrical Resistivity, and Conductivity: These values are temperature-dependent, and are defined with polynomials. The coefficients in the sample devices are a good starting point, but check with the TEC manufacturer for coefficient values for specific devices, as needed.
1. Click the Seebeck Coefficient button.
2. Either use the coefficients from the sample devices or input different coefficient values. Click Apply to save the values.
3. Repeat with Electrical Resistivity, and click Apply.
4. Repeat with Conductivity, and click Apply.
These expressions are second order polynomials that vary with the average temperature, Tav. The coefficient values vary by manufacturer, and the default values supplied in Autodesk® CFD are published in the reference below.

Seebeck Coefficient, a, units of V/K:

a = 0.000210902 + 3.4426e-07(Tav - 23) - 9.904e-10(Tav - 23)²

Electrical Resistivity, r, units of Ohm-m:

r = 1.08497e-05 + 5.35e-08(Tav - 23) + 6.28e-11(Tav - 23)²

Conductivity, k, units of W/m-K:

k = 1.65901 - 0.00332(Tav - 23) + 4.13e-5(Tav - 23)²

To compute custom coefficients for these values:
1. For each quantity, plot values as a function of temperature (in °C).
2. Use a curve-fit tool to compute a second order polynomial.
3. Extract the 0, 1st, and 2nd order coefficients from the equation.
4. Enter the three coefficients in the appropriate field in the Material Editor.
4. Specify the TEC Parameter Limits

These are the manufacturer supplied limiting performance parameters for specific devices. It is very important to use the correct parameter values for the specific device in the analysis model.
1. Click the TEC Parameter Limits button.
2. Specify the manufacturer-supplied TEC parameter limits. These parameters limit the performance of the device within the Autodesk® CFD analysis. If the system is such that a target temperature can only be maintained by surpassing the maximum values, a warning will be given to indicate that the TEC device parameters have been exceeded.
  - QMax is the maximum heat load the device can absorb through the cold side. It is the power that corresponds to a temperature difference across the module of DT = 0, at the maximum current (Imax).
  - IMax is the DC current that results in a maximum temperature difference (DTMax). It is not the highest value of current the module can accept, but rather the current that results in DTMax. (It is the maximum current that can be applied to the device before the resultant Joule-heating surpasses the cooling effect. TEC devices operated above their maximum rated current will add more heat to the system than they will remove through the Peltier effect.)
  - VMax is the maximum voltage for Imax with no heat load.
  - DTMax is the maximum temperature differential that can be maintained across the module at Imax, with no heat load.
3. Click Apply to save the values.
Optionally, click Save.
Click OK. The new material is available when the Materials quick edit dialog is opened.

TEC Modeling Guidelines

Reference: Rowe, D.M., CRC Handbook of Thermoelectrics, CRC Press, Boca Raton, 1995.