transient thermal analysis workshop 6.2. workshop supplement transient thermal analysis august 26,...

Transient Thermal Analysis

Workshop 6.2

August 26, 2005Inventory

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Workshop 6.2 - Goals

• In this workshop, we will analyze the electrically heated base typical of consumer steam irons like the one shown below.


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Workshop 6.2 - Assumptions

Assumptions:

• The heating element contacts and transfers heat to the base using the pattern shown here

• Upon initial startup a heat flux of 0.001 W/mm2 is applied until a steady state is reached

• Heating follows a 30 second step cycle of 0 to 0.003 W/mm2 after steady state is reached

• The analysis will begin with the steady state solution and proceed through the cyclic loading described above


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Workshop 6.2 - Start Page

• From the launcher start Simulation.

• Choose “Geometry > From File . . . “ and browse to the file “Iron.x_t”.

• When DS starts, close the Template menu by clicking the ‘X’ in the corner of the window.


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Workshop 6.2 - Preprocessing

• Change the part material to “Polyethylene”:

1. Highlight “Part1”

2. In the Detail window “Material” field “Import . . .”

3. “Choose” material “Stainless Steel”

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4. Set the working units to (mm, kg, N, C, s, mV, mA) “Tools > Units” menu choose

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Workshop 6.2 - Environment

5. Select surface representing the heating element on the face of the iron

6. “RMB > Insert > Heat Flux”.

7. Set “Magnitude” field to 0.001 W/mm27

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. . . Workshop 6.2 - Environment

8. Select the bottom surface (opposite the heat flux side) and 6 side surfaces of the iron (7 faces)

9. “RMB > Insert > Convection”

10. Change to “Temperature Dependent”

11. Choose “Import” in the correlation field

12. Select “Stagnant Air – Vertical Planes1”

13. Set ambient temperature to 20 deg. C

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. . . Workshop 6.2 - Environment

14. Select the 2 surfaces surrounding the heated surface

15. “RMB > Insert > Convection”

16. Change to “Temperature Dependent”

17. Choose “Import” in the correlation field

18. Select “Stagnant Air – Vertical Planes”

19. Set ambient temperature to 40 deg. C

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Workshop 6.2 - Solution

• Add temperature and total heat flux results.

20. Highlight the Solution branch.

21. “RMB > Insert > Thermal > Temperature”, repeat for total heat flux

22. Solve

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Workshop 6.2 - Results

• A review of the results shows the maximum steady state temperature is approximately 51.7 degrees C

• The worksheet view of the environment shows that an energy balance has been achieved– Convection1 + Convection2 ≈ 5.2 W

– Applied Load = 0.001W/mm2 * Area• Area ≈ 5276 mm


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Workshop 6.2 – Transient Solution

23. Highlight the “Temperature” result, RMB > “Generate Transient Environment with Initial Condition”

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• The result is, the steady state environment is duplicated and the new branch automatically setup as a thermal transient run– Notice the new branch contains an

“initial condition” branch and a “transient settings” branch


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Workshop 6.2 – Transient Setup

24. Begin the transient setup by specifying an end time of 180 seconds for the analysis in the toolbar

25. Inspection of the initial condition details shows no action is required. The steady state (non-uniform) temperature result from the “Environment” branch is mapped to the transient branch

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. . . Workshop 6.2 - Transient Setup

26. Highlight “Heat Flux” in the Thermal Transient branch

27. In the heat flux detail change “Define As” to “Load History”

28. In the “History Data” field choose “New Load History . . . “

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• The Engineering Data application will open and a new “Heat Flux vs. Time” chart/graph will be created

• Enter the time and load data as shown on the next page


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29. Enter time and load information as described in the problem statement– 30 second increments

– 0.003 W/mm2 Heat Flux

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30. Highlight the “Transient Settings” branch

31. Toggle off all items but “Heat Flux” in the “Visible” and “Active” columns of the Timeline Legend Control

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Notice the automatic time steps are based on the end time:

Initial = ET/100, Min = ET/1000, Max = ET/10

Leave time steps as default


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• Toggling off all but the heat flux allows easier inspection of the timeline chart in this case

• Since the heat flux is the only load defined as a “non-constant” it will have the only influence on the placement of the automatic step resets

Reset points

As expected, each reset point coincides

with an inflection point on the load

history


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Workshop 6.2 - Transient Results

32. Solve the thermal transient branch

• When the solution is complete, results can be reviewed just as with steady state solutions

33. Highlight the quantity of interest to plot

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. . . Workshop 6.2 - Transient Results

34. To review results from specific time points, LMB in the timeline chart to locate the time of interest

35. RMB > Retrieve Results

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• Notice, when a new time point is selected in the time line, the result detail is displayed in red until the results matching the time selection are retrieved

• Plotting the “Global Maximum” temperature from the Solution Information branch shows the model has not reached a cyclic equilibrium


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• Using the Probe Tool allows individual parts of the model to be evaluated over time

• Multiple Probes can be plotted on the same graph

Single Probe Multiple Probes

transient thermal analysis workshop 6.2. workshop supplement transient thermal analysis august 26,...

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