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

Transient Thermal Analysis

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/mm 2 is applied until a steady state is reached

Heating follows a 30 second step cycle of 0 to 0.003 W/mm 2 after steady state is reached

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

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.

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/mm 2 7

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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/mm 2 * Area Area PP

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

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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. . . Workshop 6.2 - Transient Setup

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

. . . Workshop 6.2 - Transient Setup

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

0.003 W/mm 2 Heat Flux

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. . . Workshop 6.2 - Transient Setup

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

. . . Workshop 6.2 - Transient Setup

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

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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. . . Workshop 6.2 - Transient Results

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

. . . Workshop 6.2 - Transient Results

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