Transient Thermal Analysis

Winter Semester2009-2010

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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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AssumptionsAssumptions: The heating element contacts and transfers

heat to the base using the pattern shown here

Upon initial startup a heat flow of 1000 W is applied until a steady state is reached

Heating follows a 30 second step cycle of 0 to 1000 W 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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Start Page

From the launcher start Simulation. Choose “Geometry > From File . . . “

and browse to the file “Iron.x_t”.

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Preprocessing Change the part material to “Stainless

Steel”:– Highlight “Part1”– In the Detail window “Material” field

“Import . . .”– Choose the “Stainless Steel” material

Set the working units to (mm, kg, N, C, s, mV, mA)

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Preprocessing Start new thermal analysis by selecting

“Transient Thermal” under the “New Analysis” menu.

The initial conditions include thermal load, which is constant temp, will be applied for 1sec.– Highlight the initial condition branch.– Set the ‘Initial temp’, in the ‘Details

window’, to ‘Uniform Temperature’.– Highlight the ‘Analysis settings’ branch

and make sure that the ‘Step end time’ is 1 sec.

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Transient Thermal• Select surface representing the heating

element on the face of the iron

• “RMB > Insert > Heat Flow”.

• Set “Magnitude” field to 1000 W.

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Environment• Select the bottom surface (opposite the

heat flux side) and 6 side surfaces of the iron (7 faces)

• “RMB > Insert > Convection”• Change to “Temperature Dependent” by

choosing “Tabular (temperature)” in the details window.

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Environment• Choose “Import” in the correlation field• Select “Stagnant Air – Vertical Planes1”• Set ambient temperature to 20 deg. C

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Environment• Select the 2 surfaces surrounding the

heated surface.• “RMB > Insert > Convection” • Change to “Temperature Dependent”• Choose “Import” in the correlation field• Select “Stagnant Air – Vertical Planes”• Set ambient temperature to 40 deg. C

Please see previews slides for the stages above

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Solution Add temperature and total heat flux results.• Highlight the Solution branch.• “RMB > Insert > Thermal > Temperature”, repeat for total heat

flux

• Solve

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Results A review of the results shows that after 1 sec of heating, the

maximum temperature is approximately 36.8° C

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Transient Solution• We will apply a periodic load during 180 sec.• Highlight the “Analysis setting” branch, begin the transient

setup by specifying an end time of 180 seconds

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Transient Setup• Highlight “Heat Flow” in the Thermal

Transient branch

• In the heat flow details windows, select the Magnitude and choose “Add to Engineering Data”

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Transient Setup Change to Engineering Data tab 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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Transient Setup• Enter time and load information as described in the problem

statement: 30 second increments 0-1000 W Heat Flow

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Transient Setup• Highlight the “Analysis

Settings” branch• In the Details window omit all

parameters except the Heat Flow and temperature.

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

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Transient Results• Solve

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

• Note: due to the long exposure time to heat flow, the max temp achieved was 163.18°C (comparing to 36.8°C during 1 sec)

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Transient Results – Postprocessing

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

35.RMB > Retrieve This Results

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Transient Results Notice: when a new time point is

selected in the time line, the result details window 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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Transient Results Using the Probe Tool allows individual parts of the model to be evaluated over time Add probe tool for heat flow the center area:

Highlight the Solution branch: RMB Insert Probe Heat flux Add probe tool for temperature for the same area

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Transient Results In the details window, select the results to display the total

result

RMB on the solution branch Evaluate all results

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Results for the heat flux probe

Results for the Temperature probe