Cancel
Showing results for 
Search instead for 
Did you mean: 

Transient Heat Transfer: Thermal Analysis to Predict Product Performance

Siemens Experimenter Siemens Experimenter
Siemens Experimenter

Solid Edge Simulation offers a number of tools that allow you to analyze and predict product performance in the real world, so you can design better products that will be built to last and withstand many varying conditions throughout their operation. In this post today, we are going to look at heat transfer studies, and specifically a new type of thermal analysis available in Solid Edge 2019. 

 

What are heat transfer studies?

Heat transfer studies are thermal studies that analyze heat flow due to differences in temperature. In Solid Edge 2019, there are two types of heat transfer studies available in Solid Edge Simulation: steady state and transient.

 

  • A steady state heat transfer study simulates the thermal conditions of an object when it reaches equilibrium with its surroundings. At this operational stage of the model, heat flow and temperature are constant (in a steady state).

  • A transient heat transfer study simulates the effects of heat energy within and around an object over a period of time, before a steady-state temperature is reached.

You can use heat transfer to evaluate temperature distribution and maximum temperatures at different stages in the operation of your design. For example, use a steady state study to determine the final state and maximum temperature of the model, and use a transient heat study to see the temperature changes during the operation of the model, or at a critical or specific time.

Setting up a transient heat transfer study in Solid Edge Simulation

The examples shown here are for a brake rotor part model. The objective is to identify the maximum temperature of the break rotor over time, and to verify that thermal stresses do not exceed operational maximum temperature for the part.

 

brake_rotor_part.png

IMPORTANT--Before you begin working with your model, verify in the Material Table that material property values for Thermal Conductivity, Density, and Specific Heat are defined for the material used in it.

 

Create the study.

 

1. On the Simulation tab, click New Study. In the Create Study dialog box, from the Study type list, select Transient Heat Transfer. Selecting this study type opens the Transient Heat Options dialog box.

 

1select_study_type.png

 

 

 

 

 

 

 

2. In the Transient Heat Options dialog box, enter the study processing parameters based on the following guidelines, and then click OK.

2define_transient_heat_options.pngDefine Transient Heat Options (HELP)

TIP--Click the Help button to open this procedure directly in Solid Edge Simulation help. Follow the links in help to more detailed information about these options.

TIP--To change the default initial temperature after the study is solved, you must edit the Body Temperature load value in the Simulation pane→Loads group.

 

End Time—This is the total time that you want the analysis to run. You can convert a value from a known number of minutes to seconds by typing min after the value, and then pressing Tab.

Calculation Time Increment—How often do you want the system to calculate thermal results?  

Output Step—At what time increment in the process do you want to begin generating plots?

Default Initial Temperature—This is the starting temperature that will be applied to all of the geometry included in the study. Subsequent temperatures are calculated from this starting point.

  

NOTE--------------------------------------------------------------------------------------------------------------------------------------

Results are generated until the study end time is reached, but the number of results varies with your inputs. Use this formula to determine some reasonable input values:

 

Number of Result Sets= (End Time)/(Calculation Time Increment)/(Output Step)+1, where +1 represents the baseline result plots at Increment 1, 0 seconds.

 

Here are two examples for a study length of 100 seconds:

  • If Calculation Time Increment=5 sec and Output Step=5, results are calculated every 25 seconds, and result sets are produced at these intervals: Number of Result Sets =100/5/5+1=5transient_heat_result_increments.png
  • If Calculation Time Increment=2 sec and Output Step=5, results are calculated every 10 seconds, and result sets are produced at these intervals: Number of Result Sets =100/2/5+1=11.transient_heat_result_11increments.png

     

------------------------------------------------------------------------------------------------------------------------------------------------

 

3. In the Create Study dialog box, in the Results Options section, under Elemental Results, click Heat Flux. Temperature result plots are produced by default. Selecting this check box adds heat flux plots to each set of results.

 

3select_heat_flux_result.png

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

NOTE--Assembly models require connectors. For any type of study, you can add connectors automatically based on the mate relationships in the assembly by selecting the appropriate options in the Connector Options section of the Create Study dialog box, shown above.

 

4. Click OK in the Create Study dialog box to initiate the transient heat study.

 

TIP--To change your study options after the study is created, use the Transient Heat Options… button in the Modify Study dialog box.

modify_transient_heat_options.png

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Apply thermal boundary conditions.

 

Temperature differentials occur when heat is transferred by conduction (through a solid body), by convection (between a body and a liquid or gas), or by radiation. Use the commands in the Thermal Loads group on the ribbon to define the heat transfer mechanisms (the boundary conditions) for your model. These commands act as both loads and constraints in thermal studies. The specific commands you choose depend on the file type (part or assembly), where you want to apply the load (entire bodies or selected entities), and how the model is intended to operate.

 

1. A body temperature load is required as a starting point for a transient heat transfer study. Observe the following:

  • For this brake rotor and for other part models with a tetrahedral mesh, a Body Temperature load was added automatically to the Simulation pane→Loads group when you initiated the study. The temperature assigned to it is the Default Initial Temperature you entered in the Transient Heat Options dialog box.

 

body_temperature_load_simulation_pane.png

 

  • For models with a surface mesh (for example, sheet metal) or a general body mesh (for example, some assemblies), you must select the Body Loads group→Body Temperature command and assign a default initial temperature to the study geometry.

2. Apply a thermal load to define the source of the heat.

  • Use the Heat Flux command  to define heat conducted within a solid or between a solid and a liquid or gas. You can apply it to a face, curve, edge, node, or point. For this brake rotor, we added a 1200 W Heat Flux load to the brake pads on both sides of the rotor where the brake is applied.

    apply_heat_flux_load.png

 

 

  • In an assembly, use the Heat Generation command to apply heat transfer to entire bodies or components.


3. Apply a thermal load to specify how heat is removed. Use a free Convection load to define how heat is transferred from one surface to another surface or to its surroundings due to a temperature differential.

  • We added a Convection load to all of the surfaces of the rotor except the brake pad surfaces. We assigned a natural convection film coefficient value of 22.000 W/m^2-K and an ambient temperature of 20.000 C.

    apply_convection_load.png

 

 

 

4. Mesh and solve the study.

mesh_and_solve.png

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

What do the results mean?

When the study is solved, the results are shown in the Simulation Results environment. Compare the Color Bar color-coding and values to the temperatures shown in the temperature and heat flux plots. You can use this information to determine whether the part meets the maximum temperature requirements set by your company.

 

Review the thermal result plots.

  1. Select the type of plots you want to review on the Home tab→Data Selection
  2. Use the Result Mode list to choose a specific results increment, or click the arrows to cycle through each plot produced at each time interval.
  3. From the Result Type list, choose Temperature or Heat Flux.
  4. From the Result Component list, choose the specific result plot.
  5. To quickly locate a specific plot, use the Simulation pane. Expand the ResultsPlotsIncrement sets to see the list of individual temperature and heat flux plots produced at the specified time intervals. Use the View command on the shortcut menu (or double-click) to open the results plot. If a plot is listed in gray text, you still can display it.

    heat_flux_plot.png

 

 

  

transient_heat_temp_plot.png

 

 

Create a report to review and share the results with others.

  • Use the Home tab->Output Results group->Create Report command to create a report as an HTML web page or as a Word doc or other format. The Thermal Results section of the report conveniently summarizes the maximum and minimum temperatures in each time increment.

    create_report_command.png

report_thermal_results_table.png

 

 

Use the Probe Table to see the analysis data at specific nodes.

For a transient heat transfer study, you can select the Probe command to show the stress data at each time step for nodes selected in the Probe Table. Use the Show Graph button to show the stress data in graphical form. Probe labels matching each of the selected nodes are displayed in the simulation results, color-coded to match the data in the graph.

See the help topic, Graph nodal analysis results, to learn how to do this.

NOTE-- In Solid Edge 2019, you can only generate a graph of node values for transient heat transfer studies.

 

transient_heat_probe_graph1600x880.png

 

Use the transient heat Temperature-Nodal graph to find the steady state temperature.

While the example above shows how the temperature changes over time, it does not indicate the temperature at which a steady operational state is reached. If you close the Simulation Results, you can change the study input values and then reprocess it. Right-click the study name in the Simulation pane and select Modify Study to access the transient heat study options. Adjust the End Time (the length of time the study runs), and then solve the study, until you are able to generate a graph that shows that temperatures have reached a nearly steady state.

 

You can also experiment with changes to the Calculation Time Increment and the Output Step, to maintain a useful temperature distribution of node values along the curve.

 

Here are a few examples. The first shows the starting point for the comparison. It is a transient heat graph of a single node generated using the Transient Heat Options values shown below: 
End Time=1000 sec
Calculation Time Increment=100.00 sec

 

transient_heat_graph1.png

 

The last three examples all use an adjusted End Time=5000 sec. Running the study for this length of time produces a graph that flattens to show the steady state temperature.

 

  • One graph uses Calculation Time Increment=250.
  • The next graph uses Calculation Time Increment=200.
  • The last graph uses Calculation Time Increment=150.

transient_heat_graph3.png

 

transient_heat_graph2.png

 

 transient_heat_graph4.png

 

 

Create a movie showing the results plots in sequence.

  1. Display the increment result plot (temperature or one of the heat flux plots) that you want to create a movie of in the Simulation Results.
  2. Select the Home tab-->Animate group-->Animate command.
    animate_command.png
  3. You can set animation options, and then save it as a movie (.avi file) using the Save As Movie button on the Animate command bar.

 

animate_heat_flux_temp_gradations.png 

Click to play an example of the movie produced by the Animate command. 

(view in My Videos)

 

NOTE--If you want structural analysis (displacement and stress, such as Von Mises and factor of safety) as well as thermal analysis (temperature and applied temperature), then create a thermal coupled study. In a thermal coupled study, you define thermal loads and constraints and structural loads and constraints, in any order. When you solve the study, Solid Edge Simulation first processes the thermal analysis, and then applies the thermal results as a boundary condition input to the linear static analysis.

To define a thermal coupled study, set the Study type=Steady State Heat Transfer + Linear Static in the Create Study dialog box.
thermal_coupled_study.png

 

You can try this yourself using a training model delivered with Solid Edge. Follow the instructions in the practice activity in Solid Edge Simulation Help, titled Activity: Perform a thermal stress analysis.

 

Contributors