This tutorial was created using ANSYS 7.0 to solve a simple transient conduction problem. Special thanks to Jesse Arnold for the analytical solution shown at the end of the tutorial.

The example is constrained as shown in the following figure. Thermal conductivity (k) of the material is 5 W/m*K and the block is assumed to be infinitely long. Also, the density of the material is 920 kg/m^3 and the specific heat capacity (c) is 2.040 kJ/kg*K.

It is beneficial if the Thermal-Conduction tutorial is completed first to compare with this solution.

  1. Give example a Title Utility Menu > File > Change Title...
    /Title,Transient Thermal Conduction

  2. Open preprocessor menu ANSYS Main Menu > Preprocessor

  3. Create geometry Preprocessor > Modeling > Create > Areas > Rectangle > By 2 Corners
    X=0, Y=0, Width=1, Height=1

  4. Define the Type of Element
  5. Preprocessor > Element Type > Add/Edit/Delete... > click 'Add' > Select Thermal Mass Solid, Quad 4Node 55

    For this example, we will use PLANE55 (Thermal Solid, Quad 4node 55). This element has 4 nodes and a single DOF (temperature) at each node. PLANE55 can only be used for 2 dimensional steady-state or transient thermal analysis.

  6. Element Material Properties
  7. Preprocessor > Material Props > Material Models > Thermal > Conductivity > Isotropic > KXX = 5 (Thermal conductivity)
    Preprocessor > Material Props > Material Models > Thermal > Specific Heat > C = 2.04
    Preprocessor > Material Props > Material Models > Thermal > Density > DENS = 920

  8. Mesh Size
  9. Preprocessor > Meshing > Size Cntrls > ManualSize > Areas > All Areas > 0.05

  10. Mesh
  11. Preprocessor > Meshing > Mesh > Areas > Free > Pick All

    At this point, the model should look like the following:

  1. Define Analysis Type
  2. Solution > Analysis Type > New Analysis > Transient

    The window shown below will pop up. We will use the defaults, so click OK.

  3. Set Solution Controls
  4. Solution > Analysis Type > Sol'n Controls

    The following window will pop up.

    A) Set Time at end of loadstep to 300 and Automatic time stepping to ON.
    B) Set Number of substeps to 20, Max no. of substeps to 100, Min no. of substeps to 20.
    C) Set the Frequency to Write every substep.

    Click on the NonLinear tab at the top and fill it in as shown

    D) Set Line search to ON .
    E) Set the Maximum number of iterations to 100.

    For a complete description of what these options do, refer to the help file. Basically, the time at the end of the load step is how long the transient analysis will run and the number of substeps defines how the load is broken up. By writing the data at every step, you can create animations over time and the other options help the problem converge quickly.

  5. Apply Constraints
  6. For thermal problems, constraints can be in the form of Temperature, Heat Flow, Convection, Heat Flux, Heat Generation, or Radiation. In this example, 2 sides of the block have fixed temperatures and the other two are insulated.

  7. Apply Initial Conditions
  8. Solution > Define Loads > Apply > Initial Condit'n > Define > Pick All

    Fill in the IC window as follows to set the initial temperature of the material to 100 K:

  9. Solve the System
  10. Solution > Solve > Current LS

  1. Results Using ANSYS
  2. Plot Temperature

    General Postproc > Plot Results > Contour Plot > Nodal Solu ... > DOF solution, Temperature TEMP

    Animate Results Over Time

    You can see how the temperature rises over the area over time. The heat flows from the higher temperature to the lower temperature constraints as expected. Also, you can see how it reaches equilibrium when the time reaches approximately 200 seconds. Shown below are analytical and ANSYS generated temperature vs time curves for the center of the block. As can be seen, the curves are practically identical, thus the validity of the ANSYS simulation has been proven.

    Analytical Solution

    ANSYS Generated Solution

  1. Creating the Temperature vs. Time Graph

  2. Graph Results over Time

The above example was solved using a mixture of the Graphical User Interface (or GUI) and the command language interface of ANSYS. This problem has also been solved using the ANSYS command language interface that you may want to browse. Open the .HTML version, copy and paste the code into Notepad or a similar text editor and save it to your computer. Now go to 'File > Read input from...' and select the file. A .PDF version is also available for printing.