Film - Convection Library

The Surface Film/Convection Coefficient Library is used to store convection coefficient values that are used frequently. The values are entered through the Film/Convection Coefficient Calculator dialog.

Note: The Autodesk Simulation Default Library cannot be modified. New values can be added to the user-created libraries only.

How to Access Convection Libraries

The convection library is accessible when applying a convection load to the model. Select a surface, right-click, and choose Add Surface Convection Load. To perform general maintenance on the convection library (add new libraries, add new coefficients, edit existing entries, etc.), click the Read from Library button on the Surface Convection Object dialog.

To apply a convection value from the library to the model, simply select the name in the Coefficient list on the right and click OK. The value will be copied to the Surface Convection Object dialog.

The convection library always shows the values using the units set in the model. The values stored in the library are converted from the units in which they were entered to the units shown in the current model.

How to Create Libraries

Access the convection library as described above. Then,

  • If the library file does not exist, click the Create button. Then specify the descriptive name for the new library. Then, the filename and location for the library file will be specified with a standard Windows Save As dialog.
  • If the library file already exists but is not linked to in your software, click the Import button. For example, a co-worker may have created a convection library on a network drive or provided their file to you. The Import button will display a standard Windows Open dialog from which you can choose the file.

How to Add Convection Values

New convection values can be added to a library either from the library dialog or from the convection calculator dialog. The advantage of using the convection library is that all the existing entries are shown.

To add a value through the convection library

  1. Access the convection library as described above.
  2. Choose the library (on the left side of the dialog) to which the new value is being added. Create a new library first if necessary.
  3. Click the Add button and enter the name for the new value on the New Coefficient dialog.
  4. Once the name is entered, use the Film/Convection Coefficient Calculator dialog to enter the new value. When the OK button on the calculator is clicked, the user-defined value and all supporting input will be stored in the convection library.
  5. Steps 2 through 4 can be repeated to add additional values to the library.

To add a value through the convection calculator,

  1. Click the Calculate button on the Surface Convection Object dialog. This will access the convection calculator.
  2. After entering the relevant values for the arrangement and fluid properties, click the Save to Library button. The Save Film/Convection Coefficient dialog will be displayed with a list of existing user-defined libraries.
  3. Select an existing library. To create a new library, click the entry New in the list of libraries and type the library's description.
  4. Type the Name for the new convection value.
  5. Click the OK button. This will save the user-defined convection value and all supporting input to the selected library and return control to the convection calculator. If the entered name already exists in the library, you have the option to overwrite the existing value. (If the value is being saved to a new library, a standard Windows Save As dialog displays so you can select the location and filename for the library file.)
  6. Steps 2 through 5 can be repeated to add additional values to the library.
Tip: Although the convection calculator is often used to calculate the convection coefficient based on the fluid properties and arrangement, the calculator is also used to store a common convection coefficient to a user-created library. For example, perhaps your company has a standard value of 12.5 J/(s*m 2 *°C) for convection inside some device. This can be added to a library by creating a model (in units of J, s, m, °C) and adding a new convection value as described above. Instead of entering fluid properties into the calculator, simply type the value in the User-defined value for film/convection coefficient.

How to Modify Convection Values

The name of the coefficient can be modified. Access the convection library as described above. Then select the name to be changed, pause, and click the name again. A cursor will appear in the name field. Make to the name and press Enter to finish the edit.

The coefficient value is modified separately from the name. Access the convection library as described above. Then select the name to be changed and click the Edit button. This will display the Film/Convection Coefficient Calculator dialog with all the entries associated with the convection value. Make changes and click OK to update the convection value.

How to Copy Existing Values To New Entries

Although there is no direct method to copy an existing library name to a new name, it is easy to use an existing value from the library as a starting point for a new entry. Simply use the convection calculator method described above to add a new convection value. When the Film/Convection Coefficient Calculator dialog appears, use the Read from Library button to load the input from an existing entry. Then make the desired changes. When the procedure is finished, the changes to the copy will be saved to the new name.

Tip:
  • Due to the number of options in the convection calculator, it is not practical to provide convection values for every combination. However, this may not be necessary. One major benefit of the convection library is saving the fluid properties. Thus, other arrangements can be calculated quickly by reading an existing library value and changing it for a particular arrangement. (Of course, often used arrangements can be saved into a new library for more immediate access.)
  • For example, the Autodesk Simulation Default Library contains entries for fluids at a variety of temperatures. Choose the entry with the fluid temperature closest to the required temperature and make adjustments for the actual arrangement (fluid velocity, dimensions, and so on). The names in the Autodesk Simulation Default Library are organized as follows:
  • fluid, temperature, type, specifics
  • where
    • fluid is the type of fluid.
    • temperature is the temperature corresponding to the fluid properties.
    • type indicates the type of convection: forced external, forced internal, or buoyancy. For buoyancy, the temperature difference between the wall and fluid temperature is given in the name as [dT] but does not indicate whether the wall is hotter or colder than the ambient.
    • specifics indicate the more important parameters relating to the type, such as velocity of the fluid or the orientation of the structure. Other parameters that affect the calculation are not encoded in the name, so these should be reviewed before using the default values for a specific analysis.

Parent topic: Film - Convection Coefficient Calculator