Loads

The following types of loading are available in the Thermal Analysis workbench:

Creating Surface Heat Fluxes: Applies a heat flux to a surface geometry selection.

Creating Body Heat Fluxes: Applies a heat flux to a volume geometry selection.

Creating Point Heat Fluxes: Applies a heat flux to a point geometry selection.

Creating Film Conditions: Applies a heat flux due to convection to a surface geometry selection.

You apply environmental actions, such as loads, to supports (geometrical features) on your model. The supports that are available include points/vertices, curves/edges, surfaces/faces, or volumes/parts. In addition, point, line, or surface groups are also valid supports. You can either select the support and then set the load specifications or set the load specifications and then select the support. Table 10–2 summarizes the supports to which each type of load can be applied.

Table 10–2 Supports for loads.

Load	Point, Vertex, or Point Group	Curve, Edge, or Line Group	Surface, Face, or Surface Group	Volume or Part
Surface Heat Flux
Body Heat Flux
Point Heat Flux
Film Condition

Creating Surface Heat Fluxes

Surface heat fluxes represent uniform scalar heat fluxes applied to surface geometries.

Surface heat fluxes can be applied only in heat transfer steps.

The magnitude of a surface heat flux can vary with time during a step according to an amplitude definition (see Amplitudes for more information on defining amplitudes).

You can prescribe the time variation of the magnitude of a surface heat flux in a user subroutine, which is sometimes preferable when the time history of the magnitude is complex. You can also apply knowledgeware techniques to control the value of a surface heat flux (for more information, see Applying Knowledgeware).

You can import heat flux data into a surface heat flux definition from a Microsoft Excel spreadsheet (.xls*) or a text file (.txt). The imported heat flux data must satisfy the following criteria:

The data must be arranged in four columns in the following order: X-coordinate, Y-coordinate, Z-coordinate, and heat flux value.
The data must include a header row in which the dimensional data are provided in parentheses. Surface heat flux data can be provided without dimensions. The following sample header row provides one example of proper header row syntax:

X(mm) Y(mm) Z(mm) Heat flux()

The actual heat flux values created from imported data will be the product of the dimensionless heat flux values multiplied by the value you provide for the Magnitude of the initial temperature. For example, if your imported data specify a dimensionless value of 10 at the location (0, 0, 0) and you specify a value of 20W_m2 for the surface heat flux object, the surface heat flux at that location will be 200W/m² for the analysis.

Surface heat fluxes can be applied to surface or face supports or to a surface group.

This task shows you how to create a surface heat flux on geometry.

Click the Surface Heat Flux icon .

The Surface Heat Flux dialog box appears, and a Surface Heat Flux object appears in the specification tree under the Loads objects set for the current step.
You can change the identifier of the load by editing the Name field.
Select the geometry support (a surface). Any selectable geometry is highlighted when you pass the cursor over it. You can select several supports to apply the load to all supports simultaneously. You can also select a surface group.

The Supports field is updated to reflect your selection. A temporary symbol will appear at the supports to indicate zero values until you apply a nonzero load.
Enter a value for the surface heat flux Magnitude.
Right-click on the surface heat flux Magnitude field to add knowledgeware controls (for more information, see Applying Knowledgeware).
To import and incorporate mappings for heat flux data into the surface heat flux definition, perform the following steps:
1. Toggle on Data mapping, then click the ... button.
  
  The Data Mapping dialog box appears.
2. Click Browse, then select the spreadsheet or text file from which you want to import temperature data.
  
  Once you select a file, you can display the imported data in tabular form in the Imported Table dialog box by clicking Show.
3. If desired, toggle on Display Bounding Box to display a three-dimensional box incorporating the minimum and maximum values from the imported table. The bounding box enables you to confirm that the support you select lies completely within the space dictated by the imported data; if a portion of the support is outside this box, an error will be returned during the analysis.
4. Click OK to close the Data Mapping dialog box.
Click More to access additional surface heat flux options.
1. Toggle on Selected amplitude, and select an amplitude from the specification tree to define a nondefault time variation for the surface heat flux.
  
  If you do not specify an amplitude, the solver applies the reference magnitude based on the Default load variation with time option that you selected when you created the step. The solver either applies the reference magnitude linearly over the step (Ramp) or applies it immediately at the beginning of the step and subsequently holds it constant (Instantaneous).
2. Toggle on Apply user subroutine to define a nonuniform variation of the surface heat flux magnitude throughout the step in user subroutine DFLUX. For more information, see Using User Subroutines.
Click OK in the Surface Heat Flux dialog box.

Symbols representing the applied heat flux are displayed on the geometry.

Creating Body Heat Fluxes

Body heat fluxes represent uniform scalar heat fluxes applied to volume geometries.

Body heat fluxes can be applied only in heat transfer steps.

The magnitude of a body heat flux can vary with time during a step according to an amplitude definition (see Amplitudes for more information on defining amplitudes).

You can prescribe the time variation of the magnitude of a body heat flux in a user subroutine, which is sometimes preferable when the time history of the magnitude is complex.

You can import heat flux data into a body heat flux definition from a Microsoft Excel spreadsheet (.xls*) or a text file (.txt). The imported heat flux data must satisfy the following criteria:

The data must be arranged in four columns in the following order: X-coordinate, Y-coordinate, Z-coordinate, and heat flux value.
The data must include a header row in which the dimensional data are provided in parentheses. Body heat flux data can be provided without dimensions. The following sample header row provides one example of proper header row syntax:

X(mm) Y(mm) Z(mm) Heat flux()

The actual heat flux values created from imported data will be the product of the dimensionless heat flux values multiplied by the value you provide for the Magnitude of the initial temperature. For example, if your imported data specify a dimensionless value of 10 at the location (0, 0, 0) and you specify a value of 20W_m2 for the body heat flux object, the body heat flux at that location will be 200W/m² for the analysis.

Body heat fluxes can be applied to volume or part supports or to a body group.

This task shows you how to create a body heat flux on geometry.

Click the Body Heat Flux icon .

The Body Heat Flux dialog box appears, and a Body Heat Flux object appears in the specification tree under the Loads objects set for the current step.
You can change the identifier of the load by editing the Name field.
Select the geometry support (a volume or part). Any selectable geometry is highlighted when you pass the cursor over it. You can select several supports to apply the load to all supports simultaneously. You can also select a body group.

The Supports field is updated to reflect your selection.
Enter a value for the body heat flux magnitude.
To import and incorporate mappings for heat flux into the body heat flux definition, perform the following steps:
1. Toggle on Data mapping, then click the ... button.
  
  The Data Mapping dialog box appears.
2. Click Browse, then select the spreadsheet or text file from which you want to import temperature data.
  
  Once you select a file, you can display the imported data in tabular form in the Imported Table dialog box by clicking Show.
3. If desired, toggle on Display Bounding Box to display a three-dimensional box incorporating the minimum and maximum values from the imported table. The bounding box enables you to confirm that the support you select lies completely within the space dictated by the imported data; if a portion of the support is outside this box, an error will be returned during the analysis.
4. Click OK to close the Data Mapping dialog box.
Click More to access additional body heat flux options.
1. Toggle on Selected amplitude, and select an amplitude from the specification tree to define a nondefault time variation for the body heat flux.
  
  If you do not specify an amplitude, the solver applies the reference magnitude based on the Default load variation with time option that you selected when you created the step. The solver either applies the reference magnitude linearly over the step (Ramp) or applies it immediately at the beginning of the step and subsequently holds it constant (Instantaneous).
2. Toggle on Apply user subroutine to define a nonuniform variation of the body heat flux magnitude throughout the step in user subroutine DFLUX. For more information, see Using User Subroutines.
Click OK in the Body Heat Flux dialog box.

Symbols representing the applied heat flux are displayed on the geometry.

Creating Point Heat Fluxes

Point heat fluxes represent uniform scalar heat fluxes applied to selected degrees of freedom.

Point heat fluxes can be applied only in heat transfer steps.

The magnitude of a point heat flux can vary with time during a step according to an amplitude definition (see Amplitudes for more information on defining amplitudes). You can also apply knowledgeware techniques to control the value of a point heat flux (for more information, see Applying Knowledgeware).

Point heat fluxes can be applied to point or vertex supports or to a point group.

This task shows you how to create a point heat flux on geometry.

Click the Point Heat Flux icon .

The Point Heat Flux dialog box appears, and a Point Heat Flux object appears in the specification tree under the Loads objects set for the current step.
You can change the identifier of the load by editing the Name field.
Select the geometry support (a point). Any selectable geometry is highlighted when you pass the cursor over it. You can select several supports to apply the load to all supports simultaneously. You can also select a point group.

The Supports field is updated to reflect your selection.
Enter a value for the point heat flux Magnitude.
Right-click on the point heat flux Magnitude field to add knowledgeware controls (for more information, see Applying Knowledgeware).
Click More to access additional point heat flux options.
1. Toggle on Selected amplitude, and select an amplitude from the specification tree to define a nondefault time variation for the point heat flux.
  
  If you do not specify an amplitude, the solver applies the reference magnitude based on the Default load variation with time option that you selected when you created the step. The solver either applies the reference magnitude linearly over the step (Ramp) or applies it immediately at the beginning of the step and subsequently holds it constant (Instantaneous).
Click OK in the Point Heat Flux dialog box.

Symbols representing the applied heat flux are displayed on the geometry.

Creating Film Conditions

Film conditions represent heat flux on a surface due to convection. The governing equation for this heat flux is

where

is the heat flux across the surface,

is the film coefficient,

is the temperature at this point on the surface, and

is a reference sink temperature value.

Film conditions can be applied only in heat transfer steps.

By default, the sink temperature varies linearly with time throughout the step from its value at the end of the previous step (ramp function), while the film coefficient is applied immediately and remains constant throughout the step. Nondefault time variations can be defined for the sink temperature and/or the film coefficient by referring to amplitude definitions (see Amplitudes for more information on defining amplitudes).

You can prescribe the time variation of the magnitude of the film coefficient in a user subroutine, which is sometimes preferable when the time history of the magnitude is complex.

You can import reference sink temperature and film coefficent data into a film condition definition from a Microsoft Excel spreadsheet (.xls*) or a text file (.txt). The imported data must satisfy the following criteria:

The data must be arranged in five columns in the following order: X–coordinate, Y–coordinate, Z–coordinate, reference sink temperature, and film coefficient.
The data must include a header row in which the dimensional data are provided in parentheses.Thermal Analysis disregards dimensional data, if provided, for reference sink temperature data and film coefficients. The following sample header row provides one example of proper header row syntax:

X(mm) Y(mm) Z(mm) Sink Temperature() Film Coefficient()

If you toggle on Use temperature-dependent data and specify reference sink temperature and film coefficient values in the Film Condition dialog box, all imported film coefficient data are disregarded and the data specified in the dialog box are used instead. Imported sink temperature data are still included in the analysis.

Film conditions can be applied to surface or face supports or to a surface group.

This task shows you how to create a film condition on geometry.

Click the Film Condition icon .

The Film Condition dialog box appears, and a Film Condition object appears in the specification tree under the Loads objects set for the current step.
You can change the identifier of the load by editing the Name field.
Select the geometry support (a surface). Any selectable geometry is highlighted when you pass the cursor over it. You can select several supports to apply the load to all supports simultaneously. You can also select a surface group.

The Supports field is updated to reflect your selection. A temporary symbol will appear at the supports to indicate zero values until you apply a nonzero load.
Specify the film coefficient, h. By default, the film coefficient is assumed to be a function of surface temperature.
1. Enter the film coefficient versus temperature values in the data table.
2. To add or delete table rows, click Add or Delete below the data table.
3. To read the film coefficient data from a text file, click the Folder icon , and select an ASCII text file that contains columns of numerical data separated by commas, tabs, or spaces.
4. Toggle off Use temperature-dependent data if the film coefficient does not vary with temperature, and enter only a single film coefficient value in the data table.
Enter a value for the Reference sink temperature, .
To import and incorporate mappings for sink temperature and film coefficients into the film condition definition, perform the following steps:
1. Toggle on Data mapping, then click the ... button.
  
  The Data Mapping dialog box appears.
2. Click Browse, then select the spreadsheet or text file from which you want to import temperature data.
  
  Once you select a file, you can display the imported data in tabular form in the Imported Table dialog box by clicking Show.
3. If desired, toggle on Display Bounding Box to display a three-dimensional box incorporating the minimum and maximum values from the imported table. The bounding box enables you to confirm that the support you select lies completely within the space dictated by the imported data; if a portion of the support is outside this box, an error will be returned during the analysis.
4. Click OK to close the Data Mapping dialog box.
Click More to access additional film condition options.
1. Toggle on Selected amplitude, and select an amplitude from the specification tree to define a nondefault variation for the Sink Temperature vs Time.
  
  If you do not specify an amplitude, the solver applies the reference sink temperature based on the Default load variation with time option that you selected when you created the step. The solver either applies the reference magnitude linearly over the step (Ramp) or applies it immediately at the beginning of the step and subsequently holds it constant (Instantaneous).
2. Toggle on Selected amplitude, and select an amplitude from the specification tree to define a nondefault variation for the Film Coefficient vs Time.
  
  If you do not specify an amplitude, the solver applies the reference film coefficient immediately at the beginning of the step and subsequently holds it constant (Instantaneous).
3. Toggle on Apply user subroutine to define a nonuniform film coefficient as a function of position, time, temperature, etc. in user subroutine FILM. For more information, see Using User Subroutines.
Right-click on the Reference sink temperature field to add knowledgeware controls (for more information, see Applying Knowledgeware).
Click OK in the Film Condition dialog box.

Symbols representing the applied film condition are displayed on the geometry.