17.6.2.20. Heat Flow

Heat Flow is available for 3D simulations and 2D simulations for Plane Stress and Axisymmetric behaviors only. For the required geometry settings for Plane Stress and Axisymmetric behaviors, see the 2D Analyses section of the Help

Heat flow simulates the transmission of heat across flat or curved surfaces or edges or across a vertex or vertices and as a result adds energy to a body over time.

Tip:  Because the application applies this load evenly across the scoped geometry, geometric averaging can cause the applied load value to change slightly from your entry if you have a low-quality mesh. This is especially true for curved surfaces or any time the mesh deviates from the idealized geometry. To improve accuracy, refine the mesh.

Perfectly Insulated

For a selected face or faces, Heat Flow allows you to specify a Perfectly Insulated load wherein a "no load" insulated condition is applied to the Face: that is, zero heat flow. An insulated face is a no load condition meant to override any thermal loads scoped to a body. The heat flow rate is 0 across this face. This load is useful in a case where most of a model is exposed to a given condition (such a free air convection) and only a couple of faces do not share this condition (such as the base of a cup that is grounded). This load overrides thermal loads scoped to a body only. For a discussion on thermal load precedence, see Resolving Thermal Boundary Condition Conflicts.

Selecting multiple faces insulates all of the faces.

This page includes the following sections:

Analysis Types

Heat Flow is available for the following analysis types:

Dimensional Types

The supported dimensional types for the Heat Flow boundary condition include:

  • 3D Simulation

  • 2D Simulation

Geometry Types

The supported geometry types for the Heat Flow boundary condition include:

  • Solid

  • Surface/Shell

  • Wire Body/Line Body/Beam

Topology Selection Options

The supported topology selection options for Heat Flow include:

  • Face: Supported for 3D only. If you select multiple faces when defining the heat flow rate, the magnitude is apportioned across all selected faces.

  • Edge

    • If you select multiple edges when defining the heat flow rate, the magnitude is apportioned across all selected edges.

    • During 2D analyses, the application does not enable you to apply Heat Flow to edges that share topology.

  • Vertex. If you select multiple vertices when defining the heat flow rate, the magnitude is apportioned among all selected vertices.

  • Nodes.

  • Element Face.

Magnitude Options

The supported Magnitude options for Heat Flow include the following:

  • Constant

  • Tabular (Time Varying): Supported for face selections in 3D and edge selections in 2D.

  • Function (Time Varying): Supported for face selections in 3D and edge selections in 2D.

Applying a Heat Flow Boundary Condition

To apply a Heat Flow:

  1. On the Environment Context tab, click Heat>Heat Flow. Alternatively, right-click the Environment tree object or in the Geometry window and select Insert>Heat Flow.

  2. Define the Scoping Method as either Geometry Selection or Named Selection and then specify the geometry.

  3. Enter a Magnitude for the Heat Flow.

Details Pane Properties

The selections available in the Details pane are described below.

CategoryProperty/Options/Description
Scope

Scoping Method: This property specifies how you perform geometric entity selection. Options include Geometry Selection (default) and Named Selection.

Geometry: Visible when the Scoping Method is set to Geometry Selection. Displays the type of geometry (Body, Face, etc.) and the number of geometric entities (for example: 1 Body, 2 Edges) to which the boundary has been applied using the selection tools.

Named Selection: Visible when the Scoping Method is set to Named Selection. This field provides a drop-down list of available user-defined Named Selections.

Shell Face: This property is supported for 3D shell bodies only and requires that you activate beta options as well as a beta feature selection for thermal variation. This property enables you to apply the Heat Flow load to the temperature degree of freedom associated with the selected face. Assuming you have specified a Heat Flow load, to display the Shell Face property:

  1. Activate beta options and beta feature selection[a].

  2. Select the shell body under the Geometry object and set the Thermal Variation (Beta) property to an option other than No Variation Along Thickness.

  3. Select the Heat Flow object and define the Shell Face property. Options include Top (default) or Bottom.

Definition

Type: Read-only field that displays boundary condition type - Heat Flow.

Define As: Heat Flow (default) or Perfectly Insulated. Perfectly Insulated indicates zero heat flow.

Magnitude: Loading value.

Suppressed: Include (No - default) or exclude (Yes) the boundary condition.

[a] Activate beta options and beta feature selection:

  1. On the Workbench Project page, select the Tools drop-down menu and then Options.

  2. In the dialog, select the Appearance group and then the Beta Options check box.

  3. Click OK.

  4. Again, select the Tools drop-down menu and then Options.

  5. In the dialog, select the Mechanical group.

  6. Under the heading "MAPDL Solver," select the Allow thermal variation along shell thickness check box.

  7. Click OK.

  8. The application prompts you to restart. Do so, and then open your shell model in Mechanical for a supported analysis type.

Mechanical APDL References and Notes

Convection loading is applied using the element types SURF152 (3D thermal analyses) and SURF151 (2D thermal analyses).

  • In a 3D analyses, Heat Flow on face selections are applied using the SF,,HFLUX command on SURF152 elements. Heat Flow is represented as a table in the input file. Heat Flow applied to a selected edge or vertex use the F command.

  • In a 2D analyses, Heat Flow on edge selections are applied using the SF,,HFLUX command on SURF151 elements. Heat Flow is represented as a table in the input file. Heat Flow on vertex selections are applied using the F command.

API Reference

For specific scripting information, see the Heat Flow section of the ACT API Reference Guide.