When performing a thermal analysis, consider the dimensionality of the problem as well as the loads required. Use the following information to select elements for modeling various regions as well as elements to apply loads:
A complex thermal model often has a combination of all or most of the element types described.
For more information, see the Thermal Analysis Guide.
Typically, the solid region should be meshed with 2-D or 3-D continuum elements. 1-D elements serve to couple these regions. The 0-D element can be used to represent a lumped mass (that is, a reduced-order model of a continuum region).
Use the following table to select thermal elements for the structural region:
| Continuum | Application | Elements |
|---|---|---|
| 3-D | Modeling homogeneous materials and layered solids / composites | SOLID278 -- Lower-order element that can degenerate |
| SOLID279 -- Higher-order element that can degenerate | ||
| Modeling homogeneous materials | SOLID70 -- Lower-order thermal solid that can degenerate | |
| SOLID87 -- Higher-order tetrahedral-only thermal solid | ||
| SOLID90 -- Higher-order, accurate thermal solid that can degenerate | ||
| 2.5-D | Analyzing the in-plane temperature distribution of thin structures such as plates or shells. [1] | SHELL131 -- 3-D lower-order shell with in-plane and through-thickness thermal conduction capability |
| SHELL132 -- 3-D higher-order shell with in-plane and through-thickness thermal conduction | ||
| 2-D | Modeling irregular meshes | PLANE35 -- Triangular thermal solid (compatible with PLANE77) |
| Modeling a plane or an axisymmetric ring | PLANE55 -- Thermal solid with 2-D thermal conduction | |
| Modeling curved boundaries | PLANE77 -- Higher-order thermal solid | |
| 1-D | Conduction link between regions | LINK33 -- Uniaxial 3-D conduction bar [2] |
| Convection link between regions | LINK34 -- Uniaxial convection link [2] | |
| Radiation link between regions | LINK31 -- Uniaxial radiation link [2] | |
| 0-D | Representing a body having thermal capacitance but with no significant temperature gradients | MASS71 -- Thermal mass point element |
If the model containing the conducting shell element is to be analyzed structurally, use an equivalent structural shell element (such as SHELL281) instead.
In most cases, contact elements can be used in place of this element.
For related information, see Selecting Elements for Your Analysis.
For the 1-D continuum, use FLUID116, a reduced-order coupled thermal-fluid pipe, to represent fluid temperature for flow-through pipes/internal channels. The element can be connected to nodes in the structural region.
Two methods are available for applying loads to thermal elements:
In a thermal model, the surface loads can consist of convection, heat flux, or radiation. Although you can apply the loads directly on the continuum elements, it is more convenient to apply them via surface-effect elements, which are overlaid onto other thermal elements.
Use these surface-effect elements to apply convection, heat flux, and radiation (to a point) on solid regions:
Use these surface-radiosity elements to apply grey body radiation (where view factors are unknown):
Besides surface loads, it is also possible to load thermal models via contact elements.
When two or more structural regions are in close vicinity or contact, it is sometimes necessary to account for convection, conduction, or radiation between the regions. Frictional forces between the contacting surfaces can also be a source of heat generation.
Use these contact elements between solid regions:
2-D Contact Elements
3-D Contact Elements
A special 2-D/3-D node-to-surface contact element, CONTA175, is also available. You can use it with either TARGE169 or TARGE170.
Use the COMBIN37 control element to enable or disable heat flow between two points when the temperature (or other control parameters) reach a specified threshold value.
In addition to the thermal and related loading elements described here, also consider coupled-physics elements, which can couple thermal and other physics.
You can also create a custom element via USER300 to model special physics, or combine a group of linear thermal elements into a MATRIX50 superelement for greater solution efficiency.