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Thermal Solver
Contains thermal solver related guides, such as the TMG reference manual, thermal API guide, and error message list.
Thermal solver theory
Describes the theory and methods of the thermal solver.
Radiation exchange methods
Thermal radiation is a heat transfer due to electromagnetic radiation emitted by the surface of bodies due to their temperature.
View factor calculation without ray-tracing
Inaccuracies due to non-uniform illumination
Radiation calculations with view factors assume uniform illumination over an element, and potentially significant errors may be introduced when this assumption is not fulfilled.

Thermal Solver
Contains thermal solver related guides, such as the TMG reference manual, thermal API guide, and error message list.
- Thermal solver guides
  Maya HTT's thermal solver is included in Simcenter 3D and in Simcenter Femap. This page contains links to thermal solver guides, which help you understand how the thermal solver works.
- Thermal solver theory
  Describes the theory and methods of the thermal solver.
  - Introduction
    This guide provides the theory and methods used by the thermal solver, including methods to calculate conduction, convection, and radiation, as well as modeling specific topics using the thermal solver.
  - Conduction methods
    To model heat conduction, the thermal solver can use two finite volume methods, center of element method or element's center of gravity method, or the finite element method.
  - Convective heat transfer methods
    The thermal solver computes convection conductances for various geometrical configurations using correlations that depend on specified characteristic lengths, convective surfaces, and type of convection.
  - Radiation exchange methods
    Thermal radiation is a heat transfer due to electromagnetic radiation emitted by the surface of bodies due to their temperature.
    - Basic view factor concepts
    - View factor calculation without ray-tracing
      - View factor calculation algorithm
        The following outlines the steps by which view factors are calculated without ray-tracing using deterministic method without explicit sky modeling.
      - View factor accuracy considerations
        The accuracy of the Nusselt sphere technique is compared with the contour integral technique and the double summation technique.
      - Inaccuracies due to non-uniform illumination
        Radiation calculations with view factors assume uniform illumination over an element, and potentially significant errors may be introduced when this assumption is not fulfilled.
      - Planet view factor calculation without ray-tracing
        The planet view factor is the element's view factor to the planet.
      - Albedo factors calculation without ray-tracing
    - View factor calculation using ray-tracing
    - Plane stress view factor calculation when modeling with axisymetric or 3D elements
      This section explains how the thermal solver computes the view factor for axisymmetric or mixed 2D axi-3D models with plane stress elements for radiation requests.
  - Miscellaneous topics
  - References
- Thermal solver API guide
  Allows you to create or add functionality to enhance the thermal solver capabilities.

Inaccuracies due to non-uniform illumination

Radiation calculations with view factors assume uniform illumination over an element, and potentially significant errors may be introduced when this assumption is not fulfilled.

The cylinder blockage problem, the fence blockage problem, and the small area seeing a large area problem are types of errors introduced by non-uniform illumination.

In the cylinder blockage problem, radiation from element i cannot reach j because of blockage by cylinder k. However, if cylinder k is modeled as a single element and thus has a single reflecting surface, because of the uniform illumination assumption inherent in the view factor definition it is assumed that some of the radiation will be reflected onto j, which is clearly incorrect. To avoid this problem, if a cylinder can cause significant blockage then model its surface with a series of planar elements.

In the fence blockage problem, i and j cannot see each other because they are blocked by fence k. However, the edges of fence k do not line up with element l, which can see both i and j. Since both i and j are assumed to illuminate l uniformly, l incorrectly reflects radiation from i to j. The solution here is to create a mesh so that the edge of l lines up with the edge of k, or, if this is not possible, use smaller elements along the projection of k.

When a small area sees a large area with a large view factor, element k is a small black area that is very close to reflective element i. Element i in turn has a large view factor to black element j. Then, very little of the radiation originating from k should be reflected away from i, most of it should bounce back to k and be re-absorbed. However, because the radiation incident upon i is assumed to be uniform, and radiation is reflected in proportion to the view factors, most of the radiation from k is incorrectly computed to be reflected onto and absorbed by j. The solution here is to subdivide element i into smaller sub-elements.

Highly reflective surfaces and coarse meshes generally aggravate problems due to non-uniform illumination.