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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 using ray-tracing
Ray-tracing through solid elements
This section describes the methodology for performing ray-tracing within solid elements when solar spectrum extinction or IR spectrum extinction coefficients are defined.

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 using ray-tracing
      - Ray-tracing methodology
        The following topic describes the thermal solver methodology for handling radiation in the presence of diffuse and transparent/specular surfaces using deterministic ray tracing method.
      - Ray-tracing with explicit planet modeling
      - Energy packet strength computation
        To compute the strength of the packets associated with the ray launched from DA_i, an incremental view factor DVF_ij between sub-elements DA_i and DA_j must be computed.
      - Accuracy consideration for ray-tracing
        Accuracy and performance of ray-tracing strongly depend on the elemental subdivision parameter, MESH.
      - Reflected/transmitted energy packet strengths computation
      - Angle dependent surface properties
        This section explains how specular reflectivity or transmissivity is determined for elements based on the angle of incidence.
      - Calculation of ray intercept and direction for curved elements
        This topic describes the procedure for calculating the local surface normal, the point of interception, and the new ray direction for curved elements.
      - Ray termination conditions
        This section outlines the circumstances under which ray termination occurs.
      - Summation of the energy packets to calculate the ray-traced view factors
        This section explains how energy packets are summed to calculate geometric view factors after ray-tracing calculations are completed.
      - Ray-tracing through solid elements
        This section describes the methodology for performing ray-tracing within solid elements when solar spectrum extinction or IR spectrum extinction coefficients are defined.
      - Reciprocity in ray-tracing
        This section explains how reciprocity is handled when calculating view factors with 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.

Ray-tracing through solid elements

This section describes the methodology for performing ray-tracing within solid elements when solar spectrum extinction or IR spectrum extinction coefficients are defined.

In the thermal solver, all surfaces of all solid elements with solar spectrum extinction or IR spectrum extinction coefficients are surfaces coated with perfectly transparent elements, unless a shell element already exists on that surface.

These surface-coated elements will also be considered to be the boundary elements for conduction calculations.
Reverse sides are also created for these surface-coated elements, which are ignored for conduction calculations.
The index of refraction value assigned to the front surface of a surface-coated element facing a solid element. The index of refraction of the reverse side is taken from the adjacent solid element, or, if it is a free surface, is assigned the value 1.

A ray striking one of these elements will be transmitted, and the strength of the transmitted ray will be diminished as it travels through the solid by a factor equal to:

where EXT is the specified extinction coefficient. The lost radiation is written as a view factor from the original source element incident upon the surface-coated element the ray hits on the far side of the solid element.

If all the surface-coated elements facing a solid have the same index of refraction, the solid element is considered to have a zero index of refraction gradient, and the ray path will be straight through it. If, however, there is a variation in the index of refraction, then an index of refraction gradient will be calculated for the solid element, and an appropriate curved path will be calculated for the ray traveling through the solid.

If a ray hits an internal surface-coated element, it is always transmitted into the adjacent solid element. If it hits a surface-coated element whose reverse side faces outwards, a determination is made based on Snell’s Law on whether it exits the solid material or total internal reflection occurs.

Once the calculations are completed, view factors and solar view factors incident upon the surface-coated elements will calculate heat fluxes for these elements, assuming the incident rays are perfectly absorbed by the surface-coated elements.