Home
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
Planet view factor calculation without ray-tracing
The planet view factor is the element's view factor to the planet.

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.

Planet view factor calculation without ray-tracing

The planet view factor is the element's view factor to the planet.

To calculate the planet view factor, first, a preliminary viewing check is performed to see whether the element's surface sees any part of the planet.

Lump mass and beam elements can always see the planet.

If the shadowing option is requested, a preliminary blockage check is performed to screen out the shadowing surfaces that cannot block the planet.

If after the screening some possibly shadowing surfaces exist, the planet blockage factor is calculated:

The planet is subdivided into 4×MESH² sub-elements, while element i is subdivided into MESH²×NV sub-elements DA_i.
The view from each sub-element NV×MESH² to each planet sub-element is then examined for blockage by checking whether any of the possibly shadowing surfaces interrupts their centroids' views of each other.
An incremental planet view factor DEVF_i is calculated with the Nusselt sphere technique for each sub-element DA_i.
The planet blockage factor for element i, PBF_i, is then defined as:
where:
- DEVF_mknb is the incremental view factor from the m^th sub-element of element i to the k^th sub-element of planet, calculated with the Nusselt sphere technique without blockage.
- DEVF_mkb is the incremental view factor from the m^th sub-element of element i to the k^th sub-element of planet, calculated with the Nusselt sphere technique with blockage.

The planet blockage factor equal one if there is full blockage, and zero if there is no blockage.

After the planet blockage factor is calculated, the unshadowed planet view factor (UPVF) is calculated with the analytical expression for the view factor from a small planar area to a very large sphere. Cylindrical two-node elements are approximated as equivalent surface area square cross-section rods, and lump masses are approximated as equivalent area cubes.

Then, the shadowed planet view factor is given by: