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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.
Hydraulic network analysis
When the hydraulic pressure-flow network is present in the model, the thermal solver solves it at each iteration or time step using the following algorithm.
Nozzles and diffusers
The thermal solver computes the flow resistance factor for nozzles and diffusers based on the angles α and β, and various coefficients.

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 reference
  Describes the format and contents of the thermal solver's input and output files
- 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.
  - Elements in the thermal solver
    The thermal solver uses elements to calculate conductive, convective, and radiative conductances, as well as hydraulic resistances.
  - Supported element types for radiation
    Radiating elements may be defined with 1 to 4 corner nodes. The elements may be linear or parabolic.
  - 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.
  - Steady state analysis
    In a steady state analysis, the thermal solver solves the temperatures of non-sink elements iteratively using the following algorithm.
  - Transient analysis
    Transient analysis is performed using the following algorithm.
  - Hydraulic network analysis
    When the hydraulic pressure-flow network is present in the model, the thermal solver solves it at each iteration or time step using the following algorithm.
    - Hydraulic flow resistances for incompressible flows
      Hydraulic resistances are modeled with 2-node hydraulic elements.
    - Straight ducts
      For straight ducts, the flow is assumed to be fully developed, and the flow resistance factor (RF) is calculated using a specific formula based on duct characteristics.
    - Nozzles and diffusers
      The thermal solver computes the flow resistance factor for nozzles and diffusers based on the angles α and β, and various coefficients.
    - Duct geometry consideration for rough and curved ducts
      For fully developed flow through straight, smooth ducts, the thermal solver supports a wide range of friction factor and heat transfer correlations for different duct geometries.
    - Rough duct correlations
      Rough duct correlations use different friction factors for laminar, turbulent, and transitional flow. Nusselt numbers used in the correlations for rough ducts also change depending to flow conditions.
    - Head loss coefficients in curved ducts
      Understanding the pressure loss in bends using head loss coefficients for both laminar and turbulent flow conditions.
    - Heat transfer correlations in curved ducts
      Understanding heat transfer coefficients in curved ducts and the proposed correlation for different bend angles.
    - Head loss in sharp duct bends and duct branches
      The thermal solver uses the head loss in sharp duct bends and duct branches.
    - One-way conductance
      Modeling the heat transported by the fluid through one-way conductance for each flow resistance.
  - Miscellaneous topics
  - Thermal solver theory bibliography
    The following bibliography lists all sources used to explain how the thermal solver works.
- Thermal solver API
  Allows you to create or add functionality to enhance the thermal solver capabilities.
- Thermal solver error message list
  Lists solver messages that the thermal solver generates to communicate issues with the model or the solve.

Nozzles and diffusers

The thermal solver computes the flow resistance factor for nozzles and diffusers based on the angles α and β, and various coefficients.

The angles α and β are defined [12]:

where:

SE1 is the larger side of the exit
SE2 is the larger side of the inlet
SI1 is the smaller side of the exit
SI2 is the smaller side of the inlet
L_D is the length of the nozzle or diffuser

α is assumed grater than β. If α < β, the two are reversed. α can take on a maximum value of 40 degrees. If α > 40 degrees, α = 40 degrees is used.

Next, a friction coefficient is defined:

for β > 0.5 degrees, and

for β < 0.5 degrees.

where:

A1 is the area at the narrower end.
A2 is the area at the larger end.
ψ_FR is the friction coefficient.

For diffusers, a shock and an expansion coefficient are defined at the narrower end:

where:

ψ_EXP is the shock coefficient.
Z_EXP is the expansion coefficient.

Then the flow resistance factor for a diffuser is:

For nozzles, a length to hydraulic diameter ratio is defined:

where:

D1 is the hydraulic diameter at the narrower end.
R_LD is the length to hydraulic diameter ratio.

Next, an interpolation parameter R_INT is computed:

Next, the parameter Z' is defined and the flow expansion coefficient Z_EXP is calculated:

Then the flow resistance factor for a nozzle is: