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Thermal analysis Guide
1.1.1. Convection
You specify convection as a surface load on conducting solid elements or shell elements. You specify the convection film coefficient and the bulk fluid temperature at a surface; ANSYS then calculates the appropriate heat transfer across that surface. If the film coefficient depends upon temperature, you specify a table of temperatures along with the corresponding values of film coefficient at each temperature.
For use in finite element models with conducting bar elements (which do not allow a convection surface load), or in cases where the bulk fluid temperature is not known in advance, ANSYS offers a convection element named
LINK34. In addition, you can use the FLOTRAN CFD elements to simulate details of the convection process, such as fluid velocities, local values of film coefficient and heat flux, and temperature distributions in both fluid and solid regions.
1.1.2. Radiation
ANSYS can solve radiation problems, which are nonlinear, in four ways:
- By using the radiation link element, LINK31
- By using surface effect elements with the radiation option (SURF151 in 2-D modeling or SURF152 in 3-D modeling)
- By generating a radiation matrix in AUX12 and using it as a superelement in a thermal analysis.
- By using the Radiosity Solver method.
For detailed information on these methods, see
"Radiation".
1.1.3. Special Effects
In addition to the three modes of heat transfer, you can account for special effects such as change of phase (melting or freezing) and internal heat generation (due to Joule heating, for example). For instance, you can use the thermal mass element
MASS71 to specify temperature-dependent heat generation rates.
1.1.4. Far-Field Elements
Far-field elements allow you to model the effects of far-field decay without having to specify assumed boundary conditions at the exterior of the model. A single layer of elements is used to represent an exterior sub-domain of semi-infinite extent. For more information, see
Far-Field Elements in the
Low-Frequency Electromagnetic Analysis Guide.