Radiation Analysis

[adampar]

Hi everyone,

i use Femap 11.1 with NX Nastran v9.0. My basic license includes Steady state Heat Transfer and i would like to use it to perform a radiation analysis with sun as a source to a truss in orbit (although i analyse the structure being at a specific point). Is there a capability of the program to model radiation on 1D elements, or do i have to change my model to 2D or even 3D??

 

[BlasMolero]

Dear Adampar,
iN FACT, Radiation is supported BY DEFAULT in FEMAP with NX NASTRAN, the basic license of NX NASTRAN support Steady state (SOL153) and transient (SOL159) heat transfer analysis with conduction, convection and radiation. But the part of radiation suported in the Graphic User Interface (GUI) of FEMAP WITH NX NASTRAN only runs with surface elements, not possible to define radiation using 1-D CROD elements, unless NX NASTRAN internally support the definition of radiation on line elements, take a look to the command CHBDYP:

The types of radiation boundary condition supported in FEMAP WITH NX NASTRAN are Radiation to Space and Radiation Enclosures.
• Radiation to space is a boundary condition which defines radiant exchange between a finite ele­ment surface (face) and blackbody space. The inputs required for radiation to space are: the absorptivity and emissivity of the element surface, the ambient temperature of space, and the radiation view factor between the surface and space (usually equal to 1.0). The absorptivity and emissivity can both be temperature dependent and the ambient temperature can vary with time.
• Radiation Enclosure exchange is similar to the Radiation to Space boundary condition, however this type of boundary condition takes into account the radiation exchange between finite element surfaces. As a result, the geometric relationship (view factor) between individual finite element surfaces needs to be determined. For enclosure radiation the view factors between surfaces are internally calculated. Also for enclosure radiation the absorptivity is taken as being equal to the emissivity.


But here we are FEMAP TMG/THERMAL that can use 1-D Bar, Beam, Tapered Beam and Curved Beam elements for Radiation Modeling, this is an add-on module of FEMAP that requires a license (take a look

http://www.iberisa.com/productos/femap/femap_advanced_thermal.htm).

FEMAP TMG/THERMAL solver uses internally the 1-D element's perimeter from its cross section definition and constructs an equivalent six-sided cylinder. The view factors for the six faces are computed individually then merged together. Only 1-D elements with emissivity defined can radiate or block radiation. For 1-D elements, the reverse side optical material properties are ignored; 1-D elements do not have a reverse side.
FEMAP TMG/THERMAL solver is really powerful modeling Thermal Effects of an Orbit. You can use "Orbit Modeling" command to request solar, albedo, and planet view factor calculations for selected elements within a defined orbit. You can also define orbits or orbital maneuvers by specifying time-varying sun and planet vectors. You can preview a defined orbit prior to solving the model with the Orbit Display option. Orbital view factors and heat fluxes may be recovered for post-processing and visualization, impressing!!.

Best regards,
Blas.

~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director

IBERISA
48004 BILBAO (SPAIN)
WEB:

http://www.iberisa.com

Blog de FEMAP & NX Nastran:

http://iberisa.wordpress.com/

 

[adampar]

Quite illuminating! Thank you very much, you have been very helpful also many times in the past with your posts.