Discussion Groups

## Simulation Mechanical and Multiphysics

Contributor
Posts: 22
Registered: ‎04-02-2011

# Heat Flow Calculation

841 Views, 4 Replies
04-28-2011 02:12 PM

Hello!

I have a question and hope that you will help me.

While doing some of the  tutorials I came across the "Heat Flow Calculation"-setting in Edit - Element Data. today, but although I read the paragraph about it in the wiki I still do not completly understand what it means. Can someone give an understandable explanation on the difference between Projected at Centroid, Nonlinear Based on BC and Linear Based on BC?

Kind regards,

Walter

Employee
Posts: 259
Registered: ‎06-14-2010

# Re: Heat Flow Calculation

04-29-2011 08:38 AM in reply to: jones79

The wiki already gives the information for the basic differences. Here I am trying to clarify and help to understand the options.
To answer your question, some basic knowledge of heat transfer and numerical approaches need to be reiterated here.
(a) Three basic heat transfers and how the thermal BCs applied
Heat conduction, convection and radiation are three kinds of heat transfer. As a general thermal analysis package, we cover all of them including the corresponding BCs.
(b) Relationship between temperature and heat flux/heat rate
Heat flux is the temperature derivative in space, i.e. Heat flux=constant*dT/dx(Fourier's law), here T is temperature, from this point of view, they are dependent.
(c) Primary variable and derived variable in heat transfer and numerical analysis
In numerical heat transfer in FEA, nodal temperature is the primary variable to be solved in solver (major effort here) , while heat flux is the derived variable from above space derivative relation. As one of thermal boundary conditions, the radiation effect is enforced from heat flux of part exterior surfaces.

Note the three "Heat Flow Calculation" options in element definition are used to handle the thermal boundary conditions from radiation and convection, which bring nonlinear effect.
Here are the differences for three kinds of heat flux.
(1) Projected at Centroid
Calculate heat flux by nodal temperature at element centroid from Heat flux=constant*dT/dx(Fourier's law), and use it to calculate element face heat rate by
Element face heat flux= normal projection component of element Centroid heat rate *element face area
This is the regular expression in numerical heat transfer, and is used in thermal post-processor.
(2) Nonlinear Based on BC
To count the thermal boundary condition from convection or radiation loads, the heat rate (integration from flux) of the part exterior surfaces is calculated from convection, radiation boundary conditions and contribution of nodal temperatures as in (1)
The name of nonlinear comes from the nonlinear nature of radiation loads.
(3) Linear Based on BC
This option is close to (2) except heat flux on surfaces with radiation loads is linearized.

Jianhui Xie, Ph.D
Principal Engineer
MFG-Digital Simulation
Contributor
Posts: 22
Registered: ‎04-02-2011

# Re: Heat Flow Calculation

04-29-2011 02:22 PM in reply to: Joey.X

Thumbs up! Thanks for the good explanation!

Maybe some of the details could be merged into the wiki

Do you know if there are other documents available (e. g. course material), beside the official user guide and the wiki, from which one can learn how to use Autodesk Simulation/Multiphysics ?

Kind regards,

Walter

Contributor
Posts: 12
Registered: ‎06-18-2008

# Re: Heat Flow Calculation

02-08-2013 10:45 AM in reply to: jones79

I also would be interested in finding some more literature that covers the setup of thermal analysis as well as dynamic MES analysis. Some more tutorials or course materials of that nature, downloadable or for purchase.

Thank you.

Employee
Posts: 89
Registered: ‎10-27-2009

# Re: Heat Flow Calculation

02-15-2013 06:20 AM in reply to: jm74jensen

Take a look at the following link for In-person training: Training

You can also go through the training manuals on your own time by purchasing the books from the following e-store

Training manuals

-Sualp