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## Simulation CFD

Valued Contributor
Posts: 65
Registered: ‎10-31-2012

# time step for a transient run with TECs

133 Views, 2 Replies
03-27-2014 07:21 AM

Dear Autodesk CFD experts,

I am running a transient case that contains several thermoelectric cooling devices.  I also have several fans in the model, hence, a forced convection case.  So, I solved the case to steady state with flow only, then, followed by solving for the temperature field with frozen flow.  In this case, I can use a larger time step.  However, I found that, the results when I used 4 seconds for time step are different from the results when I used 1 second for the time step.  This seemed to be due to the TEC model.  Any general guideline on time step for TECs?

Thanks!

Pei-Ying

Product Support
Posts: 645
Registered: ‎08-24-2011

# Re: time step for a transient run with TECs

03-27-2014 04:44 PM in reply to: pei-ying.hsieh

The TEC model really doesn't support transient analysis, especially when this is what you are looking to study.  When you examine the governing equations, the TEC has to thermal mass.  Might be something you would want to include in the idea station.

Best regards,

Royce Abel
Valued Contributor
Posts: 65
Registered: ‎10-31-2012

# Re: time step for a transient run with TECs

03-28-2014 04:55 AM in reply to: pei-ying.hsieh

Hi, Royce,

I do not understand why the TEC does not support transient case.  Basically, the TEC model computes heat flux on the cold side and heat flux on the hot side based on temperature difference between the hot side and the cold side and the parametes like Seebeck coef, resistivity, conductivity, and current (or voltage).  Basically, at each time step, the solver looks up the average temperature on the cold side and the average temperature on the hot side and the compute the heat fluxes on both side, use them as BCs to the fluid/solid domain.  In this case, I do not understand why delta t will make a big difference (as long as it is not too big).

Pei-Ying