Discussion Forum

Hi

first of all are you sure you have that much "radiation" from a solid to a fluid, compared to conduction and convection ? In particular for your dimensions ?

Have you done a few hand estimates ? these one should always do, even just to chekc that the FEM model is set up correctly

Then if you check your material properties, you will see that a few items are missing, that is why you get the error message

Last thing, when you have such large extend objects, to make the selection and model set up (sometimes too the model post-processing) its is worth to use a second "Definition View" where you have unchecked the "View - Camera - Preserve Aspect ratio" tick box (then update your plots)

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Good luck
Ivar

Hi Ivar

The solid receive the solar radiation and than the fluid receive heat by convection. So i think the correct physics that I have to use are: laminar flow and heat transfer with radiation in participating media.

I corrected the error with material properties.

Its a good idea the view without Preserve Aspect ratio. I did not know this option.


Thanks.


Gustavo

Hi

if it's the external surface that receives solar radiation, you do not need "radiation" in HT, you can use the total heat flux from the sun [W/m^2], somewhere <1500[W/m^2], depending on altitude, sun orientation and air humidity (atmostphere transmission).

The radiation is for radiative exchange between surfaces with stephan Boltzmann law and T^4 behaviour, mostly its negligible for temperatures below a few hundred K, compared to convection and conduction (except perhaps in vacuum when you have no conduction nor convection in the vacued region, but still thermal radiative exchange between internal surfaces)

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Good luck
Ivar

thanks Ivar