Confusion in applying boundary condition

[harshn]

Hi,

I am trying to do a thermal analysis. There is a constant heat source which is a result of radiation energy absorbed from sun's radiation:

Q_sun = (absorption coefficient) * Q_incident

Then there is a wind flowing on the surface which is the convection boundary condition.

How do I implement Natural Boundary (Heat flow) and Mixed boundary (Convection winds) simultaneosly on a thermal element .

Thanks
Harsh

 

[doatis]

Harsh,

You need to use surface effect elements if you want to impose heat flow and convection.

Look up the help for the following:

2.5.2.3. Convections (CONV)
2.5.2.4. Heat Fluxes (HFLUX)

You apply the convection to the surface effect element, and the flux to the solid element.

Hope this helps,
Doug

 

[harshn]

Hi Doug

In the mean time I tried the follwoing and it seems to work, it is on the same lines as you are advising me to follow.

on the top of the model I generated two SURF152 elements, first one KEYOPT(4)=1, KEYOPT(5)= 0 and KEYOPT(8)=1 (heat flux only)

the second srface element has KEYOPT(4)=1 KEYOPT(5)=1 KEYOPT(8)=2 (convection only)

in solution I specify appropriate loading to both types of element using appropriate value in SFE command.

IS this close to what you are suggesting ??

Thanks
Harsh

 

[doatis]

Interesting...never thought of doing it that way.

Yes, that's one way to do it, and is very close to what I suggested. However, you don't have to generate two sets of surf152's. You can apply the heat flux to the underlying thermal solid and then apply the convection to the surf152.

As usual, there's more than one way to skin a cat.