Elmer Discussion Forum

Hi, Does it decrease below 293 K? --> Yes it goes to 292,62K I assume that your convection BC is on top of the small block? --> The Convection BC is on all surfaces (I grouped them in Salome to one boundary) Where do you monitor the temperature - somewhere on the big block? --> Yes What happens if y...

I thought it's better to upload pictures cause it was so huge. I don't see the ads because I've installed an adblocker. The sketch: the big Block is made of COC the small block is made of aluminium and that's the heat source Inside the big block are some little channels with still water. sketch.png ...

Hello their, I simulate a heatflow problem again. Boundings conditions: T of the surrounding air: 293K (no radiation) heat source: T of a volume element: 343 initial temperature at the complete volume: 293 If I display the temperature over time I get the following diagram: http://fs2.directupload.ne...

Thanks Mark

Okay thx,

now I understand what you mean. But which heat transfer coefficient I should set?

In some papers I found the approximation of the heat transfer coefficient in still air. They use 10 W/(m^2*K).

Which value would you use?

Thanks

Okay thanks,

there are further questions. How I define the natural convection.

I set the convection to "constant".

• - Which convection (1,2,3) velocity I should use and which value I have to use?
  - I set the boundary conditions to external temperature (293K). That's right?

Thanks

Hello there, I don't know whether my model is correct. I try to simulate the heatflow in a volume. It's surrounded by air. How I should define the bounding conditions at the surfaces? Should I model a volume of air around the volume or could I set the surfaces to the surround temperature (293K)? Tha...

Mzenker you made my day.

I mind that FreeCAD exports in metre but I would have never thought that Salome converts the units...

After you advices it works very well.

Thank you

Hello, I don't like crossposting but my problem is quite similar to yours. With temperature gradients of different boundaries I could not simulate a transient Simulation. That works only with a heat source (W/kg a.s.o). Also bodywise Dirichlet conditions does not work. Does anybody know why not? Tha...

Hello mzenker, I used the Salome Tutorial successfully. There are only some requirements to the original geometry. The partial bodies should not have self-intersections. Otherwise the Connection is not good and the mesh generator Needs a lot of time. Salome has a tool in "Measure" to detec...