Can I do this in thermal analysis?

[alan_ambrose]

Hi, I'm getting on OK with thermal - it's quite easy to use. I've got a simple basement external stairwell modelled with concrete and XPS insulation. The boundary conditions are all temperatures. This kind of thing (below). The grey stuff is concrete, the red stuff is XPS insulation, the blackish looking thing is some glass doors. I'm trying to figure (a) a reasonable scheme for insulation, (b) the resulting heat loss into the stairwell. Intuitively, from the temperature plot, the 'maximum XPS' design shown below looks fine - I can't see any obvious thermal bridges that are causing problems. But, is there a way to quantity that and find the overall heat loss into the stairwell (which I'm looking for as an input to PHPP analysis software)? That is, total heat flux and/or U-Value through the plane encompassing the window? Seems to me, if not, these are just pretty pictures, no?

As a final question, is there a tutorial somewhere that shows how to do multiple simulations (say, with different insulation schemes) and compare the results? I would like to remove panels of insulation and see the impact on the thermal loss analysis and thus determine how valuable each XPS panel is.

TIA, Alan

[alan_ambrose]

To add: this is what the heat flux looks like perpendicular to the window:

[henderh]

Hi @alan_ambrose,

As you've discovered, we don't currently offer a result for a total heat transfer through objects. We have this requirement recorded in our internal system as FUS-118433.

For multiple simulations with different model schemes, cloning a Simulation Model is the easiest way to accomplish this.

1. With the study set up in Simulation Model 1, go to the Simplify workspace
2. Right-click on the Simulation Model 1 browser node > 'Clone Simulation Model'
3. OK to include cloning the Simulation Study
4. Make the necessary geometry changes for Simulation Model 2
5. Return to the Setup workspace, and make any changes needed in the cloned Simulation Study

The Thermal Analysis tutorial describes a similar workflow, but creates a New Simulation Model and study instead of cloning a Simulation Model + Study.

If you're not changing the model geometry, and only changing the insulation material, you can right-click on the study in the Setup workspace > 'Clone Study'. In both cases, the Compare workspace can be used to compare results between studies that are contained within the same design document.

Best regards,

[alan_ambrose]

OK thanks. I'm going to suggest that while the temperature results look 'plausible', the whole thermal analysis suite looks buggy. In particular:

(1) While I realise FEA as a numerical method can come up with oddities and glitches, in this case we're dealing with an easy heated geometry and the heat simply leaks out of the geometry to the surroundings. As none of the boundary conditions has a temperature above 20 degrees and there is no heat source, is it really plausible that there a point that is at 21.6?

(2) I'm not convinced the thermal gradient and heat flux results are valid. If you look at the Z heat flux above, you can see that the numbers change sign over the surface. That doesn't make any sense - in general the heat is just leaking out of the building, so it's going in one direction only - towards the outside.

Unfortunately at $10 a shot I'm reluctant to spend my money validating the Autodesk software. I note there's no training that I've seen that mentions heat flux or thermal gradient, only temperature, so I wonder whether this is a niche feature that isn't really supported?

[henderh]

Hi @alan_ambrose,

I agree with you the temperature result value higher than the applied temperature is very suspect.

This can happen if (for example) mesh is not refined enough. A technical solution explains when this behavior can happen, and how to adjust for it: Temperature results of a simulation are out of range

If the results are still not satisfactory, I can ask the solver team to investigate if you attach the Fusion design with the setup (File > Export... > f3d or f3z file type).