Solar Wall material issue

[Anonymous]

Hello,

I'm having some problems running a solar heating simulation.

I've already reviewed the AEC tutorials, and I've been trying to get something similar to work.

The thing is, I have an internal natural convection problem due to solar heating with a window. However, when I input the transparent BC to the external surface of the window and I try to run the analysis, it terminates due to "having put a transparent BC on a material with a transmissivity = 0".

I don't know if I've been doing something wrong, because I have selected the "Solar Window" material from the Autodesk Default Material List.

I ran the simulation without the transparent BC, however, no radiation energy seemed to have been let through the window.

Also, I noticed that the value of Transmissivity for the Solar window condition, is shown to be 0 (when I click on the list of properties while assigning the material to a solid). Is that the reason why I'm getting this error?

For the rest of the model, I assigned a custom steel material with a solar wall transmissivity condition. This is supposed to be heated by the sun radiation.

Can you help me with that?

Thank you,

Roberto

[Jon.Wilde]

It sounds like you are using strange boundary conditions.

Some questions:

1. Are you modelling any external air?
2. Do you have solar loading on?
3. Are any of your boundary conditions internal? By this, I mean internal to the outer walls of the entire analysis - this is not permitted. I am not sure why you would need one applied to a window, this does not really make sense
4. Solar Window transmissivity is not zero by default, it should have a SHGC and a U Factor assigned. If you have 'zero' I would guess you assigned the wrong material? Below is what it should look like, by default

I hope this helps,

Jon

[Anonymous]

Thank you for your reply!

1. No I'm not.

2. Yes.

3. They aren't. The transparent condition BC was put on the outer wall of the window.

4. See attachment 🙂

I have also attached the model in question. I ran the entire model with another custom material - One with a user input transmissivity of 0.3 and the analysis actually ran. However, it didn't seem to let any heat from the sun through.

Can you guide me more in detail?

Roberto

[Jon.Wilde · Accepted solution]

I would think you just need to remove the transparent BC, the solar windows are already transparent 🙂

I suggest you also keep an eye on the mesh - you might need a couple of elements through the thickness of those copper pipes to allow for a thermal gradient. An easy way to do this is either a uniform mesh or split the part into two in CAD (so you have a smaller tube inside a larger one).

It runs OK for me without that BC 😉

(Although your mesh is definitely too coarse - this looks 'lumpy')

Hope that helps,

Jon