Heat Flux question

[pim.krabshuis]

Greetings,

Im trying to simulate heat gain in a double skin facade using a Heat flux BC on the surface of the glass instead of solar heating function. Im using the standard glass material provided by simulation CFD.

My building with de double skin facade is placed with in a big air dome and the heat is not going through my glass material its only emitting it to the outside air volume..

What do i need to do to let the heat transfer go through the glass? Must I edit the glass to give it a transmissivity value and apply a transparent BC?

And the air around the glass with the heat flux BC does not seem to heat up which is a little strange and i dont know how to fix it. My air is set to variable and has a emissivity of 0.3.

thanks for your reply

Pim

[Jon.Wilde]

Hi Pim,

The problem here is that we cannot apply internal surface boundary conditions.

Assuming your heat load is on the outside, you either need to:

1. Run with the heat flux and no externa air
2. Run without the heat flux and use the solar loading which will pass through the air domain to the glass

Does that help?

Kind regards,

Jon

[pim.krabshuis]

Hi Jon,

Thanks for your reply. I will try both but i got some questions.

For option 1. do i need to model the air in the cavity instead?

And for option 2. I tried using the solar heating but with the oriantation settings I used X as north Z as sky and 0,0,-1 as earth gravity. But it dident heat up the south side of my model. Maybe i did something wrong but if i can get a good explanation on how the oriantation of the solar heating works it would be realy great.

Thanks,

Pim

[Jon.Wilde]

Hi Pim,

Which side of the glass are you applying a heat load?

Thanks,

Jon

[pim.krabshuis]

I applied the heat load on the outside of the glass.

[Jon.Wilde · Accepted solution]

OK, then if you have a heat load on the outside with no external air this should work fine.

Of course, you do need to set some ambient reference temperature somewhere, or CFD would not have a starting point. I would typically use a film coefficient to achieve this.

I would have thought that you would want to model the internal air, yes. I would imagine it would need to be variable too, so that you had natural convection occurring? 

Depends on what you are trying to measure though, I'm not sure what the goal is.

Kind regards,

Jon

[pim.krabshuis]

Jon,

Thanks for the feedback I got some good results on both the options now.

For my thesis im researching the effects of a double skin facade and a climate facade and if there are benefits when you combine them(adaptive facade) in diferent climates and seasons.

But I got a little question about rules.

I use Revit 2015 and when I export my model to CFD 2015 I only get *CAD Volume* or *CAD Volume*_U_*CAD Volume* and not the name generation out of Revit Family Catagory : Family Name : Type

Is this a bug? Or is there a way to fix this?

Thanks

Pim

P.S. I just tried the export functions in Revit 2014  to CFD and then I get the good naming of the volumes.