Air layer or Boundary cond.

[avp081090]

Hello

In currently working on modelling a window frame. In the frame there is some ventilated indentations. This air space can be seen highlightend in red on the attached picture.

My question is:

Should i make anisotropic air layers or just ad outside boundary conditions?

On of the main task is to see if the window is ventilated enough so that moisture won´t stack up.

Best regards

[avp081090]

BTW. If it should be boundary conditions, should the sides have different conditions as the orientation are different?
Since none of them are oblique, four different conditions would be enough: 0, 90, 180 and 270 deg?

best regards

[Christian Bludau]

Hello,
the easy way would be to us a exterior climate (without radiation and rain so you need no orientation) bit if you like to compare the needed ventilation, you have to insert an air layer (isotropic or anisotropic should do no big difference) and adapt an air change source. Here you can set the air change rate and by this way compare different rates.
Christian

[avp081090]

okay, so there is no way for wufi to inform me about the air change rate? I just mean, I have no way of knowing the air change in that "pocket".

[avp081090]

BTW the surfaces should not have a short wave absorptivity, but still the long waved emissivity right? I was wondering, since there is no grid inbetween the surfaces, can they then emit on one another or should air be inserted ?

best regards

[Christian Bludau]

If you use boundary conditions in your gap, the long emissivity is calculated to the atmosphere. If you want to fill the gap with air, you have to draw new layers inside and assign air. The material data for the air layers based on effective µ and lambda values including assumptions for convection and radiation. Please also see the materials "Info Text", you will find that for each material in the database.
Christian