Auto Enclosure Model option in boundary condition

[Edin Mer]

What is the difference when using Auto Enclosure Model  in boundary condition for interior?

I made a model of a glazing system. With Auto Enclosure Model option OFF the U-factor of the frame is 7 W/m2K 

and the same model with Auto Enclosure Model option ON gives a much higher value of U-factor 11.15 W/m2K.

Can somebody tell me if it has to be turned ON or OFF and in which cases?

Edd

[D. Charlie Curcija/LBNL]

I am not sure that I understand what do you mean by: Auto Enclosure Model option OFF. Where did you turn it OFF?

[Marles McDonald]

Charlie, If this is a new, unprotected comprehensive boundary condition with radiation model checked, autoenclosure  is turned off completely if black body or linear radiation is selected.
Hope this helps, perhaps Edin could send you the BC library so you could look at it
Marles

On Wednesday, June 18, 2014 8:02:01 PM UTC-7, Edin Mer wrote:

[D. Charlie Curcija/LBNL]

OK, so this is not turning it OFF, but choice between autoenclosure, black body or linear radiation. Autoenclosure generally produce lower, not higher results for Aluminum windows and the reason is more realistic radiation model that tend to decrease radiation, since black body and linear radiation tend to overestimate radiation heat transfer. If the linear radiation heat transfer coefficient is artificially low, then this would produce lower heat transfer than detailed (Auto Enclosure and Manual Enclosure) models. My recommendation is to use Auto Enclosure whenever possible, since this is the most accurate method.

Charlie

[Edin Mer]

Thanks for the answer, Charlie.

Attached is the screenshot showing that when using a custom boundary condition with Auto enclosure gives higher value of U-factor for the frame compared to boundary condition without Auto enclosure. I am attaching the Therm 7.2 file, too.

Edin

[Edin Mer]

I read your answer one more time carefully. The first time I read your answer I was still sleepy. I see you are saying what I just sent in the attached screenshot. 

Everything is OK now.

Thank you again for the answer,

Edin