[chrisf90]

Hi everybody,

For my work I try to simulate heat transfer and fluid flow in double skin facades and therefore also for windows (double glazing).

A sketch of the problem setup is attached: There are simply 2 solid zones made out of glas and a air gap between those.
The transmittance for short- and longwave radiation of the glazing was modelled with to bands: absorption coeff. 30 for shortwave rad. (solar) and 3000 for longwave rad. (thermal). As solar source there was irradiation (1000W/m²) for the shortwave band at the external surface applied.

The solution seems to be reasonable but I am facing some problems with post-processing different fluxes in the surface integral reports at the internal glas surface:
1) Total heat flux is negative which makes sence because energy is leaving the domain there
2) radiation heat flux is also negative which makes also sence because of the transmittance of glaz for shortwave radiation. But how is this flux calculated? Is it the sum of the transmitted radiation flux of both wavelenght bands?
I am really confused because there are some pretty high values for the transmitted radiation flux for the longwave radiation?!
Shouldn't that value be much smaller because of the high absorption coeff. for this band.
3) My last question: is there a possibility to obtain only the conduction part of the total heat transfer through the window?

Any advice would be highly appreciated.

Cheers
Chris

[sasa mohamed]

Dear Christoph Ferk,
Did you receive a solution to this problem because I am facing the same but I cant overcome this problem. Moreover that, the direct irradiance don't transmit from the first glass layer as well as I have a negative radiation heat flux on the other side of the first glass layer.

thanks in advance,

regards,
mostafa