# emissivity

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 September 8, 2008, 10:46 emissivity #1 Andrea Guest   Posts: n/a Hi guys, I'm working with a radiation problem: a lamp that radiates close to a slab. I'd know the temperature distribution on the slab. When define the boundary condition, I've to set emissivity for the slab wall and shadow, is it right? Or could I use the default value (e=1)? Thanks for your help. Andrea

 September 8, 2008, 13:45 Re: emissivity #2 jay Guest   Posts: n/a If the slab wall is a black body..then only you can set the emissivity as 1. Otherwise..you have to get the emissivity for that slab...and apply..

 September 8, 2008, 14:58 Re: emissivity #3 Andrea Guest   Posts: n/a But I must set emissivity only for wall-shadow (boundary of slab) that is close to air or for wall and wall-shadow? tnx

 September 9, 2008, 00:04 Re: emissivity #4 jay Guest   Posts: n/a you can't set emmisivity for shadow wall.. option available will be only for non-shadow wall.because shaodow wall is a imaginary wall

 September 9, 2008, 03:00 Re: emissivity #5 Andrea Guest   Posts: n/a For DO radiation model, emissivity option is available for both wall and wall-shadow... My doubt is this. Thanks Andrea

 September 20, 2008, 06:00 Re: emissivity #6 gregorio Guest   Posts: n/a Hello, I think you have to set the same emissivity in the wall and in the shadow. The emission and the absorption depend of emissivity. For example you can have a treatment that improves your emission/absorption in one of faces of your wall. In this case you have to set a different emissivity of wall and shadow. One is the emissivity in the direction of the normal of wall and the other in the opposite direction.

 September 20, 2008, 06:54 Re: emissivity #7 Andrea Guest   Posts: n/a Thanks very much Gregorio! I tried the two way and I obtained different solutions... now I'll follow you suggests. Andrea

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