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Andrea September 8, 2008 10:46

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.


jay September 8, 2008 13:45

Re: emissivity
If the slab wall is a black body..then only you can set the emissivity as 1. have to get the emissivity for that slab...and apply..

Andrea September 8, 2008 14:58

Re: emissivity
But I must set emissivity only for wall-shadow (boundary of slab) that is close to air or for wall and wall-shadow? tnx

jay September 9, 2008 00:04

Re: emissivity
you can't set emmisivity for shadow wall..

option available will be only for non-shadow wall.because shaodow wall is a imaginary wall

Andrea September 9, 2008 03:00

Re: emissivity
For DO radiation model, emissivity option is available for both wall and wall-shadow... My doubt is this. Thanks


gregorio September 20, 2008 06:00

Re: emissivity
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.

Andrea September 20, 2008 06:54

Re: emissivity
Thanks very much Gregorio! I tried the two way and I obtained different solutions... now I'll follow you suggests.


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