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Modelling solar radiation / black body radiator?

Posted Jan 25, 2011, 12:24 p.m. EST Heat Transfer & Phase Change, Geometry, Materials, Modeling Tools & Definitions, Parameters, Variables, & Functions, Results & Visualization, Studies & Solvers Version 4.1 3 Replies

Fabrice Motte
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Hello everybody.


I would like to model accurately the thermal behavior of a flat plate solar collector.
(from the top to the bottom : a glass cover, an air layer, a radiation absorbeur and a thermal insulation).

I did a first model (2D and 3D) using an input energy flux on the top boundary of the glass cover. But I'm not really satisfied with this configuration :
It seems that in this case, Comsol is working in conduction/convection only, and did not take into account that the incident flux type is radiative. I would like to traduce the fact that the glass cover is opaque to the IR radiation and transparent to the UV radiation.

I've tried to model a black body radiator with the surface to surface radiation module (heat transfer)... but it didn't work.

Does someone know how I could manage that?


Thanks a lot for your answers

Fabrice
3 Replies Last Post May 3, 2012, 3:22 p.m. EDT
COMSOL Moderator

Hello Fabrice Motte

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RONG XU
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Posted: 1 decade ago Apr 7, 2011, 12:13 p.m. EDT
Have u figure it out. I am also in this area too.
PS: You could change the equation system such as add a new flux term in it.
Have u figure it out. I am also in this area too. PS: You could change the equation system such as add a new flux term in it.
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Apr 8, 2011, 4:01 a.m. EDT
Hi

by default the wavelength is a constant (or scanned over via a parameter or frequency domain) you need it as a variable to integrate over.

Either you can estimate the transmission and use that as an interpolated (or analytical) function to do the integration, or you would need to make a parametric run for different wavelengths, adapt the emissivity and transmission of your material for the different wavelengths and integrate over the wavelengths to get total power out

--
Good luck
Ivar
Hi by default the wavelength is a constant (or scanned over via a parameter or frequency domain) you need it as a variable to integrate over. Either you can estimate the transmission and use that as an interpolated (or analytical) function to do the integration, or you would need to make a parametric run for different wavelengths, adapt the emissivity and transmission of your material for the different wavelengths and integrate over the wavelengths to get total power out -- Good luck Ivar
Dr Christopher Leung
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Posted: 1 decade ago May 3, 2012, 3:22 p.m. EDT
Hello Fabrice + All,

I am trying to model and simulate a solar heated enclosure too, I have same obstacle. There was a Webcast today (Tech Briefs media) on heat-transfer by radiation that shows a feature that models + simulates a solar radiation source (in COMSOL 4.3). I have asked panel if this differentiates for the absorbtion and emissivity of materials, specifically shortware incident (from sun) from long wavelength. The answer was exchange is modelled as gray i.e. averaged.

I am trying to do same step of modelling the black-body radiation (longwave length 10mu m) emissive loss from inside the solar heated enclosure to back of glass. Then again from the outside of the glass to outside air.

I just realised after listening to the presenter of the webcast that air may be treated as a 'participating media' for the absorption of longwave length emission from the outside of the collector's glass cover. This might help you.

Regards

Christopher

Hello Fabrice + All, I am trying to model and simulate a solar heated enclosure too, I have same obstacle. There was a Webcast today (Tech Briefs media) on heat-transfer by radiation that shows a feature that models + simulates a solar radiation source (in COMSOL 4.3). I have asked panel if this differentiates for the absorbtion and emissivity of materials, specifically shortware incident (from sun) from long wavelength. The answer was exchange is modelled as gray i.e. averaged. I am trying to do same step of modelling the black-body radiation (longwave length 10mu m) emissive loss from inside the solar heated enclosure to back of glass. Then again from the outside of the glass to outside air. I just realised after listening to the presenter of the webcast that air may be treated as a 'participating media' for the absorption of longwave length emission from the outside of the collector's glass cover. This might help you. Regards Christopher

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