some confusion about the radiation model of Floefd
 

hello everyone:
I am a thermal engineer focus on PCB,though Floefd's radiate model is enough for me.
but still some confusion for me.
1. as the Floefd white paper says: the software using Mote Carlo Radiation Model.
and i have checked few versions embed in SW, only find the sections including Disperse Transfer Radiation Model and Disperse Ordinate Radiation Model.
so why the model is not match with the white paper, and if any mistakes with my code?

2. I also tested the DO radiation model in the Floefd with Fluents when I free.

the aim is simulating the absorption of the semi-transparent part.
both the radiation model choose the DO. also the absorption coefficient are the same.
but the results have a big different.
comparing to the test, the Fluent's result is more reasonable.
the Floefd 's value is much lower,the temperature of the semi-transparent is just 3 degree more than ambient.

the doubts are exhausting me for a long time.

who can help me?

Hi,

FloEFD has three radiation models, depending which module you have.
SW only has two radiation models, also depending which module you have.
The basic version of both has the Discrete Transfer model which is good for tasks where you have no absorption in any kind of semi-transparent solids like glass and therefore good enough for usual PCB thermal simulations.
The white paper refers to FloEFD and FloEFD has more functionalities than SWFS.

I cannot tell what you might have done wrong with the DO model radiation setup but the results I had were always very good within the limits of the DO model itself. So it depends on the model and the setup of the project.

Regards,
Boris

dear Boris:
thank you for your reply first.
and what I need simulate now is the absorption of the semi-transparent solid like glass.
I think it can be solved using DO model according the theory of the DO radiation model, but I cannot find the mistake I have made.
do you know the point need to be noticed in the set?
thank you very much.

Hi,
Yes, the DO model can solve absorption in semi-transparent solids but there are a range of settings that might influence wrong results. I can assume that you used the correct boundary conditions but there might a problem in them and also the model itself and the mesh settings might give wrong results.
For example I just know you want to do a simulation with absorption in semi-transparent solids but don't know what the model looks like. Is it a flat plate as a radiation source or a bulb, do you have a flat glass plate or a lens like body or how does your mesh look like.
I don't even know in what way the results differ from the other simulation tool.
You need to give me more information otherwise it is like 4 equations with 7 unknowns for me. This task I cannot solve with enough information.

Also, why are you trying to use the DO model? Do you have access to the MC model?
The MC model is faster in solver time and more accurate and better suited for some applications. But I cannot tell if yours is such an application as I have no idea what your model looks like.

Boris

yes, and so sorry that I cannot upload the details about the model.
and if possible, can you leave a e-mail address to me? or direct contact me via the e-mail 734771892@qq.com
I can show you the sketch and the aim.
so appreciate your support.