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Radiation between solid domains in vacuum..

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Old   June 24, 2011, 23:30
Default Radiation between solid domains in vacuum..
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Kim, Chang gon
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I have no idea how I can simulate radiation heat transfer between 'Solid' and 'Solid' domiain. Two solid have no contact in vacuum.

I found some examples in tutorial about fluid-solid or fluid-fluid radiation, but no solid-solid radiation.
Only I know is that monte carlo option is available.

Any advices or example/tutorial links are helpful for me.
Please show me the way..
thank you.
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Old   June 25, 2011, 07:58
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You should be able to do this with the discrete transfer model as well. It is a lot cheaper than monte carlo. You should be able to get the radiation to transfer between the interfaces on the outside of the solid domains. Also note you will have to mesh the region in between the solid domains for the radiation to transfer through it. If it is a vacuum and has no fluid in it you can just fill it with air and turn the fluids and heat transfer solver off with expert parameters and then the air will not move or conduct heat so will act like a vacuum.
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Old   June 26, 2011, 01:55
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Thank you for advise.
I looked up 'expert parameters'.
Now I can insert expert parameters in CFX-Pre Solver, but there are only 't-f' selection. And still i don't know what option is related with my case.
Could you or anybody tell me what should I do next step?
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Old   June 26, 2011, 07:17
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What is in between the objects? Is it a total vacuum, or is there some fluid flow? Is the only heat transfer mechanism radiation?
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Old   June 26, 2011, 08:53
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It can be assumed as vacuum between solid and solid domain.

I want to see a temperature map of a pipe.
Coolant flow is inside of it, and the radiation source(another solid) is apart from pipe.

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Old   June 26, 2011, 12:15
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Hi Kim,

Your problem seems interesting. Maybe I have not understood it well, but I think, that there is no vacuum between two pipes. I think air (or another gas) is present. If yes, you may proceed with fluid between the pipes.

But if there is really a vacuum, then you may try following trick (I think this should work. I have not tried it yet. So please let me know if it works.) (I would also appreciate if Glenn could comment on this)

Define a fluid with density, viscosity & other HT properties equal to zero (Maybe solver wont allow you to define the values equal to zero. Try to define it as low as possible.) However define the radiation property carefully. Then define this fluid as operating fluid. And proceed further.

Hope this helps.

Regards,

-Sanyo
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Old   June 26, 2011, 22:22
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You have two choices - either define a fluid with very low thermal conductivity, low density but I suspect high viscosity would help (you cannot use zero for these parameters, the solver will barf). Or you can turn the fluids solver off with expert parameters.
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Old   July 19, 2018, 18:28
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Quote:
Originally Posted by ghorrocks View Post
You should be able to do this with the discrete transfer model as well. It is a lot cheaper than monte carlo. You should be able to get the radiation to transfer between the interfaces on the outside of the solid domains. Also note you will have to mesh the region in between the solid domains for the radiation to transfer through it. If it is a vacuum and has no fluid in it you can just fill it with air and turn the fluids and heat transfer solver off with expert parameters and then the air will not move or conduct heat so will act like a vacuum.
Dear Glenn Horrocks, from past few days i am searching for this case and you had given the right solution seems to be you are experienced paramater setup for radiation model, i wanted to know how to give this expert parameters, can any assist me, possible with snap shots
Thanks
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Old   July 19, 2018, 19:20
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Expert parameters are one of the menu options in CFX-Pre. Look in the CFX-Pre documentation if you cannot find it.
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