Radiation between solid domains in vacuum..

Kim CK · June 24, 2011, 23:30

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.

ghorrocks · June 25, 2011, 07:58

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.

Kim CK · June 26, 2011, 01:55

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?

ghorrocks · June 26, 2011, 07:17

What is in between the objects? Is it a total vacuum, or is there some fluid flow? Is the only heat transfer mechanism radiation?

Kim CK · June 26, 2011, 08:53

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.

thank you

Sanyo · June 26, 2011, 12:15

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

ghorrocks · June 26, 2011, 22:22

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.

vijaybr1993 · July 19, 2018, 18:28

Quote:

Originally Posted by ghorrocks

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

ghorrocks · July 19, 2018, 19:20

Expert parameters are one of the menu options in CFX-Pre. Look in the CFX-Pre documentation if you cannot find it.

June 24, 2011, 23:30	Radiation between solid domains in vacuum..	#1
Kim CK New Member Kim, Chang gon Join Date: Jun 2011 Posts: 4 Rep Power: 15	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.

June 26, 2011, 01:55	:)	#3
Kim CK New Member Kim, Chang gon Join Date: Jun 2011 Posts: 4 Rep Power: 15	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?

June 26, 2011, 08:53	vacuum.	#5
Kim CK New Member Kim, Chang gon Join Date: Jun 2011 Posts: 4 Rep Power: 15	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. thank you

July 19, 2018, 19:20		#9
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,871 Rep Power: 144	Expert parameters are one of the menu options in CFX-Pre. Look in the CFX-Pre documentation if you cannot find it. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

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June 25, 2011, 07:58		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,871 Rep Power: 144	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.

June 26, 2011, 07:17		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,871 Rep Power: 144	What is in between the objects? Is it a total vacuum, or is there some fluid flow? Is the only heat transfer mechanism radiation?

June 26, 2011, 12:15		#6
Sanyo Member Sanyo Join Date: Apr 2009 Location: India Posts: 62 Rep Power: 17	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

June 26, 2011, 22:22		#7
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,871 Rep Power: 144	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.