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heat transfer from solid with fixed wall temp to fluid

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Old   March 3, 2018, 15:43
Default heat transfer from solid with fixed wall temp to fluid
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Hello,

I want to set in CFX fixed temperature to one wall and want to simulate heat transfer from this wall to another fluid domain. When I set fixed temp there is no heat transfer to the air. Is it ok to set also boundary for the same wall in air domain as fixed temperature? Or is there any other way?

Thank you very much
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Old   March 4, 2018, 05:36
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Yes, you can do this. If you are getting no heat transfer something is wrong with your setup. Is this a single domain or multi domain simulation?
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Old   March 4, 2018, 06:20
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Thank you for your answer. There is no heat transfer because as soon as you set fixed temp for that face the interface between fluid and solid disappears and therefore there is no conservative interface flux. I just wanted to know of the physics is the same when I set the fixed temp for the same face in both domains. I also found a solution where I set energy source with CEL expression so I get the desired temp in solid body
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Old   March 4, 2018, 09:48
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Quote:
Originally Posted by sortik View Post
I want to set in CFX fixed temperature to one wall and want to simulate heat transfer from this wall to another fluid domain. When I set fixed temp there is no heat transfer to the air. Is it ok to set also boundary for the same wall in air domain as fixed temperature? Or is there any other way?
Maybe you just forgot to change heat transfer option from Isothermal to Heat Energy in domain options?
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Old   March 4, 2018, 16:53
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You cannot define fixed temperature on an interface. Because then it is not an interface, as you have defined the temperature instead. So in this case you need to define a wall on both the fluid and solid domain and remove the interface. Make them both fixed temperature walls - the default is adiabatic walls and I suspect this is what you are seeing.
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Old   March 4, 2018, 17:57
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Originally Posted by ghorrocks View Post
You cannot define fixed temperature on an interface. Because then it is not an interface, as you have defined the temperature instead. So in this case you need to define a wall on both the fluid and solid domain and remove the interface. Make them both fixed temperature walls - the default is adiabatic walls and I suspect this is what you are seeing.
Yes I know that. I created fixed temp boundary for wall in one domain. I saw that fluid solid interface was suddenly gone and whhen you dont have interface you cant have heat transfer. I thought that it will natively compute heat transfer but no. I did it as you mentioned but still dont get it why it has to be like this.

Anyway thank you for your help
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Old   March 4, 2018, 18:00
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Originally Posted by Antanas View Post
Maybe you just forgot to change heat transfer option from Isothermal to Heat Energy in domain options?
Nope everything was ok. I just thought that it works somehow different. You cant set fixed temp boundary for one face and have automatic heat transfer from solid to fluid because there is no interface after you had created boundary.
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Old   March 5, 2018, 02:26
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I think that your problem is ""and whhen you dont have interface you cant have heat transfer""

You dont even need a solid in this case if you know that the wall temperature is at some fixed temperature,just use the fluid domain with that wall set to fixed temperature there is no inteface involved in your simulation
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Old   March 5, 2018, 04:17
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That is correct. If the interface between the solid and fluid domain has a known temperature, then there is no need for a multiple domain simulation as you can run separate solid and fluid simulations. That is much easier and quicker than a combined simulation anyway.
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Old   March 5, 2018, 16:53
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Originally Posted by ghorrocks View Post
That is correct. If the interface between the solid and fluid domain has a known temperature, then there is no need for a multiple domain simulation as you can run separate solid and fluid simulations. That is much easier and quicker than a combined simulation anyway.
I have a heated bed in enclosure with air. The bed is connected to another solid and I was also interested in heat transfer to that solid. Now i completely understand how it works so thanks for the help. I appreciate it
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