Geometry not cooling?

Numerical methods and mathematical models of Elmer
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ScientistRenzo
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Geometry not cooling?

Post by ScientistRenzo »

I applied a heat source for 20 seconds then turned it off with a user defined function. I wanted to see my object cool. It does not cool. Idk why.
https://imgur.com/a/lnCtJh7

I have a 273 external temp and idealized radiation with emmisivity .75 set to all the boundary
https://imgur.com/a/AYleCPd

Even with external temp 200, no change

Thanks :D ;)
kevinarden
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Re: Geometry not cooling?

Post by kevinarden »

If I start with a warm body using an initial condition, no body force, the body cools with time.
nobodyforce.png
(29.91 KiB) Not downloaded yet
If I start with a cool body, it with a body force for a finite time until is is a warm body. Set heat source to 0, no cooling.
bodyforce.png
(16.55 KiB) Not downloaded yet
kevinarden
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Re: Geometry not cooling?

Post by kevinarden »

It appears I did not get it hot enough. If I heat the body well over the external boundaries then it cools.
bodyforce.png
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case.sif
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kevinarden
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Re: Geometry not cooling?

Post by kevinarden »

If i start with a cold body the external boundary heats it.
heatbody.png
(21.29 KiB) Not downloaded yet
If I heat the body some, then turn of the heat source the external boundary continues to heat it.
heat2.png
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If I heat the body close to the boundary temperature, the boundary holds the body nearly constant.
bodyforce1.png
(16.55 KiB) Not downloaded yet
ScientistRenzo
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Re: Geometry not cooling?

Post by ScientistRenzo »

Oh it's cooling. It's just barely cooling -> -.001 K change per second when the ext. temp. is set to 100 K and the object is heated to 274 K. Surprising.

Thanks kevin
raback
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Re: Geometry not cooling?

Post by raback »

Hi

Typically whe this happens the user has forgotton to change the units of length to SI units. Your material parameters are in SI units. What is your system size looking in paraview?

Also, please don't use ".75", rather "0.75". Not everybody reads that correctly, I don't know about Elmer.

-Peter
kevinarden
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Re: Geometry not cooling?

Post by kevinarden »

My block was 0.1 meter x 0.1 meter x 0.30 meter high.
raback
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Re: Geometry not cooling?

Post by raback »

Ok, seems plausible that a block of aluminum would radiate significantly in an hour or so. Maybe you could share the last vtu file from the time series. -Peter
ScientistRenzo
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Re: Geometry not cooling?

Post by ScientistRenzo »

@raback I believe all of my units are SI.

Do you think this sort of result is accurate/realistic to the simulation/model?

Are you suggesting I change something in ParaView? I don't understand.

Thanks :)
kevinarden
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Re: Geometry not cooling?

Post by kevinarden »

I believe he was responding to my post of 0.1 meter x 0.1 meter x 0.3 meter aluminum block.
We do not know the size or material of your block.
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