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Old   February 1, 2005, 23:34
Default Heat source problem
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ocy
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Hi all,

How can we model a heat source beneath a chimney using fluent?

I tried to specify the edge as a wall in the boundary condition.

I also tried specifying the edge as a radiator.

Both results doesn't looks good.

Thanks in advance to any replies that come in.
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Old   February 2, 2005, 17:00
Default Re: Heat source problem
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Evan Rosenbaum
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Create a fluid region at the bottom where you want to apply the heat. In the boundary condition panel, under shource terms, you can specify a heat source.
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Old   February 2, 2005, 23:53
Default Re: Heat source problem
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ocy
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Hi Evan,

Thanks for your reply. What do you mean by 'create a fluid region'?

I used gambit to creat a 2D chimney, basically, it's a rectangle with a inlet and a outlet. The continum boundary type inside the rectangle is'fluid'.

Is what i had done correct?

Hope to hear from you soon. Thanks.

Regards
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Old   February 3, 2005, 03:25
Default Re: Heat source problem
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ocy
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Hi Evan,

I tried using the source term.

However, I am getting opposite results. The temp at my outlet is at its maximum while the inlet is minimum.

By the way, I used the fluid zone which is the entire interior of my chimney to specify the source term.

Am I correct in doing that?

If not, how should i go about doing it?

Thanks for your help.
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Old   February 3, 2005, 13:59
Default Re: Heat source problem
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Evan Rosenbaum
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Your need to make two rectangles. Say you have a 10 m chimney with a fire 1 m high in the bottom, and a width of 0.1 m. You make one area from z = 0 m to z = 1 m and a second area from z = 1 m to z = 10 m. The two must share a line at the 1 m height. Mesh the two areas. Now FLUENT will recognize two separate fluid regions. You can specify the heat in the lower region.
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Old   February 7, 2005, 04:52
Default Re: Heat source problem
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ocy
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Thanks Evan.

I managed to get the thing running with your help. However, it seems like i can't get my solution to converge. Not even after 5000 iteration.

For solver: coupled,implicit,steady, 2D, cell-based gradient option.

Operating condition: gravity= -9.81 in x dirn,

Any suggestions in how i can get it to converge?

Thanks
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Old   February 7, 2005, 13:10
Default Re: Heat source problem
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Evan Rosenbaum
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Buoyancy flows are not always easy to converge. First, look at your mesh. Mesh density can have a big influence. If continuity is oscillating, you may need more cells. Second, look at your under-relaxations. Use 0.98 for energy and 0.8 for the body force and density. Third, reconsider the definition of converged. The default parameters in FLUENT are pretty good for most cases, but are as arbitrary as any other criteria you might choose to apply.
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Old   February 17, 2005, 03:08
Default Re: Heat source problem
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ocy
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Hi Evan,

I re-meshed my model, now i can't seems to heat up my air flow. pls help me
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