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Old   March 4, 2016, 07:35
Exclamation Conjugate Heat Transfer Problem
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Ramjan
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Hello All
I am working on IC Engine Fin problem with Fluent and got stuck so solving very simple 2D problem of Rod conducting heat from one end to ambient air around.

Here I have few questions for experts out there

1. At steady state 0 m/s velocity, I received the block temperature (150 deg) all over the body, even the fluid around.
to get more correct results i have switched on gravity with 9.81 m/s^2,
even worked on Air density to Boussinesq with thermal expansion coeff or even density to incompressible ideal gas (according to few lit.)
But no results!!

2. URF are affecting too much with convergence and results and if initialize with lower values (by mistake) solution look very different, please put a light on its affect and usage

We can discuss further if anyone turn up

thanks in advance

Ramjan Pathan
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Old   March 4, 2016, 10:48
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On your first question: why would the temperature not be 150 deg? Which physical mechanism would make the temperature of the fluid in steady state lower, and did you add this mechanism into your simulation?
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Old   March 5, 2016, 06:22
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Ramjan
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Thank you for your reply
I just repeat the question for clarity: According to you the temp across entire body should be 150 is on Boundary is at 150!

For more clarity i have schematic diagram attached here,
Please check all the BCs. Rod left wall has been fixed with 150 deg temp and others are left with heat flux = 0.
As of now no fluid flow, but natural convection is happening because of gravity at y = -9.81 m/s^2

Results: (Static Temp Contours)
Temperature of entire solid body is 150 deg because of conduction and fluid around has 150 deg temp.

But if you refer the fig 3 (Graphical interpretation from Text Book), you can see there should be reduction in temp along the length. tip temp should be lesser than To but grater than Ta for finite length.

and if one can do the same analysis with thermocouples attached to rod temp should be lesser along the length without any flow.

Regards
Attached Images
File Type: jpg BCs.jpg (126.2 KB, 13 views)
File Type: jpg Results.jpg (69.1 KB, 12 views)
File Type: jpg Graph2.jpg (124.1 KB, 10 views)
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Old   March 5, 2016, 09:08
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Christoph Ferk
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Hi Ramjan,

So you expect 150 at the B.C. "Rod left" and then slightly decrease along the length of the fin? Are my thoughts right?

You could also check it in a XY Plot to be sure that there is no decrease in temperature.
What else I could suggest is to calculate in double precision as I think the difference in the thermal conductivities of the fin and the sorrounding air is quite big.

Regards
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Old   March 6, 2016, 05:04
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"According to you the temp across entire body should be 150 is on Boundary is at 150! "

No, don't put words in my mouth that I did not say.

I asked you: "Which physical mechanism would make the temperature of the fluid in steady state lower, and did you add this mechanism into your simulation?"
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