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Old   January 31, 2010, 08:33
Default Heated tube
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Panos
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Hello fluent users

I simulate the air flow inside a heated cylinder. The geometry is quite simple. The air enters the cylinder by 6 little holes and in environment temperature (300K). The walls temperature is 1273 K (fixed temperature).
i have determined the air density, Cp(specific heat), Thermal conductivity and dyn viscosity by polynomial equations because the air temperature is
expected to rise a lot. Gravity is enabled too. I used the k-e model for energy. I iterated all the equations at once. After 700 iterations suceed convergency and it was obvious that no more changer were done on the residuals. I monitored the pressure outlet static temperature (mass weighted average) and i see that the temperature hadnt reached a stable number.. i reduced the absolute critiria of all the residuals to 1e-05 and i continue iterrating and finally after 1500 iterations the temperature holds a stable price as you can see on the diagrams (ignore the scaled residuals price).
I wanna ask which are the best steps to solve this problem. For example , it would be better for me to solve the flow without energy at first and after this enters the energy? or iterrate at first without gravity?
Can anybody tells me how can i calculate the average air temperature at the outlet please?
Thanks a lot



Adding...
Take a look at the 3rd and 4th diagramms. Eventhough the solution is converged, the temperature keep rising.. I reduced the absolute criteria for all residuals to 1e-05 and keep iterating, hoping that the temperature will stop rising..
Any idea about the number of iterrations that the problem should need to be solved????
Thanks a lot again!
Attached Images
File Type: jpg 1000C30Louttemp.jpg (59.8 KB, 5 views)
File Type: jpg 1000C30Lresiduals.jpg (28.2 KB, 3 views)
File Type: jpg 1000C30L_b_scaled.jpg (72.0 KB, 4 views)
File Type: jpg 1000C30L_b_temp.rising.jpg (63.2 KB, 4 views)

Last edited by panos_metal; January 31, 2010 at 09:59.
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