# transient conduction in a wall

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September 4, 2013, 03:05
transient conduction in a wall
#1
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this the problem. steam inlet from below the drum with temp 380 C, mass flow 0,4 kg/s with int condition 60 C (for wall and fluid), steam injected for 460 min. air inside the drum with temp. 60 C. here is the step what i've done.

gambit :
1.import model 2D
2. create face 1 for solid and create face 2 for liquid
3. mesh face for face 1 and face 2 together
4. create countinuum type face 1 solid and face 2 liquid selected
5. creat BC inlet at buttom line and symetry on left edge
6. export mesh

fluent 6 :
2. scale
2. define model solver - unsteady
3. define mdl multiphase- eularian
4. define mdl energy - check
5. define mdl visc - k-epsilon
6. define material - vapor water (solid with rho=7850, cp =450, K = 40)
7. define phase- phase 1 (air) phase 2 (vapor)
8. define OC - gravity (-9.81)
9. define BC- inlet (phase 2, 0,4kg/s, temp 380 C) (phase 1, 0 kg/s, temp 60 C) there is wall 1 and wall 01:shadows appear at edge between solid and luqiud, BC without outlet

10. solve-control solution-ok
11. solve initialize- inlet
13. solve initialize - patch (phase 2, liquid , value=0) (mixture, solid, value 60 C) this i want to make theres no vapor inside the drum and int temp. of wall is 60 C
14. solve monitor residual - plot
15. iterate - time step size (1) number of TS (76000 s) max iteration/TS (2)
16. iterate

there're all the steps friends, but the result temperature of the wall is not as i expected, its about 250 C and thats should be around 350 C. Please tell me what i missed. is that because i used fluent 6 ? i really need your help

thank you very much
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Last edited by chabib; September 4, 2013 at 05:18.

 September 4, 2013, 04:22 #2 Member     Join Date: Jul 2011 Posts: 74 Blog Entries: 1 Rep Power: 12 do you have specific question or you want us to solve your problem

 September 4, 2013, 05:10 #3 New Member   chabib muhammad Join Date: Aug 2013 Posts: 2 Rep Power: 0 dear centurion2011 i just want to share my problem why i have different wall temperature from numerical result with measured result. i hope some one can explain to me. i write the steps because i thing there something wrong in my steps or something else. i am still learning using Fluent. sorry if my question too general or say something wrong in this forum regards

 September 4, 2013, 05:20 #4 Member     Join Date: Jul 2011 Posts: 74 Blog Entries: 1 Rep Power: 12 maybe you should start with steady solution and then progress toward unsteady case. For more info on unsteady problems, go to following link Hope this will help you a bit __________________ I'M NOT A GYNECOLOGIST BUT I'LL TAKE A LOOK.

September 4, 2013, 07:49
#5
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duri
Join Date: May 2010
Posts: 160
Rep Power: 9
Quote:
 Originally Posted by chabib 10. solve-control solution-ok 11. solve initialize- inlet 12. adapt region-insert number of x/y max/min - adapt - mark
Since you used default solver settings. Check whether it is second order or higher. And don't use mesh adaption near boundary (if any), better to create a fine mesh than mesh adaption. k-epsilon turbulence model uses wall function which is not suitable for heat transfer applications try sst model.

September 5, 2013, 05:55
#6
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Daniele
Join Date: Oct 2010
Location: Italy
Posts: 1,001
Rep Power: 19
Quote:
 Originally Posted by chabib 15. iterate - time step size (1) number of TS (76000 s) max iteration/TS (2)
Are you sure you are getting convergence with only 2 iterations per time step?

Daniele

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