CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > ANSYS > CFX

Heat transfer problem

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   May 5, 2010, 03:18
Default Heat transfer problem
  #1
New Member
 
Join Date: Mar 2009
Posts: 24
Rep Power: 16
seojaho is on a distinguished road
Hello,

I have a model with three domains (two solid domains, one fluid domain).
One solid domain is for hot plastic melt. (Actually, this domain should be a fluid domain but hot plastic melt does not move and is just contained into this domain. So set this domain as a solid domain for the hot melt)
The other solid domain is for steel into which the heat from the hot plastic melt is transferred.
The remaining fluid domain is for water as a coolant. So the water cools down the steel domain.
When I finished the simulation, it seems that the heat transfer is not conducted from the melt to the steel because the temp. of the steel is increased just little.
Also, the heat transfer from the steel to water is not successful since the temp. difference between inlet and outlet of water is quite small.

(Addtionally, the simulation type is 'transient' and the heat transfer coefficient of ambient air for natural conection of the steel domain is set to 40 W/m2 K.
The initially given hot melt is cooled down by water's cooling without any additional melt during the simulation time. So, I set the initial temp. (204C) of the provided plastic melt an initial condition for the melt domain. )

Please let me know how to solve this unsuccessful heat transfer problem on solid-solid interface and solid-fluid interface.
Thank you.

Last edited by seojaho; May 5, 2010 at 03:33.
seojaho is offline   Reply With Quote

Old   May 5, 2010, 05:06
Default
  #2
Senior Member
 
Matthias Voß
Join Date: Mar 2009
Location: Berlin, Germany
Posts: 449
Rep Power: 20
mvoss is on a distinguished road
hi,

what about convergence? what about the imbalances?

neewbie
mvoss is offline   Reply With Quote

Old   May 5, 2010, 16:10
Default
  #3
New Member
 
Join Date: Mar 2009
Posts: 24
Rep Power: 16
seojaho is on a distinguished road
For convergence control and convergence criteria, I gave 100 as max.coeff.loops and RMS (as residual type), respectively.

Convergence results:
--------------------------------------------------------------------
| Equation | Rate | RMS Res | Max Res | Linear Solution |
+----------------------+------+---------+---------+------------------+
| U-Mom | 0.89 | 3.2E-06 | 8.2E-05 | 3.5E-02 OK|
| V-Mom | 0.81 | 7.1E-06 | 3.0E-04 | 3.1E-02 OK|
| W-Mom | 0.81 | 3.0E-06 | 6.0E-05 | 4.2E-02 OK|
| P-Mass | 0.89 | 4.4E-07 | 1.8E-05 | 8.7 3.3E-02 OK|
+----------------------+------+---------+---------+------------------+
| H-Energy | 0.96 | 5.9E-05 | 1.6E-03 | 4.7E-02 OK|
| T-Energy | 0.95 | 1.1E-04 | 1.9E-03 | 5.3 4.7E-02 OK|
+----------------------+------+---------+---------+------------------+
| K-TurbKE | 0.80 | 3.8E-06 | 1.8E-04 | 5.6 1.7E-02 OK|
| E-Diss.K | 0.82 | 5.1E-06 | 1.4E-04 | 9.6 4.1E-03 OK|
+----------------------+------+---------+---------+------------------

The average of each energy imblance is:

water domain: -1.6e-5(H-energy imbalance)
hot melt domain: 0.001 (T-energy imblance)
steel domain: 0.047 (T-energy imblance)

Thank you so much.
seojaho is offline   Reply With Quote

Old   May 5, 2010, 20:00
Default
  #4
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,655
Rep Power: 143
ghorrocks is just really niceghorrocks is just really niceghorrocks is just really niceghorrocks is just really nice
Your steel imbalance is large (5%). You need to further convergence to get the steel imbalance down, aim for better than 1% but you might need tighter than that.
ghorrocks is offline   Reply With Quote

Old   May 6, 2010, 00:45
Default
  #5
New Member
 
Join Date: Mar 2009
Posts: 24
Rep Power: 16
seojaho is on a distinguished road
Dear Glenn,

Thank you for kind help everytime.
From http://www.cfd-online.com/Forums/cfx...exchanger.html, you suggested useful tips to solve this kind of problem.

In my case, the simulation is transient. So I cannot control solid domain's timescale which is only valid in steady state simulation. (So, 1) tip is not unavailable). Also I applied GGI interfaces ( 2) tip) but it cannot contribute in my case. For 3) which is convergence parameters, another parameters except the H, T-energy imbalance parameters above are required?
For 4) tip, I gave 100 as max.coeff.loops for convergence control.

So, I wonder how I can further convergence to decrease the steel imbanace...

Thank you so much and have a great day, Glenn.

Jaho
seojaho is offline   Reply With Quote

Old   May 6, 2010, 00:57
Default
  #6
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,655
Rep Power: 143
ghorrocks is just really niceghorrocks is just really niceghorrocks is just really niceghorrocks is just really nice
The most important thing in this case is to set a convergence criteria of 0.01 on the imbalances (although you may need tighter - that's up to you to determine) AND the normal residual criteria. You will need to give the solver enough coefficient loops per time step to achieve that convergence tolerance.
ghorrocks is offline   Reply With Quote

Old   May 6, 2010, 01:32
Default
  #7
New Member
 
Join Date: Mar 2009
Posts: 24
Rep Power: 16
seojaho is on a distinguished road
Thank you for quick reply and help.
I will try to do that.
Have a great day, Glenn.

Jaho
seojaho is offline   Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Wall heat transfer coefficient (HTC) problem Mohamed khamis CFX 1 January 16, 2010 00:12
How can I increase Heat Transfer at Domain Interf? B.Simon CFX 3 October 28, 2008 19:53
Conjugate heat transfer problem in 3D Tanveer FLUENT 1 June 17, 2008 03:15
Heat Transfer Problem Help JB FLUENT 2 October 18, 2006 19:54
heat transfer problem. vipin CFX 2 July 18, 2006 11:05


All times are GMT -4. The time now is 23:02.