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July 3, 2014, 08:11 |
Heat exchanger - crazy temperature
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#1 |
New Member
Dawid
Join Date: Jun 2014
Posts: 14
Rep Power: 11 |
Hello,
I want to simulate heat exchanger. Model pipe in pipe. I want to air flowing with 40°C in inside pipe and air 900°C i outside pipe. What i get is... weird. I don't know where the problem could be. Those are setting i made: -Model: Energy On, Viscous Laminar -Cell Zone Conditions: Materials inside pipes air, materials of pipes solid aluminium -Boundary Conditions: inlets of hot/cold pipes are set up on massflow inlet, 0.01kg/s and 900°C/40°C temperature oulets are set up to outflow I am learning fluent for 2 months and maybe i am doing something stupid (and simple i hope so). Yours faithfully, Dawid Pogorzelski |
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July 11, 2014, 12:37 |
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#2 |
Member
David
Join Date: Aug 2012
Posts: 48
Rep Power: 13 |
At first, i think it could probably be mesh-related, your mesh seems course. What are the dimensions of your problem? The residuals have reached convergence? You could give us a little sketch. Check also again your BC, it is a good practice.
Regards |
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July 17, 2014, 09:28 |
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#3 |
New Member
Dawid
Join Date: Jun 2014
Posts: 14
Rep Power: 11 |
Hello, thank You for reply. I have changed mesh size. Now elements are much smaller. Unfortunately it didn't change anything. This is 2D problem. I think residuals have reached convergence. What kind of sketch do you mean? Project? I have checked my BC many many times
here is link to my project project It is created in asnys workbench 14. I hope together we will find solution |
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July 18, 2014, 08:18 |
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#4 |
Member
David
Join Date: Aug 2012
Posts: 48
Rep Power: 13 |
I meant a simple drawing with your bounday conditions and how you have set them up in Fluent.
pd: Also post here your residuals and the result of the new mesh |
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August 1, 2014, 08:55 |
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#5 |
New Member
Dawid
Join Date: Jun 2014
Posts: 14
Rep Power: 11 |
ok, i am not sure but i have found reason. It could be velocity inlet sot up i diffrent direction than normal to boundries. So far is good. I hope nothing more will get crazy from now. Thank you for your patience and help
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August 5, 2014, 05:48 |
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#6 |
New Member
Dawid
Join Date: Jun 2014
Posts: 14
Rep Power: 11 |
Hello again,
After little succes in 2D simulation(based on your help) I decided to create 3D simulation. And again i have strange temperatures. Before (it's shame, i know) the problem was boundary conditions (direction of specification method wasn't normal to boundry). Now i have different problem. In "hot entry" i have great 1013K and in "cold" entry i have beatiful 313K. The problem is that i have 4,83e3K in couple points on "out" wall, and somewhere -14K. I did this time everything as in 2D simulation. I hope it's some stupid and easy mistake but i don't know where to look for it. Please help? Here are: -main problem, weird temperatres on surface of inside pipe: -mesh (with highlighted inner pipe) -residuals (first 100 are for laminar viscous model, after is standard k-e) -my boundary conditions |
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August 5, 2014, 10:36 |
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#7 |
Senior Member
Rick
Join Date: Oct 2010
Posts: 1,016
Rep Power: 26 |
Hi, it's clear from the residual image that solution is not converged.
Why don't you setup a structured hexa mesh? It is quite simple for your geometry. |
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August 6, 2014, 22:13 |
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#8 |
Senior Member
Sangwoo Kim
Join Date: Jul 2014
Location: Seoul, South Korea
Posts: 115
Rep Power: 11 |
Are you going with steady solver?
You should use unsteady solver when handling heat transfer problem
__________________
Best regards |
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