# extreme temperatures on winding

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 July 25, 2011, 03:47 extreme temperatures on winding #1 Senior Member   Join Date: Jul 2010 Posts: 147 Rep Power: 7 Hello everyone. I am simulating heat transfer in electric power generator and I had to use anisotropic copper to define its winding. But I obtained very strange result of temperature distribution. There are few little areas where the temperature is very low (-150°C) and very high (480°C). Also the convergence of thermal energy is quite normal but after 200 iterations it becomes to diverge. Does anyone know what could be cause of this issue?? Thanks for any suggestions.

 July 25, 2011, 04:58 hi #2 Member   Rahul Vaibhav Join Date: Nov 2009 Location: India Posts: 33 Rep Power: 7 Hi Keeper I think because of diverging solution, you are getting such strange temperature values. Try to improve the mesh quality and reduce the time step for better convergence .

 July 25, 2011, 05:40 #3 Senior Member   Join Date: Jul 2010 Posts: 147 Rep Power: 7 unfortunately I am limited by the mesh size, my model contains 2.5M nodes and this is reasonable maximum which I can calculate with..but I will try to decrease timestep, thank you very much for suggestion...but anyway it is strange that those areas appear just after 200th iteration when solution starts to diverge

 July 25, 2011, 08:13 #4 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 10,923 Rep Power: 85 Convergence is one possibility but another common cause of this problem is the application of heat sources and sinks. If they are not correctly applied you get regions which get far too hot and cold. How have you applied the heat to this simulation?

July 26, 2011, 01:44
#5
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Join Date: Jul 2010
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I defined domains and created subdomains on them where I set up heat sources. Below there is part of CCL.

SUBDOMAIN: WINDING HS
Coord Frame = Coord 0
Location = B5653
SOURCES:
EQUATION SOURCE: energy
Option = Source
Source = 98919 [W m^-3]
END
END
END

Those loses are calculated from electrical loses in winding and recalculated to 1 m^3.
Attached Images
 CFX_019.jpg (93.2 KB, 20 views)

 July 26, 2011, 08:57 #6 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 10,923 Rep Power: 85 Assuming the red and blue regions are your temperature extreme regions then it looks pretty certain something is wrong. Is there a GGI nearby? Is it intersecting properly? What could be causing this? If no external cause is present then it is most likely a divergence problem.

 July 26, 2011, 09:10 #7 Senior Member   Join Date: Jul 2010 Posts: 147 Rep Power: 7 yes there is GGI but it is without any overlaping area..as you can see on the picture the wireframe shows each domain..the end winding is seperated into four domains. I also used anisotropic definition for this domain. Please see below CCL for material definition. It is strange that it appears only in one domain. MATERIAL: CopperStatorOut12 Material Group = CHT Solids, Particle Solids Option = Pure Substance Thermodynamic State = Solid PROPERTIES: Option = General Material EQUATION OF STATE: Density = 8933 [kg m^-3] Molar Mass = 63.55 [kg kmol^-1] Option = Value END SPECIFIC HEAT CAPACITY: Option = Value Specific Heat Capacity = 3.85E+02 [J kg^-1 K^-1] END REFERENCE STATE: Option = Specified Point Reference Specific Enthalpy = 0 [J/kg] Reference Specific Entropy = 0 [J/kg/K] Reference Temperature = 25 [C] END THERMAL CONDUCTIVITY: Option = Orthotropic Cylindrical Components Thermal Conductivity Axial Component = 296 [W m^-1 K^-1] Thermal Conductivity Theta Component = 5 [W m^-1 K^-1] Thermal Conductivity r Component = 4.7 [W m^-1 K^-1] AXIS DEFINITION: Option = Two Points Rotation Axis From = 0 [m],0 [m],-0.265 [m] Rotation Axis To = 0 [m],0 [m],-0.5 [m] END END END END Could the point on the axis affect the results?? I mean is it the same when defining axis like: from (0,0,0) to (0,0,1) and from (0,0,0.25) to (0,0,1)??

 July 26, 2011, 18:49 #8 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 10,923 Rep Power: 85 To me it looks like a mismatched GGI or some other local problem. Does not seem to be the axis location, but you have not given much detail and so cannot be sure.

 July 27, 2011, 03:05 #9 Senior Member   Join Date: Jul 2010 Posts: 147 Rep Power: 7 it is also strange when ruuning simulation with isotropic material then those errors don't appear.. anyway thank you very much for help..what kind of details would you need to know more??

 July 27, 2011, 06:02 #10 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 10,923 Rep Power: 85 If this runs fine isotropic then I suggest it is a convergence problem, not a GGI problem. Try converging tighter.

 July 27, 2011, 06:26 #11 Senior Member   Join Date: Jul 2010 Posts: 147 Rep Power: 7 ok ghorrocks thank you very very much for your help

 July 27, 2011, 15:37 #12 Senior Member   Edmund Singer P.E. Join Date: Aug 2010 Location: Minneapolis, MN Posts: 495 Rep Power: 11 I dont entirely concur. It could have something to do with the large difference in conductivity (axial and non-axial), along with a mesh density mismatch at the GGI interface or a mesh density issue in the respective planes. Few things you should try: 1) Ensure your interface mesh sizes are about equal 2) Keep material othrotropic but put in the same conductivity (probably use the axial conductivity) for all directions and see if the issue still occurs 3) If 2 works fine, try dropping your non-axial conductivity bit by bit, if the problem occurs when the differences in conductivity becomes large, you most likely have a mesh density issue.

 July 27, 2011, 19:10 #13 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 10,923 Rep Power: 85 Good point. Definitely worth trying.

 July 28, 2011, 02:18 #14 Senior Member   Join Date: Jul 2010 Posts: 147 Rep Power: 7 thanks a lot singer I will try to follow your steps

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