How can I calculate correct temperature?

[Fmasa]

Dear all,

First of all, I am pleased that I have known the wonderful elmer FEM software.
I have a trouble in calculation using HeatSolver and StatCurrentSolver.
Now I am trying to calculate temperature increase of a metal wire by Joule heating.
The followings are conditions:
・ The wire was platinum (the electric conductivity = 9.523e6) and a rectangular solid with dimension of 1 x 1 x 20 um^3
・ The added voltage was 0.0005 V
・ The Heat transfer coefficient from the surface to ambient air was 3 W/m^2K.
・ The initial temperature and external temperature was 0 K
・ I used ElmerGUI of Rev5884-win32-binary on Win7 Professional.

The total Joule heating power should be 1.19e-7 J and the elmer correctly calculated, which was checked using SaveScalars.
Energy of the heat transfer to ambient air at steady state should become the same with the total Joule heat, which would results that temperature is 496 K.
However, my calculation with the elmer gave me the temperature of 1.06e7 K (It's too high!).

Could someone tell me why I obtained such the high temperature and what should I do for fixing?


Best regards,
Masa

Code: Select all

Header
  CHECK KEYWORDS Warn
  Mesh DB "." "."
  Include Path ""
  Results Directory ""
End

Simulation
  Max Output Level = 4
  Coordinate System = Cartesian
  Coordinate Mapping(3) = 1 2 3
  Simulation Type = Steady state
  Steady State Max Iterations = 20
  Output Intervals = 1
  Timestepping Method = BDF
  BDF Order = 1
  Solver Input File = case.sif
  Post File = case.ep
Coordinate Scaling = 1.0e-3
End

Constants
  Gravity(4) = 0 -1 0 9.82
  Stefan Boltzmann = 5.67e-08
  Permittivity of Vacuum = 8.8542e-12
  Boltzmann Constant = 1.3807e-23
  Unit Charge = 1.602e-19
End

Body 1
  Target Bodies(1) = 1
  Name = "Body 1"
  Equation = 1
  Material = 1
  Body Force = 1
  Initial condition = 1
End

Solver 2
  Equation = SaveScalars
  Filename = "Flux.dat"
  Coefficient 1 = Electric Conductivity
  Procedure = "SaveData" "SaveScalars"
  Operator 1 = diffusive flux
  Variable 1 = Potential
End

Solver 1
  Equation = Static Current Conduction
  Calculate Joule Heating = True
  Calculate Volume Current = True
  Procedure = "StatCurrentSolve" "StatCurrentSolver"
  Variable = -dofs 1 Potential
  Exec Solver = Always
  Stabilize = True
  Bubbles = False
  Lumped Mass Matrix = False
  Optimize Bandwidth = True
  Steady State Convergence Tolerance = 1.0e-6
  Nonlinear System Convergence Tolerance = 1.0e-6
  Nonlinear System Max Iterations = 1
  Nonlinear System Newton After Iterations = 3
  Nonlinear System Newton After Tolerance = 1.0e-3
  Nonlinear System Relaxation Factor = 1
  Linear System Solver = Iterative
  Linear System Iterative Method = CG
  Linear System Max Iterations = 300
  Linear System Convergence Tolerance = 1.0e-8
  Linear System Preconditioning = ILU0
  Linear System ILUT Tolerance = 1.0e-3
  Linear System Abort Not Converged = True
  Linear System Residual Output = 1
  Linear System Precondition Recompute = 1
End

Solver 3
  Equation = Heat Equation
  Variable = -dofs 1 Temperature
  Procedure = "HeatSolve" "HeatSolver"
  Exec Solver = Always
  Stabilize = True
  Bubbles = False
  Lumped Mass Matrix = False
  Optimize Bandwidth = True
  Steady State Convergence Tolerance = 1.0e-7
  Nonlinear System Convergence Tolerance = 1.0e-8
  Nonlinear System Max Iterations = 20
  Nonlinear System Newton After Iterations = 3
  Nonlinear System Newton After Tolerance = 1.0e-3
  Nonlinear System Relaxation Factor = 1
  Linear System Solver = Iterative
  Linear System Iterative Method = BiCGStabl
  Linear System Max Iterations = 300
  Linear System Convergence Tolerance = 1.0e-9
  Linear System Preconditioning = ILU1
  Linear System ILUT Tolerance = 1.0e-3
  Linear System Abort Not Converged = True
  Linear System Residual Output = 1
  Linear System Precondition Recompute = 1
End

Equation 1
  Name = "Equation 1"
  Active Solvers(3) = 2 1 3
End

Material 1
  Name = "Platinum (generic)"
  Heat expansion Coefficient = 8.8e-6
  Electric Conductivity = 9.523e6
  Heat Conductivity = 71.6
  Sound speed = 2800.0
  Heat Capacity = 133.0
  Mesh Poisson ratio = 0.38
  Density = 21450.0
  Poisson ratio = 0.38
  Youngs modulus = 144.79e9
End

Body Force 1
  Name = "BodyForce 1"
  Heat Source = Equals Joule Heating
  Joule Heat = True
End

Initial Condition 1
  Name = "InitialCondition 1"
  Temperature = 0.0
End

Boundary Condition 1
  Target Boundaries(1) = 1
  Name = "Heat flux from surface"
  External Temperature = 0.0
  Heat Transfer Coefficient = 3.0
End

Boundary Condition 2
  Target Boundaries(1) = 2
  Name = "BoundaryCondition 1"
  Potential = 0.0
End

Boundary Condition 3
  Target Boundaries(1) = 3
  Name = "Heat flux from surface"
  External Temperature = 0.0
  Heat Transfer Coefficient = 3.0
End

Boundary Condition 4
  Target Boundaries(1) = 4
  Name = "BoundaryCondition 2"
  Potential = 0.0005
  Save Scalars = True
End

Boundary Condition 5
  Target Boundaries(1) = 5
  Name = "Heat flux from surface"
  External Temperature = 0.0
  Heat Transfer Coefficient = 3.0
End

Boundary Condition 6
  Target Boundaries(1) = 6
  Name = "Heat flux from surface"
  External Temperature = 0.0
  Heat Transfer Coefficient = 3.0
End

[raback]

Hi

Try to remove the "Heat Source = Equals Joule Heating" part. I think the "Joule Heat = Logical True" should take care of the heating optimally.

-Peter

[Fmasa]

Hello Peter,

Thanks for your quick reply.
You could solve my trouble. I have obtained perfectly correct temperature.


Best regards,
Masa