1. Heat transfer simulation using COMSOL Multiphysics 4.1
University of Tokyo
Kenshi Okada
July 6, 2011

2. The simulation of temperature change of the test mass
Pendulum_wire_41_3D_refined_dampingmass.mph
in C:/Users/frank/Documents/Okada
We can change the parameters (ex. initial temperature at Heat Transfer>Initial Values, or time length at Study>Step2:Time Dependent>Study Setteings>Times) and see the result when we right click Study and choose Compute.
How I made the file is as follows

3. After start COMSOL, in Model Wizard choose 3D and click Next
Choose Heat Transfer>Heat Transfer in Solids and click Next
Choose Preset Studies>Time Dependent and click Finish

4. Model>Geometry Model>Definitions Model>Materials Global definitions Model>Heat Transfer Model>Mesh Study Results

5. ・ Right click Model>Geometry and choose , for example, Cylinder.
・ When we want to make holes, right click Model>Geometry and choose
Boolean Operations>Deference
・ After we make all domains, right click Model>Geometry and choose Build all

6. Model>Geometry Model>Definitions Model>Materials Global definitions Model>Heat Transfer Model>Mesh Study Results

7. We can make groups of the domains
(for convenience) when we right click Model>Definitions and choose Selection

8. Selection 1 (Aluminum)

9. Selection 2 (Tungsten)

10. Selection 3 (Copper)

11. Selection 4 (Glass)

12. Model>Geometry Model>Definitions Model>Materials Global definitions Model>Heat Transfer Model>Mesh Study Results

13. Right click Materials>Material to make the materials as follows
Functions in
Global Definitions
・ Aluminum
Selection: Selection1
Thermal conductivity Value: Al_thermal_con(T)
Density Value: 2700
Heat capacity at constant pressure Value: Al_heat_capa(T)
・ Tungsten
Selection: Selection2
Thermal conductivity Value: Tungsten_thermal_con(T)
Density Value: 19250
Heat capacity at constant pressure Value: Tungsten_heat_capa(T)
・ Copper
Selection: Selection3
Thermal conductivity Value: Copper_thermal_con(T)
Density Value: 8940
Heat capacity at constant pressure Value: Copper_heat_capa(T)
・ Glass
Selection: Selection4
Thermal conductivity Value: Glass_thermal_con(T)
Density Value: 2600
Heat capacity at constant pressure Value: Glass_heat_capa(T)

14. Model>Geometry Model>Materials Global definitions Model>Heat Transfer Model>Mesh Study Results

15. Interpolation and Extrapolation>Enterpolation:
Right click Global Definitions ,and choose Functions>Interpolation
Input Function name (ex. Al_heat_capa) and data
Interpolation and Extrapolation>Interpolation:
Piecewise cubic
Interpolation and Extrapolation>Enterpolation:
Linear
We can save the data as text file and use them in other simulations
(the files are in C:/Users/frank/Documents/Okada/Functions)

16. ・ Heat capacity of Aluminum
from

17. After clicking Plot on the upper right

18. ・ Thermal conductivity of Aluminum6061

19. After clicking Plot on the upper right

20. ・ Heat capacity of Tungsten
from

21. After clicking Plot on the upper right

22. ・ Thermal conductivity of Tungsten

23. After clicking Plot on the upper right

24. ・ Heat capacity of Copper
from

25. After clicking Plot on the upper right

26. Thermal conductivity of Copper

27. After clicking Plot on the upper right

28. Heat capacity of Glass
from

29. After clicking Plot on the upper right

30. Thermal conductivity of Glass

31. After clicking Plot on the upper right

32. Model>Geometry Model>Definitions Model>Materials Global definitions Model>Heat Transfer Model>Mesh Study Results

33. Heat Transfer in solids, Thermal insulation and Initial Values exist
from the beginning.
Right click Heat Transfer and choose Surface-to-Ambient Radiation.
Choose boundaries for gold surface (I used 0.47 for the value of emissivity).
Choose boundaries for aluminum surface (I used 0.3 for the value of emissivity).
Right click Heat Transfer and choose Temperature.
Select the top of the wire.
Input 4K.
Right click Heat Transfer and choose Heat Flux.
Select a surface of the glass.
Input some value at General inward heat flux
(I used 100μW ×4% divided by the area).

34. Model>Geometry Model>Materials Model>Heat Transfer Model>Mesh Study Results

35. Right click Mesh and click Built all
Model>Mesh>size
Choose Custom on Element size.
(In some cases, we can use Predefined.
But if even Extremely coarse can not be used,
we need to use Custom)
Element Size Parameters I used
Maximum element size: 0.15
Minimum element size:
Right click Mesh and click Built all

36. After built in Mesh

37. Model>Geometry Model>Materials Model>Heat Transfer Model>Mesh Study Results

38. Right click Study, and choose study steps>Time dependent.
In my case I needed to use two steps of Time dependent
(Perhaps because of the sharp gradient of the initial temperature (293.15K and 4K))
Step1: range(0, 0.1, 1)
Step2: range(1,10000, )

39. Model>Geometry Model>Materials Model>Heat Transfer Model>Mesh Study Results

40. Results>3D Plot Group>Surface
We can change the time of the result on Results>3D Plot Group>Data>Time

41. Results>3D Plot Group>Slice

42. How to plot temparature change at a paticular point
・Right click on Results>Data sets and add Cut Point 3D
Cut Point 3D>Point Data
X:0, Y:0, Z:0.0127
Parameters I used:

43. ・Right click Results, and add 1D Plot Group
・Choose Cut point 3D in 1D Plot Group>Settings>Data>Data set
・Right 1D Plot Group, and add Point Graph
・Choose Cut point 3D in 1D Plot Group>Point Graph>Settings>Data>Data set
・Click Plot on the on the upper right in Settings