1. Heat Transfer on Electrical Components by Radiation
R. Haller

2. Topics Motivation and Introduction Physical basic relations
Determination of Radiant Power
Fields of Application
Conclusions
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

3. Motivation Is the radiation in the low temperature range
(< 100 … 150 °C) important for thermal
calculation or not ?
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

4. Introduction Heat transfer (heating, cooling) is possible by
conduction
convection
radiation
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

5. design- tasks for electrical components (indoor)
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

6. design- tasks for electrical components (outdoor)
sky
Influence of heat power on outdoor components
caused by sun and sky radiation
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

7. Topics Motivation and Introduction Physical basic relations
Determination of Radiant Power
Fields of Application
Conclusions
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

8. type of electromagnetic radiation
thermal radiation  0.1 … 400 µm
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

9. Physical basic relations
radiation processes are different from those by
conduction or convection
no transfer medium is necessary
transferred heat power is mainly determined by
the object temperature T and the interactions
between the radiated areas (absorption, emissivity)
what can lead to a difference of temperature T ) and
can´t be described by classical thermodynamics
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

10. generation of thermal radiation (modelling)
thermal radiation will be generated by changes of atomic dipol moment caused by thermal induced oscillations
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

11. classification
Objects with a temperature T > 0 K emit electromagnetic radiation and, therefore, are able to give away energy to other objects
The radiation takes place from the surface of solid and fluid objects and/ or from the volume of gases
area radiator (radiators are described by their radiation area)
volume radiator (physical basic processes)
the heating by radiation will be generated by inner atomic processes into the radiated object (near the surface, absorption)
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

12. intensity of radiation
infrared range
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

13. intensity of thermal radiation
[Wien]
[Planck]
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

14. Physical basic relations
area of radiation
[Stefan- Boltzmann´s law]
emissivity
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

15. thermal radiation balance
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

16. Physical basic relations
The ratio of emission is equivalent to the ratio of absorption
(thermal balance  Kirchhoff´s law
Ratio of emission for real radiators:
radiation of real object with T1
radiation of „black radiator“ with T1
ε =
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

17. Physical basic relations
classification of radiators:
black: all radiations will be absorbed (ά = ε = 1)
white: all radiations will be reflected (ρ = 1)
gray: all radiations will be absorbed/ emitted in the
same ratio about all wave lengthes (ε < 1)
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

18. radiation characteristic for planes
[Lambert´s law]
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

19. Topics Motivation and Introduction Physical basic relations
Determination of Radiant Power
Fields of Application
Conclusions
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

20. Determination of Radiant Parameters
 determination of emissivity ε
ε ≠ f (T)
ε = f (surface material, ..)
 determination of surfaces O
determination of power P and/ or temperature T
exact calculation
numerical calculation (thermal- grid, … .)
measurement (thermografy, ..)
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

21. exact calculation = geometrical faktor
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

22. radiation characteristic for two planes
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

23. emitted radiation between two planes with significant area difference
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

24. emitted radiation between two planes with significant area difference
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

25. Cu- busbar, oxidized (indoor) Cu- busbar, oxidized (outdoor)
emissivity
material 
Al- busbar, oxidized (indoor)
0,25
Al- busbar, oxidized (outdoor)
0,6 … 0,9
Cu- busbar, oxidized (indoor)
Cu- busbar, oxidized (outdoor)
0,7 … 0,95
colours, varnishes
0,8 … 0,9
mineralic materials
0,7 … 0,85
 usually determined by measurement
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

26. numerical calculation
[Stefan- Boltzmann]
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

27. numerical calculation analogous to the thermodynamic relation [Newton]
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

28. determination of heat power (radiation + convection)
[Newton]
with  = k + S1,2
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

29. determination of heat power
 heat power parts must be determined separately
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

30. heat transfer by convection
exact calculation of Navier- Stokes- Equations
numerical calculation (FEM, CFD, …)
theory of similarity
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

31. simulation by FEM- program (ANSYS)
α = αkonv + αrad
boundary conditions
results
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

32. theory of similarity free convection: forced convection:
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

33. theory of similarity free convection forced convection
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

34. theory of similarity
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

35. theory of similarity
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

36. thermal grid method Gth· θ + Cth· (dθ/ dt) = P with θ  temperature
P  heat power
Gth , Cth  thermal admittance, capacity
ordinary differential equation system
coefficients are dependent from variable
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

37. thermal grid method DQ = Rth * P (steady state) procedure:
with DQ  difference of temperatures
P  heat power
Rth  thermal resistances
procedure:
 separation of interesting areas/ volumes into n- parts
 determination of heat power sources
 calculation of thermal resistances
 appropriate network calculation method
(nonlinear, iterative calculations)
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

38. thermal grid method Rth = RL + RKo + RS
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

39. thermal grid method
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

40. thermal grid method
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

41. radiation influence on outdoor components
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

42. influence of sky radiation
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

43. comparison with convective transferred heat power
vertical plate with temperature T > T0 T T0 I
bus- bar of switching equipments
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

44. comparison of heat transfer
PKo PS
vertical plate (OS1 = 1m2), T1 = 70 °C, T2 = 30 °C
1 = 0,25/ 0,9; 2 = 0,9;
OS1 << OS2
free convection
S= 1,92 W/m2K
S= 6,9 W/m2K
Ko= 5,83 W/m2K
PKo = 233,2 W/m2
PS= 76,8W/m2
PS= 276 W/m2
 Ps > Pk !
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

45. comparison of heat transfer
Parameter: I = 2000 A, bus- bar (10 x 100) mm2, Al =
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

46. comparison of heat transfer
Prad --- (ε = 0,25; 0,9)
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

47. measurement of radiant power measurement principle
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

48. measurement of radiant power
transmission ability of measuring distance
working range of IR- measurement systems
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

49. application in electrical power engineering
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

50. heating up process of an electronic circuit
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

51. Topics Motivation and Introduction Physical basic relations
Determination of Radiant Power
Fields of Application
Conclusions
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

52. fields of application evaluation of thermal conditions for technical
devices  design, development, quality inspection, …
studying of physical processes ….
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

53. radiation heating technical data: θ ~ 90 °C, 200 … 700 W
efficiency of radiation heating is mainly determined by ability of absorption/ emissivity of the located objects/ areas but not from the room air !!
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

54. Gas Insulated Lines (GIL)
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

55. Overhead line joint
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

56. Overhead line joint
Hasse
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

57. Overhead line joint
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

58. Topics Motivation and Introduction Physical basic relations
Determination of Radiant Power
Fields of Application
Conclusions
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

59. thermal radiation processes are different from those as
convection or conduction
heat transfer should be determined by convection and
radiation processes even in the low temperature range
for determination of heat transfer the method of thermal
grid can be used as an effective engineering tool
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

60. Thank you -- dekuji za pozornost
Questions ?
 Answers !
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

61. additional informations
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

62. additional informations
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

63. additional informations
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.

64. additional informations
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.