Heat Transfer on Electrical Heat Transfer on Electrical Components by RadiationComponents by Radiation
R. Haller
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
Motivation and Introduction
Physical basic relations
Determination of Radiant Power
Fields of Application
Conclusions
TopicsTopics
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
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.
conduction
convection
radiation
Heat transfer (heating, cooling) is possible by
IntroductionIntroduction
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
design- tasks for electrical components design- tasks for electrical components (indoor)(indoor)
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
Influence of heat power on outdoor components
caused by sun and sky radiation
design- tasks for electrical componentsdesign- tasks for electrical components(outdoor)(outdoor)
sky
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
Motivation and Introduction
Physical basic relations
Determination of Radiant Power
Fields of Application
Conclusions
TopicsTopics
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
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.
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.
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.
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.
intensity of radiation
infrared range
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
intensity of thermal radiation
[Wien]
[Planck]
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
Physical basic relations
[Stefan- Boltzmann´s law]
emissivityarea of radiation
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
thermal radiation balance
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
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.
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.
radiation characteristic for planes
[Lambert´s law]
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
Motivation and Introduction
Physical basic relations
Determination of Radiant Power
Fields of Application
Conclusions
TopicsTopics
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
determination of emissivity ε
ε ≠ f (T)
ε = f (surface material, ..)
determination of surfaces O
determination of power P and/ or temperature T
Determination of Radiant Parameters
exact calculation
numerical calculation (thermal- grid, … .)
measurement (thermografy, ..)
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
exact calculation
= geometrical faktor
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
radiation characteristic for two planes
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
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.
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.
emissivity
material Al- busbar, oxidized (indoor) 0,25
Al- busbar, oxidized (outdoor) 0,6 … 0,9
Cu- busbar, oxidized (indoor) 0,25
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.
numerical calculation
[Stefan- Boltzmann]
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
numerical calculation
analogous to the thermodynamic relation
[Newton]
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
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.
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.
heat transfer by convection
KoKoKo OP
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.
simulation by FEM- program (ANSYS)
boundary conditions results
α = αkonv + αrad
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
theory of similarity
free convection:
forced convection:
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
theory of similarity
free convection forced convection
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
theory of similarity f r e i e K o n v e k t i o n
s e n k r e c h t e W a n d
Z e l l e n s e i t en w ä n d e i n n e n u n d a u ß e n
3 PrGr 15,0 Nu 108 102 PrGr 107,1
w a a g e r e c h t e W a n d , W ä r m e a b g a b e n a c h o b e n , W ä r m e a u f n a h me v o n u n t e n
Z e l l e n d a c h I n n e n u n d a u ß e n
3 PrGr 17,0 Nu 98 101,1 PrGr 103,2
w a a g e r e c h t e W a n d , W ä r m e a b g a b e n a c h u n t e n
K a n a l b o d en a u ß e n
3 Pr Gr095,0 Nu 98 102,1 PrGr 103,1
w a a g e r e c h t e Z y l i n d e r
K a b e l u n d R u n d l e i t e r , h o r i z o n t a l v e r l e g t
lw
ROK o
K o K o
1
K ow
N u
l
4 PrGr 54,0 Nu 72 102 PrGr 105
3 PrGr 13,0 Nu 137 10 PrGr 102
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
theory of similarity
e r z w u n g e n e u n d e r z w u n g e n e m i t ü b e r l a g e r t e r f r e i e r K o n v e k t i o n
v e r t i k a l e W a n d V
5,0
66,0
Pr)Gr (91,0 Re*
;Re'16,0 Nu
R e ' 1 0 5
Z y l i n d e r q u e r a n g e s t r ö m t
lw
V
403,0
62,0
Pr) Gr(97,6 Re*
;Re'17,0 Nu
R e ' 1 0 4
E i n f a c h s c h i e n e w a a g e r e c h t , h o c h k a n t
L u f t b e w e -g u n g i m G e r ä t d u r c h L ü f t u n g s -ö f f n u n g e n o d e r L ü f t e r
lw
V
ROK o
K o K o
1
K ow
N u
l
2*Re²Re Re'
42,0
6,0
Pr)Gr (25,2 Re*
;Re'4,0 Nu
R e ' , 4 2 1 0 4
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
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.
thermal grid method
DQ = Rth * P (steady state)
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.
thermal grid method
Rth = RL + RKo + RS
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
thermal grid method
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
thermal grid method
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
radiation influence on outdoor components
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
influence of sky radiation
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
comparison with convective transferred heat power
I
Tvertical plate with temperature T > T0T0
bus- bar of switching equipments
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
comparison of heat transfer
vertical plate (OS1 = 1m2), T1 = 70 °C, T2 = 30 °C
1 = 0,25/ 0,9; 2 = 0,9; OS1 << OS2
S= 1,92 W/m2K
PS= 76,8W/m2
S= 6,9 W/m2K
PS= 276 W/m2
Ko= 5,83 W/m2K
PKo = 233,2 W/m2
free convection
1T 2TPKo
PS
Ps > Pk !
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
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.
comparison of heat transfer
heat transfer on bus- bar(parameter: Al, 10x100, I= 2000A, eps= 0,25/ 0,9)
0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0,9
-10 -5 0 5 10 15 20 25 30 35 40
surr_temperature [°C]
Pko
nv,
Pra
d /
Pto
tal
Prad --- (ε = 0,25; 0,9)
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
measurement of radiant power
measurement principle
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
measurement of radiant power
working range of IR- measurement systems
transmission ability of measuring distance
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
application in electrical power engineering
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
heating up process of an electronic circuit
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
Motivation and Introduction
Physical basic relations
Determination of Radiant Power
Fields of Application
Conclusions
TopicsTopics
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
evaluation of thermal conditions for technical
devices design, development, quality inspection, …
studying of physical processes
….
fields of application
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
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 !!
radiation heating
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
Gas Insulated Lines (GIL)
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
Overhead line joint
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
Overhead line joint
Hasse
Verlustle istung ²RI
Sonnen- und H im m elsstrahlung P SH
W ärm eleitungswiderstand
konvektiver W ärm eübergangswiderstand
W ärm estrahlungswiderstände
W ärm kapazität
I R V
Verbindung Leiter
V L L L L L L
0
H
I²R V
0°C
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
Overhead line joint
Messwerte mit ku = 1,8
Rechnung mit ku = 2,0
Rechnung mit ku = 1,0
Rechnung mit ku = 1,5
Rechnung mit ku = 1,8
-0,6 -0,4 -0,2 0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6 m 2,0
90
85
°C
80
75
70
60
65
Tem
pe
ratu
r
Abstand x
Verbinder Leiter
Messwerte mit ku = 1,8
Rechnung mit ku = 2,0
Rechnung mit ku = 1,0
Rechnung mit ku = 1,5
Rechnung mit ku = 1,8
-0,6 -0,4 -0,2 0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6 m 2,0
90
85
°C
80
75
70
60
65
Tem
pe
ratu
r
Abstand x
Verbinder Leiter
Messwerte mit ku = 1,8
Rechnung mit ku = 2,0
Rechnung mit ku = 1,0
Rechnung mit ku = 1,5
Rechnung mit ku = 1,8
-0,6 -0,4 -0,2 0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6 m 2,0
90
85
°C
80
75
70
60
65
Tem
pe
ratu
r
Abstand x
Verbinder Leiter
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
Motivation and Introduction
Physical basic relations
Determination of Radiant Power
Fields of Application
Conclusions
TopicsTopics
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
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.
Thank you --dekuji za pozornost
Questions ?
Answers !
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
additional informations
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
additional informations
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
additional informations
RITTAL- bus- bars with different coefficients of emissivity (0,9/ 0,4)
0
200
400
600
800
1000
1200
0 50 100 150 200 250 300 350 400 450
cross section [mm**2]
limit
of
curr
ent
[A]
Department of Electrical Power and Environmental Engineering Prof. Dr.- Ing. habil. Rainer Haller, Dr.sc.techn.
additional informations