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PLATO - TOU Thermal analyses. Summary of previous thermal analyses performed in 2010-2011 S.Basso – F. Borsa (I.N.A.F. – Osservatorio Astronomico di Brera ) . FE Model description : elements description. 3 element types are used, SOLID70 and LINK33 ( Ansys software). 3 Bipods - PowerPoint PPT Presentation
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PLATO - TOUThermal analyses
Summary of previous thermal analyses performed in 2010-2011
S.Basso – F. Borsa (I.N.A.F. – Osservatorio Astronomico di
Brera)
Catania, 11/Jun./2014 S.Basso - INAF OABrera
FE Model description:elements description
3 Bipods(link element)
Catania, 11/Jun./2014 S.Basso - INAF OABrera
• 12 points• metallic ring• 3 points
3 element types are used, SOLID70 and LINK33 (Ansys software)
~10000 nodes~8000 elements
PLATO - TOUBaffle height
Configuration 1&4 Configuration 2&3
Conf.1&4:Minimum possible height
Catania, 11/Jun./2014 S.Basso - INAF OABrera
Fast 1&4 2&3Baffle height [mm]
100 117 92
The height of the baffle for configuration 2&3 is set to obtain the same avarage temperature for the two configuration
FE Model results:Conf. 1&4
Heaters OFF, insulating links Baffle/tube (0.0296 W/K) , no IR coating on the Window and baffle emiss.=0.94
Win
dow
L1 L2 L3 L4 L5 L6 baffl
e
tube
TRP
-140
-130
-120
-110
-100
-90
-80
Temperature
Al Ti
Win
dow
L1 L2 L3 L4 L5 L6 baffl
e
tube
0
5
10
15
20
25
30
35
40
45
50
Thermal gradient inside each com-ponent
Al Ti
Very close to the -90°C
(goal)
Catania, 11/Jun./2014 S.Basso - INAF OABrera
Win
dow
L1 L2 L3 L4 L5 L6 baffl
e
tube
-140
-130
-120
-110
-100
-90
-80
Temperature
Al baffle and coupling=0.0290 Al baffle and coupling=0.0148Al baffle and coupling=0.0074 Ti baffle and coupling=0.0293
FE Model results:Conf. 2&3Heaters OFF, no IR coating on the Window and baffle emiss.=0.94
Very close to the -90°C
(goal)
Win
dow L1 L2 L3 L4 L5 L6
baffl
e
tube
0
5
10
15
20
25
30Thermal gradient inside each com-
ponent
Al baffle and coupling=0.0290 Al baffle and coupling=0.0148
Al baffle and coupling=0.0074 Ti baffle and coupling=0.0293
Catania, 11/Jun./2014 S.Basso - INAF OABrera
Win
dow
L1 L2 L3 L4 L5 L6 baffl
e
tube
TRP
-140
-130
-120
-110
-100
-90
-80
Temperature
Baffle AL Baffle Ti
FE Model results:Fast TOU
Heaters OFF, no IR coating on the Window and baffle emiss.=0.94
The Titanium baffle is not necessary to
reach the goal (-90°C)
Win
dow
L1 L2 L3 L4 L5 L6 baffl
e
tube
0
5
10
15
20
25
30
35
40
Thermal gradient inside each com-ponent
Baffle AL Baffle Ti
Catania, 11/Jun./2014 S.Basso - INAF OABrera
FE Model results:Baffle-tube connection
Baffle-tube connection
Catania, 11/Jun./2014 S.Basso - INAF OABrera
Washers
Conductance baffle/tube
N° joining points
Joining material
Flexure size [mm] (length/height/minimum thickness)
Washer - Size [mm] (ext.diameter/int.diameter/height)
0.0074 4 Ti 23/7/0.7 Yes (ceramic) – 10/6/100.0148 6 Ti 23/10/0.7 Yes (ceramic) – 10/6/8 0.0296 12 Al 23/10/0.7 Yes (ceramic) – 8/4/120.0296 6 Ti 23/10/0.7 No2.9558 12 Al 18/10/0.7 (current
mechanical design)No
FE Model results:Last change
Catania, 11/Jun./2014 S.Basso - INAF OABrera
Heat from CCD [W] (cold case)
0.94 (normal TOUs) 1.73 (FAST)
Heat from CCD [W] (hot case)
1.46 (normal TOUs) 2.63 (FAST)
OB Temperature [°C] -63Bipod conductance
[W/K] 3*0.012=0.036Lenses emissivity 0.9Outer emissivity (tube, baffle and
CCD) 0.005Inner emissivity (tube and CCD) 0.94 The intermediate value of 0.0071 W/K per bipod corresponds to
the value computed with the mechanical design proposed in PLATO.LAM.SYS.SPE.1065 - Issue 2
FE Model results:termo-elastic analysesEvaluation of thermo-elastic deformations of telescopes
from 20°C to low temperature
ModelThermal analysis
Structural analysis
Catania, 11/Jun./2014 S.Basso - INAF OABrera
FE Model results:termo-elastic analyses
Catania, 11/Jun./2014 S.Basso - INAF OABrera
Vertical displacement
L1
L6
temperature~ -106°C
~ -102°C
Compression of lenses
Compression of tube & baffle
FE Model results:Thermo-elastic for conf. 1&4
Catania, 11/Jun./2014 S.Basso - INAF OABrera
Check for tilt of lenses
The presence of the baffle creates an asimmetry
window: 10.140 arcsec
L1: 0.058 arcsec
FE Model results:Thermo-elastic for conf. 1&4
The thermo-elastic model is OK
D Z [mm] Tilt [arcsec]
Window -589 10.140L1 -507 0.058L2 -450 0.029L3 -334 0.018L4 -225 0.016L5 -200 0L6 0 0
Tilt up to 25 arcsec do not influence
High dependence from the baffle material
Catania, 11/Jun./2014 S.Basso - INAF OABrera
FE Model results:Conclusion
Catania, 11/Jun./2014 S.Basso - INAF OABrera
The new analyses show that the latest change in the I/F parameter move away from the goal to reach -90°C in the TRP (Temperature Reference Point) with the heaters off. The greater effect is the decrease of the CSS temperature from -10°C to -63°C.In order to increase again the TRP Temperature to the goal the possibility are:1. Increase the heaters power adding 1W for the normal TOU and 0.2W for the fast
TOU. That means that the total heater power would increase of 32*1+2*0.2= 32.4W 2. Reducing the decoupling between the Camera I/F plane building bipods more
conductive. This solution would increase the uncertainty in the mean temperature of the telescopes because the temperature of the Camera I/F plane is less known.
3. Adopt not conventional approaches like:• titanium baffle, • thermal filters• coating or layer on the internal surface of the baffle to reduce the internal
emissivity