33
Appendix C
Evaluation of Heat Transfer Parameters from CFD for Use inTMM in Case of Gas Convection in Vented Cavities
Christian Wendt(Astrium Space Transportation, Bremen, Germany)
27th European Space Thermal Analysis Workshop 3–4 December 2013
34Evaluation of Heat Transfer Parameters from CFD for Use in TMM in Case of Gas Convection
in Vented Cavities
Abstract
The analysis of the convection in Ariane 5 launcher’s vented cavities on ground and during ascent isimportant for the thermal control of the equipments and of the propellants during flight phase. For theaccording analysis of the upper stage, a lumped parameter Thermal Mathematical Model (TMM) hasbeen established within ESATAN.As an input, heat transfer parameters (HTPs) have been derived from two related Computational FluidDynamic (CFD) analysis cases, the so called hot and cold case. The methodology for evaluation of theseHTPs from the CFD analysis is described for one and more gas nodes based on steady state results. For arepresentative launcher cavity with laminar/turbulent buoyancy influenced flow, a comparison is providedbetween the TMM results and the CFD results obtained with the commercial tool ANSYS Fluent. Exactagreement is achieved between TMM and CFD for the hot and the cold case. Deviations for the analyzedintermediate cases turned out to be less than 5K in case of a one gas node TMM and less than 3K in caseof a seven gas node TMM.
27th European Space Thermal Analysis Workshop 3–4 December 2013
Evaluation of Heat Transfer Parameters from CFD for Use in TMM in Case of Gas Convection in Vented Cavities
27th annual European Space Thermal Analysis Workshop, 3rd & 4th Dec. 2013, Noordwijk
C. Wendt, Astrium Space Transportation, Bremen, Germany
• Introduction
• Background
• Description of Methodology
• Test Case
• Conclusion & Outlook
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Page 2
Introduction: Example A5ME Ground Phase
LOXLH2
EBS Cavity with N2 venting(or He venting)
ETF Cavity with N2 venting
Interstage Cavity with N2 venting
Evaluation of Heat Transfer Parameters from CFD for Use in TMM in Case of Gas Convectionin Vented Cavities 35
27th European Space Thermal Analysis Workshop 3–4 December 2013
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Page 3
Background: Check of CFD with Cryo-Tests
N2 vented cavity with a simplified typical geometry
Variable temperature of heat exchanger to realize several test cases
Good agreement betweenCFD and test
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Page 4
Method: Approach for HTPs from CFD
36Evaluation of Heat Transfer Parameters from CFD for Use in TMM in Case of Gas Convection
in Vented Cavities
27th European Space Thermal Analysis Workshop 3–4 December 2013
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Page 5
Method: Gas/Wall Heat Transfer GLs from CFD
hotiw
hoti
hotiwhot
iw TTQ
GL,
,,
coldiw
coldi
coldiwcold
iw TTQ
GL,
,,
)(,,,,
coldinincold
inhotin
coldiw
hotiwcold
iwiw mmmmGLGL
GLGL
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Page 6
Method: Gas/Gas Heat Transfer GFs and Qs from CFD
)()()()(
),( ,,,,
coldi
coldjijcold
icoldj
hoti
hotj
coldig
hotigcold
igjiig TTTTTTTT
QQQTTQ
)()(,,
coldi
coldj
hoti
hotj
coldig
hotig
i TTTTQQ
GF
)()()(
,,,
coldi
coldjcold
icoldj
hoti
hotj
coldig
hotigcold
igi TTTTTT
QQQQ
Evaluation of Heat Transfer Parameters from CFD for Use in TMM in Case of Gas Convectionin Vented Cavities 37
27th European Space Thermal Analysis Workshop 3–4 December 2013
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Page 7
Method: Venting Inlet/Gas Heat Transfer GFs and Qs from CFD
)()()()(
),,( ,,,,
coldi
coldin
coldiniinincold
icold
incoldin
hoti
hotin
hotin
coldig
hotigcold
igiininig TTmTTmTTmTTm
QQQTTmQ
)()(,,
coldi
coldin
coldin
hoti
hotin
hotin
coldig
hotig
ini TTmTTmQQ
mGF
)()()(
,,,
coldi
coldin
coldincold
icold
incoldin
hoti
hotin
hotin
coldig
hotigcold
igi TTmTTmTTm
QQQQ
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Page 8
Test Case: EBS Cavity
DescriptionTemperature
Wall 1[K]
Temperature Wall 2
[K]
Mass Flow Temperature
[K]
Mass Flowrate up
[g/s]
cold 200 220 294 60hot 210 250 314 80
38Evaluation of Heat Transfer Parameters from CFD for Use in TMM in Case of Gas Convection
in Vented Cavities
27th European Space Thermal Analysis Workshop 3–4 December 2013
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Page 9
Test Case: CFD Results for Cold + Hot Case
cold case
hot case
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Page 10
Test Case: TMM
Evaluation of Heat Transfer Parameters from CFD for Use in TMM in Case of Gas Convectionin Vented Cavities 39
27th European Space Thermal Analysis Workshop 3–4 December 2013
Page 11
Test Case:Comparison between TMM and CFD
Case Nr.
Temperature Wall 1[K]
Temperature Wall 2 [K]
InletTemperature[K]
Mass Flowrate up [g/s]
1 205 235 304 70
2 205 235 314 60
3 205 235 294 80
4 195 210 274 60
5 215 260 334 80
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Page 12
Test Case:Comparison between TMM and CFDOne Gas Node Model
-4
-3
-2
-1
0
1
2
3
4
5
cold hot 1 2 3 4 5
Case
∆Te
mpe
ratu
re [K
]
∆Twall average [K]Max |∆Twall| [K]∆Tgas [K]
Seven Gas Node Model
-4
-3
-2
-1
0
1
2
3
4
5
cold hot 1 2 3 4 5
Case
∆Te
mpe
ratu
re [K
]
∆Twall average [K]Max |∆Twall| [K]∆Tgas average [K]Max |∆Tgas| [K]
40Evaluation of Heat Transfer Parameters from CFD for Use in TMM in Case of Gas Convection
in Vented Cavities
27th European Space Thermal Analysis Workshop 3–4 December 2013
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Page 13
Conclusion & Outlook
• Methodology for transfer from CFD to TMM explained for vented cavities
• Comparison beween TMM and CFD showed good overall agreement for EBS Cavity for the One Node and Seven Nodes Model as well: Seven Gas Node Model about ~40% better than One Gase Node Model
• Method is currently enhanced to include time dependency, as needed e.g. for propellant stratification phenomena
One Node Model Seven Node Modelmaximum temperature deviation ~4K ~2.5Kmaximum LH2 heat flux deviation ~1% ~0.5%
Evaluation of Heat Transfer Parameters from CFD for Use in TMM in Case of Gas Convectionin Vented Cavities 41
27th European Space Thermal Analysis Workshop 3–4 December 2013
42
27th European Space Thermal Analysis Workshop 3–4 December 2013