1. Introduction and discussion of background and important ... · – User can combine all...

��

� ��

��

James Etchells (TEC-MCV)

19th European Workshop on Thermal and ECLS Software

11th–12th October 2005

Sheet 2

11 - 12 October 2005


��

� ��

� � ��

1. Introduction and discussion of background and important issues

2. Comparison of TLP and FEA for S/C thermal analysis

3. Presentation of developed tools with accompanying examples

4. Combination of tools to allow hybrid FEA/TLP analysis

5. Conclusions

6. Questions

Sheet 3

11 - 12 October 2005


��

� ��

�� ! " #$ �� % ��& ��

• Traditionally S/C thermal analysis uses Thermal Lumped Parameter (TLP) method– Physical system represented as an abstract ‘network’ of conductors and capacitances– Based on 1st order Finite Difference discretisation of governing PDE– Industry standard tools: ESATAN, SINDA

• In the past lumped parameter methods were used for many application domains– e.g. Structural, Fluid Flow, Thermal, Electromagnetic– complex problems abstracted and analysed using limited computing resources of the day

• Recently FEA gained widespread popularity – especially for structural analysis– Shift to FEA made possible by vast improvements in computational hardware– Excellent pre/post processing tools, CAD import, mesh generation– Intrinsic link with physical geometry

• However, the S/C thermal analysis community is reluctant to embrace FEA– But the method has much to offer so why the reluctance?

Sheet 4

11 - 12 October 2005


��

� ��

�� ' " #� �� ( �� ) * � ��

• FEA often considered inefficient compared with TLP– Inappropriately large thermal models with FEA –unsuitable for system level analysis

• Perception that FEA is ‘non-physical’ method – negative conductors often cited

• Lack of Thermal Control functionality in FEA tools– Valid point but problem lies with current FEA tools NOT the method

• Lack of dedicated radiation analysis tools for FEA– Some FEA tools support radiation exchange – but very limited (only geometric VF’s)– No support for specular reflectivity, environmental fluxes, orbit definition, kinematics etc.

• Thermal engineers often not interested in precise temperature fields– More interested in system level heat flows– But very precise temperature fields will be required for future scientific missions

• Cultural inertia - over 40 years of experience with TLP– Thermal engineers have confidence in TLP and experience with the tools

Sheet 5

11 - 12 October 2005


��

� ��

� �� ) * � ��

•FEA pre-processors extremely powerful for building geometry – meshing and CAD import

•Limited radiative anal. functionality in current FE tools – no specularity or orbital fluxes

•No conductor generation necessary – conduction matrix from mesh and material props.

•Lack of functionality for thermal control – element library designed for structures

•Excellent post-processing tools – contour plotting on mesh, x-y plotting, etc.

•Mapping temperatures. to structural FE mesh is made easier - intrinsic link with geometry

•GMM built in radiative analysis tool – geometry only used for radiation, no CAD link

•Powerful radiative anal. tools (e.g. ESARAD) - specularity, orbit definition, heat fluxes

•Conductor generation required for TMM – often done manually – major bottleneck

•Thermal anal. and control in TLP tool with functionality for – fluid loops, subroutines, etc.

•Post-pro with spreadsheets, ad-hoc scripts etc - mapping temps to structural FE difficult

TL

PF

EA

GMMRadiativeAnalysis

ConductorGeneration

StructuralMapping

PostProcess

ThermalAnalysis

ThermalControl

Sheet 6

11 - 12 October 2005


��

� ��

� ( +�� , � �&

• Several targets were identified:1. It should be possible to use the functionality of FE pre-processors to create a GMM

2. Important to be able to use S/C radiative analysis tool (e.g. ESARAD) with FE mesh

• Also important to map exchange favtors and

3. Hybrid TLP/FEA thermal analysis (c.f. Thermal Desktop) is attractive

• Combine benefits of FEA (e.g. no conductor gen.) & TLP (e.g. control elements)

• Hybrid TLP/FEA thermal analysis using TLP tool as general equation solver

• Allows gradual integration of FEA – users must gain experience and confidence

Sheet 7

11 - 12 October 2005


��

� ��

�� ! #- � � ' � � �

• Key benefit of FEA is functionality in pre-processing tools– Automatic meshing, CAD import, “point-and-click” modelling, link to parametric data or concept model possible

– We can use this functionality to create GMM for analysis of radiation exchange

• NAS2TAS was developed – converts radiativepart of NASTRAN Thermal FE model to STEP-TAS– Allows development of GMM in any pre-processor that supports NASTRAN BDF (Patran, FEMAP, CATIA)

– Patran/NASTRAN chosen due to availability at ESTEC – ABAQUS, SAMCEF, ANSYS etc. could have been used

• Use of STEP-TAS as neutral format allows any supported radiative tool to be used for analysis– Currently ESARAD and THERMICA supported – TRASYS, RadCAD in future

TLP

FEA


ConductorGeneration

StructuralMapping

PostProcess

ThermalAnalysis

ThermalControl

Sheet 8

11 - 12 October 2005


��

� ��

�� ! #- � � ' � � �

Develop GMM in Preprocessor

NASTRAN

BDFNAS2TAS

ESARAD

erg

THERMICA

SYSBAS

TRASYS

inp

STEP-TAS

stpTASverter

Sheet 9

11 - 12 October 2005


��

� ��

• Real practical example where NAS2TAS was used

• Validated ESARAD model of LSS existed – but Boolean cutting operations used

• THEMICA LSS model was required – cutting operations not supported in THERMICA

• Patran used to build faceted model – powerful modelling functionality and meshing

. ��! #/ �� / � � " * � �� 0 ��

ESARAD with cutting MSC PatranTHERMICA

Sheet 10

11 - 12 October 2005


��

� ��

�� ' #1 � �� 2 , ��

• Many FEA codes have some in built radiation exchange functionality – but limited– No support for specular reflectivity, calculation of environmental heat fluxes, mission definition etc.– But NASTRAN permits user to supply pre-defined radiative couplings – RADMTX matrix

• RADMTX Writer maps REF’s and heat fluxes from radiative analysis tool to NASTRAN– GR’s and HF’s calculated with radiative tool and written to ESATAN input deck– Both ESARAD and THERMICA can produce ESATAN input decks

• Tool was developed to map REF’s and HF’s from ESATAN deck to NASTRAN– Mapping via an ESATAN deck reader – implemented in python

• Thermal analysis carried out using FEA in NASTRAN

TLP

FEA


ConductorGeneration

StructuralMapping

PostProcess

ThermalAnalysis

ThermalControl

Sheet 11

11 - 12 October 2005


��

� ��

�� ' #1 � �� 2 , ��

Develop FE Model in Preprocessor

NASTRAN

BDF

ESARAD erg

THERMICA SYSBAS

NAS2TAS/

TASverter

Radiative Analysis

NASTRAN Thermal

FE Solver

RADMTX Writer

Include Files:

radmtx.dat

fluxes.dat

NASTRAN

Results

Post-process FEA

e.g. Patran

ESATAN

Model.d

Sheet 12

11 - 12 October 2005


��

� ��

�� ' #1 � �� 2 , ��

Sheet 13

11 - 12 October 2005


��

� ��

�� 3 #� ' � � -

TLP

FEA


ConductorGeneration

StructuralMapping

PostProcess

ThermalAnalysis

ThermalControl

• FEA does not require conductor generation – huge advantage over TLP methods– Disadvantage of FEA tools is the lack of flexibility for subroutines, control loops etc.

• But TLP codes such as ESATAN/SINDA just solve systems of equations – Thus it is possible to cast FEA equations (matrices) in TLP form and solve in TLP tool

• FE2TAN tool maps NASTRAN conduction elements to ESATAN conductors & capacitances

• Hybrid FEA/TLP approach possible due to use of ESATAN for thermal analysis– User can combine all functionality of ESATAN with detailed FE model - subroutines, fluid loops…

Sheet 14

11 - 12 October 2005


��

� ��

� ' � � - #�� / � ��

32

41

��

�

�

��

�

�

=

44434241

34333231

24232221

14131211

KKKK

KKKK

KKKK

KKKK

Ke

��

�

�

��

�

�

=

44434241

34333231

24232221

14131211

CCCC

CCCC

CCCC

CCCC

Ce

$CONDUCTORSGL(1,2) = -K12GL(1,3) = -K13GL(1,4) = -K14GL(2,3) = -K23GL(2,4) = -K24GL(3,4) = -K34

$INITIALC1 = C11+C12+C13+C14C2 = C21+C22+C23+C24C3 = C31+C32+C33+C34C4 = C41+C42+C43+C44

Sheet 15

11 - 12 October 2005


��

� ��

� ' � � - #� � ��

• Currently CTRIA3, CQUAD4, CTETRA, CELAS, CDAMP elements can be written to TAN– CELAS analogous to TLP linear conductor– CDAMP analogous to TLP lumped capacitance

• Non-isotropic material properties and temperature dependence not yet supported

• Functionality to include radiation exchange (GR’s) between FE grid points

• ESATAN template file can be used to define structure of model – solution routines etc.

• Element conduction/capacitance matrices formed using code written from scratch– Validation of the methods used is thus an issue – but we can compare with NASTRAN

Create FE Model in preprocessor

e.g. Patran

NASTRAN

.BDF FE2TANESATAN

Model.d

User Logic

Control

ESATAN SolverESATAN

results

Optional ESATAN template

.Optional GR’s

Sheet 16

11 - 12 October 2005


��

� ��

4 �� ' � � - #�� * � �� & ��

Q W/m-2

Boundary Temperature

Q W/m-2

Q W/m-2

Problem Definition

FE2TAN Results: Solution in ESATAN

NASTRAN Results

Create Patran/NASTRAN Mesh

Sheet 17

11 - 12 October 2005


��

� ��

* � �( �� #� � ��$ � ( ��

FEM Pre/Post Processor(PATRAN, FEMAP)

NASTRAN.BDF

NAS2TAS/TASverter--from_BDF

Input Deck for Radiative Toolwith TASverter writer

ESARAD: ergTHERMICA: SYSBAS

Radiative ToolESARAD/THERMICA

ESATAN deck

Model.dGR’s, Fluxes

FE2TAN

TASverter--from_GFF --to_patran

User LogicProcedural ControlTLP components

ESATAN

Model.dGL’s, GR’s, Fluxes

ESATAN/ThermXL

ESATAN results

.GFF

Kernel

e.g. erk

TAN template

e.g. ere

Sheet 18

11 - 12 October 2005


��

� ��

. ��3 #$ � ( �� ) � / � 5 * � ��

• Electronics units with power dissipation mounted on a shelf – reject heat to DS via radiator

• Single phase fluid loop chosen to transport heat to radiator

• Optimisation of fluid loop requires accurate temperature field prediction on shelf– FEA excellent method to model conduction on electronics shelf accurately

• BUT no capability to model fluid loops in NASTRAN – must use TLP

Sheet 19

11 - 12 October 2005


��

� ��

�� 6 ��. ��#* � ��

• NASTRAN radiation enclosure geometry mapped to ESARAD – NAS2TAS and TASverter

• NASTRAN conductive model mapped to ESATAN – FE2TAN

• Fluid loop ESATAN model defined manually – GF’s and GL’s– Standard pipe flow – Prandtl, Nusselt number approach with expressions coded in $VARIABLES1

• Steady state thermal analysis with ESATAN – results written to GFF format

• GFF file mapped back to Patran for post-processing – TASverter GFF reader

D500 = ' NASTRAN Gr i d Poi nt 500' , T = 2. 731500E+02[ K] ;D501 = ' NASTRAN Gr i d Poi nt 501' , T = 2. 731500E+02[ K] ;D502 = ' NASTRAN Gr i d Poi nt 502' , T = 2. 731500E+02[ K] ;D503 = ' NASTRAN Gr i d Poi nt 503' , T = 2. 731500E+02[ K] ;B99999 = ' DEEP SPACE' , T = 3. 0[ K] ;

$CONDUCTORS#NASTRAN CQUAD4 HEAT CONDUCTI ON ELEMENT. ELEMENT I D 1GL( 1, 2) = 4. 625000E- 02;GL( 1, 23) = 9. 250000E- 02;GL( 1, 22) = 4. 625000E- 02;GL( 2, 23) = 4. 625000E- 02;GL( 2, 22) = 9. 250000E- 02;GL( 23, 22) = 4. 625000E- 02;#END OF NASTRAN ELEMENT 1 ESATAN deck sample

Sheet 20

11 - 12 October 2005


��

� ��

�� 6 ��. ��#� � � �7��

• Nodal results data imported to Patran

• Contour plotting available on geometry

• Data extraction and XY plotting

• Temperatures linked to geometry– Mapping to structural mesh more simple

Sheet 21

11 - 12 October 2005


��

� ��

�� 6 ��. ��#� � � �7��

Flow

dir

ectio

n

Sheet 22

11 - 12 October 2005


��

� ��

� � �� , � �&

• Integrate NAS2TAS as a reader module in future TASverter release– Including development of a formal test suite – unit tests etc.

• FE2TAN tool should produce STEP-TAS network model – not ESATAN model– Create STEP-TAS conductors “nrf_network_node_relationship’s”– Extension to include temperature dependent properties and more elements

• Extension of TASverter GFF reader to read ESARAD results into STEP-TAS– GFF reader supports ESATAN type results but ESARAD rpt. is also a valid GFF file

• Develop ESARAD/THERMICA primitives that are more compatible with FE’s– Shells analogous to curved finite elements – allows higher order elements to be used– Raytracing between finite element nodal points – not isothermal faces

• Research into model reduction– FE models can have many degrees of freedom – how to interface with system level model– Reduction of linear conduction models is simple – non-linear (radiation) difficult

Sheet 23

11 - 12 October 2005


��

� ��

* � ��

• Several tools were developed to aid integration of FEA into S/C thermal analysis– Long term goal is a co-existence of TLP/FEA – this project should be seen as a first step– Thermal engineers should be able to choose the analysis method best suited for a given

application

• Important aspect of the development was use of neutral formats (STEP-TAS)– STEP-TAS can aid the development of new methodologies– Generality and tool-independence of ideas is extremely important - all the ideas used in

the tools can be applied directly to other tools

• Users can try the tools and gain some experience and confidence with FEA – All the methodologies use existing tools – minimum financial investment or time

commitment– All tools and documentation available on the web - http://exchange.esa.int– Tutorials for the tools are almost complete and will also be published

Sheet 24

11 - 12 October 2005


��

� ��

� �& ��

During the course of my YGT period I received support from many people. I would particularly like to thank:

• Harrie Rooijackers – Supervisor for my YGT period

• Simon Appel

• Everybody in TEC-MCV/TEC-MCT at ESTEC

1. Introduction and discussion of background and important ... · – User can combine all...

Documents

Transcript of 1. Introduction and discussion of background and important ... · – User can combine all...