An overview of four analysis capabilities, which developed and integrated into the NASTRAN Thermal Analyzer, is given. To broaden the scope of applications, these additions provide the NTA users with the following capabilities: (1) simulating a thermal louver as a means of the passive thermal control, (2) simulating a fluid loop for transporting energy as a means of the active thermal control, (3) condensing a large sized finite element model for an efficient transient thermal analysis, and (4) entering multiple boundary condition sets in a single submission for execution in steady state thermal analyses

Harder, R. L.

Lee, H. P.

English

NASA Technical Reports Server

THE GSFC NASTRAN THERMAL ANALYZER NEW CAPABILITIES
Hwa- Ping Lee
NASA Goddard Space Flight Center
Robert L. Harder
The MacNeal-Schwendler Corporation
SUMMARY
An overview of four new analysis capabilities, which have been developed and
integrated into the GSFC NASTRAN Thermal Analyzer, is given. To broaden the scope
of applications, these new additions provide the NTA users with the following capabili-
ties of: (1) simulating a thermal louver as a means of the passive thermal control,
(2) simulating a fluid loop for transporting energy as a means of the active thermal
control, (3) condensing a large-sized finite-element model for an efficient transient
thermal analysis, and (4) entering multiple boundary condition sets in a single submis-
sion for execution in steady-state thermal analyses.
INTRODUCTION
Four new capabilities have been recently developed and integrated into the GSFC
NASTRAN Thermal Analyzer (blTA), which is a finite-element based general-purpose
heat transfer computer program in the NASTRAN system (refs. 1, 2, 3). The NTA
was originally designed to analyze a large and complex space-borne telescope optical
sub-system (refs. 4, 5). The new additions have broadened the scope of engineering
application of the NTA from component level to system level, so that complete space-
craft, which would generally require passive and/or active thermal controls, can be
treated. Also, the manipulative options relating to the operational efficiency of the
computer program can become critical when large numbers of elements or grid points
are employed in modeling rather than dealing with a problem of a small size. Specifi-
cally, the four new capabilities are:
(1) Temperature-dependent emissivity and absorptivity.
(2) One-dimensional thermo-fluid elements.
(3) The condensation of a finite-element thermal model including the non-linear
radiative effect.
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https://ntrs.nasa.gov/search.jsp?R=19770013548 2020-03-20T07:32:35+00:00Z
(4) The entry of multiple boundary condition sets in a single submission for
execution.
The purpose of this paper is to provide NASTRAN users with an overview of these
new capabilities. Definition, scope, features and limitation of each individual item are
given. New elements needed to facilitate functional objectives are introduced. The use
of these new elements together with the appropriate solution routines are described.
Essential parts of program changes and new elements interfacing with different func-
tional modules in the NTA are outlined.
TE MPE RATURE- DE PENDENT E MISSIVITY AND ABSORPTIVITY
In the Level 15.5 NTA, the solution algorithm pertaining to the radiative exchanges
is limited to the diffuse-gray case. The programming code is, therefore, sufficient to
enter a single constant value for the emissivity, e, and the absorptivity, c_, of each
surface. As a result, the radiation matrix (the module RMG) is symmetric. These
program restrictions have been eliminated by this new capability which permits an
independent specification of temperature-dependent emissivity e(T) and absorptivity a(T).
The application of this feature is for transient thermal analysis only. A notable engi-
neering application is to simulate a thermal louver as a means of the passive thermal
control.
To accommodate temperature-dependent emissivity and absorptivity through the
boundary surface element, HBDY, the RMG module would have to be restructured.
Such a rigorous approach would result in a prohibitively large effort, and excessively
long computer run times would be required for the following reasons:
(1) The matrices which express the radiation properties are generated in the module
RMt '_. urh{oh _S ...... +^'_ .... '--
................. ._u vaity ill the program.
(2) If emissivity and absorptivity are temperature-dependent functions, it would be
necessary to execute the RMG module and all subsequent modules up to and including
the solution module, TRHT, for each time step.
(3) If radiative heat flow was requested in the output, it would be necessary to execute
the data recovery modules after each time step, because NTA does not have the
ability to store the separate radiation flux matrices [Qge ] for each time step.
Although less flexible than the rigorous approach, art alternative has been adopted
to employ the existing general nonlinear capability of NASTRAN (ref. 6). A nonlinear
120
element, NOLIN5*, has been newly introduced (ref. 7}. It allows the emissivity and
the absorptivity to be given independently as tabular functions of the radiating surface
temperature.
NOLIN5 differs from other NASTRAN nonlinear load cards in that a large number
of grid points may be involved. An area factor A i is associated with each grid point.
For the emitting surface, the convention is adopted that Ai _> 0. The sum of the area
factors of the grid points associated with the emitting surface is one; hence the average
temperature Tar, of the emitting surface is
Tav = i_AiTi (1)
Other grid points, assigned to receive the radiation, are given area factors which are
negative and are not included in the calculation of Way . The emissivity e (Tar) is given
as a tabular function of Tar by one of the TABLEDi data cards, as is the absorptivity
_(Tav ). The rate at which the radiative heat is treated as a nonlinear load at point i is
given by
N i = -SoAie(Tav ) (-I'av + Tabs) 4 (2)
where S and A i are data items and a, the Stefan-Boltzmann constant, and Tab s , a datum
temperature in an absolute scale, are rigid format parameters.
have been made to the program:
IFP
DPD
TRHT
Rigid Format (SOL 9)
The following changes
New card NOLIN5.
Add NOLIN5 to subroutine DPD4.
Add parameter TABS, SIGMA; add NOLIN5 to
subroutine TRDID.
Add parameter to TRHT.
ONE-DIMENSIONAL THERMO- FLUID ELEMENTS
A simple but commonly used energy transporting means is the fluid loop consisting
of a flowing fluid inside a tube, which may be made to contact a thermally conductive
structure. New elements have been developed and added to the NTA to allow the effect
of an active thermal control to be included in a model.
*The names of actual NTA cards are capitalized and underlined.
121
The tube to convey the flowing fluid is modeled using the existing TUBE element
with modification that allows a tube of uniform wail thickness to have a constant bore
and a linearly tapered geometry as well. The convective heat exchange between the
fluid and the tube and any heat transferring from the tube to the surroundings are
modeled using HBDY elements as shown in Figure 1. The HBDY element has been
modified, as is reflected in the PHBDY data card, to accommodate the linear taper.
The developed thermo-fluid elements are available to both the cases of steady-
state and transient thermal analyses. For steady-state analysis, a constant flow rate
is specified by the user. A new fluid element FTUBE has been introduced. The
unusual feature of this element is that it possesses an asymmetric conduction matrix
which is characterized by the fluid phenomenon (ref. 8). This element has created a
connection C FTUBE and a property PFTUBE data cards. Element routines are needed
for IFP, SMA1, SMA2, SDR2, and OFP. This new fluid element can be used in the
nonlinear steady-state solution routine, the rigid format APP HEAT, SOL 3.
For transient analysis, a table, TABLEDi, may be provided by the user with a
time-dependent flow rate function. In addition to the FTUBE element, the fluid cylinder
is also treated as a nonlinear load. A new nonlinear element NFTUBE has been
introduced. Both methods can be used in the transient solution routine, the rigid format
APP HEAT, SOL 9. These two approaches, the element method and the nonlinear load
method, are equivalent and equally simple to apply as far as the user is concerned.
The following changes have been made to the program for this thermo-fluid
capabil ity:
IFP Modify PTUBE, CHBDY; new CFTUBE, PFTUBE,
NFTUBE.
GPTA1 New entries for block data.
SMA1, SMA2 FTUBE routine (asymmetric output); fix HBDY type
"FTUBE".
SDR2 Compute convected power in FTUBE
OFP Output SDR2 results.
DPD Add NFTUBE to subroutine DPD4
TRHT Add NFTUBE to subroutine TRDID.
122
THE CONDENSATION OF A FINITE-ELEMENT THERMAL MODEL
\
Condensation is the reduction of the number of temperature variables (or the
generalized degrees-of-freedom in the NASTRAN system) used for solution efficiency.
The OMIT feature of NASTRAN was designed to provide the model condensation. This
feature has been extended to the transient thermal analysis, using the rigid format APP
HEAT, SOL 9, t 9 include linear and nonlinear boundary conditions. It is accomplished
through matrix transfer and partitioning. The computer code has been modified to
allow for asymmetric matrix operations. As a result, the restriction used to limit
"a grid point which is OMITted may not touch any nonlinear elements" has been removed.
This feature, however, is not available to the nonlinear steady-state thermal
analysis. Since the possible increase of the computer run time expenditure due to the
mathematical manipulations would not be justified by the saving that would be realized
by a condensed model ha the steady-state case.
The program ch_es made to accommodate this capability have been modifications
of MCE2 and SMP1 for asymmetric operations.
THE ENTRY OF MULTIPLE BOUNDARY CONDITION SUBCASES IN ONE EXECUTION
The counterpart of this capability in NASTRAN has been known to its users as the
SUBCASE, but this capability was not available to any of the three rigid formats in the
NTA. To loop through several subcases of distinct boundary condition sets is a very
desirable feature, especially for a large-sized NTA model, ha which the types of input
data card of a problem generally consist of the conduction elements (the connection and
property data cards), the boundary surface elements, the material cards, the radiation
matrix input cards (RADLST and RADMTX), and different thermal loading cards for
specifying boundary conditions. Usually, thermal loadings need only a few cards to
describe needed quantities and conditions in steady-state cases, while the rest of cards
constitutes the major part of a bulky input deck. This feature has been developed and
used to eliminate time-consuming repetitive submissions of bulky input data decks in
succession with only changes pertaining to thermal loadings varied from case to case.
This multiple entry feature is limited, however, to steady-state thermal analyses using
the rigid formats of APP HEAT, SOL 1 and SOL 3. Specifically, a DMAP-ALTER has
been added to handle the following loops for
(1) Only thermal loads are changed.
(2) The MPC and SPC constraints are changed.
(3) The boundary surface elements CHBDY are changed.
123
The required program changes for looping in this rigid format APP HEAT, SOL 3, are
summarized as follows:
Write ALTER
Fix to IFP1, PARAML for ALTER.
The DMAP-ALTER packet is shown in Figure 2 for reference.
RE FERENC ES
.
.
o
.
.
1
Lee, H. P., and Mason, J. B. : NASTRAN Thermal Analyzer- A General Purpose
Finite-Element Heat Transfer Computer Program. The 2nd NASTRAN User's
Colloquium. NASA TMX-2637. Sept. 1972, pp. 443-454.
McCormick, C. W. : The NASTRAN User's Manual. NASA SP-222. Washington,
D.C., Sept. 1970.
Lee, H. P. : NASTRAN Thermal Analyzer -- Status, Experience and New
Developments. The 4th NASTRAN User's Colloquium. NASA TMX-3278.
Sept. 1975, pp. 523-528.
Lee, H. P.: Structural-Thermal-Optical-Program (STOP), Paper presented at
NASA-GSFC 1970 Science and Technology Review, NASA-Goddard Space
Flight Center, Jan. 13-14, 1971; also appears in: Significant Accomplish-
ments in Technology: Goddard Space Flight Center, 1970. NASA SP-295.
Washington, D.C., 1972, pp. 36-40.
.... T_ Using L, NASTRAN Thermal Analyzer toLee, H. P., and Jackson, c _ , _.: _uv
Simulate a Flight Scientific Instrument Package. Proceedings of the 20th
Annual Meeting of the Institute of Environmental Sciences, Apr. 1974,
pp. 152-158.
MacNeal, R. H. (Editor): The NASTRAN Theoretical Manual. NASA SP-221,
with Level 15.5 Updates. Washington, D.C., Dec. 1972.
124
eas
Harder, R. L. : Functional Module Mathematical Specifications for the New
Capabilities to be Added to the NASTRAN Thermal Analyzer. Report EC-346-1,
(under the Contract NAS5-22560). The MacNeal-Schwendier Corporation,
Oct. 1975.
Lee, H. P. : "On the One-Dimensional Thermo-Fluid Element." NASA'GSFC
Test and Evaluation Division, Program STOP-Document, Greenbelt, Maryland,
Jan. 1975.
°,[
I
G2
,I
G3I
HBDY
I TUBE i
I
I G5
IHBDY
g
I -
Exterior Structure Temperatures
Conductive, Convective, and/or
Radiative Heat Exchange
Tu be Temperatures
Convective Heat Exchange
Fluid Temperatures
J,
Figure 1. Combination of the NTA elements to simulate thermo-fluid effects
125
$ THE DMAP-ALTER PACKET TO ALLOW BOUNDARY COt_[)ITION SETS CHANGED IN
$ TO ALLOW TEMP(MATERIAL) TO VARY FROM SUBCASE TO SUEECASE" ALTER IO
$ TO ALLOW SPC OR MPC TO VARY FROM SURCASE rc) SU_CA.$_: ALTER 31
$ TO ALLOW THERMAL LOAD TO VARY FROM SUBCASF TO SUBCASE: ALTER 58
ALTER 7,7
PLTHBDY GEOM2,HECT )EPT ,HSI L,HEQEX IN,HBGPDTI_BCT, PSI L, PEO IN, Pb(;PF)T/
V, N,NHBDY/V,Y ,MESH=NO $
SAVE NHBDY $
EQUIV HECT,PECT,/NHBDY/HSIL,PSIL/NHBDY/HE_EXIN,PE(.)IN/NHBDY/HRGPnT,
PBGPDT/NHBDY $
PLTSET PCD8, PEOIN, PECT/HPLTSETX,HPLTPAR, HGPSETS, HELSETS/V, N, HNSI L/
V,N,JUMPPLOT $
ALTER 13,13
PLOT HPLTPAR,HGPSETS ,HELSETS ,CASECC) PHGPr) F, PEq I,_l,PSI L, ,, ,/
HPLOTXI/HNS IL/HLUSET/JUMPPLOT/V,N,HPLTFLG/V,N,HPE ILlz $
ALTER lq
SETVAL //V,N,REPEATT/-I $
LABEL LOOPTOP
CASE CASECC,/CASE XX/TRAN/V ,N, REPEATT/V, N,N()L UOP $
SAVE R_PEATT,NOLOOP $
PARAML CASEXX//OTI/I/8//V,N,TEMPHATE $
PARAM //STSR/V,N, TEMPMATE/- IO $
ALTER 32,32
GPZ+ CASEXX ,GEOM4,HEOEX IN,HS I L,HGPI)T, ) /HRG, ,HIJ')':T,IHI_iJSET/
V,N,HMlaCFt/V_N,HMPCF2/V,N,HSINGLE/V,I'*..HI_'4| T/V,_\I,HREACT/
0/O/V I,N ,HNOSET/V,N, HNOL/V, N, HNOA $
ALTER 33,33
SAVE HMPCF1,HMPCF2,HSINGLE,HOMIT,HREACT,HNF)SC_T,iI,,I()L,HqOA $
ALTER 37,37
CHKPNT HGM ,HPS, HK ES, HKSS, HUS ET ,HRG, HKNil, H)_,,I,,I,_-_<S _:,I-_'_SN $
ALTER 54
PARAM //C,N _AOO/V _Y, KSYM/-I/0 $
ALTER 59,59
SSGI HSLT,HBGPOT,HCSTM,HSIL,HEST,MPT,HGPTT,i-I)[,, :AS=XX,_;IT/H_G/
HLUSET/I $
ALTER 63,63
SSG2 HUSET,HGM, ,, ,,HPG/ , ,HPS,HPF $
ALTER 74,74
SOR2 CA S E X'X,HCSTM, MPT, O IT, HE'0E X IN , ,HGPT T ,E I)T,Hr_GPI}P ,H I-_(G, H(J(},
HUGV , HE S T , /HOPG I ,HOOG ]. , HOUGV ]. ,HOF: S L , H()E'z L , H,_I J(_V t / ST /_T I C S
ALTER 81,81
PLTSET PCF)_,HEQEX IN )HECT/PSMES,I)PI TPA_,OGPS-T.q,_Oi'_S_[S/V,<.I,_IL/
V,N,f)J $
SAVE DS I L $
PLOT DPLTPARtOGPSETS,f)ELSETS,CASEXX,HBGPr)p,HEC)_xIi\I,HSIP,HPIIGVI,,
HECPT ,HOESI/HPLOTX2/DSIL/HLUSEP /JUMPPLOT /V,N,HPLTrLG/
V,N,HPFILE $
SAVE HPEILE $
ALTER 83
COND EINIS,REPEATT
REPT LOOPTOP, IO0
JUMP HERROR3 $
$ END OF OMAP-ALTER (53548)
RF-HEAT,3
Figure 2. The DMAP-ALTER packet for the multiple boundary condition subcases in
one execution.
126


The GSFC NASTRAN thermal analyzer new capabilities

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