%42) *OURNAL VOLUME NUMBER *ULY
! 3TUDY ON 4HERMAL 0ERFORMANCE OF (EAT 0IPE FOR /PTIMUM 0LACEMENT OF 3ATELLITE %QUIPMENT
*ONG (EUNG 0ARK
#/.4%.43
./-%.#,!452%3 ) ).42/$5#4)/.
)) .5-%2)#!, !.!,93)3 ))) %80%2)-%.4
)6 2%35,43 !.$ $)3#533)/.3 6 #/.#,53)/.3
2%&%2%.#%3
!"342!#4
! STUDY ON THE OPERATION OF A HEAT PIPE WITH TWO HEAT SOURCES HAS BEEN PERFORMED TO OP TIMIZE THE HEAT DISTRIBUTION OF SATELLITE EQUIP MENT ! NUMERICAL MODELING IS USED TO PRE DICT THE TEMPERATURE PRO`LE FOR THE HEAT PIPE ASSUMING CYLINDRICAL TWO DIMENSIONAL LAMINAR aOW FOR THE VAPOR AND THE CONDUCTION HEAT TRANSFER FOR THE WALL AND WICK !N EXPER IMENTAL STUDY USING THE COPPER WATER HEAT PIPE WITH THE LENGTH OF M HAS BEEN PER FORMED TO EVALUATE THE NUMERICAL MODEL AND TO COMPARE THE TEMPERATURE DISTRIBUTION AT THE OUTER WALL FOR THE NON UNIFORM HEAT DIS TRIBUTION 4HE RESULTS ON TEMPERATURE PRO
`LES FOR THE HEAT INPUT RANGE FROM 7 TO
7 ON EACH HEATER ARE PRESENTED !LSO THE CORRELATION BETWEEN THE HEAT INPUT AND THE TEMPERATURE INCREASE IS PRESENTED FOR THE OP TIMUM DISTRIBUTION ON TWO HEATERS 4HE RESULT SHOWS THAT THE OUTER WALL TEMPERATURE CAN BE CONTROLLED BY REDISTRIBUTION OF HEAT SOURCES )T IS ALSO CONCLUDED THAT THE HEAT SOURCE CLOSER TO THE CONDENSER CAN CARRY MORE HEAT WHILE MAINTAINING LOWER TEMPERATURES AT THE OUTER WALL
*ONG (EUNG 0ARK %42) *OURNAL VOLUME NUMBER *ULY
./-%.#,!452%3
! AREA M
CP SPECI`C HEAT AT CONSTANT PRESSURE *KG + HFG LATENT HEAT OF EVAPORATION *KG
K THERMAL CONDUCTIVITY 7M + , TOTAL LENGTH OF HEAT PIPE M
Mq MASS aUX AT THE LIQUID VAPOR INTERFACE KGM S
P VAPOR PRESSURE .M PO REFERENCE PRESSURE .M Q HEAT aUX 7M
1 HEAT INPUT 7 R RADIAL COORDINATE M 2 GAS CONSTANT
2O OUTER PIPE WALL RADIUS M 2V VAPOR REGION RADIUS M 2W WICK WALL INTERFACE RADIUS M 4 TEMPERATURE +
4O REFERENCE TEMPERATURE + V RADIAL VELOCITY MS W AXIAL VELOCITY MS Z AXIAL COORDINATE M
POROSITY
} DYNAMIC VISCOSITY OF THE VAPOR KGM S
DENSITY KGM
3UBSCRIPTS A ADIABATIC C CONDENSER EF F E_ECTIVE ( (EATER ( (EATER
L LIQUIDWORKING aUID LW LIQUID SATURATED WICK R RADIAL DIRECTION
S WICK SOLID MATERIAL OR SATURATION V VAPOR
W WALL
) ).42/$5#4)/.
$UE TO THE HEAT TRANSPORT BY EVAPORA TION AND CONDENSATION OF THE WORKING aUID A HEAT PIPE IS AN E_ECTIVE BUT SIMPLE DE VICE WHICH HAS A VERY HIGH THERMAL CON DUCTANCE 3INCE S THESE DEVICES HAVE BEEN DEVELOPED TESTED AND PUT INTO OPERA TION IN VARIOUS TYPES SPECIALLY FOR SPACE AP PLICATIONS 7ITH THESE DEVELOPMENTS HEAT PIPES ARE USED IN MANY ENGINEERING `ELDS NOWADAYS ;= ;=
!CCORDING TO THE CHANGE OF THE WORKING CONDITIONS AND APPLICATIONS THE HEAT PIPE OPERATION WITH MULTIPLE HEAT SOURCES HAS BEEN ENCOUNTERED FREQUENTLY RATHER THAN THE CONVENTIONAL HEAT PIPE OPERATION WITH A SINGLE HEAT SOURCE AND SINK 4HIS OPERA TION WITH MULTIPLE HEAT SOURCES CAN BE OB SERVED IN SPACE APPLICATION WHERE THE HEAT PIPES ARE THE MAJOR DEVICES FOR THE THER MAL CONTROL OF SATELLITE EQUIPMENT 7HEN THE HEAT DISSIPATING EQUIPMENT SUCH AS HIGH POWER AMPLI`ER FREQUENCY CONVERTER AND POWER SUPPLY ARE MOUNTED IN SERIES ON A HEAT PIPE EMBEDDED IN A HONEYCOMB PANEL THESE EQUIPMENT ACT AS MULTIPLE HEAT SOURCES ON THE HEAT PIPE )T IS OBVIOUS THAT A CONVENTIONAL ANALYTICAL METHODOLOGY DE VELOPED FOR A HEAT PIPE WITH A SINGLE HEAT SOURCE CANNOT BE APPLIED TO THE OPERATION WITH MULTIPLE HEAT SOURCES OF NON UNIFORM HEAT DISTRIBUTIONS
'ERNERT ;= ATTEMPTED THE ANALYSIS OF HEAT PIPE WITH MULTIPLE HEAT SOURCES WITH THE USE OF SUPERPOSITION AND THE EXTEN TION OF THE EXISTING THEORIES FOR THE SINGLE EVAPORATOR HEAT PIPE (E ALSO CONDUCTED
%42) *OURNAL VOLUME NUMBER *ULY *ONG (EUNG 0ARK
AN EXPERIMENT USING A M LONG COPPER WATER HEAT PIPE WITH THE TOTAL HEAT INPUT OF 7 ON `VE HEATERS )N THE STUDY THE PERFORMANCE OF THE HEAT PIPE SUCH AS THE TEMPERATURE PRO`LES AND DRYOUT CONDI TION WAS PRESENTED &AGHRI AND "UCHKO ;=
PERFORMED AN EXPERIMENTAL AND NUMERICAL STUDY OF LOW TEMPERATURE HEAT PIPE WITH MULTIPLE HEAT SOURCES 4HEY SUGGESTED A COMPLETE MATHEMATICAL MODEL TO PREDICT THE PERFORMANCE OF THE HEAT PIPE INCLUD ING THE CONJUGATE HEAT TRANSFER AND THE EF FECT OF LIQUID aOW IN A WICK )N ADDITION THE EXPERIMENTAL TESTING USING THE M LONG COPPER WATER HEAT PIPE WITH THE HEAT INPUT RANGE FROM 7 TO 7 ON FOUR HEATERS WERE PERFORMED FOR THE OPTIMIZATION OF THE HEAT DISTRIBUTION )N SPITE OF THE E_ORT OF THESE STUDIES DESCRIBED ABOVE THE CORRELA TION BETWEEN THE HEAT INPUT AND THE TEM PERATURE INCREASE FOR THE OPTIMUM DISTRI BUTION OF HEAT SOURCES WERE NOT AVAILABLE IN OPEN LITERATURE
&IG (EAT PIPE MODEL AND COORDINATE SYSTEM
4HE OBJECTIVE OF THE PRESENT STUDY IS TO INVESTIGATE THE E_ECT OF THE HEAT DISTRIBU TION ON THE HEAT PIPE PERFORMANCE FOR THE OPTIMUM PLACEMENT OF SATELLITE EQUIPMENT
4HE TEMPERATURE PREDICTION BY THE NUMERI CAL MODELING AS WELL AS THE EXPERIMENT WITH A COPPER WATER HEAT PIPE HAVE BEEN PER FORMED 4HE RESULTS ON THE TEMPERATURE PRO`LES FOR THE HEAT INPUT RANGE OF 7 TO
7 ON EACH HEATER ARE PRESENTED !LSO THE CORRELATIONS BETWEEN THE HEAT INPUT AND TEMPERATURE INCREASE ARE PRESENTED FOR THE OPTIMUM HEAT DISTRIBUTION ON TWO HEATERS
)) .5-%2)#!, !.!,93)3
-ATHEMATICAL -ODELING
&IG SHOWS THE SIMPLI`ED MODEL AND THE COORDINATE SYSTEM OF THE HEAT PIPE USED IN THE PRESENT STUDY WHICH IS A CONVEN TIONAL ONE WITH TWO HEATERS 4HESE HEATERS CAN BE CONSIDERED AS EQUIVALENT SATELLITE EQUIPMENT WHICH DISSIPATE HEAT 4HE HEAT PIPE CON`GURATION SHOWN IN &IG CAN BE DIVIDED INTO THREE REGIONS NAMELY VAPOR SPACE WICK AND WALL REGIONS 4HE WORK ING aUID IS SATURATED WITH WICK IN LIQUID PHASE 4HE POWER APPLIED TO THE HEATERS CAUSES THE LIQUID IN THE WICK TO VAPORIZE
4HE VAPOR aOWS TO THE CONDENSER SECTION AND RELEASES THE HEAT AS IT CONDENSES 4HE RELEASED HEAT IS REJECTED THROUGH THE WALL TO THE AMBIENT 4HE CONDENSED WORKING aUID IN THE WICK RETURNS TO (EATER AND (EATER
SECTIONS BY THE CAPILLARY FORCE OF THE WICK STRUCTURE
Heat flow Adiabatic section
Condenser Heater 2
Lc
La2
LH2
La1
LH1
Rv
Rw
Ro
Heater 1
Vapor Space
Wall Wick z,w
r,v 0
*ONG (EUNG 0ARK %42) *OURNAL VOLUME NUMBER *ULY
'OVERNING %QUATIONS
4HE SEVERAL NUMERICAL METHODOLOGIES FOR A HEAT PIPE WITH MULTIPLE HEAT SOURCES HAVE BEEN DEVELOPED ;= ;= !MONG THEM THE MODELING FROM #HEN AND &AGHRI ;=
IS ADOPTED FOR THE PRESENT STUDY WHICH SHOWED A GOOD AGREE MENT FOR BOTH HIGH TEMPERATURE AND LOW TEM PERATURE HEAT PIPES 4HEREFORE THE GOVERNING EQUATIONS FOR THIS MODEL CAN BE DESCRIBED IN THREE DI_ERENT RADIAL REGIONS 4HESE EQUATIONS SHOULD BE SOLVED AS A CONJUGATE PROBLEM DUE TO THE HEAT AND MASS aOW ALONG THE INTERFACE
! 6APOR 3PACE
"OWMAN AND (ITCHCOCK ;= REPORTED THE VAPOR aOW WAS ALWAYS LAMINAR IN THE CON DENSER WHILE IT MIGHT BE TURBULENT WHEN THE 2EYNOLDS NUMBER IS GREATER THAN
!CCORDING TO $UNN AND 2EAY ;= THE COM PRESSIBILITY OF VAPOR COULD NOT BE IGNORED WHEN THE -ACH NUMBER IS GREATER THAN
3INCE THE 2EYNOLDS NUMBER AND THE -ACH NUMBER IN THE PRESENT STUDY ARE APPROXI MATELY AND RESPECTIVELY THE VAPOR IS ASSUMED TO BE AN INCOMPRESSIBLE LAMINAR aOW #ONSEQUENTLY THE GOVERNING EQUA TIONS FOR THE TWO DIMENSIONAL INCOMPRESS IBLE LAMINAR aOW WITH CONSTANT VISCOSITY IN THE CYLINDRICAL R Z COORDINATE ARE GIVEN AS FOLLOWS ;=
R RRV
ZW
R RRV
ZVW
p P R }
f R
d R RRV
e
V Z g
R RRVW
ZW
p P Z }
f R
d R RRW
e
W Z
g
CP
d V 4
R W 4 Z
e
K f
R R d
R 4 R
e
4 Z g
WHERE P } CP 4 AND K ARE DENSITY PRESSURE VISCOSITY SPECI`C HEAT TEMPERA TURE AND THERMAL CONDUCTIVITY OF THE WORK ING aUID IN THE VAPOR PHASE
" 7ICK
&AGHRI AND "UCHKO ;= PERFORMED AN EX PERIMENTAL AND NUMERICAL ANALYSIS ON A
M LONG COPPER WATER HEAT PIPE WITH THE TO TAL HEAT INPUT RANGE OF 7 TO 7 )T WAS CONCLUDED THAT THE E_ECT OF THE LIQUID aOW IN THE WICK COULD NOT BE IGNORED IN A LOW TEMPERATURE HEAT PIPE (OWEVER ONE DIMENSIONAL CALCULATION OF THE LIQUID aOW IN THE WICK FOR THE PRESENT HEAT PIPE WITH A M IN LENGTH AND HEAT INPUT RANGE BETWEEN 7 TO 7 SHOWED THAT THE AXIAL AVERAGE VELOCITY IN THE WICK WAS IN THE ORDER OF p MS WHICH IS RELATIVELY LOW ENOUGH TO IGNORE THE IMPACT OF THE LIQ UID aOW ON THE TEMPERATURE DISTRIBUTION
4HIS DOES NOT MEAN THAT THE aOW IN THE WICK IS NOT IMPORTANT (OWEVER IN ORDER TO SAVE THE E_ORT OF CALCULATION THE WICK aOW IS IGNORED IN THE PRESENT STUDY FOR CON VENIENCE )N ADDITION SINCE THE CALCULA TION OF CAPILLARY LIMIT SUGGESTED BY $UNN AND 2EAY ;= WAS ABOUT 7 USED FOR THE PRESENT STUDY THE WICK STRUCTURE IS AS SUMED TO HAVE A SUbCIENT CAPILLARY FORCE TO AVOID THE OPERATIONAL FAILURE "ASED ON
%42) *OURNAL VOLUME NUMBER *ULY *ONG (EUNG 0ARK
THESE ASSUMPTIONS THE WICK REGION IS MOD ELED AS PURE CONDUCTION WITH AN E_ECTIVE THERMAL CONDUCTIVITY 4HE CORRESPONDING GOVERNING EQUATION IS
KEF F f
R R d
R 4LW R
e
4LW Z
g
WHERE THE E_ECTIVE THERMAL CONDUCTIVITY KEF F IS CALCULATED FROM BASED ON THE METAL SCREEN WICK ;= ;=
KEF F KL;KL KS p p KLp KS =
;KL KS p KLp KS =
WHERE IS THE POROSITY OF THE WICK AND SUBSCRIPTS L AND S INDICATE THE WORKING aUID IN THE WICK IN LIQUID PHASE AND THE SOLID MATERIAL OF THE SCREEN MESH RESPECTIVELY
# 7ALL
4HE HEAT TRANSFER THROUGH THE HEAT PIPE WALL IS PURELY BY CONDUCTION 4HE CORRE SPONDING GOVERNING EQUATION IS
KW
f R R
d R 4W
R e
4W
Z g
"OUNDARY #ONDITIONS
"OUNDARY CONDITIONS ARE NEEDED AT BOTH ENDS OF THE HEAT PIPE AT THE CENTERLINE AT THE VAPOR WICK INTERFACE AT THE WALL WICK INTERFACE AND AT THE OUTER WALL !T BOTH ENDS OF THE HEAT PIPE THE NO SLIP CONDITION FOR THE VELOCITY AND THE ADIABATIC CONDITION FOR THE TEMPERATURE ARE APPLIED
V W 4
Z AT Z ,
!T THE CENTERLINE THE SYMMETRY CONDI TIONS ARE APPLIED
W
R V 4
R AT R
!T THE VAPOR WICK INTERFACE THE TEM PERATURE IS ASSUMED TO BE AT SATURATION CORRESPONDING TO THE INTERFACE PRESSURE DURING HEAT PIPE OPERATION 4HUS THE IN TERFACE TEMPERATURE IS CALCULATED USING THE
#LAUSIUS #LAPEYRON EQUATION ;= GIVEN BY
4
4O
p d 2
HFG e
LN dPV
PO
e AT R 2V
WHERE 2 HF G PO AND 4OARE GAS CONSTANT LATENT HEAT OF THE WORKING aUID REFERENCE SATURATION PRESSURE AND REFERENCE TEMPER ATURE RESPECTIVELY &OR THE VELOCITY THE BOUNDARY CONDITIONS ARE DE`NED BASED ON THE RATE OF EVAPORATION AND CONDENSATION OF THE WORKING aUID 4HE RADIAL AND THE AX IAL VELOCITIES ALONG THE VAPOR WICK INTERFACE ARE GIVEN BY
VI Mq
Q
HF G
HFG d
KV 4V
R p KEFF 4LW R
e
W AT R 2V
WHERE M IS THE MASS aUX AT THE VAPOR q WICK INTERFACE !CCORDING TO THE COOR DINATE SYSTEM SHOWN IN &IG INTERFACE VELOCITY VI IS NEGATIVE IN THE HEATER SEC TIONBLOWING AND IS POSI TIVE IN THE CON DENSER SECTIONSUCTION TO BALANCE THE MASS aOW
*ONG (EUNG 0ARK %42) *OURNAL VOLUME NUMBER *ULY
!T THE WICK AND WALL INTERFACE THE BOUNDARY CONDITION IS
KW
4W R KEFF
4LW
R AT R 2W
!T THE OUTER WALL A CONSTANT HEAT aUX BOUNDARY IS USED
KW
4W
R u1
! AT R 2O
4HE HEAT aUX IN ;= IS CONSTANT AND POS ITIVE IN THE HEATER SECTIONS ZERO IN ALL THE ADIABATIC SECTIONS AND NEGATIVE IN CON DENSER SECTION BASED ON THE UNIFORM DISTRI BUTION OF TOTAL HEAT THROUGH THE HEATERS
.UMERICAL -ETHODOLOGY
4HE CONJUGATE HEAT TRANSFER PROBLEM SHOULD BE SOLVED NOT ONLY BECAUSE THREE RADIAL REGIONS WITH DI_ERENT PROPERTIES ARE SOLVED SIMULTANEOUSLY BUT ALSO BECAUSE THERE IS HEAT TRANSFER THROUGH THE INTER FACES OF THE REGIONS 4HE 0(/%.)#3 COM PUTATIONAL CODE BY 2OSTEN AND 3PALDING
;= WHICH EMPLOYED THE `NITE DI_ERENCE METHOD WAS USED TO SOLVE THE GOVERNING EQUATIONS WITH THE ABOVE BOUNDARY CON DITIONS 4HE PRESSURE AT THE VAPOR WICK INTERFACE AT THE END OF THE CONDENSER WAS TAKEN AS A `XED DATUM PRESSURE FOR THE CAL CULATION 4HE PHASE CHANGE AT THE VAPOR WICK INTERFACE IS SIMPLY TREATED AS A SOURCE TERM IN THE ENERGY EQUATION 4HE LATENT HEAT IS ADDED AS A POSITIVE VALUE WHERE THE CONDENSATION OCCURS AND AS A NEGATIVE VALUE WHERE THE EVAPORATION OCCURS
4HE GRID CONSISTS OF RADIAL BY AX IAL ! CONVERGED SOLUTION IS DE`NED AS THE
CONDITION WHEN THE DI_ERENCE FOR THE AB SOLUTE VALUES OF DEPENDENT VARIABLES IS LESS THAN BETWEEN TWO SUCCESSIVE ITERA TIONS AND WHEN THE SUM OF THE ABSOLUTE VALUES OF RESIDUALS IS LESS THAN p ! FALSE TIME STEP RELAXATION ;= IS USED TO SOLVE V AND W MOMENTUM EQUATIONS
))) %80%2)-%.4
"ECAUSE THE MAJOR OBJECTIVE OF THIS STUDY WAS TO INVESTIGATE THE E_ECT OF THE HEAT DISTRIBUTION ON THE HEAT PIPE PERFOR MANCE IT WAS DECIDED TO USE A CONVENTIONAL COMMERCIAL HEAT PIPE FOR AN EXPERIMENT IN STEAD OF MAKING A NEW PIPE 4HE HEAT PIPE SELECTED FOR THE EXPERIMENT WAS A COPPER WATER HEAT PIPE4HERMACORE )NC (0 WHICH WAS RATED TO OPERATE AT A TEMPER ATURE RANGE OF b# TO b# 4ABLE SHOWS THE DETAILS OF THE HEAT PIPE 4HE DI MENSION IS M IN LENGTH AND M IN DIAMETER 4HE WALL AND THE WICK THICKNESS ARE M EACH ! SIMPLE CIRCUMFERENTIAL SCREEN WICK CONSISTING OF THREE LAYERS OF
MESH COPPER SCREEN WIRE IS INSTALLED TO PRO VIDE THE WORKING aUID RETURN BY CAPILLARY FORCE
4HE EXPERIMENTAL APPARATUS IS SHOWN IN
&IG ! TOTAL OF TWELVE TYPE 4 TYPE THER MOCOUPLES WITH AN ACCURACY OF u b# WERE ATTACHED ON THE OUTER WALL WITH A THERMAL BOND 4WO RUBBER COATED aEXIBLE HEATERS EQUIVALENT TO SATELLITE EQUIPMENT WERE WRAPPED AROUND THE PIPE WALL 4HESE HEATERS WERE INDEPENDENTLY CONTROLLED BY A POWER SUPPLY 4HE LENGTH OF HEATERS ,(
%42) *OURNAL VOLUME NUMBER *ULY *ONG (EUNG 0ARK
4ABLE 3UMMARY OF EXPERIMENTAL HEAT PIPE
)TEM -ATERIAL AND 3IZE
(EAT PIPE WALL #OPPER
7ICK MATERIAL #OPPER
%ND CAP MATERIAL #OPPER 7ORKING &LUID $ISTILLED WATER
,ENGTH MM
$IAMETER MM
$IAMETER OF VAPOR SPACE MM 3CREEN MESH NUMBER LAYERS ,ENGTH OF HEATER MM EACH ,ENGTH OF ADIABATIC SECTION MM EACH ,ENGTH OF CONDENSER MM
&IG %XPERIMENTAL APPARATUS
AND ,( WAS MM EACH 4HE LENGTH OF ADIABATIC SECTIONS ,AAND ,AWAS MM BETWEEN HEATERS AND BETWEEN (EATER AND CONDENSER SECTION 4HE ENTIRE HEAT PIPE EX CEPT THE CONDENSER SECTION WAS WRAPPED BY
MM THICK INSULATION MATERIALS COMPOSED OF `BER GLASS AND STYRO FORM 4HREE MORE
THERMOCOUPLES WERE PLACED ON THE OUTER SURFACE OF THE INSULATION MATERIAL TO MEA SURE THE HEAT LOSS TO THE SURROUNDINGS 4HE NET HEAT INPUT TO THE HEAT PIPE WAS DE`NED AS THE DI_ERENCE BETWEEN THE POWER INPUT FROM POWER SUPPLY AND THE LOSS THROUGH THE SURFACE OF THE INSULATION MATERIAL 4HE LOSS WAS ABOUT u IN THE PRESENT APPA RATUS )N THE CONDENSER SECTION THE COOL ING WATER WAS CIRCULATING IN A WATER JACKET MADE OF GLASS TO REMOVE THE HEAT FROM THE CONDENSER #OOLING WATER WAS SUPPLIED BY A PUMP CONNECTED TO THE CONSTANT TEMPER ATURE RESERVOIR WHICH WAS EQUIPPED WITH A PRE HEATER TO CONTROL THE WATER TEMPERA TURE WITH AN ACCURACY OF u b# 4HIS ASSEMBLY WAS MOUNTED HORIZONTALLY ON A WORK BENCH 4HE SIGNALS FROM THE THERMO COUPLES WERE READ BY A THERMOCOUPLE DATA LOGGER
)6 2%35,43 !.$
$)3#533)/.3
!T `RST THE HEAT PIPE WAS OPERATED WITH 7 HEAT INPUT AT (EATER ONLY IN ORDER TO ENSURE THE PROPER OPERATION AND TO ESTABLISH THE TEMPERATURE SETTING OF COOL ING WATER &IGURE SHOWS THE WALL TEMPER ATURE PRO`LES AS A FUNCTION OF THE COOLING WATER TEMPERATURE AT (EATER Z M ADIABATICZ M AND CONDENSER SEC TIONZ M !S CAN BE SEEN IN THIS
`GURE AS THE TEMPERATURE OF THE COOLING WATER INCREASES THE TEMPERATURES AT THE THREE LOCATIONS INCREASES WITH A SAME RATE
Water flow
Thermocouples
PC and
Data Logger Insulation materials Flow meter Reservoir
(constant temperature)
Heat pipe
Table Power
Supply
Water jacket Heater 1 Heater 2
Water
*ONG (EUNG 0ARK %42) *OURNAL VOLUME NUMBER *ULY
&IG 7ALL TEMPERATURE PRO`LE WITH COOLING WATER TEMPERATURE
4ABLE 4EST MATRIX
#ASE (EATER (EATER 4OTAL
7 7 7
7 7 7
7 7 7
7 7 7
7 7 7
7 7 7
7 7 7
7 7 7
7 7 7
4HIS MEANS THE HEAT PIPE UNDER TEST IS OP ERATING NORMALLY IN THE RANGE OF b# TO
b# OF COOLING WATER "ASED ON THIS RE SULT THE TEMPERATURE OF COOLING WATER WAS MAINTAINED AT b# THROUGHOUT THE EXPER IMENT
4ABLE SHOWS THE NINE CASES OF EXPERI MENT IN THE PRESENT STUDY TO OPTIMIZE THE HEAT DISTRIBUTION ON TWO HEATERS 4HE HEAT
INPUT RANGE WAS FROM 7 TO 7 AT EACH HEATER CONSEQUENTLY TOTAL HEAT IMPOSED ON THE HEAT PIPE WAS A MINIMUM OF 7 AND A MAXIMUM OF 7 )T WAS OBSERVED THAT THERE WAS NO OPERATING FAILURES SUCH AS A DRY OUT IN THIS HEAT INPUT RANGE
7ALL TEMPERATURE PRO`LES ALONG THE AX IAL DIRECTION FOR #ASE #ASE AND #ASE
ARE SHOWN IN &IGS RESPECTIVELY 4HE TEMPERA TURE PRO`LES PREDICTED BY THE NU MERICAL MODELING ARE ALSO SHOWN IN THE SAME `GURES WHICH SHOW A RELATIVELY GOOD AGREEMENT WITH EXPERIMENTAL DATA EXCEPT TWO LOCATIONS THOSE ARE AT THE END OF (EATER Z M AND AT THE ADIA BATIC SECTION BETWEEN HEATERSZ M 4HE DEVIATION AT THESE TWO LOCATIONS WAS ABOUT COMPARED TO THE DI_ERENCE BETWEEN THE HIGHEST TEMPERATURE AT THE HEATER AND THE LOWEST TEMPERATURE AT THE CONDENSER SECTION )T IS INTERESTING TO NOTE THAT THE TEMPERATURE AT (EATER IS AL WAYS HIGHER THAN THE PREDICTED VALUE WHILE IT IS ALWAYS LOWER AT THE ADIABATIC SEC TION 4HIS IMPLIES THAT THE HEAT PIPE UNDER THE PRESENT EXPERIMENT HAS A LOWER PERFOR MANCE THAN THE MODELED ONE )N GENERAL IT IS KNOWN THAT THE HEAT PIPE PERFORMANCE IS WORSE THAN THOSE PREDICTED BY THEORETICAL MODEL ;= 4HE REASON FOR THIS IS BECAUSE THE WICK STRUCTURE SPECIALLY MULTI LAYERED METAL SCREEN MESH IS NOT COMPLETELY AT TACHED TO THE WALL SURFACE AND TO EACH LAYER SO THAT THE RETURN OF WORKING aUID MAY NOT BE UNIFORM 4HE TEMPERATURE DEVIATION IN THE PRESENT STUDY SEEMS TO BE RESULTED FROM THE SIMILAR REASON
Twater[7C]
70 60 50 40
30 80
0 30 60 90 120
Tw[7C]
QH1=38W
Condenser (z = 0.39 m) Adiabatic (z = 0.23 m) Heater 1 (z = 0.07 m)
%42) *OURNAL VOLUME NUMBER *ULY *ONG (EUNG 0ARK
&IG 7ALL TEMPERATURE PRO`LE WITH AXIAL LOCATION FOR #ASE
&IG 7ALL TEMPERATURE PRO`LE WITH AXIAL LOCATION FOR #ASE
!S SHOWN IN &IGS AND IT SEEMS TO BE NATURAL THAT THE TEMPERATURE IS HIGHER AT (EATER THAN IN (EATER DUE TO THE HIGHER OR SAME AMOUNT OF HEAT INPUT TO THE (EATER COMPARED TO THAT FOR (EATER
(OWEVER IT IS NOTICEABLE THAT THE TEMPERA TURE AT (EATER IS STILL HIGHER THAN THAT AT (EATER IN SPITE OF THE HIGHER HEAT INPUT AT
&IG 7ALL TEMPERATURE PRO`LE WITH AXIAL LOCATION FOR #ASE
(EATER AS SHOWN IN &IG !S &AGHRI AND
"UCHKO ;= CONCLUDED IN THEIR EXPERIMENT THE HIGHER HEAT LOAD CAN BE CARRIED IN THE EVAPORATOR LOCATED CLOSER TO THE CONDENSER SECTION DUE TO THE BETTER RETURN OF WORK ING aUID AS WELL AS THE AXIAL CONDUCTION THROUGH THE WALL AND WICK 4HIS ARGUMENT CAN BE APPLICABLE TO THE PRESENT STUDY
4O EVALUATE THE THERMAL PERFORMANCE OF THE COPPER WATER HEAT PIPE USED IN THE PRESENT STUDY IT WOULD BE VALUABLE TO COM PARE THE WALL TEMPERATURES CORRESPONDING TO THE HEAT INPUT 4HE EXPERIMENTAL WALL TEMPERATURE PRO`LES FOR THE TOTAL HEAT IN PUT OF 7#ASE #ASE AND #ASE RESPECTIVELY ARE SHOWN TOGETHER IN &IG
)N THIS `GURE 1( MEANS THE HEAT INPUT AT (EATER AND 1( AT (EATER #ON SIDERING THE SAME AMOUNT OF THE TOTAL HEAT INPUT IT IS INTERESTING THAT THE WALL TEM PERATURES APPEAR DI_ERENTLY ACCORDING TO THE HEAT DISTRIBUTION 4HE MAXIMUM TEM PERATURE DI_ERENCE BETWEEN THE HEATER AND
Tw[7C]
100 90 80 70 60 50
30 40
20
29 W 29 W
z[m]
0.45 0.3
0.15 0
Numerical Experiment
Condenser
Numerical Experiment
38 W 29 W
Condenser
z[m]
0.45 0.3
0.15 0
Tw[7C]
110 100 90 80 70 60
40 50
30
Numerical Experiment
38 W 47 W
Condenser
z[m]
0.45 0.3
0.15 0
Tw[7C]
110 100 90 80 70 60
40 50
30
*ONG (EUNG 0ARK %42) *OURNAL VOLUME NUMBER *ULY
THE CONDENSER SECTION WAS OBSERVED IN #ASE
7 AT (EATER AND 7 AT (EATER WHILE THE MINIMUM TEMPERATURE DI_ERENCE WAS OBSERVED IN #ASE 7 AT (EATER
AND 7 AT (EATER 4HIS IMPLIES THAT THE MAXIMUM HEAT TRANSPORT CAPABIL ITY CAN BE INCREASED BY THE OPTIMUM DISTRI BUTION OF THE HEAT INPUT WHILE MAINTAINING THE MAXIMUM ALLOWABLE TEMPERATURE WHICH IS A MAJOR THERMAL PARAMETER IN EQUIPMENT PLACEMENT WITHIN THE DESIRED LIMIT
&IG #OMPARISON OF WALL TEMPERATURES FOR TOTAL HEAT INPUT 7 #ASE #ASE AND #ASE
!MONG THE NINE CASES LISTED IN 4ABLE
THE TEMPERATURE WAS HIGHER AT (EATER
THAN AT (EATER IN #ASE ONLY 4HE TEMPERATURES WERE HIGHER AT (EATER IN ALL OTHER CASES ALTHOUGH THERE WERE TWO MORE CASES WHERE THE AMOUNT OF HEAT INPUT WAS LARGER AT (EATER THAN AT (EATER !GAIN IT SHOULD BE EMPHASIZED THAT THE OPTIMUM HEAT DISTRIBUTION IS IMPORTANT TO MAINTAIN THE OUTER WALL TEMPERATURE WITHIN THE DE SIGNED LIMIT
&IG 4HE RATIO OF TEMPERATURE INCREASE VS THE RA TIO OF HEAT INPUT BETWEEN (EATER AND (EATER
&IG 7ALL TEMPERATURE INCREASE WITH HEAT INPUT
4HE RATIO OF THE TEMPERATURE INCREASE VERSUS THE RATIO OF THE HEAT INPUT BETWEEN (EATER AND (EATER OF THE HEAT PIPE OBTAINED FROM THE PRESENT EXPERIMENT IS SHOWN IN &IG )N THIS `GURE 4( 4(
AND 4# ARE THE MEAN TEMPERATURES AT (EATER (EATER AND CONDENSER RESPEC
Heart 2 Heart 1
Condenser Q H1=47W, QH2=29W (Case 7) Q H1=38W, QH2=38W (Case 5) Q H1=29W, QH2=47W (Case 3)
z[m]
0.15
0 0.3 0.45
Tw[7C]
100 110 120
90 80 70 60 50 40 30
Heart 2 Heart 1
Condenser Q H1=47 W, QH2=29 W (Case 7) Q H1=38 W, QH2=38 W (Case 5) Q H1=29 W, QH2=47 W (Case 3)
z[m]
0.15
0 0.3 0.45
Tw[7C]
100 110 120
90 80 70 60 50 40 30
60
Q[W]
Heater 2 (38 W at Heater 2) Heater 1 (38 W at Heater 2) 110
100
90
80
70
50 60
40 30
20 Tw[7C]
%42) *OURNAL VOLUME NUMBER *ULY *ONG (EUNG 0ARK
TIVELY 4O EXTEND THIS RESULT IT WOULD BE VALUABLE TO FORMULATE THE CORRELATIONS BE TWEEN THE HEAT INPUT RATIO AND MEAN TEM PERATURE INCREASE RATIO 4HE SOLID LINE IN
&IG IS EXPRESSED AS WHICH CAN BE USED TO PREDICT THE MEAN TEMPERATURE DIF FERENCE BETWEEN TWO LOCATIONS BASED ON THE HEAT RATIO IN OTHER CON`GURATION OF A HEAT PIPE
d4(p 4# 4(p 4#
e
d1(
1(
e
4HE INFORMATION ON THE MEAN TEMPERA TURE INCREASE AT THE OUTERWALL WITH RESPECT TO THE HEAT INPUT WOULD BE USEFUL FOR OPTI MUM HEAT DISTRIBUTION &IG SHOWS THE RE SULTS ON THE WALL TEMPERATURE INCREASE WITH HEAT INPUT OBTAINED FROM THE PRESENT STUDY
4HE TREND OF THE TEMPERATURE AT (EATER WITH A `XED HEAT INPUT OF 7 AT (EATER
IS DRAWN WITH A DASHED LINE AND THE TEM PERATURE TREND AT (EATER WITH A `XED HEAT INPUT OF 7 AT (EATER IS DRAWN WITH A SOLID LINE IN THE `GURE )T WAS FOUND THAT
b# INCREASED PER WATT AT (EATER AND
b# INCREASED PER 7ATT AT (EATER
6 #/.#,53)/.3
4HE PERFORMANCE OF A HEAT PIPE WITH TWO HEAT SOURCES HAS BEEN INVESTIGATED FOR THE OPTIMUM PLACEMENT OF SATELLITE EQUIP MENT 4HE PREDICTION OF THE TEMPERATURE PRO`LE FOR THE HEAT PIPE IS PERFORMED BY A NUMERICAL MODELING AND VERI`ED BY THE EX PERIMENT WITH A M COPPER WATER HEAT
PIPE 4HE TEMPERATURE PRO`LES BY THE NU MERICAL MODEL AND THE EXPERIMENT ARE PRE SENTED FOR NINE DI_ERENT HEAT DISTRIBUTIONS ON TWO HEATERS )N ADDITION A CORRELATION FOR THE RATIO OF THE TEMPERATURE INCREASE VERSUS THE RATIO OF THE HEAT INPUT AT TWO HEATERS AS WELL AS RATE OF THE TEMPERATURE INCREASE WITH THE HEAT INPUT ARE PROPOSED FOR THE OPTIMUM PLACEMENT OF HEAT SOURCES FOR THIS PARTICULAR HEAT PIPE 4HE RESULTS SHOW THAT THE TEMPERATURE PRO`LE AT THE OUTER WALL CAN BE CONTROLLED BY THE OPTI MUM DISTRIBUTION OF HEAT SOURCES ,ARGER HEAT CAN BE CARRIED BY LOCATING THE HIGHER HEAT DISSIPATING EQUIPMENT CLOSER TO THE CONDENSER SECTION WHILE MAINTAINING THE MAXIMUM TEMPERATURE CONTROLLED
4HE NUMERICAL METHODOLOGY AND THE CORRELATIONS IN THE PRESENT STUDY CAN BE EASILY EXTENDED TO PREDICT THE PERFORMANCE OF THE HEAT PIPE WITH DI_ERENT THERMAL CON
`GURATIONS
2%&%2%.#%3
;= & $ORAN <(EAT PIPE RESEARCH AND DEVELOPMENT IN THE !MERICAS (EAT 2ECOVERY 3YSTEMS AND
#(0 VOL NO PP
;= 9 ,EE ) 0IORO AND ( * 0ARK <!N EXPERI MENTAL STUDY ON A PLATE TYPE TWO PHASE CLOSED THERMOSYPHON 0APER 3 TH)NTERNATIONAL (EAT 0IPE 3YMPOSIUM 4SUKUBA -AY
;= . * 'ERNERT <!NALYSIS AND PERFORMANCE EVALUATION OF HEAT PIPES WITH MULTIPLE HEAT SOURCES !)!!!3-% TH *OINT 4HERMO PHYSICS AND (EAT 4RANSFER #ONFERENCE !)!!
*ONG (EUNG 0ARK %42) *OURNAL VOLUME NUMBER *ULY
;= ! &AGHRI AND - "UCHKO <%XPERIMENTAL AND NUMERICAL ANALYSIS OF LOW TEMPERATURE HEAT PIPES WITH MULTIPLE HEAT SOURCES *OURNAL OF (EAT 4RANSFER VOL PP
;= * ( *ANG ! &AGHRI 7 3 #HANG AND % 4
-AHEFKEY <-ATHEMATICAL MODELING AND ANALY SIS OF HEAT PIPE START UP FROM THE FROZEN STATE
*OURNAL OF (EAT 4RANSFER VOL PP
;= 9 #AO AND ! &AGHRI <4RANSIENT TWO DIMENSIONAL COMPRESSIBLE ANALYSIS FOR HIGH TEM PERATURE HEAT PIPES WITH A PULSED HEAT INPUT .UMERICAL (EAT 4RANSFER 0ART ! VOL PP
;= * ( 0ARK AND * ( ,EE <! NUMERICAL STUDY ON THE HEAT PIPE WITH SWITCHED HEAT SOURCE AND SINK FOR SPACE APPLICATION !3-% (4$ 6OL
.ATIONAL (EAT 4RANSFER #ONFERENCE VOL PP
;= - - #HEN AND ! &AGHRI <!N ANALYSIS OF THE VAPOR aOW AND THE HEAT CONDUCTION THROUGH THE LIQUID WICK AND PIPE WALL IN A HEAT PIPE WITH SINGLE OR MULTIPLE HEAT SOURCE )NT *OURNAL OF (EAT -ASS 4RANSFER VOL NO PP
;= 7 * "OWMAN AND * (ITCHCOCK <4RANSIENT COMPRESSIBLE HEAT PIPE VAPOR DYNAMICS 0ROC
OF TH !3-% .ATIONAL (EAT 4RANSFER #ONFER ENCE VOL PP
;= 0 $ $UNN AND $ ! 2EAY (EAT 0IPES TH
%D .EW 9ORK 0ERGAMON PP
;= % . 'ANIC * 0 (ARTNETT AND 7 -
2OHSENOW <"ASIC CONCEPTS OF HEAT TRANSFER IN (ANDBOOK OF (EAT 4RANSFER &UNDAMENTALS 2OHSENOW ET AL %DS .EW 9ORK -C'RAW (ILL
;= ! &AGHRI (EAT 0IPE 3CIENCE AND 4ECHNOLOGY
4AYLOR &RANCIS PP PP
;= ( ) 2OSTEN AND $ " 3PALDING 0HOEN ICS 4RAINING #OURSE .OTES #(!- 42
#(!-
;= * ( "OO AND 3 ( *IN <$EVELOPMENT OF A COMPUTER CODE FOR THE PERFORMANCE ANALYSIS AND DESIGN OF LOW TEMPERATURE HEAT PIPES HAVING SCREEN WICK 4RANS OF +3-% VOL NO PP
*ONG (EUNG 0ARK RECEIVED HIS "3 -3 AND 0H$
DEGREES IN -ECHANICAL %NGI NEERING FROM (ANYANG 5NI VERSITY IN IN AND IN RESPECTIVELY (E HAD WORKED ON THE THERMAL DESIGN MECHANICAL DESIGN AND EVALUATION OF THE ELEC TRONIC SYSTEM SUCH AS 4$8 4)#/- AND 3-8
(E JOINED THE +OREASAT 0ROGRAM FOR TWO AND HALF YEARS AT --3-ATRA -ARCONI 3PACE 5+ AND ,-!3,OCKHEED -ARTIN !STRO 3PACE 53! (E IS CURRENTLY WORKING ON THE MECHANICAL AND THERMAL DESIGN OF THE TRANSPONDER SYSTEM FOR THE COMMUNI CATION SATELLITE
