1、Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-1. Report No. 2. Government Accession No. 3. Recipients Catalog No.NASA CR-20184. Title and Subtitle“The
2、ory and Design of Variable Conductance Heat Pipes“7. Author(s)B.D. Marcus9. Performing Organization Name and AddressTRW Systems GroupOne Space ParkRedondo Beach, Ca.12. Sponsoring Agency Name and AddressNational Aeronautics variable conductance heat pipes;capillary pumping, heat transfer, temperatur
3、econtrol, spacecraft thermal control, change-of-Phase heat transfer18. Distribution StatementUNCLASSIFIED-UNLIMITED19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No. of PagesUNCLASSIFIED UNCLASSIFIED 23822. Price*3.00For sale by the National Technical Information Ser
4、vice, Springfield, Virginia 22151Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-FOREWORDThe work described in this report was performed under NASAcontract NAS 2-5503, “Design_ Fabrication and Testing of aVariable Conductance Constant Temperature Hea
5、t Pipe“. Thecontract is administered by Ames Research Center, MoffettField, California, with Mr. J. P. Kirkpatrick serving asTechnical Monitor.The program is being conducted by TRW Systems Group of TRW,Inc., Redondo Beach, California_ with Dr. Bruce D. Marcusserving as Program Manager and Principal
6、Investigator. Majorcontributors to the effort include Mr. G. L. Fleischman andProfessor D. K. Edwards.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-1.02.03.04.0TABLEOFCONTENTSINTRODUCTION lLITERATUREREVIEW. 3CONVENTIONAL HEAT PIPE THEORY . 43.1 Hyd
7、rodynamics . 43,l.l Capillary Head . 43,1.2 Liquid Pressure Drop 83.1.3 Vapor Pressure Drop lO3.1.4 Body Force Head II3.1.5 Integrating the Flow Equations . 153.1.6 Capillary Pumping Limit 183.1.7 Entrainment Limit . 233.1.8 Sonic Limit 283.2 Heat Transfer . 293.2.1 Evaporator Heat Transfer -Boiling
8、 in the Wick . 303.2.2 Condenser Heat Transfer 36CONVENTIONAL HEAT PIPE DESIGN . 374.1 Wick Design 374.1ol Effective Pore Radii of Various Wicks 384.1.2 Permeability of Various Wicks . 464.1.3 Wick Optimization . 514.1.4 Composite Wicks 604.2 Fluid Inventory 734o2.1 Fluid Inventory Variations . 754.
9、3 Excess Fluid Reservoirs 804.4 Working Fluid . 824.4.1 Operating Temperature Range 824.42 Heat Transfer Requirements . 834.4.3 Expected Body-Force Field . 834.4.4 Tolerance of Wick Structure to Boiling 854.4.5 Conventional or Variable ConductanceHeat Pipe 85Provided by IHSNot for ResaleNo reproduct
10、ion or networking permitted without license from IHS-,-,-Table of Contents(Contd)4.4.6 Special Requirements. 884.4.7 Materials Compatibility andStability . 884.4.8 Summary 955.0 HEATPIPECONTROLTECHNIQUES 975.1 Liquid FlowControl . 985.2 VaporFlowControl 995,3 CondenserFloodingUsingNon-CondensibleGas
11、. 995.4 CondenserFloodingUsingExcessWorkingFluid 996.0 VARIABLECONDUCTANCETHROUGHTHEUSEOFNON-CONDENSIBLEGASES 1O06.1 Flat-Front Theory: MathematicalModel I006.1.I Effect of WorkingFluid: FixedSinkConditions . 1056.1.2 Effect of Variations in Sink Temperature 1066.1.3 Effect of WorkingFluid: Variable
12、 SinkConditions . 1086.1.4 GasReservoirs 1096.1.5 Effect of CondenserGeometry. 1246.1.6 Sizing the GasReservoirwith the Flat-Front Model 1256.1o7 Limitations on Control with PassiveSystems 1306.1.8 Variable Set-Point HeatPipes . 1306.1.9 FeedbackControlled HeatPipes 1376.2 Accuracyof the Flat-Front
13、Theory 1406.2.1 Potential Limitations . 1406.2.2 ExperimentalVerification of the Flat-Front Theory 1406.2_3 Summary 1496.3 Diffuse-Front Theory 1496.3.1 Analytical Formulation 1506.3.2 TRWGaspipeComputerProgram . 1586.3.3 ExperimentalVerification of TRWGaspipeProgram 160iiProvided by IHSNot for Resa
14、leNo reproduction or networking permitted without license from IHS-,-,-Tableof Contents(Contd)6.3.4 ParametricStudyof GasFront Behavior 1676.3.5 SummaryandConclusions 1736.4 Transient Performanceof Gas-ControlledHeatPipes . 1756.4.1 WickedReservoirHeatPipes 1766.4.2 Non-WickedReservoirHeatPipes 1816
15、.5 DesigningGas-ControlledHeatPipes forSpacecraftThermalControl 1936.5.1 Summaryof Control Schemes 1936.5.2 DesignApproach 19565.3 DesignConsiderationsandTradegoffs . 1977.0 VARIABLECONDUCTANCETHROUGHTHEUSEOFEXCESSWORKINGFLUID 2078.0 VARIABLECONDUCTANCETHROUGHTHEUSEOFLIQUIDFLOWCONTROL. 2119.0 VARIAB
16、LECONDUCTANCETHROUGHTHEUSEOFVAPORFLOWCONTROL. 2129.1 Analytical Model. 2139,1.1 BlowThroughLimits 2159.1.2 OperatingCharacteristics . 2209.2 Summary. 224I0,0 SELECTEDBIBLIOGRAPHYPERTINENTTOSPACECRAFTTHERMALCONTROL. 226I0.I Hydrodynamics Comparisonof ExperimentalDatawith Theory . 148Cross-sectionof C
17、ondenser:Diffuse-Front Model. 151SchematicDiagramof ExperimentalGas-LoadedHeatPipe . . 161Comparisonof MeasuredandPredictedTemperature-Profilesfor a GasLoadedHeatPipe 165Comparisonof Predicted andObservedHeatTransfer Ratesas a Functiono,f HeatPipe EvaporatorTemperature . . 166Effect of Axial Wall Co
18、nductionon the Con_ense,rTemperatureProfile . 170Effect of WorkingFluid on the CondenserTemperatu,reProfile . 172Effect of OperatingTemperatureon the CondenserTemperatureProfi Ie . 174HeatPipe NodalModel . 178FeedbackControlled HeatPipe Test Set-up 180Comparisonof MeasuredandPredictedTransient HeatP
19、ipe Behavior. 182Transient Start-up Tust Results for Internal ReservoirGasControlled HeatPipe without Teflon Plug (PipeNo. I) . 184TmansientStart-up Test Results for Internal ReservoirGasControlled HeatPipe with Teflo,nPlug (Pipe No. 2) 186Transient Test Results of VaporPenetreti_on Experiments(Heat
20、PipeNo. 2) . 187SchematicDiagramsof Various GasControJl,led HeatPpeReservoirConfigurations . 196SchematicDiagramof LunarSurfaceMagnetometerHeatPipe 200SchematicDiagramof the AmesHeatPipe Experiment 203viProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,
21、-H7-I Schematic Diagram of an Excess Liquid Controlled VariableConductance Heat Pipe 2087-2 Pressure-Temperature Relationship for an Excess LiquidControlled Variable Conductance Heat Pipe 2089-I Schematic Diagram of a Vapor Modulated Variable ConductanceHeat Pipe 2139-2 Vapor Modulated Heat Pipe Lim
22、its Using Water 2179-3 Vapor Modulated Heat Pipe Limits Using Methanol 2189-4 Vapor Modulated Heat Pipe Limits Using Ammonia . 2199-5 Effect of Vapor Throttling on Axial Heat Transfer CapacityWater . 2219-6 Operating Range of Vapor Modulated Heat Pipe - Water 223viiProvided by IHSNot for ResaleNo re
23、production or networking permitted without license from IHS-,-,-,i _ _ TABLESPage4-I Heat Pipe Materials Compatibility Matrix 944-2 Potential Heat Pipe Working Fluids for SpacecraftThermal Control . 966-I Heat Pipe Design Details 1436-2 Experimental Heat Pipe Design Details . 1626-3 Summary of Cases
24、 Studied 1686-4 Results of Calculations: Diffusion FreezeoutRate, Minimum Power and Total Power . 171viiiProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-i_ _1.0 INTRODUCTIONHeat pipe technology has advanced rapidly in the six years sinceGrover, et al
25、, at Los Alamos, published their first paper GI. Fromthe simple tube lined with a screen mesh, heat pipes are now beingfabricated in many geometries with complex, multi-component capillarywick structures tailored to maximize their performance. Much work hasbeen done to advance heat pipe hydrodynamic
26、s, heat transfer, materialscompatibility and fabrication technology. However, one of the mostimportant areas of endeavor has been in heat pipe control.The heat pipe described by Grover is a completely passive device whoseoperating temperature automatically adjusts to the heat source and sinkconditio
27、ns so as to maintain conservation of energy. However, it wasnot long before investigators recognized the many potential applicationsof heat pipes which could be controlled, either actively or passively,to regulate temperatures. Numerous schemes have since been devised toaccomplish this control, and
28、many of these have been implemented.However, as is often the case in a rapidly advancing technology, theability to accurately design and predict the performance of thesedevices had lagged the ability to build and operate them.This program represents an effort to improve this situation through acompr
29、ehensive review and analysis of all aspects of heat pipe technologypertinent to the design of self-controlled, variable conductance, constanttemperature devices for spacecraft thermal control. Subjects consideredinclude hydrostatics, hydrodynamics, heat transfer into and out of thepipe, fluid select
30、ion, and materials compatibility, in addition tonumerous variable conductance control techniques.Most attention is given to passive gas-controlled heat pipes, be theycold or hot, wicked or non-wicked reservoir designs. However, for thesake of completeness, the report also deals briefly with active h
31、eatedreservoir and feedback controlled systems since these will likely playan important role in spacecraft thermal control.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-In addition, the subject matter includes discussionson other controlschemesincl
32、uding (I) liquid flow control, (2) vapor flow control, and(3) the useof excessworkingfluid (rather than non-condensiblegas)to effect condenserarea variations.This report presents the results of efforts to date in eachof the areasmentioned. Since this is a continuing program,someof the materialpresen
33、tedherein constitutes the current status of workin progress. Inother cases, the workhasbeencompletedandthe material presentedservesto documenttheseaccomplishments.In addition to the fundamentalstudies described, a major endeavoronthis programwasthe design, fabrication andtesting of prototype,qualifi
34、cation andflight units for the AmesHeatPipe Experimentonboardthe OAO-Cspacecraft. This experiment,whichinvolves a functionalinternal reservoir gascontrolled heat pipe, is currently scheduledforlaunchin May1972. Althoughseveral fundamentalstudies, ancillary tothe experiment,are presentedin this repor
35、t_ the detailed documentationof this phaseof the programis not. Instead, it constitutes a separatereport; the “AmesHeatPipe ExperimentDescription Document“,to beissued shortly, and is the subject of reference V6.Provided by IHSNot for ResaleNo reproduction or networking permitted without license fro
36、m IHS-,-,-2.0 LITERATUREREVIEWJudgingby the remarkablegrowthrate of the literature, the heatpipe field hasindeedattracted the interest of manyworkersin academia,industry andgovernment.Whereas,in 1965, the pertinent literaturenumberedbut a few documents,TRWscurrent heat pipe bibliographycontainswell
37、over three hundredreferences.As one task on this program,all of the identified andavailable literaturewasreviewedto select that information pertinent to the designof variableconductanceheat pipes for spacecraft thermal control. Theselectivebibliography thus obtained is presentedin Section 5.Wherepos
38、sible, referenceshavebeencatalogedas to their principalsubject. Theseinclude:o Hydrodynamicsiabatic section,. Also, the pipe geometry and wick are uniform axiallyas is: the heat input and rejection over the evaporator and condenserrespectively. Under such circumstances, the lasses are given by G4:Q
39、(L + L a) u_2 K (Rw2-Rv2)4Q (L + La) _vAP = (3-19)v _Pv_Rv4APb = p_gD w sine+ Lcoso17Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-where:Q - total axial heat transportL - total pipe lengthLa - length of adiabatic sectionRv - vapor core radiusRw - w
40、ick radius3.1.6 Capillary Pumping LimitThe fact that there exists a maximum capillary head for any wick-fluid combination (Eq: 3-4) results in a hydrodynamic limit on heat pipecapacity. As mentioned previously, the capillary head must increase withthe liquid and vapor pressure drops as the heat load
41、 (and hence the fluidcirculation rate) increases. Since there exists a limit on the capillaryhead, there also exists a corresponding limit on the heat load if thepressure balance criterion (Eq. 3-I) is to be satisfied. This definesthe capillary pumping limit.In the general case, the capillary pumpin
42、g limit is established for agiven heat pipe by integrating the pressure drop equations along thepipe (as described in the last section) and comparing the sum of thelosses at all points with the local maximum capillary head. Since themaximum capillary head and the body force head are usually not depe
43、ndenton load, the capillary pumping limit criteria is most clearly defined bytransposing Eq. (3-I), using APcmax, to read:APcmax APb AP_ + APv (3-20)In Eq. (3-20), only the terms on the right hand side are load dependent.Thus the heat pipe operates below the capillary pumping limit as long asthe ine
44、quality holds everywhere along the pipe. When the load increasesso that the two sides of the equation are equal at any point along thepipe the capillary pumping limit has been reached. Thus, to calculatethe capillary pumping limit for a given heat pipe the heat load isprogressively increased until such an equality occurs. This is shown inFig. 3-3 for a number of heat pipe configurations.18Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
