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  • 1
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    An Experimental Study of Pressure Oscillation in a Capillary Pumped Loop with Multiple Evaporators and Condensers (1998)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The heat transport capability of a capillary pumped loop (CPL) is limited by the pressure drop that its evaporator wick can sustain. The pressure drop in a CPL is not constant even under seemingly steady operation, but rather exhibits an oscillatory behavior. A hydrodynamic theory based on a mass-spring-dashpot model was previously developed to predict the pressure oscillation in a CPL with a single evaporator and a single condenser. The theory states that the pressure oscillation is a function of physical dimensions of the CPL components and operating conditions. Experimental data agreed very well with theoretical predictions. The hydrodynamic stability theory has recently been extended to predict the pressure oscillations in CPLs with multiple evaporators and multiple condensers. Concurrently, an experimental study was conducted to verify the theory and to investigate the effects of various parameters on the pressure oscillation. Four evaporators with different wick properties were tested using a test loop containing two condenser plates. The test loop allowed the four evaporators to be tested in a single-pump, two-pump or four-pump configuration, and the two condenser plates to be plumbed either in parallel or in series. Test conditions included varying the power input, the reservoir set point temperature, the condenser sink temperature, and the flow resistance between the reservoir and the loop. Experimental results agreed well with theoretical predictions.
    Keywords: Fluid Mechanics and Heat Transfer
    Type: Energy Conversion Engineering; Aug 02, 1998 - Aug 06, 1998; Colorado Springs, CO; United States
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  • 2
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    Multi-Evaporator Miniature Loop Heat Pipe for Small Spacecraft Thermal Control (2010)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Under NASA s New Millennium Program Space Technology 8 (ST 8) Project, four experiments Thermal Loop, Dependable Microprocessor, SAILMAST, and UltraFlex - were conducted to advance the maturity of individual technologies from proof of concept to prototype demonstration in a relevant environment , i.e. from a technology readiness level (TRL) of 3 to a level of 6. This paper presents the new technologies and validation approach of the Thermal Loop experiment. The Thermal Loop is an advanced thermal control system consisting of a miniature loop heat pipe (MLHP) with multiple evaporators and multiple condensers designed for future small system applications requiring low mass, low power, and compactness. The MLHP retains all features of state-of-the-art loop heat pipes (LHPs) and offers additional advantages to enhance the functionality, performance, versatility, and reliability of the system. Details of the thermal loop concept, technical advances, benefits, objectives, level 1 requirements, and performance characteristics are described. Also included in the paper are descriptions of the test articles and mathematical modeling used for the technology validation. An MLHP breadboard was built and tested in the laboratory and thermal vacuum environments for TRL 4 and TRL 5 validations, and an MLHP proto-flight unit was built and tested in a thermal vacuum chamber for the TRL 6 validation. In addition, an analytical model was developed to simulate the steady state and transient behaviors of the MLHP during various validation tests. Capabilities and limitations of the analytical model are also addressed.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: GSFC.CP.4681.2011 , Multi-Evaporator Miniature Loop Heat Pipe for Small Spacecraft Thermal Control; Jan 04, 2010 - Jan 07, 2010; Orlando, FL; United States
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  • 3
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    Multi-Evaporator Miniature Loop Heat Pipe for Small Spacecraft Thermal Control (2010)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Under NASA s New Millennium Program Space Technology 8 (ST 8) Project, Goddard Space Fight Center has conducted a Thermal Loop experiment to advance the maturity of the Thermal Loop technology from proof of concept to prototype demonstration in a relevant environment , i.e. from a technology readiness level (TRL) of 3 to a level of 6. The thermal Loop is an advanced thermal control system consisting of a miniature loop heat pipe (MLHP) with multiple evaporators and multiple condensers designed for future small system applications requiring low mass, low power, and compactness. The MLHP retains all features of state-of-the-art loop heat pipes (LHPs) and offers additional advantages to enhance the functionality, performance, versatility, and reliability of the system. An MLHP breadboard was built and tested in the laboratory and thermal vacuum environments for the TRL 4 and TRL 5 validations, respectively, and an MLHP proto-flight unit was built and tested in a thermal vacuum chamber for the TRL 6 validation. In addition, an analytical model was developed to simulate the steady state and transient behaviors of the MLHP during various validation tests. The MLHP demonstrated excellent performance during experimental tests and the analytical model predictions agreed very well with experimental data. All success criteria at various TRLs were met. Hence, the Thermal Loop technology has reached a TRL of 6. This paper presents the validation results, both experimental and analytical, of such a technology development effort.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: GSFC.CP.4680.201 , Multi-Evaporator Miniature Loop Heat Pipe for Small Spacecraft Thermal Control; Jan 04, 2010 - Jan 07, 2010; Orlando, FL; United States
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  • 4
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    Flight Testing of the Capillary Pumped Loop 3 Experiment (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The Capillary Pumped Loop 3 (CAPL 3) experiment was a multiple evaporator capillary pumped loop experiment that flew in the Space Shuttle payload bay in December 2001 (STS-108). The main objective of CAPL 3 was to demonstrate in micro-gravity a multiple evaporator capillary pumped loop system, capable of reliable start-up, reliable continuous operation, and heat load sharing, with hardware for a deployable radiator. Tests performed on orbit included start-ups, power cycles, low power tests (100 W total), high power tests (up to 1447 W total), heat load sharing, variable/fixed conductance transition tests, and saturation temperature change tests. The majority of the tests were completed successfully, although the experiment did exhibit an unexpected sensitivity to shuttle maneuvers. This paper describes the experiment, the tests performed during the mission, and the test results.
    Keywords: Spacecraft Design, Testing and Performance
    Type: Space Technology and Applications Forum; Feb 02, 2003 - Feb 06, 2003; Albuquerque, NM; United States
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  • 5
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    Investigation of the Temperature Hysteresis Phenomenon of a Loop Heat Pipe (1999)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The temperature hysteresis phenomenon of a Loop Heat Pipe (LHP) was experimentally investigated. The temperature hysteresis was identified by the fact that the operating temperature depends upon not only the imposed power but also the previous history of the power variation. The temperature hysteresis could impose limitations on the LHP applications since the LHP may exhibit different steady-state operating temperatures at a given power input even when the condenser sink temperature remains unchanged. In order to obtain insight to this phenomenon, a LHP was tested at different elevations and tilts by using an elaborated power profile. A hypothesis was suggested to explain the temperature hysteresis. This hypothesis explains well the experimental observations. Results of this study provide a better understanding of the performance characteristics of the LHPS.
    Keywords: Fluid Mechanics and Heat Transfer
    Type: National Heat Transfer; Aug 15, 1999 - Aug 17, 1999; Albuquerque, NM; United States
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  • 6
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    Mathematical Modeling of Loop Heat Pipes (1998)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: The primary focus of this study is to model steady-state performance of a Loop Heat Pipe (LHP). The mathematical model is based on the steady-state energy balance equations at each component of the LHP. The heat exchange between each LHP component and the surrounding is taken into account. Both convection and radiation environments are modeled. The loop operating temperature is calculated as a function of the applied power at a given loop condition. Experimental validation of the model is attempted by using two different LHP designs. The mathematical model is tested at different sink temperatures and at different elevations of the loop. Tbc comparison of the calculations and experimental results showed very good agreement (within 3%). This method proved to be a useful tool in studying steady-state LHP performance characteristics.
    Keywords: Fluid Mechanics and Heat Transfer
    Type: AIAA Paper 99-0477
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  • 7
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    An Advanced Loop Heat Pipe for Cryogenic Applications (2016)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A loop heat pipe (LHP) is a very versatile heat transfer device which can transport a large heat load over a long distance with a small temperature difference. All LHPs currently servicing orbiting spacecraft are designed to operate in the room temperature range. Future space telescopes and space-based Earth resource imaging satellites require passive cryogenic heat transport devices that can thermally couple remote cryocoolers to sensor or instrument of interest while providing the capability of payload vibration/jitter isolation, implementation of redundant coolers, and coupling of multiple sensors to a common heat sink. All of these requirements can be satisfied by using a cryogenic LHP (CLHP). Although the development of CLHPs faces several technical challenges, NASA Goddard Space Flight Center has devoted extensive efforts in developing CLHP technology over the past decade and has made significant progress. In particular, the combination of the innovative ideas of using a secondary capillary pump to manage the parasitic heat gain and using a hot reservoir to reduce the system pressure under the ambient condition has led to the successful development of the CLHP. Several CLHPs charged with nitrogen and hydrogen were built and tested in thermal vacuum chambers. These CLHPs demonstrated reliable start-up and robust operation during power cycle and sink temperature cycle tests.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: GSFC-E-DAA-TN33812 , Thermal & Fluids Analysis Workshop (TFAWS 2016); Aug 01, 2016 - Aug 05, 2016; Moffet Field, CA; United States
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  • 8
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    An Advanced Loop Heat Pipe for Cryogenic Applications (2017)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A loop heat pipe (LHP) is a very versatile heat transfer device that can transport a large heat load over a long distance with a small temperature difference. All LHPs currently servicing orbiting spacecraft are designed to operate in the room temperature range. Future space telescopes and space-based Earth resource imaging satellites require passive cryogenic heat transport devices that can thermally couple remote cryocoolers to sensor or instrument of interest while providing the capability of payload vibration jitter isolation, implementation of redundant coolers, and coupling of multiple sensors to a common heat sink. All of these requirements can be satisfied by using a cryogenic LHP (CLHP). Although the development of CLHPs faces several technical challenges, NASA Goddard Space Flight Center has devoted extensive efforts in developing CLHP technology over the past decade and has made significant progress. In particular, the combination of the innovative ideas of using a secondary capillary pump to manage the parasitic heat gain and using a hot reservoir to reduce the system pressure under the ambient condition has led to the successful development of the CLHP. Several CLHPs charged with nitrogen and hydrogen were built and tested in thermal vacuum chambers. These CLHPs demonstrated reliable start-up and robust operation during power cycle and sink temperature cycle tests.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: GSFC-E-DAA-TN43600 , International Conference on Environmental Systems (ICES) 2017; Jul 16, 2017 - Jul 20, 2017; Charleston, SC; United States
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  • 9
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    Mathematical Modeling of Loop Heat Pipes with Multiple Capillary Pumps and Multiple Condensers (2004)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Loop Heat Pipes (LHPs) have proven themselves as reliable and robust heat transport devices for spacecraft thermal control systems. So far, the LHPs in earth-orbit satellites perform very well as expected. Conventional LHPs usually consist of a single capillary pump for heat acquisition and a single condenser for heat rejection. Multiple pump/multiple condenser LHPs have shown to function very well in ground testing. Nevertheless, the test results of a dual pump/condenser LHP also revealed that the dual LHP behaved in a complicated manner due to the interaction between the pumps and condensers. Thus it is redundant to say that more research is needed before they are ready for 0-g deployment. One research area that perhaps compels immediate attention is the analytical modeling of LHPs, particularly the transient phenomena. Modeling a single pump/single condenser LHP is difficult enough. Only a handful of computer codes are available for both steady state and transient simulations of conventional LHPs. No previous effort was made to develop an analytical model (or even a complete theory) to predict the operational behavior of the multiple pump/multiple condenser LHP systems. The current research project offered a basic theory of the multiple pump/multiple condenser LHP operation. From it, a computer code was developed to predict the LHP saturation temperature in accordance with the system operating and environmental conditions.
    Keywords: Spacecraft Design, Testing and Performance
    Type: 2nd International Energy Conversion Engineering Conference; Aug 16, 2004 - Aug 19, 2004; Providence, RI; United States
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  • 10
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    An Advanced Loop Heat Pipe for Cryogenic Applications (2017)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A loop heat pipe (LHP) is a very versatile heat transfer device that can transport a large heat load over a long distance with a small temperature difference. All LHPs currently servicing orbiting spacecraft are designed to operate in the room temperature range. Future space telescopes and space-based Earth resource imaging satellites require passive cryogenic heat transport devices that can thermally couple remote cryocoolers to sensor or instrument of interest while providing the capability of payload vibration jitter isolation, implementation of redundant coolers, and coupling of multiple sensors to a common heat sink. All of these requirements can be satisfied by using a cryogenic LHP (CLHP). Although the development of CLHPs faces several technical challenges, NASA Goddard Space Flight Center has devoted extensive efforts in developing CLHP technology over the past decade and has made significant progress. In particular, the combination of the innovative ideas of using a secondary capillary pump to manage the parasitic heat gain and using a hot reservoir to reduce the system pressure under the ambient condition has led to the successful development of the CLHP. Several CLHPs charged with nitrogen and hydrogen were built and tested in thermal vacuum chambers. These CLHPs demonstrated reliable start-up and robust operation during power cycle and sink temperature cycle tests.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: ICES-2017-58 , GSFC-E-DAA-TN42271 , International Conference on Environmental Systems; Jul 16, 2017 - Jul 20, 2017; Charleston, SC; United States
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