Search NASA⌕ Search

SEARCH · Search NASA

Results for “Loop Heat Pipe”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Thermal power loops

The concept of a thermal power loop (TPL) to transport thermal power over relatively large distances is presented as an alternative to heat pipes and their derivatives. The TPL is compared to heat pipes, and capillary pumped loops with respect to size, weight, conservation of thermal potential, start-up, and 1-g testing capability. Test results from a proof of feasibility demonstrator at the NASA JPL are discussed. This analysis demonstrates that the development of specific thermal power loops will result in substantial weight and cost savings for many spacecraft.

Gottschlich, Joseph M.↗
NASA NTRS2006

Heat Rejection Concepts for Lunar Fission Surface Power Applications

This paper describes potential heat rejection design concepts for lunar surface Brayton power conversion systems. Brayton conversion systems are currently under study by NASA for surface power applications. Surface reactors may be used for the moon to power human outposts enabling extended stays and closed loop life support. The Brayton Heat Rejection System (HRS) must dissipate waste heat generated by the power conversion system due to inefficiencies in the thermal-to-electric conversion process. Space Brayton conversion system designs tend to optimize at efficiencies of about 20 to 25 percent with radiator temperatures in the 400 K to 600 K range. A notional HRS was developed for a 100 kWe-class Brayton power system that uses a pumped water heat transport loop coupled to a water heat pipe radiator. The radiator panels employ a tube and fin construction consisting of regularly-spaced circular heat pipes contained within two composite facesheets. The water heat pipes interface to the coolant through curved sections partially contained within the cooling loop. The paper evaluates various design parameters including radiator panel orientation, coolant flow path, and facesheet thickness. Parameters were varied to compare design options on the basis of H2O pump pressure rise and required power, heat pipe unit power and radial flux, radiator area, radiator panel areal mass, and overall HRS mass.

Siamidis, John↗
NASA NTRS2019

Microgravity Liquid-Gas Two-Phase Flow: Review of Pressure Drop and Heat Transfer Correlations and Guidelines for Equipment Operability

In this report we have catalogued the flow regimes observed in microgravity, summarized correlations for the pressure drop and rate of heat transfer that are commonly used, and discuss the validation of a few correlations from available experimental results. Two-phase flow through some specific components such as bends, tees, filters and pumps are discussed from a physical perspective to guide the designer on how reduced gravity might affect their performance. Phase separation in zero gravity is addressed through the behavior and basic design concepts for devices based on passive centrifugal action, capillary forces, gas extraction through a membrane installed in a channel wall and the use of a syringe with a perforated piston to remove bubbles from small liquid volumes. We address the common instabilities that develop in flow loops owing exclusively to the two-phase nature of the flow, e.g., Ledinegg instability and concentration waves. Finally we briefly review flow metering and gauging; two-phase flow through porous media, where pressure drop and flow regime map correlations in zero-g are a current research topic; and basic operation principles of heat pipes and capillary pumped loops.

liquid-gas↗
NASA NTRS1975

A 2.2 sq m /24 sq ft/ self-controlled deployable heat pipe radiator - Design and test

An all heat pipe, deployable radiator has been developed which can effectively control pumped fluid loop temperatures under varying loads using variable conductance panel heat pipes. The 2.2 sq m (24 sq ft) aluminum panel can be coupled to either a fluid header or a flexible heat pipe header capable of transporting 850 watts in a 90-deg bent configuration. Test results support the feasibility of using this system to passively control Freon-21 loop temperatures.

Edelstein, F.↗
NASA NTRS1989

Space Power Free-Piston Stirling Engine Scaling Study

The design feasibility study is documented of a single cylinder, free piston Stirling engine/linear alternator (FPSE/LA) power module generating 150 kW-electric (kW sub e), and the determination of the module's maximum feasible power level. The power module configuration was specified to be a single cylinder (single piston, single displacer) FPSE/LA, with tuning capacitors if required. The design requirements were as follows: (1) Maximum electrical power output; (2) Power module thermal efficiency equal to or greater than 20 percent at a specific mass of 5 to 8 kg/kW(sub e); (3) Heater wall temperature/cooler wall temperature = 1050 K/525 K; (4) Sodium heat-pipe heat transport system, pumped loop NaK (sodium-potassium eutectic mixture) rejection system; (5) Maximum power module vibration amplitude = 0.0038 cm; and (6) Design life = 7 years (60,000 hr). The results show that a single cylinder FPSE/LA is capable of meeting program goals and has attractive scaling attributes over the power range from 25 to 150 kW(sub e). Scaling beyond the 150 kW(sub e) power level, the power module efficiency falls and the power module specific mass reaches 10 kg/kW(sub e) at a power output of 500 kW(sub e). A discussion of scaling rules for the engine, alternator, and heat transport systems is presented, along with a detailed description of the conceptual design of a 150 kW(sub e) power module that meets the requirements. Included is a discussion of the design of a dynamic balance system. A parametric study of power module performance conducted over the power output range of 25 to 150 kW(sub e) for temperature ratios of 1.7, 2.0, 2.5, and 3.0 is presented and discussed. The results show that as the temperature ratio decreases, the efficiency falls and specific mass increases. At a temperature ratio of 1.7, the 150 kW(sub e) power module cannot satisfy both efficiency and specific mass goals. As the power level increases from 25 to 150 kW(sub e) at a fixed temperature ratio, power module efficiency is seen to increase slightly, but at the expense of increased specific mass. An empirical equation relating power module thermal efficiency as a function of power module specific mass, power output, and temperature ratio is developed. Alternative configurations to the single cylinder, direct coupled linear alternator approach are also evaluated, but are shown to have technical drawbacks that lessen their attractiveness. The dynamic balance assembly mass (moving mass and structure) represents 20 to 30 percent of the total single cylinder power module mass. Joining two modules in a balanced opposed configuration eliminates the need for the balancer, and a hot end junction can be made without significant addition of structural mass. Recommendations are made for evaluation of advanced heat pipe concepts, tests of radial flow heat exchangers, and evaluation of high temperature alternator materials.

Jones, D.↗
NASA NTRS1983

Space station needs, attributes and architectural options study. Briefing material: Final review and executive summary

Advantages and disadvantages were assessed for configuration options for a modular 14' diameter space station, a modular aft cargo carrier and a shuttle derived vehicle. Early, intermediate, and mature configurations were defined as well as power requirements, heat rejection, hydrazine usage, and the external scavenging concept. Subsystems were analyzed for propulsion, attitude control, data processing, and communications. Areas of uncertainties, associated costs and benefits, and the cost by phase of the modular and shuttle derived vehicle configurations were identified. Technologies assessed included solar vs nuclear; gravity gradient vs active control; heat pipe radiators vs fluid loops; distributed processors vs centralized, and modular vs shuttle derived configuration. It was determined that the early space station architecture should include: (1) reusable OTV with aerobraking; (2) TMS with telepresence services; (3) OTV/TMS refueling and servicing capability; and (4) attached research laboratories for life sciences and materials processing.

Source record↗
NASA NTRS1989

SP-100 power system conceptual design for lunar base applications

A conceptual design is presented for a nuclear power system utilizing an SP-100 reactor and multiple Stirling cycle engines for operation on the lunar surface. Based on the results of this study, it was concluded that this power plant could be a viable option for an evolutionary lunar base. The design concept consists of a 2500 kWt (kilowatt thermal) SP-100 reactor coupled to eight free-piston Stirling engines. Two of the engines are held in reserve to provide conversion system redundancy. The remaining engines operate at 91.7 percent of their rated capacity of 150 kWe. The design power level for this system is 825 kWe. Each engine has a pumped heat-rejection loop connected to a heat pipe radiator. Power system performance, sizing, layout configurations, shielding options, and transmission line characteristics are described. System components and integration options are compared for safety, high performance, low mass, and ease of assembly. The power plant was integrated with a proposed human lunar base concept to ensure mission compatibility. This study should be considered a preliminary investigation; further studies are planned to investigate the effect of different technologies on this baseline design.

Mason, Lee S.↗
NASA NTRS1991

Design considerations for space radiators based on the liquid sheet (LSR) concept

Concept development work on space heat rejection subsystems tailored to the requirements of various space power conversion systems is proceeding over a broad front of technologies at NASA LeRC. Included are orbital and planetary surface based radiator concepts utilizing pumped loops, a variety of heat pipe radiator concepts, and the innovative liquid sheet radiator (LSR). The basic feasibility of the LSR concept was investigated in prior work which generated preliminary information indicating the suitability of the LSR concept for space power systems requiring cycle reject heat to be radiated to the space sink at low-to-mid temperatures (300 to 400 K), with silicon oils used for the radiator working fluid. This study is directed at performing a comparative examination of LSR characteristics as they affect the basic design of low earth orbit solar dynamic power conversion systems. The power systems considered were based on the closed Brayton (CBC) and the Free Piston Stirling (FPS) cycles, each with a power output of 2 kWe and using previously tested silicone oil (Dow-Corning Me2) as the radiator working fluid. Conclusions indicate that, due to its ability for direct cold end cooling, an LSR based heat rejection subsystem is far more compatible with a Stirling space power system than with a CBC, which requires LSR coupling by means of an intermediate gas/liquid heat exchanger and adjustment of cycle operating conditions.

Juhasz, Albert J.↗
NASA NTRS1995

Preliminary Design of a SP-100/Stirling Radiatively Coupled Heat Exchanger

Several methods for coupling the SP-100 space nuclear reactor to the NASA Lewis Research Center's Free Piston Stirling Power Convertor (FPSPC) are presented. A 25 kWe, dual opposed Stirling convertor configuration is used in these designs. The concepts use radiative coupling between the SP-100 lithium loop and the sodium heat pipe of the Stirling convertor to transfer the heat from the reactor to the convertor. Four separate configurations are presented. Masses for the four designs vary from 41 to 176 kgs. Each design's structure, heat transfer characteristics, and heat pipe performance are analytically modeled.

Schmitz, Paul↗
NASA NTRS2004

Thermal Performance of Capillary Pumped Loops Onboard Terra Spacecraft

The Terra spacecraft is the flagship of NASA's Earth Science Enterprise. It provides global data on the state of atmosphere, land and oceans, as well as their interactions with solar radiation and one another. Three Terra instruments utilize Capillary Pumped Heat Transport System (CPHTS) for temperature control: Each CPHTS, consisting of two capillary pumped loops (CPLs) and several heat pipes and electrical heaters, is designed for instrument heat loads ranging from 25W to 264W. The working fluid is ammonia. Since the launch of the Terra spacecraft, each CPHTS has been providing a stable interface temperature specified by the instrument under all modes of spacecraft and instrument operations. The ability to change the CPHTS operating temperature upon demand while in service has also extended the useful life of one instrument. This paper describes the design and on-orbit performance of the CPHTS thermal systems.

Ku, Jentung↗
NASA NTRS1998

Liquid-Vapor Interface Configurations Investigated in Low Gravity

The Interface Configuration Experiment (ICE) is part of a multifaceted study that is exploring the often striking behavior of liquid-vapor interfaces in low-gravity environments. Although the experiment was posed largely as a test of current mathematical theory, applications of the results should be manifold. In space almost every fluid system is affected, if not dominated, by capillarity (the effects of surface tension). As a result, knowledge of fluid interface behavior, in particular an equilibrium interface shape from which any analysis must begin, is fundamental--from the control of liquid fuels and oxygen in storage tanks to the design and development of inspace thermal systems, such as heat pipes and capillary pumped loops. ICE has increased, and should continue to increase, such knowledge as it probes the specific peculiarities of current theory upon which our present understanding rests. Several versions of ICE have been conducted in the drop towers at the NASA Lewis Research Center, on the space shuttles during the first and second United States Microgravity Laboratory missions (USML-1 and USML-2), and most recently aboard the Russian Mir space station. These studies focused on interfacial problems concerning the existence, uniqueness, configuration, stability, and flow characteristics of liquid-vapor interfaces. Results to date have clearly demonstrated the value of the present theory and the extent to which it can predict the behavior of capillary systems.

Concus, Paul↗
DOE OSTI2023

HIGH-LOW FIDELITY THERMAL HYDRAULIC COUPLING USING AI/MACHINE LEARNING ALGORITHMS

The primary goal of the US Department of Energy (DOE) office of Nuclear Energy Integrated Energy Systems (IES) program is to develop the tools and framework for coupling multi-scale and multi-physical thermal and electrical energy usage and storage systems. High- and low-fidelity (high–low) coupling is a key feature of multi-scale, multi-component systems and has been an important focus of research in the nuclear energy community for the past two decades. An essential feature of demonstrating the capability to couple high-fidelity and low-fidelity systems for real-time applications are surrogate/reduced order models (ROM). For the purposes of this study, surrogate models are essentially Blackbox models, typically developed using supervised Machine learning (ML) algorithms. The surrogate models can be used to mimic the response of high-fidelity models to represent large historical datasets and coupled with more general low-fidelity system models distributed as Functional Mock-up Interface (FMI) or Functional Mock-up Units (FMU) modules. The example is demonstrated with Spallation Neutron Source (SNS) First Target Station flow loop data. The flow loop is a liquid mercury loop with a pump, piping, heat exchange, and internal heat generation in the target window. This work elucidates some of the potential benefits and future needs of developing tools for high–low system coupling of energy systems.

Williams, Wesley↗
NASA NTRS2011

Design of Refractory Metal Heat Pipe Life Test Environment Chamber, Cooling System, and Radio Frequency Heating System

A series of 16 Mo-44.5%Re alloy/sodium heat pipes will be experimentally tested to examine heat pipe aging. To support this evaluation, an environmental test chamber and a number of auxiliary subsystems are required. These subsystems include radio frequency (RF) power supplies/inductive coils, recirculation water coolant loops, and chamber gas conditioning. The heat pipes will be grouped, based on like power and gas mixture requirements, into three clusters of five units each, configured in a pentagonal arrangement. The highest powered heat pipe will be tested separately. Test chamber atmospheric purity is targeted at <0.3 ppb oxygen at an approximate operating pressure of 76 torr (.1.5 psia), maintained by active purification (oxygen level is comparable to a 10(exp -6) torr environment). Treated water will be used in two independent cooling circuits to remove .85 kW. One circuit will service the RF hardware while the other will maintain the heat pipe calorimetry. Initial procedures for the startup and operation of support systems have been identified. Each of these subsystems is outfitted with a variety of instrumentation, integrated with distributed real-time controllers and computers. A local area network provides communication between all devices. This data and control network continuously monitors the health of the test hardware, providing warning indicators followed by automatic shutdown should potentially damaging conditions develop. During hardware construction, a number of checkout tests.many making use of stainless steel prototype heat pipes that are already fabricated.will be required to verify operation.

Martin, J. J.↗
NASA NTRS1974

Heat pipe thermal conditioning panel

Thermal control of electronic hardware and experiments on future space vehicles is critical to proper functioning and long life. Thermal conditioning panels (cold plates) are a baseline control technique in current conceptual studies. Heat generating components mounted on the panels are typically cooled by fluid flowing through integral channels within the panel. However, replacing the pumped fluid coolant loop within the panel with heat pipes offers attractive advantages in weight, reliability, and installation. This report describes the development and fabrication of two large 0.76 x 0.76 m heat pipe thermal conditioning panels to verify performance and establish the design concept.

Saaski, E. W.↗
NASA NTRS2005

Utilizing Radioisotope Power System Waste Heat for Spacecraft Thermal Management

An advantage of using a Radioisotope Power System (RPS) for deep space or planetary surface missions is the readily available waste heat, which can be used for a number of beneficial purposes including: maintaining electronic components within a controlled temperature range, warming propulsion tanks and mobility actuators, and maintaining liquid propellants above their freezing temperature. Previous missions using Radioisotope Thermoelectric Generators (RTGs) dissipated large quantities of waste heat due to the low efficiency of the thermoelectric conversion technology. The next generation RPSs, such as the 110-Watt Stirling Radioisotope Generator (SRG110) will have higher conversion efficiencies, thereby rejecting less waste heat at a lower temperature and may require alternate approaches to transferring waste heat to the spacecraft. RTGs, with efficiencies of ~6 to 7 percent, reject their waste heat at the relatively high heat rejection temperature of 200 C. This is an advantage when rejecting heat to space; however, transferring heat to the internal spacecraft components requires a large and heavy radiator heat exchanger. At the same time, sensitive spacecraft instruments must be shielded from the thermal radiation of the RTG. The SRG110, with an efficiency around 22 percent and 50 C nominal housing surface temperature, can readily transfer the available waste heat directly via heat pipes, thermal straps, or fluid loops. The lower temperatures associated with the SRG110 avoid the chances of overheating other scientific components, eliminating the need for thermal shields. This provides the spacecraft designers more flexibility when locating the generator for a specific mission. A common misconception with high-efficiency systems is that there is not enough waste heat for spacecraft thermal management. This paper will dispel this misconception and investigate the use of a high-efficiency SRG110 for spacecraft thermal management and outline potential methods of waste heat utilization in several conceptual missions (Lunar Rover, Mars Rover, and Titan Lander). The advantages associated with the SRG110 as they relate to ease of assembly, less complex interfaces, and overall mass savings for a spacecraft will be highlighted.

Pantano, David R.↗
DOE OSTI2025

Multiphysics Modeling of Microreactors with NEAMS codes, and Validation Based on KRUSTY Reactivity Insertion

The NEAMS Multiphysics Applications team continues to assess code usability and functionality for microreactor design and safety analyses, while demonstrating that NEAMS tools capture both steady-state and transient behavior across distinct microreactor concepts. In FY2025, the team advanced full-core, high-fidelity, multiphysics models that solve more complex problems and strengthen verification/validation for several microreactor systems: heat-pipe microreactor (HPMR), gas-cooled microreactor (GCMR), and the KRUSTY experiment. These models employ the MOOSE MultiApp/Transfers architecture with Griffin for neutronics, BISON for heat conduction/thermomechanics, Sockeye for heat pipes, SAM/THM for coolant channels and loops, and SWIFT for hydride behavior, with meshes generated via the MOOSE Reactor Module. The graphite models available in the Grizzly code were also investigated for future analyses. For the HPMR, a Na-HPMR variant was constructed to align with recently validated heat-pipe experiments and Sockeye’s LCVF capability, enabling mechanistic heat-pipe transients and startup modeling. The Na-HPMR will serve as the primary model for HPMR investigations in upcoming tasks. The load-following and single heat-pipe failure scenarios (Griffin/BISON/Sockeye), which were previously modeled for the K-HPMR, were replicated for the Na-HPMR, showing strong negative temperature feedback and highly localized thermal effects, respectively, while the startup case captured vapor-front progression and heat-removal activation. Solid mechanics was added to the previously built K-HPMR full-core model in BISON, showing minimal impact on steady-state reactivity yet enabling stress-field predictions that prepare the path for full-core TRISO performance analyses. For the GCMR, automated steady-state and four transient scenarios were executed using Griffin/BISON/SAM/SWIFT. Results confirm robust inherent safety: power collapses promptly in loss-of-cooling events, the inlet-temperature drop settles to a new equilibrium, and a single-channel blockage yields only a ~30 K local fuel-temperature rise with <0.4% power decrease. SWIFT-predicted hydrogen redistribution affects reactivity during both steady-state and transient conditions, underscoring its importance. A Brayton-cycle balance of plant (BOP) model in SAM/THM demonstrated stable startup behavior, and xenon-driven reactivity during load following was analyzed. To improve TRISO-compact temperature fidelity, a fast multiscale Heat Source Decomposition (HSD) treatment was implemented. Against heterogeneous benchmarks, HSD reduces underprediction of kernel temperatures and lowers predicted peak powers in reactivity-insertion transients compared to previous homogenized models. KRUSTY warm-critical validation progressed from FY2024 baselines: the 15Ȼ insertion shows excellent agreement in peak power (~2% high) and temperature trends, and the 30Ȼ case was automated via a feedback controller that maintained power near 3 kW for ~150 s with close agreement to data. The successful modeling of the warm critical tests has laid a strong foundation for simulating more complex nuclear system tests in the years ahead. Throughout FY2025, developer feedback was provided (e.g., MOOSE batch mesh generation, distributed pre-split meshes, Griffin sweeper on displaced meshes), several new models were contributed to the Virtual Test Bed, and an OECD-NEA WPRS multiphysics benchmark based on the HPMR was initiated to enable broader cross-comparison and best-practice development with the nuclear community at large.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
NASA NTRS1979

Optimum design of spacecraft radiators for large capacity or long duration mission applications

Results of trade studies comparing optimum pumped fluid and hybrid heat pipe/pumped fluid radiator designs are presented. Design variables considered in the system optimization analyses include transport fluid properties and Reynolds number, pump loop component reliabilities, micrometeoroid protection, heat pipe spacing, manifolding and flow routing in pumped fluid designs, transport tubing spacing and diameters, and radiator fin parameters. Criteria for evaluating candidate radiator system designs include mass, radiator area, and overall system reliability. The studies show advantages in constructing large systems from small independent subsystems with oversizing to account for subsystem failures. The optimum size and survivability of the subsystems are identified as a function of the radiator construction, the system heat rejection requirements, the mission duration, and the system reliability requirements.

Leach, J. W.↗