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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.

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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Development of a Magnetic Refrigerator Operating Between 2K and 10K

An adiabatic demagnetization refrigerator (ADR) is under development at NASA-Ames Research Center that will operate between 2 K and 10 K and will provide 50 mW of cool ng at 2 K. Gadolinium Gallium Garnet (GGG) is selected as the refrigerant for the ADR, To minimize temperature gradients in the GGG, thick slices of GGG are sandwiched together with strips of high-purity copper in between them. The copper strips are used to exchange heat between the GGG and the 2 K and the 10 K heat switches. The heat transfer across the Cu-GGG interfaces is improved by placing thin foils of' high-purity indium at the interfaces. The heat switches employed in the ADR have no moving parts. The 10 K heat switch is a helium gas-gap heat switch; while, the 2 K heat switch is a He ll-gap heat switch. A switch is on when its gap Is filled with helium and is off' when the gap is emptied. This is accomplished with an activated carbon pump (ACP). The ACP adsorbs helium when cooled and desorbs it when heated. A superconducting magnet capable of providing 9 T at 2 K is used for the ADR cycle. A prototype of this refrigerator has been built and is currently under test. A detailed design of the ADR and preliminary test results performed on the prototype ADR will be presented.

Lane, David A.↗
NASA NTRS1991

Oscillating Thermal Switch

Proposed heat switch transfers heat from source to sink in regular cycles. Self-sustaining; actuated by transferred heat, contains no moving parts, and needs no external heaters or electronic circuitry to synchronize heat-transfer periods or control heat-transfer rates. Intended for use in gas-sorption refrigerator.

Petrick, S. Walter↗
DOE OSTI2024

A nanoscale photonic thermal transistor for sub-second heat flow switching

Abstract Control of heat flow is critical for thermal logic devices and thermal management and has been explored theoretically. However, experimental progress on active control of heat flow has been limited. Here, we describe a nanoscale radiative thermal transistor that comprises of a hot source and a cold drain (both are ~250 nm-thick silicon nitride membranes), which are analogous to the source and drain electrodes of a transistor. The source and drain are in close proximity to a vanadium oxide (VO x )-based planar gate electrode, whose dielectric properties can be adjusted by changing its temperature. We demonstrate that when the gate is located close ( < ~1 µm) to the source-drain device and undergoes a metal-insulator transition, the radiative heat transfer between the source and drain can be changed by a factor of three. More importantly, our nanomembrane-based thermal transistor features fast switching times ( ~ 500 ms as opposed to minutes for past three-terminal thermal transistors) due to its small thermal mass. Our experiments are supported by detailed calculations that highlight the mechanism of thermal modulation. We anticipate that the advances reported here will open new opportunities for designing thermal circuits or thermal logic devices for advanced thermal management.

42 ENGINEERING↗
NASA NTRS1990

Adiabatic demagnetization refrigerator for space use

An Adiabatic Demagnetization Refrigerator (ADR) for space use is under development at NASA's Goddard Space Flight Center (GSFC). The breadboard ADR operated at 100 mK for 400 minutes. Some significant changes to that ADR, designed to eliminate shortcomings revealed during tests, are reported. To increase thermal contact, the ferric ammonium sulfate crystals were grown directly on gold-plated copper wires which serve as the thermal bus. The thermal link to the X-ray sensors was also markedly improved. To speed up the testing required to determine the best design parameters for the gas gap heat switch, the new heat switch has a modular design and is easy to disassemble.

Serlemitsos, A. T.↗
NASA NTRS1983

Cycling Joule Thomson refrigerator

A symmetrical adsorption pump/compressor system having a pair of mirror image legs and a Joule Thomson expander, or valve, interposed between the legs thereof for providing a, efficient refrigeration cycle is described. The system further includes a plurality of gas operational heat switches adapted selectively to transfer heat from a thermal load and to transfer or discharge heat through a heat projector, such as a radiator or the like. The heat switches comprise heat pressurizable chambers adapted for alternate pressurization in response to adsorption and desorption of a pressurizing gas confined therein.

Tward, E.↗
NASA NTRS2001

Continuous Magnetic Refrigerators for Cooling in the 0.05 to 10 K Range

Low temperature refrigeration is an increasingly vital technology for NASA's Space Science program since most detectors being developed for x-ray, IR and sub-millimeter missions must be cooled to below 100 mK in order to meet the requirements for energy and spatial resolution. For space applications, magnetic refrigeration has an inherent advantage over alternative techniques because it does not depend on gravity. Adiabatic demagnetization refrigerators, or ADRs, are relatively simple, solid state devices. The basic elements are a magnetocaloric refrigerant (usually an encapsulated paramagnetic salt) located in the bore of a superconducting magnet, and a heat switch linking the salt to a heat sink. The alignment of magnetic spins with the magnetic field causes the refrigerant to warm as the magnetic field increases and cool as the field decreases. Thus the simple process of magnetizing the refrigerant to high field with the heat switch closed, then demagnetizing it with the heat switch open allows one to obtain temperatures well below 100 mK using a heat sink as warm as 4.2 K. The refrigerant can maintain a low temperature for a length of time depending on the applied and parasitic heat loads, its mass, and the initial magnetic field strength. Typically ADRs are designed for 12-24 hours of hold time, after which they must be warmed up and recycled.

Shirron, Peter↗
NASA NTRS2003

Continuous Magnetic Refrigerators for Cooling in the 0.05 to 10 K Range: Progress and Future Development

Low temperature refrigeration is an increasingly vital technology for NASA s Space Science program since most detectors being developed for x-ray, IR and sub-millimeter missions must be cooled to below 100 mK in order to meet the requirements for energy and spatial resolution. For space applications, magnetic refrigeration has an inherent advantage over alternative techniques because it does not depend on gravity. Adiabatic demagnetization refrigerators, or ADRs, are relatively simple, solid state devices. The basic elements are a magnetocaloric refrigerant (usually an encapsulated paramagnetic salt) located in the bore of a superconducting magne$, and a heat switch linking the salt to a heat sink. The alignment of magnetic spins with the magnetic field causes the refrigerant to warm as the magnetic field increases and cool as the field decreases. Thus the simple process of magnetizing the refrigerant to high field with the heat switch closed, then demagnetizing it with the heat switch open allows one to obtain temperatures well below 100 mK using a heat sink as warm as 4.2 K. The refrigerant can maintain a low temperature for a length of time depending on the applied and parasitic heat loads, its mass, and the initial magnetic field strength. Typically ADRs are designed for 12-24 hours of hold time, after which they must be warmed up and recycled. The drawback to single-shot ADRs is that the cooling power per unit mass is relatively low. Refrigerants that are suitable for low temperature operation necessarily have low magnetic ion density, and therefore low entropy density. Since ADRs store entropy, systems with even modest cooling powers (a few microwatts) at temperatures below 100 mK tend to be massive, averaging 10-15 kg.

Shirron, Peter↗
NASA NTRS1986

Dynamic design of gas sorption J-T refrigerator

A long-life Joule-Thomson refrigerator which is heat powered, involves no sealing, and has few mechanical parts is desirable for long-term sensor cooling in space. In the gas-sorption J-T refrigerator, cooling is achieved by gas sorption (either adsorption or absorption) processes. Currently, a modular, single-stage refrigerator is being designed and built to be operated at 20 K. The design was analyzed using a dynamic model, which is described here. The model includes the kinetics of the compressors and the heat switches, the heat transfer of the pre-coolers and the heat exchangers, the on/off ratio of the check valves, and the impedance of the J-T valve. The cooling power, the cycle time, and the operating conditions were obtained in terms of the power input, the heat sink temperature, and the J-T impedance.

Chan, C. K.↗
NASA NTRS2004

Development of a Lunar Consumables Storage and Distribution Depot

NASA is in the preliminary planning stages for a future lunar base as a response to President George W. Bush's recent announcement of a new sustained exploration program beyond low earth orbit. Kennedy Space Center engineers are supporting this program by utilizing experience in Spaceport system design and operations to help develop a Lunar Consumables Depot. This depot will store propellants, life support fluids, and other consumables either transported from Earth or manufactured from In Situ resources. The depot will distribute these consumables in an energy efficient manner to end users including spacecraft, habitation modules, and rovers. This paper addresses some of the changes to lunar base architecture design as a result of advances in knowledge of lunar resources over the past 35 years, as well as technology advances in the area of In Situ Resource Utilization and consumable storage and distribution. A general system level description of the depot will be presented, including overall design philosophy and high level requirements. Finally, specific subsystem technologies that have been or will be developed by KSC will be addressed. Examples of these technologies are automated umbilicals, cryogenic refrigerators, novel storage vessels, advanced heat switches and heat exchangers, and self healing gaskets and wires.

Mueller, Robert P.↗
NASA NTRS1990

Conceptual design of a 0.1 W magnetic refrigerator for operation between 10 K and 2 K

The design of a magnetic refrigerator for space applications is discussed. The refrigerator is to operate in the temperature range of 10 K-2 K, at a 2 K cooling power of 0.10 W. As in other magnetic refrigerators operating in this temperature range GGG has been selected as the refrigerant. Crucial to the design of the magnetic refrigerator are the heat switches at both the hot and cold ends of the GGG pill. The 2 K heat switch utilizes a narrow He II filled gap. The 10 K heat switch is based on a narrow helium gas gap. For each switch, the helium in the gap is cycled by means of activated carbon pumps. The design concentrates on reducing the switching times of the pumps and the switches as a whole. A single stage system (one magnet; one refrigerant pill) is being developed. Continuous cooling requires the fully stationary system to have at least two stages running parallel/out of phase with each other. In order to conserve energy, it is intended to recycle the magnetic energy between the magnets. To this purpose, converter networks designed for superconducting magnetic energy storage are being studied.

Helvensteijn, Ben P. M.↗