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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Advantages of cryopumping with liquid hydrogen instead of helium refrigerators

Open loop hydrogen vaporizers and helium refrigerators are compared for operational complexity, installation and operating cost, and safety requirements. Data from two vacuum chambers using helium refrigerators are used to provide comparative data. In general, the use of hydrogen is attractive in the larger systems, even when extra safety precautions are taken. Emotional resistance to the use of hydrogen because of safety requirements is considered great. However, the experience gained in the handling of large quantities of cryogenics, particularly hydrogen and liquefied natural gases, should be considered in the design of open loop hydrogen cooling systems.

J.W. Anderson↗
NASA NTRS1973

Analysis of a combined refrigerator-generator space power system

Description of a single-shaft and a two-shaft rotating machinery arrangements using neon for application in a combined refrigerator-generator power system for space missions. The arrangements consist of combined assemblies of a power turbine, alternator, compressor, and cry-turbine with a single-stage radial-flow design. A computer program was prepared to study the thermodynamics of the dual system in the evaluation of its cryocooling/electric capacity and appropriate weight. A preliminary analysis showed that a two-shaft arrangement of the power- and refrigeration-loop rotating machinery provided better output capacities than a single-shaft arrangement, without prohibitive operating compromises.

Klann, J. L.↗
NASA NTRS1975

A two-degree Kelvin refrigerator

Open-cycle cryogenic refrigerator maintains temperature as low as 2K for periods up to six months. Designed to cool an infrared detector, refrigerator can be used in cooling Josephson-junction devices, magnetic bubble domains, and superconducting devices.

Stephens, J. B.↗
NASA NTRS1975

Helium refrigerator

An improved helium refrigerator of the type which includes a plurality of counter-flow heat exchangers and has a maximum reserve cooling capacity when the final or low-temperature heat exchanger is substantially filled with liquid helium, and a minimum reserve cooling capacity when the low-temperature heat exchanger is substantially filled with gas. An electrical bridge circuit including a pair of temperature responsive resistors is mounted on the low-temperature heat exchanger for providing a continuous indication of the reserve cooling capacity of the refrigerator.

Ervin R Wiebe↗
NASA NTRS1977

Photovoltaic-powered refrigerator experiment at Isle Royale National Park

The use of a photovoltaic power system to operate an electric refrigerator at a trail construction camp at Isle Royale, Michigan is investigated. The use of P/V power for refrigeration in a remote installation is demonstrated. System design as well as predicted and measured system performance are presented.

Ratajczak, A. F.↗
NASA NTRS1979

Refrigerant leak detector

Quantitative leak detector visually demonstrates refrigerant loss from precision volume of large refrigeration system over established period of time from single test point. Mechanical unit is less costly than electronic "sniffers" and is more reliable due to absence of electronic circuits that are susceptible to drift.

Byrne, E. J.↗
NASA NTRS1974

Fractional watt Vuillemier cryogenic refrigerator program engineering notebook. Volume 1: Thermal analysis

The cryogenic refrigerator thermal design calculations establish design approach and basic sizing of the machine's elements. After the basic design is defined, effort concentrates on matching the thermodynamic design with that of the heat transfer devices (heat exchangers and regenerators). Typically, the heat transfer device configurations and volumes are adjusted to improve their heat transfer and pressure drop characteristics. These adjustments imply that changes be made to the active displaced volumes, compensating for the influence of the heat transfer devices on the thermodynamic processes of the working fluid. Then, once the active volumes are changed, the heat transfer devices require adjustment to account for the variations in flows, pressure levels, and heat loads. This iterative process is continued until the thermodynamic cycle parameters match the design of the heat transfer devices. By examing several matched designs, a near-optimum refrigerator is selected.

Miller, W. S.↗
NASA NTRS1974

Fractional watt Vuillemier cryogenic refrigerator program engineering notebook. Volume 2: Stress analysis

A structural analysis performed on the 1/4-watt cryogenic refrigerator. The analysis covered the complete assembly except for the cooling jacket and mounting brackets. Maximum stresses, margin of safety, and natural frequencies were calculated for structurally loaded refrigerator components shown in assembly drawings. The stress analysis indicates that the design is satisfactory for the specified vibration environment, and the proof, burst, and normal operating loads.

Miller, W. S.↗
NASA NTRS1979

Thermal compensator for closed-cycle helium refrigerator

The wave length of an infrared, semiconductor laser diode having an output frequency that is dependent on the diode temperature is maintained substantially constant by maintaining the diode temperature constant. The diode is carried by a cold tip of a closed cycle helium refrigerator. The refrigerator has a tendency to cause the temperature of the cold tip to oscillate. A heater diode and a sensor diode are placed on a thermal heat sink that is the only highly conductive thermal path between the laser diode and the cold tip. The heat sink has a small volume and low thermal capacitance so that the sensing diode is at substantially the same temperature as the heater diode and substantially no thermal lag exists between them. The sensor diode is connected in a negative feedback circuit with the heater diode so that the tendency of the laser diode to thermally oscillate is virtually eliminated.

Jennings, D. E.↗
NASA NTRS1979

Shock isolator for operating a diode laser on a closed-cycle refrigerator

A diode laser mounted within a helium refrigerator is mounted using a braided copper ground strap which provides good impact shock isolation from the refrigerator cold-tip while also providing a good thermal link to the cold-tip. The diode mount also contains a rigid stand-off assembly consisting of alternate sections of nylon and copper which serve as cold stations to improve thermal isolation from the vaccum housing mounting structure. Included in the mount is a Pb-In alloy wafer inserted between the cold-tip and the diode to damp temperature fluctuations occurring at the cold-tip.

Jennings, D. E.↗
NASA NTRS1980

A thermodynamic analysis of a solar-powered jet refrigeration system

The article describes and analyzes a method of using solar energy to drive a jet refrigeration system. A new technique is presented in the form of a performance nomogram combining the energy and momentum equations to determine the performance characteristics. A numerical example, using water as the working fluid, is given to illustrate the nomogram procedure. The resulting coefficient of performance was found comparable with other refrigeration systems such as the solar-absorption system or the solar-Rankine turbocompressor system.

Lansing, F. L.↗
NASA NTRS1980

Magnetic refrigeration in space - Practical considerations

Various schemes of using adiabatic demagnetization to provide refrigeration in the 10-1000 mK range are discussed with particular reference to the requirements for use in space. The methods considered are complete demagnetization, isothermal demagnetization, moving magnet demagnetization, and continuous refrigeration. The requirements that are important for use in space are low mass, low power dissipation, high mechanical rigidity, modular design, and ease of use.

Kittel, P.↗
NASA NTRS1981

An adiabatic demagnetization refrigerator for infrared bolometers

Adiabatic demagnetization refrigerators have been built and installed in small portable liquid helium cryostats to test the feasibility of this method of cooling infrared bolometric detectors to temperatures below 0.3 K. Performance has been achieved which suggests that bolometer temperatures of 0.2 K can be maintained for periods of approximately 60 hours. Applications to sensitive infrared detection from ground-based telescopes and space satellites are discussed. Design data are given which permit the evaluation of refrigerator performance for a variety of design parameters.

Britt, R. D.↗
NASA NTRS1982

Can He-3 - He-4 dilution refrigerators operate aboard spacecraft

The possibility of using an He-3 - He-4 dilution refrigerator to provide cooling down to millikelvin-range temperatures for high sensitivity and low noise instruments employed in future space missions is considered. Calculations are presented which demonstrate that electrostriction can be substituted for gravity as a practical means of achieving phase separation, with well defined interfaces in mixing chambers of spacecraft dilution refrigerators. An electric field of the required strength may be created by a potential difference of about 5000 V, across a gap of 0.5 mm.

Jackson, H. W.↗
NASA NTRS1984

Ionic Refrigerator

With no moving parts, proposed refrigerator has long life. Thermal energy of refrigeration process transported by hydrogen ions that go through three phase changes in absorbing heat and three phase changes in dissipating heat.

Richter, R.↗
NASA NTRS1982

Single shot demountable self-contained He-3 refrigerator

The present investigation is concerned with the development of a self-contained demountable He-3 refrigerator which greatly increases the versatility of a cold-plate-style helium Dewar. The refrigerator is controlled by a single heater. The considered design makes it possible to achieve a temperature of 0.27 K without costly or time-consuming modifications to the Dewar. An example for an employment of a temperature of less than 1 K in space is related to the study of the critical behavior of He-3/He-4 mixtures in the absence of gravitational mixing. This requires a temperature of 0.87 K. Such low temperatures can also be utilized in the space operation of infrared telescopes. Attention is given to details of system design, the operating principles, and aspects of performance.

Kittel, P.↗
NASA NTRS1983

Refrigeration for Cryogenic Sensors

Research in cryogenically cooled refrigerators is discussed. Low-power Stirling cryocoolers; spacecraft-borne long-life units; heat exchangers; performance tests; split-stirling, linear-resonant, cryogenic refrigerators; and computer models are among the topics discussed.

Gasser, M. G.↗
NASA NTRS1983

Compact Claude cycle refrigerator for laboratory use

A Claude cycle refrigerator with a three stage reciprocating expansion engine is described. Instead of a cam mechanism, valves are driven directly by magnetic solenoids operated by means of a micro processor control system. A swash plate mechanism is used to convert reciprocating motion of the expander pistons to rotary motion. A refrigeration capacity of 8 watts was achieved at 4.5 K with the operating pressure of 1.1 MPa and flow rate of 2.4 g/sec.. An effect of overintake operation was studied. Experimental results show that the efficiency of the expander has a peak point in the region of overintake operation with constant cycle speed, which agrees with theoretical results. The electrically controlled valve system is useful to vary the valve timing to achieve an optimum condition of operation.

Hiersaki, Y.↗