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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Design and performance analysis of gas sorption compressors

Compressor kinetics based on gas adsorption and desorption processes by charcoal and for gas absorption and desorption processes by LaNi5 were analyzed using a two-phase model and a three-component model, respectively. The assumption of the modeling involved thermal and mechanical equilibria between phases or among the components. The analyses predicted performance well for compressors which have heaters located outside the adsorbent or the absorbent bed. For the rapidly-cycled compressor, where the heater was centrally located, only the transient pressure compared well with the experimental data.

Chan, C. K.↗
NASA NTRS2023

Effect of the Electrostatic Field due to the Surface Monolayer Metal Atoms on the Dissociation of Homonuclear Diatomic Gases in Gas-Metal Surface Reactions

The present paper examines the role of an electrostatic field generated by the outermost monolayer of metal ions prior to gas adsorption in aiding the dissociation of homonuclear diatomic gas molecules. The interaction of five homonuclear diatomic gases, Cl 2 , F 2 , H 2 , N 2 and O 2 , with several pure metals are examined using Coulomb’s law to calculate the attractive and repulsive forces between the electrons or ions in the gas molecule and the free surface metallic electrons or ions assuming a Bohr model. These calculations demonstrate that the total energy of the electrostatic fields from the metals can exceed the molecular binding energies of Cl 2 , F 2 , and O 2 at some distance from the metallic surface thereby suggesting that these gases interact primarily with the metallic surface in their atomic states after molecular bond dissociation prior to reaction. In contrast, H 2 and N 2 gases do not dissociate prior to reaching the metal surface due to the fact that the effective charge of the gas ions is less than the total electron charge at the outermost electronic shell. The present results correlate linearly with the electrochemical series standard reduction potential as well as with the Pauling electronegativity for several metals.

Gas-metal reactions↗
NASA NTRS1986

Improving adsorption cryocoolers by multi-stage compression and reducing void volume

It is shown that the performance of gas adsorption cryocoolers is greatly improved by using adsorbents with low void volume within and between individual adsorbent particles (reducing void volumes in plumbing lines), and by compressing the working fluid in more than one stage. Refrigerator specific power requirements and compressor volumetric efficiencies are obtained in terms of adsorbent and plumbing line void volumes and operating pressures for various charcoal adsorbents using an analytical model. Performance optimization curves for 117.5 and 80 K charcoal/nitrogen adsorption cryocoolers are given for both single stage and multistage compressor systems, and compressing the nitrogen in two stages is shown to lower the specific power requirements by 18 percent for the 117.5 K system.

Bard, S.↗
NASA NTRS1972

Microphysical, microchemical, and adhesive properties of lunar material. III - Gas interaction with lunar material.

Gas adsorption measurements on an Apollo 12 ultrahigh vacuum-stored sample and Apollo 14 and 15 N2-stored samples, show that the cosmic ray track and solar wind damaged surface of lunar soil is very reactive. Room temperature monolayer adsorption of N2 by the Apollo 12 sample at 0.0001 atm was observed. Gas evolution of Apollo 14 lunar soil at liquid nitrogen temperature during adsorption/desorption cycling is probably due to cosmic ray track stored energy release accompanied by solar gas release from depths of 100-200 nm.

Grossman, J. J.↗
NASA NTRS2004

Separation of Carbon Monoxide and Carbon Dioxide for Mars ISRU

The atmosphere of Mars has many resources that can be processed to produce things such as oxygen, fuel, buffer gas, and water for support of human exploration missions. Successful manipulation of these resources is crucial for safe, cost-effective, and self-sufficient long-term human exploration of Mars. In our research, we are developing enabling technologies that require fundamental knowledge of adsorptive gas storage and separation processes. In particular, we are designing and constructing an innovative, low mass, low power separation device to recover carbon dioxide and carbon monoxide for Mars ISRU (in-situ resource utilization). The technology has broad implications for gas storage and separations for gas-solid systems that are ideally suited for reduced gravitational environments. This paper describes our separation process design and experimental procedures and reports results for the separation of CO2 and CO by a four-step adsorption cycle.

Walton, Krista S.↗
NASA NTRS2017

Mapping the Limitations of Breakthrough Analysis in Fixed-Bed Adsorption

The separation of gases through adsorption plays an important role in the chemical processing industry, where the separation step is often the costliest part of a chemical process and thus worthy of careful study and optimization. This work developed a number of new, archival aspects on the computer simulations used for the refinement and design of these gas adsorption processes: 1. Presented a new approach to fit the undetermined heat and mass transfer coefficients in the axially dispersed plug flow equation and associated balance equations 2. Examined and described the conditions where non-physical simulation results can arise 3. Presented an approach to determine the limits of the axial dispersion and LDF mass transfer terms above which non-physical simulation results occur.

Knox, James Clinton↗
NASA NTRS1971

Physisorption of Ar, Kr, CH4, and N2 on 304 stainless steel at very low pressures.

Determination of physisorption isotherms of these gases on stainless steel by pressure change measurements in very low pressure cryogenic baths where a steel nipple was brought in contact with the test gas at 77 to 90 K in a sealed constant-volume system. The position of the nipple in the gas was changed in such a manner that gas adsorption on a 47.5 sq cm area of the steel surface could be measured. The Dubinin-Radushkevich (DR) equation (1947) was used for an empirical description of isotherms at different temperatures. The mean adsorption energies calculated from the DR plots were 1290, 1545, 1490 and 1903 cal/mol for Ar, Kr, CH4 and N2, respectively, being about 10% higher than the corresponding values on Pyrex.

Troy, M.↗
NASA NTRS1976

The surface structure and composition of 60017,43

A surface fragment of 60017, itself an exposed section of Shadow Rock, has been characterized structurally and chemically using gas adsorption, helium pycnometry, scanning electron microscopy, and Auger and ESCA spectroscopy. The fragment is seen as a partially melted devitrified-glass impact breccia possessing a relatively low surface area, macroporosity, and low absolute density. The fragment appears to be plagioclase-enriched with respect to 60017 and to possess significant surface heterogeneity. Confirmation of the surface reduction of iron was obtained; however, the extent of this reduction varied from point to point. Significant amounts of surface volatiles were also found, and it is hypothesized that these were released during the North Ray cratering event. If this is proved correct, similar volatile concentrations should be found on other North Ray ejecta.

Cadenhead, D. A.↗
NASA NTRS1980

A review of the NASA/OAST cryogenic coolers technology program

Low and ultra low temperature cryogenic cooler systems for future space missions include mechanical, solid cryogen, gas adsorption, superfluid helium, helium-3, and magnetic (adiabatic demagnetization) coolers. Operating lifetimes required vary from a few weeks for a Shuttle/Spacelab mission to as long as nine years for missions to the outer planets. Temperature requirements vary from tens to tenths of kelvin. At the higher temperature, cooling loads for detectors, instruments and associated shields may be as high as 15 watts. The general requirements for low and ultra low temperature and techniques that can be employed to achieve these temperatures at expected heat loads are discussed. The NASA Centers involved in the R & T efforts and the type of cooler systems on which they are focusing their effort are considered as well as the thrust of R & T effort for each cooler type. Projected missions that will use the technology are identified.

Lundholm, J. G., Jr.↗
NASA NTRS1991

Evaluation of Fungal Metabolic Compounds Released to the Air in a Restricted Environment

The metabolic action of selected fungi species on common components of the interior of Space Station Freedom (SSF) will be tested. When present, volatile organic chemicals will be collected on porous polymer adsorbent columns. Using thermal desorption, the volatile compounds will be passed onto a gas chromatographic column for analysis. The Space Station Freedom (SSF) modular complex will largely be individually self contained and the established air environment will not be easily adjusted. The development and maintenance of a safe working environment offers a considerable challenge. Present plans for use of SSF acknowledge periods of manned activities and alternate times when the station is unmanned. The obvious necessity for clean and safe air and water during periods of use have been pursued as fundamental systems to SSF success. Somewhat less obvious, although perhaps of no less importance to the success of long term cyclic usage, are those periods of inactivity. It is during these periods when spores from microorganisms may be afforded the best conditions to germinate and in the vegetative form react with the complex synthetic chemical polymers which compose the furnishings and hardware of SSF nodes. Biodegradation could constitute a real hygiene problem, if the organisms form and release volatile organic chemicals. Similar problems have been documented in closed and improperly ventilated buildings and work spaces. Many of the metabolic products of fungi and bacterial growth create a variety of health problems. Analytical chemical techniques will first be used to document the growth of Aspergillus, Penicillium, and Cladosporium fungal species on the potential substrates Nomex and Kevlar. Any volatile organics that are released will be measured using the spectrum of gas adsorption chromatography. The level of microbial contamination that is necessary to produce such volatile compounds and the relative amounts expected to accumulate will be estimated.

Ferebee, Robert N.↗
NASA NTRS1993

Morphology of nitric acid and water ice films

Ice films have been used to simulate stratospheric cloud surfaces in order to obtain laboratory data on solubilities and heterogeneous reaction rates. In the present study, environmental scanning electron microscopy (ESEM) is used to study thin films of both water ice and nitric acid ice near the composition of the trihydrate. The ices are formed by vapor deposition onto aluminum or borosilicate-glass substrates cooled to about 200 K. Micrographs are recorded during the deposition process and during subsequent annealing at higher temperatures. The results show that the ice films are composed of loosely consolidated granules, which range from about 1 to 20 microns in size at temperatures between 197 and 235 K. Cubic water ice is sometimes observed at 200 K, which converts to the hexagonal form at slightly higher temperatures. The loose packing of the granules confirms the high porosities of these films obtained from separate bulk porosity measurements. Average surface areas calculated from the observed granule sizes range from about 0.2 to 1 sq m/g and agree with surface areas obtained by gas-adsorption (BET) analysis of annealed ice films. For unannealed films, the BET areas are about an order of magnitude higher than the ESEM results, implying that the unannealed ices contain microporosity which is lost during the annealing process.

Keyser, Leon F.↗
NASA NTRS1993

Comprehensive investigation of HgCdTe metalorganic chemical vapor deposition

The principal objective of this experimental and theoretical research program was to explore the possibility of depositing high quality epitaxial CdTe and HgCdTe at very low pressures through metalorganic chemical vapor deposition (MOCVD). We explored two important aspects of this potential process: (1) the interaction of molecular flow transport and deposition in an MOCVD reactor with a commercial configuration, and (2) the kinetics of metal alkyl source gas adsorption, decomposition and desorption from the growing film surface using ultra high vacuum surface science reaction techniques. To explore the transport-reaction issue, we have developed a reaction engineering analysis of a multiple wafer-in-tube ultrahigh vacuum chemical vapor deposition (UHV/CVD) reactor which allows an estimate of wafer or substrate throughput for a reactor of fixed geometry and a given deposition chemistry with specified film thickness uniformity constraints. The model employs a description of ballistic transport and reaction based on the pseudo-steady approximation to the Boltzmann equation in the limit of pure molecular flow. The model representation takes the form of an integral equation for the flux of each reactant or intermediate species to the wafer surfaces. Expressions for the reactive sticking coefficients (RSC) for each species must be incorporated in the term which represents reemission from a wafer surface. The interactions of MOCVD precursors with Si and CdTe were investigated using temperature programmed desorption (TPD) in ultra high vacuum combined with Auger electron spectroscopy (AES). These studies revealed that diethyltellurium (DETe) and dimethylcadmium (DMCd) adsorb weakly on clean Si(100) and desorb upon heating without decomposing. These precursors adsorb both weakly and strongly on CdTe(111)A, with DMCd exhibiting the stronger interaction with the surface than DETe.

Raupp, Gregory B.↗