Results for “low temperature drying” — Page 16

NASA NTRS1979

Ultrafine polybenzimidazole (PBI) fibers

Mats were made from ultrafine polybenzimidazole (PBI) fibers to provide an alternate to the use of asbestos as separators in fuel cells and alkaline batteries. To minimize distortion during mat drying, a process to provide a dry fibrid was developed. Two fibrid types were developed: one coarse, making mats for battery separators; the other fine, making low permeability matrices for fuel cells. Eventually, it was demonstrated that suitable mat fabrication techniques yielded fuel cell separators from the coarser alkaline battery fibrids. The stability of PBI mats to 45% KOH at 123 C can be increased by heat treatment at high temperatures. Weight loss data to 1000 hours exposure show the alkali resistance of the mats to be superior to that of asbestos.

Chenevey, E. C.↗

NASA NTRS2021

On Assessing ERA5 and MERRA2 Representations of Cold-Air Outbreaks Across the Gulf Stream

The warm Gulf Stream sea surface temperatures (SSTs) strongly impact the evolution of winter clouds behind atmospheric cold fronts. Such cloud evolution remains challenging to model. The Gulf Stream is too wide within the ERA5 and MERRA2 reanalyses, affecting the turbulent surface fluxes. Known problems within the ERA5 boundary layer (too-dry and too-cool with too strong westerlies), ascertained primarily from ACTIVATE 2020 campaign aircraft dropsondes and secondarily from older buoy measurements, reinforce surface flux biases. In contrast, MERRA2 winter surface winds and air-sea temperature/humidity differences are slightly too weak, producing surface fluxes that are too low. Reanalyses boundary layer heights in the strongly-forced winter cold-air-outbreak regime are realistic, whereas late-summer quiescent stable boundary layers are too shallow. Nevertheless, the reanalysis biases are small, and reanalyses adequately support their use for initializing higher-resolution cloud process modeling studies of cold-air outbreaks.

Gulf stream↗

NASA NTRS1982

Tribological characteristics of nitrogen (N+) implanted iron

The effect of implantation of nitrogen ions (1.5 MeV) on the friction and wear characteristics of pure ion sliding against M-50 steel (unimplanted) was studied in a pin-on-disk sliding friction apparatus. Test conditions included room temperature (25 C), a dry air atmosphere, a load of 1/2 kg (4.9 N), sliding velocities of 0.043 to 0.078 m/sec (15 to 25 rpm), a pure hydrocarbon lubricant (n-hexadecane), or a U.S.P. mineral oil and nitrogen ion implantation doses of 5x10 to the 15th power and 5x10 to the 17th power ions/sq cm. No differences in wear rates were observed in the low dose experiments. In the high dose experiments, small reductions in initial (40 percent) and steady state (20 percent) wear rates were observed for nitrogen implanted iron riders as compared with unimplanted controls. No differences in average friction coefficients were noted for either dose. Auger electron spectroscopy combined with argon ion bombardment revealed a subsurface Gaussian nitrogen distribution with a maximum concentration of 6 atomic percent at a depth of 0.8 microns. Similar analysis within the wear scar of an implanted rider after 20 microns of wear yielded only background nitrogen concentration. No inward migration of nitrogen ions was observed.

Jones, W. R.↗

NASA NTRS1983

Tribological characteristics of nitrogen (N+) implanted iron

The effect of implantation of nitrogen ions (1.5 MeV) on the friction and wear characteristics of pure ion sliding against M-50 steel (unimplanted) was studied in a pin-on-disk sliding friction apparatus. Test conditions included room temperature (25 C), a dry air atmosphere, a load of 1/2 kg (4.9 N), sliding velocities of 0.043 to 0.078 m/sec (15 to 25 rpm), a pure hydrocarbon lubricant (n-hexadecane), or a U.S.P. mineral oil and nitrogen ion implantation doses of 5x10 to the 15th power and 5x10 to the 17th power ions/sq cm. No differences in wear rates were observed in the low dose experiments. In the high dose experiments, small reductions in initial (40 percent) and steady state (20 percent) wear rates were observed for nitrogen implanted iron riders as compared with unimplanted controls. No differences in average friction coefficients were noted for either dose. Auger electron spectroscopy combined with argon ion bombardment revealed a subsurface Gaussian nitrogen distribution with a maximum concentration of 6 atomic percent at a depth of 0.8 microns. Similar analysis within the wear scar of an implanted rider after 20 microns of wear yielded only background nitrogen concentration. No inward migration of nitrogen ions was observed. Previously announced in STAR as N82-24322

Jones, W. R., Jr.↗

NASA NTRS1989

A solution to water vapor in the National Transonic Facility

As cryogenic wind tunnels are utilized, problems associated with the low temperature environment are being discovered and solved. Recently, water vapor contamination was discovered in the National Transonic Facility, and the source was shown to be the internal insulation which is a closed-cell polyisocyanurate foam. After an extensive study of the absorptivity characteristics of the NTF thermal insulation, the most practical solution to the problem was shown to be the maintaining of a dry environment in the circuit at all times. Utilizing a high aspect ratio transport model, it was shown that the moisture contamination effects on the supercritical wing pressure distributions were within the accuracy of setting test conditions and as such were considered negligible for this model.

Gloss, Blair B.↗

NASA NTRS1989

Uranus deep atmosphere revealed

The present examination of the radio spectrum and latitudinal radio brightness temperature variation of Uranus leads to a ejection of thermochemical equilibrium models and the adoption of an atmospheric model characterized by a low ammonia volume-mixing ratio that is uniformly distributed over a wide altitude range. The elemental ratios derivable from this model support the planetary accretion theory of Pollack and Bodenheimer (1989). It is noted that while the equatorial and midlatitude values of Uranian radio brightness temperature are explainable by condensation theories, the polar value can only be accounted for through the invocation of strong, dry air downdrafts.

De Pater, Imke↗

NASA NTRS2012

Validation of MIPAS IMK-IAA Temperature, Water Vapor, and Ozone Profiles with MOHAVE-2009 Campaign Measurements

MIPAS observations of temperature, water vapor, and ozone in October 2009 as derived with the scientific level-2 processor run by Karlsruhe Institute of Technology (KIT), Institute for Meteorology and Climate Research (IMK) and CSIC, Instituto de Astrofısica de Andalucıa (IAA) and retrieved from version 4.67 level-1b data have been compared to co-located field campaign observations obtained during the MOHAVE-2009 campaign at the Table Mountain Facility near Pasadena, California in October 2009. The MIPAS measurements were validated regarding any potential biases of the profiles, and with respect to their precision estimates. The MOHAVE-2009 measurement campaign provided measurements of atmospheric profiles of temperature, water vapor/relative humidity, and ozone from the ground to the mesosphere by a suite of instruments including radiosondes, ozonesondes, frost point hygrometers, lidars, microwave radiometers and Fourier transform infrared (FTIR) spectrometers. For MIPAS temperatures (version V4O_T_204), no significant bias was detected in the middle stratosphere; between 22 km and the tropopause MIPAS temperatures were found to be biased low by up to 2 K, while below the tropopause, they were found to be too high by the same amount. These findings confirm earlier comparisons of MIPAS temperatures to ECMWF data which revealed similar differences. Above 12 km up to 45 km, MIPAS water vapor (version V4O_H2O_203) is well within 10% of the data of all correlative instruments. The well-known dry bias of MIPAS water vapor above 50 km due to neglect of non-LTE effects in the current retrievals has been confirmed. Some instruments indicate that MIPAS water vapor might be biased high by 20 to 40% around 10 km (or 5 km below the tropopause), but a consistent picture from all comparisons could not be derived. MIPAS ozone (version V4O_O3_202) has a high bias of up to +0.9 ppmv around 37 km which is due to a non-identified continuum like radiance contribution. No further significant biases have been detected. Cross-comparison to co-located observations of other satellite instruments (Aura/MLS, ACE-FTS, AIRS) is provided as well.

MIPAS validation↗

DOE OSTI2022

The Mechanical Response of High Burnup 17x17 PWR Fuel Rods Under Bending

As a part of the US Department of Energy Office of Nuclear Energy High Burnup Spent Fuel Data Project, Oak Ridge National Laboratory has performed 4pt-bend tests on a series of 17x17 PWR fuel rods that were discharged with rod average burnups between 50 and 60 GWd/MTU. The rods include four different kinds of fuel cladding: standard Zircaloy-4 (Zirc-4), low-tin (LT) Zirc-4, ZIRLO, and M5. Six rods of each type (combining Zirc-4 and LT Zirc-4 as one type) were tested to failure at room temperature and 200 oC. Three of each type experienced a full-length heat treatment cycle from RT to 400 oC to RT with an 8 hr soak at 400 oC to simulate the expected limiting vacuum drying condition, which potentially induces hydride reorientation and causes some annealing of irradiation damage in the cladding. Overall, the fuel rods show significant capacity to deflect in bending and exhibit non-linear deformation before failing. The calculated failure strains range from 1.5% to 3.8%. The simulated vacuum drying heat treatment had the largest effect on fuel rods with ZIRLO and M5 cladding. In both cases the heat treatment caused increases in the plastic strain at failure, suggesting some annealing of irradiation damage is occurring. The finite element modeling of the 4pt bending test assume the pellet is a collection of pellet wedge pieces. The results for the Zircaloy-4 rods suggest that the pellets are bonded to the cladding and friction controls the relative motion of the pellet wedge pieces.

Cantonwine, Paul↗

NASA NTRS1979

The origins and early histories of planetary atmospheres

Ancient dry river beds detected on Mars by the Viking spacecraft suggest that the early Martian atmosphere may have been much more massive than at present. Degassing of a late-accreting, volatile-rich veneer may account for the primitive atmosphere of both Mars and earth. The primitive earth atmosphere could have produced a greenhouse effect sufficient to maintain temperatures above 273 K without NH3 and with low solar luminosity. The Venutian veneer, according to preliminary Pioneer results, was probably richer in noble gases relative to carbon and nitrogen than were the Martian and earth veneers. The highly evolved atmosphere of Titan, the large satellite of Saturn, is also discussed.

Owen, T.↗

NASA NTRS1984

Mesoscale analysis of VAS 6.7 micron image data for several case studies

Several case studies are examined in an attempt to relate Visible infrared spin scan radiometers Atmospheric Sounder (VAS) water vapor channel radiance data to atmospheric moisture. Since the 6.7 micrometer channel detects radiation emitted by atmospheric water vapor from a rather thick layer, a scheme is developed which weighted rawinsonde observations of relative humidity in a similar manner. A comparison of the two fields (weighted relative humidity values from gridded rawinsonde observations and the VAS water vapor image) indicates that even when mesoscale data are used, the technique only presented a smooth representation of the radiance field. This weighting function is dependent on both the temperature and moisture distribution of the atmosphere. Cross sections of relative humidity from the mesoscale rawinsondes are produced which sliced the water vapor imagery in particularly interesting regions (areas of high and low blackbody temperatures). Comparisons are then made between the cross sections and the variations in the VAS radiance data along the cross section line. Bright regions in the water vapor imagery (cold blackbody temperatures) are often associated with thin layers of high relative humidity or thick layers of only moderately moist air. The reverse also applies, i.e., dark regions (warm blackbody temperatures) in the imagery corresponded well with very dry regions in the cross sections.

Jedlovec, G. J.↗

NASA NTRS1984

Mesoscale analysis of 6.7 micron image data from the VISSR Atmospheric Sounder (VAS) for several case studies

Several case studies are examined in an attempt to relate Visible infrared spin scan radiometers Atmospheric Sounder (VAS) water vapor channel radiance data to atmospheric moisture. Since the 6.7 micrometer channel detects radiation emitted by atmospheric water vapor from a rather thick layer, a scheme is developed which weighted rawinsonde observations of relative humidity in a similar manner. A comparison of the two fields (weighted relative humidity values from gridded rawinsonde observations and the VAS water vapor image) indicates that even when mesoscale data are used, the technique only presented a smooth representation of the radiance field. This weighting function is dependent on both the temperature and moisture distribution of the atmosphere. Cross sections of relative humidity from the mesoscale rawinsondes are produced which sliced the water vapor imagery in particularly interesting regions (areas of high and low blackbody temperatures). Comparisons are then made between the cross sections and the variations in the VAS radiance data along the cross section line. Bright regions in the water vapor imagery (cold blackbody temperatures) are often associated with thin layers of high relative humidity or thick layers of only moderately moist air. The reverse also applies, i.e., dark regions (warm blackbody temperatures) in the imagery corresponded well with very dry regions in the cross sections.

Jedlovec, G. J.↗

NASA NTRS2001

Idealized Simulations of the Effects of Amazon Convection and Baroclinic Waves on the South Atlantic Convergence Zone

The South Atlantic Convergence Zone (SACZ) is a NW-SE oriented, stationary region of enhanced convergence and convection that extends southeastward from the ITCZ convection anchored over the Amazon region. On daily satellite images each SACZ episode is seen as a progression of one or several midlatitude cold fronts that intrude into the subtropics and tropics, becoming stationary over southeastern Brazil for a few days. Previous studies have shown that while Amazon convection plays a fundamental role in the formation of the SACZ, Atlantic sea surface temperatures and the Andes Mountains play a relatively minor role in the strength and location of the SACZ. The role of interactions between Amazon convection and midlatitude baroclinic waves in establishing the origin, position, and maintenance of the SACZ is studied here using idealized dry, multilayer global model simulations that do not include the effects of topography. The model simulations produce SACZ-like regions of low-level convergence in the presence of Amazon convection embedded in a mean-flow that contains propagating baroclinic waves. The results of these simulations indicate that Amazon convection plays two fundamental roles in the formation and location of the SACZ. First, it produces a NW-SE oriented region of low-level convergence to the SE of Amazon convection. Second, it produces a storm-track region and accompanying stronger midlatitude baroclinic waves in the region of the SACZ. It is suggested that in the presence of moist effects, the 'seedling' SACZ regions produced in these simulations can be enhanced to produce the observed SACZ.

Ferreira, Rosana Nieto↗

NASA NTRS2003

A Mechanism for Recent Production of Liquid Water on Mars

Though Mars is a cold, dry planet, with respect to the thermal stability of liquid water at low altitudes it is not terribly different from comparably cold places on Earth. In dry air such water would evaporate faster on Mars, at a rate comparable to a 60 C hot spring on Earth, but the heat loss associated with that evaporation would be mitigated by the poor thermal convection in the thin Martian air. Even at higher altitudes where the atmospheric pressure does not reach the triple point of water, liquid water might theoretically exist in a low-vapor pressure form such as wet soil, in a briny solution, or simply under a layer of dust or snow. The theoretical stability of liquid water does not suggest its occurrence, either on Mars or in Antarctica. In fact, global models have suggested that locations capable of providing sufficient heat for melting are, precisely for that reason, too dry for water to be present. However, the temperature of irregular local structures such as trenches or craters can be markedly warmer than those of the uniform surfaces of global models. The work described here suggests a plausible scenario in which seasonal liquid water might be produced locally, in sheltered locations, through a process of condensation, cold-trapping, buffering, and melting. While the amounts produced in the present climate would be small, copious amounts of meltwater may have been produced at other phases of the orbital cycle, as recently as 20,000 years ago.

Hecht, M. H.↗

NASA NTRS2014

Compact Multi-Gas Monitor for Life Support Systems Control in Space: Evaluation Under Realistic Environmental Conditions

Advanced space life support systems require lightweight, low-power, durable sensors for monitoring critical gas components. A luminescence-based optical flow-through cell to monitor carbon dioxide, oxygen, and humidity has been developed and was demonstrated using bench top instrumentation under environmental conditions relevant to portable life support systems, including initially pure oxygen atmosphere, pressure range from 3.5 to 14.7 psi, temperature range from 50 F to 150 F, and humidity from dry to 100% RH and under liquid water saturation. This paper presents the first compact readout unit for these optical sensors, designed for the volume, power, and weight restrictions of a spacesuit portable Life support system and the analytical characterization of the optical sensors interrogated by the novel optoelectronic system. Trace gas contaminants in a space suit, originating from hardware and material off-gassing and crew member metabolism, are from many chemical families. The result is a gas mix much more complex than the pure oxygen fed into the spacesuit, which may interfere with gas sensor readings. The paper also presents an evaluation of optical sensor performance when exposed to the most significant trace gases reported to be found in spacesuits. The studies were conducted with the spacecraft maximum allowable concentrations for those trace gases and the calculated 8-hr. concentrations resulting from having no trace contaminant control system in the ventilation loop. Finally, a profile of temperature, pressure, humidity, and gas composition for a typical EVA mission has been defined, and the performance of sensors operated repeatedly under simulated EVA mission conditions has been studied.

Delgado, Jesus↗

DOE OSTI2021

A Parameterization of Turbulent Dissipation and Pressure Damping Time Scales in Stably Stratified Inversions, and its Effects on Low Clouds in Global Simulations

Abstract It is difficult for coarse‐resolution global models of the atmosphere to accurately simulate the observed distribution of low clouds. In particular, it is difficult for moist turbulence closure models to simulate sufficiently bright near‐coastal stratocumulus (Sc) without simulating overly bright marine shallow cumuli (Cu). To parameterize bright Sc, a turbulence parameterization must damp the turbulent fluxes of heat and moisture above cloud top in order to prevent excessive entrainment of dry air into cloud top. To parameterize dim shallow Cu, the subgrid variances of temperature and moisture must remain large, in order to permit partial cloudiness. However, damping the fluxes but not the variances just above cloud top is difficult if a parameterization uses a single “master” time scale to damp both. In nature, the above‐cloud fluxes are damped by pressure fluctuations, whereas scalar variances are damped by a different process, namely, turbulent dissipation. In a stably stratified inversion above cloud, pressure damping is large but turbulent dissipation is small. To avoid this problem, a multitime scale parameterization for damping has been developed. The damping parameterization has been implemented in a global model and evaluated. The parameterization is capable of dimming shallow Cu while producing adequately bright Sc.

54 ENVIRONMENTAL SCIENCES↗

NASA NTRS1977

Low-temperature thermionic emitter

An improved photodelineatable cathode material is disclosed comprising a combination of triple carbonate (TC) and a hydrocarbon polymeric photoresist PR. A mixture of TC powder and PR is applied to a cathode by spraying, spinning or dipping and is then subjected to activation at a temperature from about 800.degree. C up to the melting temperature. The cathodes can be activated at a temperature as low as 800.degree. C and still deliver a 0-field, temperature-limited current density of 750 milliamperes per sq. centimeter at 600.degree. C. If a pattern is desired, the coating is exposed through a suitable mask to actinic light to harden the photoresist in the desired areas. Following exposure, the exposed image areas are developed and the unexposed portions of the coating are removed with solvent. When dry, the cathode is ready for activation.

Remington, Richard W.↗

DOE OSTI2020

Multi-Element Water Content System Instrument Handbook

The SEA Model WCM-2000 multi-element water content system was designed to provide aircraft and wind tunnel users with a single, rugged sensor to simultaneously measure liquid water content (LWC), total water content (TWC), and ice water content (IWC). The instrument consists of four heated stainless steel elements, each with a different shape or size. Each element is directly heated by low-voltage DC current flowing through the element. These elements are maintained at a constant temperature, typically 140°C, by a digital closed-loop control system. Three of the heated elements are exposed directly to the airstream and incoming cloud water. A fourth element, the reference/comp element, is arranged to be exposed to the airflow but not to incoming cloud water. This element is used to establish the “dry power term” that is subtracted from the other three elements’ power readings to establish the measured water content.

54 ENVIRONMENTAL SCIENCES↗

NASA NTRS1980

Refraction of microwave signals by water vapor

Tropospheric water vapor causes a refractive path length effect which is typically 5-10% of the 'dry' tropospheric effect and as large as several meters at elevation angles below 5 deg. The vertical water vapor profile is quite variable, and measurements of intensive atmospheric parameters such as temperature and humidity limited to the surface do not adequately predict the refractive effect. It is suggested that a water vapor refraction model that is a function of the amount of precipitable water alone can be successful at low elevation angles. From an extensive study of numerical ray tracings through radiosonde balloon data, such a model has been constructed. The model predicts the effect at all latitudes and elevation angles between 2 and 10 deg to an accuracy of better than 4% (11 cm at 3 deg elevation angle).

Goldfinger, A. D.↗