Pressure effects on postulated lunar materials.
Thermal conductivity of solid, porous and powder rocks and minerals at subnormal temperatures and pressures with respect to lunar surface material
LUNAR SURFACE↗
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Results for “Effective thermal conductivity”
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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Analysis of the diffusion-dominated thermionic converter plasma.
J-V characteristics of diffusion dominated cesium thermionic converter plasma, describing electron thermal conductivity and volume ionization effects
Bornhorst, W.↗
Multilayer high performance insulation materials
A number of tests are required to evaluate both multilayer high performance insulation samples and the materials that comprise them. Some of the techniques and tests being employed for these evaluations and some of the results obtained from thermal conductivity tests, outgassing studies, effect of pressure on layer density tests, hypervelocity impact tests, and a multilayer high performance insulation ambient storage program at the Kennedy Space Center are presented.
Stuckey, J. M.↗
Assessment of crack growth in a space shuttle main engine first-stage, high-pressure fuel turbopump blade
A two-dimensional finite element fracture mechanics analysis of a space shuttle main engine (SSME) turbine blade firtree was performed using the MARC finite element code. The analysis was conducted under combined effects of thermal and mechanical loads at steady-state conditions. Data from a typical engine stand cycle of the SSME were used to run a heat transfer analysis and, subsequently, a thermal structural fracture mechanics analysis. Temperature and stress contours for the firtree under these operating conditions were generated. High stresses were found at the firtree lobes where crack initiation was triggered. A life assessment of the firtree was done by assuming an initial and a final crack size.
Abdul-Aziz, Ali↗
Thermal history of comets during residence in the Oort cloud - Effect of radiogenic heating in combination with the very low thermal conductivity of amorphous ice
The thermal history of long-period comets initially composed of amorphous ice is studied. It is shown that such comets with a small nucleus thermal conductivity (kappa) experience a runaway increase in the internal temperature during residence in the Oort cloud. The temperature increase is a result of rapid release of the latent heat at crystallization triggered by gradual heating due to decay of radioactive nuclides. The time of the runaway temperature increase is about ten to a hundred million years after the formation of the nucleus depending on the fraction of refractory grains which contain radioactive nuclides. Most of the amorphous ice in the nuclides except just beneath the surface transforms into crystalline ice due to the runaway temperature increase. This implies that the ice in short-period comets is crystalline from the initial time when the long-period comet becomes a short-period one. In comets with large kappa the temperature does not rise much compared to the small kappa case and the initial amorphous ice is preserved. A criterion for the crystallization of the nucleus ice is derived.
Haruyama, Jun'ichi↗
Target compressions by working fluids driven with solid liner implosions
Compression by a spherical solid liner of a gold target surrounded by a hydrogen plasma is simulated. Two-dimensional simulations that treat only a subset of the physics included in the one-dimensional code were performed in an attempt to assess multidimensional effects. A one-dimensional numerical code has been developed to study the effects of thermal radiation and conduction. Results of pressure, density, and energy deposited for different initial plasma conditions are presented and discussed. Results from both one- and two-dimensional codes show that the average target density at peak compression is 39-43 g/cu cm, using the SHIVA Star facility at 90 kV discharge.
Chiang, P.-R.↗
Director's Discretionary Fund Report for Fiscal Year 1996
Topics covered include: Waterproofing the Space Shuttle tiles, thermal protection system for Reusable Launch Vehicles, computer modeling of the thermal conductivity of cometary ice, effects of ozone depletion and ultraviolet radiation on plants, a novel telemetric biosensor to monitor blood pH on-line, ion mobility in polymer electrolytes for lithium-polymer batteries, a microwave-pumped far infrared photoconductor, and a new method for measuring cloud liquid vapor using near infrared remote sensing. Also included: laser-spectroscopic instrument for turbulence measurement, remote sensing of aircraft contrails using a field portable imaging interferometer, development of a silicon-micromachined gas chromatography system for determination of planetary surface composition, planar Doppler velocimetry, chaos in interstellar chemistry, and a limited pressure cycle engine for high-speed output.
Source record↗
Streamer Evaporation
Evaporation is the consequence of heating near the top of streamers in ideal Magnetohydrodynamics (MHD) models, where the plasma is weakly contained by the magnetic field. Heating causes slow opening of field lines and release of new solar wind. It was discovered in simulations and, due to the absence of loss mechanisms, the ultimate end point is the complete evaporation of the streamer. Of course streamers do not behave in this way because there are losses by thermal conduction and radiation. Physically, heating is also expected to depend on ambient conditions. We use our global MHD model with thermal conduction to examine the effect of changing the heating scale height. We also apply and extend an analytic model of streamers developed by Pneuman (1968) to show that steady streamers are unable to contain plasma for temperatures near the cusp greater than approximately 2 x 10(exp 6) K.
Suess, S. T.↗
Steady State Transportation Cooling in Porous Media Under Local, Non-Thermal Equilibrium Fluid Flow
An analytical solution to the steady-state fluid temperature for 1-D (one dimensional) transpiration cooling has been derived. Transpiration cooling has potential use in the aerospace industry for protection against high heating environments for re-entry vehicles. Literature for analytical treatments of transpiration cooling has been largely confined to the assumption of thermal equilibrium between the porous matrix and fluid. In the present analysis, the fundamental fluid and matrix equations are coupled through a volumetric heat transfer coefficient and investigated in non-thermal equilibrium. The effects of varying the thermal conductivity of the solid matrix and the heat transfer coefficient are investigated. The results are also compared to existing experimental data.
Rodriquez, Alvaro Che↗
Cooling of Gas Turbines: Computed Temperature Distribution Through Cross Section of Water-Cooled Turbine Blade - 6
A theoretical analysis of the cross-sectional temperature distribution of a water-cooled turbine blade was made using the relaxation method to solve the differential equation derived from the analysis. The analysis was applied to specific turbine blade and the studies icluded investigations of the accuracy of simple methods to determine the temperature distribution along the mean line of the rear part of the blade, of the possible effect of varying the perimetric distribution of the hot gas-to -metal heat transfer coefficient, and of the effect of changing the thermal conductivity of the blade metal for a constant cross sectional area blade with two quarter inch diameter coolant passages.
Livingood, John N. B.↗
Preparation and Thermoelectric Properties of p- and n-type IrSb(sub 3)
IrSb(sub 3) belongs to a large family of compounds with the skutterudite crystal structure (CoAs(sub 3)).
seebeck coefficient electrical resistivity thermal↗
Electron Energetics in the Martian Dayside Ionosphere: Model Comparisons with MAVEN Data
This paper presents a study of the energetics of the dayside ionosphere of Mars using models and data from several instruments on board the Mars Atmosphere and Volatile EvolutioN spacecraft. In particular, calculated photoelectron fluxes are compared with suprathermal electron fluxes measured by the Solar Wind Electron Analyzer, and calculated electron temperatures are compared with temperatures measured by the Langmuir Probe and Waves experiment. The major heat source for the thermal electrons is Coulomb heating from the suprathermal electron population, and cooling due to collisional rotational and vibrational CO2 dominates the energy loss. The models used in this study were largely able to reproduce the observed high topside ionosphere electron temperatures (e.g., 3000 K at 300 km altitude) without using a topside heat flux when magnetic field topologies consistent with the measured magnetic field were adopted. Magnetic topology affects both suprathermal electron transport and thermal electron heat conduction. The effects of using two different solar irradiance models were also investigated. In particular, photoelectron fluxes and electron temperatures found using the Heliospheric Environment Solar Spectrum Radiation irradiance were higher than those with the Flare Irradiance Spectrum Model-Mars. The electron temperature is shown to affect the O2(+) dissociative recombination rate coefficient, which in turn affects photochemical escape of oxygen from Mars.
magnetic topology↗
Monolithic Trace-Contaminant Sorbents Fabricated from 3D-Printed Polymer Precursors
The current trace-contaminant (TC) removal technology for use in Extravehicular Activities (EVAs) involves the use of a packed bed of acid-impregnated granular charcoal, which is difficult to regenerate. In this paper, results are presented on the development of vacuum-regenerable TC sorbents for use in the Portable Life Support System (PLSS). The sorbents are derived from 3D-printed polymer monoliths (e.g., honeycomb structures), which are then carbonized and activated in order to develop porosity, and also to enhance the TC-sorption capacity. Results are presented on the following aspects of carbon-sorbent development: (1) precursor selection; (2) monolith fabrication; (3) shape retention and strength; (4) carbon surface and porosity characterization; (5) TC-sorption capacity and vacuum-regeneration; (6) pressure drop; and (7) sub-scale sorbent prototype. The use of predominantly microporous monolithic carbon is associated with the following benefits: (a) high TC-sorption capacity; (b) low pressure drop; (c) rapid vacuum (pressure-swing) desorption due to thin monolith walls and low pressure drop; (d) good thermal management (high thermal conductivity and low adsorption/desorption thermal effects associated with physisorption); and (e) good resistance to dusty environments.
Portable Life Support System (PLSS)↗
Thermal Insulation Performance of Textile Structures for Spacesuit Applications at Martian Pressure and Temperature
Protection of astronauts from the extreme temperatures in the space environment has been provided in the past using multi-layer insulation in ultra-high vacuum environments of low earth orbit and the lunar surface. For planetary environments with residual gas atmospheres such as Mars with ambient pressures between 8 to 14 hPa (8 to 14 mbar), new protection techniques are required because of the dominating effect of the ambient gas on heat loss through the insulation. At Mars ambient pressure levels, the heat loss can be excessive at expected suit external temperatures of 172 K with state-of-the-art suit insulation, requiring an active heat source and its accompanying weight and volume penalties. Micro-fibers have been identified as one potential structure to reduce the heat losses, but existing fundamental data on fiber heat transfer at low pressure is lacking for integrated fabric structures. This baseline study presents insulation performance test data at different pressures and fabric loads for selected polyesters and aramids as a function of fiber density, fiber diameter, fabric density, and fabric construction. A set of trend data of thermal conductivity versus ambient pressure is presented for each fiber and fabric construction design to identify the design effects on thermal conductivity at various ambient pressures, and to select a fiber and fabric design for further development as a suit insulation. The trend data also shows the pressure level at which thermal conductivity approaches a minimum, below which no further improvement is possible for a given fiber and fabric design. The pressure levels and resulting thermal conductivities from the trend data can then be compared to the ambient pressure at a planetary surface, Mars for example, to determine if a particular fiber and fabric design has potential as a suit insulation.
Orndoff, Evelyne↗
Effect of time and spatial domains on monolayer 2D material interface thermal conductance measurement using ns ET-Raman
Raman-based approaches to characterizing thermal properties of nanoscale and microscale materials have proven to be powerful experimental methods. Here, this work explores the potential of energy-transport state-resolved Raman (ET-Raman) for the precise determination of interfacial thermal conductance (G) between monolayer 2D materials and their substrates. ET-Raman employs a continuous wave laser and nanosecond (ns) pulsed laser to induce both steady state and transient heating while simultaneously collecting 2D material temperature information from the Raman signal. A 3D numerical model built using the finite volume method simulates the two differentiated thermal transport processes. The simulated temperature rises are compared with experimental Raman temperature information to extract G. In this study, we investigate the temporal effects of the pulse frequency and pulse width of the ns laser on precise characterization of G. By running multiple simulations for a range of pulsed laser frequencies and pulse widths, we determine that ET-Raman is most sensitive to precise interfacial thermal conductance measurements with short pulse widths (~below 20 ns) and with pulsing frequencies that ensure sufficient cooling time between consecutive pulses (~below 500 kHz). We also conclude that substrate thickness and laser spot size play critical roles in heat distribution and subsequent sensitivity to meaningful G measurements. As both laser spot size and SiO 2 substrate thickness decrease, detection of interfacial thermal transport becomes more difficult. These results offer essential guidance in the design of future Raman-based approaches to thermal measurements using pulsed lasers.
2D materials↗
An Instrumented Capsule Design to Measure Thermal Conductivity in Miniature UO2 Specimens
Numerous separate effects irradiations of miniature nuclear fuel specimens have been conducted in the High Flux Isotope Reactor (HFIR) under the experimental platform designated as MiniFuel. MiniFuel is a static irradiation capability in which microstructural evolution and fuel performance phenomena are observed during postirradiation examination thereby offering a snapshot of the terminal fuel characteristics. This approach inherently requires fielding an irradiation where the experimental conditions are determined using predictive models and the pertinent outcomes are measured at the end of the test. Static irradiations can provide useful insights to the relationships between fuel performance and the pivotal irradiation conditions, namely temperature and burnup, but the ability to monitor fuel performance in situ would further support fuel development and qualification. To this end, an instrumented experiment design is being developed at Oak Ridge National Laboratory to capture thermal conductivity degradation and fission gas release during HFIR irradiation. These phenomena will be monitored using unique capsule designs that each target a different phenomenon. This paper details the thermal conductivity capsule (TCC) design and its expected performance envelope as determined using computer models. Each TCC will contain a miniature UO2 disc specimen (~0.5 mm thick × 5 mm diameter) sandwiched between metallic slugs with embedded thermocouples. The coupling of in situ temperature measurements, known thermal conductivity of the metallic components, and heat generation rates computed using high-fidelity neutronics models make the thermal conductivity measurement possible. This paper describes the reactor physics and heat transfer models used to predict the capsule’s performance and the methodology for calculating the fuel specimen’s thermal conductivity from the thermocouple measurements.
Gorton, Jacob [ORNL] (ORCID:0000000269806083)↗
Impact Foam Testing for Multi-Mission Earth Entry Vehicle Applications
Multi-Mission Earth Entry Vehicles (MMEEVs) are blunt-body vehicles designed with the purpose of transporting payloads from outer space to the surface of the Earth. To achieve high-reliability and minimum weight, MMEEVs avoid use of limited-reliability systems, such as parachutes and retro-rockets, instead using built-in impact attenuators to absorb energy remaining at impact to meet landing loads requirements. The Multi-Mission Systems Analysis for Planetary Entry (M-SAPE) parametric design tool is used to facilitate the design of MMEEVs and develop the trade space. Testing was conducted to characterize the material properties of several candidate impact foam attenuators to enhance M-SAPE analysis. In the current effort, two different Rohacell foams were tested to determine their thermal conductivity in support of MMEEV design applications. These applications include thermal insulation during atmospheric entry, impact attenuation, and post-impact thermal insulation in support of thermal soak analysis. Results indicate that for these closed-cell foams, the effect of impact is limited on thermal conductivity due to the venting of the virgin material gas and subsequent ambient air replacement. Results also indicate that the effect of foam temperature is significant compared to data suggested by manufacturer's specifications.
Glaab, Louis J.↗
Thermal diffusivity of diamond films using a laser pulse technique
Polycrystalline diamond films were deposited using a microwave plasma-enhanced chemical vapor deposition process. A laser pulse technique was developed to measure the thermal diffusivity of diamond films deposited on a silicon substrate. The effective thermal diffusivity of a diamond film on silicon was measured by observing the phase and amplitude of the cyclic thermal waves generated by laser pulses. An analytical model is presented to calculate the effective in-plane (face-parallel) diffusivity of a two-layer system. The model is used to reduce the effective thermal diffusivity of the diamonds/silicon sample to a value for the thermal diffusivity and conductivity of the diamond film. The average effective diffusivity values are 1.47 + or - 0.03 and 1.83 + or - 0.10 yielding thermal diffusivity values of 7.46 + or - 0.90 and 7.33 + or - 0.70 sq cm/s respectively, for the two samples; the calculated thermal con ductivity values are 13.50 and 13.28 W/cmK, which are better than that of type 1a natural diamond. The phase and amplitude measurements give similar results.
Albin, Sacharia↗