Airborne observations of contrail effects on the thermal radiation budget
Contrail effects on atmospheric thermal radiation budget in heavy jet traffic regions from airborne IR and solar radiometric observations
Kuhn, P. M.↗
SEARCH · Search NASA
Results for “thermal effect”
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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
System overview on electromagnetic compensation for reflector antenna surface distortion
The system requirements and hardware implementation for electromagnetic compensation of antenna performance degradations due to thermal effects was investigated. Future commercial space communication antenna systems will utilize the 20/30 GHz frequency spectrum and support very narrow multiple beams (0.3 deg) over wide angle field of view (15-20 beamwidth). On the ground, portable and inexpensive very small aperture terminals (VSAT) for transmitting and receiving video, facsimile and data will be employed. These types of communication system puts a very stringent requirement on spacecraft antenna beam pointing stability (less than .01 deg), high gain (greater than 50 dB) and very lowside lobes (less than -25 dB). Thermal analysis performed on the advanced communication technology satellite (ACTS) has shown that the reflector surfaces, the mechanical supporting structures and metallic surfaces on the spacecraft body will distort due thermal effects from a varying solar flux. The antenna performance characteristics (e.g., pointing stability, gain, side lobe, etc.) will degrade due to thermal distortion in the reflector surface and supporting structures. Specifically, antenna RF radiation analysis has shown that pointing error is the most sensitive antenna performance parameter to thermal distortions. Other antenna parameters like peak gain, cross polarization level (beam isolation), and side lobe level will also degrade with thermal distortions. In order to restore pointing stability and in general antenna performance several compensation methods were proposed. In general these compensation methods can be classified as being either of mechanical or electromagnetic type. This paper will address only the later one. In this approach an adaptive phased array antenna feed is used to compensate for the antenna performance degradation. Extensive work has been devoted to demonstrate the feasibility of adaptive feed compensation on space communication antenna systems. This paper addresses the system requirements for such a system and identify candidate technologies (analog and digital) for possible hardware implementation.
Acosta, R. J.↗
Thermal radiation effects in the atmosphere initiated by pre-earthquake processes
The science community is still looking for pre-earthquake indicators of major seismic events in order to minimize the loss of human life. Recent advances in satellite technology have helped to increase the scientific understanding of the nature of pre-earthquake phenomena in the atmosphere and their relationship with transitional thermal anomalies. It was realized that the thermal heat fluxes over areas of earthquake preparation are a result of air ionization by Rn222, its isotopes and progenies and consequent water vapor condensation on newly formed ions. Latent heat (LH) is released as a result of this process and leads to the formation of local thermal radiation anomalies (TRA) known as outgoing longwave radiation (OLR). We recorded data from the most recent major earthquakes in California (2014) Nepal (2015) that allowed us to summaries TRA's main morphological features. It was also established that the TRA is part of a more complex chain of the short‐term earthquake precursors, which are explained within the framework of a Lithosphere-Atmosphere-Ionosphere Coupling (LAIC) model.
Dimitar Ouzounov↗
Multiscale Thermal Conductivity Modeling of 3D Woven Composite Thermal Protection System Materials
Novel thermal protection systems (TPS) for re-entry and hypersonic vehicles utilize 3D woven composite materials with blended carbon filament tows (yarns) and a phenolic resin matrix. The presence of continuous carbon fibers provides superior stiffness and strength compared to legacy TPS, while the 3D weave pattern provides a great deal of design flexibility for both in-plane and through thickness thermomechanical behavior. However, modeling of 3D woven composites is notoriously complex and numerically intensive. The present investigation utilizes a unique ultra-efficient approach, known as Multiscale Recursive Micromechanics (MsRM), wherein recursive semi-analytical micromechanics methods are employed at various length scales within the composite. The MsRM approach has recently been extended to solve for the effective thermal conductivity as well as the local temperature and thermal flux fields throughout the composite. Presented model results focus on the impact of the microstructural geometry representation at each length scale on the material’s effective thermal conductivity, along with the local thermal flux and temperature fields induced in the microstructures, for a novel 3D woven TPS.
Composite↗
Effects of Thermal and Mechanical Processing on Microstructures and Desired Properties of Particle-Strengthened Cu-Cr-Nb Alloys
Ternary Cu-Cr-Nb alloys, particularly Cu-8 Cr-4 Nb (in at.%), have demonstrated good thermal stability as well as high strength and conductivity at elevated temperatures. The initial powder material has a bimodal size distribution of Cr2Nb precipitates. Primary Cr2Nb precipitates are approx. 1 micron, and secondary Cr2Nb particles are 30-200 nm. The particle coarsening was analyzed and found to follow LSW-type behavior, This study provides a detailed examination of the stability and strengthening effects of Cr2Nb particles. This investigation also revealed that the primary particles provide direct grain boundary pinning and indirect grain boundary strengthening but virtually no Orowan strengthening. The secondary particles found within grains do provide Orowan strengthening. For extruded material, grain bound-ary strengthening (Hall-Petch effect) accounts for two-thirds of the strength with Orowan effects contributing the remainder. The proven advantages of Cu-Cr-Nb were the motivation to improve these attributes via microstructural refinement. Mechanical milling (MM) of Cu- 4 Cr-2 Nb and Cu-8 Cr-2 Nb produced an increase in hot pressed Vickers hardness of 122% and 96%, respectively. The increase in hardness was more due to Cu grain-size refinement than to Cr,,Nb refinement. This study also demonstrated enhanced stability of MM Cu-4 Cr-2 Nb. Hot pressed 4 h milled Cu-4 Cr-2 Nb experienced only a 22% drop in hardness when annealed at 1273 K for 50 h versus a 30% drop for extruded Cu-8 Cr-4 Nb. The goal of improving the strength and stability of Cu-4 Cr-2 Nb to better than such properties for as- extruded Cu-8 Cr-4 Nb has been met. In addition, a figure-of-merit (FOM) coupling hardness and thermal conductivity was maximized for the case of 4 h milled Cu-4 Cr-2 Nb material. Overall, Cu-Cr-Nb alloys not only possess high strength, conductivity and thermal stability but also can be further developed to improve strength and stability.
Anderson, Kenneth Reed↗
Tensile properties of SiC/aluminum filamentary composites - Thermal degradation effects
Aluminium metal matrix composites with a low cost fiber, e.g. SiC, provide for an attractive combination of high elastic modulus and longitudinal strengths coupled with a low density. SiC (volume fraction 0.55)-aluminum (6061) systems have been studied in order to optimize fiber composite strength and processing parameters. A comparison of two SiC/aluminum composites produced by AVCO and DWA is provided. Fiber properties are shown to alter composite tensile properties and fracture morphology. The room temperature tensile strengths appear to be insensitive to thermal exposures at 500 C up to 150 h. The elastic modulus of the composites also appears to be stable up to 400 C, however variations in the loss modulus are apparent. The fracture morphology reflects the quality of the interfacial bond, fiber strengths and fiber processing.
Skinner, A.↗
Effects of Thermal Treatment on Tensile Creep and Stress-Rupture Behavior of Hi-Nicalon SiC Fibers
Tensile creep and stress-rupture studies were conducted on Hi-Nicalon SiC fibers at 1200 and 1400 C in argon and air. Examined were as-received fibers as well as fibers annealed from 1400 to 1800 C for 1 hour in argon before testing. The creep and rupture results for these annealed fibers were compared to those of the as-received fibers to determine the effects of annealing temperature, test temperature, and test environment. Argon anneals up to 1500 C degrade room temperature strength of Hi-Nicalon fibers, but improve fiber creep resistance in argon or air by as much as 100% with no significant degradation in rupture strength. Argon anneals above 1500 C continue to improve fiber creep resistance when tested in argon, but significantly degrade creep resistance and rupture strength when tested in air. Decrease in creep resistance in air is greater at 1200 C than at 1400 C. Mechanisms are suggested for the observed behavior.
Yun, H. M.↗
Inelastic deformation and dislocation structure of a nickel alloy - Effects of deformation and thermal histories
Inelastic deformation behavior of the cast Ni-base alloy, B1900 + Hf, was investigated using data from step-temperature tensile tests and thermomechanical cyclic tests in the temperature ranges 538-760 C and 760-982 C. The deformation results were correlated with the dislocation structures of deformed specimens, identified by TEM. It was found that, in the 760-982 C temperature range, there are no thermal history effects in the inelastic deformation behavior of B1900 + Hf. In the 538-760 range, anomalous cyclic hardening and, possibly, thermal history effects were observed in thermomechanically deformed alloy, caused by sessile (010) dislocations in the gamma-prime phase.
Chan, K. S.↗
Effect of thermal cycling on ZrO2-Y2O3 thermal barrier coatings
A study was made of the comparative life of plasma sprayed ZrO2-Y2O3 thermal barrier coatings on NiCrAlY bond coats on Rene 41 in short (4 min) and long (57 min) thermal cycles to 1040 C in a 0.3 Mach flame. Short cycles greatly reduced the life of the ceramic coating in terms of time at temperature as compared to longer cycles. Appearance of the failed coating indicated compressive failure. Failure occurred at the bond coat-ceramic coat junction. At heating rates greater than 550 kw/sq m, the calculated coating detachment stress was in the range of literature values of coating adhesive/cohesive strength. Methods are discussed for decreasing the effect of high heating rate by avoiding compressive stress.
Mcdonald, G.↗
Heat Transfer In High-Temperature Multilayer Insulation
The combined radiation/conduction heat transfer in high-temperature multilayer insulations for typical reentry of reusable launch vehicles from low Earth orbit was investigated experimentally and numerically. The high-temperature multilayer insulation investigated consisted of gold-coated reflective foils separated by alumina fibrous insulation spacers. The steady-state heat transfer through four multilayer insulation configurations was investigated experimentally over the temperature range of 300-1300 K and environmental pressure range of 1.33 10(exp -5)-101.32 kPa. It was shown that including the reflective foils reduced the effective thermal conductivity compared to fibrous insulation sample at 1.5 times the density of the multilayer sample. A finite volume numerical model was developed to solve the governing combined radiation/conduction heat transfer equations. The radiation heat transfer in the fibrous insulation spacers was modeled using the modified two-flux approximation assuming anisotropic scattering and gray medium. The numerical model was validated by comparison with steady-state experimental data. The root mean square deviation between the predicted and measured effective thermal conductivity of the samples was 9.5%.
Daryabeigi, Kamran↗
The calibration of photographic and spectroscopic films. Part 1: Film batch variations of reciprocity failure in IIaO film. Part 2: Thermal and aging effects in relationship to reciprocity failure. P art 3: Shifting of reciprocity failure points as a function of thermal and aging effects
Reciprocity failure was examined for IIaO spectroscopic film. Three separate experiments were performed in order to study film batch variations, thermal and aging effects in relationship to reciprocity failure, and shifting of reciprocity failure points as a function of thermal and aging effects. The failure was examined over ranges of time between 5 and 60 seconds. The variation to illuminance was obtained by using thirty neutral density filters. A standard sensitometer device imprinted the wedge pattern on the film as exposure time was subjected to variation. Results indicate that film batch differences, temperature, and aging play an important role in reciprocity failure of IIaO spectroscopic film. A shifting of the failure points was also observed in various batches of film.
Peters, Kevin A.↗
Electron beam induced damage in ITO coated Kapton
Data for the stability of thin conductive indium tin oxide films on 0.003 inch thick Kapton substrates during exposure of the surface to electron beams are reported. The electron beam energy was 3 keV and the diameter was about 0.8 mm. Thermal effects and surface modifications are considered. For primary current greater than 0.6 microamperes, an obvious dark discoloration with diameter approximately that of the beam was produced. The structure of the discolored region was studied with the scanning electron microscope, and the findings are stated. Surface modifications were explored by AES, obtaining spectra and secondary emission coefficient as a function of time for different beam intensities. In all cases beam exposure results in a decrease of the secondary yield but because of thermal effects this change, as well as composition changes, cannot be directly interpreted in terms of electron beam dosage.
Krainsky, I.↗
Effect of a steady thermal field on the stress concentration in an infinite elastic plane with circular hole
Steady thermal field effect on stress state of infinite elastic plane with circular hole
THERMAL EFFECT↗
Effects of thermal and environmental exposure on the mechanical properties of graphite/polyimide composites
Composites were exposed in circulating and static air environments up to 589 K for a maximum of 1000 hours. Composites of HT-S, HM-S, Thornel 50S, and Fortafil 5-Y fiber and a new addition type polyimide resin were laminated in a matched-die mold. Flexural strengths, flexural modulus, and interlaminar shear strengths were determined at 297, 533, and 598 K after various durations of exposure. Composite and fiber weight loss characteristics were determined by isothermal gravimetric analysis in air. Properties of composites exposed and tested at the environment temperatures were compared with those determined under short-term exposure. A new short beam interlaminar shear fixture is described. Environmental effects of long-term ambient temperature exposure on the elevated temperature mechanical properties of graphite/polyimide composites are presented.
Hanson, M. P.↗
Effects of thermal and environmental exposure on the mechanical properties of graphite/polyimide composites.
Composites were exposed in circulating and static air environments up to 600 F for a maximum of 1000 hours. Composites of HT-S, HM-S, Thornel 50S, and Fortafil 5-Y fiber and a new addition type polyimide resin were laminated in a matched-die mold. Flexural strength, flexural modulus, and interlaminar shear strengths were determined at 75, 500 and 600 F after various durations of exposure. Composite and fiber weight loss characteristics were determined by isothermal gravimetric analysis in air. Properties of composites exposed and tested at the environment temperatures are compared with those determined under short-term exposure. A new short beam interlaminar shear fixture is described. Environmental effects of long-term (up to one year) ambient temperature exposure on the elevated temperature mechanical properties of graphite/polyimide composites are presented.
Hanson, M. P.↗
Delineation of cold-prone areas using nighttime SMS/GOES thermal data Effects of soils and water
Infrared digital data from geostationary satellites were used to demonstrate the usefulness of remotely sensed surface temperature data to delineate microscale and mesoscale climates. Nocturnal winter data (December-February) from 1976-77 to 1978-79 over Florida revealed noticeable contrasts in surface temperature patterns. Colder areas were associated with low soil moisture content in the upper layers of excessively drained and well drained sandy soils, whereas warmer areas were associated with bodies of water, wetlands, or poorly drained soils. An unexpected surface temperature pattern for one night where the north-central Florida climatic zone was colder than the north Florida climatic zone was found to be caused by differences in antecedent frontal rainfall. Differences in surface radiant energy fluxes over these two areas at 0200 EST 20 December 1977, based on average satellite-sensed surface temperatures, were compared with differences in soil heat fluxes that were computed from 1.5 m climatological temperatures and soil thermal properties by use of a simplified surface energy balance equation.
Chen, E.↗
The flare kernel in the impulsive phase
The impulsive phase of a flare is characterized by impulsive bursts of X-ray and microwave radiation, related to impulsive footpoint heating up to 50 or 60 MK, by upward gas velocities (150 to 400 km/sec) and by a gradual increase of the flare's thermal energy content. These phenomena, as well as non-thermal effects, are all related to the impulsive energy injection into the flare. The available observations are also quantitatively consistent with a model in which energy is injected into the flare by beams of energetic electrons, causing ablation of chromospheric gas, followed by convective rise of gas. Thus, a hole is burned into the chromosphere; at the end of impulsive phase of an average flare the lower part of that hole is situated about 1800 km above the photosphere. H alpha and other optical and UV line emission is radiated by a thin layer (approx. 20 km) at the bottom of the flare kernel. The upward rising and outward streaming gas cools down by conduction in about 45 s. The non-thermal effects in the initial phase are due to curtailing of the energy distribution function by escape of energetic electrons. The single flux tube model of a flare does not fit with these observations; instead we propose the spaghetti-bundle model. Microwave and gamma-ray observations suggest the occurrence of dense flare knots of approx. 800 km diameter, and of high temperature. Future observations should concentrate on locating the microwave/gamma-ray sources, and on determining the kernel's fine structure and the related multi-loop structure of the flaring area.
Dejager, C.↗
The Effects of Thermal History on Nucleation of Tetragonal Lysozyme Crystals, or Hot Protein and Cold Nucleation
Chicken egg white lysozyme has a well characterized thermally driven phase transition. Between pH 4.2 and 5.2, the transition temperature, as defined by the point where the tetragonal and orthorhombic solubilities are equal, is a function of the pH, salt (precipitant) type and concentration, and most likely of the buffer concentration as well. This phase transition can be carried out with protein solution alone, prior to addition of precipitant solution. Warming a lysozyme solution above the phase transition point, then cooling it back below this point, has been shown to affect the subsequent nucleation rate, as determined by the numbers and size of crystals formed, but not the growth rate for the tetragonal crystal form . We have now measured the kinetics of this process and investigated its reversibility. The transition effects are progressive with temperature, having a half time of about 1 hour at 37C at pH 4.8. After holding a lysozyme solution at 37C (prior to addition of precipitant) for 16 hours, then cooling it back to 4C no return to the pre-warmed nucleation kinetics are observed after at least 4 weeks. Orthorhombic lysozyme crystals apparently do not undergo the flow-induced growth cessation of tetragonal lysozyme crystals. Putting the protein in the orthorhombic form does not affect the averaged face growth kinetics, only nucleation, for tetragonal crystals. This differential behaviour may be exploited to elucidate how and where flow affects the lysozyme crystal growth process. The presentation will focus on the results of these and ongoing studies in this area.
Burke, Michael↗