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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Design considerations for optical heterodyne receivers: A review

The current state of knowledge concerning optical heterodyne receivers is reviewed. Following a discussion of noise processes in the heterodyne receiver and the manner in which sensitivity is increased through time integration of the detected signal, an expression for the mean square signal current is derived by mixing a coherent local oscillator with a partially coherent, quasimonochromatic source. Then the manner in which the IF signal calculation can be transferred to any convenient plane in the optical front end of the receiver is demonstrated. Using these techniques, a relatively simple equation is obtained for the coherently detected signal from an extended incoherent source and applied to the heterodyne detection of an extended thermal source and to the backscatter lidar problem where the antenna patterns of both the transmitter beam and heterodyne receiver must be taken into account. Finally, the detection of a coherent source is considered and, in particular, a distant point source such as a star or laser transmitter in a long range heterodyne communications system is discussed.

Degnan, J. J.↗
NASA NTRS1986

Development of an emulation-simulation thermal control model for space station application

The orbiting space station being developed by NASA will have many thermal sources and sinks as well as requirements for the transport of thermal energy through large distances. The station is also expected to evolve over twenty or more years from an initial design. As the station evolves, thermal management will become more difficult. Thus, analysis techniques to evaluate the effects of changing various thermal loads and the methods utilized to control temperature distributions in the station are essential. Analysis techniques, including a user-friendly computer program, were developed which should prove useful to thermal designers and system analysts working on the space station. The program uses a data base and user input to compute costs, sizes, and power requirements for individual components and complete systems. User input consists of selecting mission parameters, selecting thermal acquisition configurations, transport systems and distances, and thermal rejection configurations. The capabilities of the program may be expanded by including additional thermal models as subroutines.

Hartley, James G.↗
NASA NTRS1989

The spatial scales and rise times of impulsive solar burst sources

During the rise time of an impulsive solar burst of hard X-rays and microwaves, energy release overwhelms losses so that the characteristics of the flare energy release process are best displayed. A sample of 30 bursts was analyzed, and the rise times of the bursts were compared with their source length scales. The result, as in earlier work employing the 'thermal conduction-front' model, is that the burst length scales were linerly proportional to their rise times, and ranged from 5.4 x 10 to the 6th to 3.6 x 10 to the 9th cm. This proportionality places a new and restrictive condition upon the possible energy release processes. The new condition is especially powerful because the proportionality was formerly believed to depend on the thermal source model alone, but now is known to follow from every model in current use.

Batchelor, David↗
NASA NTRS2005

The Impact of the Sun on Passive Remote Sensing at L-band

The sun is a strong source of radiation at L-band behaving roughly like a thermal source with a temperature ranging between 10(exp 5) - 10(exp 7) K, depending on solar activity. This is an important consideration at 1.4 GHz (the window set aside for passive use only) where future satellite sensors will operate to monitor soil moisture and sea surface salinity (e.g. SMOS, Aquarius, and Hydros). Straight forward calculations show that such a source of radiation can be a significant issue for these remote sensing applications, especially in the case of remote sensing of sea surface salinity. Radiation from the sun impacts passive remote sensing systems in several ways. First, is the solar radiation that comes directly from the sun (line-of-sight from sun to spacecraft that enters the radiometer through antenna side lobes). This is a particular problem for sensors in sunsynchronous orbits near the terminator (e.g. orbits with equatorial crossing times near 6am/6pm) because the spacecraft is in the sun most of the time. Second, is solar radiation that is reflected (specularly) from the mean surface to the radiometer. This contribution can be nearly as large as the direct ray, especially when the reflection is from the ocean surface which has a high reflection coefficient. Finally, there is "incoherent" signal reflected from the surface structure (roughness) to the radiometer antenna. Examples illustrating the significance of these terms is presented for the case of a pushbroom radiometer such as Aquarius and a conically scanning radiometer such as proposed for Hydros. Calculations are made using a set of theoretical patterns for these beams together with data on solar radiation obtained from by a worldwide network of observing stations known as Radio Solar Telescope Network (RSTN). Near solar minimum, solar contamination is not a problem unless the sun enters near the main beam. But near solar maximum, account must be made for radiation from the sun even when the signal enters in sidelobes far from the main beam.

LeVine, David M.↗
NASA NTRS1972

Extragalactic X-ray sources.

The extended X-ray sources associated with the Virgo, Perseus, and Coma clusters of galaxies can best be explained as a result of the Compton scattering of relativistic electrons (generated in the radio sources which are present in each of these clusters) on the microwave background radiation. The same physical process involving microwave infrared or optical photons generated in the nuclei of active galaxies may account for the more compact X-ray sources. Thermal bremsstrahlung of hot gas in clusters of galaxies is a less likely source of X-rays.

Brecher, K.↗
DOE OSTI2025

Comparative Analysis of HEATNETS for Geothermal Network Performance

Thermal energy networks (TENs), also known as 5th generation district energy systems, or more specifically geothermal networks when exchanging heat with geothermal boreholes, are an important technology for decarbonization. In these networks an ambient loop connects buildings and thermal sources, such as a borehole field, to exchange energy and maintain a desired loop temperature. Water-source heat pumps are used at the buildings to connect to the ambient or thermal loop to meet to the building heating and cooling loads and maintain comfort. A semi-transient, reduced-order technical model and techno-economic model, called HEATNETS, has been developed at NREL that captures the flow of energy around a TEN. In this work, a comparison of the HEATNETS technical model and a well-known coding platform used for modeling geothermal networks, TRNSYS, has been completed for a proposed geothermal network as a verification and validation process. Hourly data provided from the TRNSYS simulation included building loads, pumping power, heat pump power, temperature entering and leaving the borehole field, and mass flow rates. The hourly borehole temperatures were used to create a linear regression model utilized in HEATNETS to estimate the borehole field heat exchange. The building loads and mass flow rates were direct inputs to HEATNETS while the pumping power, heat pump power, borehole temperatures, and coefficients of performance were all simulated and calculated by HEATNETS, allowing for direct comparison of the thermal energy transfer HEATNETS considers the full process from design inputs to economic outputs and can provide modeling options for high-level initial system design and operational optimization. This study focuses on a validation of HEATNETS using results from TRNSYS. HEATNETS is not intended to replace other modeling tools, but this work demonstrates, via a comparison with an industry standard code, that HEATNETS can be a unique, high-level and rapid modeling tool for estimating the performance of a full geothermal network system.

15 GEOTHERMAL ENERGY↗
DOE OSTI2025

Comparative Analysis of HEATNETS for Geothermal Network Performance: Preprint

Thermal energy networks (TENs), also known as 5th generation district energy systems, or more specifically geothermal networks when exchanging heat with geothermal boreholes, are an important technology for decarbonization. In these networks an ambient loop connects buildings and thermal sources, such as a borehole field, to exchange energy and maintain a desired loop temperature. Water-source heat pumps are used at the buildings to connect to the ambient or thermal loop to meet to the building heating and cooling loads and maintain comfort. A semi-transient, reduced-order technical model and techno-economic model, called HEATNETS, has been developed at NREL that captures the flow of energy around a TEN. In this work, a comparison of the HEATNETS technical model and a well-known coding platform used for modeling geothermal networks, TRNSYS, has been completed for a proposed geothermal network as a verification process. Hourly data provided from the TRNSYS simulation included building loads, pumping power, heat pump power, temperature entering and leaving the borehole field, and mass flow rates. The hourly borehole temperatures were used to create a linear regression model utilized in HEATNETS to estimate the borehole field heat exchange. The building loads and mass flow rates were direct inputs to HEATNETS while the pumping power, heat pump power, borehole temperatures, and coefficients of performance were all simulated and calculated by HEATNETS, allowing for direct comparison of the thermal energy transfer, rather than also comparing control systems responses. HEATNETS considers the full process from design inputs to economic outputs and can provide modeling options for high-level initial system design and operational optimization. This study shows that HEATNETS, while not intended to replace other modeling tools, can be a unique modeling tool for the performance of a full geothermal network system.

15 GEOTHERMAL ENERGY↗
DOE OSTI2020

Adapting the Electron Beam from SEM as a Quantitative Heating Source for Nanoscale Thermal Metrology

The electron beam (e-beam) in the scanning electron microscopy (SEM) provides an appealing mobile heating source for thermal metrology with spatial resolution of ~1 nm, but the lack of systematic quantification of the e-beam heating power limits such application development. Here, we systemically study e-beam heating in LPCVD silicon nitride (SiN x ) thin-films with thickness ranging from 200 to 500 nm from both experiments and complementary Monte Carlo simulations using the CASINO software package. There is good agreement about the thickness-dependent e-beam energy absorption of thin-film between modeling predictions and experiments. Using the absorption results, we then demonstrate adapting the e-beam as a quantitative heating source by measuring the thickness-dependent thermal conductivity of SiN x thin-films, with the results validated to within 7% by a separate Joule heating experiment. The results described here will open a new avenue for using SEM e-beams as a mobile heating source for advanced nanoscale thermal metrology development.

42 ENGINEERING↗
NASA NTRS1981

A comparison of the height distributions of solar flare hard X-rays in thick target and thermal models

Using recent observations of solar hard X-ray bursts having a spatial resolution of a few arcsec, a computation is made of the theoretically predicted spatial variation of hard X-ray flux versus height in both thick target nonthermal and thermal models of solar hard X-ray bursts. The work on the thick target model revises previous results in this area by adopting a more realistic model for the flaring atmospheric structure and also by taking into account energy loss and scattering processes in the evolution of the nonthermal electron beam which have previously been neglected. It is noted that in the so-called 'thermal' model currently in vogue there is a substantial nonthermal bremsstrahlung component at all photon energies; it is further demonstrated that this nonthermal component results in a hard X-ray flux versus height distribution whose maximum brightness per unit length is, similarly to the thick target model, located in the chromosphere and not in the thermal source itself. The characteristics of the hard X-ray height distributions in both thick target and thermal models are summarized and compared.

Emslie, A. G.↗
NASA NTRS1983

X-ray spectra of Orion OB supergiants

The spectra are at a higher energy resolution than earlier X-ray observations of OB supergiants, and this allows stronger constraints to be placed on the location of the emission source in the outer atmosphere. The spectra of all three stars are found to be consistent with thermal sources which are only slightly attenuated by stellar wind opacity and have temperatures of approximately 10 to the (6.5 + or - 0.2) power K. A number of explanations of the soft X-ray flux distributions of early-type stars are tested. A model with the X rays coming only from a corona in a slab at the base of the wind does not seem a possibility unless the ionization or density structure of the overlying material is significantly different from that usually assumed for a cool wind. A model where the X rays are produced by radiatively driven shocks, some of which must be strong, can explain the X-ray luminosity and satisfy upper limits on the absorption by oxygen derived from the data. A high-energy (greater than 1 keV) contribution from a base coronal zone is considered possible. The spectrum of Zeta Ori shows emission near 2 keV, wich can be interpreted as line emission of Si XIII and S XV from a very hot source component with T = 1.5 x 10 to the 7th K.

Cassinelli, J. P.↗
NASA NTRS1998

Tape-Drop Transient Model for In-Situ Automated Tape Placement of Thermoplastic Composites

Composite parts of nonuniform thickness can be fabricated by in-situ automated tape placement (ATP) if the tape can be started and stopped at interior points of the part instead of always at its edges. This technique is termed start/stop-on-the-part, or, alternatively, tape-add/tape-drop. The resulting thermal transients need to be managed in order to achieve net shape and maintain uniform interlaminar weld strength and crystallinity. Starting-on-the-part has been treated previously. This paper continues the study with a thermal analysis of stopping-on-the-part. The thermal source is switched off when the trailing end of the tape enters the nip region of the laydown/consolidation head. The thermal transient is determined by a Fourier-Laplace transform solution of the two-dimensional, time-dependent thermal transport equation. This solution requires that the Peclet number Pe (the dimensionless ratio of inertial to diffusive heat transport) be independent of time and much greater than 1. Plotted isotherms show that the trailing tape-end cools more rapidly than the downstream portions of tape. This cooling can weaken the bond near the tape end; however the length of the affected region is found to be less than 2 mm. To achieve net shape, the consolidation head must continue to move after cut-off until the temperature on the weld interface decreases to the glass transition temperature. The time and elapsed distance for this condition to occur are computed for the Langley ATP robot applying PEEK/carbon fiber composite tape and for two upgrades in robot performance. The elapsed distance after cut-off ranges from about 1 mm for the present robot to about 1 cm for the second upgrade.

Costen, Robert C.↗
NASA NTRS1988

Analytic limits on the forms of spectra possible from optically thin collisional bremsstrahlung source models

The constraints on hard X-ray bremsstrahlung spectral forms required in order for them to correspond to physically acceptable (nonnegative) electron distributions in thin-target, thick-target, and thermal source models are discussed. The extent to which various spectra can be attributed to the different models is examined, showing that many possible spectra cannot be described by all, or in some cases, any of the models. It is shown that for any bremsstrahlung cross section, the thick-target and thermal models require that successively higher derivatives of the thin-target constraint have the appropriate sign. It is found that thermal models are the most restrictive, and that thin-target models are the least restrictive. Explicit analytic constraint expressions are derived for all three cases for the Kramers cross section and examples of acceptable and unacceptable spectra are given. Application of these criteria to the testing and exclusion of models is discussed.

Brown, John C.↗
DOE OSTI2016

Directional and monochromatic thermal emitter from epsilon-near-zero conditions in semiconductor hyperbolic metamaterials

The development of novel thermal sources that control the emission spectrum and the angular emission pattern is of fundamental importance. In this paper, we investigate the thermal emission properties of semiconductor hyperbolic metamaterials (SHMs). Our structure does not require the use of any periodic corrugation to provide monochromatic and directional emission properties. We show that these properties arise because of epsilon-near-zero conditions in SHMs. The thermal emission is dominated by the epsilon-near-zero effect in the doped quantum wells composing the SHM. In conclusion, different properties are observed for s and p polarizations, following the characteristics of the strong anisotropy of hyperbolic metamaterials.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Development of Streamlined Nuclear Safety Analysis Tool for Spent Nuclear Fuel Applications

To understand the changing nuclear and mechanical characteristics of spent nuclear fuel (SNF) or used nuclear fuel (UNF) and the different storage, transportation, and disposal systems at various stages within the waste management system, different types of analyses are required. These analyses require the use of assorted tools and numerous types of data. Using the appropriate modeling and simulation (M&S) parameters and selecting from the diversity of analytic tools to conduct SNF analyses can be a tedious, error-prone, and time-consuming undertaking for analysts and reviewers alike. A new, integrated data and analysis system was designed to simplify and automate performance of accurate, efficient evaluations for characterizing the input to the overall U.S. nuclear waste management system—the UNF-Storage, Transportation & Disposal Analysis Resource and Data System (UNF-ST&DARDS). A relational database has been assembled to provide a standard means by which UNF-ST&DARDS can succinctly store and retrieve M&S parameters for specific SNF analysis. A library of various analysis model templates is used to communicate M&S parameters for the most appropriate M&S application. A process manager facilitates performance of actual as-loaded, assembly-specific, and cask-specific evaluations. Interactive visualization capabilities facilitate data analysis and results interpretation. To date, UNF-ST&DARDS has completed (1) explicit depletion and decay analysis of every fuel assembly (~245 000) discharged from commercial U.S. reactors through June 2013, with 13 cooling time steps (results include isotopic compositions for 142 isotopes, and radiation and thermal source terms); (2) SNF radiation dose rate evaluations at 1 m for all the fuel assemblies discharged through June 2013; and (3) criticality, shielding, thermal, and containment analyses of hundreds of loaded casks. In conclusion, UNF-ST&DARDS also provides various automated report generation capabilities with dynamic figure and table update capabilities based on changes to the Unified Database.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS1976

Infrared emission from A0620-00

Infrared observations of the transient X-ray source A0620-00 were made on Aug. 26 and 29, 1975. When combined with optical data, these observations are consistent with emission from a thermal source which is optically thick at visual wavelengths if the interstellar extinction is about 2.2 magnitudes. Implications of these data for models of the source are discussed.

Kleinmann, S. G.↗
DOE OSTI2026

Dual Purpose – Heating & Cooling – Thermal Battery for Flexible and Energy-Efficient Heat Pump Systems

The integration of heat pumps with thermal energy storage (HP-TES) systems is gaining attention as a viable solution for managing peak building demand driven by immense cooling and heating loads. With growing reliance on renewable energy sources, thermal energy storage offers an excellent opportunity to mitigate mismatches in thermal load between energy supply and demand. The use of phase-change material (PCM) TES is especially promising, as PCMs offer significant latent energy storage capacity with smaller temperature glides in smaller volumes compared to other TES technologies. However, challenges arise because current HP-TES architectures can load-shift only cooling or heating, not both, requiring two systems and thus doubling cost, weight, and footprint. Furthermore, current research efforts lack specific tools and techniques to advance integrated systems from concept design to end-user application, focusing on only discharge performance. To address these challenges, this research proposes a dual-mode (heating and cooling) integrated HP-TES system that uses room-temperature PCM-TES as a high-temperature heat source in heating mode and a low-temperature heat sink in cooling mode, thereby reducing temperature lifts and compressor power. Design criteria for PCM-TES heat exchangers were developed, balancing thermal-hydraulic performance with practical constraints such as available building space and weight requirements along with PCM selection considerations such as shipping conditions, moisture exposure, and number of available cycles. A detailed transient model for HP-TES systems was developed to enable rapid annual performance assessments in any US climate zone.

42 ENGINEERING↗
NASA NTRS1983

He D3 as a diagnostic for the hard and soft X-rays from solar flares

The time comparison of He D3 and X-ray emission has been studied in a number of medium-sized flares. In most cases there is a good agreement between the time histories of the He D3 emission and the high-temperature (about 2 keV) thermal source. The most intense He D3 emission comes from two small regions on either side of the neutral line, which are identified with the footpoints of magnetic structures in which a hot (2.3 x 10 to the 7th K) thermal plasma is formed. The impulsive X-ray event is marked by the transient brightening of a number of (usually weaker) He D3 sources. The two types of sources are well displaced from each other, which is an indication that they are produced in two different volumes. In some cases a long-lived third He D3 source is seen.

Feldman, U.↗
DOE OSTI2023

The Internal Compound Parabolic Concentrator (ICPC): a Novel Low Cost Solar Thermal Collection System for Desalination Processes

The research team at UC Merced designed, prototyped, and tested (1) a novel low cost non-tracking solar thermal collector/concentrator called the Integrated Compound Parabolic Concentrator (ICPC) and (2) a low-cost phase-change thermal energy storage system. Together these technologies can significantly reduce the levelized cost of heat from solar thermal sources while also incorporating features of dispatchability and portability. The ICPC allows elevated temperature and efficiency in a low cost, non-tracking collector. The collector has demonstrated 60% ±4% solar to thermal modules efficiency at fluid outlet temperature of 120°C. The raw material cost of the collector system is reduced by utilizing low cost aluminum minichannels. The collector design is also amenable to economic mass production. A 200 tube, 10 kW prototype array was constructed and tested, yielding over 6 kWh/day on average at outlet fluid temperature exceeding 120°C.

14 SOLAR ENERGY↗