Application of the line-source technique for vacuum thermal conductivity measurements.
Line source technique for ablative heat shield materials thermal conductivity measurements, comparing vacuum and atmospheric test results
Comparin, R. A.↗
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Application of the line-source technique for vacuum thermal conductivity measurements
Line source technique for ablative heat shield materials thermal conductivity measurements, comparing vacuum and atmospheric test results
Comparin, R. A.↗
Theory and application of scanning electron acoustic microscopy
A three-dimensional theoretical model based on the application of the thermal conduction and Navier equations to a chopped electron beam incident on a disk specimen is used to obtain the particle displacement field in the specimen. The results lead to a consideration of the signal generation, spatial resolution, and contrast mechanisms in scanning electron acoustic microscopy (SEAM). The model suggests that the time-variant heat source produced by the beam chopping generates driving source, thermal wave, and acoustic wave displacements simultaneously in the specimen. Evidence of the correctness of the prediction is obtained from the mathematically similar problem of pulsed laser light injection into a tank of water. High speed Schlieren photographs taken following laser injection show the simultaneous evolution of thermal and acoustic waveforms. Examples of contrast reversal, stress-induced contrast, and acoustic zone contrast and resolution with SEAM are presented and explained in terms of the model features.
Cantrell, John H.↗
Pulsed Thermal Tomography Nondestructive Examination of Additively Manufactured Reactor Materials and Components. Third Annual Progress Report
Additive manufacturing (AM) of high-strength corrosion resistance alloys for nuclear energy applications, such as stainless steel and Inconel, is currently based on laser powder bed fusion (LPBF) process. Some of the challenges with using LPBF method for nuclear manufacturing include the possibility of introducing pores into metallic structures. Probability of crack initiation at the pore depends on size, shape, and orientation of the defect. Pulsed Infrared Thermography Imaging (PIT) provides a capability for non-destructive evaluation (NDE) of sub-surface defects in arbitrary size structures. The PIT method is based on recording material surface temperature transients with infrared (IR) camera following thermal pulse delivered on material surface with flash light. The PIT method has advantages for NDE of actual AM structures because the method involves one-sided non-contact measurements and fast processing of large sample areas captured in one image. Following initial qualification of an AM component for deployment in a nuclear reactor, a PIT system can also be used for in-service nondestructive evaluation (NDE) applications. In this report, we describe recent progress in enhancing PIT capabilities in detecting microscopic subsurface defects in metals, and classifying shapes and orientation of pores in thermal images. For detection of microscopic defects in PIT imaging data, we have developed Spatial Temporal Denoised Thermal Source Separation (STDTSS) unsupervised machine learning (ML) image processing algorithm. We show that flat bottom hole (FBH) defects as small as 200µm in SS316 and IN718 specimens, can be detected with STDTSS algorithm. To the best of our knowledge, these are the smallest detected defects which are reported in literature. For classification of defects shapes, we have previously developed thermal tomography (TT) algorithm to obtain depth reconstructions of material defects from data cube of sequentially recorded surface temperatures. However, interpretation of TT images is non-trivial because of blurring with increasing depth. To address this challenge, we have developed a deep learning convolutional neural network (CNN) to classify size and orientation subsurface defects in simulated TT images.
22 GENERAL STUDIES OF NUCLEAR REACTORS↗
X-Ray Spectra from General Relativistic Radiation Magnetohydrodynamic Simulations of Thin Disks
We compare X-ray emission from several general relativistic, multifrequency, radiation magnetohydrodynamic simulations of thin black hole accretion disks with different accretion rates and spins. The simulations were performed using the M1 closure scheme, resolved with 12 frequency (energy) bins logarithmically spaced from 5 × 10 −3 to 5 × 10 3 keV. We apply a general relativistic Monte Carlo transport code to postprocess the simulation data with greater fidelity in frequency resolution and Compton scattering treatment. Despite the relatively few energy bins and Kompaneets approximation to Compton scattering utilized in the M1 method, we find generally good agreement between the methods. Both produce prominent thermal profiles with peaks around 2–2.5 keV, where agreement is particularly strong and representative of the soft state. Both also find weaker (lower-luminosity) thermally sourced emission extending out to 100 keV due to the hotter innermost regions of the disks. Inverse Compton scattering becomes increasingly effective at hardening spectral outputs with increasing black hole spin, and becomes the dominant mechanism for photons that escape with energies between 10 to several hundred keV. At very high rates of spin, the radiation flux in this upscattered component becomes comparable to the thermal flux, a phenomenon typically associated with intermediate states. Beyond 10 4 keV, we observe faint, free–free emission from hot, optically thin coronal regions developing near the horizon, common to both spinning and nonspinning black holes.
79 ASTRONOMY AND ASTROPHYSICS↗
Absorption/Desorption based high efficiency Supercritical Carbon Dioxide Power Cycles - Final Scientific/Technical Report
The team of Southwest Research Institute® (SwRI®) and Thar Energy LLC (Thar) are advancing the state of the art in fossil-fired closed Brayton supercritical carbon dioxide (sCO 2 ) power cycles. This current effort is focused on evaluating the integration of a fossil-based thermal system with closed Brayton sCO 2 power blocks to understand the impact of thermal integration on plant performance and identification of current technology gaps. This effort is extending the current understanding of how fossil-based thermal systems may best be integrated with recuperated closed Brayton cycles based on the overall impact on the integrated plant efficiency, cost, and operating characteristics. System Engineering Design and Thermodynamic Analysis is being utilized to (1) identify technical challenges impacting the integration of fossil-based thermal sources with highly recuperated closed Brayton sCO 2 power cycles, (2) evaluate the impact of boiler design and sCO 2 cycle configuration on integrated plant performance, cost, and operability, and (3) evaluate technology readiness of the integrated system and identify specific technologies requiring development of advanced fossil-based sCO 2 cycles. Engineering evaluation is being applied to coal- and natural gas-fired thermal systems for sCO 2 power cycles to evaluate current boiler technologies and challenges associated with adapting those to a sCO 2 based configuration. This includes technical evaluation of the sCO 2 heat exchanger design and anticipated performance impacts on the thermal system. In addition to the general evaluation of indirect fossil fires closed Brayton sCO 2 cycles, this effort is also evaluating a novel indirect sCO 2 power cycle that utilizes an absorption/desorption circuit to minimize compression work by 40% to 65%. This translates to a thermodynamic cycle efficiency improvement of 3.2 points for a simple recuperated cycle using a binary CO 2 + Acetone working fluid.
20 FOSSIL-FUELED POWER PLANTS↗
DENSITY OF WARM IONIZED GAS NEAR THE GALACTIC CENTER: LOW RADIO FREQUENCY OBSERVATIONS
We have observed the Galactic center (GC) region at 0.154 and 0.255 GHz with the Giant Metrewave Radio Telescope. A total of 62 compact likely extragalactic (EG) sources are detected. Their scattering sizes decrease linearly with increasing angular distance from the GC up to about 1 Degree-Sign . The apparent scattering sizes of the sources are more than an order of magnitude less than predicted earlier by the NE2001 model of Galactic electron distribution within 359. Degree-Sign 5 < l < 0. Degree-Sign 5 and -0. Degree-Sign 5 < b < 0. Degree-Sign 5 (Hyperstrong Scattering Region) of the Galaxy. High free-free optical depths ({tau}) are observed toward most of the extended non-thermal sources within 0. Degree-Sign 6 from the GC. Significant variation of {tau} indicates that the absorbing medium is patchy at an angular scale of {approx}10' and n{sub e} is {approx}10 cm{sup -3}, which matches the NE2001 model. This model predicts the EG sources to be resolved out from 1.4 GHz interferometric surveys. However, out of 10 EG sources expected in the region, 8 likely EG are present in the 1.4 GHz catalog. Ionized interfaces of dense molecular clouds to the ambient medium are most likely responsible for strong scattering and low radio frequency absorption. However, dense GC clouds traced by CS J = 1-0 emission are found to have a narrow distribution of {approx}0. Degree-Sign 2 across the Galactic plane. Angular distribution of most EG sources seen through the so-called Hyperstrong Scattering Region are random in b, and typically {approx}7 out of 10 sources will not be seen through the dense molecular clouds, which explains why most of them are not scatter broadened at 1.4 GHz.
79 ASTRONOMY AND ASTROPHYSICS↗
Microsecond switchable thermal antenna
We propose a thermal antenna that can be actively switched on and off at the microsecond scale by means of a phase transition of a metal-insulator material, the vanadium dioxide (VO{sub 2}). This thermal source is made of a periodically patterned tunable VO{sub 2} nanolayer, which support a surface phonon-polariton in the infrared range in their crystalline phase. Using electrodes properly registered with respect to the pattern, the VO{sub 2} phase transition can be locally triggered by ohmic heating so that the surface phonon-polariton can be diffracted by the induced grating, producing a highly directional thermal emission. Conversely, when heating less, the VO{sub 2} layers cool down below the transition temperature, the surface phonon-polariton cannot be diffracted anymore so that thermal emission is inhibited. This switchable antenna could find broad applications in the domain of active thermal coatings or in those of infrared spectroscopy and sensing.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA Tech Briefs, November 2011
The topics include: 1) Flight Test Results from the Rake Airflow Gage Experiment on the F-15B; 2) Telemetry and Science Data Software System; 3) CropEx Web-Based Agricultural Monitoring and Decision Support; 4) High-Performance Data Analysis Tools for Sun-Earth Connection Missions; 5) Experiment in Onboard Synthetic Aperture Radar Data Processing; 6) Microfabrication of a High-Throughput Nanochannel Delivery/Filtration System; 7) Improved Design and Fabrication of Hydrated-Salt Pills; 8) Monolithic Flexure Pre-Stressed Ultrasonic Horns; 9) Cryogenic Quenching Process for Electronic Part Screening; 10) Broadband Via-Less Microwave Crossover Using Microstrip-CPW Transitions; 11) Wheel-Based Ice Sensors for Road Vehicles; 12) G-DYN Multibody Dynamics Engine; 13) Multibody Simulation Software Testbed for Small-Body Exploration and Sampling; 14) Propulsive Reaction Control System Model; 15) Licklider Transmission Protocol Implementation; 16) Core Recursive Hierarchical Image Segmentation; 17) Two-Stage Centrifugal Fan; 18) Combined Structural and Trajectory Control of Variable-Geometry Planetary Entry Systems; 19) Pressure Regulator With Internal Ejector Circulation Pump, Flow and Pressure Measurement Porting, and Fuel Cell System Integration Options; 20) Temperature-Sensitive Coating Sensor Based on Hematite; 21) Standardization of a Volumetric Displacement Measurement for Two-Body Abrasion Scratch Test Data Analysis; 22) Detection of Carbon Monoxide Using Polymer-Carbon Composite Films; 23) Substituted Quaternary Ammonium Salts Improve Low-Temperature Performance of Double-Layer Capacitors; 24) Sustainably Sourced, Thermally Resistant, Radiation Hard Biopolymer; 25) Integrated Lens Antennas for Multi-Pixel Receivers; 26) 180-GHz Interferometric Imager; 27) Maturation of Structural Health Management Systems for Solid Rocket Motors; 28) Validating Phasing and Geometry of Large Focal Plane Arrays; 29) Transverse Pupil Shifts for Adaptive Optics Non-Common Path Calibration; 30) Qualification of Fiber Optic Cables for Martian Extreme Temperature Environments; 31) Solid-State Spectral Light Source System; 32) Multiple-Event, Single-Photon Counting Imaging Sensor; 33) Surface Modeling to Support Small-Body Spacecraft Exploration and Proximity Operations; and 34) Achieving Exact and Constant Turnaround Ratio in a DDS-Based Coherent Transponder.
Source record↗
On the operational characteristics and economic value of pumped thermal energy storage
Pumped thermal energy storage (PTES) systems use an electrically-driven heat pump to store electricity in the form of thermal energy, and subsequently dispatch the stored thermal energy to generate electricity using a thermodynamic heat engine. Optimal day-ahead operational scheduling and annual value of a PTES system based on Joule-Brayton thermodynamic cycles and two-tank molten salt hot thermal storage is evaluated in this work. Production cost models, which simultaneously optimize commitment and dispatch schedules for an entire set of generators to minimize the cost of satisfying electricity demand, are employed to determine system-optimal operation and day-ahead energy value of the PTES system within each of six hypothetical near-future grid scenarios intended to approximately represent the U.S. Western Interconnection or the Texas Interconnection. Sensitivity to grid scenario (including the contribution of variable renewable energy sources), thermal storage capacity, relative heat pump and heat engine capacities, and startup/shutdown cycling costs are evaluated. PTES energy value and heat engine annual capacity factor increase strongly as the contribution of variable renewable resources increases, heat pump capacity increases relative to heat engine capacity, or PTES cycling costs decrease. Grid scenarios in which the contribution of variable renewable energy is dominated by solar photovoltaics (PV) vs. wind produce inherently different PTES operational patterns. Annual PTES energy value within PV-dominated scenarios increased with storage capacity only up to approximately seven hours of full-load discharge capacity, whereas that within wind-dominated scenarios exhibited a continual increase with storage duration up to at least 16 hours.
24 POWER TRANSMISSION AND DISTRIBUTION↗
Intense Pulse Light Annealing of Perovskite Photovoltaics Using Gradient Flashes
Perovskite solar cells (PSCs) have been fabricated through high-speed and low-cost depositions but often require long annealing. Intense pulse light (IPL) can anneal thin films in seconds after deposition by inducing very high temperatures lasting for milliseconds, and multiple flashes can be used to tune the temperature profile. In this study, a gradient flash annealing (GFA) approach is introduced and compared to uniform flash annealing (UFA) by investigating the crystallinity, morphology, and phase evolution of the CH 3 NH 3 PbI 3 perovskite films and their impact on PSC performance. Unlike UFA, low-intensity pulsed irradiation during the pre-annealing stage of GFA played a significant role on enhancing the PSC performance by forming pure-phase CH 3 NH 3 PbI 3 perovskite thin films with superior morphology and high crystallinity. To understand the kinetics, a transient thermal simulation using ANSYS was developed and confirmed with an experimental setup. The results combined with microscopy and spectrophotometry were used to visualize how duration, delay time, photon flux, and flash count parameters participated in crystallization, phase, and morphology evolution. The IPL annealing induced rapid surface temperature increase, reaching as high as 800 °C, while produced well-developed and bound perovskite grains without any surface defects in an uncontrolled ambient environment with high humidity (>60%). The study resulted in PSCs with maximum efficiency and fill factor of 9.27 and 69.92% for the UFA and 11.75 and 68% when annealed through the GFA approach, respectively. Lastly, this work utilized IPL as the sole thermal source for post-deposition annealing to rapidly fabricate efficient PSCs in only 10 s, which opens the pathway for high-speed, low-cost, and large-scale automated fabrication of perovskite photovoltaics and semiconductors.
14 SOLAR ENERGY↗
Comparison of Thermal Coefficients for Two Microwave Detectors
Laboratory measurements were performed to compare the thermal coefficients of two microwave detectors that might be used for direct detection in L-band radiometers. In particular it was desired to compare the performance of a new-technology flash ADC (analog-to-digital converter) against that of an older-technology diode detector in series with a VFC (voltage-to-frequency converter). The outputs of two state-of-the-art detectors were recorded as a constant 1.414-GHz signal was input and the physical temperatures of the detectors were varied over a range of 10 C. As a further experiment, each detector was tested with a noise diode source and with a sine wave synthesizer source. Thermal coefficients were computed in terms of W/C and in terms of ppt/C at nominal operating temperatures reasonable for the individual devices. Finally, thermal coefficients were calculated in K/C to indicate the change in brightness temperature seen by a theoretical sea surface salinity radiometer employing each detector. The K/C for the flash ADC was determined to be about 2.8 times that of the diode/VFC. Different reactions of the ADC to a noise input and a sine wave input indicated that ADC tests for radiometric purposes, such as this one, should be performed using a noise input.
Mackenzie, Anne I.↗
Review of Inorganic Salt Hydrates with Phase Change Temperature in Range of 5°C to 60°C and Material Cost Comparison with Common Waxes
Phase change materials (PCMs) with desirable phase change temperatures can be used to provide a constant temperature thermal source or sink for diverse applications. As such, incorporating PCMs into building materials, equipment, or appliances can shift and/or reduce the energy load. The motivation of this work is to identify low-cost inorganic salt hydrate PCMs that can complement current building systems and designs, and compare them with common paraffins.In this work, we analyzed inorganic salt hydrates with phase change temperatures in the range of 5-60°C, to target both space heating and cooling applications. The properties of the salt hydrates were compared with paraffins over the same temperature range. The results showed that PCMs with a melting temperature above 20°C, salt hydrates have advantages over paraffins including higher thermal energy density (45-120 kWh/m3 for salt hydrates; 45-60 kWh/m3 for paraffins) and generally lower material energy cost (1-20 $/kWh for salt hydrates; 20-30 $/kWh for comparable paraffins). For PCMs with a melting temperature less than 20°C, the material cost is higher for both salt hydrates and paraffins (30-110 $/kWh for both classes of materials) and salt hydrates retain their advantage of greater thermal energy density (50-120 kWh/m3 for salt hydrates; 45-60 kWh/m3 for paraffins). In all cases, factors including thermal cyclability, stability, congruency, corrosion, and supercooling must be considered when comparing paraffins and salt hydrates for a particular application. Finally, we give an overview of enhancement techniques for salt hydrate PCMs and find that limited efforts have been pursued to tune salt hydrate phase change temperatures, with a wider range of studies investigating stabilization and minimization of supercooling. This analysis shows the potential of developing salt hydrate PCMs for low-cost heating and cooling thermal energy storage systems for a range of applications.
Hirschey, Jason↗
Thermal dissociation of alkyl nitrites and recombination of alkyl radicals
Not Available
Randazzo, John B.↗
A Topology Optimization Framework to Facilitate Adoption of Advanced District Thermal Energy Systems
Advanced district thermal energy systems, which circulate water at temperatures near ambient conditions, and facilitate the utilization of waste heat and renewable thermal sources, can lower the carbon-intensity of urban districts, advancing the U.N. Sustainable Development Goals. Optimization of the network topology — the selection of the best subset of buildings and the best network to connect them, to minimize life cycle cost — can increase adoption of these system in appropriate applications. The potential "solution space" of the topology optimization problem grows factorially with the number of buildings in the district, motivating the consideration of a design heuristic. In this study, a heuristic for the network selection was evaluated with an exhaustive search, for a prototypical four-building district. For the prototypical district considered, the heuristic was effective in selecting an optimal network topology. Additionally, it was found that, in this case, the selection of the subset of buildings was more influential on the life cycle cost than the selection of the network topology. This work is part of a larger effort to develop a topology optimization framework for district thermal energy systems, which is anticipated to address barriers to adoption of ambient-temperature systems.
28 EE - Advanced Manufacturing Office (EE-5A)↗
Embedding Neural Thermal Scattering (NeTS) Modules in SERPENT for Higher Fidelity Advanced Reactor Analysis
When a neutron born in fission thermalizes to the order of $k$ $B$ $T$, it’s de-Broglie wavelength and energy approach the order of inter-atomic spacing and elementary lattice oscillations, respectively. $S$($a,β,t$) or the scattering law, uuantify these temperature-dependent crystallographic contributions to total cross section (or reaction rate). In a Monte Carlo analysis, cumulative distribution functions (CDFs) of $S$($a,β,t$) are loaded to memory from “A Compact ENDF” (ACE) files for stochastically selecting thermal scattered neutron trajectories. In this work, novel neural thermal scattering (NeTS) modules for $S$($a,β,t$) CDFs are designed, trained, serialized and embedded within SERPENT using Python’s limited C-API for on-the-fly deployment of crystalline graphite $S$($a,β,t$) sampling. Torchscript tracing and Numba just-in-time (JIT) compilation streamline neural inference on NVIDIA GPUs with CUDA libraries. Demonstrations of bare sphere thermalization of fast and thermal sources show excellent agreement between embedded NeTS in SERPENT and MCNP. With an explicit model of the reactor, NeTS can predict on-the-fly changes in TREAT neutron spectra as a function of local temperature, which can serve to improve transient and accident predictions in a multiphysics analysis framework. This framework can be further extended to account on-the-fly for changes in local graphitic microstructure to scattering cross sections, and outlines a novel coupling of modern machine learning with state-of-the-art reactor physics methods.
97 MATHEMATICS AND COMPUTING↗
Pyroelectric energy conversion with large energy and power density in relaxor ferroelectric thin films
The need for efficient energy utilization is driving research into ways to harvest ubiquitous waste heat. Here, we explore pyroelectric energy conversion from low-grade thermal sources that exploits strong field- and temperature-induced polarization susceptibilities in the relaxor ferroelectric 0.68Pb(Mg 1/3 Nb 2/3 )O 3 -0.32PbTiO 3 . Electric-field-driven enhancement of the pyroelectric response (as large as -550 μC m -2 K -1 ) and suppression of the dielectric response (by 72%) yield substantial figures of merit for pyroelectric energy conversion. Field- and temperature-dependent pyroelectric measurements highlight the role of polarization rotation and field-induced polarization in mediating these effects. Solid-state, thin-film devices that convert low-grade heat into electrical energy are demonstrated using pyroelectric Ericsson cycles, and optimized to yield maximum energy density, power density and efficiency of 1.06 J cm -3 , 526 W cm -3 and 19% of Carnot, respectively; the highest values reported to date and equivalent to the performance of a thermoelectric with an effective ZT ≈ 1.16 for a temperature change of 10 K. Our findings suggest that pyroelectric devices may be competitive with thermoelectric devices for low-grade thermal harvesting.
30 DIRECT ENERGY CONVERSION↗
Study of heat sources interacting in integrated circuits by laser mirage effect
This work exploits the mirage effect to analyze multiple heat sources thermally interacting in an integrated circuit (IC) by means of a probe IR laser beam, which strikes on the die lateral walls and passes through the die substrate. Under such conditions, the criteria for locating such hot spots, as well as their relative power dissipation, are discussed on the basis of a theoretical model inferred in this work. Finally, the technique feasibility is shown in a real application scenario, obtaining 5-μm spatial lateral resolution and an error in power dissipation measurements below 5%. This method may become a practical alternative to usual off-chip techniques for inspecting hot spots in ICs and to experimentally characterize heat flow in the semiconductor substrate.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗